1 HANDBOOK of METAL ETCHANTS Editors Perrin Walker William H. Tarn CRC Press Boca Raton Boston London New York Washington, D.C. © 1991 by CRC Press LLC

2 Library of Cataloging-in-Publication Data Congress handbook of etchants/editors, Perrin Walker, William H. CRC metal Tarn cm. p. and bibliographical index. references Includes ISBN 0-8493-3623-6 1. etc. I. Walker, Perrin. Etching reagents—Handbooks, manuals, William H. II. Tarn, TN690.7.C73 1991 617.7—dc20 90-15046 CIP highly information obtained from This and contains regarded sources. Reprinted material is book authentic with permission, and sources are indicated. A wide quoted of references are listed. Reasonable efforts variety have made to publish reliable data and information, but the author and the publisher cannot assume been for the validity of all materials or for responsibility consequences of their use. the in this nor Neither part may be reproduced or transmitted book any form or by any means, electronic or any mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without permission in writing from the publisher. prior for consent Press LLC does not extend to copying CRC general distribution, for promotion, for creating The of works, or for resale. Specific permission must be new in writing from CRC Press LLC for such obtained copying. N.W. all to CRC Press LLC, Direct inquiries Corporate Blvd., Boca Raton, Florida 33431. 2000 Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for and explanation, without intent to infringe. identification the Press Visit Web site at wwwxrcpress.com CRC 1991 by CRC Press LLC © No claim to original U.S. Government works International Standard Number 0-8493-3623-6 Book Library Congress Card Number 90-15046 of Printed in the United States of America 9 0 Printed on acid-free paper © 1991 by CRC Press LLC

3 PREFACE This is a collection of cleaning and etching solutions extracted from the open book literature from 1940 to the present. It began when the authors and co-workers technical about with the of germanium and silicon semiconductor devices as became involved development and, removal, defect development were needed and over cleaning, polishing solutions for expanded to include compound semiconductors, other the materials, and years, has device metallic used in the processing and compounds of devices in their metals or all assembly and physical forms ... the entire field of inorganic materials and their various shapes processing . . with, here in this single volume, all major metal elements, and chemical . High of currently involved in our compounds Technology fields. majority the metallic includes several solutions as originally formulated by the authors and co- The collection new as were being developed, many of which have been published or workers compounds the ourselves other workers in or chemical processing field. presented by the continual influx of new scientists, engineers and With into the Metals, technicians Solid Electronic or Silicate and Ceramic fields, there is always a "need-to-know" State, of chemical already developed. Even at that, old solutions appear in availability solutions years, as approximately every 10 to 15 development, mainly due to a literature "new" the time or the nonavailability of a technical lack for extensive literature search. This of library not castigate such "new" development, as it to includes a greater understanding of is often and material reactions utilizing advanced equipment capability that chemical not orig was inally available. the any books have been published over many years with regard to chemical In event, of materials, often on a particular metal or metallic group . . . but not all- processing selected inclusive . and more often involved with the material processing with but a short, . . list chemical solutions and limited discussion of their application. There are exceptions, of such as the ASTM E407-70 pamphlet — no longer in print — that has an extensive numbered list of developed for the *'metal" industries . . . mainly for irons, steels and formulations alloys. The Metals Digest published by Buehler Ltd. is another example, but copper A/B industries, is the so-called "heavy metal" with some natural minerals, too concerned this largely involved with the preparation of metallographic and for study ... not is specimens State Electronic material processing. The ASM and Handbook Series of some Solid Metals volumes probably presents one of the most extensive collections of data with regard to 12 processing the again — metal metal industries with etchant solutions for general material — and plating. processing specifically the technical journals Many are worldwide published for Solid of today and Electronics, but there is such a vast amount of literature available that it is all State but impossible any one individual to stay abreast of the new data and developments. The for may of varies by Journal and again presentation be more concerned with development format other than chemical processing — a newly developed compound often extensively studied for crystallographic with little or no mention of chemical solutions. structure understanding of is essential, yes, but any new material requires An crystallography solutions: development four types of chemical basically (i) cleaning; (ii) general eventual of (iii) polishing, and (iv) defect removal; etchants. Fortunately, the vast majority development of and metallic compounds form in the Isometric (Cubic) System, and metals brief intro a duction to Crystallography is presented in Appendix F. There are many excellent books on the market that discuss the crystal defect state in detail with regard to Solid State materials, but the field of mineralogy (geology particular natural 'hard-rock") much of the basic data on 4 minerals — Dana & Ford A established Textbook of Mineralogy — not only includes an extensive section on Crystallography, but crystal describes minerals — over 4000—their known structure, refractive index, specific all gravity, formula, pyrolitic data (including etchants), natural occurrence, and major industrial © 1991 by CRC Press LLC

4 use. Many grown compounds are found as natural minerals, several are included artificially grown. this they have been studied and/or where Sphalerite, ZnS, as one example in book, zinc sulfide — as its structure is basic to many compound semiconductors . . . Isometric — Tetrahedral System, Class. this be a book of cleaning and etching solutions, crystal structure cannot Though is directly as of chemical processing is much related to the crystal structure overemphasized, of the materials in both general study and device fabrication. A knowledge of bulk crystal plane directions, an example, is essential in the structuring of many specific microelec as devices. tronic objective of this book is to present The least one solution for all major metals and at metallic compounds in current use and/or under development for immediate, hands-on ap place" plication, be used as a "starting can for further specific solution development. and Hopefully, those who have an immediate need-to-know will find it of use. Pen-in Walker William H. Tarn Los Angeles, California 1990 © 1991 by CRC Press LLC

5 THE EDITORS Walker is retired after 30 years in the Solid State industry as a scientist Perrin currently and and 20 years military service. has engineer, over the B.A. a honors in Geology from degree University of Virginia, holds He with 1953 with work toward an M.S. degree at UCLA Charlottesville, 1954. He has Virginia, in a of Sigma Gamma Epsilon, the Electrochemical Society, and the N.R.A. been member his crystallography chemistry background, much of and work has been in With his & D on semiconductor and quartz crystal surface chemistry and R processing of chemical all Solid State materials. He also has been involved in processing parts and inorganic design, and phases of device design, testing and fabrication, to include sales. equipment all half been line engineer in charge of has a dozen government device development He the supervisor of operations, to include an MIC Laboratory, contracts, Manager of Quartz and Crystal & D. R Walker both patents in semiconductor processing, and has presented papers in Mr. holds involved semiconductor geology fields. He is still the with studies in both Solid State and and Geology, actively pursuing a career as a freelance writer (both technical and non technical), is published cartoonist, also with published sketches and drawings of macro- a micro-fossils in and geology. Tarn research recently retired after being employed for 45 years in the H. William is disciplines areas a panoply of disciplines. The of each required, at some and development in time, the chemical reaction of a surface point against an often obstinate and etchant uncooperative surface; hence his interest in chemical etches. metallic Tarn and during World War II under research Mr. development O.S.R.D. worked Mechanical and a patent for a "Resilient contracts Wheel' that required neither rubber holds nor etching. The Synthetic Liquid Fuel Program of the Department of the Interior and the infant semiconductor were later sites of surface chemistry activities that led to etch industry assault in and sensitization of metallic surfaces for use by intermediate or terminal preparation chemical agents. Mr. Tarn holds several patents and has been the co-author of several papers in these emphatically fields these subjects; he also states on that although he has accidentally and skin tested approximately 20% of the etches herein, there are no commercial cosmetic care applications for mixtures and advises great the be used in their application. © 1991 by CRC Press LLC

6 PUBLISHING STATEMENT and etching and general data presented are for information, and direct Cleaning solutions chemical processing those operators with a basic understanding of chemistry application in by materials. as solution discussion sections are of applied by the referenced and physics The the and those applications only. With reflects continual advance published author(s) articles, of chemicals, materials, and solvents it should be understood that results discussed in purity the period of time, locale, chemicals and chemicals involved, and that results are relative to is within limits of chemical reactions. Information known accurate and reliable vary the may best of our knowledge according to known applications to practices, but the authors the and no as to completeness or accuracy guarantee assume no liability in that regard. make and ON SAFETY NOTE of Many etching solutions discussed in this book represent a safety hazard, not only the the type involved, but their temperature, type reactions, methods of appli from chemicals so and forth. cations, can be dangerous due to reduced temperature, being inert, or explosive; Cryogenic liquids extremely are toxic; fluorine compounds are extremely dangerous as they attack cyanides all tissue, yet do not show an immediate "burn" reaction like most nerve chlorine gas acids; and are irritants on exposed skin, unbreathable, with attack of mucous membranes. silanes are immediate dangerous when being used hot; and the strong acids give Alkalies skin most burns. reaction acids and In as solutions, the end products of mixing should be known, salts to include reaction results from the material involved. Safety procedures are not specifically discussed in this book, but individuals should be sufficiently knowledgeable instructed prior to handling metals, chemicals, gases and and in this solutions regard. DISCLAIMER etchant patented or a part of are patents, which may include Specific solutions device as part of the disclosure, and other chemical processes or solutions can processing chemical classified Company Proprietary. There are a few as patented solutions — with patent be such — included in this etchant assembly but to the best of our number ... no knowledge company information. What may be classified as company proprietary, per se, proprietary — a given often already in the open literature is there are only certain chemicals for operation, mixtures applicable to a particular metal and metallic compound. This is particularly true or in area of clean/etch sequences and the sequences, the latter involved with multilayer etch or composite structures — several such sequences are shown in this text as they have appeared in the literature. There are cases of "new" etchants or chemical processes developed, open are the in the open literature — sometimes — for several years prior to which ' 'new" already and, instances, many development the same or closely similar solutions are developed in and simultaneously experimenters in generate laboratories different areas of the world, by such that it is sometimes difficult to determine priority of development. This disclaimer is not to there has been no attempt to release any information that already available in state the metals and metallic compounds processing areas. All information herein is as extracted from open literature, and is as originally written source by authors, from the the references cited. The Editors © 1991 by CRC Press LLC

7 TABLE OF CONTENTS Introduction Chapter Format Section 9 1: Material 9 Introduction Electrolytic 23 Format Etch Format 24 Dry Chemical Etching 26 Methods of Etching Index of Methods 29 Method Definitions 33 Etchants 70 Named Chapter 2: Section 75 Etchant 75 Adhesion ; 76 Air Aluminum 80 Aluminum Alloys 106 Antimonide 114 Aluminum Aluminum Arsenide 117 Nitride Aluminum 118 Oxide 121 Aluminum Phosphate 130 Aluminum Amalgam 131 Antimony 132 Argon 136 137 Arsenic Barium 141 142 Fluoride Barium 144 Titanate Barium 147 Barium Tungstate Beryllium 147 Alloys Beryllium 151 Beryllium 152 Oxide 155 Bismuth Alloys 159 Bismuth Bismuth 161 Germanate Bismuth Selenide 162 Bismuth Telluride 163 Bismuth Trioxide 165 166 Blisters 171 Bonding 177 Boron Carbide 179 Boron Borides 180 Boron Nitride 187 Boron 191 Phosphide Boron Telluride 192 Boron Trifluoride 193 Brass 194 Bromine 199 © 1991 by CRC Press LLC

8 Bronze 202 206 Cadmium 210 Cadmium Antimonide 211 Arsenide Cadmium Fluoride 211 Cadmium Cadmium Indium Selenide 213 Telluride 214 Cadmium Indium 214 Iodide Cadmium 215 Cadmium Oxide Cadmium Phosphide 216 Cadmium Selenide 217 Silicon Arsenide 222 Cadmium Sulfide Cadmium 222 Telluride 229 Cadmium Calcium 240 Calcium 242 Carbonate Calcium Fluoride 246 Molybdate 250 Calcium Nitride Calcium 250 Calcium 251 Tungstate 254 Californium 254 Carbides 255 Carbon Dioxide 261 Carbon Ceramics 262 Cerium 265 Cerium Dioxide 266 267 Cesium 268 Cesium Bromide 269 Chloride Cesium Cesium 270 Dioxide Cesium Iodide 271 272 Chlorine Hydrate Chlorine 272 284 Chromium Alloys 292 Chromium Chromium 292 Trioxide Cleaning, General 295 Cobalt 314 Cobalt Oxide 316 Sulfide Colbalt 318 Colemanite 318 319 Columbium 320 Copper Copper Alloys 341 Copper Bromide 346 Copper 346 Chloride Copper Iodide 347 Copper Oxide 348 Copper Phosphide 352 Copper Selenide 353 © 1991 by CRC Press LLC

9 Copper Sulfide 355 Disulfide 356 Copper 358 Phospho-Sulfide Copper Copper 359 Telluride Telluride Indium Copper 360 Corundum 361 Cronstedite 362 363 Cristobalite Deuterium 365 366 Diamond Dielectrics 371 372 Dysprosium Electride 374 and Epoxy 375 Polyimide Erbium 377 379 Etching Europium 384 386 Oxide Europium Ferric 387 Oxide Ferrite 387 Fluorapatite 390 Fluorine 391 401 Fresonite Gadolinium 402 403 Gallium Gallium Antimonide 406 Gallium Arsenide 413 Gallium Aluminum 487 Arsenide Nitride 488 Gallium 490 Gallium Oxide Gallium Phosphide 493 Gallium Selenide 500 501 Garnets 509 Germanium Alloys Germanium 581 Germanides 583 Germanium 587 Arsenide Germanium Nitride 589 Germanium Oxide 590 Germanium Selenide 592 Sulfide Germanium 593 Telluride 593 Germanium 594 Gold Gold Alloys 606 Graphite 612 Hafnium 615 Helium 617 Hematite 618 Holmium 619 Hydrides 621 Hydrocarbon 622 © 1991 by CRC Press LLC

10 Hydrogen 624 632 Ice Indium 641 644 Indium Alloys Antimonide 647 Indium Indium Gallium Antimonide 668 Indium Arsenide 669 675 Indium Oxide 678 Indium Phosphide Iodine 713 Indium 716 Iridium 718 Alloys Iron 719 Alloys 729 Iron Oxide Iron 736 Phosphide 738 Iron 738 Iron Sulfide Krypton 741 743 Lanthanum Lead 746 Alloys 751 Lead Lead Iodide 753 Molybdate Lead 754 Monoxide 755 Lead Lead 757 Nitrate Lead Selenide 758 Lead Sulfide 760 Lead Telluride 762 768 Lithium 771 Lithium Bromide 772 Chloride Lithium Lithium 773 Fluoride Lithium Nitride 776 Sulfide Lithium 779 Magnesium 780 Fluoride Magnesium 784 Nitride 785 Magnesium Magnesium 786 Oxide Magnesium Silicide 792 Magnesium Sulfide 793 Magnetite 794 796 Manganese Dioxide 797 Manganese Mercury 800 Mercuric Cadmium Telluride 803 Mercuric Iodine 806 Mercuric 808 Oxide Mercuric Selenide 808 Mercuric Telluride 810 Metals, General 811 Molybdenum 818 © 1991 by CRC Press LLC

11 Molybdates 829 Carbide 830 Molybdenum 831 Sulfide Molybdenum Oxide 833 Molybdic Mounting Materials 834 850 Muscovite Neodymium 854 Neon 855 856 Neptunium Nickel 857 Nickel Alloys 864 Nickel Iodide 872 Oxide 873 Nickel Sulfide Nickel 875 876 Nitrogen Niobium 879 884 Alloys Niobium Niobium 884 Carbide Niobium Nitride 886 Niobium 887 Oxide Nitrides 890 891 Osmium Oxygen 893 896 Palladium Palladium Alloys 898 Phosphorus 900 Phosphorus Pentoxide 907 908 Plastics Platinum 913 916 Alloys Platinum Platinum 917 Antimonide Platinum Arsenide 920 922 Plutonium Fluoride Polyvinidene 923 Alum Potash 924 Potassium 925 Potassium 927 Bromide Potassium Chloride 929 Potassium Iodide 933 Praseodymium 936 938 Quartz 947 Radium 948 Radon Earths 949 Rare Rhenium 950 Rhodium 953 Rubidium 955 Rubidium Bromide 956 Rubidium Iodide 956 Rubidium Sulfide 957 Ruthenium 958 © 1991 by CRC Press LLC

12 Samarium 961 Bromide 962 Samarium 963 Sapphire 968 Scandium Selenium 970 973 Silicides Silicon 986 Silicon Alloys 1091 Silicon Carbide 1092 Dioxide Silicon 1128 1134 Nitride Silicon Silver 1146 Silver Alloys 1155 Bromide 1160 Silver Chloride Silver 1161 Iodide 1164 Silver 1166 Siver Selenide Sulfide 1168 Silver 1170 Silver Telluride 1172 Sodium Sodium 1175 Bromide Sodium 1176 Chloride Nitrite 1185 Sodium 1186 Spinel Steel 1188 Strontium 1199 Strontium Chloride 1201 Strontium Fluoride 1202 Oxide 1203 Strontium 1204 Strontium Tungstate Sulfur 1205 1211 Talc Tantalum, 1212 Alloys Tantalum 1219 Tantalum 1220 Carbide Nitride , Tantalum 1222 Tantalum Oxide 1224 Tantalum Selenide 1226 Tantalum Sulfide 1226 Tellurium 1227 Dioxide Tellurium 1232 Terbium 1233 1234 Thallium Selenide 1236 Thallium Thorium 1237 Thorium Dioxide 1239 Thulium 1240 Tin 1241 Tin Dioxide 1247 Tin Selenide 1249 Tin Telluride 1249 © 1991 by CRC Press LLC

13 Titanium 1251 Alloys 1260 Titanium 1261 Carbide Titanium Dioxide Titanium 1263 Titanium 1268 Nitride Titanium:Tungsten 1270 Tungsten 1272 1283 Carbide Tungsten Tungsten Selenide 1285 Sulfide Tungsten 1286 1287 Trioxide Tungsten 1290 Uranium Uranium Carbide 1293 Dioxide 1295 Uranium Uranium , 1296 Nitride Uranium 1298 Disulfide 1300 Vanadium 1303 Vanadium Carbide 1305 Water Xenon 1323 Ytterbium 1324 Yttrium 1325 1328 Zinc Alloys Zinc 1338 1340 Zinc Arsenide Fluoride 1341 Zinc Zinc 1342 Oxide Zinc Phosphide 1345 Zinc Selenide 1346 Zinc Sulfide 1349 Telluride 1353 Zinc 1356 Zinc Tungstite 1357 Zirconium 1363 Zirconium Alloys 1364 Dioxide Zirconium Zirconium Nitride 1365 Zirconium 1367 Sulfide A: 1368 Appendix Crystallography B: Appendix Elements and Radicals 1370 Major Appendix C: Metals and Metallic Compounds with Reference Acronyms 1372 Appendix D: Indices 1389 Miller E: Natural Appendix 1391 Minerals Appendix F: Common Chemicals 1406 Appendix G: Hardness 1409 Used Appendix Common Acronyms and Abbreviations H: Throughout the Text 1411 © 1991 by CRC Press LLC

14 INTRODUCTION In development or fabrication of any metal or metallic compound, chemical pro the is involved one or more steps — from the study of a newly developed material cessing at a — product. This includes wet chemical etching (WCE) — liquid solutions; final to market copper (DCE) gases; a solid metal, such as ionized as a reactive etching — dry chemical at elevated temperature; molecular gases, agent; as in hydrogen firing; molten fluxes such solutions include the use of electric that Plating of metals or com electrolytic and current. a separate subject, not covered to any extent pounds this book, though chemical is in of and a few plating solutions are presented where they have particular preparation surfaces Solid processing. in application State factor in chemical processing involves the physical structure of the material on A major is many — in it instances, specific solutions have been developed for pro applied which crystal ... amorphous, crystalline, and single colloidal, structure. In addition, of cessing one solution can have a number of different applications: any removal, polishing, general preferential, selective . . . development of pinholes in an oxide thin film ... and structuring, alone can a solution from a slow cleaning system to polishing or preferential. temperature alter both the for solution reactivity control, but diluant alcohols and solvents is primary Water used as well as other acids are buffering agents. Other special additives, such similarly as surfactants chelating agents for foaming and de-foaming, glycerin or ethylene glycol as and viscosity control, and soaps for improved solution surface wetting, may be included in for solution a Gases may be bubbled through a solution: chlorine as an active agent formulation. alone, inert a stirring action only. Solvents for such as trichloroethylene, TCE, or nitrogen used in liquid form or as hot vapor degreasers; acids, such as HF are HC1, also are used or as or in hot vapor form. liquids chemical oxidation be Surface major concern in can processing as all metals and of many metallic compounds always have a passivating native oxide on their surfaces. Such oxides are surface contamination, as are oils, greases, dirt, or other organic considered they can a surface and produce erratic etching results. Further, if such residues, for mask form on that is subjected to some surface of heat treatment during remains a contamination can diffuse into the material and alter both physical and electrical parameters. processing, it other HF compounds are the primary oxide removers, but surfaces or fluorine-containing (boiling intentionally as a surface cleaning step be water, HNO3, H2O2); and may oxidized etching solutions can leave a trace oxide after many and are followed by a final HF use, strip. to say, oxides, nitrides, borides, and carbides are controllably grown on Needless against as element or as masks passivating etching, diffusion, metallization, surfaces final growth, and so forth, and may be an active element in a device construction. epitaxy The physical of a metal or compound are assembled to present factors that properties as be to chemical processing, such important melting points, chemical reactivity, crystal can structure and so forth. This includes their use as bulk material; thin or thick films; as a mixture, such alloys; and in multilayer construction, where each individual metal/com as will layer a specially designed solution that require attack that material but not pound may others in the assembly. There are several collective sections in Chapter 2 the solutions as containing fluorine, bromine, chromium, etc., with selected etchants formulas, chlorine, application by listed A to Z, brief material and format reference number. These can from be used for a quick summary of solution effect where a user is working with multilayer or composite systems. 1 all in some detail the etchant presentation used in Chapter 2 — Chapter discusses with: and and major compounds start gases, (1) Physical Properties; (2) General: elements associated natural minerals and general industrial use; (3) Technical Application: develop a ment studies, usage and devices, with emphasis on Solid State, and (4) Etching: and brief are mention applicable chemicals. Three formats of used in presenting each numbered © 1991 by CRC Press LLC

15 2 CRC of Metal EtcharUs Handbook in order assemble all pertinent information in an easily read manner for consistency solution to The of Chapter 1 is a discussion of the items listed in the Formats: bulk descriptions. of so Temperature, Discussion, Reference, and Composition, forth. Time, Type, Etch Name, an assigned number using the chemical formula All an acronym: AL-xxxx, etchants have or for Arsenide, etc. Some natural Gallium are included Aluminum; GAS-xxxx, for minerals particularly where they are of importance by regard to their artificial counterparts name, with like as a device. or, Alpha-Quartz, of — — is the alphabetical list Solution solutions, and includes some 2 Etchant Chapter are not strictly etchants, per se, but techniques forming or fabricating methods, that special as forming or the cutting and use sphere cylinders, bars, and oriented single crystal such of rhomboids, octahedrons, and so cubes, Many such forms are used in the study of forth. etch on concave and convex surfaces . . . the finite crystal form of a rates . . . bulk plane directions for controlled etching of channels, via holes, sphere establishing includes such oxidation rates on crystallographic planes using This forms. Gases etc. similar cryogenic in discussed — as gas or as some liquids — with their application in are detail processing, and includes their growth and study as single crystals. There is a chemical section on Materials, including some organics, such as waxes, resins, and lacquers (photo Mounting process etc., are involved in material they handling, mainly cleaning solutions. resists), as 80 of the major elements and gases — Over 600 metallic compounds, for a total over of 700 items with at least approximately cleaning or etching solution are presented. one Where there is a large number of solutions involved, such as under silicon (400+ ); gallium arsenide (300+) a "Selection Guide" is included: solution mixture, such as HF:HNO3 etc., H2SO4:H2O2:H2O, with — polish, preferential, etc. — and the assigned etchant or application shown. numbers are and each include the sections structure Format formula: a-Si:H, of Discussion material (SI), clean/etch sequences used, and GaAs:Cr, materials to which the solution (100) other applied. lower case letter following an The Number (AL-0027a) signifies another was Etchant was used on the material in the referenced solution The discussion is "as applied" article. by reference article; and it may vary with the period of development and use due to the the of or higher purity chemicals now available. improvement material objective of this book is to present hands-on applicable solutions The the open from literature all major metals and compounds in for single reference volume to reduce time a for an extensive literature search and it includes most of the current high technology materials. A number technical journals, both domestic and foreign; books; magazines; industrial of been brochures and technical conferences have pamphlets; used in the assembly technical and this book for the specific data. Much of the referencing done throughout uses the assigned of number solution developed in Chapter 2, as the Formats include the specific, say, journal/ as is volume most cases, the article title In not included, because only the number/page/year. type material and chemistry of concern is presented. Several of the tables, such as for compiled material the Physical Properties lists, are or from up to half a dozen hardness, sources, to include data developed by the authors, and do not reflect a pure abstract of any one source. The end-of-book Appendix H is a complete list of materials, their formulas, and Etchant Format letter acronyms used in Chapter 2. © 1991 by CRC Press LLC

16 JOURNAL REFERENCES* Journals (or publication): American U.S. (Acta Crystallogr) 1958: 1959: 1962 Acta Crystallographica — Me — (Ada 1955—1966 Ada Metallurgia tall) — 1955: 1958 J Abstr Metall Ceram Soc — 1959—1961: 1968: 1977 J Am Am Chem — 1941 J Soc — Mineral 1950 Am J Appl Phys — 1954—1985 Phys Lett J 1966: 1981—1984 Appl — — 1942 Aluminum Aluminum (Budapest) — 1955 J Chem — 1967 Appl Proc Eledropl Soc — 1956 Am Am Soc Mater — 1924 Proc Test Tech — 1956—1959 Systems Pub Bell Phys Soc Bull 1960 Am — Ind — 1963 Chem Chem Phys — J 1977: 1980 1940—1962: J Soc — 1929 Chem Cryst — 1979—1985 J Growth Crystallogr — 1984 J — 1970 Corrosion J Electrochem Abstr — 1961 Electrochem Acta — 1961 J Electrochem (JES) — 1955—1985 Soc Electrochem Tech 1964—1966 / — — Electron J 1956—1958 Control — 1957 J Electron Electron — 1983—1985 J Mater IBM J — 1961 1956—1957; 1966 IBMJResDev— Trans Electron Div — 1978 IEEE IEEE— Proc 1982 Ind Eng Chem (Ann) — 1948 Phys ConfSer Inst 1979 — Int J Appl Radiat Iso — 1961; 1969 IRE Trans Nucl Sci — 1960—1961; 1966 J Inst 1913; 1947/48; 1953; 1958/59 Met— Abstr 1958 Met — Prog — 1948; 1949; 1956; 1958 Met Rev— 1905; 1951 Met Met — j 1956 1953; Met Alloys— 1930 J Mater Sci— 1976 1962; Trans AIME — 1961; Soc 1967 Metall Met Finish— 1951 NASA Tech Briefs — 1985 * Singular or inclusive year dates. Standard abbreviations used. © 1991 by CRC Press LLC

17 4 CRC of Metal Etchants Handbook Res Rep 1959 Phillips — Rev Phillips 1961 — Tech 1960; Mag) 1960—1066 (Phil — Philosophical Magazine 1955—1969; 1984 Phys Rev — — 1958 Lett Rev Phys Chem Solids — 1940; 1956—1965; J Phys 1983—1985 — 1953 Plating 1950; — 1960 Soc 1958; Proc Phys Prog Semicon — 1965 Electr Proc — 1959 Inst Eng Am Electropl Soc — 1949 Proc Rev — RCA 1969^—1984 Rev Instrum — 1951—1969; 1980 Sci Prod Solid Technol — 1964 Semicond State J 1960 Tech — S.E.R.L. Electron — 1960—1972; Solid State 1982—1985 State Technol — 1973—1977 Solid Technol — 1958 Sylvania Thin Solid — 1976; 1982—1985 Films AIME 1944; 1956—1957 Trans — Electrochem Soc — 1942 Trans Vac Sci Res — 1984 J / Sci Technol — 1976—1985 Vac Foreign Journals Acta Phys — 1958 Pol Freq — Alta 1958 Appl — 1958; 1965/66 J Br Phys Fys — 1958 Cesk Cos Sci (Paris) — 1959 CR Acad Czech J Phys— 1958 1935 ComptVend— Akad Nauk SSSR — 1947; 195/59 Delk Met — 1957 Fiz Metalloved Fizverdogo Tela — 1959 Akad Nauk Izv Ser Fiz — 1957 SSSR J Phys Soc Jpn — 1956—1985 Jpn J Appl Phys — 1957; 1962/63; 1980—1985 Jerkontorets Ann — 1942 126 — Kristallografiya 1957—1959 Metalen — 1954 Corros — 1943 Met — 1957 Metallurgica (London) — 1958 Nature Kinzoku Gakkaishi — 1955 Nippon Phys Status Solidi — 1969—1972 Proc Soc — 1948 R Sov Microelectron — 1984 Sov Phys (Solid State) — 1959—1960 Sov Tech Phys — 1958 Phys Sov Phys Crystallogr — 1960 © 1991 by CRC Press LLC

18 / Phys Jpn — 1976—1985 Soc J Appl — 1957; 1962/63; 1980—1985 Jpn Phys ZAngewPhys— 1957 ZAnalikhum— 1948 ZavodLab— 1947 Anorg Chem — 1959 Allg Z ZPhys— 1938; 1954; 1957/58 CAem — 1942 /%s Z ZMetallkd— 1954—1961 Naturforsch — Z 1957—1959 F/z 1956/57 7eifcft ZA — Magazines Development, October 1966 Research & February 1962 Electric World, Solid State Technology, March 1983 Data Book, 1966 Kodak Chemical Engineering, 1962 March News, 1987—1988 Science Technology, 1984 Solid State May Scientific American, 1976 April 1981 Semiconductor International, 1985 Defense Electronics, Science, September 1985 Semiconductor Electronics, June 1967 Week, May Aviation 1957 Power, 1961 December & August 1984 Microwave RF, Iron Age, 1941 Pamphlets/Brochures 116B/Rev-HPD/VB/TM/O883/1K — Bull: Research Corp (MRC) Material ASTM E407-70 Metals Catalog 1035-AMD-CHG/ID/09997/30M SSS — (MRC) Bull: ADV 21M0M-11-59 — Crucible Steel Co. of Am., Pittsburgh, PA Bull: Photo and Materials — Scientific Gas Products Co. CA, 1972 Resists SM-102R — Applied Materials Tech., Inc., 1970 Pam: (Silox) OVB-4 1 l/i/64 — Corning Glass Works Bull: A-l-8 — Etch M-01-006" Bull: R & G Enterprises, CA, 1983 "Micro 1092 AMD/ID/JBA/5K/0482/GUILD/1982 — (MRC) Bull: "Platinum" — Pam: & Sons, Inc. (no date) Baker Pam: "Bright Gold" — Hanvia Chem & Mfg Co., Newark, NJ (no date) Pam: "Silvaloy" Engelhard Industries, Inc. (no date) — H681-10M Corp, "Metal Finishing Products" — Heatbath Bull: 1984 — Pfizer Sheets: 585; 593 — Chas. Data & Co., Inc. (1958/59) 557, Sales Catalog — VWR Bull: — Ashland Chemical Co 13332-1 Brochure: "AZ Series Positive Photo Resists for Semiconductors and Am Hoerchst Corp., 1983 Microelectronics", Bull: CD-101-5M-SC-282 — Stackpole Corp., 1982 © 1991 by CRC Press LLC

19 6 CRC of Metal Etchants Handbook B-11D — American Brass Co. (no date) Bull: The 406.6.71 Pam: Development Corp. (no date) — "Molybdenum" Schwartzkopf 1/1/83C Hycomp Inc. M Bull: 5 — D Council Bulletins — 1949 Tin R & — Digest Ltd, 1983 A/B Metals Buehler 395/1./71 Schwartzkopf Development Corp "Tungsten", Pam: — Alloys" — Magnesium Electron Inc., Farmington, Brochure:*'Magnesium (no date) and NJ "A of Carbide Terms" — Adams Carbide Corp., Kenilworth, NJ Pam: Dictionary M Nickel "The Platinum Metals", The Int W Co., Inc., 1954 Wise, — Reports & Meetings (15 Apr 66), Control Final (Si) Rep 65-0388f Labs Tech Rep Lincoln Soc Meet Electrochem WDC, 12—16 May 1957 — Electrochem Meet — Pittsburgh, PA, Oct 13, 1955 Soc Soc Meet Cleveland, OH, 30 September-^ October 1956 Electrochem — Met Dallas, TX, Spring 1967 Soc — Electrochem Soc Meet — Pittsburgh, Am March 15—17, 1956 Phys PA, Water Conf, Pittsburgh, PA, October 1961 Int Soc Mech Eng Meet — New York, Am November—December 1958 NY, Books of Dana, & Ford, W E — A Textbook S Mineralogy, 4th ed, John Wiley & Sons, 1. E New 1950 York, 2. S — Handbook of the Elements, Ruben, ed, Howard W Sams, Indianapolis, IN, 2nd 1967 3. Hodgman, CD — Handbook of Chemistry and Physics, 27th ed, Chemical Rubber Co., Cleveland, 1943 OH, Weast, R — Handbook of Chemistry and Physics, 65th ed, CRC Press, Boca Raton, 4. C 1985 FL, 5. and Materials, Alfa Catalog, 1983/84 Chemicals Research Corp., Refractory Materials Handbook, Coltronics & Brooklyn, NY, 1985 6. Ceramics Moss, T S — Photoconductivity of the Elements, Academic 7. New York, 1952 Press, 8. J C et al — Dislocations and Mechanical Properties of Crystals, John Wiley Fisher, Sons, York, 1957 & New Gatos, H C et al — The Surface 9. of Metals and Semiconductors, John Wiley Chemistry & Sons, New York, 1960 10. Lancaster, O — Electron Spin Response in Semiconductors, Plasma Press, New York, 1967 11. T J et al — The Defect Solid-State, Interscience, New York, 1957 Gray, Bennet, Barns E, Physics Without Mathematics, College Outline Series, 12. and Noble, C York, New 1951 Gatos, H C — Properties of Elemental 13. Compound Semiconductors, Vol 5, Inter and science, New York, 1960 14. Roe, J H — Properties of Chemistry, 7th ed, C V Mosby, St Louis, MO, 1950 Processes 15. A — Handbook of Materials and C for Electronics, McGraw-Hill, Harper, New York, 1970 16. Tegart W C McG — The Electrolytic & Chemical Etching of Metals in Research and Industry, Pergamon Press, London, 1956 © 1991 by CRC Press LLC

20 17. Scholler, R & Powell, A R — Analysis of Minerals and Ores of the Rare Earth W Chas Griffin, 1940 Elements, London, T 18. W H — Metallographer s Handbook of Etching, Pitman & & Berglund, Deardon, 1931 Sons, London, Thin & Glang, R — Handbook of Massel, Film Technology, McGraw-Hill, New 19. I L 1970 York, E & Jones, F D — Machinery's Handbook, 4th ed, The Industrial Press, 20. Oberg, New 1951 York, & L Properties of Glass Surfaces, John Wiley The Sons, New York, 1964 21. — Holland, W H — Handbook of 22. and Techniques for Vacuum Devices, Reinhold, Koll, Materials York, New 1967 I — Epoxy Skeist, Reinhold, New York, 1959 23. Resins, Simonds, H R et al — Handbook of Plastics, 2nd ed, Reinhold, New York, 1979 24. Schwentner, 25. et al — Rare Gas Solids, Vol 3, Academic Press, New York, 1970 N Ghandi, S — VLSI Fabrication Principles, John Wiley & Sons, New York, 1983 26. K Vol R & Beer, AC — Semiconductors & Metals, Willardson, 7, Academic Press, 27. K York, 1971 New Bondi, F J — Transistor Technology, Vol III, D Van Nostrand, New York, 1958 28. Bridgers, E 29. et al — Transistor Technology, Vol I, D Van Nostrand, New York, H 1958 30. J W — The Surface Chemistry of Metals and Semiconductors, John Wiley & Faust, New 1950 Sons, York, Coblenz, A & Owens, H L 31. Transistors — Theory and Applications, McGraw-Hill, — New York, 1955 32. Brechenridge, R C — Photoconductivity Conference, John Wiley & Sons, New York, 1956 33. J F — Physical Properties of Crystal, Oxford University Press, London, 1967 Nye, Read, W Jr — Dislocations in Crystals, McGraw-Hill, New York, 1953 34. T G Physics, & Brown, A P — Crystal Zhdanov, Academic Press, New York, 1965 35. S Academic R — Optical Properties of Semiconductors, S Press, New York, 1959 36. Moss, Lowenhein, FA — Modern Electroplating, 3rd ed, John Wiley & Sons, New York, 37. 1974 38. J — Tool Engineer's Handbook, McGraw-Hill, New York, 1949 Gordon, Wiley Thomas, Transmission Electron-Microscopy of Metals, John — & Sons, New 39. O 1962 York, ASM — Metals Handbook Series, Vol 40. 8th ed, 1974 2, 41. R C — Metallurgy of Elemental and Grubel, Semiconductors, Vol 12, Compound Interscience, New York, 1961 42. Holmes, P J — The Electrochemistry of Semiconductors, Academic Press, New York, 1962 43. J J & Johnston, W S — Dislocations in Crystals, John Wiley & Sons, New Gilman, 1956 York, Willis, R — Rare Metals Handbook, Reinhold, New York, 1954 44. and Etsenberg, 45. Kadsmann, W — The Structure D Properties of Water, Oxford & University Press, 1969 46. Hausmann, E et al — Physics, 2nd ed, D Van Nostrand, 1944 47. 1982 and Yearbook, Reader's Digest Association, Pleasantville, NY, 1982 Almanac 5th Jeans, 48. — Electricity and Magnetism, J ed, Cambridge University Press, England, H 1933 49. Winchell, AN — Elements of Optical Mineralogy — Part III: Determinative Tables, 2nd John Wiley & Sons, NY, 1951 ed, 50. Bunn, C W — Chemical Crystallography, Oxford University Press, London, 1946 © 1991 by CRC Press LLC

21 8 CRC of Metal Etchants Handbook Crystals, Bijvoet, et al —X-ray Analysis of M Interscience, New York, 1951 51. J Vossen, J L & Kern, W — Thin Film Processing, Academic Press, 52. York, 1978 New 53. W C & Gilman, J J — Dislocations and Johnston, Properties of Crystals, Mechanical John Wiley & Sons, New York, 1957 54. Phillips, A B — Transistor Engineering, McGraw-Hill, New York, 1962 55. Ducommun 1968 Catalog, New Kehl, L — Principles of Metallographic Laboratory 56. McGraw-Hill, G Practices, York, 1950 57. A/B Metal Digests 1976—1978, Buehler Ltd 58. Foster, W & Alyea, H N — An Introduction to General Chemistry, 3rd ed, Van Nostrand, York, 1947 New 59. Collie, M J — Etching Compositions and Processes, Noyes Data Corp., 1982 (patents) © 1991 by CRC Press LLC

22 Chapter 1 FORMAT SECTION MATERIAL INTRODUCTION cleaning solutions are those that have been developed for the processing The and etching crystal artificially crystals. Some natural single single minerals are of grown and study have been studied in conjunction with their included counterparts or where they artificial of crystallographic structure of materials as the class, such as sphalerite, representative are a wurtzite, ZnS for binary compounds; chalcopyrite, CuFeS2, for ternary and syl- ZnS and for 3Cu2S-V2S5 compounds iji addition to spinel, MgAl2O4; rutile, TiO2; vanite, quaternary ternary wolframite, others for binary and and oxides. There A12O3; (Fe,Mn)WO4 corundum, hundred or more such compounds that have been presented in the literature with regard are a not methods growth or in study of their crystallographic classification, but do of their to cleaning etching solutions and or thus, not included. include are, should be realized that there are over 4000 natural single crystal It that have minerals been and classified in the field of mineralogy, to include evaluation for pyrolytic studied solubility reactions. information is in book reference (I) A Textbook of Mineralogy and This Compounds" the ''Physical Constants of Inorganic on — book references in section and (4) The Handbook of Chemistry and Physics (3) by CRC Press, which lists and published and with brief notations as to compounds in water, acids, alkalies, elements solubility or some mixed acids, but no specific solution formulas alcohols, application data, and and do include many etch mixtures that have been developed in the metals and solid state not The is text also includes the name of the natural mineral where it technologies. latter to are chemical compound, and both texts referenced excellent references for general a information. solubility addition to single crystals, many elements In compounds are now being grown and and used in other crystallographically classified forms, such as colloidal, amorphous and crys talline. The are sometimes referred to as "polycrystalline" and may be as sub-micron, latter or macro-crystallites as a bi-crystal. All of these "forms" may be used separately micro-, or compounds/oxides/nitrides/metals, combination layers of metallic multiple etc. Such in as or included in this list of cleaning and etching solutions under their variations are primary crystal or compound and, in many cases, they require element formulation single special for controlled etching and processing. mixtures classification is the effect of solutions Another the material. This includes some of on the (i) general removal; (ii) polishing; (iii) preferential; (iv) stain; (v) decoration following: plating; metal develop defect structures; (vi) to (vii) selective, and others. as diffusion the solution is used for a physical action: (i) Where (ii) thinning; (iii) etch- step-etch; stop; pinhole; (v) via hole; (vi) channel, etc., (iv) material itself may be in a specific the form, such as a wafer, cylinder, bar, wire or as oriented cubes, octahedrons, tetrahedrons or rhomboids spheroids. It may be as a single crystal sphere, a bi-crystal or polycrystalline and reactions used to finite crystal form, oxidation etching of spheres are studied or sphere for are used to fabricate a device. Some metal they spheres are included where they are alloys of importance in fabrication or have been specific as a single crystal, such as brass. grown Special sections include borides, carbides, nitrides, and silicides and even a brief section assembly, on lucite, epoxies, and polyimides used in device — mainly for cleaning plastics or removal of such materials. In some instances, even though the basic etch format is used, there is no etchant shown of as is a growth or forming technique thought worthy of inclusion, such as the forming it studied spheres. as an example, is grown and Ice, using a cryostat microscope stage and © 1991 by CRC Press LLC

23 10 CRC of Metal Etchants Handbook is done varying cryotemperature, and ice spheres are made by spraying water "etching" by nitrogen, argon, oxygen. into liquid or compounds metals as substrates, which may or may not be involved Many are and used alumina, device. and dielectrics, such as Ceramics beryllia, quartz, final a with operating and and photo resist patterned in the fabrication of electronic circuits sapphire, are metallized powder, single crystal substrates — or fused or may be used as stand-offs pressed — parts in addition to their electronic applications. Semiconductors, such as gallium or heat sinks (GaAs) and phosphide (InP), are used as substrates for layered thin film arsenide indium heterostructure construction devices. Many single crystal compounds, or of heterojunction magnesium chloride potassium chlorides (KC1), and sodium oxide (MgO), as such (NaCl), for thin film metallization studies, with the films are then removed by the used deposited, technique study under a transmission electron microscope (TEM). The natural float-off for in one the micas, is used of a similar manner. mineral muscovite, the thin Where is an absorber and nonreflective for TEM study, graphite coatings film with gold films are used to fabricate replicas of the surface and can require special thin removal techniques, as for float-off. chemical such may single is being prepared for processing, it wafer be cut from an a crystal Where mechanically lapped and polished, and then cleaned and etched, or it may oriented ingot, used be or mechanically lapped, etc. In any case, cleaning and etching cleaved, as-cleaved sequences been for processing. Many such developed being assembled for sequences have device line processes are considered company proprietary, specific several also have but been in the open literature and are described in the discussion portion of etch published of Any sequence may consist of any clean/etch the following, alone, in formats. basic and not necessarily in the order shown: (i) chem/mech lap polish combination, remove to previous lap damage; (ii) degreasing; (iii) etching steps; (iv) solvent cutting/mechanical solvent steps a final (v) and or acid dip clean. cleaning There also is a degree of cross-referencing involved in the discussion section of etch formats where solution has been applied to more than one metal or compound in the the referenced. That etchant and reference will occur under each individual metal article same aqua with specific etchant number. For example: own, regia (3HC1:1HNO3) compound its or under gold (letter prefix: AU-xxxx); it also will appear will platinum (letter appear under PT-xxxx); both metals were under study in where article. This leads to a certain prefix: the of repetition, but each etchant has a distinctive number assigned which amount associated is with element or compound. There also is a degree of repitition involved with particular the The such bromine-methanol, BRM, mixtures. the concentration of bromine solutions, as from about 0.5 to 20% and, regardless of the general acronym BRM, each varies concen tration a specific solution as applied, and so listed. is appears the concentration, or etch mixture, Where in more than one author/article, same they too have an etch number assigned and immediately follow the primary etch format as an additional and may show another use of the solution. reference, applied also certain etchants where they are with for a different purpose. Repetition occurs acid (HF) is an example, as it may be used for (i) removal; (ii) pinholing; (iii) Hydrofluoric thinning, etc., that it will appear as a separately numbered etch solution in each such application case. a few only have been deposited A compounds thin film, some amorphous, others as as a single crystal, still others as polycrystalline films. Several are included whether an etch solution is not, because of the tremendous development, application and interest included or thin technology. in film are many aspects of cleaning There etching not mentioned in the above discussion, and but we believe the etchant formats are self-explanatory. The following sections describe the 2: methods present the materials of Chapter to Etchant Section. The introduction sections used to each element, metal or compound vary in length according to their light or heavy usage, © 1991 by CRC Press LLC

24 11 and three basic formats have been organized to present a consistent approach for pre the data. The items are described in some detail. senting format TO A. MATERIALS INTRODUCTION following: major compounds are introduced with the and (i) physical All elements of the description, (iii) technical application, and properties, etching, general. (ii) general (iv) properties The physical properties of the — or compound, and Physical (i) element properties where applicable. This may be extensive or brief depending upon some electronic of the found in the literature. Some new compounds show no physical availability information binary trinary compounds may follow their quaternary compounds with and or properties, list of physical properties. Crystal structure no shown by crystal system-class individual is to crystallographic notation. Cleavage (fracture) standard shown as many single according is compounds are being used as-cleaved, or cleaved crystal are used in both study sections and processing. General — as a natural single crystal mineral or element and associated (ii) Occurrence compounds; it a natural crystal, then artificial not general industrial use to If is minerals. applications such as in medicine, food include and so forth. The basic other preservation are and, where they are major discussed of etchants, they also appear gases constituents under applicable material in the etch formulation. Some natural single crystals are under the their name, such as magnetite, Fe3O4 and/or included under their chemical name, mineral as the sulfide, ZnS and sphalerite, ZnS, where such two compounds have been involved zinc in comparative studies. state Technical — Primarily as (iii) application material. If not a semiconductor, solid the compound application in semiconductor processing, or other use as a material or device in high This includes use as other than a single crystal structure, such as a technology. amorphous or form. It should be realized that both semiconductors and colloid, crystalline of well other metallic compounds are in use, as or in combination in all as metals, alone, possible forms. Other materials have physical in semiconductor processing, but their use in other applications, such as oxides or ceramics or as dielectric also as capacitors material or or their use as light frequency filters, lenses, lasers, and fiber optics. resistors, Etching As General solubility in acids, alkalies, alcohols, halogens. (iv) single or — acids; fluxes, gases; molten mixed and so forth. ionic the following Physical Properties list is Immediately General Section. The "General" the section is headed by the material name and is introduced by the name and formula of the material: example: CARBONATE, CaCO3 or CALOTTE, CaCO3 CALCIUM the (iv) section, the formatted etchant section is introduced with the etching Following example: CALCIUM CARBONATE ETCHANTS heading: following B. ETCHANT FORMATS three formats used have The designed for consistency of presentation in order to been include pertinent data in a concise, readable all repetitive form. As will be seen, all and information is not present for many of the etchants as it may not have been included in the say, reference many cases, it is easy to assume, In that a solution was used at room article. temperature — the normal application of that particular mixture — but unless it was so temperature stated the referenced article, the in (TEMP) is left blank. © 1991 by CRC Press LLC

25 12 CRC of Metal Etchants Handbook Wet (WCE) etching chemical I. format (1) Number Etch ETCH (2) NAME: TIME: (5) (3) TYPE: TEMP: (6) COMPOSITION: (4) RATE: (7) (formula) (8) DISCUSSION: (9) REF: format (EE) Electrolytic II. etching Etch (1) Number (5) TIME: NAME: ETCH (2) (6) TEMP: TYPE: (3) (10) ANODE: (4) COMPOSITION: (11) CATHODE: (12) POWER: (formula) DISCUSSION: (8) (7) RATE: (9) REF: chemical etching (DCE) format III. Dry Number Etch (1) (5) TIME: NAME: ETCH (2) TEMP: (6) (3) FLOW: GAS (13) TYPE: PRESSURE: (4) COMPOSITION: (14) (12) POWER: (formula) (7) RATE: DISCUSSION: (8) REF: (9) WDC format is used as the general format, such as for use of molecular gas as The DCE ionized Also includes molten flux etches, special forming and fabrication against gases. that may include a specific etchant. not techniques ITEM DESCRIPTION FORMAT C. ETCH NUMBER (1) referenced or has an assigned number under each element, metal Every com etchant and material; of three items: (1) capital letter designation of the pound, (2) an consists etchant number, individual lower case letter where more than one and appears for the (3) material in the referenced article. Up to four capital letters are used and are the chemical symbols for the material, element, compound, etc., it is a singular element or a binary compound. In some instances, where are "common acronyms, such as GAS for gallium arsenide, (GaAs) as GAS- these usage" YIG-xxxx. yttrium garnet, Y3Fe2O12, the acronym iron For trinary or quaternary xxxx. For where a chemical formula is in conflict, a special acronym compounds, used, such as for is molybdenum sulfide, MoSeS2 (acronym: MOSS-). And there is the special case selenium artificial carbon, diamond, of and a third for natural or C-; graphite, GR-, all three being D-; forms of carbon. All element or compound numbers start: -0000, e.g., AL-0001; then BE-0009; SI-0274; and so This leaves sufficient numbering space for any currently foreseeable new forth. solutions to they are added etchant the handbook. as the use the The case letter following of number is limited to those references lower where more than one solution has been used in the article on that particular element, under compound, full reference will appear The the "a" designated solution only; etc. whereas the "b", "c", etc. solutions will be shown as: REF: Ibid. © 1991 by CRC Press LLC

26 13 Example: ... REF: Doe, J — J Appl Phys, 57,112(1985) CD-0004a ... REF: CD-0004b Ibid. example A full format and additional reference is shown following the of complete a REF. of description (2) NAME ETCH a singular acid, alkali, salt, the If name is used, e.g., hydrochloric acid. It also it is full where the singular acid, is etc. is water diluted, e.g., hydrochloric acid, dilute. shown alkali, is shown if dilution is with other than water — alcohols, solvents, etc. It not are vast solutions show no name as they of mixtures. On the other hand, The majority a name is in common usage it is shown and may be a modification of an original where The an is formulation. example of one such solution: following NAME: Camp The original solution development ETCH #4 CP4 ETCH acronym Common NAME: usage CP4A without bromine NAME: ETCH CP4 CP4, modified CP4 with ETCH replaced by iodine, etc. NAME: bromine NAME: modified CP4 with CP4, different bromine content ETCH a similar case is the bromine-methanol (BRM) classification. The acronym is A in used the without regard to bromine concentration and no attempt has been made to literature these referenced as modifications. As in many instances the classify article only solutions . " . . says: BRM solution was used . . . ", which leaves a bit to be desired. a There are some poorly named solutions, such as the " 1:1:1", but it is still shown as an ETCH per article reference. The use of the name "White Etch" is another NAME: as it been used to describe HF:HNO3, and HF-HNO3:HAc solutions — none example, has are clear but transparent, which and colorless solutions. of white, the hydrofluoric solutions (BHF) are in buffered same variation category as The acid the BRM solutions — even HF, dilute has been called BHF, are KF has been used in or place NH4F, etc. A general standard in use is 1HF:1NH4F(4O%), though the reference of in show " . . . BHF may used. Unless it has been shown only the article, the BHF ..." formulation is not shown under COMPOSITION. (3) TYPE Divided into two parts: (1) a "chemical" designation and (2) an "application" desig nation. The of this two-part approach is to show how an acid or solution mixture objective used as more than one application is described in the various referenced articles. for possible Terms as brief and concise as are and the "chemical" descriptive term used may not necessarily agree with pure chemistry nomenclature, but all terms are chosen for general repetitive consistency. in of more commonly applied terms are shown Some the the two categories: below Chemical Application Acid Cleaning, polish Alkali Damage removal, polish, jet Alcohol preferential Dislocation, Gas Isotropic, oxide etch Halogen Anisotropic, oxide removal Ionic gas Junction, selective Metal Macro-etch, sphere © 1991 by CRC Press LLC

27 14 CRC of Metal Etchants Handbook Application Chemical Micro-etch, structure Molten flux stain Salt Mesa, Solvent step Orientation, Forming, Electrolytic thinning in categories. others are There both are chemically designated "electrolytic" and followed by an electrolytic All solutions even though common practice would say: "electropolish", application example; term as many the electrolytic solutions described have far more than just the polish whereas of application. are a plating handbook, but there not some plating solutions shown, primarily This is they have been used in developing p-n where as metal contact plating, or are of junctions, particular in Solid State or metal processing. use examples of designation are shown below: Three TYPE: polish TYPE: Acid, cleaning TYPE: Alkali, thinning TYPE: Electrolytic, (4) COMPOSITION into two parts: (1) volume/quantity used and (2) chemical formula of Divided constituents. In instances, the volume/quantity was not shown in the referenced article and is many obvious therefore an "x". Where it is as that the volume/quantity such as a designated single acid, alkali, etc. is not critical, it too is shown as ' V: x ... cone. or x ... HNO3 or x ... 2% Br2 HF, x...MeOH x...H2O example above is very common for third BRM and BHF solutions where the The the volume is not critical, provided the percent concentration of bromine, fluorides, etc. total maintained. is mixed solutions are shown by volume percentage. This is common to the metals Many industries and early solid state articles: some ... 6% HC104 35% ... butyl cellusolve 59% ... MeOH Where dry chemical compounds are used, such as ferric chloride, FeCl3 or potassium permanganate, KMNO4, are usually formulated as a water diluted solution, specifically they acids gram-weight as of water: g/1. Both liquid per or dry chemicals may be mixed by liter viscosity, using the Baume scale, °Be, which should not be confused with the temperature it scales e.g., °F or °C, although designation, is called "degrees Baume". Using "degree" ferric chloride as an example: 20% x FeCl3 (35°B6) or x ... ... FeCl3 or x ... x% FeCl3 © 1991 by CRC Press LLC

28 15 It may be shown as also g ... *or 50 g ... FeCl3 112 FeCl3 ... 10 ml ... H2O HC1 ml 1000 H2O ... 50 ml as a g/1 solution * solvents, etc. are usually measured and used by milliliter, ml, volume as Liquid acids, with commercially diluted concentrations shown as 70% HNO3; 30% H2O2; supplied water etc. HF 49% common method of designating The of a solution mixture, where most volume/quantity total volume is neither critical nor required, is the use a numerical ratio of constituents: to 1 HF or 3 ... HC1 or 1 ... Br2 ... MeOH ... ... HNO3 10 ... 1 5 HNO3 ... CH3COOH(HAc) 12 a mixed acid is used as a "constituent" in a particular formulation, it is shown Where as: 1 *CP4 ... ...HNO3 3 ... H2O 6 *CP4: 30HF:50HNO3:30HAc:0.6Br2 solutions may be shown Saturated two contexts: in 50 ml... HF or 100 ml ... HC1 20 ml ... NH4F, sat. sol. x ... *Br2 ♦saturate with bromine differentiate between an acid in concentrated form as against its use in vapor To using ("cone." shown when referenced.) form: only HF, ... or x ... HF, vapor x cone. a specific mixture When described, it is usually in milliliters, ml (liquid) or grams, is g still seen) for dry chemicals: (gm ... ml 30% 250 or 20 g ... KOH or 10 ml ... HF KOH 100 ml ... H2O 30 ml ... HNO3 100 ml ...HAc some terms the older literature, milliliters appear as centiliters, cc, but the two In of centimeters, are volumes are shown in cubic Some cm3, such as 150 cm3 HC1, equivalent. which is equivalent to 150 ml HC1. There are some large volume solutions measured in the gallons ounces, etc. The latter more often are in and metals and plating area, rather than Solid State. © 1991 by CRC Press LLC

29 16 CRC of Meted Etchants Handbook also may shown as a Normal or Molar solution: Solutions be or x... 1 ... 12WHC1 *EDTA2M x 1 ... ...NH4OHforpH3.5 UNHAc 1 l#K2Cr2O7 ... diamine disodium salt *Ethylene tetraacetic example, In EDTA solution is available as a standard molar mixture and, the second the case, a specific acid/base pH value is established using ammonium hydroxide. in this are solvents for liquid immersion or (hot) vapor: Cleaning used x TCE ... TCE, vapor or x ... TCE, spray ... or x or metal salts are Where for either developing p-n junctions by plating, or metals, used a defect decoration agent with in-diffusion: as g ... Cu(NO3)2 or 50 ... Au x 100 ... H2O ml ... intense + light developed, a clean/etch sequences that have been of many of them are number There are to a specific line operation, but several have been published in the company proprietary literature and follow a general pattern of any one or more of the following, and not open in the order shown below: necessarily BRM Chem/mech remove damage, such as to on a polishing cloth (1) lap Degrease in TCE, Freon, etc., as vapor, spray, or (2) (RT/hot) liquid (3) rinse with acetone, methyl or ethyl alcohol Alcohol (4) etch — a slow polish and/or cleaning solution Acid (5) Alkali etch — as an etch or surface conditioner (optional) (6) Water — DI, Hi-Q, etc., [also after (1) and (4)] rinse Alcohol rinse in (3)] (7) [as + rinse (often 50% HC1) HC1 (8) water + water rinse (50% HF common) (9) HF etc. Nitrogen — may be He, Ar, air, dry (RT/warm/hot) or IR lamps, other (10) blow or air dry heaters, As additional (11) process, final cleaning or drying in vacuum, in a furnace with hot an etc. gases, sequences are shown in the discussion section of formats where they may be These a major step. Some references may not operation any clean/etch steps, but only the include primary solutions associated with the material study even though one would normally prepare the surfaces using one or more of the clean/etch steps shown. by gas its gas mixture may be used as an etch in either A molecular or ionic form, alone. or liquid molecular also may be bubbled through a gas and act only as a carrying vehicle A for the liquid; for stirring action of the solution only; or be an active element in the solution their reaction. gases are shown by molecular normal diatomic representation; whereas The the ionic gases as in the example for argon, below. In some cases, the ionization (+) symbol © 1991 by CRC Press LLC

30 17 is present, but it will be apparent that ionic gases are applied, because the dry chemical not (DCE) format used. The last example shown below is of this type: etching it or N2 ... Cl2 or x ... Ar+ ion x x ... CF4 x ... or 5%O2 ... x vacuum, alone, is used for both preferential etching as well as for annealing, Heat in heat thermal A vacuum system may be back-filled to a partial pressure with e.g., treatment. oven when are used, it is usually as an but or furnace system. Oxygen or O2/N2 gas, gases CO2/N2 for oxidation; N2 or N2/Ar for nitridization; H2 or forming gas (FG) 85% N2/15% or H2 a reducing atmosphere, all along with heat. Where heat is the primary operator, it is as are as under composition; as shown below; but if molecular gases etch involved represented an addition to heat, the gas is shown: in ... heat or x ... N2, hot x are cases There where pressure, with or without heat, have been used to initiate special pressure under conditions defects temperature, or under vacuum using vapor various of change as the agent: x ... pressure or x ... vacuum Another special case is the use of light. It may be white light or referenced to a color and/or specific spectrum, used alone for drying; as a work light, such as etching frequency under red as a damage induction/reaction vehicle; in conjunction with plating; silver light; enhance to etching: or ...Cu(NO2)3 or x ... light 20 5 ... HF g or 2 ...HNO3 100ml...H2O ... *intense light 4- ... *light + lamp *Mercury (5890 A) yellow *Sodium the acid-slurries for lapping and etching, used acid, solvent carrier, and Where are are shown. abrasive only an abrasive where it is the only agent used for Occasionally, polishing the material: 50 g ... 0.5 |xm A12O3 or x ... diamond, powder 5 ml HNO3 ... ml ethylene glycol (EG) 50 ... systems are under the metal or other material used as the cutting Acid-saw (iron agent wire, thread, tantalum rod, etc.) and may cotton abrasives to improve slicing and include cutting action. Where two or more solutions are shown under COMPOSITION there are three methods as of the lettering or numbering systems using shown in the following three designation examples: (1) If two or more solutions are to be mixed together: (i)4...HF 10 g ... AgNO3 (ii) 3 ... HNO3 100 ml ... H2O © 1991 by CRC Press LLC

31 18 CRC of Metal Etchants Handbook 1 part parts (ii), when ready to use. mix: (i):3 two (2) solutions are to be used in order: or Where more HF 1 x ... MeOH (A) (B) (then) ... H2O 6 ... or more solutions are (3) be used separately: When two to ... HF (and/or) (2) 1 ... HF 1 (1) H2O 50 ... 1 ... H2O water used as the diluent or rinse it is shown as H2O, without regard to purity Where is should as considered but distilled water (DIH2O) unless otherwise specified: designation, be x HF x ... H2O, salt or ... ... H2O, tap x or' x...H2O are many types of water, but There two are normally used in all industrial processing, only as natural water with only solid matter removed, or as purified water, e.g., DI water. either latter most distilled on-site, and may be double-, even triple-distilled with The commonly as such Occasionally, it is known "Hi-Q". demineralized water (dm-H2O). Ref names as use is as fresh, potable (drinking) water, not saline, e.g., salt water, except as erenced . . . when used as a quenching medium or direct etchant, itself. noted water applied a neutral solvent, it is Although as an etching solution on water-soluble is Water and compounds. See the section on artificial for a more extensive discussion, minerals to include "cold etchants" as mixtures that may contain ice, or snow, or be cryogenic liquids. (5) TIME only when in the referenced article. Usually a single time and temperature; Appears given time two or two times at repetitive different temperatures, as separate occasionally steps forth. levels; times and temperatures and so etching The time can vary etching sequence seconds to minutes to hours depending upon the material and application. Some from are examples or 12 TIME: 10 sec, 3 times or TIME: 4 h or TIME: sec 2 min or 15 sec TIME: RT 80°C metallographic sectioning, etching In micro- or macro-structure, terms such as "dip" for or may be shown under TIME. These "swab" a method of applying a solution, but are were used as a time referent in the article. In defect and structure etching, final surface cleaning or device electrical parameters, an initial etch time may be shown and tuning by results. or more dip periods to obtain optimum followed This is particularly applicable one shown photo metallization patterning on circuit substrates and is to in the discussion resist section of the format. A time may be shown, and no temperature. In such cases, the solution was probably if used temperature but again, information is included only room it appears in the referenced at article. (6) TEMP Appears only when shown in the referenced article. In most cases, when a solution is the used other than room temperature at reference includes temperature. Fortunately, most © 1991 by CRC Press LLC

32 19 etching done at room temperature even though there may be an increase in temperature is the etching due to the exothermic nature of the solution or the heating effects during period RF plasma dry chemical etching. of an in any a affect have etching results with major given solution. The can Temperature on and NaOH, for example, when used at room temperature as 2—10% hydroxides, KOH solutions, for used liquid surface cleaning; as 20—50% liquid solutions concentration are heavy hot removers on many metals; and when used are to boiling are progressively they scale temperature used a molten flux at elevated as (360°C), they are also- preferential. When All liquid etch solutions become progressively more surface preferential and preferential. below even temperature, slow though they may be a polishing solution at room room and the is true. Much above 40°C, an exothermic solution becomes temperature, reverse in rapid polishing control. For this reason, good batch etching semiconductor wafers, too for large volume of solution is used — allowing it to cool between etch periods — or etching a done cycle-controlled a is etching bath using water, glycols or Freons chilling piping to in heat. dissipate three primary temperature are in common use: There scales Centigrade, °C Also called Celsius. Used in (1) works and as the atmos scientific pheric in Europe . . scale also now in the Americas. . (2) Fahrenheit, °F Widely used in the metals and plating industries and as the at mospheric scale the U.S., in addition to Centigrade. in Kelvin, (3) scale based on absolute zero. Absolute, °A, is equi K Scientific (°) that not use the degree does notation, al Note "K" valent. still does appear with the though sign in some publications. it degree between scales is as these Correspondence follows: Temperatures Table Comparative °F Reaction °C °Aor K Correspondence Boiling 212 100 + 6F 9 = 32 373 °C/5 x 50 323 20 293 Room temp 72 22.2 298 5/9; x 32) - (°F = °C Freezing 0 32 273 -40 -40 -200 73 Zero -273 0 formats, Under heading of the etchant the room temperature is shown as temperature RT whenever possible, even though "room temperature" has been shown in articles from 20 to It should be noted that many of the electrical measurements in the Physical 25°C. sections made at 20 or 25°C. Properties are terms also are used in describing a temperature, such as cool, Verbal hot, or warm, boiling. for following temperature levels have been The arbitrary use in this text for established consistency: as Cryogenic: -30°C — Liquified gases, such to LN2, LHe, LOX, etc. Normally -270 used to chill other liquids, though they can be a direct etchant under special conditions. level Freezing: 30 to 0°C — Certain acids or acid/ice-snow mixtures. Freezing - can produce a slush etch solution with cryogenic liquids for chilling. © 1991 by CRC Press LLC

33 20 CRC of Metal Etchants Handbook 0 to 10°C — Some acid mixtures, alone; others housed in a bath of ice water, Cold: + etc. acetone/ice, methanol/ice, 20°C — Acid mixtures chilled with cold water or other cold solvents, cryogenic Cool: to 10 liquids, etc. mmHg), — Standard atmosphere and pressure (760 or much etching done RT: 72°F 22.2°C temperature. room at to 40°C — Heat with light, gases or electricity (Note: "Chrome Etch" is widely Warm: RT a controlled 30°C). used at but to Varies with liquid and mixture, — below boiling point. Hot: 40 80°C Boiling: 80 to 100°C — Slow solution movement; fine, sporadic bubbles. Low boil: 100 boil: 130°C — Convection currents in solution; continual surface movement. Medium to solution; above 130°C Severe convection currents in — massive bubbles ex High boil: to surface; and violent, erratic plosive Some solutions, even above 130°C, show surface. a or rolling boil without severe, massive bubbling. roiling Most hot is done at low or medium boil. Note: etching or 100°C temperature dependent on solvent Specific gas used. above — Vapor: gas: to 1000°C or more; vacuum as low as Vacuum Ton*. +/- 10"10 RATE (7) article in unless it is referenced Not the formats as the majority of solutions listed in used without regard to are rates. removal In single crystal materials, such as the semiconductors, removal rates relative processing can the as well as bulk crystallographic planes surface be a critical factor of the to wafer design and structuring. Because of device whenever a new single crystal compound is this, developed, of the initial studies are much in establishing the etching of planar, involved concave, and convex surfaces. Convex surfaces are studied with spheres and hemispheres — the etch planes; concave surfaces — slow etch planes — are developed by controlled fast damaging and with pit shape and bulk planes controlled by the planar surface pit etching that pits (111) surface develops triangle type such and a (100), square pits. orientation, a solution both convex etching, the type etchant and used is an additional variable In concave hexagonal pits can be etched on (111) surfaces (superimposed negative and positive — one etch will tetrahedrons); a sphere to finite crystal form as a dodecahedron, (110); solution an as (100) and yet, another as cube, octahedron, (111) or tetrahexahedron, (hkO). another a of the above are in addition to defect study All dislocations, slip, stacking faults, twinning — — other structures. and general, rates single crystals Removal materials in on where only small amounts of and material are removed, are commonly measured in angstroms per unit time: 50 A/sec; 1200 A/min. In metals, ceramic, and glass industries — corrosion and similar studies — rate the may and a total volume gram-weight loss with time. The etch rate measurement include for metals, more chemically inert time such as tungsten, titanium, or molybdenum, some be have slow attack rates, may extremely only in mils-per-year (mpy). which Where material removal rates are more substantial, measurements are in millimicrons, .001"), m\i\ (xm; or in mils (1 mil = microns, with the time in seconds (sec), minutes in (min) or hours (h). Rate is always shown relative to time. Some examples are mils/h 10 20 fxm/min or 1.5 or or 4 |x/10 min A/sec The following table shows the correspondence of thickness measurements of some of the more widely used units: © 1991 by CRC Press LLC

34 21 Thickness Table Measurement Micro-inch Micron Inch Angstroms Mil ((*) (A) (mi!) (pl99) (") 1 254 1 10,000 .0001 100 0.1 25,400 2.5 254,000 1000 1 .001 25 is common for metal plating thickness, though The limited to micro-inch measure not 100 a relative standard, say, for copper, fx" or chromium; whereas gold with plating, nickel, \x" in most commercial applications, but supplied as 150 jul" or is jx" as gold 25—50 300 alumina in Solid State circuit processing. These thickness measurements plated substrates removal in processing, as the rate of material of a specific metal/ important all become a substrate is critical. Rate compound/multilayer thickness is experimentally established, on vs. for patterning of thin films in controlled circuit fabrication. In etching for initially, device and depth, an line-width solution will attack vertically and laterally at an equal rate, etch such initial rubilith pattern widths calculations must take the lateral etch factor into that to prevent undercutting, lifting, peeling of the thin film, or loss consideration subsequent are characteristics. such fabrication, rates electrical removal must be known, and In of of extremely critical factor in microwave device fabrication. an already said, removal rates are only shown in the etch formats when listed in the As articles referenced a major item, such as the initial study of a new compound. As a as function, of may appear in the discussion section secondary the format along with other it data. processing DISCUSSION (8) extensive from few words to Varies fairly a discussion depending upon the application. a Many of the earlier solutions that were, say, used for defect etching, plane attack data, etc. are brief; with more current development involving metallization, multiple layers, whereas etching, and forth, to include clean/etch sequences, the discussion is more selective so instances, the discussion starts with most material formula; single crystal extensive. In the amorphous; where other structure, such as or the physical specimen orientation applicable; such as a wafer, blank, etc. and the study or fabrication involved where appropriate used, with say, — a new refractive index, dielectric constant, or the test involved, and results, are forth. or special processing applications sequences included. Where the so Clean/etch article shows the study of other materials, these are referenced by chemical formula shown for purposes. cross-indexing Cleaning of general sections, Some as the (solutions/methods) may be a specific such solution application or a general discussion that can include other fields than metals/metallic compounds, such the use of borax ... a cleaner, a solder flux, a preservative ... in as in use, in medicine, and so forth. industry, home introductory sections — "Etching", as an example, describe the The etching basic methods . . wet chemical etching (WCE), . dry chemical etching (DCE), and molten flux or etching (MFE), or electrolytic etching, (EE) . . . without inclusion of a specific component clean or solution. etch used other the WCE etchant In is cases, for convenience, but involves a special format fabrication procedure, such as the fabrication of spheres by lathe cutting, melt forming, or using "race The latter starts by grinding. pre-cut single crystal cubes. track" (9) REFERENCES abbreviations Standard for presentation with accepted practice are used. Author(s) with © 1991 by CRC Press LLC

35 22 CRC of Metal Etchants Handbook name, first, initials — then the journal abbreviation (journal, volume number, last then year, year). the full title is given, followed by publisher, books, and page; For and page, with month/year/page. magazines and are more than two authors for the article, we have taken the liberty of Where there primary showing followed by "et al.". One horrendous example: a full page of the author Several and authors, page and a half of text! only foreign journals often list four to 52 a authors — again, first author shown only, for sake eight brevity, otherwise a drastic of increase total book volume which we feel is unwarranted, but no reflection against the in or status those other authors of die article! input of than have sections reference . . . less an 2% as unknown or unavailable Some open while others may be as "N/A" for common usage solutions, references, as aqua regia; such or the section' 'Mounting Materials'', and similar sections, where only a general discussion in is involved. here consolidation reference materials used are A of in Chapter 1 following this shown introduction, such as the Journal of Applied Physics with only year-inclusive dates. Specific articles are following each etchant format as part of the format: REF: xxxx and, referenced the other used the solution, they immediately follow have primary where authors/articles as an additional references. format referenced, the article title is not included in most cases, again, for brevity, and As the primary concern solutions are the because in this book; whereas the article chemical have and on another aspect of material developed may study with only minor description been of chemical processing. by example a primary One followed of an additional reference is reference, *REF: Belyustin, AW —SovPhys-Cryst. 5,143(1969) SI-0247: Richards, & Crocker, M — J Electrochem Soc, 121,14(1956) T L immediately the discussion section of the etchant format. This follows example of a complete Chapter 2 text An format and additional reference is etchant shown below: AL-0001 ETCH NAME: acid TIME: 1 min Hydrochloric TYPE: Acid, removal/clean TEMP: RT COMPOSITION: 1 HC1 ... ... 2 H2O DISCUSSION: as thin Al, . . . etc. films REF: Doe, J — J Apply Phys, 27,142(1976) 112,219(1977) AL-0007: J K — J Electrochem Soc, John, Al, (100) wafers . . . etc. © 1991 by CRC Press LLC

36 23 ELECTROLYTIC FORMAT a method etching, electrolytic etching is more widely used in the metal industries As of solid than electronics device fabrication. But if the iron industry says "electro- state in and say term polish'*, using the word polish as an application we polish" here, "electrolytic, a more or are such applications: cleaning, forming, thinning, oxidizing, dozen because there only a few. mention to preferential, (10) ANODE etching is used, the anode is Where to be the material involved — anodic understood arsenide, manganese, etc., but it is not listed unless actually stated in the gallium silicon, article. referenced In there may be more than one anode, or cathode and where a semiconductor special cases n-type is etched the specimen p- or being zone may be the anode. junction p-n "etch" solution, proper, may be either a true etchant The a plating solution — again, or primarily developing p-n junctions — such as using copper or silver to selectively plate- in the p- n-type side of a junction. It may include intense white light (copper) or be out or the understood (silver). It should be in that this book is not a Plating Handbook, dark operated junction presentation plating is with regard to of delineation, or material plating only the contact metallization of electronic devices. There are several for solutions as electrolytic anodic action formulas used, alone, or in conjunction with cathodic "etching". etching positive to operation the anode is the electrolytic ( + ) terminal. According standard CATHODE (11) there "cathodic occasional reference to Although etching", it is not etching in the is or of of material, but de-plating removal conversion of a surface. sense The cathode may be the same material as the anode in special cases, but it is more often a base such as lead, steel, stainless steel, iron, copper, nickel, or platinum that is, metal inert to etch solution involved and does not directly affect the anode material effectively, the Both such and cathodes may be in several forms, etched. as a bar, a single being anodes a wire etc. wire, mesh, the much work is progress in developmental anodic/cathodic oxidation of There in in particular, silicon in potassium hydroxide, KOH, solutions. It is surfaces, combination a of and de-oxidizing the surface by switching from anode-to-cathode. This operation oxidizing of included its importance in the study to metal and metallic compound surfaces. is due cathode material is shown only if it The given in the referenced article and includes is the rod, wire, screen or special form: when described in the article. shape, According to standard electrolytic operation the cathode is the negative (-) terminal. (12) POWER be shown is given in the referenced article; may it voltage or amperage only, Not unless both. preferably semiconductor materials are etched in Most milliampere (mA) range; whereas many the metals, and dielectrics such as glasses are ceramics in the ampere (A) range. In both etched cases, voltage (V) can range from tenths, say 0.2 V, to several volts — 5 V, 20 V, etc. Standard practice to show amperage per square centimeter, A/cm2 of surface area: 0.5 is occasionally mA/cm2 on. Most power is DC, so AC, or a combination of both. and Unfortunately, many references simply say "anodic etching** was used with no details a given, the article is not concerned with chemical processing of as material as a major factor in the study presented. © 1991 by CRC Press LLC

37 24 CRC of Metal Etchants Handbook CHEMICAL ETCH DRY FORMAT used Note: molecular form, such as H2 as a furnace reduction gas or N2 in Gases their inert chemical are shown under the wet as etch format, WFCE. Dry and At atmospheres, of (DCE), dry format (DF), applies to the use the gases in their ionic etching chemical using obtained using RF, RF magnetron, or form, power. Special applications may include as DC combination both RF and DC operation. a of FLOW (13) GAS cc/min, as SCFM: shown occasionally as Usually 0.5 SCFM cc/min 10 or or gas mixture is The by chemical/application under TYPE as TYPE: Ionized gas shown selective (and others) with the formula(s) under COMPOSITION: gas, ... Ar+ x or x ... CF4 ion x...O2(5%) the second that ionization is not shown as the dry chemical etching format In example, In used, the Ar+ (ionic symbol) is self-evident. rather than Ar only, which is addition, is of a gas. The additional descriptor molecular PRESSURE also is distinc of representative DCE processing, although RF or DC power application is tively both RF and DC power not; also used in sputter evaporation of metals, epitaxy growth of materials and plating. are PRESSURE (14) shown as milliTorr of over-pressure of the gas(es) when referenced to DCE Usually but can be shown in atmosphere, (atm): processing, mTorr 0.5 or 0.2 Pa (Pascal) or 0.4 atm (mT) Ion gas etching includes ion milling as an operating system, or RF plasma cleaning or etching systems. plasma cleaners using N2 or O2 as ionic gases are being widely used RF Solid State processing, and specific vacuum systems are designed to handle chloride in device cases, of oxide thin films with A1C13 etching BC13 as ionic gases. In all aluminum gas or systems with an input operate over- or back-pressure. the gas as an individual function/operation without regard to dry chemical Pressure etching (DCE) in the wet chemical etching (WCE) — classification, with pressure shown appears in or as pounds per square inch (psi). either atmospheres materials are pressurized in the study of Many high pressure crystallographic forms their and establish their transition temperatures. to hexagonal ice, for example, under Standard pressure, becomes cubic (isometric system, normal (cubic) class), and there are six high pressure forms silicon. of specific chemical CVD, material growth, deposition, pressure designated sys In vapor are used: low pressure, as LPCVD; high pressure, as HPCVD, and several others. tems and The artificial alpha-quartz is done at a minimum of 30,000 psi, of in geology growth studies of rock magma formation, better than 300,000 atm. Pressure alone is used as an "etchant" for preferentially developing defects in such rare materials alkaline halides (ionic crystals) or single crystal ice, gases (vary vapor as pressure in the vacuum system). In dry chemical etching (DCE) a number of methods and terms have been developed etching, with own acronyms. RF or DC plasma their PE, is the most general; reactive ion © 1991 by CRC Press LLC

38 25 etching, and several others. These may be shown in the format as an ETCH NAME, RIE, a TYPE: designator; or referred in the DISCUSSION section. Additional anodes as chemical plasma may used in conjunction with the RF cathodes or additional electric bias is and be to specimens. These are shown in an expanded applied — a combination of the format electrolytic dry chemical etching formats. and etching, reference the terms isotropic and anisotropic as used With wet chemical to in WCE, are polishing or preferential they respectively. Isotropic/polish are solutions etchants, that attack crystallographic planes at an equal rate in all crystal plane directions producing planar, flat whereas anisotropic/preferential solutions attack crystallographic planes surfaces; different producing structure. at rates dry chemical etching, the terms refer to structuring development without regard In to their or nonpreferential crystal plane attack preferential . . ionic gases can be either iso . tropic or anisotropic in character. From a pure chemical reaction point of view this variation difference of be confusing, because of this can in interpretation between wet or dry terms etching. In physics, geology, and optics the two terms were originally defined with regard crystallography, to propagation through solids, and are basic to light e.g., the refractive index of materials, etc. © 1991 by CRC Press LLC

39 26 CRC of Metal Etchants Handbook OF ETCHING METHODS been have terms used in the literature to describe a method of etching, over There 200 in into the three format categories described of the previous section: fall and one generally chemical and electrolytic etching. The use of a molten flux, here, is considered wet or dry is wet etching as the chemical flux is in liquid form, and also chemical used for a of form crystals, such as garnets and ferrites. single growing to the In and base definition using the Sorensen pH scale with water neutral addition acid pH acids with pH below 7; and bases (also called alkalies) above pH 7, there are many at 7; etching Water be considered an acid-like can solution; alcohols and categories. itself other usually considered as cleaning solvents, can act as solvents, etchant on certain though an molecular can be used in conjunction with gases or used alone, such as in materials; acids firing; vacuum as a "vapor" etchant on hydrogen materials; molecular gases can be certain used conjunction with acids or used alone, such as in hydrogen firing; vacuum and vapor in in vacuum been used as etching vehicles; thermal heat treatment, alone, or pressure have well is as a part of material fabrication as both as to etch. The halogens gases used with etchant category of their own, are the bromine-methyl alcohol (BRM) solutions in an with use. wide pressure, specialized include the use Some methods ice, cryogenic fluids, and highly of abrasives. The latter, for example, are used for even cleaning. Wire-saw cutting is surface another used in conjunction with an acid, with an abrasive slurry or acid-slurry. Many area under the or techniques are categorized methods wet chemical etching (WCE) of specialized the wet format (WF). using science use etching solutions is still The to as a magic art rather than a of by referred many particularly when it involves developing people, new solution as, though known a chemicals are used, results are often obtained by trial and error: varying solution constituents; varying constituent temperature variations; different methods of application. concentrations; factors include material being etched and its structure; chemical reactivity or Other the contamination involved. usage many solutions have become and standards, such as aqua With time industrial When it was first formulated in the regia Ages in Europe, the (3HC1:1HNO3). Middle of period thought it to be the the etch for all metals and metallic alchemists universal which, as we know today, is far from the case. It was the first solution developed compounds that would gold, and also will dissolve metals of the platinum group — platinum, etch to osmium. these metals etch slowly in comparison of gold in aqua regia, even indium, All used hot to boiling. It does etch a few other metals and compounds, can when either a be removal/polish or solution and, on still other metals, is a surface cleaning solution preferential heavy It is useful for removal of particularly metals contamination on surfaces, e.g., only. copper, iron, etc. The aqua regia solution varies in constituent concentrations, and may be diluted with or alcohols. water acid mixtures been developed for one material and a specific result, such as Other have light — #4 — developed as a Camp figure orientation etch for (100) oriented CP4 initially wafers, yet, even on germanium, it germanium be both a preferential or polishing can solution. original solution was 15 ml HF:30 ml HNO3:15 ml HAc:0.6 ml Br2. Since The semiconductor development has been used on several it materials and other metals and its compounds. Without bromine it is called CP4A, and is considered a better polishing etch for either or silicon than CP4. Further, as CP4-modified, the bromine has been germanium improve with Cu(NO2)3, Ag(NO2)3, etc. to I2, preferential action for a particular replaced type of defect. And depending upon the material involved, CP4 may be applied as a surface cleaning solution. (NO2)3C6H2OH:EOH, and — HNO3:EOH Nital Picral respectively, have long been and major solutions on iron, iron alloys and steels, both as polish and preferential etchants. The © 1991 by CRC Press LLC

40 27 acid are varied, the ethanol replaced by methanol, and both solutions are concentrations used on metals, such as the wide range of brass and bronze . . . both major now other since antiquity: (the Bronze Age) around 5000 B.C.; brass in use by copper alloys bronze circa B.C. possibly, 3000 the Egyptians, (lHF:2CrO3), developed in the early 1960s, has been a major The Sirtl etch preferential dislocation defect development, initially on silicon, and on many other for etchant now metallic compounds. Since its inception, a dozen other HF:CrO3-type solutions metals and for in defect enhancement developed general or for specific type defects. have been improved these interesting that like Sirtl etch, many of note solutions have been named after is It to Schimmel, Sopori, Wright, etc., to include variations and modifications their developers: their original These solutions are strictly preferential, as are many of the of formulations. been etches are several iodine etches that have there developed over the years, *'iodine" — called 'iodine etchant" although they are different formulas. all HF:HNO3, or The HF:HNO3:HAc solutions are the original oxidation- HF:HNO3:H2O etchants developed the Solid State semiconductor industry for general removal, reduction in on most preferential wafers, and are used on metal and metallic and polishing, attack diluted with either water or acetic acid (HAc), they act as surface compounds. Heavily or solutions. staining The mixture of HF:HNO3, high in either acid, cleaning, passivating surface solutions. as staining act a wide range of There with H2O2 replacing HNO3 as the oxidizing are mixtures the peroxide containing etches agent... . with similar uses to those containing HNO3. . . Another type preferential solution is Killing's etch (HF:KMnO4) developed in the oxidizer wafers and and used on semiconductor industry, and other metals. iron steel etch (1H2SO4:3H2O2) is primarily a surface cleaning solution on a wide range Caro's metals metallic of compounds, and there are many modifications of that base formula, and handled to dilution. These solutions should be water with care as they become self- include heating upon being activated and, once reaction is initiated, will reach a constant boiling level of 175°C. about acid, H2SO4, is a glass cleaner and conditioner, and has been long used Sulfuric alone, glass soda-lime for metallization as chrome plates masks for photolitho preparing in glass also is a general removal and polishing solution on many metals, particularly, as graphy. It etch the electrolytic metal industries. As a mixture of H2SO4:K2Cr2O7 it has long been an in it as cleaner" solution in many laboratories, and "glass is an extremely powerful known the oxidizer. two The alkalies, KOH and NaOH, have several applications depending upon major solution and/or temperature. A 2—10% mixture, at RT, is used for surface concentration, for At to about 40°C, warm), good (RT general removal. As 20—50% cleaning. 30—40% hot to boiling, they become increasingly preferential. As electrolytic solutions, solutions, are good for general removal, polishing, shaping, surface oxidation or selective struc they 360°C, As molten flux, liquified pellets at turing. they are highly preferential and used a for dislocation development in silicon and other single crystals. Other molten fluxes, such as carbonate nitrate mixtures are applied as cleaning or etch solutions in general metals and single Still are used in the growth of fluxes crystals, such as ferrites and processing. other and borax has already been mentioned as a flux for alloying. garnets, primary or The nitride remover is hydrofluoric acid, HF, applied as a concentrated oxide from or even alcohol or solvent diluted; used solution; RT to boiling; or as hot vapor. water, Because of HF's rapid attack of oxides, buffered hydrofluoric acid (BHF) mixtures have been developed better control removal rates. A fairly standard solution is 1HF:1NH4F(4O%), to as though other fluorine compounds used, such are KF and NaF, or NH4F.HF. there Concentrated, hot phosphoric acid, H3PO4, also is both an oxide and nitride removal rate solution it attacks silicon dioxide at a slower as than it does silicon nitride, it can and, be used as a stop-etch where the nitride is on top, and the reduced attack rate of the oxide © 1991 by CRC Press LLC

41 28 CRC of Metal Etchants Handbook "stops" the With the oxide over the nitride, the oxide will act an etch effectively reaction. photolithographic patterning the nitride. mask for of is concentrated, or diluted with alcohols, diluted, used (HC1) water Hydrochloric acid surface cleaner. As a hot vapor in epitaxy systems, as is the primary glass tube a general it susceptor method. In final rinse cleaning of semiconductor wafers, graphite and cleaning metallization, a two-step process is often used — dip in 50% HC1 and water say, prior to — then in 50% HF, and final water rinse, then N2 blow dry. rinse dip many (BRM) being widely used on are different metals bromine-methanol The solutions compounds as a chemical/mechanical (chem/mech) removal and polishing and metallic RT; general at polishing by immersion; or high concentrations of bromine as solution for Apiezon-W When wafer is patterned with a (black wax), BRM so preferential solutions. have been used for selective etching structure. Most polishing is done with solutions lutions less of 5% Br2, and preferential etching between 5—20% concentration. In conjunction than black wax solutions have been applied for thinning of specimens for trans with patterning, microscopy study. electron mission (TEM) be noted that any chemical polish solution can be used for thinning, but a It should solution produce will slow a flat, planar surface is preferred. For thick reasonably that reduction, a be used for initial thickness may followed by final thinning specimens, rapid etch a slower more controllable etchant such as BRM. Iodine can replace with bromine in the BRM with less evaporation loss, and similar results. solutions NH3 and hydroxide, NH4OH at standard liquid concentration are Ammonia, ammonium before widely neutralizes for acid waste sumps most disposal into sewer systems. the applied may be the sole They of an etch on alkaline halides or as an additive constituent constituent in etchant mixture. Both liquids can be used an neutralize acid burns on the skin, and to solid crystalline ammonia is the medical "smelling salts". Water, alone, a neutral solution (pH 7 on the Sorenson Scale), and the major quenching is following etching. is considered the universal solvent in chemistry and geology medium It material time, eventually dissolve all compounds. In will processing, it can act with it as, etching solution on water soluble compounds, such as as alkaline halides (NaCl, KC1, an the and, so applied, is referred to as an when under TYPE in the formats. Sea etc.) "acid" containing dissolved salts, either natural or artificially compounded, has been used water, an as for single crystal ice; as a quenching medium in metal processing; and even etchant the to crystal sodium chloride (salt), itself ... single primary saline compound used etch ocean water. in "Chrome Etch" solutions contain cerric ammonium nitrate or sulfate, with The or without amounts of HNO3, HC1, or H3PO4. They are commercially available as small pre- mixed and were developed specifically solutions, the controlled etching of chromium for thin films on glass masks in the fabrication of chrome photo masks for photolithographic processing. They commonly used at 30°C. The masks are made with iron oxide in place are solutions chromium today, for improved handling. The nickel, used on chrome are of or rapid with about 2000 A metallization, plus a quite A anti-reflective (AR) coating 400—600 and nitrate is preferred, as it has been the that the sulfate solutions may leave an shown unwanted film on the glass plate after etching. Note that these solutions also can be used on nickel. cleaning, alcohols are mainly used for surface solvents often as a final rinse Though and following quenching of an acid etch for their water absorbing qualities, they can act water as etchants on particular materials — in particular alkaline halide crystals. alphabetical The of etching are in methods order without regard to chemicals following and/or processes involved, and represent the wide variety of terms used throughout the industrial cleaning and etching of materials. © 1991 by CRC Press LLC

42 29 OF INDEX METHODS ETCHING 43. etch Control -A- etch Cool 44. etch Corrosion 45. etch clean Abrasive 1. etch 46. Coupon 2. Acid etch Cover 47. etch 3. Acid-slurry etch 48. Crucible etch Adhesion etch 4. Cryogenic etch 49. etch 5. Aged 50. Crystallographic etch etch 6. Agitation 51. Cup etch etch Alcohol 7. 52. etch Cutting etch 8. Alkali 53. Cyclic etch etch Alloy 9. etch 10. Air -D- etch 11. Angle Anisotropic etch 12. 54. removal etch Damage etch 13. Anodic etch Decoration 55. Argon etch 14. 56. etch Defect etch Atmospheric 15. etch 57. Definition 16. Atomizer etch 58. Degreasing etch etch Autoclave 17. etch 59. Descaling Dicing 60. etch -B- 61. Dip etch 62. etch Dislocation 18. etch Barrel etch 19. etch Base 63. Dissolutionment Drip 64. etch 20. Basic etch 65. Drop etch Basket etch 21. 22. Batch 66. (DCE) chemical Dry etch etch 67. Dry etch 23. etch Beaker etch 68. Dry ice 24. Blank etch 25. etch Boiling bead -E- 26. etch Bomb Bottle 27. etch 69. Electrolytic etch 28. Brine etch Brush Electron etch beam 70. 29. etch 30. etch Etch-back 71. Bulk etch sequences 72. Etch/clean 73. Etch-stop etch -C- 31. Cap etch -F- 32. Cascade etch Cathodic 33. etch 74. etch Failure etch Caustic 34. 75. etch Fatigue Centrifuge 35. etch Figure 76. etch etch Chem/mech 36. 77. Finish etch etch 37. Channel 78. Finite form etch Cleave etch 38. 79. Flame etch etch Cleaning 39. 80. Flash etch 40. Cold etch 81. Flat etch Conditioning etch 41. 82. Float-off etch 42. Contamination etch 83. Flood etch © 1991 by CRC Press LLC

43 30 of Metal Etchants Handbook CRC 84. Flush etch Light figure 118. etch etch Flux 85. 119. etch orientation figure Light etch Form 86. Lineation 120. etch etch 87. Forming 121. Liquid etch 88. etch Free 122. Long etch etch Freeze 89. etch Loose 123. 90. etch Fume 124. Low etch -G- -M- Gas 91. etch 125. etch Macro 92. Gate etch 126. Magnetic etch 93. General etch Matte 127. etch 94. Graphic etch Medium etch 128. etch 129. Melt-away 95. Gravity etch etch Melt-back 130. etch 96. Groove Mesa etch 131. -H- 132. etch Metal 133. Metallographic etch 97. Halogen etch etch 134. Metallurgical Heat 135. etch etch Micro 98. Heat-tint etch etch 99. 136. Milling Heavy 100. etch etch 137. Minimum Hot 101. etch Mist 138. etch etch 139. Molar -I- 140. etch flux Molten -N- etch Ice 102. 103. Immersion etch 104. Induced damage etch Named etch 141. Native etch oxide 142. Initial etch 105. Neutral (gas) Ion 106. etch etch 143. 144. etch 107. Nitride etch Irradiation 108. etch etch Isotropic 145. Normal -O- -J- etch 146. Oil Jar 109. etch etch Orientation 147. 110. Jet etch cleaning Oxide 148. etch etch 111. Junction etch 149. Oxide etch Oxide 150. removal -K- etch 151. Ozone etch Key 112. -P- 113. Krypton etch 152. Paniculate etch -L- Passivation etch 153. 114. etch etch Pattern 154. Laser etch Phase 155. Layer 115. etch 156. Photo resist etch Lift-off etch 116. 157. Pickling etch Light 117. etch © 1991 by CRC Press LLC

44 31 etch Pinhole 158. etch Slush 201. Pit etch 159. Snow etch 202. etch Planar 160. etch Soak 203. 161. etch Plane Solid etch 204. Plasma 162. etch Solution etch 205. Polar 163. etch etch 206. Solvent etch Polarity 164. etch 207. Spark Pole 165. etch 208. Sphere etch 166. etch Polish Spin 209. etch 167. Preferential etch 210. Sputter etch 168. Pre-plate etch 211. Squirt etch etch Pressure 169. 212. etch Stacking fault 170. Priming etch etch Stagnant 213. 171. Profile etch 214. Stain etch 172. Pylon etch etch 215. Standard 216. etch Steam 217. Step-etch -Q- Still 218. etch etch Quality 173. 219. Stir etch etch 174. Quantity stop) Stop-etch (etch 220. etch Strain 221. -R- Stress etch 222. 223. Strong etch Rapid 175. etch 224. Structure etch etch Raster 176. etch 225. Subtractive 177. etch Rate etch Swab 226. (ion) etch Reactive 178. 227. etch Swirl 179. REDOX etch etch Relief 180. -T- 181. Removal etch plasma 182. etch RF Temperature etch 228. 183. Rolling etch 229. etch Thermal 184. Rough etch etch Thimble 230. etch Thinning 231. -S- 232. etch Trim 233. Tumble etch etch Sand 185. etch Satin 186. -U- etch 187. Saturation etch 188. Saw (acid) 234. Ultrasonic etch etch Scale 189. Used 235. etch Seeded 190. etch 191. Segregate etch -V- 192. Selective etch 193. Sequence etch etch Vacuum 236. 194. Series etch 237. etch Vapor etch Shaping 195. degrease Vapor 238. etch Shim 196. 239. etch Via-hole etch Short 197. 240. Vibration etch etch 198. Sizing 199. Slosh etch etch Slow 200. © 1991 by CRC Press LLC

45 32 CRC of Metal Etchants Handbook -X- -W- Wash etch 247. 241. etch X-ray 242. Water etch 243. Weak etch -Y- 244. chemical etching (WCE) Wet 245. White etch 248. Yellow Room etch 246. Work damage etch © 1991 by CRC Press LLC

46 33 METHOD DEFINITIONS ABRASIVE CLEAN 1. wet or used as a method of cleaning material surfaces. Applied abrasive Dry powders powder other gas pressure; in a water slurry; acid-slurry; as sandpaper; or in dry as a under or disc resinoid as grease, cutting blade. Silicon carbide, SiC, is a major a medium, such processing, original manufacturing name "carborundum"; garnet general for compound the W-0 to W-16 series, graded by abrasive size/grit, with W-5 powder, grit or 16 as (600 a standard surface finish on materials. Surface machining shown in micro- fxm) general standard (250 1 |i") with 60 pi" a = finish. Abrasive hardness (Mohs scale ja", A inches, to 10); particle physical size and shape; of size in millimeters, microns, or inches 1 mesh shape blocky, round, slivers, etc., influence surface as and cleaning. — finish ACID ETCH 2. designation pH is the abbreviation The to describe the hydrogen-ion concentration used of solution. On the Sorensen Scale, pH values run from 0 to 14 and can be defined as pH a is a solution (water). Below pH 7, solution is acid, and the lower the value the 7 neutral the hydrogen-ion Above pH 7 the solution is basic, and the higher greater concentration. value, the greater the hydroxyl-ion concentration. the acids that are.widely used can be represented by sulfuric acid and nitric acid. Strong acids, be this can Weak confusing, may contain the OH hydroxyl radical, such as and solution acetic (HAc). Even water, the neutral CH3COOH at pH 7, is sometimes glacial acid, an "acid" where it is used as an called solution on material like the alkaline halides, etching such sodium chloride, NaCl or potassium as KBr and similar compounds and salts bromide, that are soluble in water. Almost all inorganic solids, whether they are an element, natural mineral or known grown material be etched in either a single acid or acid mixture, and the artificially can is — by concentration with dilution solubility usually by water — and material controlled solution temperature. by to many compounds require Semiconductors acids metal produce an oxidation- and mixed reaction — HF:HNO3 solutions as an example — where the nitric acid oxidizes reduction material and the hydrofluoric acid dissolves the oxide formed. Other acids, such as the material acid, sulfuric acid, H2SO4, convert the or to a water soluble hydrochloric HC1 or sulfide, respectively. And, as is the case of chloride iodine, I2, solutions, the many material forms water insoluble compounds that can be removed later as a sludge removed for material recovery, e.g., gold. Most acids are obtained and used in liquid form as a specific concentration in water: sulfuric acid, hydrogen peroxide, 30%, and so forth. Solution mixing and use for 95%; supplied is using the commercial concentration done as a physical volume etching mostly regardless of absolute acid concentration. An exception is quantity, titration of solutions in for of constituents, certain percentage evaluations of determination materials, and mixed similar chemical tests and studies. As wet chemical etching, acids and acid mixtures can be used in several physical ways: polishing, by spray, hot vapor, etc., as well as for specific results: cleaning, jet, immersion, surface defect development, or thinning, structuring, Such methods and/or techniques etc. form the bulk of this Methods of Etching section. electrolyte Acids used as a liquid are (electrolytic etching [EE]), including electric also current, and the specimen etched by immersion, jet spraying, with similar specific results as in wet chemical etching (WCE). © 1991 by CRC Press LLC

47 34 CRC of Metal Etchants Handbook ACID SLURRY 3. ETCH of A lapping where an acid is mixed with an abrasive. This mechanical form polish into amount damage introduced by the abrasive work the subsurface of material the reduces of or polished and can improve surface finish. The etch solution can be an acid being lapped base or a chemical mixture, such as SiC:H2O:Glycerin: 10%HF, or A12O3:H20:10%KOH. a as are a particular interest in polishing materials with slurries Mohs hardness greater Acid of for H such as glass or ceramic compounds 7, these materials tend to produce an than = smeared layer during normal abrasive lapping, and such layers show amorphous, different etching than that of the material bulk. This can affect subsequent processing characteristics a masking film (referred to as orange-peel), or initiate the introduction of pin- as surface an in etc. The acid action in oxide, acid-slurry will reduce such effects. holes an malleable and ductile metals, such as pure gold, lead, copper and silver, are not Soft, for recommended etching as they also tend to smear. acid-slurry ADHESION 4. ETCH of thin films to relieve stress and evaluate the film failure, as lifting, Etching peeling, crazing, Etching may include heat treatment to etc. or enhance failure. initiate 5. AGED ETCH Has two meanings: (1) any solution mixed and allowed to stand for a specified period of time, (2) any solution used more than one time may be called an aged or used solution. or regia is example of an etch requiring an aging time before use. See Stagnant Etch; Aqua an Etch. Used 6. ETCH AGITATION It used some form of solution movement. with can be movement of the Any physical of the part, or a combination of both, and solution, are various forms of movement: there 1. Solution hand Rotational a rod in solution, — or electrically operated (i) stirring Magnetic stirring — magnet in solution (ii) an exterior magnetic flux with (iii) motion using transducer Ultrasonic (iv) as on a shaker table Rocking, (v) Convection, as with boiling solutions (vi) Hand a form of rotational stirring swirling, As on a rotating part (vii) spray Gas bubbled through the solution as an agitation mechanism (viii) 2. Part Vertical (i) motion (ii) Horizontal motion Spinning motion (iii) Solution rotation, as in angle etching (iv) (v) Rocking motion, or various combinations of any of the above bubbles Solutions heavy evolution of gas produce are commonly agitated in some that manner to prevent bubbles from adhering to surfaces being etched to prevent the appearance of "footprints". 7. ALCOHOL ETCH Alcohols are normally considered cleaning or rinsing solutions rather than etchants, but they will attack certain alcohol soluble materials. © 1991 by CRC Press LLC

48 35 Three used alcohols are ethyl alcohol (ethanol) with the acronym of EOH; methyl widely (methanol or alcohol) with the acronym of MeOH; and isopropyl alcohol alcohol wood with acronyms either ISO or IP A. In addition, acetone (Ace acronym) (rubbing alcohol) of even because its here use as a cleaning solution in photolithography, of is included wide is a ketone, not an alcohol. it though are poisonous with the exception of ethanol (drinking alcohol) which is All alcohols as alcohol commercially with 5% MeOH or ethylene glycol added to supplied denatured but nonpotable. is 100% EOH (200 proof), alcohol most ethanol is 95% it Absolute make H2O (190 proof). Note that EOH. drinking alcohol is 80 proof (whiskeys, rum, 5% most gin, with proof-gallon as an vodka) 50% water content. brandy, initial addition to being used as a pure alcohol etch, many etching solutions contain alcohol In as a — Nital, HNO3:EOH, as an example. constituent ALKALI ETCH 8. are solutions pH 7, are the base or basic chemical solutions greater Alkaline than the the of pH as they contain scale hydroxyl-radical, (OH"). They to according Sorenson may liquid form, such as ammonium hydroxide, NH4OH or in solid form as potassium be in KOH, sodium hydroxide, NaOH. Where or hydroxide is used already hydroxide, ammonium liquid form, the in hydroxides must be dissolved in water for a specific percent solid concentration As a solution, they can be mixed as a Molar solution concentration, liquid. moles M liter of water and shown as, say, 1 e.g., KOH or 0.5 M NaOH (one mole of per of substance the total of the molecular weights is the elements in the compound that is any equivalent to one gram-molecular weight in one liter of water — (1/1 — or 1000 ml). A computation example is hydroxide, KOH Potassium 39.102 = (at K wt) (at 15.999 wt) O = wt) H= 1.008 (at g 56.109 Total that approximately 56 g of KOH in 1 liter This water is a 1 Molar (1 M) solution. says of is gram-mole of the substance. There are the available that show concentration as It tables percent solution, such as 10% KOH (109.2 g KOH), which is a equivalent to a 2 roughly M solution. by also shown as a Baum6, °B6, solution be specific gravity, such that 12.2 °Be It may equivalent to a 10% solution with a specific gravity of 1.0918, regardless is the chemical(s) of involved. the degree (°) sign is used with the Baume scale, but Note is not a temperature it scale like Centigrade, °C, or Fahrenheit, °F. The term * 'hydroxide" is often used in place of alkali or base, and all are equivalent, having the meaning. In the etchant section of Chapter 2 as the chemical descriptor same it shown as TYPE: Alkali, polish/removal/preferential, etc. word, is general, hydroxides are weak etches at room temperature and primarily used for In cleaning of 2 concentrations surface to about 15%; when used hot to boiling, usually in in etchants between to 50%, they are removal 20 and can be surface preferential concentrations — developing crystallographic structure. Alkalies also used as molten fluxes for preferential etching, such as on silicon; or are such growth for high temperature type single crystals, as as garnets and ferrites. fluxes 9. ALLOY ETCH Any solution used to clean an alloyed joint or structure, such as water for flux removal. etching The of an alloy material acting as the use agent, such as an AlSi(5%) alloy bead © 1991 by CRC Press LLC

49 36 CRC of Metal Etchants Handbook a pit a single crystal wafer, then etch removed for study of the convex pit side- forming in their crystallographic slopes and planes. 10. ETCH AIR Etch. Actual etching is due for oxygen, salt (chlorine), Alternate term Atmospheric to water contaminants in the air such sulfur, acids . . . smog. See Atmos moisture, or other pheric Etch. ETCH ANGLE 11. two meanings: (1) specimen: the part is lapped at a specified angle and then are There to develop diffusion depths; to Used p-n junctions, or epitaxy layer structure etched. measure alloys, semiconductor defects and structure in metal or or (2) containers: the etch in devices; is placed on a rotating spindle, say, container a 45° angle. Specimens are mounted on at discs or SST with Apiezon-W (black wax), placed face-up on the container bottom, of Teflon produce etching rotation speeds of between 130 to 300 rpm. The method used to at with done planar surface. Also used to wafer material for transmission electron extremely etch-thin (TEM) study, and to polish spheres, cylinders or other forms by slow rotation microscopy etching. during ANISOTROPIC ETCH 12. attacks term Etch. Any etch that Preferential crystallographic planes at Another for rates. Anisotropy and isotropy are terms related to different physical state of matter and the in are defined with regard to mineralogy propagation of light through solids. Recently, the the term has been applied in dry chemical etching (DCE) of selective structures whether the solution used a preferential/anisotropic or polish/isotropic solution. See Dry Chemical is Selective Etch; Etch. Etch; Preferential ETCH 13. ANODIC cleaning, the as the anode etching specimen removal, polishing, with Electrolytic for may structuring, switching from anode-to-cathode. See Electrolytic Etch; Cath and include Etch. ode 14. ARGON ETCH (1) Argon ion, Ar+, cleaning or etching of surfaces. Secondary: (2) The etching Primary: single of argon. crystal in Argon etching and cleaning of surfaces (Ar+) vacuum has become a widely (1) ion technique in processing immediately prior to used or epitaxy growth. RF metallization power vary from 50 to 500 KeV levels the electron energy can be sufficient to and cause subsurface damage. (2) Argon other gases have been grown as single crystals in vacuum under pressure and cryogenic etching Once grown, preferential and of the solid ingot has been conditions. system. accomplished vapor pressure in the varying Note that molecular argon is by used for parts drying or as an inert processing atmosphere, and may preferentially etch a specimen at high temperature. surface ATMOSPHERE 15. ETCH nominally 24% oxygen and Air, nitrogen with water vapor, contaminating gases 75% or other compounds will attack all known inorganic materials with time — hours, days, years millions of years, geologically. — In Solid State materials processing, atmospheric etching is not widely used although © 1991 by CRC Press LLC

50 37 Clean have controlled atmosphere, temperature, and humidity for optimum device Rooms control. quality industries, on the other hand, are vitally concerned with the atmospheric The metals metals, alloys materials with on-going studies in progress for development corrosion of and materials stability, corrosion resistance of all and to weathering — improved of reliability general term applied to effects of atmospheric etching reactions in geology. the most specific salt tests, such as are spray, gas absorption, and corrosion, There component standard that techniques in both Solid State and many other industries are that evaluation Air as active medium air carrying medium for other vapors. See an Etch; Gas Etch; use or Etch. Dry 16. ATOMIZER ETCH of an atomizer to apply a fine mist/spray to etch or clean a surface. Also used Use to fine-tune parameters on a semiconductor device with exposed junctions. A perfume electrical has been with a weak, polish acid mixture to etch, or pressure spray cans atomizer used or pressure solvents for cleaning acetone with nitrogen gas. containing other ETCH AUTOCLAVE 17. metal container capable of A high pressure. Called autoclaves, they closed handling long been used for steam cleaning of medical tools. have type autoclave application The can by process, material, or study involved, to include temperature and pressure levels: be pressure: cleaning of parts. 2—10 psi. Low General pressure: Artificial alpha-quartz crystal growth. 30,000—50,000 psi. Medium in High of single crystal metals and compounds Compression study of high density pressure: structures. 300,000—500,000 psi. Cryogenic: Artificial growth of single crystal ice at liquid nitrogen (-196°C), or liquid helium (-2 temperature. Etch by varying vapor pressure, say, of a vacuum K) 2—5 psi to 30,000 psi or more for high pressure crystallographic system. (ice); single temperatures). (cryogenic to elevated of forms crystals pressure of is oxidation done in low silicon autoclaves for both an oxide Steam being film or, with HF removal of the steam generated oxide, as a method of cleaning surfaces. thin 18. BARREL ETCH etching, barrel-like bottle for cleaning and or used closed and rotated A container on roller bars; open-topped and mounted on a rotating spindle similar to horizontally an angle beaker; or close-topped on a shaker table. etch abrasives, roller The using ceramic jars and bar has been a long standing way method, of polishing gem stones, and called tumbling. The same system is used for general cleaning of small with dry abrasives with the tumbler unit capable of handling from 2—5 lb of parts Machine parts and plating shops may use cement mixer-sized systems for material. shops See Etch; Angle Etch. cleaning. Bottle BASE ETCH 19. with used three ways: Term Any chemical solution in pH greater than pH 7 is a (1) chemical base, or basic solution as determined by the hydroxyl-radical concentration, OH" clean/etch radical. first etch solution used in a The sequence or the primary solution in (2) such a sequence. (3) A specific etch mixture with established characteristics against which mixture other are evaluated. This has included modification of the original solutions and comparison of reactivity changes. See Alkali Etch; Basic Etch. © 1991 by CRC Press LLC

51 38 CRC of Metal Etchants Handbook BASIC ETCH 20. with solution as established by the hydroxyl-ion concentration. The chemical pH Any >7 primary base an acid. Occasionally refers to a against solution in an a as compound is process. See Base Etch; Alkali Etch. etching sequence or 21. ~~~ BASKET ETCH wafers, dice or other parts in etching form of a basket holder that is The of some an etch solution; passed submerged an etch solution; held in hot vapor; or held in through spraying. latter two largely for cleaning, as in vapor degreasers. Basket design and for The upon high mixtures and/or temperature. Ceramic and platinum for depend material acid polyethylene, glass other plastics, or Teflon, for nonreactivity (glass not temperature; and and solutions). are many Teflon There polyethylene basket designs with fluorine-containing processing Solid State materials; for basket trays for vapor degreasers; wire mesh steel baskets, so forth. Teflon will handle temperatures to 200°C, but some plastics will melt and vapor degreasers temperature levels can range from 80°C (TCE) to about 120°C in where (PCE/Perk). Where etching is done, a basket CAUTION: mask the material surface causing can heavy against Stir solution and/or rotate the basket the the solution flow direction. erratic results. Agitation Etch: Rotation Etch; Stir Etch; Angle Etch; Batch See Etch. 22. ETCH BATCH specimens etching of any two or more wafers, cleaning or parts in a solution at The or time. A large glass or polyethylene beaker or one container with wafers, or parts similar held a basket immersed in the solution is in simplest form of batch etching. High volume the production systems may have two containers — one etch, one wash — a trough through which parts passed, or a centrifuge with immersion, spray etching, water quenching, are air or drying sequences. Such systems can be manual or automatic cycling, and nitrogen or from in a basket holder or fed wafers a cassette through a belt-spinner-belt to parts with wafers Cassette are designed for processing systems and dielectric sub loading. re-cassette circuits though photo resist applications; PCB boards though solder alloy furnaces. strate is Plating with multiple parts or hangers, and there is "free etching", where parts are done loose the etch solution. dropped in 23. BEAKER ETCH open-topped container used to hold an etch or cleaning Any Quartz, Pyrex, solution. polyethylene, Teflon beakers from 200 to or ml are common. Thick walled beakers 1000 (Pyrex) arc recommended for high temperature. Beakers arc widely used for individual wafer/part or batch processing of materials, to include plating. Teflon and polyethylene small beakers arc solutions contain fluorine compounds. Metal if of steel and platinum beakers used ceramic arc used in high temperature or and as thimbles, cups or crucibles for etching, molten etching or as single flux growth fluxes. crystal 24. BLANK ETCH Any etch solution used on a relatively small flat part, such as a 1 x 1 x .010" ceramic Heavily or Also called a flat or coupon. substrate. used in the metals industries for a metal wide variety of evaluation tests (coupons), or in alpha-quartz frequency crystal processing (blanks). Coupon Etch. See 25. BOILING BEAD ETCH Ceramic, glass, or metal beads of various sizes placed in the bottom of an etch beaker © 1991 by CRC Press LLC

52 39 to and control a bubble/agitation action of a hot to boiling solution. Bead material introduce be inert etch attack, and not contribute contamination. should against ETCH 26. BOMB or capable high pressure, and used to hold an etching holding A of metal container Autoclave Etch. See solution/gas. cleaning 27. ETCH BOTTLE a bottle for etching. Ink patterned closed taped silicon wafers have been as Use and this manner with solutions of HF:HNO3:HAc etched 500 ml polyethylene bottles. With in in etch and wafers loaded, the bottle cap attached, the bottle is then placed the solution a for the table on etch period. horizontally shaker crack. repeated the With will harden and use If the cap is not CAUTION: polyethylene tightened, it can come loose during etching. With insufficient acid or too many firmly excessive fumes and pressure are generated and the bottle can rupture explosively. wafers, with good table agitation wafers tend to overlap, stick together, and produce Even shaker results. Batch Etch; Barrel Etch. etching erratic See ETCH 28. BRINE solution. artificial or used as an etch salt Not common; some test evaluation Natural water metals and compounds in corrosion study. Quenching in brine solutions is used on in fabricating alloys and other metal mixtures to obtain specific structure and other physical steel The brine spray test might be considered as a type of characteristics. etch. In the metals salt tests. coupons exposed to seacoast salt environments in on-going corrosion industries are See Water Etch; Atmosphere Etch. 29. BRUSH ETCH The use of a brush to apply an etch solution to a material surface. It may be for light cleaning/etching, to etched structure, to fine-tune electrical parameters of a device, developed to produce particular surface finish. In the latter case, a wire brush may be used with or a Etch; electric applied, for a "brush" surface finish. See Swab without Matte or current Satin Etch. Etch; 30. BULK ETCH mechanical lap and polish of a material surface, the surface is etched to After remove the subsurface damage down to the undamaged bulk metal. Or use of a heavy etch residual general total removal, which may be measured by for gram-weight loss of a specimen. bulk solution. with to a Occasionally, volume of etching or cleaning regard See Rough large Etch; Removal Etch. 31. CAP ETCH ~~~ Special terms applied to Solid State processing and etching single crystals with thin films. (1) ion implantation of a semiconductor wafer when a CVD silicon dioxide or nitride After is "cap". deposited on the implanted surface, it is called a coating After an then with cycle stabilize annealing implanted element the cap is etch removed to solutions the of BHF, HF, or RF plasma (ionized gas). (2) In molecular beam epitaxy (MBE), the top thin film layer also is referred to as a cap, the as or oxide/nitride material layer. If epitaxy latter, a suitable fluorine containing an etch is used; whereas, if it is an epitaxy material layer, it may be a selective acid or ionized gas etch. © 1991 by CRC Press LLC

53 40 CRC of Metal Etchants Handbook Metallized thin are sometimes referred to as capping layers, such as when being (3) films by photolithographic pattern etched processing. of method capped crucible etching container may be referred to as a capped use (4) a The with in flux growth of single crystals molten subsequent etch removal as of etching, flux. See Cover Etch. from the CASCADE ETCH 32. final called commonly a method of more water quenching and Though etching, often an etch period, with reference to washing container structure used: a rectangular following the divided three or four progressively into sections, usually fabricated from trough lower sheet or similar high purity plastic. polyethylene available systems are about Commercially 6" each trough section about 8" long, and progressively more shallow. High purity wide, (18 MA) the top section, flowing downward through lower sections. To use a water enters in part be quenched and rinsed is placed the the lowest trough first, then moved cascade, to to the final top trough. Repeat rinse steps until the megohm upward remains at 18 meter Mft the upper rinse trough. in CATHODIC 33. ETCH etching is normally anodic, but switching from anode to cathode acts as a Electrolytic of and system, not an actual method removal etching. The term has been used deplating relative to studying the growth effects of hydrated oxides on metals, and in sputter etching with ionized See Sputter Etch; Dry Chemical Etch; Anodic Etch; Ion Etch. gases. CAUSTIC ETCH 34. Etch; or with a pH >7. See Alkali solution Hydroxide Etch; Base hydroxide An alkali Etch. ETCH 35. CENTRIFUGE cleaning. motion a part during etching or of A photo resist spinner has spinning Rapid used for acetone cleaning during photo resist application and been of semiconductor etching wafers the holder platen rotating at about 3500 rpm. There are automatic systems with to through etch and dry wafers designed automatic cycles with wafers handled from clean, cassettes. A system, including directional magnetic flux specialized produce a negative (-) or to positive (+) gravity effect during etching has been used to form pits and via-holes in brass and silicon and referred to as a centrifuge etching method. wafers, liquified systems to mixed glass-frits as a used slurry, which are then Centrifuge are onto surfaces and melt-fired spun 600—800°C). (nominal 36. ETCH CHEM/MECH widely etching being more Chemical/Mechanical more is used in single crystal wafer and processing to remove residual subsurface damage introduced by previous cutting, lapping, remove or The bromine:methyl alcohol (BRM) solutions are used to steps. damage polishing with a slow polish action. 37. CHANNEL ETCH The etching of a groove into a surface. Used in selective structuring of single crystal devices. channel Wafer dicing: Semiconductor wafers are (1) etched into individual dice shape and © 1991 by CRC Press LLC

54 41 then, demounting from the mounting substrate channels are oxidized or me without as a edge coating of the dice. tallized wrap-around channeling: (2) with oxide/photo resist with channel pattern etch Surfaces Wafer coated directions etching (100) oriented wafers. Dry chemical

55 42 CRC of Metal Etchants Handbook COUPON ETCH 46. a of as a flat form sheet material. Term common to metal flats specimen Etching cut corrosion the and other metal tests in atmospheric metal industries, but not used in studies, Etch. in processing. See Blank Etch; Wafer State widely used Solid ETCH ~~~~ COVER 47. specialized term where methyl alcohol is over a BRM mixture: MeOH/Br2:MeOH. As a part be etched is slowly lowered into the BRM solution, etched, then slowly withdrawn The to exposure pure "cover" to quench etching action without methanol to air. through the CRUCIBLE ETCH 48. use of graphite, ceramic, or high temperature metals, such as platinum, as a cup The hold to etching solution. Most commonly used in molten flux etching, such as defect an in silicon KOH pellets at about 360°C; or crystal growing from such development with by Etch. etch removal. See Cup followed fluxes, their ETCH CRYOGENIC 49. of cryogenic liquids as an etching The such as liquid chlorine, LC12 at use medium, 102°C. Also refers to the use - cryogenic liquid as a chilling agent for other acid solutions, of such liquid nitrogen, LN2. See Temperature Etch. as CRYSTALLOGRAPHIC 50. ETCH solution that will develop single crystal plane structure by preferential Any attack. Specific have been developed on solutions metals and metallic compounds during most evaluation development, and include etching spheres (convex), and pits (concave) surfaces. See Finite Etch; Dissolutionment Etch; Anisotropic Etch. Form CUP ETCH 51. container cup. used to hold an etching solution may be referred to as a Any open when Mo, small graphite, or high temperature metal (Pt, ceramic, Ti, Ta) used as a Usually a for either an etch solution or solid molten metal, and may include a crucible or cover. cap See Beaker Crucible Etch. Etch; CUTTING 52. ETCH use of an etch solution, alone, or a wire soaked in the etch to cut material. See The Etch; Acid-saw Etch. Acid-slurry CYCLIC 53. ETCH with sequential periods of time. Etching include water or alcohol quenching between May etch cycles, or the removal to air and return to etch without quenching. See Sequence Etch; Step Etch. DAMAGE REMOVAL 54. ETCH or solution to remove either etch surface used subsurface damage present or Any the by previous abrasive lapping, etc. It induced usually a slow polish type etch, such as is bromineimethanol both remove the damaged zone that polish simultaneously. See Chem/ and Mech Etch. 55. DECORATION ETCH alloyed The a metal thin film diffused or of into a single crystal surface to enhance use defect structure for observation. Other materials used are fluorescent dyes that may or may (liquid not biased electrically to develop color patterns be crystal, etc.); and, though not an © 1991 by CRC Press LLC

56 43 etch, or iron powders have been brushed on preferentially etched surfaces to enhance carbon observation. See Etch; Heat-tint Etch. defect Stain ETCH 56. DEFECT surface denoting development of any bulk or etch anomaly in a general the term A not it is single crystal, colloidal, amorphous or crystalline in structure. whether material or the etching study on materials is concerned with the recognition and elimination Much of wide of of defects, several of which have developed specific etching names as shown a range below. Dislocation Stacking Fault Etch See: Etch Slip Etch Polarity Crystallographic Etch Etch Etch Preferential Thermal Etch Anisotropic Etch Vacuum Etch Etch Lineation 57. DEFINITION ETCH used in two ways: (1) an Term used to develop a particular structure, such as fine- etch line and (2) a solution developed for a particular purpose — a definitive etch. definition, DEGREASING ETCH 58. rather solvent removal of oils or Usually for than etch solution, although an a greases, may be used. Laboratory glass is etch cleaned in a solution of H2SO4:K2Cr2O7, and etch glass photo used for chrome soda-lime resist masks are scrub cleaned with soap. plates DESCALING 59. ETCH etch used to remove heavy contamination from metal surfaces. Term widely used An development metal but not in Solid State processing, where most materials are supplied in as nominally clean parts. 60. DICING ETCH etch solution to cut and separate discrete devices or units from a semiconductor Any used type Channel in wafer or thin sheet form. See other Etch. or material ETCH DIP 61. or cleaning of a specimen for a The short period of time — the "time" is etching very to difficult but can be arbitrarily said to be between 1—3 sec. This form of etching define has used for (1) a final surface cleaning step; (2) to develop and optimize a defect been or structure; to fine-tune electrical or frequency parameters (3) a device, etc. It may be a of single "dip" or a series of such dips, depending on requirements. 62. DISLOCATION ETCH crystal preferential of structure in a single development material that can be The etch to crystallographically oriented defects associated related bulk structure or surface with defects. can be introduced during ingot Dislocations by heat treatment, alone, or growth; in conjunction with alloying, diffusion, epitaxy, cutting, and lapping; by controlled bending or or a surface in defect studies; of inadvertent damaging from process handling, striking etc. The study of dislocations in single crystals is probably one of the most important areas major of work in the Solid State field, because of the developmental effects defects produce on device parameters. See Defect Etch. © 1991 by CRC Press LLC

57 44 CRC of Metal Etchants Handbook DISSOLUTIONMENT ETCH 63. broadest the term dissolution or dissolutionment etch refers to any solution context In the a is In the study of single crystals, it dissolve used with specific reference that will material. with of to finite crystal form (FCF) spheres development of crystal facets the to etching convex surfaces. Also in determining the (planes) etching for characteristics of on general metals metallic compounds. all and ETCH DRIP 64. a single, or series of droplets on a surface. Usually applied to a limited area. apply To Pinhole specimens etched in this manner with DI water. See been Etch; Structure Iron have Selective Etch. Etch; DROP ETCH 65. has been used in three ways: (1) the free etching or cleaning of a part by physically Term dropping free into solution; (2) placing of a drop of solution on a surface to etch and/ the plate a p-n junction; develop pinholes in oxide/nitride thin films, etc., and or semiconductor of a distance, down through a column of solution with dropping time, and temperature (3) part sphere control e.g., the shot tower technique used in to forming. used fabrication, DRY CHEMICAL ETCH (DCE) 66. use of an ionized gas for cleaning The etching surfaces. Ar+ ion cleaning of single or crystal surfaces has become a standard technique in processing. Also used for selective wafer of be in device design. Gases used may etching inert, like argon; or they may be structure type reactive such as BC13. The latter species, called reactive ion etching (RIE). DCE is a one of the three major etch formats used to describe etching. 67. DRY ETCH considered a form of etching, yet drying can affect the surface or bulk of a Not true or removal surface can cause crazing, cracking a leave stains. Bulk Water from specimen. alter both chemical formula and crystal structure. Heat removal or annealing can treatment hydrogen are two methods. The latter a method firing surface cleaning in a reducing and of atmosphere. DRY ICE ETCH 68. CO2 Solid as a direct etching medium. Also used as a mixture with alcohols or used of for etch solution, or for removal another water vapor from process acetone chilling . . . drying the gas by chilling and freeze-out of gases water vapor as ice. the 69. ETCH (EE) ELECTROLYTIC etching use electric current The to any of or cleaning solution. Many such applied solutions are shown in the following section for different metals and metallic compounds using the etchant (EE) format for presentation of data. The specimen being etched electrolytic the and a metal (such as Cu, Pb, Fe) as the cathode. Additional anodes in cathodes anode and be be there can may anode-cathode switching, or the specimen separately elec included, are trically liquids and molecular gases Both used. biased. 70. ELECTRON BEAM ETCH E-beam or EB vacuum systems are used for metal evaporation from a rotatable copper beam hearth one to four crucibles. The from is magnetically bent up and around containing into the crucible, a 270° beam being a standard, today. The E-beam can be used to etch surface remove vaporize metals on a specimen and at controlled rates by varying power © 1991 by CRC Press LLC

58 45 input. used to anneal a specimen (heat treatment), in addition to being a method of Also evaporation. metal SEQUENCES 72. ETCH/CLEAN Sequences See under Clean/Etch Composition. 73. ETCH-STOP etch will attack one material but not another in a multilayer thin An film solution that than will remove Si3N4 much more rapidly etch SiO2, such that the H3PO4 structure. Hot work as an oxide mechanism. The method is used in structuring devices, and can etch-stop the and thinning of layers for TEM study. in removal ETCH FAILURE 74. use in the study of device Any and used to etch develop, surface stain solution failure, otherwise expose the causes of failure. or FATIGUE 75. ETCH solutions used on metals and their alloys in the study of material failure due Specific fatigue, such cracking from bending or crazing from atmospheric corrosion. This is a to as and test of study applied to metals method alloys with specimens prepared major evaluation metallographic techniques for observation after the test period. See Metallographic Etch. by FIGURE 76. ETCH form of defect or structure developed in a surface by etching, regardless of the Any etchant, Figures gas, liquid, solid. type also can be formed by temperature, pressure, e.g., called or As a pressure formed figure, flame. a "percussion figure" on mica, (0001) direct surfaces developing as a six-rayed star. Star line pattern representative of bulk prism plane directions and for orienting the micas. used FINISH ETCH 77. used etch a material surface. Term primarily on in the metals industries, The used final apply generally or to a specific and or technique developed to produce a particular can etch finish. Matte Etch; Satin Etch. See surface FORM ETCH FINITE 78. etching of Preferential crystal spheres of any metal or metallic compound to single produce solid with crystallographically oriented exterior planes that are the fast etching a (100); of convex surface. Planes developed planes with solution mixture, as cube, a vary octahedron, dodecahedron, (110); or tetrahexahedron, (111); as most common forms, (hkO) e.g., also called finite crystal form etching, and primarily applies to materials that form in the isometric system. See Dissolutionment Etch; Sphere Etch. (cubic) FLAME 79. ETCH of a propane torch or similar gas torch to produce etching action on a Use Has surface. been to develop surface etch figures used high melting point temperature metals and on alloys. Also used for surface cleaning of metals and their alloys during brazing operations. 80. ETCH FLASH Any very rapid etch applied for a short period of time. It can be a liquid solution or an analysis. electrical The latter used in spectrographic spark. See Dip Etch; Electric Spark Etch. © 1991 by CRC Press LLC

59 46 CRC of Metal Etchants Handbook FLAT ETCH 81. etch to to be planar and flat, or etching of a material sheet in die form a Either surface Blank Etch. Coupon See of a "flat". Etch; ETCH FLOAT-OFF 82. for film The from a surface removal microscope study by TEM, SEM, of thin layers solution attacks the substrate, but not the etc. Sodium chloride, NaCl, (100) Etch film. use H2O; silicon Si, wafers when used as a substrate in this manner, use substrates water, dissolve Mica, silicon substrate for film removal. to (0001), MgO, (111) and HF:HNO3 the such used substrates have their own etch mixtures, materials as HF for quartz and other as blanks. This is a separated and distinct method glass the float-off technique ... as ... against lift-off technique used for photo resist and excess metallization removal in device the (with acetone). fabrication ETCH 83. FLOOD cover a specimen surface with an etching or cleaning solution, usually with To rapidly than washing quenching acid reaction, rather or etching. An etching container to reference flooded with water to stop etch action. See Flush Etch. is FLUSH 84. ETCH cover a surface with a moving liquid etch solution. Used as a light surface cleaner, To to a an etch-washed pattern for or decorative effect. Also refers to water quenching produce See an by flushing to stop etch action. solution Flood Etch; Matte Etch; Satin Etch. etch 85. FLUX ETCH Use of a metal or solid chemical compound for etching. May also refer to the molten and of such as borax, in metal alloying and brazing, and solutions used to clean flux, use a residual after joint fabrication. See Molten borax Etch. remove Flux FORM ETCH 86. etching a material to a specific shape, or etching of a particular shape. Spheres Either etched crystal finite are form; rectangular bars are control-thinned as electronic reeds; to is are hole pattern etched as an inking mask; many metal shim stocks silicon electroformed via antenna, pattern as or masks; tantalum is etch formed as an etched etc. See evaporation Finite Form Etch; Sphere Etch. 87. FORMING ETCH Preferential, selective, or electrolytic etching of a specimen to a bulk shape, or structuring a surface etching pits, via holes, channels. Diamond is etched with a saw-tooth structure by a element. as filter 88. FREE ETCH etching of specimens by dropping them loose into The solution without being held in a any manner. See Bottle Etch. 89. FREEZE ETCH The use of a solution below 0°C to effect etching action, or, the quenching of a material bath from temperature into a liquid elevated solution. an 90. FUME ETCH Use of hot acid or solvent vapors for etching or cleaning action. Hot HC1/H2 vapors are of used epitaxy systems for general cleaning in quartz tubes, graphite susceptors and spec- © 1991 by CRC Press LLC

60 47 imens; HF vapors for oxide removal or hot water vapor (steam) for hydrated oxide hot conversion of surface followed by HF Strip as a surface cleaning step. See Vapor growth a Degreasing. Etch; Vapor 91. ETCH GAS molecular a to produce etching of in its gas form, such as argon, Ar; use The action nitrogen, N2, etc. It usually includes heat and/or pressure. Argon, as an hydrogen, H2; pressure in heat under a vacuum system has been shown to preferential etch example, and producing observed and pits similar to those surfaces with wet semiconductor hillocks ionic See etching. Dry Chemical Etch (both as Ion gases, not molecular). chemical Etch; GATE ETCH 92. term denoting channel etching for the active area of a Schottky Barrier Specialized such transistor a field effect device, (FET). The channels are either wet chemically etched as electron photolithographically on the submicron width scale. An active gate metal, or etched or channel, is then pattern evaporated in the aluminum and may be followed either gold (aluminum RF etch forming with ionized gases final with BC13). with plasma GENERAL ETCH 93. etch solution can be so called when used without Any specific definition, such as other a removal etch; and there is an etch solution with the name General Etch. general GRAPHIC 94. ETCH repetitive pattern of figures etched onto a surface. Such patterns can be A controllably produced decorative effects or developed in for — meteorites have a distinctive etched nature structure called Widmanstatten Figures that appear much like a grossly twinned single crystal ingot; also Neumann Line structure associated with twin lamellae — several of the quartz- the granites show fine graphic structure of a clear quartz network enclosing the softer feldspar a white Satin See Matte Etch; or Etch. pink feldspar. ETCH GRAVITY 95. specialized method of etching where A specimen is subjected to either a highly the ( + ) or negative (-) gravitational force by centrifugal action during preferential positive to controlled etching structures. Brass and gallium arsenide have been via hole and pit form in column manner. A specimen may be dropped down through an etch solution patterned this a or distance for forming for cleaning. controlled GROOVE 96. ETCH single crystal wafer structuring of devices, In etching of a channel in surfaces. It the may be as a "V" groove, have a bottom curvature of known radius; as a saw-tooth series of ridges; vertical side walls with a flat bottom, and side walls may be specific crystal have planes. 97. ETCH HALOGEN to a chemical class of elements as etching agents: fluorine, chlorine, bromine, Refers is iodine. Solid State processing, the term In most often applied to the bromine:methyl and alcohol (BRM) solutions. Chlorine, as a gas, is bubbled through other etch solutions for used added hot HC1 or HF vapors are action; as etchants; and iodine can replace etching bromine in the BRM solutions, and is used in several designated/named "iodine" etches. are Low bromine BRM solutions are polish etchants, hot vapors concentration primarily cleaning agents, and the iodine solutions are mainly preferential. © 1991 by CRC Press LLC

61 48 CRC of Metal Etchants Handbook HEAT ETCH 98. of use to effect an etching or cleaning action. Used under vacuum heat The only, a specimen in air to oxidize Used specimen surface. clean surfaces. conditions to flash heating of a liquid or Occasionally for etching action. See Thermal Etch; referenced as gas Hot Etch. Etch; Heat-tint 99. HEAT-TINT ETCH ~~ specimen on Heating hot plate in air to produce oxide colors. Used in the study of a a metallographic A crystalline material varies in color by rate of oxidation of of specimens. grains crystallographic to their crystallite plane orientation. A single individual according phase or can be differentiated by material structure or internal crystallographic crystal alloy directions by similar color variation. plane an alloy mixture or similar specimen, different In metal compounds can be determined by their characteristic oxide color when heat tinted or a specific Single crystal spheres of metals and compounds have been widely studied for time. kinetics controlled in the study of oxidation oxidation and growth rates related by furnace internal crystal plane location and orientation. See Heat Etch; Thermal Etch. to HEAVY 100. ETCH etch solution used to remove a large volume of material. Measurement is done by Any of gram-weight removal, or by total specimen mils loss. See Rough Etch; Removal surface Etch. 101. ETCH HOT room solution for etching or Any above used temperature as either a liquid or cleaning gas, and may be shown in °F, °C, or K. Also shown as warm, hot, or boiling. See Temperature Etch. 102. ETCH ICE ice has used as an etching medium in the sense of the freeze-out of a hot, Solid been alcohol metal the ice surface. Mixed with water or on it is used to cool other liquid poured solutions and, along with snow, has been used as a constituent in formulating a series etch of "cold for specific temperature levels. Also can refer to the etching of single etches" ice section, grown under cryogenic conditions in cold cryostats. See Water crystal specimens 2 Cold Etchants. Chapter for IMMERSION ETCH 103. solution, submersion a specimen Complete a liquid etch of or in a molten flux solid in chemical solute. It is the most common form of etching as wet chemical etching (WCE) or electrolytic etching which are two of the Etchant Formats used in the next section. (EE), chemical etching is the third format.) (DCE) (Dry DAMAGE ETCH INDUCED 104. etching to develop defects or structure in a surface Preferential has been subjected that to form of damage. Such damage may be some controlled scratch or a point of damage a introduce by a diamond-type stylus to develop specific defects, or to initiate the etch forming been of via hole, channel, etc. Also has pit, used with reference to residual subsurface a damage remaining after cutting or mechanical lap and polish. Such damage being removed Solid by polishing or straight chemical etching in chem/mech State device fabrication. See Defect Etch. © 1991 by CRC Press LLC

62 49 105. ETCH INITIAL solution that the first in a series, or the first etch applied in a specific material Any is process. ION ETCH 106. its RF rather than molecular state used to clean or etch a surface. A gas ionized in Solid O+ systems are widely used in cleaning State material processing. or plasma N+ ionic Ar+, also is widely used in Solid State processing to final clean surfaces Argon, as immediately prior to metallization and compound growth or deposition, and under vacuum helium subsurface ionic gases, such as Other (He+), xenon (Xe+), introduce damage. can used in material irradiation damage and thin etc., adhesion studies. Electron irra are film from TEM microscope or an electron-beam a vacuum system; lasers, for annealing diation in alternating materials; and nuclear or have all been used as forms of ion etching. particles See Etch; Dry Chemical Etch; Irradiation Etch; Particle Etch. Argon IRRADIATION ETCH 107. action. of or radiation particles to affect etching gases May also be used The ionized use damage into surfaces in the broader to of irradiation effects. Note that a single induce study when will revert toward the irradiated, amorphous state, and the crystal, noncrystalline, — an amorphous material will tend reverse single crystal or the crystalline state. toward Such of the immediate subsurface of Solid State materials is of major consid alternations in junction structuring, particularly, when an active diffused eration is in the <1 fim device electronic region, altered zones can severely affect the such functions of devices. as 108. ISOTROPIC ETCH Another name for a polish etch solution. The etch attacks all crystal planes at an equal rate, producing flat, planar surface. The opposite is anisotropic (preferential) etching. The a anisotropic and originally applied to the propagation of light through a solid terms isotropic also (DCE) now used in dry chemical etching They with regard to shaping a mineral. are reference or hole with ionized gases without via to the polish (isotropic) or pit, channel (anisotropic) nature of a liquid etch solution. preferential JAR 109. ETCH The use of any closed vessel for etching in which parts or specimens are immersed. (Jug). Beaker Bottle Etch. See Etch; 110. JET ETCH fine stream of liquid under pressure applied as an etchant, and A often for shaping most the of a solid specimen, structuring exterior material surface, etch cutting a hole through a a wafer, etc. May be a single or multiple jet system with or without electric current. There are jet combining etch/cut action for slicing or dicing material with high velocity systems steam, electrical or an acid. There also are hot-melt gas, plasma composites deposited water, in surfaces on . not etch action, but used . constructing Solid State substrates. . 111. JUNCTION ETCH As a semiconductor term, the development of a p-n junction by staining, etching or can selective heavy metals industry, weld joints In the be developed or cleaned by plating. etching or light sandblasting. In the plating and cladding industries, etching to develop See interface between layers can be done with a jet. joints Layer Etch; Stain Etch; Selective Etch; Jet Etch. © 1991 by CRC Press LLC

63 50 CRC of Metal Etchants Handbook KEY ETCH 112. etch primary a clean/etch sequence, or any solution applied in a solution A within around is fundamental solution. A solution a which other that processing step considered revolve. solutions or processing ETCH KRYPTON 113. ionized krypton, Kr+, as an etch use material damaging agent by irradiation. The of or of The pressure change to etch single crystal krypton grown under pressure and use vapor vacuum cryogenic conditions. ETCH LASER 114. electrons propagated by light at a controlled frequency and power level to effect of Use etch action. types of lasers are used to Several channels and other structures for an etching Solid State devices; for material cutting, such as preparing circuit substrates; as operational to increase crystallite size on dendritic crystals, or in conversion of carbon to a annealing (DLC). See Etch; Flash Etch; Irradiation Etch; Ion diamond-like-compound Electron-Beam Etch. LAYER 115. ETCH in Solid State processing, die etch development of epitaxy multilayer struc As applied more device or in material studies. As a fabrication general term, the etch removal tures in a specific layer of material from a dissimilar material. of may be total removal as in oxide It or stripping from a semiconductor surface, or selective removal through a photo resist nitride similar subsequent coating to develop patterns for or device fabrication. See Junction surface Etch. 116. ETCH LIFT-OFF film specific developed to A thin technique metallization from a photolitho- remove graphically prepared wafer surface. Wafers are soaked, sprayed and/or lightly scrubbed with a plastic Q-tip in acetone. The acetone dissolves the photo resist layer used for patterning foam loosens excess by lift-off, and exposes the metallized pattern for further device which metal float-off is separate This distinct operation, though similar to the a technique. processing. and Float-off Etch. See 117. LIGHT ETCH term has been used in two contexts: (1) as a physical term to differentiate between The etching; of in the sense light-medium-heavy a slow, minimum removal etch, and (2) the or enhance of or in conjunction with solutions to alone, etching reaction or for selective use light action. White light most widely used, plating as a strobe light for semiconductor p-n such junction with copper. See Electron Beam plating Laser Etch. Etch; 118. LIGHT FIGURE ETCH The use of preferential etchants to develop surface etch pit and dislocations on the surface of a single crystal ingot face or wafer and used to crystallographically orient the surface cut reflected processing This is standard practice in the by of single crystal ingots of all light. ingots materials. be noted that many single crystal should can be cleaved into wafers on It preferred fracture planes, which does not always require etching to obtained surface figures silicon for orientation (LFO). After etching face-cut figure ingots in boiling KOH, 5 light min, as an example, the ingot is mounted on a ceramic block, then on an x-y-z positioner surface and pinhole light is reflected off of the a back into a black box. The pattern that © 1991 by CRC Press LLC

64 51 appears the back of the box is then used to orient the ingot for cutting wafers. Orientation at can be

65 52 CRC of Metal Etchants Handbook MAGNETIC ETCH 126. real a yet has been used in two ways: (1) magnetic powder has etching Not method, domain wafer ferromagnetic materials to develop of structure, on surfaces been brushed titanate and ferrites; (2) iron or carbon powder such on a preferentially as barium brushed surface accentuate defects and etched patterns. to are magnet-stir hot wafer etched There a Teflon or plates magnet is dropped into the solution, then solution where plastic-coated and controlled by the hot plate dials. Barium titanate, being fabricated as an rotation heat is orient (magnetic flux) poled in water to transducer, domains. See ultrasonic electrically Etch. Gravity 127. ETCH MATTE finish etch used for decorative A on metal surfaces, such as copper or surface purposes The surface has a low-profile grain-like nickel. with a dull sheen, and can be as structure a finish. See Satin Etch; Silk Etch. semi-matte MEDIUM ETCH 128. medium, two with regard to time, as a slow, (1) or fast etch, and (2) Used ways: in to solution strength, as weak, with or strong. regard medium, MELT-AWAY 129. ETCH for of thin film from separation substrate a microscope study by heat liquefying The a removal of the substrate. Etch removal and a metal thin film or alloyed pre-form, wire, of etc., observe the pit formed in the material surface by the metal. Semiconductor wafers to alloyed the junctions have been etched from p-n back to observe the buried junction- with substrates the bulk wafer. Sodium chloride, (100) front have been heated to the liquid in state in order to remove a thin film for TEM study, rather than the usual use of water to dissolve the interface. substrate/film MELT-BACK ETCH 130. etching Solid relative to wafer surface term during epitaxy growth, A State specialized using indium on indium phosphide, InP, or gallium such gallium arsenide, GaAs as on liquid epitaxy (LPE). The method is used phase clean the surfaces to reduce the during to of defects in the epitaxy film. growth MESA 131. ETCH a etching roughly cylindrical column or pylon on a single crystal surface as a The of junction device structure. In Solid State, as a p-n mesa, it is the mesa diode. As an single array mesas in the fabrication of SCRs, of are elements for power distribution and they control in the electrical operation of the device. Mesas are commonly formed with a slightly preferential etch that the mesa side slopes have a degree of crystallographic orientation. such can dry techniques, the mesa sides etching be more cylindrical without Using chemical facets. See Pylon Etch; Structure Etch. crystal METAL 132. ETCH any the sense, any solution used In etch broadest metal. More commonly, the use of to a liquified metal as an etch medium on high temperature, chemically inert metals, such as molybdenum, tantalum, titanium. Occasionally refers to the metallizing of a material or Etch; with surface decorate defects. See Decoration in-diffusion Molten Flux Etch. to 133. METALLOGRAPHIC ETCH Term primarily used in the preparation of metals and alloys as specimens for defect and the structure using preferential etches. Common in analysis metals industries and in geology, © 1991 by CRC Press LLC

66 53 and Solid State companies maintain a metallographic laboratory for material inspection most evaluation of The etch can be macro- or micro-etch as a size definition. and processing. Etch; Micro Preferential Etch. See Macro Etch; ETCH 134. METALLURGICAL Not etch applied to a metal or alloy specimen with reference to the but common, any reference metallurgical as a science. Also with engineering to the use field metallurgy or of of microscope for material observation. a metallurgical ETCH MICRO 135. cannot figure, etched on a surface that structure be easily observed by Any or defect, eye, and requires a microscope for the viewing. Both macro- and micro- unaided proper are widely used in the study terms metallographic specimens in general metal etch of not as often used in Solid processing, processing. See Metallurgical Etch; Macro Etch. State 136. ETCH MILLING Solid State refers to the use of an ion milling vacuum system where ionized argon In it nitrogen etch is used to or remove and pattern thin film metallization on circuit (N+) (Ar+) occasionally active general metal processing, it devices. In means the use of or substrates lathe or cutting mill for a combination a cutting, etching, or shaping of a part, and may of be an electrolytic etch with the lathe head as the cathode. as MINIMUM 137. ETCH etch used for a short period of time, or one that removes An or no material during little the etching period. See Slow Etch. 138. MIST ETCH The use of an etch as a spray of finely divided particles as from an atomizer. The method has been final etch cleaning of a surface; to fine-tune and optimize electrical used for to an junction semiconductor device; or p-n develop defects, of exposed characteristics figures in a surface for optimum clarity observation. structure, in metallographic or Used etching develop fine structure of crystallites, phases to See Vapor Etch. specimen etc. MOLAR ETCH 139. solution mixed by its molecular weight. The total of the atomic weights of the Any one elements molecular gram-weight of the substance as dissolved in one liter is compound water (1 liter = 1000 ml): of H = 39.102 = 1.008 K wt) (at HC1: wt) KOH: (at 35.453 = O = Cl 15.999 H = 1.000 Total Total 56.109 36.461 g g hydroxide, KOH, as an example, potassium solutions would be: (1) Using approximate M KOH = 56 1 (2) 2 M KOH = 112 g/1; or (3) a 0.5 M KOH solution about 28 g/1. g/1; A Molar solution may be used as the etching solution by itself, or be only one constituent of an mixture. See Normal Etch. etch MOLTEN ETCH 140. FLUX metal or compound liquidized at Any slightly above its melting point without the or inclusion of water or other liquid solvent. In Solid State processing, as an example, KOH, used NaOH, a IKOHilNaOH (eutectic) mixture are or as dislocation etches in their molten © 1991 by CRC Press LLC

67 54 CRC of Metal Etchants Handbook at about Other molten fluxes of nitrates and carbonates (NaNO3 or KCO3, state 365°C. used in metal industry for etching, cleaning or structuring of materials. examples) are the crystal used also are of certain compounds, such as single for garnets. These fluxes growth Etch; Melt-back Etch. Flux See ETCH ~~ 141. NAMED solutions letter, a number, etch chemical, individual's name, or a combination Many have Where shown have been given to a specific etch solution, it is such. after ETCH of names is the formats used in Chapter 2. The following in a list of some of the NAME etchant in nomenclature that have appeared in the literature: variations Name Example Chemical name Single acid/chemical: HC1; H2SO4; KOH, etc. + Chemical name letter A; ♦Iodine etch Tri-iodide Chemical acronym Mixed solutions: bromine-methanol or (BRM), hydrofluoric **buffered acid (BHF) ratio Volume 1:1:1 *** Letter(s)/volume ratio BK-112;BK-213 Letter(s)/number SR2 CP4; Individual's name Billig's etch; Dash Wright etch; Sirtl etch; etch; Makuri's reagent, etc. Individual's number + name Ellis #1; #2 Camp Color etch**** White Individual's name(s), acronym etch etch*****; A/B BJ mixture component Two etch***** AB abbreviation Company etch***** RCA abbreviation Company + number RCA #1; GE-3 + chemical symbol Company WAg only Number ASTM 407-70 pamphlet See varying are "iodine etch" ♦There of several composition, several developed many mixtures years ago for a specific metal or compound, such that the general term "iodine etch" can be any one several solutions. of the BHF BRM designations should be considered general terms, not a specific **Both and are, different several hundred possible compositions, and many solution as there etch literally, shown only. the acronym are mixtures by not of a volume use alone, is numerical recommended. From the example ***The ratio, — 1:1:1 — there are many show mixtures with such a ratio. acid A designation along with the ratio — BK-112 — is an improvement as it becomes letter specific user nomenclature, but the a still needs to know the acids involved. etchant misleading. ****The the name "White etch" is of When HF:HNO3 solutions were first use being applied to silicon etching several of them were termed "White etch", even though the solutions clear and transparent, not white in color. are use former the terms AB or A/B can be confusing. In the *****The case, it has been of portion to a two-part solution with an "A" describe and a "B" portion used separately; used but also has been shown as A-B — with the total quantity of the two solutions mixed together the when use, or, a specified ratio of for solutions mixed. And another conflict with ready the use of an "A" and "B" nomenclature is the A/B etch named after Abrahams and Bioucchi. © 1991 by CRC Press LLC

68 55 The of the term "RCA etch" is also questionable, as several hundred etch solutions use been developed RCA over the years. In this case, the "RCA etch" usually refers have at * A'' "B " solutions developed for cleaning silicon by Kern and Puotinenr. Further, to the' and of used the "A" or "B" portion only those two solutions without developers some have yet still call out "RCA etch". letter designation, OXIDE NATIVE 142. ETCH inorganic metals and compounds become surface passivated by an oxide Almost all to as Such oxides are called native oxides exposed they are a normal attribute of when air. type and artificially produced. The removal of this not of oxide can be critical the surface metal processing, such as preparing aluminum surfaces for to as well as copper, plating nickel, and steels. It is of major importance in preparing semiconductor wafers for iron, metallization, diffusion, as such residual oxides can affect device characteristics. etching, etc., a solution etch remove such oxides is called used native oxide removal etch to Any to it from a solution used to etch an oxide thin film or material, such as titanium differentiate TiO2 or quartz, SiO2, and called an "oxide etch". It should be realized that a dioxide, oxide though occurs under natural atmospheric conditions, even "native" it is called only after in State such where residual surface oxide remains Solid chemical treatment. processing See Oxide Etch 143. NEUTRAL ETCH A very slow, nonreactive etch, when used as a cleaning solution, or the use of water as a 7 neutral wash or quenching solvent. pH NITRIDE ETCH 144. silicon several nitride compounds, such as grown nitride, Si3N4 There artificially are nitride, A1N. The metal industries use a nitridization and to condition aluminum process surfaces the Solid State industry is developing and applying both oxide and nitride metal and thin films in processes. surface either case, any etch solution used to remove or pattern In a is called a nitride etch, and many also can be used on oxides. nitride NORMAL 145. ETCH etch solution mixed on the basis of An total valence of the metallic radical ions in the solution. To obtain the number of grams of a compound for a Normal solution: divide one gram-molecular-weight (1 by the total valence number of the element and radical: mole) #139 gram computation of the (See mole.). Examples of Normal solution computations for are (1) hydroxide, NaOH: Sodium Na+1 metallic valence of "1" = (OH"1 = hydroxyl valence of "1" [ref. only]) and 40 (Na at wt) = 40 g or 1 gram- mole = g 40 be Normal solution. In this instance, it also 1 to (N) a 1 Molar (A/) solution. happens (2) Sulfuric acid, H2SO4 H2+1 = metallic valence of "2" wt (SO4~1/2 sulfate valence of "2" [ref. only]) and 98 (total at - elements) = 49 g or 1 gram-mole = 49 g © 1991 by CRC Press LLC

69 56 CRC of Metal Etchants Handbook this case, g/1 of water (1000 ml H2O) of sulfuric acid is a 1 N solution. It also In 49 be a M solution. happens to 0.S such 50 N solution of a chemical base, ml as sodium hydroxide, is mixed If Note: a equal quantity of an acid N solution, such as sulfuric acid, the resulting solution with an neutral 7, like be water). will (pH primary NH3, hydroxide, NH4OH are the ammonium chemical base ammonia, and Both to neutralize acid sumps before effluent discharge into solutions disposal sewer used waste lines. are mixed with both N and etchants constituents, even combining acids and Many M but equal quantities of bases, and M solutions are not mixed or else a neutral solution N will without etch action. result OIL ETCH 146. ~ oils normally act as etchants on some metals, even though they are base Petroleum can similar of coolants in metal cutting, and as processing. For critical materials, only thought as semiconductor wafers and assembly or test parts, such oil coolants with various such for additives prevent, foaming, etc. can be severely degraded because of chemical rust residual as and other anomalies, such that silicones are used attack, replacement films, for oils. liquids petroleum ORIENTATION ETCH 147. single preferential used A determine the solution crystal orientation of a specimen to surface by development of surface etch pits. See Light Figure Etch; Optical Orientation Etch; Figure Etch. OXIDE CLEANING 148. ETCH It developed an oxide surface with minimum or no removal. clean can be to solution A or solvent. alkali, acid, 149. OXIDE ETCH solution to etch a metallic oxide material. See used immediately following Any the for special case applications. terms OXIDE REMOVAL 150. ETCH In State processing, often refers to removal of a native oxide on a material surface Solid A12O3) to processing. It also is prior where a deposited oxide thin film (SiO2, further used is pattern etched or removed. See being Oxide Etch. Native 151. OZONE ETCH Ozone, O3, is an extremely strong oxidizing agent. In Solid State and some metal processing it used, by itself, as a surface cleaner. Caution should be exercised as con is producing greater 1% in air centrations be hazardous to health. There are ozone than can commercial systems used in metal cleaning for material surface cleaning. Similar processing units are used in movie theaters or other commercial offices and buildings as an air freshener, market and smoke removal. (Ozone ash trays are on the cigarette for home or office for use.) 152. PARTICULATE ETCH Any solution used to remove a material matrix and expose embedded particles without some affecting particles. This is common in the ore processing operations where gangue © 1991 by CRC Press LLC

70 57 material separated, and in some material studies. The etch may expose the paniculate, is or be to remove the particles for separate microscope study. only, used ETCH 153. PASSIVATION remove used ways: (1) a solution developed to two a passivating thin term in is The surface, film as a native oxide, or (2) a solution that will introduce a surface from a such An iodine solution has been used on diamonds in the film case as pas passivation. latter against with H3PO4, and an I2:Me0H rinse applied as an ionic surface sivation etching system silicon wafers prior to diffusion. removal contamination on ETCH 154. PATTERN a solution etch develop structure in or on that surface and there are several Any will applications and methods: (i) to develop defects in surfaces; different to differentiate (ii) between structure, or minerals in a mixture material; (iii) to etch through a masking elements, such as resist patterned thin film oxides to remove the oxide down to the layer, photo or the pattern; (iv) etching via holes, desired (v) circuit pattern etching of substrate in See Photo Resist Etch; Thermal Etch; Defect Etch; Figure Etch; Vacuum Etch; substrates. Etch. Structure PHASE ETCH 155. to metal and metal alloy etching of steel in the etch development of alpha-, Common or of structure, and the recognition beta-, martensite, carbide, and similar crystal delta-phase structures. 156. RESIST ETCH PHOTO COP-, resist such as the Photo series, lacquers, or PMMA types used in device AZ- and circuit fabrication of semiconductor devices, have their own solutions called developers, and used UV exposure of the resists in fabricating patterns. The developers are designed after each type commercial photo resist formulation, many contain hydroxide, such that for of particularly be should the material being processed in observed vulnerable to attack caution if alkaline solutions. by that in removing photo resists before or after metallization of the specimens or Note the is widely used solvent wafers, acetone (a ketone) by soaking, spraying, or light most of specimen surfaces. scrubbing the 157. PICKLING ETCH common in metal processing and plating. Metal surfaces are soak-cleaned for Term contamination. such for removal of scale, or other type as See Scale Etch; conditioning, Conditioning Etch. 158. PINHOLE ETCH Small, roughly circular defects in a deposited thin film are referred to as "pinholes" and may may not go completely through the film. Any solution or method used to locate or observe pinhole pinholes is called a and etch. Such pinholes can be created by con such insufficient on substrate surface, be due to a cohesion within the growing thin tamination film, or from entrapment of particles in the film. Oxide and nitride thin films are particularly the prone in Solid State processing, and are pinholing subject of much study. The term to also is applied to the etching of a controlled pinhole, such as for thickness measurement of of the diffusion depth profiling, or observation and study film, epitaxy layer structures. See Structure Etch; Profile Etch. © 1991 by CRC Press LLC

71 58 CRC of Metal Etchants Handbook PIT ETCH 159. etch preferential develop dislocations or surface damage pits in single crystal used A to specimens This wet chemical etching (WCE). similar includes controlled damage wafers or as through as structure. Dry chemical etching (DCE) device a photo resist, development pit a oxide/nitride thin film mask, as well as WCE, also for metal, fabrication. Note or device dislocation conform to crystallographic structure and bulk plane directions, such as that pits triangular not on a (111) wafer surface, and do sharp increase in size to any extent pit the not etching; a surface damage pit does whereas conform to crystal planes and extended with expand in size with extended etching with a flat pit bottom directions, may be heavily that terraced, will disappear when the bulk, undamaged material surface is reached. Un and bulk surfaces be recognized by their usual high reflectivity, and common near- damaged can near-hexagon (111) particularly recognizable on and oriented surfaces. mammillary structure, structure, wafer (100) is more block-like in bulk coincident with the square out The surface dislocation and surface etch pits. See Preferential Etch; Via Hole line Selective Etch. Etch; 160. ETCH PLANAR reflective polish produces a very flat, highly that surface. Now a major surface A etch for three-dimensional layered electronic device and finish substrate structuring. circuit 161. ETCH PLANE or solution to develop a Preferential facet, used plane in a single crystal material. crystal Occasionally with reference to etching a planar surface. See Planar Etch; Crystallographic Etch; Structure Etch. PLASMA ETCH 162. Either of particles to effect cleaning or etching. gas RF or DC plasmas The ionized use RF more common are microwave, high frequency electronic device fabrication. used, in Dry Etching; RF Plasma Chemical See Etch. POLAR ETCH 163. etch used on a polar material, such as the compound semiconductors and, in Any particular, the oriented surfaces. Gallium arsenide, as an example: the positive (11 l)Ga (111) surface surface negative (1 ll)As[(l 11)B] the show different etching phenom [(111)A] vs. One surface_will etch preferentially with defects; whereas ena. opposed surface, usually the the (lll)B, will be erratic, and it negative difficult to develop an etch solution that will is equally polish both surfaces. Note that in compound semiconductors there also may be different electronic See Polarity Etch. characteristics. POLARITY ETCH 164. characteristics used develop the Any etching to of polar compounds, solution preferential as GaAs, InP, AlSb, or their associated trinary such quaternary forms. See Polar Etch. and 165. ETCH POLE magnetizable specialized applied to the A of term structure in materials such as etching barium titanate, Ba2Ti03, where the magnetic domains are aligned by polarization with devices electrolytic a magnetic flux. Garnet memory and as a computer chip are solutions similarly poled. The term also is applied in the etching of single crystal spheres for finite crystallographic crystal the solution produces only when "pole" figures at axial points, form, rather than developing exterior facets (planes) as a finite crystal solid form. © 1991 by CRC Press LLC

72 59 166. ETCH POLISH etch solution attacks a material surface at an equal rate in all crystal plane Any that regard directions orientation. This is the opposite of preferential etching. In to without their single polished etching, and much metal etching, a State surface is required all Solid crystal is fabrication and parts, such that polish etching devices of great importance, and the in of criterion in processes. It also is a called isotropic etching. See Isotropic Etch. major now PREFERENTIAL 167. ETCH rates, solution crystallographic planes at different attack and produce etch that will Any controlled by those planes. It is the opposite structure polish etching. Much of the as of and etching of semiconductors wafers selective similar materials as devices structuring and done is preferential etching, as well as in crystallographic study of single crystals. Such with device includes formation of pits, channels, "V" grooves, via holes, saw-tooth processing This was only method of selective structuring semiconductor devices (wet structures. the or of etching) until the fairly recent advent etching dry chemical etching. chemical electrolytic Anisotropic etching now called anisotropic etching. See is Etch. Preferential also PRE-PLATE ETCH 168. acid, alkali, salt, or alcohol solution used Any clean or condition a material surface to prior plating. See Pickling Etch; Descaling Etch. to PRESSURE 169. ETCH forming of material, or alteration of a surface by direct pressure, alone, and may The or heat gas atmosphere when a furnace or a vacuum is used. Natural pressure produces include etch figures on meteor surfaces during atmospheric entry; six-rayed star percussion figures are formed (0001) oriented mica sheets by striking; controlled point pressure damaging on single crystal surface is used in forming etched pits or grooves in device structuring. of wafer Etch. Autoclave See ETCH PRIMING 170. preparation is with two meanings: term the type applied of a surface prior to The (1) such as a priming etch for conditioning, and (2) the plating, of a small piece of the adding material be etched to the etching solution prior to use. The latter method is used on highly to the solutions, reactive 1HF:3HNO3, to obtain an even etch rate from such beginning. See as Seeded Etch; Conditioning Etch. 171. PROFILE ETCH ~~~~ The term is used in two ways: (1) selective etching of any form of structure in or on material, and profile etching. The latter includes etching through thin film or metal (2) to etching and measure diffusion depths; observe study epitaxy layer structures. masks; to wafers are processed with (100) surface orientation and, Many profile study of structures, for are by cleaving in a <110> bulk cross-sectioned direction. See Angle Etch. plane 172. PYLON ETCH Any etch used to form vertical, roughly cylindrical structures on a surface. A slightly preferential etch produce facetted side-wall slopes with WCE; whereas smooth, unfa- will DCE walls be fabricated by can etching. See Mesa Etch. cetted 173. QUALITY ETCH such Applied regard to the purity of acids and chemicals used, with as electronic grade vs. commercial grade liquids or gases. © 1991 by CRC Press LLC

73 60 CRC of Metal Etchants Handbook QUANTITY ETCH 174. or etching a number of parts at a single time, or the use of a large cleaning The of See Volume Etch; solution. Etch. volume of Batch ETCH RAPID 175. etch. Any against a slow fast As an example, the 1HF:3HNO3 mixture etching solution as most rapid etch solution of is two-component etching system. the this RASTER 176. ETCH (E-beam) using high intensity electrons; electron lithography, beam etching Electron computer is used for beam positioning and exposure of photo where patterns; and a resist etching be referred to as raster etching may annealing, as has been irradiation with laser or gases or radiation with particles in ionic sense of using a controlled beam of energized the particles, etc., to effect an etching action. The term relates to the raster tracking electrons, of a screen. element computer ETCH RATE 177. two ways: (1) the time period Used any solution required to obtain desired results, in for (2) the physical reactivity time/rate of specific mixtures. The latter most important when or exothermic rates Determining etch using is a major factor in processing. solutions. REACTIVE ETCH 178. ION form of dry chemical etching (DCE) where one or more of the ionized gases A a is reactive such as BC13 used in gas, aluminum oxide surface films. Common acronym: etching RIE. This form of etching is increasingly used for selective etch structuring of electronic devices that layered epitaxy and metallized structure. Note that there are a number contain specifically designed ionized gas etching systems with their own special acronyms, of dry Etch; operate a all manner. See Dry Etch; Gas in Dry Chemical Etching though similar (DCE). 179. REDOX ETCH referred to as oxidation-reduction reaction, where one acid is a reducing Originally and agent, other an oxidizer. HF:HNO3 solutions are an atypical example, where HF the applied as the and HNO3 the oxidizer. As acts REDOX etching system, the term is reducer a to etching with pH control selective the solution. of 180. RELIEF ETCH Etching of any form of structure on a surface. It can be as a raised mesa, pit, channel, or via-hole through the material. See Figure Etch; Structure Etch; Selective Etch. completely REMOVAL 181. ETCH solution that will dissolve and reduce the thickness or weight of a material. All Any removal. are etches and many are classified by their etch-rate of removal See Rough type Etch; Heavy Etch. 182. RF PLASMA ETCH Another term for dry chemical etching (DCE), and used as a general term for any form of gas etching or cleaning. ionized 183. ROLLING ETCH Any solution used with a rolling motion. Single crystal spheres are etch polished in a to beaker at about 45° and hand swirled held produce a slow rolling action of the spheres. © 1991 by CRC Press LLC

74 61 Occasionally with reference to a boiling solution that has a rolling or roiling motion. used also has with regard to allowing a specimen to roll and tumble down an incline It been used etching during the etching of an extruded, rolled metal sheet... to include period, or an against the rolled direction. or etching in 184. ROUGH ETCH applied with two meanings: (1) general reduction in thickness or size Has been without to finish and measured in mils of depth removed from a surface or by total surface regard etch of specimen and (2) a controlled a to roughen a surface. Glass loss gram-weight slides have had one side roughed with HP vapor etching to improve thin film microscope for of study gold adhesion the film growth and structure characteristics, and some TEM finish. parts finished with a named roughness, such as a matte or satin surface metal are Removal Matte Etch; Satin Etch; See Etch. SAND ETCH 185. term has been applied with reference to the use of a dry abrasive to effect removal The with gas abrasive under action pressure (nitrogen) applied by spray or jet. The method the is to clean, roughen, or condition a surface. also used are usually considered as lapping and polishing compounds, Abrasives fine although jets sand have been used to fabricate of to drill holes through material, or form screws, cavities (pits) in a surface. The use of S.S. White Dental Unit was one of the original methods used dice silicon and germanium wafers, and the units are still used for sand to of surfaces, bead blasting technique for cleaning metal parts. See Abrasive cleaning e.g., Etch. SATIN 186. ETCH used in the metal industry Specialized an etch solution produces a surface term where that has the appearance of satin cloth. The surface structure contains variable finish length and lines, roughly parallel with some cross-hatching, and with the reflective sheen of width on The is called satin finishing, satin cloth. is used as a decorative finish method copper, and nickel, and other metals. See brass Etch. Matte 187. SATURATION ETCH A solution containing the maximum amount of a dissolved chemical in water, alcohol or solvent room temperature and standard pressure. If such a solution is mixed above at temperature, super-saturated under pressure, it is called a room solution. The latter and but is solution to any extent in material processing, not saturated solutions can be used used in six contexts: 1. A chemical is mixed as a saturated solution. In the Etchant Section, Chapter 2, such solutions are under COMPOSITION as: shown Example: ... CrO3, sat. sol. 50 ml 2. One constituent of a solution may be "saturated'* with a second. This is shown as: Example: ml... MeOH 100 x ... *I2 * saturate MeOH with I2 © 1991 by CRC Press LLC

75 62 CRC of Metal Etchants Handbook When steam used for cleaning it may be under pressure, and referred to as' 'saturated 3. is steam". Where pad is used for chem/mech polishing or damage removal from surfaces, a 4. cloth be the with may etch solution. the pad "saturated" grown that crystals or solvent soluble are are from saturated solutions. Single 5. water sodium chloride, NaCl, is artificially grown by evaporation from such High purity as cut oriented substrates, and used for thin film metal evaporation solutions, (100) growth compounds in material studies. epitaxy of or repeated use of an etchant, removal rate control can be 6. due to the solution After lost "saturated" by-products that no longer with etch reaction to continue. becoming allow mixture constituent can be completely One leaving the solution "saturated" used, with nonreactive constituent. This is common to solutions containing hydrogen a H2O2, where peroxide rapidly depletes. peroxide, the (ACID) SAW ETCH 188. are cut from an ingot by a wire that is wetted with acid, it When called the wafers is technique The wire can be of (AST). SST, rayon, plastic thread, etc. acid-saw iron, cutting, lapping, or polishing a surface mechanically there is In a subsurface always damaged remaining with damage depth determined by abrasive grit size and other zone Solid chem/mech wafers, such as silicon or gallium arsenide, are often factors. polished State referred bromine-methanol solutions to with this damaged zone. This has been (BRM) remove to as saw damage removal etching. 189. SCALE ETCH Term used in metal processing where slow etch solutions are used to remove surface contamination — oils, dirt — that are called "scale". See Descaling Etch; Soak oxidation, Etch. 190. SEEDED ETCH to to added a small piece of the material is be etched. This technique solution which Any with is that initially show a rapid rate of attack in the first few seconds, then used solutions more controllable linear rate. A mixture of 1HF:3HNO3 is of this type. By initially seeding a a such allowing the piece to completely be dissolved, the etchant becomes more solution, for controlled removal. controllable linear 191. SEGREGATE ETCH etch used to remove a matrix material to expose a paniculate Any segregate embedded. or This be as a contaminant included during may growth or a new compound due to ingot regrowth, such as is observed in fabricating silicides as blocking layers in Solid State devices. See Paniculate Etch. SELECTIVE ETCH 192. etching chemical (WCE) or dry Either etching (DCE), where the solution wet chemical gas is used to structure a surface, or or remove specific material layers in a heterojunction/ to heterostructure In the latter case, the etch device. attack one material layer and not will another, and by suitable masking of surfaces with a thin film oxide, photo resist, or metal, structure then pattern, pits, channels, via-holes, or other a can be etched selectively. exposing 193. SEQUENCE ETCH A single solution, or a series of different solutions used in a consecutive order of etching and steps. sequences are of this type, Clean/etch can include vapor degreasing, etch removal © 1991 by CRC Press LLC

76 63 of damage, acid etching, alkali etching, with water and/or alcohol rinses following subsurface or the as individual steps. etching, rinses also The to the etching of different layers of heterostructure devices is term applied Etch; mixtures etch again consecutively. See Series Etch; Step are Stop where different used Etch. SERIES ETCH 194. been used in two ways: Term a single etchant used two or more times in sequence, has (1) as dip etching or (2) different acids, alkalies, and alcohols used in a sequence. See such in Etch; Chem/Mech Etch. Sequence 195. SHAPING ETCH solution used to etch form a solid material. May be electrolytic Any and term etching, has used with reference to electroforming. been SHIM ETCH 196. sheet etching material, such as thin nickel shim-stock pattern etching for Either of the an evaporation mask; use the etch thinning of a material to shim thickness, e.g., at as or under about 0.010". or SHORT ETCH 197. Any etch used for a brief period of time, as against a long period, such as a solution etch. Dip soak Etch. See SIZING 198. ETCH Solid State material processing the term In to the etch reduction of physical size applies to a particular dimension, such as in thinning of a specimen for TEM microscope study. In general material there is a gelatinous substance called "size", much like a weak processing, those which as a surface coating with applications similar to used in photolithographic glue is with photo resist lacquers. processing paper manufacture, size is added to the pulp to prevent ink from running, and is the In accurate more where tree rosins and alums are added as the sizing compounds. meaning, SLOSH 199. ETCH etch solution used with either movement of the Any or the part. See Agitation solution Etch. 200. SLOW ETCH The removal rate of a solution as against a rapid or fast rate. Many polish etch solutions are designed be slow for maximum planarity of surfaces, and for the prevention of erratic to anomalies a can occur from surface too rapid etch. See Soak Etch. that 201. SLUSH ETCH cold containing or snow Etches ice solutions. as 202. SNOW ETCH Some cold etch solution use snow as one constituent to establish a specific temperature. the As they are sometimes referred to as group, "snow etches". See section on Water, a Chapter 2, for "Cold Etchants". 203. ETCH SOAK A slow cleaning or etching solution where the part remains immersed for an extended © 1991 by CRC Press LLC

77 64 CRC of Metal Etchants Handbook of time. to the metal and plating industries for surface preparation. See period Common Conditioning Etch. 204. SOLID ETCH been (2) in two ways: (1) the etching of any solid material, or has molten The used term KOH a solid chemical compound, such as liquified pellets. See Molten with flux etching Flux Etch. ETCH SOLUTION 205. used for wet chemical etching (WCE) where the etchant is a liquid; whereas dry term A (DCE) gases. ionized etching chemical uses ETCH SOLVENT 206. of a chemical solvent as a cleaning The etching solution as against an acid, alkali, use or alcohol. A few metallic compounds can only be etched in or solvent. Trichloroethylene, a TCE; TCA; and Freons are the primary vapor degreasing solvents used for trichloroethane, cleaning. parts ETCH 207. SPARK of called electric spark to generate an etching action. As a cutting method, use The an loop a method an electrically activated wire etching in alcohol is used to spark erosion; as pinholes in oxide and nitride thin films by the appearance of observe come from bubbles the surface as the wire passes over in the alcohol solution. Metal spheres, both substrate crystal from polycrystalline, have been formed single chips of material by electrical and spark from copper pot under argon, and sparking vaporization of material from a surface a is a standard method for spectrographic analysis. 208. SPHERE ETCH term has used in two ways: (1) the slow polish etching of a material sphere, The been the sphere etching of a single crystal (2) to finite crystal form (FCF). Single or preferential and have widely used to establish etch been oxidation rates on convex surfaces crystal spheres metal in metallic compound development for device structuring applications. See Finite and Form Etch. SPIN ETCH 209. rotating. a with the solution Etching part specimen See Agitation Etch; Photo of and/or Etch. Resist SPUTTER 210. ETCH See term RF or DC plasma A for RF Plasma Etch. etching. 211. SQUIRT ETCH Any solution used in the form of a liquid jet or spray. Term often applied when a polyethylene bottle as a "squirt bottle" is used, and there are many designed jet etch know See Mist Etch; systems. Etch; Spray Etch. Jet STACKING ETCH 212. FAULT dislocation term used Specialized single crystal processing. Specific preferential etches in have been developed to accentuate this form of defect, which can be common to oxide and of nitride The defect appears as a series films. short, parallel slip lines in a translucent thin to transparent thin section, and are a three-dimensional defect relative to x,y,z crystallo- stress graphic They occur due to inherent axes. factors from the difference between coef- © 1991 by CRC Press LLC

78 65 ficients expansion of oxide/nitride thin films and the substrate materials on which they of deposited. The faults can be in both the oxide/nitride or in the immediate are stacking near substrate between the two compounds (SiO2/Si interface, as an the surface interface Etch; Etch. Defect Preferential See example). 213. STAGNANT ETCH applied to an etch The that has been allowed to stand before use. The term is mixture have been so used, with effective depletion of the H2SO4:H2O2 peroxide. mixtures hydrogen also been allowed to sit 24 h before use with the effective vaporization loss of the CP4 has Aqua is (1HC1:3HNO3) fraction. an example of a solution that requires aging bromine regia solution. but is not a stagnant it See Aged Etch. before use, STAIN ETCH 214. liquid gas, or Any such as air or oxygen, producing a coloration action on a solution with minimum removal. HF:HNO3 solutions, either high in HF on high in surface etch stain such surface rather than etch. Other solutions, will as those containing salts HNO3, a Both copper, gold, also will produce stains. or HF and HNO3 develop red/blue/ of silver color; whereas metal stains are grey to black. yellow has Staining used for depth profiling of diffused p-n junctions; in delineating been structures planar to observe epitaxy layer or in cleaved (110) cross- exposed junctions; which are stained after cleaving. Spheres sections, been oxidized in oxide growth rate have studies to crystal planes, and relative samples are heat-tinted by oxidation metallographic in air on a hot plate. See Junction Etch; Metallographic Etch. 215. STANDARD ETCH term has used in three ways: (1) a solution developed for a particular process The been standard chemical that process; (2) a solution used as a reference in material or a becomes for as (3) solution that has and standard for a particular use, such as CP4 a analysis, become polish or Sirtl etch for etch, a defects. STEAM ETCH 216. use The water at its boiling point as a cleaning or etching solution. Steam cleaning of under for cleaning buildings, clothing, and small parts in autoclaves. In material pressure the surface actively getters and uses a portion of the material processing in forming steam to oxide, as the silicon wafer surface atoms being used such form silicon dioxide. See a Autoclave Etch. 217. STEP ETCH Any solution used to form an etched step in a material surface. The method is used in device structuring; measure a layer thickness; to profile diffused junction depths; to trace to in or material bulk; and may be single defects multiple steps. A specimen surface is a or coasted stripes of Apiezon-W (black wax) with photo resist coated in a successively similar manner, being etched to a controlled depth between each coating to form the steps. See Junction Structure Etch; Selective Etch. Etch; STILL 218. ETCH solution used without movement of either A solution or the part being etched. Some the very slow polishing etches have been used in this manner. 219. ETCH STIR Any solution used with a rotational motion. Magnetic stirring hot plates; hand swirling; © 1991 by CRC Press LLC

79 66 CRC of Metal Etchants Handbook hand or operated stirring rod in solution, etc. In etching wafer surfaces for a electrically speed is so as to prevent flow patterns being developed. planarity, rotation controlled ETCH STOP 220. attack etch solution that will called:' one material and not another Also Any 'Etch-Stop.'' layer-type structure. A fairly recent term as applied to the selective etching of semi in a devices, heterostructure the method has been in existence for many, conductor although in specific the metals and semiconductor industries without having a years name many both etching the to as the etch removal or pattern process, of an oxide with HF that applied such not attack the underlying substrate. The solution may not be does complete "stop", as a with Si3N4 thin film on SiO2 etched with H3PO4 where the oxide etches at a much slower an effectively working an etch-stop. See Oxide Etch; Selective Etch; Layer Etch. rate, as ETCH STRAIN 221. Stress Etch. Terms often used Similar combination as stress and strain studies. to in bending of a thin material, such as a semiconductor wafer, will develop dislocations The to Such due defects have been studied as both a positive (4-) or negative (-) strain strain. relative to <110> (lll)A or (TTT)B faces, and direction directions. See Stress Etch. (100), STRESS 222. ETCH preferential solution used to develop stress A in a material. Stress may be from figures normal wear-and-tear; induced by heat treatment; physically induced by tension, compression or torque or without heat. The latter method used in material studies. See Strain Etch. with STRONG ETCH 223. diluted term to the use of concentrated acids or alkalies, as A a applied general against or solution using weak a solution, acids. STRUCTURE ETCH 224. solution used to develop physical structure whether it is a defect in the material, Any selectively pit, a mesa, channel or the shaping of a solid. See Defect Etch; Mesa etched Dislocation Fault Sphere Shaping Etch; Channel Etch; Stacking Etch; Etch; Selective Etch; Groove Etch; Etch. SUBTRACTIVE ETCH 225. thin applies the selective Term of multiple to film layers. The removal of one etching layer without affecting others. See Stop Etch; Selective Etch; RIE Etch. 226. SWAB ETCH stick. of plastic foam type material on a or Medical Q-tips are used and, in Use cotton State processing, the cotton has been Solid with plastic foam to prevent reaction replaced from glue used to attach the cotton. Used the acetone for cleaning photo resist lacquers with from surfaces. In processing metallographic specimens, swab etching is a common term and solutions method surface structure. Some metallographic etching used on irons, steels, of and copper in the Etchant Section, Chapter 2 show TIME as "swab", when shown for "time" the referenced article. in 227. SWIRL ETCH Any solution used with a rotating motion. See Stir Etch; Agitation Etch; Angle Etch. © 1991 by CRC Press LLC

80 67 228. ETCH TEMPERATURE of cleaning etching solutions vary with solution mixture, application Temperature or may be a solid, liquid, or gas. May also refer to the use of temperature, requirements, and as (heat/thermal) vacuum agent, under a or furnace conditions. Much WCE alone, as etch exothermic, done temperature, but many solutions are room thus heating the is etching at the etching period. To control such reactions, water or solvent cooling coils solution during water bath holding the etch solution vessel have been designed to limit such surround a for And a major control factor can be particular etch mix rise. temperature temperature at room temperature (RT) a 1HF:8HNO3 solution is a good tures etch ... but ... polish 8°C preferential . . . and at 50°C too becomes and erratic for control. See the at rapid section discussion on TEMP previous Etchant Formats for a description of the various in levels temperature as used in this book. of THERMAL ETCH 229. (2) been (1) the use of heat in vacuum; as the use of heat in furnaces Term applied has gas atmosphere. In the latter with also called heat treatment (metals), and annealing a case, State), both terms have been used in though material processing areas. Pure heat (Solid all can develop etch figures or structures on alone See Heat Etch; Heat-Tint Etch. surfaces. 230. ETCH THIMBLE solution. cup used to hold an etch vessel Specifically referenced to using Any shaped ceramic, high temperature metal (platinum), or graphite crucibles to contain small, highly reactive, chemicals or liquid metals, such as KOH pellets at 360°C hot dislocation etching for of silicon wafers. See Cup Etch; Beaker Etch. 231. THINNING ETCH Any solution to reduce thickness of a specimen. Widely used with reference to used specimens for electron microscopy (TEM) studies. preparing transmission ETCH 232. TRIM part, to thickness, width, or length etch a reduce specimen, or device by used Any of only. This small include laser trimming, such as in fine-tuning paired diode increments, can for matching parameters. See electrical Etch; Thinning Etch. devices Sizing TUMBLE ETCH 233. closed-end called — A a "tumbler" — has long been used to polish rock and cylinder abrasive, specimens, surface cleaning of parts. Dry for a wet slurry or acid-slurry mineral or is added to specimens, then the tumbler abrasive horizontally on a set of parallel rotated bars. can be with a hand-operated Rotation but today tumblers are electrically operated. crank For parts clean/etch cycles, time is in minutes; whereas gem stone polishing is in days. Specimens and can be tumble etched in a beaker with the solution being stirred and parts Agitation floating Spin Etch; Bottle Etch; See Etch. parts free. ULTRASONIC ETCH 234. solution used with an ultrasonic generator to Any agitation during an etching develop or cleaning There are small cup to period. large basin-type systems. The latter include very vapor degreasing systems. The cup types are used for cleaning and etching small parts with solution. an seated in a water bath that transmits the vibration frequency to the beaker etch Most are fixed frequency, but variable systems units are available. A barium frequency titanate, Ba2TiO3, transducer is used to translate physical motion of the titanate into electrical blanks. frequency, like piezoelectric quartz crystal radio frequency much See Vapor De- greaser Etch; Vibration Etch. © 1991 by CRC Press LLC

81 68 CRC of Metal Etchants Handbook USED ETCH 235. applied for more than one period of time. In high volume processing where Any solution are batch at one time, large volumes of etch solutions are used to sustain several parts etched constituent good and ensure without repetitive, temperature in solution action depletion, each having replenish with fresh solution after without etch period. In etching dependent to the plating baths are automatically monitored, and additional solution added metal plating, plating rate to a pre-set level. See Cyclic Etch; Aged Etch; Stagnant Etch. when reduces ETCH VACUUM 236. of pure vacuum to effect etching action by varying the vapor pressure. This use The and been to preferentially etch single crystal gases grown under cryogenic has method used conditions in vacuum. pressure 237. VAPOR DEGREASING ETCH degreasing has wide Vapor in cleaning parts with a combination of hot liquid, hot use spray, a hot vapor head in which parts are held. In the large systems, the hot liquid and may include ultrasonic transducer. Size ranges from a beaker on a hot plate to large tank an held with crane hoist. Parts are lowered and overhead in the hot vapor head until tanks an are deemed clean; they are then slowly removed and are found clean and dry. Although they (TCE), trichloroethylene (DCE, Perk), or trichloroethane (TCA) have been dichloroethylene as in Freon solvents are being used past, replacements due to the carcinogenic used the of chlorinated solvents. See Vapor nature Etch. 238. ETCH VAPOR an solution in vapor form Any effect used etching or cleaning action. HNO3, H2O, to and H2O2 are all used to oxidize a surface, then the oxide stripped with HF as one method of surface In epitaxy system, hot HC1 vapor is used to clean the quartz tube walls, cleaning. susceptor carrier in some cases, the material surface about to be deposited upon. the and, Etch; Degreasing Etch; Vapor Atmosphere Etch. See Corrosion HOLE VIA ETCH 239. in semiconductor processing Specialized a crystallographically orient hole term where selectively etched through a wafer. The side walls of the hole are then metallized through is top from bottom surface, often referred to as wrap-around plating for an electrical ground to See Etch. plane. Selective 240. VIBRATION ETCH form of vibration used in conjunction with an etching or Any solution. The cleaning two common systems are an ultrasonic most or a shaker table. Vibration alone transducer is a standard assembly test vehicle, and can cause part or assembly failure. Such vibration tests include and g-force generators with an x,y,z spin component. acceleration/deceleration, WASH ETCH 241. a reference the pouring of a Used across to surface. Not widely used for with solution as it tends to cause surface etching, Standard water quenching of parts after channelling. etching sometimes referred to as "wash" clean, but is not an actual etching method. is 242. WATER ETCH Though water is considered neutral, with pH 7, the major liquid used for quenching an act etch for general washing and rinsing, it can and as an acid etch on water soluble solution, compounds. Such compounds can be polished, preferential etched, or selective etched with compound water Sodium chloride, NaCl, is one such only. that is widely used as a (100) © 1991 by CRC Press LLC

82 69 oriented for thin film metal evaporation and epitaxy growth in morphological studies substrate thin films by the float-off technique for TEM observation. with removed water, High as brine and atmospheric moisture, will slowly corrode many as purity well materials alloys. industry uses coupons of new metal in corrosion tests by and metals The salt atmosphere along seacoasts, and study irons and steels by dripping exposure to high water surfaces over extended periods of time. purity onto or study ice, it is grown as single crystals and the is used to polish of preferential In water surfaces. Brine Etch; Atmosphere See etch Etch. WEAK ETCH 243. use of a highly diluted etch mixture or a singular The such as ammonium liquid, hydroxide, and ammonia, NH3, which are both weak bases. NH4OH WET CHEMICAL (WCE) 244. ETCHING the effect major divisions in chemical etching. It is the use of any liquid to of One three method or and still the most widely used action of etching. See Liquid cleaning etching Etch. WHITE ETCH 245. term applied been The to mixtures of HF:HNO3 with or without HAc/H2O. It is not has as not solutions are clear and transparent, recommended, an opaque white. See Named these Etch. 246. DAMAGE ETCH WORK sub-surface polish used Any remove residual etch damage remaining after cutting to and mechanical lap and polish in preparing a wafer or similar specimen. The bro- mine:methanol (Br2:MeOH) BRM solutions are currently used on many metals and metallic or for this as they not only remove such damage, but act as slow polishing compounds purpose, solutions. 247. X-RAY ETCH both are photographic technique X-rays in a medicine and material studies, Though used as well as other particles, have been used in material surface studies. Fluorite, X-rays, CaF2, will color changes when subjected to X-rays, such that here it is referred to as a show of irradiation Radiation or method using ionized gases or atomic particles can etching. cause similar in material, as well as produce internal, bulk damage. Again, not a effects true etching phenomenon, but of major importance in material processing. All space hardware is subjected radiation evaluation as one high reliability test, and X-ray may be included. to YELLOW ETCH 248. ROOM solution used in a Yellow Room for the processing of material by Any photolithographic techniques. resist lacquers are affected by Photo to white light, such that all exposure processing is done under yellow light with humidity controlled at 40% ± 5 RH, and much temperature for optimum results. Too 70—72°F humidity and photo resist between will not harden properly; whereas too low a humidity, the lacquer will harden too rapidly cure and If the temperature approaches 80°F, the resist also will not crack. or harden properly even under controlled oven bake out conditions. © 1991 by CRC Press LLC

83 70 CRC of Metal Etchants Handbook ETCHANTS NAMED past it used to be fairly common practice to assign a name or number to an etching In the it was often the developer's name, or a number associated, for solution when developed, mixture so a company, and the forth. Some approaches used example, with components, under the of Etching section Methods ''Named Etches". discussed are in E407-70 pamphlet, as originally assembled and published, is a list of The ASTM for industries commercial metals developed — copper, iron, steel, aluminum, solutions the number, alloys with both a name and assigned many such as Nital (HNO3:EOH), their — and — Fry's Reagent, ASTM #79, etc. The ASTM does not assign solutions #74 pamphlet specific as does this book, but where the metals has been used in Solid State for solution and known to be from the pamphlet, it is referenced by ASTM development in number addition our assigned metal-associated number. to Buehler Ltd Metals Digest series is another excellent source. Although each The AIB mainly individualistic, equipment and metal processing cover with regard to is they booklet of specimens, and include geologic mineral metallographic to some study cross-sections Several the booklets include excellent photographs, of include data on the solution degree. to to develop micro- and macro-structure of the specimen shown. Many of their solutions used are the used ASTM pamphlet, but also include solutions developed by the Buehler from organization. — Handbook Series — some ten books Metals cover all aspects of industrial The ASM processing, fairly comprehensive from aluminum to zirconium. Volume 2 is, in metal large part, etching and cleaning book of the series as applied to large the commercial volume processing. of general metals processing Much surface preparation solutions, elec includes trolytic etching, thermal heat treatment, and plating solutions. For plating, which is not covered to extent in this book: Lowenheim, FA — Modern Electroplating, sponsored any the Electrochemical (John Wiley & Sons, publisher) is an excellent reference. by Society Solid and have been developed in the solutions State area of cleaning etching Many was an initiating technology in the which 1940s. In some instances semiconductors late have carried over from the general been industries, but many others have solutions metals formulated with particular regard to single crystal been and today all of the technology associated structures (colloidal, amorphous, crystalline), as well as associated met physical solutions ceramics, other compounds. Again, several and have been named by als, glasses, developer, such as the Camp #1, #2, #3, #4, etc. their As a common usage series. acronym, Camp #4, as an example, is the known as CP4 or CP4A (without bromine). best Preferential defect solutions containing chromium salts have largely been named for their developers: Sirtl among the first, then Sopori, Schimmel, Wright, and so forth. And Etch etch). is known WAg etch (Westinghouse Silver well Two other solution types there the mention: the bromine:methyl alcohol (BRM), and buffered hydrofluoric acid (BHF) bear range Both in series. current use referred to by their acronyms, but have a wide are wide of mixtures. BRM solutions below 5% component are polish types; above, can be BR2 preferential. A more or less standard BHF mixture is 1HF:1NH4F (40%), but even dilute NaF, HF referred to as a BHF solution, or a mixture may contain been KF, yet all are has still called BHF as a general acronym. The following list includes most of the named and/or numbered solutions as discussed by and in the Etchant Section, Chapter 2 accompanied applied the assigned Etchant Numbers for referencing purposes. © 1991 by CRC Press LLC

84 71 name Etchant Material references etch "A" NACL-0007e; LIF-OOlOa; TA-0003a A-B or A/B etch GASB-0014c; INAS-0005d; GAS-0059; INP-0051 modified A/B, INP-0021d AB etch) (RCA etch SIO-0043 etch Allen's INSB-OOOld regia Aqua WB-OOOlb; ALAU-0002; CDSE-0005b; CAW-OOOb; CDTE-0018b; CUIS-0003; GAS-0056a; GA-0002; AU- GAP-0011; IR-0001; MO-0008a; PMA-OOOla; 0001; PD-0001; OS-OOOlb; QTZ- PT-0001; 0003; RU-0001; SIO-0052; SIN-0016; SN- TAN-0001; TE-0002; TH-0002; TIO-0004; TIW-0006; W-OOOld; 0005b; ZHPD- V-0002a; ZNTE-0005b; ZR-0007; 0001;ZRRH-0001 Aqua regia, dilute GAS-0044c; PD- NICR-0003; AU-0005; TE-0008 PTSB-0001; 0002b; Aqua regia, modified NI-0005 GAS-0056b; GAP-0022e; etch Barber NACL-0007b BCK-111 INP-0031a BHF SI-0023; SI- SI-0021a; SI-0020; SI-0022; 0028; SIO-0009; SIO-0013; SlO-OOlla; SIN-0008a; SIN-0009; SIO-0071; TIN- 0003; SIC-OOlOe modified BHF, SIN-0008b; SIN-0014; SIN-0023 dip finish Bichromate CU-0008c BRA-0008b; etch Billig's GE-0139b BJ etch GE-0027 BOE (BHF) SIO-0017; SIN-0006 BPK-221 INP-0031b Brilliant etch CU-OOlla BRA-0008d Bright dip dip Brite CU-0028; AL-0013; CUO-0005 BRM CDTE-0008; ALAS-0001; CDTE-0017b; CUIS-OOOlb; GAS-0006; GAS-OOOla; GE- GAS-0173b; GAP-0009; GAP-0006; 0038; INAS- INSB-0022J; INSB-0028; INP-0001; INP-0006; INP-0009; 0002; FE-0100; INP-0062c; FE-0102; FE-0113; SI-0001 MN-0002, SIC-0005b; (for arsenic) Bromine etch AS-0002b BSG SIO-0048 (Superoxol, #2 Camp CP2) SI-0165 GE-0065a; (CP3) #3 Camp GE-0065b CP4) #4 Camp (See (See Camp CP8) #8 Caro's etch GAS-0125; SI-0103; SI-0169b CR-0006; CRO-0002; CRO-0004; CRO- etch Chrome 0005 © 1991 by CRC Press LLC

85 CRC 72 of Metal Etchants Handbook etch, modified CR-0016 CR-0015; Chrome SI-0038a Chrome dislocation etch Chrome regia SIN-0018 SI-0019; AU-0017; NACL-0007c Cook's etch etch Copper SI-0153d SI-0153c; dislocation etch Copper SI-0038b (Camp CP4 #4) INSB-OOOlf; GE-0065c; AU-0016; INAS- SI-0173; 0009; TE-0005; SIGE-0001; ZNO-0004 dilute CP4, INSB-0021 GE-0201b; modified CP4, INSB- SB-OOOlh; SB-OOOlg; GE-0219; INAS-0003; 0006f; LIF-OOOla; TE-0003; INAS-0006d variety CP4, SI-0055 INSB-0021; CP4A INSB-0029; GE-0063; INSB-0022c; FEGE- 0002; SI-0102d CP8 SI-0062 Dash etch SI-0046 SB-OOOla; etch, Dash modified SB-OOOle; SB-OOOld; SB-OOOlb; SB- SI-0153b; SI-0046a; OOOlf; SI-0154a DE-100 GE-0047; SIO-0023 etch decoration Dash copper SI-0154a EEtch ZN-0008d CDTE-0006a; EAgl CDTE-0006b EAg2 CDTE-0006c EDTA CA-0003b etch Erhard's SI-0158 Ellis #1 GE-0150q; GE-0060c #5 EUis GE-0150o Ellis #7 GE-0150r INSB-0014a Etch#l #2 Etch INSB-0014b Ferric cyanide etch GE-0150s; GE-0060d BE-0004b etch Freeze Fry's reagent FE-0112;FESI-0008 Flick's etch AL-0017 General etch CU-OOllb etch cleaner Glass SIN-0015 Gold etch silicon) (on SI-0064 SI-0018 Glyceregia Hetch INP-0051 INP-0021c; etch Healy's junction SI-0069 Hypo AGCL-0007a 100 H INSB-0022f Iodate etch PBTE-0002a etch Iodine GE-0205; AL-0031; GE-0218; GE-0137c; SI-0240; PBTE-0002b; SI-0242a FE-0109; Iodine GE-0185 A Jacquet's etch AL-0048; BRA-0014 Jewitt-Wise etch NI-0004a {Calling's etch ST-OOOlb; YXM-0001 etch Keller's AL-0023 © 1991 by CRC Press LLC

86 73 KKI INP-0062d Krum etch AL-0011 Landyren's etch SI-0102f Matte dip BRA-0008c Moly etch MO-0015 reagent Murakami's MO-0005b; TAC-0001; TIC-0005; WC- 0001 Nital FE-0102; FE-0113; AL-0022b; AL-0027; FECV-0001; FENI-0001; ST-0001; ST- 0009c; ST-OOlOb FESI-0005b Nital, variety etch "0"°C GAS-0030b BRA-0008e etch Pickling CDTE-0006d; Petch SlO-OOOlb ZN-0008a P-l ZN-0008b P-2 ZN-0008C P-3 CDTE-0006e PBr P-ED (EPW) SI-0119 SI-0116; GE-0060f germanium) Peroxide etch (on ST-0009e; ST-OOOlg; Picral ST-OOOlc; FE-0106b; ST-OOlOb SIO-0021b Pliskin etch (A-B) etch RCA QTZ-0012; SAP-0004a; SI-0031 RC-1 GAS-0048 BRA-0008a Scale dip GAS-0044 Schell etch SI-0037 Schimmel etch Schimmel, modified SI-0038 etch SI-0036 Secco SI-0152 Secco, modified etch SI-0209 Silver (for silicon) etch glycol Silver SI-0041a Sirtl etch SIC-0012a SI-0039; Sirtl, SI-0132 modified SI-0153a; etch Sopori SI-0043 SIU-0044 modified Sopori, #2) (Camp Superoxol GAS-0167a; GE-0002; GE-0005; GE- INAS- INSB-0024a; GE-0202; 0150i; 0006b modified Superoxol, GE-0150j-n INP-0022a; GE-0124; SR4 SI-0172 GAS-0101 SSA etch Tri-iodide CD-0005; AU-0007; AU-0021; AUSN- 0001; AUGE-0001; AUGA-0001; AUZN- 0001 ST-OOOle Vilellas etch SI-0034 Vogel's etch NACL-0007d LIF-OOlOb; etch "W" GE-0150p; GE-0060c WAg ZNTE-0002a reagent Warekois' © 1991 by CRC Press LLC

87 74 CRC of Meted Etchants Handbook etch GE-0015b; SI-0056; SI-0057; GE-0190 White Wright etch SI-0045 !.!•* GAS-0037a; GE-0028; SI-0020 X-1114etch GE-0147d (100) etch GE-0060e © 1991 by CRC Press LLC

88 75 Chapter 2 SECTION ETCHANT Appendix C (Metals and Metallic Compounds with Reference Acronyms) for Refer to list the materials in this chapter. We have made no attempt to categorize of alphabetic all by types: or type format — three etchants (1) Wet Chemical Etching, formats or chemicals most Chemical (3) Electrolytic Etching as in and instances there is only Dry (2) Etching, a half-dozen referenced and formated etchants on any particular one to material. are such as for aluminum, gallium arsenide, germanium, indium There exceptions, extensive silicon, number of specific etchants is the (silicon has over and where antimonide, items). In this case, a Selection 450 has been included following the general referenced Index which chemical formulas, solution applications, lists the material format introduction and numbers. certain elements such as chlorine, fluorine, sulfur, or phosphorus are widely used Where in etchant a section titled: "Etchants Containing xxxx" precedes the for formulations ... an selection of etch formulas — material — application — format reference mats A—Z is regard quick reference for those interested in associative reactions with This number. a thin This or composite constructions. multilayer includes some special groups, such to film (BHF) regia, buffered hydrofluoric acid the solutions, bromine:methanol (BRM) as aqua or silver and chromium mixtures that are specifically preferential category, character. in Some and trinary compounds follow their parent element without a general binary been and natural minerals are shown where they have few specifically involved introduction, a Solid State development. in list of solutions is far from The but it will give the user at least a starting complete, place immediate application or further for to included additional data obtainable development from the referenced article accompanying each etchant format. ADHESION General: natural minerals contain thin films of alteration products on their surfaces Many grow as on dissimilar minerals as a surface coating. Magmatic intrusion and or incrustations mineralized form into cracks of solidified rock formations of solid veins percolation waters fine introduced if vug or void, can form into crystals as an encrustation within the and, a "dinosaur eggs" are silica, SiO2 are concretionary segregates found in compressed void: rocks be they may sedimentary a solid multicolored agate — or contain fine single crystals — citron, clear tinted as purple amethyst, yellow occasionally etc. as an incrustation of quartz, in the hollow concretion. growth encrustations of vein-type deposits are All geologic interest in the study of mineral and regard rock but are of little concern with and to adhesion, other than in separation formation, of gangue materials, such as in metal ore processing. Layer adhesion is of importance in making jewelry, layer separation during fabrication can destroy the item. Moonstones, as "dinosaur one similar in many respects to the are eggs" in formation, but are as example, colloidal to amorphous in internal structure solid a hard white outer coating of mag with nesium calcium sulfate with extremely good and With the coating removed by adhesion. etching, the moonstone cut and polished, it shows fine light halos due to its noncrystalline structure. Technical Thin film adhesion is of major concern in all material Application: processing, regardless the method of deposition: of evaporation, epitaxy growth, electrolytic vacuum plating, to include all phases of subsequent processing, temperature effects, in particular. singly, In State processing most of the metal elements have been deposited, Solid as compounds, multilayers metallization; as metallic of with or without subsequent recrystal- © 1991 by CRC Press LLC

89 76 CRC of Metal Etchants Handbook (silicides); or oxides, nitrides, carbides, and borides. Many have been studied lization as as for and similar structure of thin films. In both adhesion and single adhesion crystals film or reactions, studies substrate may be removed for thin interface physical properties the by SEM or TEM. study microscope few direct studies of Only are shown here, but many are mentioned in the a adhesion discussion throughout this chapter under the specific metals and metallic format sections involved. compounds with material and type adhesion Varies involved. Etching: test ETCHANTS ADHESION AD-0001 NAME: van der ETCH TIME: Graaf TYPE: conditioning TEMP: Particle, POWER: 1013—1019 COMPOSITION: cm3 electron 1—5 MeV ... or x cm"2 DISCUSSION: and Ag thin films Au, on different substrates in a study of adhesion and Pd, deposited effects of van der Graaf power and ionic species impingement on the metal surfaces. the thicknesses Film 500 A, and electrons applied were He+, Cl+, H+, and F+, and used were different were combinations. Substrates on Teflon, SiO2, CaF2, A12O3. Si, metal/substrate were GaAs, and ferrite. The silver/silicon samples InP, processed after van der Graaf W, treatment as follows: (1) remove silver with HNO3, (2) rough thin silicon with HF:HNO3, (3) final with CP4A. Adhesion was generally improved by about 30%, with center thin of films thinner relative to the flux dose level. After electron treament all films areas being standard tape test. passed the the was in order thinning observe done metal/substrate interface by microscope Etch to (Note: CP4A is 3HF:5HNO3:3HAc.) examination. Werner, al T et REF: — Thin Solid Films, 104,163(1983) B PROPERTIES AIR, N2/O2 + TRACE GASES PHYSICAL OF Classification Gas numbers 7 & 16 Atomic weight (nominal) Atomic 58 point (°C — solid) >200 atms Melting 200 (variable) - Boiling point (°C — liquid) -180 (variable) Density (g/cm3) 22°C (dry) 137 Hardness (Mohs scratch) solid 1—2 — structure (isometric normal) (100) cube Crystal — Colorless Color (gas) (liquid/solid) Bluish (cubic — solid) Cleavage (001) AIR, gaseous The atmosphere refers to General: term envelop of aeriform fluid that the surrounds the earth and commonly called air. It is a mixture of gases not a compound, in containing 78% nitrogen with trace rare gases oxygen, addition to dust particles and 21% water vapor. Dust and water content vary seasonally and with locale, as do other compounds. combine Volcanic release chlorine and sulfur which areas as hydrochloric acid, HC1 and © 1991 by CRC Press LLC

90 77 sulfuric H2SO4 or hydrogen sulfide, H2S; industrial areas release a variety of contam acid, now called though "smog" has been associated with the cities of man inants, "smog", times, since back as 4000 B.C. Decaying vegetation releases ammonia, NH3; as ancient far night gas, it is "foxfire" seen burning at — — man and the methane CH4 swamps produce dioxide, CO2, as they breath and utilize the animals in the air; whereas release carbon oxygen the and release oxygen, O2 . . . CO2 symbiotic ecology. The jungle areas of use plants a River in Africa, and the Amazon River in South America are major sources the Congo for and, the deforestation of the Amazon basin for farming, there may be a major oxygen with the shift in the atmosphere. O2/CO2 in cycle The and not clear to have weight. does standard measurement is 760 is Air appear 0°C, as measured in a tube mmHg 30" in height and 8 cm in diameter. This weight at about approximately pounds per square inch (psi) for a IS pressure on the human body of is total 18 tons. This is called 1 atmosphere (atm) of pressure, and the some of pressure amount reduces increased height above sea level as the air envelope thins out to the vacuum with space. At pressure water boils at 1QO°C; at 720 mmHg it boils at 98.72°C. At of standard feet Mount Blanc water boils at 85°C. 17,000 on about temperatures it is a clear gas, but as a liquid (— 180°C) At solid (~200°C), normal or has pale bluish color tint. The pressure liquefaction a fractionation of air is a major it and for the fabrication of liquid air, Lair (- 180°C) — liquid oxygen, LOX (- 183°C), industry liquid 195°C). LN2 (- and All of the gases have been grown in solid form, to nitrogen, single crystal for morphological study, e.g., helium excepted. include structure only in air vapor of critical importance, not the for the seasonal planting and Water is of crops, but today, the weather patterns of harvesting atmosphere are of vital concern the to traffic control and space vehicle launching. Wind-shear has been responsible for aircraft shuttle several the explosion of the Challenger crashes; has been attributed, in part, airplane to freezing temperatures at launch time; and a satellite launch into a rainstorm was destroyed by lightning Relative humidity (RH) is the measure of water vapor content in the strikes. (100% = saturation). The higher the temperature and humidity the more air maximum to human it reduces the perspiration ability as cool the body. The for uncomfortable beings, zone is 70—72°F temperature with humidity between 45—60%. Very most comfortable for 10% humidity, in desert areas, can cause dehydration; in Arctic areas such low example, can humidity, the land is covered with ice, though cause severe frostbite and even low even from breathing . . . dry, freezing, dehydrated air. Temperature, humidity, death par- and ticulate of air can be critical in industrial processes, such as electronic assemblies content Rooms" semiconductor The construction of "Clean fabrication. has become a and device industry itself, using air conditioning and filtration control for a nominal 70°F, 45% major and in than 10% paniculate content RH, the air . . . the particulates measured in micron less of A piece of dust landing at a critical point size. a device structure can destroy the single functional capability. With the beginning development of man's metal culture in the Bronze Age — somewhere around 5000 — we started using air as an industrial application: smelting of ores and B.C. when of Iron Age began about 1350 B.C. The the Hittites of Asia Minor fabrication bronze. iron smelting — requiring higher temperatures than bronze, leading to the use of developed The had bellows. already developed kiln firing and soda-lime glass (around 3000 Egyptians same initially B.C.) a glaze on pottery, and the used formula is still in use for ordinary as glass. Iron tools may have been in use by the Egyptians about this same time. Sailing ships been major power bases in the Mediterranean Sea for centuries as have and (Crete, civilizations rose and fell trading Egypt, Greece, Phoenicia, Roma). ruling 1800s sailing power culminated in the mid- Wooden when the British Empire ruled the ship oceans of the world after Spain, Portugal, Holland, and France. Great Britain was the major controlling sea after the defeat of the Spanish Armada in 1588 until after World War I, power years. much the world for over 250 of Even today, large diesel-powered transport ships © 1991 by CRC Press LLC

91 78 CRC of Metal Etchants Handbook had metal added to increase speed; fishing fleets still use both sail as well as have sails sailing engines; worldwide industry. Sailing ... the world still uses wind power is sport a purpose. for this There range of air sports: the Chinese developed the flying of kites in ancient a wide is developed and balloons French were racing across Paris in the mid- 1800s; times; the hot-air — Germany the first lighter-than-air dirigibles invented they were used Zeppelin Count in in World War I and culminated as a transport airship with the against England unfortunate the at Lakehurst, NJ in 1936. A few are still in use today, using burning of Hindenburg an than lift — the Goodyear blimps as for example — and are under rather helium hydrogen for heavy transport of materials. consideration again wings always to has It goes back to the legend of Icarius with his wax wanted Man fly. the dynastic period around 1300 B.C. The Cretian brothers are credited with during Wright and flying the first fixed-wing air machine — the airplane — in the early 1900s, designing though similar was being made in Europe in the late 1800s. Small, open- development biplanes and were used in World War I — the Americans as the U.S. cockpit monoplanes the Force become a separate branch of not military services until shortly Air Army (did War II). These small planes were used for barnstorming around the U.S. in before World and 1920s the first airmail delivery in the 1930s, and the "clipper ship" flying- 1930s, the as crossing Pacific to the Philippines the early as 193S. were boats were used in the American Civil War, and World Balloons I and II, mainly for Wars reconnaissance and today weather balloons are an element in weather fore observation, height Ballooning sport is still in existence, both for a — over 13 miles in 1935 casting. as 15 miles in 1988 — and flown for cross-country distance flying, to include attempts — to cross Atlantic Ocean. The Japanese sent incendiary balloons across the Pacific during the 555 War into the American northwest — the World PIR were used as smoke jumpers — II the only black parachute unit at that time. The use of parachutes was first envisioned in Italy in 1400s, were used for free-fall jumping during the airplane barnstorming days, the the Germans the first massed airborne parachute troops in the invasion of Holland but used Kurt German under the command of General Division, Student. The largest 1st Airborne — was by the Allies when they jumped into Holland airborne September of 1945. drop in of 82nd Airborne Division jumped in Korea, and the Airborne Division Elements 101st were in Vietnam. elements has become a civilian sport, as well as being used by the military for small Skydiving drops, designs new parachute unit are under continual development. and development of aircraft in the 1930s culminated with their use in World War The large probably Douglas — the military C-47 — is The one of the best known transport n. DC-6 and many are still in service aircraft, The B-24 and British Halifax bombers; Germany today. Messerschmitt. British Spitfire . . . American P-51, P-38, P-47, or the Navy Corsairs, . . Zero, fighter and, not the least, the Japanese as to mention only a few. The Germans aircraft, developed the first jet aircraft toward the end of World War II, and this has led to the present-day military commercial jet aircraft that have tied much transportation of the and together hours/days rather than months. world in helicopter bears mention as an aircraft in its own right. This did not become a The aircraft 1940s, the late viable and the first real service (which was military) was in until Vietnam Korea evacuation. By the time of the medical war there were wings of transport for and attack helicopters. Have you ever heard of "Puff... the Magic Dragon"? It was a helicopter built a flying gun platform, capable of decimating some 100 square yard of as concentrated area time with a single burst of a fire-power. Military branches of all countries at today have both transport and attack helicopters, and there are civilian general transport and construction as well as medical-evacuation choppers. helicopters, As a source of mechanical power, windmills have been used in Holland for centuries, in and designs were brought to the Americas several the 17th and 18th centuries. Single © 1991 by CRC Press LLC

92 79 and sets of wind vanes are now in use for production of electricity using wind multiple as an energy source. power alternate are Wind evaluating air turbulence in aircraft wing and body design, used tunnels in large vehicles to simulate freefall in space, and air-lift used are under astronauts have fans evaluation. and development such in many industrial operations, Air as for air cylinders or supply air compressors and valves. They supply the for in gas stations for filling tires, and pressurized switches air for cleaning in metal workshops, etc. There are now back-pack units and vehicle air general for maintenance. cleaning or yard systems Pressurized air is used for materials mounted street should under testing. CAUTION: Air compressors pressure be well maintained and devices prevent oil from the compressor pumps leaking into air lines and contaminating parts to cleaned or under test. being Application: Air, as a gas and as liquid, has many applications in metal Technical both State conversion Liquid air is mainly used for Solid to gaseous, pure air and processing. and use oxidizing atmosphere or for surface cleaning an drying. Air drying can be for as allowing a part to dry in the room atmosphere at room temperature; on a hot plate; simply an in oven at elevated temperature; or under IR lamps. It can be supplied air-circulating of pressure sinks for "blow-off" drying chemical parts. Where dangerous chemical under in are in use, such as in epitaxy equipment areas, gases combination of air-conditioning and a exhaust are designed to completely evacuate and fans the room volume of air in 1 replace min in the event of a gas leak. Dry air is supplied in pressurized cylinders alone, or as a gas mixture special applications (A-l cylinders at 3600 psi — 9" diameter, 5 ft high for a two-stage It also is supplied as wet-air for high purity steam oxidation. with regulator). belt of operation a nitrogen curtain (a series hydrogen glass cloth hangers at front In furnace curtain with gas blown down into the nitrogen zone) are used to prevent and end entrance entering the hot furnace, mixing with hydrogen and exploding. air samples polishing Metallographic are heated in air on a hot plate for' 'color tinting"'. after as resulting vary with the metal mixtures colors the crystallites have different The oxidation that oxidize at different rates with varying distinctive orientations Where it is a single colors. crystal with different phases, the phases can metal differentiated by color in a similar be manner. When a metal thin film has a preferred deposit orientation there will be a difference in color: is an example, (1010) surfaces are brilliant reds/blues; whereas (0001) Titanium good are basal (0001) surface gives The adhesion; the (1010) surfaces tan/yellow-brown. plane tends to peel. Air is supplied by prism for operation of valves and compressors equipment, to hoses for heavy duty or cleaning or pressure testing of parts. air As a gas mixture air is not grown as a single crystal, although oxygen, nitrogen, and the rare have been grown under vacuum cryogenic and pressure conditions for mor gases study. phological N/A Etching: ETCHANTS AIR AIR-0001 NAME: Pressure TIME: ETCH TYPE: preferential TEMP: - 196°C Pressure, COMPOSITION: x ... pressure, vapor DICUSSION: N2/O2 as a single crystal in grown under pressure and cryogenic conditions is vacuum difficult to grow because of the difference in vapor pressure between oxygen and nitrogen. © 1991 by CRC Press LLC

93 80 CRC of Metal Etchants Handbook vapor under can develop etch figures and defects on surfaces of Varying pressure vacuum the solid. Academic REF: — Rare Gas Solids, Vol 3, N Press, New York, 1971 Schwentner, et al OF PROPERTIES PHYSICAL Al ALUMINUM, Classification Metal number Atomic 13 Atomic weight 30 Melting (°C) point 660 Boiling point (°C) 2467 Density (g/cm3) 2.699 Thermal 20°C (cal/sec)(cm2)(°C/cm) conductance 0.50 25°C Specific heat (cal/g) 0.215 heat of fusion (cal/g) Latent 94.5 Heat fusion (k-cal/g-atom) of 2.55 vaporization of (k-cal/g-atom) Heat 69.9 Atomic volume (W/D) 10.0 1st ionization energy (K-cal/g-mole) 138 potential (eV) ionization 1st 5.98 (Paulings) Electronegativity 1.5 (angstroms) radius Covalent 1.18 Ionic (angstroms) radius (Al+3) 0.51 of linear thermal Coefficient expansion .22.4 (23.9) (xl0-6cm/cm/°C)20oC resistivity (micro-ohms-cm) Electrical 2.655 Cross section (barns) 0.215 (0.23) 10~6) Magnetic susceptibility (cgs 0.6 x Tensile (psi) 30,000 strength Vapor pressure (°C) 1749 2—2.9 — (Mohs Hardness scratch) — (Knoop kgf/mm~2) 100—140 structure normal) — (isometric Crystal (100) cube, fee (solid) Color Silver white (001) (cubic) Cleavage Al ALUMINUM, but Aluminum not occur as a native General: does is found as a constituent in element, over 200 single crystal minerals. In order, oxygen, silicon, and aluminum are the three most abundant elements the world, and the oxides SiO2 and A12O3 are the most inert and stable in normal atmospheric The mineral bauxite, A12O3.2H2O — a hydrated under conditions. often — oxide major ore. It is most is found in clay-like deposits called aluminum the as a mixture with clays and iron oxides, laterites may contain large amounts of a colloidal and form aluminum oxide. Bauxite's mode of origin is not completely understood, but it of is known form under tropical conditions from to prolonged weathering of aluminum bearing the rocks, and as a sedimentary colloidal precipitate which can be associated with volcanic activity. As mineral corundum it is mostly a constituent in rock forming minerals of the the of Group, can be an original constituent but igneous rocks and pegmatites. It is Chlorate not used as an ore of aluminum, but its three varieties are of commercial importance: (1) as gem (blue); ruby (red), and sapphire "Oriental" — topaz (yellow), emerald stones: (green), amethyst (purple); (2) corundum, as a powder for abrasives, and (3) emery, also © 1991 by CRC Press LLC

94 81 as admixture with magnetite, Fe3O4. When corundum is cut normal to the z-axis and an encabachon, it produce a six-rayed star — the star sapphire, with top quality polished may blue-grey. a fine is metal to gold in malleability, sixth in ductility, and one Pure second aluminum only only of = 2—3); whereas corundum is second (H to diamond in softest the of metals hardness and H = 10, respectively, on the Mohs Scale of hardness). The metal is (H = 9 color as is highly electropositive, when and, contact with other metals, in silver-white in rapidly. It has about 60% will the electrical carrying capacity of copper, and has corrode of used high power transmission lines as it is much lighter than copper. It also has been for in tend wire form for house current power and lighting, but the wire used to been finer time, to over 20 years with the oxide — a nonconductor and industrially say, oxidize aluminum high ceramic. The conversion of temperature to aluminum oxide a considered a high heat of formation which is strongly exothermic: Al + Fe2O3, when heated to has A12O3 form Fe produces 198,000 calories of heat (thermite), and used both for welding + as an Aluminum foil, when ignited in photoflash bulbs, produces heat equiv and explosive. with that sun surface (some 8000 K) the intense white light. to of alent the greatest use of aluminum is as a By metal. Physical strength is far construction with addition of small amounts of other the such that the majority of increased metals, 'aluminum9' materials are in some form of an alloy. As an example, duralumin — containing ' Mg, heat Mn — after Cu, treatment has the strength of mild steel and, when duralumin and are clad pure aluminum, becomes even more weather resistant to corrosion. sheets with engine airplane car and truck bodies; skins; blocks; building girders Applications include house siding; window and door frames, including the wire and screening; cooking mesh pots pans; as well as aluminum foil, and hundreds of small products, such as screws, and glass, rods, and so forth. Evaporated on tweezers, it is a low-cost replacement for bolts, silver mirrors, and evaporated or sprayed on glass or plastic as an anti-reflective (AR) coating. In baseball bats, water and snow skis, the frame for back-packs, and tennis sports: frames. Aluminum is either oil-base or plastic-base, e.g., acrylic spray paint. racket paint use plastics added as flakes for "glitter" with wide is in jewelry items. Military some it In dropping of thin aluminum foil to use radar and heat-seeking missiles; as includes confuse frames, as a constituent in both flares and incendiary bombs. In the clothing weapon and for some everyday wearing apparel but, more importantly, in the construction of industry retardant space chemical protective suiting and fire suits. There are medical applications and The compounds, the hydroxide, A1(OH)3 as a salve. as hydroxide also is used as a of such for setting dyes in the clothing industry, and as a clarifier in water treatment. Alums mordant double of — aluminum salts and sodium, potassium or ammonium salts — also sulfates important applications. and chemical have medical use the industry — clays In been in pottery since earliest times in the Middle East, have circa 12,000 B.C. — and, with the Egyptian development of soda-lime glass around 3500 B.C., the industry has become known as the ceramic pottery industry, e.g., the pottery of glass a surface glaze. Archaeologists date the rise and changes of ancient inclusion as pottery. the and pigments used on glazed designs, Note that many clays civilizations by alumina, such that the pottery industry includes aluminum contain but aluminum compounds, metal only been available in quantity since the discovery of the electrolytic method for has the ore within the past century. processing p-type Application: aluminum Technical is a Pure dopant in Solid State processing metal of silicon, and was used as wire or cut pre-forms, then as an evaporated thin film to fabricate the first diodes and transistors that led to development of the semiconductor industry silicon used in 1950s. The metal is still early on silicon and other compound semiconductors, the although aluminum chloride, A1C13, is used as a gaseous diffusant source. And today, an aluminum AlSi(2—5%) is more widely used as a pre-form than the pure metal as an alloy contact alloy Aluminum is evaporated as electrical device. pads on many devices, with © 1991 by CRC Press LLC

95 82 CRC of Metal Etchants Handbook wire ultrasonically to the pads. Ultrasonic vibration is used to break aluminum bonded thin native that always grows and stabilizes on aluminum metal surfaces through the oxide air. to exposed gold used in direct contact with should as with time and/or heat the Aluminum be not form distinctive purple compounds that are extremely brittle and destroy the two metals of an integrity device. The reaction is called "purple plague". Walker electrical operating recognized of a plague as a problem during a failure analysis first high power (author) purple several and Bernstein carried on the study with diode, excellent papers and reports, silicon L. 1960. circa aluminum and gold are used in a Where structure, they are separated by evaporated device layers other metals, such as Pd/Cr for a complete layer structure as Au/Pd/Cr/Al. Such of are not a vertical separation, but are horizontally off-step separated, as both gold layers only under can slow "creep" characteristics on a device surface aluminum operating and show particularly, at elevated temperature. load, chemical processing of thin film aluminum is a basic problem as, The pure when aluminum exposed to air, it forms a passivating, stable oxide layer on the surface, and is oxide most impervious to the liquid chemical processing solutions for controlled removal is microcrystalline patterning. aluminum deposits as a The layer, crystallite size controlled and to some degree by rate and temperature of evaporation, such that the ensuing oxide also is crystalline in Acid attack initiates along these oxide crystallite boundaries, un structure. the "oxide" a more rapidly attack of the underlying pure aluminum. This dercutting with the and recognizable "Swiss cheese" effect, produce remaining oxide on a surface can easily metals a resistance zone if other high are subsequently over-evaporated, reduce will create efficiency, and, in many cases, poor metal adhesion with electrical peeling and eventual loss metal contact. RIE — reactive ion etching — using an RF plasma with gas mixtures, of oxide, as or A1C13, are now such use for improved etch removal of the residual BC13 and in most structures are processed with aluminum gases in current device fabrication. these In quartz crystal radio frequency blank processing the evaporated metal electrodes are usually gold, or aluminum. Aluminum is given preference due to its lesser mass silver effect crystal frequency. loading on SELECTION GUIDE: Al Acetone: Note: Applies to lift-off of all thin film metallization deposited (1) photo on resist lacquers. Lift-off: (i) AL-0088 H2O: Note: Applies to (2) thin films deposited on soluble substrates, all (i) Float-off: AL-0095 (3) Br2:MeOH: (BRM) Removal/Polish: (i) AL-0082a (4) HC1, cone: (Electrolytic) Preferential: AL-0060; -0082b (i) ;-0098 (5) HCL:H2O (i) Removal: AL-0003b; -0004 (ii) Polish: AL-0034 (iii) Preferential: AL-0005 (6) HCl:FeCl3:H2O: Cutting: AL-0083 (i) (ii) Preferential: AL-0003 (7) H2SO4, cone: (electrolytic) (i) Anodizing: AL-0020b (8) (yN2 w/H2O (electrolytic) Air: (i) Anodizing: AL-0040; -0049; -0050; -0052 © 1991 by CRC Press LLC

96 83 (9) H2SO4:H3PO4: Polish: AL-0041a (i) H2SO4:H3PO4:HNO3: (10) -0097; -0045 Polish: (i) AL-0035; (electrolytic) H3PO4:HAc: (11) (i) AL-0024; -0087; -0090 Polish: (12) H3PO4:HNO3:H2O: (i) Cleaning: AL-0033 Removal/Polish: -0033b (ii) AL-0009; H3PO4:HNO3:HAc:H2O: (13) (i) Removal/Polish: -0014; -0084 AL-0010; (ii) Selective: AL-0031 H3PO4:H2O2:H2O: (14) (i) Removal/Polish: -0067 AL-0011; H3PO4:H2O:Glycerin: (15) AL-0007 (i) Removal/Polish: H3PO4:HNO3:A1-Brite: (16) (i) AL-0013 Polish: (17) H3PO4:Cr2O3: removal: AL-0002 Oxidation (i) H2SO4:Na2Cr2O7:H2O: (18) Cleaning: (i) AL-0032 HF:H2O: (19) Preferential: AL-0023b; (i) Removal: AL-0091 (ii) HF:NH4F:HF: (BHF) (20) (i) Cleaning: AL-0030a (21) HF:HC1:H2O: (i) Preferential: -0020a AL-0017; HF:HCl:MeOH/EOH: (electrolytic) (22) AL-0025b (i) Polish: (23) HF:HNO3:HC1:H2O: (i) Cleaning: AL-0081 Preferential: AL-0030; -0020a; -0058; -0059a (ii) (iii) Polish: AL-0030 HF:HNO,:HCl:Glycerin: (24) (electrolytic) (i) Polish: AL-0027 HNO3:MeOH: (25) (electrolytic) (i) Polish: AL-0027 (26) FeCl3:H2O: (i) Removal: AL-0004 (27) CuCl3:H2O: Polish: (i) AL-0022a (28) HClO4:MeOH: (electrolytic) Polish: (i) -0038; -0039a; -0042; -0033; -0035 AL-0037; (29) HClO4:EOH:H2O:Butyl Cellusolve: (electrolytic) (i) AL-0044 Polish: (30) HC104:HAc: (electrolytic) (i) Polish/Removal: AL-0046; -0049; -0048 (31) HClO4:EOH:Glycerin: (electrolytic) (i) Thinning: AL-0047; -0091 © 1991 by CRC Press LLC

97 84 CRC of Metal Etchants Handbook NaOH:H2O: (electrolytic) (32) AL-0064 Removal/Polish: (i) NaOH:H2O:(Glycerin) (33) Removal/Polish: -0093; -0062; -0077; -0078 AL-OO33a; (i) NaOH:HNO3:H2O: (34) AL-0030 Cleaning: (i) (35) NaOH:HNO3:MeOH: AL-0041b; (i) -0055a Preferential: -0045; KOH/NaOH:H2O: (36) AL-0001; -0066 (i) Cleaning: -0061; -0062; AL-0002 (ii) Oxidation: AL-0003a; -0062; -0063; -0065 (iii) Removal: KOH:H2O: (electrolytic) (37) (i) Cleaning/Removal: AL-0064 KOH:K3Fe(CN)6:K2B4O7.4H2O: (38) Al-0019a; -0084 (i) Removal: KLMeOH: (39) (i) AL-0094 Selective: (40) CC14: AL-0091; -0092 (i) Removal: (41) Br^Br: Removal: AL-0092 (i) GAS: (molecular) Air AL-0061; -0049; -0030; -0052 (1) (oxidation): (2) Chlorine, Cl2 (removal): AL-0092 GAS: (DCE) (ionic) (1) BCI3/AICI3 (selective): AL-0051; -0089( + O2) (2) BBr3 (removal/polish): AL-0056; -0059b; -0054 (3) SiCl4 AL-0089 ( + O2) (removal): Neon, Ne AL-0040 (4) (preferential): ABRASIVES: SiC, (polish/forming): (1) AL-0076 paper A12O3, (polish): AL-0100 (2) powder ANODIZING/OXIDATION: H2SO4 (electrolytic): AL-0020b (1) Air, (2) + H2O: AL-0040; -0049; -0050; -0052; -0030; -0061 Nj/O2 Water, H2O (cleaning): AL-0101 (3) (4) (cleaning): AL-0002 KOH/NaOH:H2O NAMED/NUMBERED ETCHANTS: (1) BHF:(HF:NH4HF.HF) (cleaning): AL-0030a (2) BRM: (removal/polish): AL-0082a (Br2:MeOH) Flick's Al-0027; (HF:HC1:H2O) (preferential): (3) -0023c Etch General Etch (HF:H2O) (preferential): Al-0023d (4) (5) Iodine Etch (I2:MeOH) (structuring): Al-0031 (6) Etch (HClO4:HAc — electrolytic) (removal): AL-0048 Jacquet's (7) Keller's Etch (HF:HNO3:HC1:H2O) (preferential): AL-0023a; -0043 (8) Nital (HNO3:EOH/MeOH) (polish): AL-0022b; -0065a; -0061 © 1991 by CRC Press LLC

98 85 THERMAL +H2 or (reducing atm) (cleaning/annealing): AL-0102 (1) N2/H2 (oxidizing atm) See Air or Anodizing (2) +O2 (cleaning/anodizing): (preferential): AL-0039a-b (3) + Vacuum ELECTRICITY: Thin (creep): AL-0041 (1) Film FATIGUE: Thermal-vacuum (1) See AL-0096 (2) Pressure: evaporated beryllium an aluminum/beryllium alloy, pure (30%) have been and Both AlBe further reduce the mass-loading effect. to has been evaporated on telescope lenses, then overcoated with a thin layer Aluminum silica, of for wear resistance. The aluminum used as an absorber and reflector. And SiO2 lenses periodically stripped for recoating. such are parts are used in package assemblies and, the combination of aluminum and Aluminum are resistant as radiation alumina packages. Aluminum foil is used as a grounded important temporary wrapping sensitive devices, and as a static shield in vacuum evaporator bell for jars. Single crystals of pure aluminum, as well as several alloys, have been grown for general morphological study, evaluation and a wide range of defect, corrosion and fatigue electrical of studies. include the other physical structures studies aluminum: colloidal, failure These and crystalline. amorphous Soluble in HC1, HNO3, H2SO4, alkalies and acid Etching: Gas mixtures as mixtures. an Plasma. RF ETCHANTS ALUMINUM AL-0033a NAME: Sodium hydroxide TIME: ETCH TYPE: removal TEMP: Alkali, COMPOSITION: x... lMNaOH DISCUSSION: Al thin film removal from vacuum evaporation systems. Used for removal of metal build-up from steel, glass, copper, and ceramic surfaces. Can damage titanium and stainless can surfaces. notes that hydroxide cleaning Another leave residual contamination on silver parts unless thoroughly washed. {Note: An excellent article on cleaning procedures for vacuum deposition equipment.) State Nichols, R — REF: D Technol, December 1979 Solid AL-OO33b ETCH NAME: TIME: TYPE: removal TEMP: Acid, COMPOSITION: 20...H3PO4 2 ... HNO3 5 ... H2O © 1991 by CRC Press LLC

99 86 CRC of Metal Etchants Handbook DISCUSSION: Al removal from vacuum evaporation systems. Use for removal from steels, thin film ceramics. glass use on copper parts. Do and not REF: Ibid. AL-0003 ETCH Hydrochloric acid TIME: 2—10 min NAME: TEMP: RT TYPE: Acid, removal COMPOSITION: cone. 1 ... HC1 (1) (2) X...HC1, H2O 1—10 ... DISCUSSION: film removal from vacuum evaporation systems. Used to Al multiple layer thin remove of and gold germanium from steel, glass and ceramic films aluminum/nickel/chromium/gold solutions Used commonly used, particularly on copper parts. dilute to soak and — more lint-free parts stainless steel brush. Used with a cloth dampened with solution to scrub with base plates wipe other in-place fixturing after light scrapping to remove heavy build and up. surfaces should be well wiped down with a water soaked cloth after acid cleaning Such follow with alcohol. Vacuum pump-down after cleaning to at least 10"6 Torr methyl and use. system before REF: Walker, P — personal application, 1960—1980 Hurden, M J & Averbach, B L — Acta Metall, 9,237(1961) AL-0005: (111) and (100) wafers Al ingots. A 50% solution was used to "heavy" etch and in in study of dislocation density specimens deformed aluminum. a AL-0033c ETCH Potassium hydroxide TIME: Variable NAME: 180°F Alkali, TYPE: RT to removal TEMP: COMPOSITION: x... 8—10%KOH(NaOH) DISCUSSION: Al and Al alloys. At room temperature solution is slow and used as a surface cleaning etch. Used for heavy removal. RT solutions used for removal of aluminum evaporation hot bell jars fixtures of vacuum systems — glass, SST, and ceramic material. onto and Ibid. REF: P & Menth, M Walker, personal application, 1981 Al-0060: — evaporated film deposits in vacuum systems. Solution used for cleaning systems. Al, with IR water washing and Follow lamp drying. Vacuum bake system before use. heavy used hydroxide. Also sodium Stirland, D J & Bicknell, R W — J Electrochem Soc, 106,481(1959) Al-0002: A specimens in a study of surface oxidation. used 3% NaOH solution, RT, 3 min Al, used to clean surfaces. After anodizing, a solution of 35 ml H3PO4:20 g Cr2O3/l used to remove the oxide. DeSorbo, — Phys Rev, 111,810(1958) Al-0001: W single crystal specimens used in a study of imperfection at low temperature. Used Al, clean solution 15% NaOH, warm as a pickling solution to of surfaces. a AL-0061: Walker, P — personal application, 1964 Al and AISi (5%) alloy as spherical pellets used in fabricating Silicon Sphere Alloy clean Zener a 1% KOH solution to Used wafers with multiple alloyed junctions after diodes. fabrication prior to DC leakage evaluation. Contour plots of leakage of devices on wafers wafers used determine segregation zones in ingots with to cut and numbered consecutively for traceability. © 1991 by CRC Press LLC

100 87 AL-0062: W H & Walker, P — personal application, 1976 Tarn, thin film on soda-lime glass used for photo resist masks and special Al, evaporation aluminum 30% warm (40°C) used to remove solution, and clean the glass. A lenses. NaOH M — personal communication, 1982 AL-0063: Menth, films telescope on thin lenses for reflectivity control. A 15—20% NaOH Al, evaporated prior RT warm used to remove aluminum at to re-work of old lenses. solution or Tegart, W J McG — The Electrolytic and Chemical Polishing of Metals in Research Al-0064: Industry, 1956 Press, London, and Pergamon and Al Alkali solutions used for etching and cleaning. Includes a discussion Al alloys. metals and chemical as preferred over mechanical lapping of electrolytic in order of etching preserve bulk characteristics. to ASTE Committee — Tool Engineers Handbook, McGraw-Hill, New AL-0065: 1949 York, Al, specimens, and other soft metals such as tin and zinc. Buffer alkali solutions alloy silicates, silicates reduce with attack. A 5% NaOH solution plus carbonates, to phos etch phates, or borates as buffers recommended for general etching. AL-0066: Campos, R & Walker, P — personal application, 1961—1963 Al alloy and parts on 2000 gallon capacity cryogenic trailers. 5—10% NaOH piping used for removal cleaning of surfaces with plastic brush scrubbing, and solutions corrosion wash Final etching. water drying with warm nitrogen gas. heavy after AL-0019a NAME: TIME: ETCH TYPE: Acid, removal TEMP: COMPOSITION: ... KOH x ... x K3Fe(CN)6 ... K2B4O7.4H2O x DISCUSSION: type on semiconductor wafers. Use COP films photo resists to coat surfaces Al, thin develop patterns using and photolithographic techniques. Use solution shown to standard remove aluminum. COP resists etch exposed slowly than the aluminum. more REF: Turner, JK — JVac Sci Technol, 15,962(1978) AL-0010 ETCH NAME: TIME: TYPE: Acid, removal TEMP: COMPOSITION 1520 ml ... . H3PO4 ... ml HAc . 120 ... 50 ml . HNO3 ml 300 . H,O ... DISCUSSION: Al, thin films deposited on GaAs and silicon (100) wafers. Use AZ-type photo resists photolithographic to open patterns with standard and techniques. The solution was used coat to remove aluminum and will attack both wafer and aluminum. After etching, rinse in DI water; and nitrogen blow dry. MeOH REF: Shipley Sales Brochures, 1975—1980 © 1991 by CRC Press LLC

101 88 CRC of Metal Etchants Handbook AL-0014 ETCH NAME: TIME: removal TYPE: TEMP: Acid, COMPOSITION: H3PO4 80 ml... ml... HAc 5 5 ml... HNO3 H2O ml... 10 DISCUSSION: films evaporated as Al of a layer metallization structure on Si(lOO) substrates, thin part Ni/TiN/Al/Si(100). photo resist patterning, etch After Ni and TiN, then use as remove shown for removal of aluminum layer. solution Ballard, REF: L et al — J Electron Mater, 13,327(1984) N AL-0009 ETCH NAME: TIME: removal TEMP: Acid, TYPE: 40°C COMPOSITION: RATE: 1500 A/min ml ... H3PO4 80 ml HNO3 5 ... ml ... H2O 0—20 DISCUSSION: with Used as Al general removal etch specimens. agitation. (Note: Rate shown is a a guideline, only as water content varies.) REF: AL-0011 NAME: Krumm TIME: ETCH etch removal 35°C Acid, TIME: TYPE: COMPOSITION: RATE: 100 A/sec 8 ... H3PO4 ... H2O2 1 1 ... H2O DISCUSSION: thin Al evaporated on GaAs, (100) wafer substrates. Solution used to remove films aluminum in photo resist pattern etching. and will also attack gallium arsenide at Solution a more rapid rate than aluminum. REF: Siracusa, — personal communication, 1979 M AL-0067 ETCH TIME: NAME: Aid, removal TEMP: RT TYPE: COMPOSITION: 2 H3PO4 ... ... 1 H2O3 3 ... H2O DISCUSSION: Al thin films evaporated on silicon and gallium arsenide, (111) wafers. Solution used interfaces. as general removal etch in studies of metal/substrate a REF: Topas, B — personal communication, 1970 © 1991 by CRC Press LLC

102 89 AL-0007 NAME: TIME: ETCH removal Acid, TEMP: TYPE: 80°C A/sec 60 COMPOSITION: RATE: ml ...H3PO4 30 10 ml ...H2O glycerin ... ml 50 DISCUSSION: films evaporated on GaAs, (100) substrates used in fabricating GaAs Al thin FETs. used remove the aluminum gates of devices in studying the Al/GaAs interface. Solution to P Walker, personal development, 1979 REF: — AL-0013 NAME: Brite dip TIME: ETCH Acid, polish TEMP: TYPE: RT COMPOSITION: ... H3PO4 x HNO3 x ... ... Al-brite x DISCUSSION: and alloys. Mixtures Al these acids are polish type solutions for aluminum. specimens of addition of Al-Brite to the solutions improves the surface The and gives better etch polish control. Heatbath Bulletin Metal Finishing Products, — Corp., 1984 REF: #H681-10M AL-0032 NAME: ETCH 10 min TIME: TYPE: Acid, cleaning TEMP: 150°F COMPOSITION: 27 ... H2SO4 3 ... Na2Cr2O7 70... H2O DISCUSSION: thin sheet material and as an evaporated as film on other materials. Solution Al alloys the preferred surface cleaning etch in preparing surfaces for plastic film adhesion, is giving the adhesion results. After etching, rinse in cold water, then hot water, best air dry. and (Note: is a form Solution the standard glass cleaner mixture.) of REF: Skeist, I — Epoxy Resins, Reinhold, New York, 1959, pp 190—192 AL-0024 ETCH TIME: 3—5 min NAME: Electrolytic, TEMP: RT TYPE: polish COMPOSITION: ANODE. Al ... H3PO4 CATHODE: 2 30 7 (HAc) POWER: 10, 20, CH3CHOOH & 40 V ... DISCUSSION: Al specimens used in a study of interfacial structures. Solution used to polish material prior etch developing structure. to REF: Randall, S T & Bernard, A — J Appl Phys, 34,1210(1964) © 1991 by CRC Press LLC

103 90 CRC of Metal Etchants Handbook AL-0004 ETCH chloride TIME: NAME: Ferric removal TYPE: TEMP: Salt, 110°F COMPOSITION: FeCl3 ... x solution is Note: Baume A standard 35° DISCUSSION: Al alloys. A general etch for aluminum and Al heavy metals, such as irons and several steels. has been used as a general removal It polishing solution as well as a preferential and or depending upon concentration and method of etch Use at RT, hot to boiling. application. After wash heavily in water until all traces of the brown colored solution is removed. etching, Meyer, Soc, M & Brown, S H — Proc Am Electropl REF: 36,163(1949) W AL-0029 ETCH Boron trichloride TIME: NAME: Ionized gas, removal TEMP: TYPE: GAS FLOW: COMPOSITION: ... PRESSURE: (l)x BC13 POWER: (2)x...CHCl3 x ... Cl2/Ar (3) DISCUSSION: Al thin film evaporations used in semiconductor device fabrication. Gas used for reactive ion etching controlled removal of aluminum after photo resist patterning. Better (RIE) for of chemical than by wet control etching. removal A12O3/A1 J R Bruce, Malafsky, G P — H Electrochem Soc, 130,1369(1983) REF: & AL-0022a NAME: Cupric chloride TIME: ETCH TEMP: Salt, TYPE: polish COMPOSITION: CuCl2 ... x x...H2O DISCUSSION: specimens. Wafers were polished in this Al single crystal studies X-ray to prior solution bulk structure. and surface of 103,547(1956) REF: Walker, C B — Phys Rev, AL-0023a Dip TIME: ETCH NAME: Keller's etch RT TEMP: TYPE: microetch Acid, COMPOSITION: #3 ASTM: ...HF 2ml 5 HNO3 ... ml 3 ml ... HC1 190ml...H2O DISCUSSION: Al, alloy and cast aluminum specimens. Solution used as a general micro-etch in the study surface structure. of REF: AJB Metal Digest, 21(2),23(1983) — Buehler Ltd AL-0043: ASTM E407-70 Reference for Keller's Reagent as #3. © 1991 by CRC Press LLC

104 91 AL-0023b NAME: Hydrofluoric TIME: Swab/dip ETCH acid macro-etch TYPE: TEMP: Acid, RT COMPOSITION: ... HF ml 1 ml ...H2O 199 DISCUSSION: alloy content specimens. Solution used as a macro-etch by swabbing Al, surface low the immersion to develop surface structure. or dipping Ibid. REF: JpnJ AL-0021: Okada, Y — Tokumaru, Appl Phys Lett, 23,123(1984) Y & thin film aluminum deposited on both Si, (100) and GaAs, Al Cr semi-insulating (100): (SI) Solution used to remove aluminum after photo resist patterning. wafers. AL-0030 ETCH (1)5 sec or (2) 15 sec NAME: TIME: Acid, preferential TEMP: (1) 0°C (2) 8°C TYPE: polish, COMPOSITION: 4 ... HF (2) 1 (1) solution (1) ... 35 HNO3 100ml...H2O ... ... 61 HC1 DISCUSSION: single crystal specimens. Solution (1) Al as a polish etch; solution (2) is used slightly preferential. Ice/acetone = 8°C, and dry ice/acetone = 0°C used for the two cold temperature applications. Tucker, G & Murphy, PC —JInstMet, 8,235(1953) REF: EG AL-0017a-b NAME: etch TIME: 10—20 sec ETCH Flick's macro-etch TEMP: RT TYPE: Acid, COMPOSITION: x ... HF (2) ml ... HC1, cone. 10 (1) 5 ... HC1 ml 90 H2O ml... DISCUSSION: Al, alloys. Etch used for preparation of metallographic specimens as a macro- cast black structure etching with solution (1) remove After smut that remains by dipping solution. in concentrated hydrochloric acid (2) and rinse in DI water. REF: AIB Dig, 21(2),23(1983), Buehler Ltd Met AL-0020a ETCH TIME: NAME: Acid, preferential TEMP: TYPE: COMPOSITION: 3% ...HF 47% ... HNO3 50% ... HC1 DISCUSSION: Al specimens. Specimens were anodized and etched in solution shown in a study of dislocation and patterns developed in aluminum by oxidation. loops REF: Bassett, G A & Edeleanu, C — Phil Mag, 5,709(1960) © 1991 by CRC Press LLC

105 92 CRC of Metal Etchants Handbook AL-0020b ETCH acid TIME: NAME: Sulfuric anodizing TYPE: TEMP: Electrolytic, ANODE: Al COMPOSITION: Pt 10% ... H2SO4 CATHODE: 15 POWER: V DISCUSSION: were Al and etched in a study of dislocation loops and specimens. Specimens anodized used 3% NaCl at 1.5 V. A third anodizing patterns. was 4 ml H2SO4:12 g Also solution ml at 30 V. Na2H3PO4:100 H2O Ibid. REF: AL-0037 NAME: TIME: ETCH polish TEMP: 0 to - 10°C TYPE: Electrolytic, Al ANODE: COMPOSITION: CATHODE: 1 ... HC1O4 5 ...MeOH 20 V POWER: DISCUSSION: wafers used in Al, (100) oxidation study. Both single crystals and tri-crystals used. an Polish in solution shown prior to oxidation. surfaces Doherty, D & Davis, K S — J Appl Phys, 34,619(1963) REF: E — J & Backofen, W A H Ada Metall, 9,352(1961) AL-0038: Alden, (100) wafers used in a study of fatigue crack Al, Solution used prior to formation. stressing as an electropolish using 60 V power. specimens Noggles, S—JAppl Phys, 28,913(1957) AL-0039a: T wafers used in a Al, (100) of thermal etch patterning surfaces. Solution used to study electropolish surfaces prior to thermal annealing. Polishing done at less than — 10°C with power at 16 A/cm2. about Alden, J — Rev Sci Instr, 31,897(1960) AL-0042: H electro crystal used in a material single study. Solution used to specimens Al, failure specimens at -50°C with solution continually stirred. polish Mehdizadeh, P & Block, R J — J AL-0015: Soc, 119,1090(1972) Electrochem Al, crystal ingots grown by boat method (Bridgman) using a graphite crucible. single cutting specimens surface orientation, After were electropolished in a perchloric acid/ for solution prior to studying slip caused by oxidizing surfaces. alcohol AL-0107: McGrath, J T & Waldron, G W J — Phil Mag, 9,249(1964) Al:Mg(l%) ingots wafers used in a dislocation study. Solution used as an electro and with replacing MeOH in the formula shown. polish EOH AL-0018 NAME: Iodine etch TIME: 3—8 min ETCH Halogen, TYPE: TEMP: 70°C structuring RATE: 1 COMPOSITION: mil/min (1) 10 g ...I2 (2) x...MeOH 100 ml ... MeOH DISCUSSION: Al films and crystalline aluminum sheet. thin were anodized, then a channel Specimens pattern was cut through the oxide with a diamond scribe. Solution shown was used to etch to channels the aluminum. Rinse in MeOH in remove residual iodine. KMER photo resist © 1991 by CRC Press LLC

106 93 was used for pattern definition and oxide removed with H3PO4 to expose the aluminum. also Walker, P Schwartz, B — personal application, 1957 REF: & AL-0027 NAME: modified TIME: ETCH Nital, polish TEMP: TYPE: Electrolytic, Al COMPOSITION: ANODE: HNO3 CATHODE: 1 ... EOH POWER: 2 ... DISCUSSION: single crystal specimens used in a study of twin boundaries. Solution used to polish Al, prior preferential etching. specimens to Aust, K T — Trans Met Soc AIME, 221,758(1961) REF: AL-0022b ETCH modified TIME: NAME: Nital, Electrolytic, TEMP: TYPE: polish COMPOSITION: ANODE: Al ... HNO3 CATHODE: 1 ... POWER: 2 EOH ASTM: #74 DISCUSSION: lattice single specimens. Solution used to polish Al, for a crystal vibration X- surfaces ray study. REF: Ibid. AL-0064a: ASTM E407-70 Reference for ASTM #74. Solution shown as: 1—5 ml HNO3:100 ml EOH/MeOH. AL-0108: Grooskreutz, C & Shaw, G G — J Appl Phys, 35,2194(1984) J structure (100) in a study of anodic used on oriented surfaces. Various Al, specimens of Nital as HNO3:MeOH were used. mixtures AL-0025a ETCH TIME: 7—10 min NAME: Electrolytic, TEMP: 0—8°C TYPE: polish ANODE: Al COMPOSITION: ... HF CATHODE: 2% ... 15% POWER: HNO3 42% ... HC1 15% ... glycerin DISCUSSION: Al, crystal specimens. Solution used to electropolish surfaces. single Hone, C & Pearson, E REF: — Met Prog, 53,363(1948) A AL-0006 ETCH NAME: TIME: TYPE: Acid, cleaning TEMP: COMPOSITION: x...5%NaOH x 50% HNO3 ... DISCUSSION: Al, polycrystalline sheet. Coupons cut from sheet and used in a study of anodization. Clean surfaces with solution shown before oxidizing. REF: Ibid. © 1991 by CRC Press LLC

107 94 CRC of Metal Etchants Handbook AL-0031 ETCH NAME: TIME: removal TYPE: TEMP: Acid, COMPOSITION: 80ml...H3PO4 ml HNO3 ... 5 5ml...HAc 10ml...H2O DISCUSSION: evaporation layer Al, in a diode metallization structure as Ni/TiN/Al on thin film used (100) substrate. After photolithographic a for diode pattern structure and metal Si, processing evaporation, metal was selectively removed—aluminum with the solution shown. layer each Electron T L al — J et Mater, 3,309(1984) REF: Martin, AL-0039b NAME: Heat TIME: ETCH Thermal, TYPE: TEMP: preferential COMPOSITION: x ... heat DISCUSSION: wafers in a study of surface etch pits developed from Al, (100) of used concentration etch during thermal annealing. Surfaces were vacuum polished prior to clusters vacancy anneal. thermal AL-0039a. See REF: Ibid. — Pierce, & Thomas, T L M Appl Phys Lett, 39,165(1981) AL-0012: J Al, fim thick thin films evaporated on Si, (100) heated substrates (360°C) pre-coated 0.2 with thin film SiO2. Evaporated aluminum film was photo resist patterned as conductors and overcoated p-SiO2 (BSG). After aluminum wire bonding, current was applied at with chains temperatures conductors and electromigration was observed as discrete different on single crystal aluminum crystallites. of AL-0040 NAME: Neon TIME: ETCH Ionized TEMP: preferential TYPE: gas, GAS COMPOSITION: FLOW: x ... Ne+ ions PRESSURE: POWER: DISCUSSION: single Al, specimens ion bombarded to develop and observe etch figures on crystal surfaces. Other materials studied were Bi, Cd, Mg, Cu, Sn, and Zn. REF: Yurasova, Kristallografiya, 2,770(1957) V E — AL-0023C ETCH Flick's Etch NAME: sec TIME: 10—20 TYPE: Acid, micro-etch TEMP:RT COMPOSITION: 10 HF ml... (1) HNO3 ... x (2) ml HC1 ... 5 ... 90 ml H2O DISCUSSION: Al, specimens remove and cast alloys. HNO3 Used to Solution used as a structure etch. etching. after smudge remaining REF: Ibid. © 1991 by CRC Press LLC

108 95 AL-0023d NAME: General Dip/swab ETCH TIME: micro-etch TYPE: TEMP: Acid, RT COMPOSITION: ... HF ml 1 ml ... H2O 199 DISCUSSION: and alloys with low aluminum Al, Solution used as a macro-etch specimens content. swabbing dipping specimens. by or Ibid. REF: AL-0025b NAME: TIME: 7—10 min ETCH Electrolytic, polish TYPE: 0—8°C TEMP: COMPOSITION: Al ANODE: ... HF 4% CATHODE: HC1 POWER: ... 70% ... MeOH/EOH 25% DISCUSSION: single crystal specimens. Solution used to electropolish surfaces in Al, shown. solution REF: Ibid. AL-0026 ETCH TIME: NAME: Acid, cleaning TEMP: TYPE: COMPOSITION: ... HN03 x x ... NR.F.HF DISCUSSION: Al, polycrystalline sheet. Coupons cut and used in a study of aluminum anodization. Clean surfaces solution shown before oxidizing. with Solid Sharp, et al — Thin J Films, 111,227(1984) REF: D AL-0034 NAME: Hydrochloric acid TIME: ETCH Electrolytic, TYPE: TEMP: polish ANODE: COMPOSITION: ... 30% HC1 CATHODE: 1 ... H2O POWER: 3 DISCUSSION: Al, specimens. A general electropolish for aluminum. of REF: & Dearden, W H — Metallographer's Handbook T Etching, Pitman & Berglund, Sons, London, 1931 AL-0035 ETCH NAME: TIME: '/2—2 min TYPE: polish TEMP: 85°C Acid, COMPOSITION: 25 ml ... H2SO4 70 ml ... H3PO4 5 ml ... HNO3 © 1991 by CRC Press LLC

109 96 CRC of Metal Etchants Handbook DISCUSSION: Al, in developing polished surfaces. The solution will also polish Al:Cu specimens used alloys. Al:Si and J & Segond R — Rev Met, 48,262(1951) (in French) Herengue, REF: J Rev Herengue, Alum, 30,261(1953) AL-0097: — polishing. and A specimens of chemical alloys. Al discussion AL-0036 ETCH NAME: TIME: Acid, cleaning TEMP: TYPE: COMPOSITION: 95% H3PO4 ... ... HNO3 5% DISCUSSION: being slugs cleaned in this high before purity used to grow AlSb. After Al, solution cleaning, rinse with in etch water. DI REF: W P et al — J Electrochem Soc, 107,117(1960) Allred, AL-0103 ETCH NAME: Hydrochloric acid TIME: TYPE: Electrolytic, preferential TEMP: COMPOSITION: ANODE: Al x ... cone. CATHODE: HC1, POWER: DISCUSSION: specimens. Solution will develop etch figures. Al, Mahl, M & Stranski, L — Z Phys Chem, 257,53(1942) REF: AL-8104 ETCH Sodium hydroxide, dilute TIME: NAME: Alkali, RT TEMP: TYPE: polish RATE: COMPOSITION: jjum/h 1 2g ...NaOH 1000ml...H2O DISCUSSION: Al, cold-rolled specimens used in a study of the effect of thickness on dislocations. surface Solution agitation to produce a highly polished with without any pitting prior used to dislocation etching. REF: Ham, R K & Wright, M G — Phil Mag, 9,937(1964) AL-0105 NAME: TIME: ETCH TYPE: Acid, preferential TEMP: COMPOSITION: 1 ... HC1 1 H2O ... x ... *FeCl3 ♦Saturate solution with FeCL © 1991 by CRC Press LLC

110 97 DISCUSSION: (100) wafer preferentially etched in this solution. Al, surfaces P REF: Rend, 201,1473(1935) — Jacquet, Comp AL-0050 Sodium hydroxide TIME: ETCH NAME: removal TEMP: TYPE: Electrolytic, Al COMPOSITION: ANODE: 2.5 NaOH CATHODE: x M ... POWER: mg/cm2/h 0.005 RATE: DISCUSSION: specimen surface coatings produced by electrodeposition or diffusion of nickel. Al:Ni shown Solution as a cleaning etch. used J Couch, & Connor, J H — E Electrochem Soc, 107,272(1960) REF: D AL-0051 NAME: Carbon tetrachloride TIME: ETCH TYPE: Solvent, TEMP: Boiling removal COMPOSITION: x CC14 ... DISCUSSION: specimens. A study of Al, reaction of carbon tetrachloride on aluminum. Aluminum the reacts rapidly in concentrated CC14. A number of additives were used to inhibit the rate. REF: Minford, D et al — J Electrochem Soc, 106,185(1959) J AL-0058 ETCH NAME: TIME: preferential Acid, TYPE: TEMP: COMPOSITION: HF 15% ... HC1 15% ... 15% ... HNO3, fuming ... H2O 25% DISCUSSION: Al, Solution used to develop etch figures. (Note: "Fuming" concentration specimens. and color specified.) not Tucker, C REF: — Met Alloys, 1,655(1930) M AL-0059a ETCH NAME: TIME: TYPE: Acid, TEMP: preferential COMPOSITION: 10 HF ... ... HC1 46 15 HNO3 ... 26 ... H2O DISCUSSION: Al, specimens. Solution used as a preferential etch on aluminum. (Note: Does not specify fuming acid; otherwise similar to AL-0058.) nitric REF: Barrett, C & Levenson, L H — Trans Am Inst Min Met, 137,112(1940) (England) © 1991 by CRC Press LLC

111 98 CRC of Metal Etchants Handbook AL-0041a ETCH 2 min NAME: TIME: polish TYPE: TEMP: Acid, 70°C COMPOSITION: H2SO4 ... 10 ... H3PO4 90 DISCUSSION: used in Al, study of lithium precipitation along dislocations. After (001) wafers a this solution polishing coat surfaces with 0.1% Li (usually in oil), heat and bubbles in — appear dislocation lines. will along G Murray, — J Appl Phys, 32,1014(1961) REF: T __ ___ NAME: TIME: 10 sec ETCH Acid, dislocation 10°C TYPE: TEMP: COMPOSITION: 2ml...HF 50ml...HNO3 32ml...HCl 50ml...MeOH DISCUSSION: wafers. Following Al, show in Al-0041a, develop dislocation density (001) treatment this solution — lithium created "bubbles" vary but with about equal in number to are dislocation — all pits were on one side of wafer and pits movement after annealing showed at 575°C for 9 h. REF: Ibid. AL-0045 ETCH NAME: TIME: Seconds TYPE: Acid, TEMP: RT preferential COMPOSITION: 3 ... HF HNO3, ... fuming 47 80 ... HC1 DISCUSSION: and other orientations Al, in a study of thermal etching. After thermal (100) used at annealing to 610°C use solution shown as a dislocation etch. (Note: Red or yellow 460 fuming, shown.) not Foss, D & REF: OH — Phil Mag, 13,945(1966) Herbjornsen, AL-0055a; Lacombe, P & Beaujard, L — Inst Met J, 132,1(1947—48) Al, high specimens used in a study of etch figures and structure. Solution used purity are 10°C, min. If iron or other metal ions at in the HC1, it will affect controlled V2—1 etching. With addition of water in the solution shown etch figures increase in number but primarily decrease size with water increase. The HC1 produces in localized attack and HF uniformally dissolves aluminum. © 1991 by CRC Press LLC

112 99 AL-0044 NAME: ETCH min 2 TIME: polish TYPE: Electrolytic, TEMP: COMPOSITION: Al ANODE: HC1O4 78 ml ... CATHODE: ml ... EOH 700 POWER: 25—35 V/cm2 ml... 120 H2O . 100 cellusolve . ... ml butyl DISCUSSION: etching Al, in a study of surface specimens effects of 8 KeV Ar+ ion (1000) used Polish surfaces with solution shown before bombardment. Specimens of bombardment. zinc and also were studied but etched in other solutions. gold 31,839(1960) Cunningham, et al — J Appl Phys, L REF: R AL-0016 ETCH NAME: TIME: 30—120 sec Acid, polish TEMP: 65°C TYPE: COMPOSITION: 25 ... H2SO4 ml ml 70 ...H3PO4 5 ml ... HNO3 DISCUSSION: and aluminum alloys. Al, as a general cleaning and polishing etch. See AL-OO35. Used REF: Tegart, W J McG — The Electrolytic & Chemical Etching of Metals, Pergamon Press, London, 1956 AL-0046 ETCH NAME: TIME: polish Electrolytic, TEMP: TYPE: COMPOSITION: ANODE: HC1O4 12 ... CATHODE: ... HAc POWER: 88 DISCUSSION: (001) wafers and other orientations. Solution used Al, polish specimens in a study to of desorption. Also studied molybdenum and magnesium. stress-induced — Fouerstein, & John, I W REF: J Appl Phys, 40,3334(1969) S AL-0047 ETCH NAME: TIME: Electrolytic, TEMP: 0°C (ice) TYPE: thinning COMPOSITION: ANODE: ... HC1O4 1 CATHODE: 1 ... glycerol POWER: 7 ... EOH DISCUSSION: Al, single crystal wafers. Specimens etch thinned in this solution for a study of electrical resistivity dislocations. of REF: Rider, J G & Foxon, T B — Phil Mag, 13,289(1966) © 1991 by CRC Press LLC

113 100 CRC of Metal Etchants Handbook AL-0049 ETCH 1—2 h NAME: TIME: polish TYPE: TEMP: Electrolytic, 20°C ANODE: COMPOSITION: CATHODE: 20...HClO4 35 V & ... mA/ POWER: HAc 80 500 cm2 DISCUSSION: Specimens specimens. surfaces in this solution. Polish were subjected crystal Al, single environments in a study to surface etch pit development. various of Kasen, K et al — Phil Mag, 13,453(1966) REF: M AL-0048 NAME: etch TIME: ETCH min 30 Jacquet's removal TEMP: TYPE: Electrolytic, ANODE: COMPOSITION: 345 ... HC1O4 CATHODE: ml ml ... HAc 655 POWER: DISCUSSION: single crystal cut from an ingot that was slow cooled. Specimens were Al, specimens in this with a removal in about 30 |xm per side. Used solution a dislocation polished of study as related to slow cooling. density Nes, REF: & Nost, B — Phil Mag, 13,855(1966) E AL-0026 NAME: Air 15—48 h ETCH TIME: oxidation Gas, 55O°C TYPE: TEMP: COMPOSITION: x ... air DISCUSSION: oxidation. single sphere. Sphere electropolished prior to crystal No change in 15 h Al, sitting in air; faint patterns after 48 h of oxidation. Developed foggy pole figures at axial points of (110) and least on (111). (100); Gwathmey, A et al — Mater Advisory Comm Aeronaut Tech Notes #1460(1948) T REF: J S et al — M Appl Phys, 39,4026(1968) Bedair, AL-0050: (100) wafers used in a study of oxidation. Forms an amorphous oxide Al, below film 600°C. 600°C film becomes crystalline A12O3. Above Bond, Appl E & Harvey, K B — J AL-0052: Phys, 34,440(1963) H that Al, was done with synthetic sapphire Work was polished on a maple specimens. lap with diamond dust in oil. With 1% by weight ZrO2 in the material, dislocations are seen on the basal plane. Oxide growth on aluminum can cause subsurface damage and (0001) metallic where pitting to the A12O3/A1 interface pitting the O2 aluminum. moves AL-0053 ~~~ ETCH NAME: Boron trichloride TIME: TYPE: Gas, selective (RIE) TEMP: COMPOSITION: FLOW: GAS x ... BC13 PRESSURE: POWER: DISCUSSION: Al, thin films deposited on GaAs, (100) wafer substrates. Layered structures were: (1) resist Al/Ni/SiO2 (2) Al/Ni/SiNx. Surfaces were photo or processed for patterning to include © 1991 by CRC Press LLC

114 101 via-holes the gallium arsenide in fabricating monomicrowave ICs. Both BC13 and through were used removal of aluminum. Removal of nickel referred to as a nickel lift CF4:O2 for off technique. REF: & Claytor, PR —J Vac Sci Technol, A(3),863(1985) Gelsgberger, A E AL-0054 Boron TIME: ETCH NAME: tribromide (RIE) TEMP: Gas, TYPE: removal FLOW: 40 cc COMPOSITION: GAS BBr3 ... x PRESSURE: W POWER: 125 DISCUSSION: and thin films. The oxide was formed by anodization Al, aluminum of A12O3/A1N (100) on or aluminum evaporated on silicon plates wafers containing an SiO2 deposited SST film: Al/SiO2/Si(100) structure, which was given thin 1 min treatment in nitrogen prior a to after BBr3 etching. RIE ionized gas etching used in studying etch reactions of aluminum and aluminum nitride oxide, and aluminum. A(3),962(1985) A Hess, D W — J Vac Landaner, Technol & REF: Sci Jacquet, P — Met Corros, 18,198(1943) AL-0056: specimens. A polish etch for aluminum. Use at Al, V and 0.8—2.5 A/cm2 or 22—25 3—4 Agitate during etching to prevent irregularities developing as the degree of A/cm2. be affects of etch figures. Should development preferentially etched immediately after polish cleaning surfaces to prevent growth of aluminum oxide and its masking effects. AL-0059b: Ibid. specimens. By the current of this solution toward the end of the etch period Al, raising and etched. can be aluminum both copper AL-0076 NAME: TIME: 30—60 min ETCH Abrasive polish TEMP: TYPE: Abrasive, RT COMPOSITION: x ... abrasive, paper DISCUSSION: Al, and alloys. Mechanical polish of specimens for metallographic study. specimens Cement abrasive cloth in a bowl and use an electromagnet for vibration. (Note: This is an "race to grinding methods using a cylinder sphere track" with nitrogen gas as the similar movement agent against abrasive paper.) REF: Krill, M — Met Abstr, 8,641(1958) F Krill, FM Prog, 700,81(1956) AL-0080: —Met and specimens similar work as in AL-0076. Al, alloys, AL-0077 NAME: ETCH TIME: Acid, machining TEMP: TYPE: COMPOSITION: 4mg NaOH ... ml ... 1000 H2O 200 ml ... glycerin DISCUSSION: Al, specimens. A method of chem/mech etching and forming parts. System has an wheel abrasive an etch tank with above working-edge vertical. Specimen is held wheel against the wheel as it is rotated through the etch solution in the tank below. (Note: This is © 1991 by CRC Press LLC

115 102 CRC of Metal Etchants Handbook to using grinding wheel with a liquid coolant.) similar a J D Greenough, O B — & Inst Met, 87,1(1958—59) Fegredo, REF: M M & Watanabe, J—Sci Rep Res Inst Tohoku UnivSer. A, 8,230(1956) AL-0078: Yamamoto, A specimens. on acid saw cutting of materials. Al, report AL-0081 NAME: ETCH 15 sec TIME: cleaning TEMP: Acid, TYPE: RT COMPOSITION: 2...HF 3 ... HNO3 ... HC1 9 5 ... H2O DISCUSSION: Al as the metal source in growing AlGaAsP single crystals. Aluminum material used GaAs, cleaned solution shown before melting with the GaP, and GaAsP material to was in aluminum produce single crystal ingots. doped REF: A — JpnJ Appl Phys, 22,109(1984) Fujimoto, AL-0082a ETCH BRM TIME: NAME: Halogen, removal TEMP: Warm TYPE: COMPOSITION: x ... 10% Br2 x ... MeOH DISCUSSION: Al foil with an A12O3 thin film grown in a solution of 40% NH4B5O8.4H2O:60% ethylene glycol at The BRM solution was used to dissolve the foil leaving oxide flakes. The RT. H3PO4:3%CrO3 also from foil with 5% stripped (ALO-0020). Aluminum foil was oxide was in a study of AC etching. used Dyer, & K REF: Alwitt, R S — J Electrochem Soc, 128,300(1981) C AL-0082b ETCH Hydrochloric acid TIME: NAME: Electrolytic, TYPE: TEMP: 60°C preferential COMPOSITION: ANODE: Al x ... 1 M HC1 CATHODE: Carbon w/25 mA/cm2 + 5 sinusoidal Hz applied current POWER: rms 700 mA/cm2 DISCUSSION: foil used in a Al, of change with AC etching. The solution produces a high density study of cubic pits. After etching, rinse in DI water, then MeOH. Pre-treat foil before electrolytic with etching x%NaOH, 10 min and follow with heavy water rinse. REF: Ibid. © 1991 by CRC Press LLC

116 103 AL-0083a-b NAME: TIME: min ETCH 40 cutting TYPE: TEMP: Acid, RT COMPOSITION: ml HC1 (2) 1 ... HNO3 200 ... (1) FeCl3 50 ... H2O g ... 1 ... H2O ml 250 DISCUSSION: 78" thick. Terylene thread soaked in Al, (1) used to cut aluminum, specimens solution and Solution (2) used to cut tin and zinc. {Note: Excellent review copper. metal brass, of methods.) growth REF: Honeycombe, RWK —Met Rev, 4,1(1959) AL-0019b NAME: TIME: ETCH Acid, TYPE: TEMP: removal COMPOSITION: (1) H3PO4 (2) x ... x% KOH x ... HNO3 x ... K3Fe(CN)6 x ... ... x ... K2B4O7.4H2O x HAc DISCUSSION: thin film on (100) silicon wafers. Solutions used for pattern etching Al with aluminum photolithography. (1) will cause COP type photo resists to lift; solution (2) will Solution affect the resist. not 15,962(1978) Reynolds, — J Vac REF: Technol, R Sci AL-0089 ETCH NAME: RIE TIME: TYPE: Gas, removal TEMP: COMPOSITION: GAS 24 SCCM FLOW: x ... PRESSURE: 75 mTorr (10 (1) SiCl4 ... Pa) x (2) SiCl4/O2 ... BaCl3/O2 ANODE: (3) x V x CATHODE: - 180 O2 (4) ... 0.26 W/cm2 POWER: DISCUSSION: Al thin deposited on silicon substrates using tungsten as an evaporation film mask. films Gas study sputter etching of aluminum thin films. A mixtures (2) and (3) with O2 plasma of develop SiO2 films as does pure O2 (4). Etch rate of the SiO2 and W films are approximately equal. SiCl4 rate was 700 A/min for aluminum. etch Degenkolb, Socf O — J Electrochem REF: 129,1150(1982) E AL-0088 ETCH Acetone TIME: Variable NAME: TYPE: lift-off TEMP: RT to warm Ketone, COMPOSITION: x CH3COCH3 ... DISCUSSION: Al thin films evaporated on glass substrates for four different thicknesses as step- study evaporation photo resist mask patterns. A through of aluminum structure and reactions. © 1991 by CRC Press LLC

117 104 CRC of Metal Etchants Handbook used to excess aluminum and photo resist after evaporation. Acetone lift-off K — Phys Soc Jpn, 4,1434(1984) J REF: Mizuno, AL-0092 TIME: NAME: ETCH removal TEMP: TYPE: Gas, COMPOSITION: ... Br2 (2) x ... Cl2 (3) x ... CC14 (4) x ... CBr4 (1) x DISCUSSION: thin films evaporated on quartz substrates in a Al of etching aluminum thin films study by sputter in ultra high vacuum (UHV). E-beam A(2),790(1985) Park, al — J Vac Sci Technol, et REF: S AL-0087 ETCH NAME: TIME: Electrolytic, polish TEMP: TYPE: ANODE: COMPOSITION: CATHODE: POWER: DISCUSSION: general high purity, dislocation free specimens used Al a as study of such material. in Solution used not shown. REF: Howe, S & Elbaum, C — J Appl Phys, 32,742(1961) AL-0090: Elbaum, — J Appl Phys, 31,1413(1960) C for electropolish used in AL-0087. Reference solution AL-0091 NAME: ETCH TIME: TYPE: Acid, thinning TEMP: COMPOSITION: DISCUSSION: specimens chemically etch thinned for study of dislocations Al transmission electron by microscopy Thinning solution not shown. (TEM). 29,1635(1958) Robinson, L — REF: Appl Phys, D J AL-0093 ETCH NAME: Sodium hydroxide TIME: TYPE: Alkali, removal TEMP: COMPOSITION: x...0.2MNaOH light 4-... DISCUSSION: thin films evaporated on SiO2, A12O3 Al ZrO2 substrates in a study of surface and protection against chemical attack. Also studied silver thin films, TiN, Si:H and PbS. Silver thin removed with 1 M HNO3+ light. films REF: Martin, P J et al — J Vac Sci Technol, A(2),341(1984) © 1991 by CRC Press LLC

118 105 AL-0094 NAME: TIME: sec ETCH 30 selective TEMP: TYPE: Electrolytic, COMPOSITION: ANODE: Al 6.4 KI CATHODE: Al g... POWER: 0.32/1 A/mm2 & 30 ... MeOH 0.3 V DISCUSSION: as sheet, plate and rod used in a study of precipitates in the material (alloys Al alloys #5182, #2124, Prepare surfaces by lap polish using 1 jim diamond paste, #3003, #7475). etch SEM expose precipitates for selectively or TEM observation. In alloy #5182, to then Al2CoMg; Mn Mg2Si; in #2124, and in #7475, Cr. were dispersoids Hower, J — Metallography REF: 15,247(1983) (MEIJAP), AL-0095 NAME: Water ETCH TIME: float-off RT Acid, TEMP: TYPE: COMPOSITION: x ... H2O DISCUSSION: on KC1, Al, and (111) cleaved substrates as oriented thin films. Some evaporated (100) were converted to A1N by N+ ion implantation. Al on (111) KC1 was films hexagonal wurtzite structure; on (100) was cubic (100). Water was used to liquefy the KC1/A1 (fee) for study float-off and interface by TEM. (Note: A1N is hexagonal system.) film J Kimura, et al — Jpn K Appl Phys, 23,1145(1984) REF: AL-0096 ETCH NAME: TIME: TYPE: Mechanical, TEMP: deformation COMPOSITION: x ... pressure DISCUSSION: specimens a study of surface deformation in aluminum due to fatigue. Al used in J C REF: Gosselin, C M — J Appl Phys, 31,1127(1960) Grooskreutz, & AL-0098 ETCH NAME: Hydrochloric acid TIME: Electrolytic, forming TYPE: Elevated TEMP: COMPOSITION: ANODE: HC1 Pb x... CATHODE: POWER: DISCUSSION: specimens as Al:Si(20%) alloyed with the following metals: Na, Mg, Zn, Cr, Al Mn, Cu, Sn, Pb, Sb, Bi, Fe, Ni, and Co. Cd, were electrolyzed in HC1 to form single Specimens crystal silicon in the anodic slime. Three silicon crystal structures were obtained: (1) with (110): Na, and (100) granules; (2) with Mg or Mn, as prismatic crystals (111) and (111) as and as plate-like (111) with negative (3) predominate with all other metal additives. (111) A study of the crystal structure of silicon in aluminum-silicon alloys. (Note: Pure aluminum an alloyed to form p-n junctions produces silicon Al:Si mixture containing needle to into blade-like silicon elements in a fine grained aluminum matrix.) N REF: I & Komatso, Obinata, — Metall Abstr, 8,94(1958) © 1991 by CRC Press LLC

119 106 CRC of Metal Etchants Handbook AL-OlOOa ETCH TIME: NAME: Abrasives polish TYPE: TEMP: Mineral, RT COMPOSITION: A12O3, ... powder x x ... H2O DISCUSSION: Solution for general cleaning and polishing. Alumina, as fine ground Al, and alloys. sub-micron water with or without glycerin: (1) as slurry grits, Linde A and B; a in powder as alumina in a colloidal suspension of water. With addition of a 1—5% KOH or (2) solution become acid slurry, and slurry particles of alumina slowly reduce to a fine paste these an Linde cleaning used with and without KOH for aluminum parts surface use. during abrasives Both fine alumina and silica for polishing. surface polishing. Used on aluminum and colloidal in alloy in material studies and specimens cleaning vacuum parts. and aluminum Walker, P & REF: M — Studies/Vacuum Parts (1981—1985) Menth, AL-OlOlb NAME: Water ETCH TIME: oxidation TYPE: to boiling TEMP: Acid, Hot COMPOSITION: H2O ... x DISCUSSION: water used to form a Al oxide on aluminum, then remove with specimens. DI hydrated HF solution for surface cleaning. Used in preparing aluminum slugs prior to use in or BHF evaporation, for general parts cleaning and aluminum and aluminum alloys. metal of REF: Ibid. ALUMINUM AIM ALLOYS, does Aluminum form metal alloys in nature and not not occur as a native General: does although there are well over 200 single crystal minerals containing aluminum element, as oxides, phosphates, and sulfates. There also are mineral hydrates. silicates, shown artificial As in the general formula aluminum above, M = Au, Ag, Be, alloys, Zn, and other metal elements. Pure aluminum is soft, like pure copper and gold, such that it is used as the pure metal for construction parts. Several alloys have specific names, not as aluminum-silicon (5% Si); magalum, with 10% Mg; and there are "zeppelin" such #43 and Fe, containing small percentages of Si, angles Sn, Mn, and Zn. braces, channels known containing is one of the lightest Be alloys with a density Beryllium-aluminum, 38% of 0.075 g/cm3 as compared to pure beryllium, 0.067 g/cm3, and pure aluminum, (lb/in3) 0.98 g/cm3. is another type of alloy. There are both high temperature Aluminum-bronze is brazing low temperature solders. It and worth noting that aluminum aluminum alloys is very difficult to braze or alloy itself, oxide to the presence of the inert oxide layer due that always present on surfaces is being exposed to air. after Technical Application: Both pure aluminum and aluminum-silicon(5%) are used as a p-type dopant on silicon, and evaporated contact pads are still in use for alloyed sources diodes that transistor devices, such as the silicon Sphere Alloy Zener process silicon and Al:Si(5%) fabricated Silicon SCRs, when uses with an aluminum pre-form, use pellets. as aluminum Al:Be(38%) has been used wires. an evaporated electrode on quartz contact crystal frequency blanks to reduce mass loading effects. Alx:Auy alloys produce "purple eventually plague", brittle compound that will a break and destroy electrical continuity as in devices, although it is used as a purple gold alloy for jewelry. in Aluminum are basic construction elements materials much Solid State processing alloy equipment — electrical transfer plates; cooling plates; lapping plates; high power feed-thrus © 1991 by CRC Press LLC

120 107 in systems; RF shielding; test blocks and many other similar applications. In com vacuum with other and ceramics, as package material for discrete devices as well as bination metals There for weight and radiation protection. minimum are several assemblies circuit both semiconductor compounds, such as aluminum arsenide, AlAs; aluminum aluminum alloy AlSb; and phosphide, A1P. In addition to compound semiconductors, antimonide, aluminum crystals other have been grown as single alloys for general morphological several aluminum such as Al:Au, Al:Ag, Al:Cu, Al:Ni, Al:Zn etc. study, Soluble HC1, Etching: H2SO4, alkalies, and mixed acids. in ALLOYS ALUMINUM ALUMINUM:BERYLLIUM ETCHANTS ALBE-0001 NAME: hydroxide TIME: 2—3 min ETCH Potassium cleaning TYPE: 30—40°C (warm) Alkali, TEMP: COMPOSITION: x ... 30%KOH(NaOH) DISCUSSION: as 0.060 diameter polycrystalline wire. Wire was etch cleaned Al:Be(38%), this in solution by heavy water washing and drying under an IR heat lamp prior to followed use as evaporation source for metal contact an on quartz radio frequency crystals. electrodes Evaporation was done with "U" shaped clips of wire hung on tungsten coils and, after evaporation, the was pumped to the 10"7 Torr range for 20—30 min before opening system bell jar to beryllium vapors. Material was used in evaluating improved frequency eliminate the levels due to reduced mass loading effects. and stability Walker, P — personal development, 1969 REF: ETCHANTS ALUMINUM:CERIUM ALCE-0001 NAME: Potassium TIME: ETCH hydroxide removal TEMP: Alkali, TYPE: Hot COMPOSITION: x... 30%KOH DISCUSSION: CeAl3 crystals grown by arc melting and aging at temperature. Used in a material single growth study. Also developed CeCu6 and LaCu6. Growth was as Czochralski (CZ) ingots. Included studies CeB6 and CeCu2Si2. No etch shown. {Note: Solution shown is for general on alloy aluminum etching.) Onuki, Y et al — J Phys Soc Jpn, REF: 4,1210(1984) ALUMINUM:COPPER ETCHANTS ALCU-OOOla ETCH NAME: hydroxide TIME: 30 min Sodium TYPE: Alkali, removal TEMP: COMPOSITION: ... 10% NaOH x DISCUSSION: Al:Cu, single crystal specimens used in a study of particle dispersion due to hardening. in After of surfaces, specimens were etched lap/polish this solution to remove work damage. © 1991 by CRC Press LLC

121 108 CRC of Metal Etchants Handbook reagent also used as the etch. Keller's was D & W D — Ada Metall, 8,147(1960) REF: Dew-Hughes, Robertson, ALCU-0002 TIME: ETCH NAME: TYPE: Acid, macro-polish TEMP: Boiling COMPOSITION: HNO3 5 ... 15 ...CH3COOH(HAc) H3PO4 ... 80 DISCUSSION: crystal specimens used in a Al:Cu, of the mechanisms of hardening and single study The solution will aging. surfaces and develop slip lines. polish REF: D & Robertson, W D — Acta Metall, 8,156(1960) Dew-Hughes, ALCU-0003 ETCH TIME: 30 sec to 2 min NAME: Acid, polish TEMP: 85°C TYPE: COMPOSITION: 25ml...H2SO4 ml ... H3PO4 70 ml... 5 HNO3 DISCUSSION: alloy specimens. Used as Al:Cu polish etch on Al.Cu; Al:Si, and Al. a REF: Heregue, J & Segond, R — Rev Metall 48,262(1951) (in French) ALCU-OOOlb ETCH Keller's reagent TIME: NAME: Acid, removal/polish TYPE: TEMP: #3 ASTM: COMPOSITION: ml ...HF 2 3ml...HCl 5ml...HNO3 ml ... H2O 190 DISCUSSION: single crystal specimens used in a Al:Cu, of paniculate dispersion in hardening. study Solution to remove work damage after mechanical used and polish. lap REF: Ibid. ALCU-0004: ASTM E407-70 Reference for ASTM number for Keller's reagent. ALUMINUM:GOLD ETCHANTS ALAU-0001 ETCH TIME: NAME: TYPE: Electrolytic, structure TEMP: ANODE: COMPOSITION: ... HC1O4 CATHODE: x x ... EOH POWER: DISCUSSION: Al:Au(2%) specimens. Solution used to develop precipitates in this alloy. Before elec etch trolytic remove native oxide with etching, solution shown under ALO-0014 under © 1991 by CRC Press LLC

122 109 Aluminum Etchants. Also refers to "Lenore's Solution" referencing Thomas, O — Oxide Electron-Microscopy of John Wiley & Sons, New York, 1962, 161 Transmission Metals, in alloy form of purple gold used a the jewelry trade.) This (Note: is Heimendahl, M — Acta Metall, 15,1441(1967) REF: Von ALAU-0002 NAME: regia, dilute TIME: ETCH Aqua removal RT Acid, TYPE: TEMP: COMPOSITION: HC1 ... 3 ... HNO3 1 10...H2O DISCUSSION: alloy reaction product observed on the side-walls of high power silicon Al:Au, diodes that been aluminum evaporated and gold evaporated on opposed wafer surfaces had a to appeared after power burn-in as Reaction failure mode, e.g., **purple prior dicing. Solution was used in a series of short-period etch-steps in the initial studies plague". of these compounds. This was the initial observation of this failure mode. brittle REF: Walker, — personal application, 1958 P ALAU-0003: L — personal communication, 1958 Bernstein, Al:Au thin films with various single crystal structures or as amorphous reactive films. Additional study purple plague and effects on device failure. Several articles written on of subject (1959—1962). this ALUMINUM:NICKEL ETCHANTS ALNI-OOOla NAME: Sodium hydroxide TIME: ETCH TYPE: TEMP: Alkali, removal RATE: 0.005 mg/cm2/h COMPOSITION: x...2.5MNaOH DISCUSSION: alloy electrodeposition films deposited by Al:Ni, or by nickel diffusion into thin Solution removal. for general aluminum. used — Cough, E & REF: J H D / Electrochem Soct 107,272(1960) Connor, ALNI-OOOlb ETCH NAME: TIME: TYPE: Fused removal TEMP: 700—800°C salt, ANODE: COMPOSITION: Graphite 400 g ...NaCl CATHODE: g ... KC1 560 2—10 A/cm2 POWER: 150 g ... Na3AlF6 (Cryolite) DISCUSSION: Al:Ni, alloy thin films. A form of molten flux etching and cleaning of high tem used perature point metals and alloys. Cryolite, Na3AlF6, is a natural mineral melting in primary processing ore as a aluminum reducing flux. REF: Ibid. © 1991 by CRC Press LLC

123 110 CRC of Metal Etchants Handbook ALNI-OOOlc ETCH NAME: TIME: salt, TYPE: 160—18O°C removal Fused TEMP: or Carbon COMPOSITION: ANODE: tungsten A1C13 CATHODE: 99 g ... NaCl POWER: 1—4 A/cm2 g 200 ... DISCUSSION: thin film Al:Ni, Crucible and cover were Pyrex, rather than graphite alloy coatings. in Method used to etch the alloy. ALNI-OOOla. as Ibid. REF: ALNI-0002 ETCH NAME: TIME: Acid, defect TEMP: TYPE: 5°C COMPOSITION: ... 10% x HC1O4 butyl ... cellusolve x DISCUSSION: crystal specimens used in a study AlNi2, phase change with recrystallization. single of used to develop structure. Solution Calvagrac, REF: & Fayard, M — Acta Me tall, 14,783(1966) (in French) Y ALUMINUM:SILICON ETCHANTS ALSI-OOOla ETCH Hydrochloric acid TIME: 10—30 sec NAME: Acid, cleaning TEMP: RT TYPE: COMPOSITION: (1) 1 ... HC1 (2) 1 ... HC1 1 ... 10 ... H2O H2O DISCUSSION: solutions and spherical pellets. Both pre-form have been used to Al:Si(5%), foil parts before furnace alloying of silicon (111) wafers in a hydrogen atmosphere or in clean forming gas Nj/15% H2). The alloy produces less stress in the silicon than pure (85% along and the formation of dislocations reduces the alloy front. Solution (2) aluminum preferred for light cleaning after alloying. REF: Walker, — personal application, 1966 P ALSI-0002 ETCH TIME: 30 sec to 2 min NAME: Acid, polish TYPE: 85°C TEMP: COMPOSITION: 25 ml ... H3PO4 70 ml ... H2SO4 5 ml ... HNO3 DISCUSSION: aluminum. specimens. Solution used as a polish etch on Al:Si, Al:Cu, and pure Al:Si — REF: J & Segond, R Heregue, Rev Met, 48,262(1951) (in French) © 1991 by CRC Press LLC

124 Ill ALSI-0003 NAME: TIME: ETCH preferential Acid, TEMP: TYPE: COMPOSITION: HC1 ... 5 ... 10 HNO3 ... 84 H2O DISCUSSION: alloy Al:Si, solution. Solution used to study the orientation re-growth of as an solid silicon aluminum-rich solid. Silicon showed a preferred precipitate (111) and (100) in the orientation. H S et al — Acta Rosenbaum, tall, 7,678(1959) REF: Me ALSI-0004 ETCH NAME: TIME: Acid, selective TEMP: RT TYPE: COMPOSITION: 1 HF ... ... HNO3 3 50... HAc DISCUSSION: re-growth p-n junctions in n-type Al:Si, wafers, 3—10 ft cm resistivity. alloy silicon aluminum evaporation and alloying into emitter and collector etched pits, excess After was aluminum removed to define circular pit areas. The silicon wafer or individual hand-lap remove die with the solution shown to etched aluminum and expose the internal alloy were front in a study of spiking defects in the bulk silicon caused by aluminum alloying. REF: Walker, & Waters, W P — device development, 1957 P ALSI-0005 ETCH acid TIME: NAME: Hydrofluoric micro-etch Acid, RT TYPE: TEMP: COMPOSITION: x...0.5%HF DISCUSSION: alloy subjected to different processing modifications. Solution was used to Al:Si(12%) the develop structure alterations observed. various A/B — Dig, 21(2), 19(1983) REF: Buehler Ltd Met Hume-Rothery, W — Inst Met Proc, 46,239(1931) ALSI-0007: Al.Si material. A general study of macro-etching of alloys. ALSI-0006 ETCH RF plasma TIME: NAME: Ionized selective removal TEMP: TYPE: gas, GAS FLOW: COMPOSITION: (Argon) ... PRESSURE: 1.7 Pa x CF4 x...O2 POWER: 0.5 W/cm2 RATE: 100 A/min @ 200°C DISCUSSION: doped thin film layers as interconnects on silicon devices along with phosphorus AISi, p-SiN silicon [(PSG) phosphorus silica glass]; dioxide and AlSiCu as multilayer structures. © 1991 by CRC Press LLC

125 112 CRC of Metal Etchants Handbook plasma etching used in multilevel structuring of these electrical interconnects. RF was Soc, H — J Electrochem al 130,645(1983) REF: Kotani, et ALSI-OOOlb Hydrogen TIME: ETCH NAME: cleaning 500°C Gas, TYPE: TEMP: COMPOSITION: H2 x... DISCUSSION: .010 diameter used to fabricate AlSi(5%) Alloy Zener diodes. The silicon spheres Sphere were held in a graphite assembly for furnace alloying, and the spheres were hydrogen wafers fired as cleaning step immediately before alloying. After alloying, individual diodes in a a plotted array for leakage current and measured to determine segregation and hexagonal were areas in the silicon wafer. Results used to improve Float Zone (FZ) defect growth of ingot zener material. Ibid. REF: ALSI-OOOlc ETCH NAME: TIME: 2—3 sec Acid, selective TYPE: RT TEMP: COMPOSITION: 1 ... HF 10 ... HNO3 5 ... H2O DISCUSSION: Si, wafers used to alloy Al:Si(5%), .010 diameter spheres as Sphere Alloy Zener (111) lightly After to testing and dicing, wafers were prior etched in the solution diodes. alloying, to optimize electrical parameters. shown Ibid. REF: ALSI-OOOld NAME: gas TIME: ETCH Forming Gas, alloying TEMP: 800°C TYPE: COMPOSITION: x ... 85% N2 x... 15% H2 DISCUSSION: Al:Si(5%) and "quad-alloy" (Al:Si:Ag:In) flat preforms about 10 mil thick used in assembly of SCRs. Belt furnace used to alloy pre-forms to moly discs prior to alloying silicon hydrogen wafers. forming gas (FG) and pure Both were used with a graphite heater SCR strip to strip/remove remaining metal alloy from moly discs for re-use of discs. REF: (1974) Ibid ALUMINUM:SILVER ETCHANTS ALAG-0001 ETCH NAME: TIME: TYPE: Alkali/acid, removal TEMP: COMPOSITION: (1) x ... 3#NaOH (2) x ... HNO3 © 1991 by CRC Press LLC

126 113 DISCUSSION: as both and single crystal ingots. Wafers were cut and lapped, Al:Ag, polycrystalline The in followed by washing in solution (2). (1), material was used in etched solution then of precipitates in cold-worked specimens. Both Al:Ag and Al:Zn a were studied. study alloys Jan, P — J Appl Phys, 26,1291(1955) REF: J ETCHANTS ALUMINUM:ZINC ALZN-0001 TIME: ETCH NAME: TYPE: removal TEMP: Alkali/acid, COMPOSITION: (1) ... 3 N NaOH (2) x ... HNO3 x DISCUSSION: were as and single crystal ingots. Wafers polycrystalline cut and lapped, Al:Zn, both then in solution (1), followed by washing in solution (2). The material was etched in used a of precipitates in cold-worked specimens. Both Al:Ag and Al:Zn alloys study studied. were REF: J P — Jan, Appl Phys, 26,1291(1955) J ALZN-0002 ETCH NAME: TIME: TYPE: Electrolytic, TEMP: 30°C polish ANODE: Al:Zn COMPOSITION: HC1O4 3% CATHODE: ... butoxyethanol POWER: 25 30% ... V ... MeOH 5% DISCUSSION: alloy sheet. Blanks were punched from sheet and then annealed. A Al:Zn(10%), system twin-jet used to electropolish specimens. was Chem Nicholls, W & Jones, L P REF: / Phys A Solids, 44,696(1983) — ALUMINUM:ZINC:COPPER ETCHANTS AZC-0001 ETCH NAME: Heat TIME: TYPE: Thermal, preferential TEMP: COMPOSITION: x heat ... DISCUSSION: and were homogenized by annealing specimens aging. Cubic shaped Al:Zn,Cu, alloy etch spiral observed parallel to the cubic axis after thermal annealing. (Note: The patterns z-axis direction as (001).) Fiz REF: N & Shehegolrva, TV — W Metalloved, 5,566(1957) Bulnov, ALUMINUM IRON ETCHANTS ALFE-0001 ETCH NAME: TIME: TYPE: cleaning TEMP: Solvent, COMPOSITION: 80 ... acetone 20 ... toluene © 1991 by CRC Press LLC

127 114 CRC of Metal Etchants Handbook DISCUSSION: AlFe used for selective oxidation. Degrease specimens in solution shown alloy specimens before oxidizing. REF: & Seybolt, A U — J Electrochem Soc, 106,582(1958) R Grace, E ALUMINUM OF PROPERTIES PHYSICAL AlSb ANTIMONIDE, Classification Antimonide numbers Atomic 13&51 Atomic weight 148.73 Melting point (°C) 600—700 Boiling point (°C) 4.67 (g/cm3) Density Hardness scratch) — (Mohs 3—4 (isometric structure Crystal — tetrahedral) (111) tetrahedron grey Color (solid) Silver (dodecahedral) Cleavage (110) ANTIMONIDE, AlSb ALUMINUM Does not as a natural compound, although there are other metal anti- General: occur as of and silver as mineral species, nickel, well as mixed metal antimonides. monides copper, is no application of There compound in the metal industries, at the present time, but the some in the fabrication of glass and silicates. use compound Application: material is a III—V Technical semiconductor that has been The grown by the Horizontal Bridgman (HB), and Czochralski (CZ) methods. Like the arsenide, the antimonide readily when exposed to moisture in air. Both materials are processed oxidizes to held solvents or in inert gas atmospheres liquid prevent oxidation. It also has and under deposited as a thin film layer by CVD. As a been film layer element of a device, it thin has fabricated as solar cells. been HC1:HNO3. Mixed Etching: HF:HNO3, HF:H2O2, and acids of ALUMINUM ANTIMONIDE ETCHANTS ALSB-OOOla ETCH NAME: TIME: TYPE: Acid, TEMP: polish COMPOSITION: x H2O2 ... DISCUSSION: as cut wafers. All AlSb and handling of aluminum antimonide should be processing under an inert, dry atmosphere such as argon or nitrogen, as this compound is attacked by abrasive atmospheric lap and polish with Mechanical slurry under oil. Etch polish moisture. with the solution shown. — REF: A et al Herczog, / Electrochem Soc, 105,533(1958) © 1991 by CRC Press LLC

128 115 ALSB-OOOlb NAME: TIME: ETCH polish Acid, TEMP: TYPE: COMPOSITION: HF x ... ... HNO3 x (HAc) ... x CH3COOH DISCUSSION: cut wafers. Solution used to polish wafers. See additional discussion AlSb as under ALSB-OOOla. REF: Ibid. ALSB-0002a NAME: 1 min ETCH TIME: polish TEMP: RT TYPE: Acid, COMPOSITION: ... HC1 4 4... HNO3 1 ... H-tartaric acid DISCUSSION: AlSb Used as a polish etch in studying copper diffusion in aluminum antimonide. wafers. Follow with a 2—3 sec dip in 1HC1:1HNO3 to remove smut residue left on surfaces etching etching. after Wieber, R H et al — J Appl Phys, 31,600(1960) REF: ALSB-0003 ETCH TIME: 5 min NAME: Acid, TYPE: TEMP: polish COMPOSITION: 1 ... HNO, 1 ... HC1 DISCUSSION: AlSb Wafers were mechanically lapped with 303V2 abrasive grit on an iron lap wafers. with kerosene liquid carrier, before etch polishing the the solution shown. Material with as in a study of elastic constants. used 31,46(1960) REF: I & Menes, M — 7 Appl Phys, D Bulef, ALSB-0002b: Wieber, E H — J Appl Phys, 31,608(1960) AlSb, wafers used in a study of copper diffusion in the material. Solution used at RT, 2—3 sec a final cleaning/polish etch. as ALSB-OOOlc ETCH TIME: NAME: Acid, polish TEMP: TYPE: COMPOSITION: x ... HF x ... HNO3 DISCUSSION: for AlSb Various concentrations of HF and HNO3 are polish solutions wafers. this material. See additional discussion under ALSB-OOOla. REF: Ibid. © 1991 by CRC Press LLC

129 116 CRC of Metal Etchants Handbook ALSB-0006 ETCH NAME: TIME: macro-etch TYPE: TEMP: Acid, COMPOSITION: HC1 1 ... 1 HNO3 ... DISCUSSION: referenced author describes AlSb as a macro-etch of aluminum anti- wafers. The this Bulef & Menes monide Fibers of Al3Ta, 1—5 \im in diameter, were (See ALSB-0003). in AlSb after etching as Al3Ta is the in this etch solution. Under high observed insoluble the surface etch pits are similar to those observed in magnification compound semi other conductors. Gorton, H — J Electrochem Soc, 107,248(1960) REF: C ALSB-0007 NAME: ETCH TIME: stain TEMP: TYPE: Acid, COMPOSITION: g 10 ...FeCl3 ... HC1 100 ml H2O ml... 1000 DISCUSSION: wafers from AlSb/GaSb ingot grown as a solid solution alloy single crystal. Wafers an were under anhydrous benzene. The acid solution shown was lapped mechanically to used etch stain surfaces in a structure study. REF: Miller, J F et al — J Electrochem Soc, 107,527(1960) ALSB-0008a-b ETCH TIME: (1) 1 min (2) 2 sec NAME: Acid, preferential (1) 25°C (RT) (2) 25°C TYPE: TEMP: (RT) COMPOSITION: HNO3 HF (2) 1 ... 1 (1) ... H2O2 1 ... HC1 1 ... ... H2O 1 DISCUSSION: AlSb, wafers. Solutions used for preferential etching to develop etch pits and other (111) antimonide in general study of aluminum a growth structures. Rotation of tetra- structures hedral etch pits show polarity between (lll)A and (lll)B surfaces of wafers. REF: Gatos, C & Lavine, M C — J Electrochem Soc, 107,427(1960) H ALSO-0009 ETCH TIME: NAME: Acid, TEMP: TYPE: polish/removal COMPOSITION: ... 1 HNOS 1 ... HC1 DISCUSSION: AlSb wafers, as grown p-n junction diodes. Etch was used to develop dendritic filaments direction of (?). Filaments were 1—5 \ua long and parallel to the growth Al3Te2 of the ingot. (See ALSB-0003). REF: Gorton, HC-7 Electrochem Soc, 107,248(1960) © 1991 by CRC Press LLC

130 117 ALSB-OOlOa-b NAME: TIME: ETCH cleaning Acid, TEMP: TYPE: COMPOSITION: ... (2) 30 ... HF H3PO4 (1) 95% 50 ... 5% ... HNO3 HNO3 HAc ... 30 0.5 ... Br2 DISCUSSION: material preparation. Both solutions used to AlSb, oxides and for general ingot remove Solution used on aluminum: solution (2) (CP4) on antimony. Both materials cleaning. (1) mixing DI after etching prior to water for ingot growth. rinsed in Allred, W P et al — J Electrochem REF: 107,117(1960) Soc, AlAs ARSENIDE, ALUMINUM PHYSICAL OF PROPERTIES Arsenide Classification 13&33 numbers Atomic 100.98 Atomic weight 800—900 point Melting (°C) (°C) point Boiling (g/cm) Density 6—7 (Mohs Hardness — scratch) tetrahedron (111) tetrahedral) — (isometric structure Crystal silver Grey (solid) Color (110) (dodecahedral) Cleavage ARSENIDE, ALUMINUM AlAs Does not occur as a natural compound, although there are four minerals General: as arsenates aluminum with iron, manganese, or of all of which are hydrated. There copper, are natural mineral arsenides of bismuth, cobalt, copper, iron, nickel, and platinum. There is no of the compound in the metal industries though as an artificial compound or as use in individual are used as additives they the glass industry. the elements Application: The material is a HI—V compound semiconductor, and has been Technical by Horizontal grown Bridgman (HB), Czochralski (CZ) methods, or from a Molten Flux the material (MF), a mixed GaAs:AlAs crystal. The include is hygroscopic to the degree that to it will react with moisture when exposed to air, oxidizing rapidly. The oxide then forms a held stable film. To prevent oxidation, wafers are processed and surface under passivating inert atmospheres, such as nitrogen, argon, or helium. As a Solid State device, the compound has been fabricated as electroluminescent diodes and solar cells. Mixed acids, HF:HNO3, Etching: halogens. and ALUMINUM ARSENIDE ETCHANTS ALAS-0001 ETCH NAME: BRM TIME: TYPE: Halogen, polish TEMP: COMPOSITION: x...0.5%Br2 x ... MeOH © 1991 by CRC Press LLC

131 118 CRC Metal Etchants Handbook of DISCUSSION: thin on (100) gallium arsenide substrates. The substrates were films AlAs, deposited solution will prior to growth of AlAs. The AlAs surface the oxidize on polished in shown be air within 24 h. AlAs also can stabilize etched in the solution shown. to exposure and hold Process N2 to prevent oxidation. and under Gordon, L et al — / Electrochem Soc, 119,992(1972) REF: N ALAS-0002 NAME: TIME: ETCH Air TYPE: Gas, oxidation TEMP: RT COMPOSITION: Air ... x DISCUSSION: wafers cleaved from an oriented AlAs,(l and as single crystal spheres. Surfaces 10) ingot, to stabilize in air. A major study of microcleavage, bonding character, and surface allowed in structure tetrahedral form as aluminum, gallium, indium antimonides, ar materials of phosphides. and senides, A & Broder, J Wolff, — Acta Crystallogr, 12,313(1959) REF: G D OF PHYSICAL PROPERTIES ALUMINUM NITRIDE, A1N Classification Nitride numbers Atomic 13 & 7 40.98 weight Atomic 2400 Melting point (°C) point Boiling (°C) 3.05 Density (g/cm3) 1.9—2.2 Refractive index (n = ) 6.3 Band gap (eV) of Coefficient thermal expansion or 4.2/5.3// J. c-axis (xlO-6cm/cm/°C) + 7 scratch) Hardness — (Mohs 3500 — (Vicker's kfg/mm2) structure hemimorphic) — (hexagonal Crystal (1120) prism Yellowish (solid) Color (1120) distinct) Cleavage (prismatic — ALUMINUM NITRIDE, A1N Does not as a natural compound. There are no metallic nitrides in nature, General: occur The are nitrates and nitrites of importance. many metal industries have used although there nitridization process for years: firing metals above the in a nitrogen atmosphere to 1000°C form surface nitrided skin that acts as a surface hardening agent, and is more stable a to corrosion. as Application: material has been Technical The a thin film by evaporation deposited of aluminum in a nitrogen atmosphere. In Solid State device development, it is under evaluation as protective surface coating similar to that of silicon dioxide and nitride. It a structure has epitaxially as both a crystalline grown and single crystal by RF sputtering been of an aluminum plate in a nitrogen atmosphere. It is both a dielectric and piezoelectric as material to alpha-quartz, SiO2 and, as an epitaxy thin film, has been fabricated similar a acoustic wave device. surface Etching: HF; hot H3PO4, and hot alkalies. © 1991 by CRC Press LLC

132 119 ALUMINUM ETCHANTS NITRIDE ALN-0001 ETCH acid TIME: Variable NAME: Hydrofluoric removal/cleaning TYPE: TEMP: Acid, RT COMPOSITION: HF cone. (2) 1 ... HF (3) x ... HF, ... (1) 1 H2O 10 ... H2O ... 1 DISCUSSION: thin films deposited on (111) silicon wafers by A plasma sputter deposition. Used IN, RF a study of the material. Films were 1000—2000 A thick as deposited. Films development in the photolithographically and etch patterned with processed solutions shown in a then were study of etching and cleaning of this material. This was general of the original work some done A1N thin films deposited by DC sputtering of a silicon target in nitrogen. on Hersch, N Walker, P — original development, 1966—1967 REF: & ALN-0002 NAME: acid TIME: Variable Hydrofluoric ETCH removal TEMP: Boiling TYPE: Acid, RATE: 170 mils/year COMPOSITION: HF 1 ... ... H2O 1 DISCUSSION: specimens. The removal rate shown was computed after etching aluminum nitride A1N, this solution. A1N is unaffected by mineral acids. in — Taylor, M & Lenie, C REF: J Electrochem Soc, 107,308(1960) K ALN-0003: Kohn, J A et al — Am Mineral 41,355(1950) A1N, specimens. in ALN-0002, above. Referenced Renner, Von —ZAnorg Algem Chem, 298,22(January 1959) ALN-0004: Th. Referenced A1N-0002, above. specimens. in A1N, G & Fuster, L M — J ALN-0005: Ceram Soc, 42,53(1959) Long, Am specimens. Referenced in ALN-0002, above. A1N, AIN-0006 NAME: Phosphoric ETCH TIME: acid TYPE: removal TEMP: Hot Acid, COMPOSITION: x H3PO4 ... DISCUSSION: thin films deposited as surface passivation on (100) gallium arsenide A1N, substrates as: Solution used after photo resist AlN/SiO2/GaAs(100). to remove the A1N layer. patterning REF: Naki, K & Ozeki, M — J Cryst Growth, 68,200(1984) ALN-0008a: Chu, L & Kelm, RWJr-7 Electrochem Soc, 122,995(1975) T thin as deposits. Solution used A1N, a general etch. film ALN-0013: Y et al — J Electrochem Soc, 129,1045(1982) Pauleau, A1N, thin films grown by CVD in a study of composition, kinetics and growth mech was anisms. at 45°C gave a rough surface; growth at 850°C a smooth surface. Etch Growth with used 65°C and removal rate varies at growth temperature of the deposit. © 1991 by CRC Press LLC

133 120 CRC of Metal Etchants Handbook ALN-0007 ETCH TIME: NAME: Heat preferential TYPE: TEMP: Thermal, COMPOSITION: heat (electron) ... x DISCUSSION: formed after aluminum A1N, on NaCl (100) substrates by im thin films evaporation N+ ions. The thin films were removed from the plantation by water float-off of substrate morphological with a high power electron microscope (HVEM) which was used for study the annealing in observing physical changes in an thin film. A1N is hexagonal as vehicle in structure; has a Vicker's hardness of 3500 kgf/mm2; a band gap of 6.3 eV, and wurtzite melting a of 2400°C. point Rauschbach, B al — Thin Solid Films, 109,37(1983) REF: et ALN-0008b NAME: hydroxide TIME: ETCH Sodium removal TEMP: RT to TYPE: (80°C) Alkali, hot COMPOSITION: x ... 10—30% NaOH (KOH) DISCUSSION: amorphous thin films deposited on Si and GaAs substrates. A1N, used as a Solution general {Note: 2—5% concentrations can be used for surface cleaners at RT and as etch. development with pin-hole A1N.) solutions Ibid. REF: ALN-0009 NAME: Water TIME: ETCH Acid, TYPE: TEMP: float-off COMPOSITION: x ... H2O DISCUSSION: A1N, thin film (100) and (111) oriented were fabricated for TEM study as follows: potassium chloride, single crystal substrates of (100) and (111) orientation were me KC1, polished; polish in water, rinsed in acetone, and nitrogen dried. Single chanically etched (100) aluminum on (100) KC1 was evaporated: single and sphalerite structure crystal was on (111) KC1 was (111) wurtzite structure (hexagonal). The (isometric); was ion aluminum implanted nitrogen to form aluminum nitride films. Films were removed for TEM study with milling the substrates with water. by Jpn Kimura, REF: al — K J Appl Phys, 223,1145(1984) et ALN-0015: Ritajima, M et al — J Electrochem Soc, 128,1588(1981) A1N, thin deposited on molybdenum substrates by RF reactive ion plating (RIP). films forms formed. 100—1200°C; at 750°C MoO3 is A1N Above 1200°C N2O3 develops. at Authors say is unstable in water vapor. A1N ALN-0010 ETCH NAME: Hydrofluoric acid TIME: TYPE: Acid, removal TEMP: RT COMPOSITION: ... HF, cone. x DISCUSSION: A1N, thin films deposited on GaAs:Zn doped, (100) wafers used in a study of Zn+ ion were implantation (F) annealing. After implant, wafers with surface coated with either A1N © 1991 by CRC Press LLC

134 121 or a cap prior to annealing. Both thin films were removed after anneal with the Si3N4 as shown. solution Appl al — J K Phys, 57,5470(1985) REF: et Moser, P et al — J Appl Phys, 32,1098(1961) ALN-0011: Delavignette, Electron microscope used for direct observation of dislocations and A1N, specimens. faults. stacking — J et al ALN-0012: J Appl Phys, 57,5470(1985) N Barrett, deposited as a thin film on GaAs ion implanted with zinc in a study of annealing. A1N, implant. A1N used as "caps" after ion were After annealing cycles, A1N Si3N4 Both and HF. removed with ALN-0013 NAME: ETCH TIME: TYPE: removal Acid, TIME: COMPOSITION: x acids/alkalies/halogens ... DISCUSSION: used in an evaluation of cohesive energy features of tetrahedral A1N, single crystals solutions vary the compounds listed below: with Etchant semiconductors. A1N BN CdTe Ge HgSe Si BeO AlAs ZnS AlSb HgTe *CuCl GaP *CuBr ZnSe A1P GaAs *Agl ZnTe *CuI GaSb *CuGaSe2 ♦AgGaSej *ZnSiF2 CuInSe2 InP *ZnSnAs2 ♦AglnSe^ InAs *CuGaTe2 *MgS *AgGaTe2 InSb CuInTe2 *AgInTe2 *MgSe *CaSiF2 Sn, grey CdS *MgTe This also listed under these individual compounds to include etchant solutions. reference solutions under shown Use the individual compounds. as J Aresti, et al — REF: Phys Chem Solids, 45,361(1984) A PHYSICAL PROPERTIES OF ALUMINUM OXIDE, A12O3 Classification Oxide Atomic numbers 8 & 13 weight Atomic 102 Melting point (°C) 1725 (°C) Boiling point 2250 (2050) Softening point (°C) 2050 (g/cm3) Density (*3.955—4.10) 3.9 25°C Thermal conductivity (cal/sec/cm/°C) 0.077 ~6 cm/cm/°C) of thermal expansion (x Coefficient 10 6.6 heat (cal/g/°C) 25°C Specific 0.25 (kg/cm2) strength Compressive 24,000 Compressive 10 ~10) x (dynes/cm2 strength 1.2 © 1991 by CRC Press LLC

135 122 CRC of Metal Etchants Handbook strength (dynes/cm2 109 @ 1.0 Compressive x atm) 750°C N2 (kg/cm2) 4800 Modulus rupture of kHz) constant Dielectric 25—500°C (1 9.87—10.93 500°C/1000°C 106 x mm2/cm) Electrical resistance 1011 (ohms 55 106) modulus Young's (x x Flexural 50 strength (psi 103) (Charpy in/lb) 7 Impact resistance — 230 (volts/mil) strength Dielectric strength (psi x 103) 30 Tensile (1 kHz) 25—500°C 0.0007 Dissociation factor (1 factor 25—500°C 0.0076 Loss kHz) (n Refractive (1.65) =) index 1.77 scratch) — 9 Hardness (Mohs 2000 (1370) (Knoop — kgf/mm2) 1650 kgf/mm2) — (Vicker's (hexagonal — rhombohedral) Crystal (1011) rhomb structure alpha — beta (100) cube (isometric normal) — White/black/grey/brown/blue (solid powder/sxtl) Color only, Cleavage cubic) (0001) or (001) (basal-parting or Artificial alumina, 99.98%, except Note: noted (*). where ALUMINUM AI2O3 OXIDE, Occurs in as the mineral corundum. Though it is hexagonal system, General: nature elongated normal often occurs in it pseudohexagonal prisms division, class, rhombohedral laminated structure; also massive, granular with near with parting (pseudo- a rectangular on and (1011). Fracture is uneven (0001) conchoidal (glassy materials). It is cleavage) to to diamond (H = 10) in next vs. H = 9 for corundum with a high specific gravity hardness, (density) = 3.95—4.10. Color range is blue, red, yellow, brown, and grey. It is opaque, G to index, as sapphire. Refractive translucent n = about 1.76, varying with axial transparent with direction. are three major divisions, There subspecies, all of which are measurement important in industry. As single crystals: (1) sapphire (blue); (2) ruby (red); (3) Oriental topaz (yellow); Oriental emerald (green); (5) Oriental amethyst (purple) and (6) star (4) with an structure on the (0001) due to cavities parallel to bulk prism sapphire, asterated and gemstones. are the two precious Sapphire The others are semi-precious planes. ruby may stones, sapphire with fine color (bluish) star be classed as precious. gem though as artificial materials both ruby and sapphire were Industrially, grown as ingots initially (boules) the Verneiul process in the late 1800s for gem stones and, the ruby laser, by in commercial mid-1950s, was the first developed laser unit. It is worth nothing that the internal natural rubies can be differentiated by artificial structure observable with a 20 x and lens. Internal growth lines in natural material are angular; in artificial stones, curved. This is true for other mineral. any of (common) varieties with dull colors opaque blue, grey, brown, and Corundum: the It has been produced artificially with a melting black. of 2050°C, as single crystals point from liquid fluxes, such as lead several or sodium sulfide. The artificial abrasive oxide alundum is made by heating bauxite (a hydrated alumina ore) in an electric furnace at 5000 type to occurs in four forms, but the alpha-corundum It is the only one stable at 6000°C. high temperatures. Alumina, A12O3 — corundum — is one of the most inert compounds known, second upon only quartz, SiO2 in nature. It is not acted to by single acids, though some acid mixtures © 1991 by CRC Press LLC

136 123 have been When finely powdered and treated with cobalt solutions it gives a developed. blue color. beautiful it industry as a high temperature ceramic and is fabricated as pressed is In classified alumina tube, forms from a mixture of powdered other with silica rod, and powder sheet, For very high purity alumina, 99.6%, the silica as removed by heat treatment. a binder. is a variety of alumina-based ceramics containing wide metal oxides that have are There other for special applications. Highest been alumina is white in color, followed developed purity grey light tan, and there is a black variety containing graphite. It has wide industrial by to an stand-offs, telephone lines, furnace liners and tubes, electrical as applications insulator: A and Spheres are used as beads, beads in hot acid solutions. rods. thermocouple boiling application is as a lapping and polishing abrasive. major is a natural mixture of corundum and magnetite or hematite, both iron ores. Emery dark grain with gradation of Usually size from very fine to coarse and occasionally black embedded single of corundum. The primary industrial use is an abrasive containing crystals as best common emery (one form or Arkansas stone). emery, (Turkish quality), There are several major uses of alumina and alumina-based Technical Application: in Solid processing and device fabrication: ceramics State heat parts: either General both electrical and As insulators in vacuum systems and 1. or test equipment; furnace tubes or bead for insulation on electronic in thermocouples diffusion epitaxy systems; inert work surfaces or holders for chemical processing and beads; electrical etch solutions as boiling in and other applications. or assembly; Lapping compound: From general lapping grits (180 to 350 mesh) to fine powder 2. slurry polishing to 0.S |xm) such as Linde A and B used for (0.2 paste compounds polishing. for mechanical lap/polish of Used metals and metallic compounds. all 3. Cutting/sawing: Discs and blades with embedded alumina grit or melt-fired onto the cutting edge a blade to improve wear resistance. These have been used to wafer of semiconductor and elements. dice dielectric state 4. major element in package construction for hermetically sealed packages: Solid A is aluminum, radiation hard package. Alumina a usually the Combined devices. with the package brazed body a metal base that acts as a an electrical insulator. of onto Thin Evaporated or sputtered (CVD or RF film: as an amorphous coating on 5. plasma) surfaces as a dielectric insulator or passivation layer material it resists ionizing — radiation. used, like silicon dioxide, as a chemical etching or diffusion mask in Also memory with Also as an active resist. element in semiconductor conjunction photo assemblies. Applied to aluminum surfaces — anodizing — to produce an inert, device surface for wear protection. Anodization can be in different colors: red, yellow, hard applications, blue, black with a variety of and such as color coded buttons. brown, 6. Substrates: High purity alumina, >99.6%, as pressed powder blanks (0.005 to 0.050 thick) are photo resist patterned, and etched as electrical circuits for a wide metallized, high of devices. It should be noted that State purity alumina with a 1— range Solid |a" polish finish can be difficult to metallize without peeling of 2 metallization the during cutting or temperature processing like glass or other highly polished subsequent have surfaces. fx" substrates do not 4 this problem, but high frequency mi As-fired crowave devices require highly polished surfaces for optimum electrical parameters. 7. Resistors: wide range of discrete resistors and resistor networks are fabricated as A size alumina or on substrates. As elements and thicknesses increase the re discrete sistance values increase: 0.005/.014 thick, to about 0.060/0.080 as squares are nominal sizes. special Capacitors: Fabrication is similar to that of resistors and both can be 8. mixture to formulations other elements and oxides with obtain special electrical characteristics. © 1991 by CRC Press LLC

137 124 CRC of Meted Etchants Handbook Amorphous ruby: parts are fabricated from a liquid melt poured into molybdenum 9. Ruby produce forms wire bonding tips, and other parts. Bond tips are used flats, to rods, devices (gold, and aluminum) of discrete silver, and device assemblies. wire in bonding tubes are used for a Flats, of applications including filter elements. Ruby rods, variety are hard, inert, and high-temperature resistant ballbearings. spheres excellent alumina, the and of forms and applications of many it is still one of Regardless varied most difficult materials the etch. As will be seen in the following list of etchants where to most cleaning solutions. are Difficult. Hot and H3PO4 and some hot gases. RIE with RF plasma gases. Etching: HC1 OXIDE ETCHANTS ALUMINUM ALO-OOOla NAME: TIME: ETCH removal TEMP: TYPE: & 80°C Acid, RT COMPOSITION: ml ... H3PO4 35 ... 20 g C1O3/I DISCUSSION: A12O3, films anodized on aluminum surfaces. Anodize 5 min at 20°C and 500 V thin of 3% acid: 0.05% Borax. A study boric film structure and A12O3/A1 interfaces. in REF: Stirland, D J & Bicknell, R W — J Electrochem Soc, 106,481(1959) ALO-0021: Dyer, K & Alwitt, R S — / Electrochem Soc, 128,300(1981) C thin films on aluminum foil and used in a study of AC etching of foil. grown A12O3, Solution in NH4BSO8.4H2O: ethylene glycol, RT. 40% shown used to strip grown Oxide BRM solution (ALO-0020b) used to dissolve foil leaving oxide oxide. Solution was: flakes. 5% CrO3. H3PO4:3% Ibid. ALO-OOOlb: thin films as native oxide on single crystal aluminum ingots and wafers. Solution A12O3, used to oxide. remove ALO-0006 ETCH Water TIME: NAME: TYPE: Solvent, TEMP: cleaning COMPOSITION: x...H2O DISCUSSION: A12O3 and Al2PxOy thin films deposited on n-type InP, (100) wafer substrates to form MIS diodes an electrical parameter study. Alumina not etched — used as an insulator in 1.48— InP additional between metallization. Refractive index shown as n = and surface 1.50. (Note: Natural sapphire n = 1.765.) REF: ALO-0022 ETCH NAME: Hydrogen TIME: To 1 h TYPE: cleaning TEMP: 800—1000°C Gas, COMPOSITION: x ... H2 DISCUSSION: A12O3, pressed powder blanks with 2 \x" (polished) and 4 \x!' (as fired) surface finish. circuits Blanks in fabricating microwave electronic used with Au/TiW (10% Ti) metallization © 1991 by CRC Press LLC

138 125 by sputter and electrolytic gold up-plating. Up-plated parts subjected to 400°C, evaporation min on hot plate in air, show blistering of metallization. Hydrogen firing used to 1—5 a surfaces prior initial metallizing. Showed major reduction of blistering, clean alumina to contained eliminate. 2 |x" finish appears to not entrapped oils from diamond did but The See AU-0024 for additional discussion of this study. paste polishing. P & Valardi, N — personal development, 1985 REF: Walker, ALO-0004 NAME: etch (A-B etch) TIME: 15—20 min ETCH RCA cleaning TEMP: 80°C TYPE: Acid, COMPOSITION: (1) NH4OH (2) 1—2 ... HCI ... 1—2 H2O2 1—2 ... H2O2 ... 1—2 ... H2O 4—6 ... H2O 4—6 DISCUSSION: A12O3 powder blanks with 2 fi" (polished) and 4 p/' (as-fired) surface finish pressed and photo patterned/etched in the fabrication of microelectronic circuits. metallized resist as silicon originally developed for cleaning of solutions, surfaces (Kern The shown, were alumina, Puotinen). the system for cleaning used quartz, sapphire, and silicon: & (Walker) parts in a Teflon holder introduced place solution (1); transferred still wet to solution into (2); rinse 2 min in running DI water and N2 blow dry. Method used in a then of metal study adhesion alumina. Immediately after cleaning in on two solutions, parts were held under the MeOH until introduced into vacuum for metallization and were still wet with alcohol, or parts were water rinse, 1 min; HF dip, 30 sec; DI water rinse, 30 sec and N2 blow dry DI before introduction vacuum. Both methods gave good adhesion of sputtered immediately into metallization. Kern, & REF: DA — RCA Rev, 69,187(1979) W Puotinen, P — personal application, 1980 Walker, ALO-0015: pressed powder blanks used for microelectronic circuit fabrication. Solutions A12O3 used to surface prior to multilayer metallization. clean ALO-0005 TIME: 2—5 min acid NAME: ETCH Hydrochloric 70°C RT TEMP: or cleaning Acid, TYPE: COMPOSITION: (2) 1 .. HCI .. cone. ... x (1) HCI, H2O .. .. 1 DISCUSSION: A12O3 pressed powder substrates, 2 and 4 \i" surface finish, used in as study of metal lization. Etch substrates in either solution, rinse in running DI water, 2 min, and N2 soak on dry. blow gave good sputtered metal adhesion. Also used This fused quartz and cleaning sapphire, and single crystal sapphire substrates. REF: Walker, P — personal application, 1980—1985 ALO-0021 ETCH Hydrochloric acid TIME: NAME: Acid, TEMP: Boiling preferential TYPE: COMPOSITION: X...6WHC1 DISCUSSION: Alpha-A12O3 (0001) wafers used in a study of impurity penetration along dislocation NaCl lines. was shown that traces of both It and Mg(NO2)2 will contaminate the surface, © 1991 by CRC Press LLC

139 126 CRC of Metal Etchants Handbook along dislocation and defect structure can be developed with the solution penetrate lines, shown. Tucker, & Gibbs, P — J Appl Phys, 29,1375(1958) N R REF: ALO-0007 Steam TIME: 6+ min NAME: ETCH cleaning TEMP: 100°C TYPE: Acid, COMPOSITION: ... steam x H2O, DISCUSSION: blanks device for fabrication of metallized circuits in semiconductor substrate A12O3 used jets. Substrates mounted facing two vertical panel The top jet contains applications. are plus surfactants; the water jet, pure water. Jets are moved up and down continuously lower spraying substrates for about 6 min. Rack mounted parts are then placed in vacuum the at Au/Cu/Cr than 100°C for at least 28 min. Cleaning is done prior to ovens metal greater Authors remove that this will lization. both fingerprints and carbon. say Sci Rogelstad, & REF: G — J Vac T Technol, A3,516(1985) Matarese, ALO-0009 ETCH NAME: Argon TIME: TYPE: Ionized gas, cleaning TEMP: COMPOSITION: GAS FLOW: Ar+,ions PRESSURE: x... POWER: DISCUSSION: A12O3 used for plasma assisted physical vapor deposition (PAPVD). blanks substrate cleaned nitrides, and sulfides were carbides, by reactive sputtering (RS) Ceramics, oxides, to metal deposition by PAPVD or prior activated reactive evaporation (ARE). Over 25 by substrates metallizations described. and Bunshah, Sci F & Deshpandey, CC — JVac REF: Technol, A3,553(1985) R ALO-0010 ETCH NAME: TIME: TYPE: Acid, anodizing TEMP: COMPOSITION: ANODE: x ... 5% NaOH CATHODE: x...50%HNO3 POWER: DISCUSSION: sheet on aluminum sheet. The aluminum coating was cleaned in the A12O3 anodized solution prior above anodization. An HNO3:NH4HF solution also used. After etching, to rinse in DI H2O, then EOH. REF: Sharp, D J — Thin Solid Films, 111,337(1985) ALO-0011 ETCH Sulfamic acid TIME: NAME: Acid, TYPE: TEMP: cleaning COMPOSITION: x ... NH2SO3H DISCUSSION: a A12O3, and other ceramics. Solution is specimens cleaning acid for ceramics. Solutions © 1991 by CRC Press LLC

140 127 are acidic but with pH values lower than formic, citric, oxalic, and phosphoric strongly Also used descaling and pickling of metals. acid. for 13332-1, REF: Co. Ashland Bulletin Chemical ALO-0012 Air 30 min, minimum NAME: TIME: ETCH TEMP: TYPE: Gas, cleaning 200°C COMPOSITION: ... air x DISCUSSION: and parts both metallized and unmetallized material. If A12O3, are substrates materials for periods of time, their surfaces can become hydrated with water vapors. stored prolonged air photolithography be used, at least an to oven bake-out is recommended before Where is AZ-type photo resist lacquers to obtain better adhesion of resist. applying Brochure: Series 1300 REF: Positive Photo Resists for Semiconductors and Microelec AZ American Hoerchst 1983 tronics, Corp, P personal application, 1983 Walker, — ALO-0013: powder substrates A12O3, received" and after metallization with RF sputtered pressed **as Ti:Au or Cr:Au. Substrates were air oven baked at 150°C for 20 min; 4, 8, and TiW:Au, h 24 to gold up-plating in a study of blisters and cracking of metallization. TiW:Au prior worst which blistering showed was reduced but not eliminated with extended baking case in Alumina shipped and stored substrates individual polyethylene envelopes have time. surface oils(?) contamination. A 2 |x" finish surface contains entrapped oil from diamond paste polishing shows different blister characteristics than the as-fired 4 fx" surface. and done at on a hot plate in air. Best results were obtained when as-received 400°C Evaluation prior hydrogen at 800 to 1000°C fired to metallization. were blanks ALO-0002b NAME: Air TIME: 9 min ETCH Gas, 1470°C TEMP: TYPE: cleaning COMPOSITION: x ... air DISCUSSION: fired were Beta-Al2O3:Na temperature substrates to clean surfaces. doped high Ibid. REF: ALO-0003 ETCH Argon + air TIME: NAME: Gas, TEMP: TYPE: 1500°C preferential COMPOSITION: x Ar + air ... DISCUSSION: Al2O3:Zr(l%) doped single crystal ingots grown by the Verneuil Process. Wafers were cut basal, and mechanically polished with diamond paste on a maple wood lap with (0001) were olive the liquid carrier. No dislocations as observed in the ingot material as-grown. oil After firing in the atmosphere and at temperature shown — surfaces show asterated sixfold cavities symmetry hexagonal loops. (Note: Cylindrical and parallel to prism planes patterns produce asterism in natural corundum and polished encabachon become star sapphires.) — REF: H E et al Bond, J Appl Phys, 34,440(1964) © 1991 by CRC Press LLC

141 128 CRC of Metal Etchants Handbook ALO-0002c ETCH acid TIME: 1 h NAME: Phosphoric removal/cleaning 150°C Acid, TYPE: TEMP: COMPOSITION: x ... H3PO4 DISCUSSION: substrates were surface cleaned with this solution in addition to Beta-Al2O3:Na doped air firing. REF: Ibid. ALO-0017: the 1%) ceramic substrates and parts were Al2O3:MgO(V2%) in Al2O3:TiO(l and cleaned shown at 200°C. solution ALO-0014 " ~~ NAME: TIME: 30 sec ETCH Acid, oxide TYPE: TEMP: 60°C removal COMPOSITION: "A" H3PO4 "B" x ... H2O 35 ... HNO3 ... 10 part "A" to Mix: parts "B". 1 3 DISCUSSION: native oxide films on Al:Au A12O3 This solution used to remove native oxide alloys. from before preferential etching to observe precipitates in specimens alloys. See ALAU- the 0001 under Aluminum Alloys. REF: Von Heimendahl, M—Acta Metall, 15,1441(1967) ALO-0016 ETCH Laser TIME: NAME: Photochemical, TEMP: TYPE: forming COMPOSITION: x ... Excimer laser DISCUSSION: thin films deposited on silicon, (100) wafers as a (1120) oriented thin film. A12O3, was Solution and an Excimer laser was used to photochemically deposit CC14:(A12CH3O6) oxide as single crystal sapphire from the liquid solution. aluminum REF: Ehrlich, D J & Tsao, JY — JVac Sci Technol, A(3),904(1985) ALO-0018 ETCH TIME: NAME: Oxide, TEMP: TYPE: passivation COMPOSITION: x ... A12O3 DISCUSSION: thin film A12O3 on InGaAsP/InP (100) LED devices as an anti-reflective (AR) deposition coating as an improvement over Si3N4. Thickness was 1805 A onto TO-18 type package headers with previously bonded. LEDs REF: Chin, A K et al — / Vac Sci Technol, B(l),72(1983) © 1991 by CRC Press LLC

142 129 ALO-0019 NAME: TIME: ETCH preferential Electrolytic, TEMP: TYPE: 0°C COMPOSITION: ANODE: ... H3PO4 x CATHODE: POWER: V EOH ... x 20 DISCUSSION: A12O3, on (100) oriented single crystal aluminum blanks used in a thin films anodized the alumina layer structure. Solution produced ridging on study hillocks on (111) of (110), (100). The blanks must have been beta-Al2O3.) and {Note: J J & Shaw, O G — Grooskreutz, Appl Phys, 35,2194(1964) REF: C ALO-0023 NAME: ETCH TIME: cleaning TEMP: Acid, TYPE: COMPOSITION: x ... H3PO4 x H2O ... DISCUSSION: thin films reactively sputtered on (111) silicon wafers with a poly-Si epitaxy A12O3 DC cm sputter used: "A" — developed 10 ft Two resistivity; "B" — 40 ft layer. conditions (down vs. up sputtering). After Al metallization wafers were photolithographic cm processed as structures. Prior to metallization, wafers were heat treated with different schedules MOS shown. He (bubble He through in to remove O2 contamination). No etch atmosphere LN2 (Note: shown is a general Etch for removal and cleaning.) solution REF: Chen, M-C — / Electrochem Soc, 118,591(1971) ALO-0024 ETCH TIME: NAME: Molten, flux, TEMP: 1200 K TYPE: removal COMPOSITION: ... x NaSO4 x ... Na2O2 DISCUSSION: material used Alpha-A12O3 a reaction study with development of a phase powdered in for Na-Al-S-O with material in flux shown. At 1 atm, NajO diagram a base; SO3 is the is acid solubility studies included: Cr2O3 beta-Al2O3, and NiO. component. Other Jose, / D et al — REF: Electrochem Soc, 132,735(1985) P — ALO-0025: & Elliot, J F W W J Electrochem Soc, 125,572(1978) Liang, A12O3 material. Similar work as in ALO-0024. ALO-0026 ETCH TIME: NAME: Vacuum, TEMP: TYPE: cleaning COMPOSITION: x ... vacuum DISCUSSION: as single crystal blanks used in a A12O3 of ceramic microstructure and metal study adhesion surfaces by smear/rubbing. (0001), to and (1010)_surfaces studied. Friction (1120) coefficient and adhesion was anisotropic vs. load on (0001) and (1120). Blanks were degassed and in due to inherent surface oxygen present. The (0001) is a glide plane; (1120) vacuum can other planes are slip planes, and prism show plastic deformation. Smeared on metals © 1991 by CRC Press LLC

143 130 CRC of Metal Etchants Handbook included evaluated Rh, Co, and Be. Surface attachment to some degree was due Cu, Ni, of and bonding. Also studied ferrites (FER-0002) presence SiC (SIC-0021). to oxygen D — Buckley, J Vac Sci Technol, A3(3),762(1985) H REF: OF ALUMINUM PROPERTIES PHYSICAL AIPO4 PHOSPHATE, Classification Phosphate Atomic numbers 8 & 13, 15, Atomic weight 121.29 Melting point (°C) 1540 Boiling point (°C) Density (g/cm3) 2.57 Refractive = ) index (n 1.54—1.57 — Hardness scratch) (Mohs 4—5 Crystal — rhomb rhombohedral) (hexagonal structure (1011) Color (solid) Greyish (rhombohedral) Cleavage (1101) ALUMINUM A1PO4 PHOSPHATE, Does not occur as a pure natural compound, but there are some 40 minerals, General: calcium. as of aluminum, potassium, or phosphates The mineral eggonite, mostly hydrous is representative of the most pure variety, and A1PO4.2H2O are half a dozen minerals there of same hydrated formula. All are the minor occurrence; whereas bauxite, A1(OH)3, is of the chief ore of aluminum as a complex admixture with clays occurring in large tropical area laterite deposits. a phosphate is little use in the metal industry, though the sulfates and oxides As there of Aluminum and its alloys is one metal the major industrial metals, equal have applications. importance to copper and iron. The phosphide, in is used as a phosphor-aluminum A1P, additive alloys, and has been grown as a single crystal. All natural phosphates are important in fertilizers. Technical No use in Solid State Application: at present, though it has been processing grown as a single crystal, as has A1P, both for general material studies. Etching: Soluble acids and alkalies. in PHOSPHATE ALUMINUM ETCHANTS ALPH-0001 ETCH NAME: TIME: TYPE: TEMP: COMPOSITION: ... HC1, cone. x DISCUSSION: A1PO4, crystals grown by a hydrothermal single gradient process from H3PO4 temperature in sealed glass ampoules, and used in a material study. No etch shown. (Note: Solution shown a general etch for phosphates.) is REF: Requardt, A & Lehmann, G — J Phys Chem Solids, 46,107(1985) © 1991 by CRC Press LLC

144 131 ALUMINUM ETCHANTS PHOSPHIDE ALP-0001 ETCH TIME: NAME: Water polish TYPE: TEMP: Acid, COMPOSITION: H2O x ... DISCUSSION: polish used to remove A1P, etch Solution the material. crystal wafers. single and REF: et al — Acta Me tall, 14,119(1966) Reynolds, A J OF AMALGAM, HgAg PROPERTIES PHYSICAL Classification Metal 47 & 80 Atomic numbers .,, Atomic (variable) weight 388.5 (°C) * (Ag) Melting point 960.5 357 (°C) point Boiling (Hg) Density (g/cm3) 13.75—14.1 — scratch) 3—3.5 Hardness (Mohs (isometric structure normal) (110) dodecahedron Crystal — Silver-white (solid) Color (dodecahedral — partial) (110) Cleavage AMALGAM, HgAg Occurs as a native metal compound, General: found in both mercury and silver and deposits, as small grains or fine crystals. Rare. Quantity of constituents varies widely usually AgHg, Ag5Hg3, There are several named minerals by percentage of silver from Ag,6Hg. Ag2Hg locale: AgHg (26.4% Ag) or amalgam, (35% Ag); arquerite, AgI2Hg and ordinary Ag); kongsbergite, Ag32Hg or Ag16Hg with over 90% silver. Heating on charcoal (86.6% volatilize will mercury, leaving a bead of silver. In mineralogy the term "amalgam" is the AuAg for compounds, reserved native gold occurs as an admixture of AgHg — though electrum — also called white or argentiferous gold. Native amalgam has minor use in industry due to scarcity as a distinct compound as it is a fraction of the ore bodies mined for their mercury or silver content. Artificial minor (1) are mercury combines with most metals: as combining with easy with amalgams formed zinc, gold, sodium and (2) using sodium amalgam with metal salts of iron, nickel, tin, manganese heavy platinum, forms the so-called cobalt, metal amalgams. or are temperature number of mercury containing alloys used as low There solders, but a it amalgams . . called amalgam even though as is electrum ... the best known application . is in dentistry, where gold and silver are compounded in small quantities in a mortar and pestle as fillings ... no mercury ... yet still called an amalgam. tooth Application: use or artificial amalgams have little Technical in the Solid State Natural of industry though there are a number se, binary and trinary compound semiconductors per as selenides, tellurides and antimonides. Mercury itself is a dopant species and can be has pyrolitically an HgCl source. Pure mercury from been rubbed on metal surfaces diffused to form a temporary amalgams for mounting or as an electrical contact, and there are high intensity light bulbs. mercury Etching: HNO3 and aqua regia (AuAg). © 1991 by CRC Press LLC

145 132 CRC of Metal Etchants Handbook ETCHANTS AMALGAM HGAG-0001 Nitric NAME: acid ETCH TIME: TEMP: removal RT TYPE: Acid, COMPOSITION: cone. ... x HNO3, DISCUSSION: single crystal. Concentrated acid used HgAg, dissolve the mineral for quan natural to analysis. diluted acid solutions used to Water surfaces. Where pure mercury titative clean applied as a film contact for electrical testing, concentrated acid was used to removal was and clean after tests. Mercury films applied to natural metal oxides — hematite, contacts acid and oxides) — removed with dilute (iron to observe structural effects magnetite siderite developed by the amalgam reaction. as Walker, mineralogy — REF: studies, 1951—1953 P >. HGZN-0001 NAME: TIME: ETCH Acid, cut TEMP: TYPE: COMPOSITION: 1 HNO3 ... ... 1 H2O2 1 ... alcohol DISCUSSION: ZnHg specimens acid saw cut with this solution, and used in a study of embrittlement with cracking After cutting, wash in water. Dry in alcohol, then compound. ether. of this Westwood, ARC — Phil Mag, 9,199(1964) REF: PROPERTIES ANTIMONY, Sb OF PHYSICAL Semi-metal Classification 51 Atomic number 121.75 weight Atomic 630.5 point (°C) Melting 1380 Boiling point (°C) 6.618 (6.691) Density (g/cm3) 0.045 Thermal conductance (cal/sec)(cm2)(°C/cm) 0.0494 heat (cal/g) 25°C Specific 38.3 heat Latent (cal/g) fusion of Coefficient linear expansion: thermal of 8-n 20°C °C) (micro-inch 8.5 (xl0-6cm/cm/°C)20°C 39.1 Electrical resistivity (micro-ohms-cm) 1st ionization energy (K-cal/g-mole) 199 8.64 potential ionization 1st (eV) 1.9 (Pauling's) Electronegativity 1.40 (angstroms) radius Covalent Ionic radius (angstroms) (Sb+5) 0.62 5.7 (barns) Cross section 18°C Magnetic susceptibility (cgs x 10"6) 99 1223 Vapor pressure (°C) © 1991 by CRC Press LLC

146 133 Hardness — scratch) 3—3.5 (Mohs structure (hexagonal rhombohedral) (lOTl) rhomb Crystal — Tin Color white (solid) perfect) Cleavage (0001) — (basal ANTIMONY, Sb a native element General: veins associated with silver and arsenic ores Occurs as in mineral stibnite, Sb2S3, which occurs as a primary mineral in quartz and although the granitic is major ore of antimony. The native antimony has a specific gravity (density) of rock the 6.6) 6.7, higher than the purified material (G = = due to trace presence of silver and G is It is sectile, brittle, and is slightly malleable when heated. It has a metallic iron. with luster a color and has a perfect (0001) cleavage, which is not common to pure metallic tin-white elements. Surfaces readily, particularly in the presence of sulfur. type tarnish industry, not is a pure metal in heavy used although there are several applications It as an additive to irons, steels, aluminum, brass, and bronze. The pure as is used in metal special melting point glasses, and as a black coloring pigment in both glass and clay low pottery. It one of the elements known to is man, and both antimony and arsenic compounds ancient have been used in black facial make-up, particularly as eye shadow, but are no longer in use today to their toxicity though there are several medical applications. due Application: Although it is not as widely used as phosphorus, it is Technical antimony dopant silicon. n-type in an is used to grow several compound semiconductors such It gallium antimonide, also as indium antimonide, InSb; and aluminum antimonide, AlSb. GaSb; is used as a constituent Antimony several medium temperature solders and some high in temperature alloys. Both used in Solid State package assemblies. brazing has for grown as a single crystal Antimony morphology and defect studies. been mixed Etching: hot concentrated H2SO4, and regia; acids of HF:HNO3. Aqua ANTIMONY ETCHANTS SB-OOOla ETCH NAME: etch TIME: 5—10 min Dash Acid, polish RT TYPE: TEMP: 1 RATE: COMPOSITION: mil/min 1 ... HF ... HNO3 3 12 ...CH3COOH(HAc) DISCUSSION: liquid specimens cleaved after freezing Sb, (0001) nitrogen, LN2, or cleaved under in LN2. Specimens were used in a polish etch development and dislocation etch study of antimony. Solution produces a good polish with no gas evolution. shown J REF: H et al — J Appl Phys, 29,1013(1958) Wernick, SB-OOOlb ETCH NAME: Dash etch, modified TIME: 5—10 min TYPE: polish TEMP: RT Acid, COMPOSITION: 1 ... HF 3 ... HNO3 12 ... HAc 1 ... Br2 © 1991 by CRC Press LLC

147 134 CRC of Metal Etchants Handbook DISCUSSION: Sb,(OOOl) in LN2. Solution shown produces a fair polish with no gas specimen cleaved SB-OOOla additional discussion. See for evolution. REF: Ibid. SB-OOOlc Dash, etch, modified TIME: 5—10 min ETCH NAME: polish TYPE: RT Acid, TEMP: COMPOSITION: ...HF 1 ... HNO3 3 6...HAC DISCUSSION: (0001) specimen cleaved in LN2. Sb, shown produces a fair polish with no gas Solution evolution. SB-OOOla for further discussion. {Note: This solution is a modification of See original etc.) the Dash, REF: Ibid. SB-OOOld NAME: Dash etch, modified TIME: 5—10 ETCH min TYPE: polish TEMP: RT Acid, COMPOSITION: ... HF 1 5 ... HNO3 12 ... HAc DISCUSSION: Sb, specimen cleaved in LN2. Produces a fair polish with no gas evolution. (0001) See SB-OOOla further discussion. for Ibid. REF: SB-OOOle ETCH NAME: Dash etch, modified min 1 TIME: TYPE: Acid, polish TEMP:RT COMPOSITION: 1 ... HF 5 ... HNO3 6 HAc ... DISCUSSION: Sb, (0001) specimens cleaved LN2. in very Produces a evolution. good polish with no gas SB-OOOla See discussion. further for Ibid. REF: SB-OOOlf ETCH NAME: Dash etch, modified TIME: TYPE: Acid, TEMP: RT removal COMPOSITION: 3 ... HF 5 ... HNO3 12 ... HAc 1 ... Br2 DISCUSSION: a specimen cleaved in LN2. Produces Sb, (0001) rough and uneven surface and etches © 1991 by CRC Press LLC

148 135 very with gas evolution. See SB-OOOla for further discussion. (Note: Compare results rapidly SB-OOOlb.) with REF: Ibid. SB-0004 NAME: TIME: ETCH TEMP: TYPE: removal/clean Acid, COMPOSITION: 2... HF 3 ... HNO3 H2O 5 ... DISCUSSION: a Cut wafers under glycol thallate with wafers. high speed cutting wheel to (0001) Sb, chipping. Mechanically lap with 600 grit, then 000 and 0000 aluminum prevent abrasive paper. solution shown as a light etch to remove damage and debris. Specimens used Use a study self-diffusion. in of Rosolowski, J H et al — J Appl Phys, 31,3027(1964) REF: SB-0005 ETCH Sulfuric acid TIME: NAME: Acid, polish TYPE: Hot TEMP: COMPOSITION: x ... H2SO4 DISCUSSION: Sb, single crystal wafers of different orientations used in a study of etch pits. Solution can be used polish surfaces prior to preferential etching. to Phys Hiramatsu, Shigeta, J — J & Soc Jpn, 13,1404(1958) REF: H SB-OOOlg NAME: CP4, modified TIME: 1—2 sec ETCH Acid, TYPE: TEMP: RT polish COMPOSITION: 3 HF ... ... HNO3 5 3 HAc ... 1 ... Br2 DISCUSSION: Sb, (0001) wafers cleaved under LN2. Solution produces a very good polish with some solution pitting evolution. See SB-OOOla for added discussion. (Note: Original CP4 gas and contained Br2 and was 0.6 for germanium.) developed REF: Ibid. SB-0002: Allred, W P et al — J Electrochem Soc, 107,117(1960) grown Sb, purity slugs etch cleaned in CP4 solution before using to high single crystal aluminum antimonide, AlSb. After etching rinse in DI water. © 1991 by CRC Press LLC

149 136 CRC of Metal Etchants Handbook SB-OOOlh ETCH modified TIME: 1—2 sec NAME: CP4, polish TYPE: TEMP: Acid, RT COMPOSITION: 2...HF ... 5 HNO3 4 ... HAc Br2 1 ... DISCUSSION: cleaved under LN2. Solution produces Sb,(OOOl) uneven polish with both pits wafers an gas See SB-OOOla for added discussion. evolution. and Ibid. REF: SB-0003 ETCH NAME: TIME: Cleave, defect TEMP: - 195°C TYPE: COMPOSITION: x cleave ... DISCUSSION: cleaved. under LN2, and used as cleaved Surface will show direction Sb, (0001) wafers trigonal axes and may show 60° twinning. Specimens used in a galvanometric properties of at study helium temperatures. liquid Steele, C — Phys Rev, 99,1751(1955) REF: M PROPERTIES OF ARGON, PHYSICAL Ar Classification Inert gas Atomic number 18 Atomic weight 39.948 Melting point (°C) -189.2 Boiling point -185.7 (°C) (g/cm3) -233°C Density 1.65 1.784 xlO-3 (g/cm3)0°C heat (cal/g/°C) 20°C 0.125 Specific of fusion Latent 6.7 heat (cal/g) conductivity (x 10"4 cal/cm2/cm/°C/sec) 20°C 0.389 Thermal ionization potential 1st 15.577 (eV) Cross (barns) 0.63 section pressure 200.5 Vapor (°C) Chemical reactivity None (Mohs — scratch) Hardness 2—2.5 Crystal structure (isometric — normal) (100) cube, fee Color (gas) Colorless (liquid) Clear Clear/bluish (solid) (cubic — solid) (001) Cleavage ARGON, Ar A natural element General: air which contains about 0.94%. It is separated by frac- in tionation of liquid air and is about 2V2 times more soluble in water than nitrogen though it as does combine with any other element not a compound; whereas nitrogen forms nitrides, © 1991 by CRC Press LLC

150 137 nitrates, nitrites. It is an inert, colorless gas at standard temperature and pressure (22.2°C and 760 mmHg) is best recognized by its characteristic spectra lines in the red end of and and is Symbol shown as A only, though Ar be standard (Gr: argon = inactive). spectrum. the may it is used for its inert properties in electric light bulbs and fluorescent tubes. In industry as used inert atmosphere for storage and chemical processing of metals and com Also an and react oxygen or water vapor in air, that as an inert furnace atmosphere in pounds to processing. metal Application: used is not directly Technical in fabrication of Solid State device Argon components, but is used as an inert atmosphere in vacuum or furnace systems, structural it various RF and epitaxy. It also is used as as gas mixture: Ar/H2 for a reducing such sputter in these systems; Ar/N2 for the sputtering atmosphere metal nitrides, such as Si3N4 or of A1N; for evaporation or sputter of metal oxides, such as SiO2 or BeO, and as Ar/N2/ Ar/O2 Ar+, for and, as an RF ionized gas, oxynitrides for surface cleaning prior to metallization O2 of a specimen. It is widely used in this latter process, but can induce subsurface damage depending upon power levels. RF processing of of the compound semiconductors, such as aluminum Chemical some air, aluminum AlAs and and respectively, which oxidize in antimonide, are arsenide AlSb, under argon or nitrogen atmospheres. handled has been grown as a single crystal in a vacuum system under Argon conditions cryogenic and for morphological study. It is fabricated as the argon laser. pressure As crystal, vary vacuum vapor pressure. Etching: single ETCHANTS ARGON AR-0001 ETCH Pressure TIME: NAME: Pressure, dislocation TEMP: 2 TYPE: (LhJ K COMPOSITION: x ... pressure, vapor DISCUSSION: Ar, single crystal ingots grown in vacuum under cryogen conditions and pressure. Develop structure defects by varying vacuum pressure. {Note: The reference describes and and for growing single crystal rare gases.) methods techniques Schwentner, N — Rare Gas Solids, Vol 3, Academic REF: New York, 1960 Press, PHYSICAL OF ARSENIC, As PROPERTIES Semi-metal Classification number 33 Atomic Atomic weight 74.92 Melting point (°C) 817 (28 atm) Boiling point 613 (sublimes) (°C) (g/cm3) Density 5.72 heat (cal/g) 20°C Specific 0.082 Heat of fusion (k-cal/g-atom) 88.5 Heat of sublimation (cal/g) 102 Atomic (W/D) 13.1 volume 1st ionization energy (K-cal/g-mole) 231 1st ionization potential (eV) 9.8 Electronegativity (Pauling's) 2.0 Covalent radius (angstroms) 1.20 © 1991 by CRC Press LLC

151 138 CRC of Metal Etchants Handbook radius (angstroms) (As+5) Ionic 0.46 of Linear 10"6) 20°C 4.7 expansion coefficient (x ohms-cm) resistivity (35) Electrical 20°C (micro 33.3 10~6) 5.5 x Magnetic susceptibility 20°C (cgs 4.5 section Cross (barns) 518 Vapor pressure (°C) scratch) Hardness (Mohs — 3.5 — rhomb (lOTl) (hexagonal (near-cube) Crystal rhombohedral) structure white Tin Color (solid) — Cleavage (0001) (basal perfect) As ARSENIC, quantity. in the pure element, but not in as Usually found in General: nature Occurs metallic veins of silver, cobalt, and nickel association and with cinnabar, realgar, with ores orpiment. latter two minerals are sulfides, As2O3, The for their brilliant red or and noted color, respectively. It is believed that amorphous arsenic (black) was first yellow recognized by Magnus in 1250 A.D. It is silver-white like tin when first cleaved, but oxidizes Albertus dull grey when sublimed by heating, re-solidifies as both a crystalline and amorphous to and, several pure is not considered dangerous, but metal compounds are extremely structure. The hazardous. industry the metallic element is used as an additive for many alloys of iron and steel, In as hardening and agent in bronze. Many compounds are used as insecticides, such as Paris a and in Adamsite and Lewisite were used as gases Green World War I. Black amorphous both times, was as a cosmetic eye shadow in ancient arsenic but is no longer used due to used its health hazard. When the metal is ignited in air it burns to the trioxide, which is noted for an garlic odor, and is extremely toxic. It also is used in glass fabrication as a intense agent, and low melting point glasses. coloring for in Arsenic several important applications Application: Solid State device Technical has both as an n-type dopant in silicon and in the growth of several compound fabrication, semiconductors. The important of the compound semiconductors is gallium arsenide, GaAs; common most GAS-. hygroscopic arsenide, AlAs, is not widely used, due to its acronym: Aluminum indium problems. InAs has similar nature; arsenide, thin growth arsenic compounds, In as epitaxy GaAs of films or, when used as a such diffusion dopant, the element is obtained using arseine, AsH3, to include growth by OMCVD and MBE. has been used as a low melting point glass in fabrication of silicon radiation It as junctions. paint-on coating over exposed planar detectors a defect has grown as a single crystal Arsenic general morphological and been studies. for Etching: HNO3, halogens, alkalies and mixed acids. ARSENIC ETCHANTS AS-OOOla ETCH NAME: hydroxide TIME: Sodium Alkali, removal TYPE: Hot TEMP: COMPOSITION: x ... 5—20%NaOH DISCUSSION: As,(0001) wafers cleaved from a bulk mass. Solution used as a general removal etch. effect. Specimens in a study of the DeHass-van Alphan used REF: Berlincourt, T G — Phys Rev, 99,1716(1955) © 1991 by CRC Press LLC

152 139 AS-OOOlb NAME: Nitric TIME: ETCH acid removal/polish TEMP: TYPE: Acid, RT COMPOSITION: HNO3, ... cone. x DISCUSSION: specimens. Solution used As, a general removal and polishing etch. (0001) cleaved as REF: Ibid. H Adachi, Hartnagel, HL — JVac Sci Technol, 19,427(1961) AS-0003: & wafers a in single crystal GaAs, p-type as fabricated as light emitting As, constituent with Al or Au dot contacts. Arsenic is removed diodes HNO3; whereas gallium is with removed alkalies producing a surface enriched with Ga or As, respectively. Light with by was improved with basic (alkali) solutions or or annealing at 350°C in N2 emission good 5 min. Strong acid treatment reduced or for emission. eliminated AS-0002a NAME: 10 sec ETCH TIME: Halogen, dislocation TEMP: RT TYPE: COMPOSITION: x ... 10% I2 x ... MeOH DISCUSSION: As, (111)(?) specimens cleaved in air at RT. Wafers were polished with 1HC1:2HNO3:12HAc. Solution was used to develop dislocations. Rinse in MeOH to shown (Note: residual final DI water wash. with a Arsenic is hexagonal-rhombohedral remove iodine perfect basal (0001) cleavage. It is occasionally observed as a near-cubic rhombohedron, with that cleavage (111) such shown is questionable. The probability is that the specimen the near-cubic appearance.) was in — Sheity, N & Tailor, REF: B M J Appl Phys, 39,3717(1968) J AS-0002b ETCH NAME: Bromine etch TIME: 45 sec TYPE: Acid, TEMP: RT dislocation COMPOSITION: 1 HF ... 2...HNO3 ... HC1 1 ... HAc(CH3COOH) 24 1 ... Br2 DISCUSSION: As, (111)(?) specimens cleaved in air at RT. Solution used as a dislocation etch. See note under for additional discussion. AS-0002a Ibid. REF: AS-0002c ETCH NAME: TIME: 1—2 min TYPE: Acid, polish TEMP: RT COMPOSITION: ... HC1 1 2 ... HNO3 12 ... HAc © 1991 by CRC Press LLC

153 140 Handbook of Metal Etchants CRC DISCUSSION: As, (111)(?) specimens cleaved in air at RT. Solution used as a polish etch prior to for dislocation See note under AS-0002a etching. additional discussion. REF: Ibid. © 1991 by CRC Press LLC

154 141 PHYSICAL OF BARIUM, Ba PROPERTIES Alkaline metal Classification 56 number Atomic 137.36 Atomic weight (725) Melting point (°C) 850 (1140) 1640 point Boiling (°C) Density (g/cm3) 3.5 25°C 0.068 (cal/g) heat Specific Heat of fusion (k-cal/g-atom) 1.83 vaporization (k-cal/g-atom) 35.7 Heat of (W/D) Atomic volume 39 energy 1st (K-cal/g-mole) ionization 120 (eV) potential ionization 1st 5.21 Electronegativity (Pauling's) 0.9 Covalent 1.98 radius (angstroms) radius (angstroms) 1.34 (Ba+2) Ionic Electrical resistivity (micro-ohms-cm) 50 function (eV) 2.48 Work Cross section 1.2 (barns) pressure (°C) Vapor 1301 — 8.5—9 (Mohs scratch) Hardness (isometric — normal) (100) cube, bcc Crystal structure Silver white (solid) Color Cleavage (cubic) (001) BARIUM, Ba Does not occur as a native element. Barite, General: (heavy spar), is the major BaSO4 ore when transparent, resembles calcite, CaCO3 (Iceland spar). Barite can form in a and, term "barite structure, equated to the rose" "rosette" used in material processing. white The pure metal has had little use in metal processing, but several compounds are of im portance: the sulfate a white pigment called "Wane fixe" used to weight paper; the is coloring is poison; and nitrates are green rat in pyrotechnics. Other barium salts carbonate a medical applications, such as Ba(OH)3 solutions used have evaluate the intestinal tract to as is opaque to X-ray. The hydroxide it is used in the refining of sugar. also Technical Application: The metal has not been used in Solid State processing, although barium fluoride, is used as a substrate, and is under evaluation as a thin film. In BaF2, primary processing materials, barium titanate, Ba2TiO3, is the of transducer ele electronic ment for ultrasonic generators. Etching: Soluble in water, single acids, and alcohols. BARIUM ETCHANTS BA-OOOla ETCH Ethyl alcohol TIME: NAME: TYPE: polish TEMP: RT Alcohol, COMPOSITION: x ... EOH DISCUSSION: and specimens. A general removal Ba, polish etch for barium. © 1991 by CRC Press LLC

155 142 CRC of Metal Etchants Handbook Hodgman, C et al — Handbook of Chemistry and Physics, 27th ed, Chemical REF: D Cleveland, Rubber 348 OH, Co., 1943, BA-OOOlb Hydrochloric TIME: NAME: acid ETCH TEMP: RT TYPE: Acid, polish COMPOSITION: HCl ... x DISCUSSION: This and other single acids can be Ba, as general etchants for barium. specimens. used Ibid. REF: OF FLUORIDE, BaF2 PHYSICAL BARIUM PROPERTIES Classification Fluoride 56 & Atomic numbers 9 weight 175.36 Atomic Melting point (°C) 1280 point (°C) Boiling 2137 Density 4.83 (g/cm3) radius (angstroms) Ionic 1.43 (ergs Surface 393 [on (111)] cm"2) 273°C free-energy (111)] [on -195°C 280 — scratch) Hardness (Mohs 2—3 — mm"2) 82 (Knoop kgf structure — normal) (100) cube Crystal (isometric (solid) Colorless Color (cubic Cleavage distinct) (111) — FLUORITE, BARIUM BaF2 Does not occur in nature as a compound, although there are several General: metallic fluorides, as fluorite, CaF2, and sellaite, such As an artificially compounded material MgF2. there is major industrial use in the manufacture of white enamels, and it is used in medicine as both antiseptic and as embalming fluid. an single Application: is one of the few fluoride crystals that show (111) Technical Barium like diamond and fluorite, as most others in the isometric system — normal class cleavage cubic, cleavage. show It has been used as a (111) cleaved substrate in the study of (001) float-off thin with the deposited films removed by films, technique with HCl for TEM metal study. As a deposited thin film, it has been converted to the oxide, BaO, as a more stable surface coating. single crystals are used for their optical properties as prisms, lenses, Bulk thin filter As a (100) or (110) deposited or film on semiconductor wafers, it has elements. been used as an optical coating in device structuring. Etching: in water, acids, and NH4C1. Soluble BARIUM FLUORIDE ETCHANTS BAF-0005b ETCH NAME: Sulfuric acid TIME: TYPE: Acid, removal TEMP: © 1991 by CRC Press LLC

156 143 COMPOSITION: ... H2SO4 x DISCUSSION: specimens. will etch barium fluoride very slowly and incompletely. This BaF2 acid REF: Ibid. BAF-0005c ETCH Oxygen TIME: NAME: conversion TEMP: TYPE: Ionized gas, GAS COMPOSITION: FLOW: x ... O+ ions PRESSURE: POWER: DISCUSSION: BaF2 specimens. Etching in an RF plasma of oxygen will convert the BaF2 single crystal in to BaO which is an even more inert and part, surface thin film than the surface, stable fluoride. REF: Ibid. BAF-0005a NAME: ETCH acid TIME: Hydrofluoric Acid, removal TYPE: TEMP: COMPOSITION: x cone. (2) x ... HF, NH4F ... (1) x% DISCUSSION: The material BaF2 soluble in both of the fluorine solutions shown. {Note: specimens. is solutions also apply.) BHF Encyclopedia of REF: Technology, Vol 10, John Wiley & Sons, New York, 1980 Chemical BAF-0006: C W — J Vac Sci Technol, B2,24(1984) Tu, on thin BaF2 was deposited by MBE films. indium phosphide (100) and (110) Material substrates. Films were deposited as single crystal. Also were co-deposited with SrF2 as BaxSr,.xF2 thin films. materials studied were SrF2 and CaF2. Other " BAF-0007 Water TIME: ETCH NAME: polish or RT Acid, warm TYPE: TEMP: COMPOSITION: ... H2O x DISCUSSION: (111) wafers used as substrates for metal deposition of BaF2, chromium, aluminum, and in a study of the mechanical properties of optical films. silver can be used to Water lightly clean and polish barium fluoride surfaces. REF: Pulker, H K — Thin Solid Films, 89,191(1982) BAF-0003 NAME: ETCH h TIME: 4 Acid, polish TYPE: RT TEMP: COMPOSITION: ... H2SO4 "A" 40 B" 30 .. .. HC1 "C" ... 80 OT Aerosol 60 70 .. ... H2O .. H2O 20 ... HAc (CH3COOH) DISCUSSION: air time related is time Polish RT. at required in cleaved were wafers (111) BaF2, to to and remove cleavage steps. The polishing process was as follows: reduce © 1991 by CRC Press LLC

157 144 CRC of Metal Etchants Handbook Glue wafer a polishing pad. 1. to up pad brass holder with paraffin — heat a slowly to prevent wafer cracking. Mount on 2. the polish pad with water and add 4 drops of solution "A" and 6 drops 3. Saturate of "B", an eye dropper. solution using at rpm — adding H2O:HC1 as needed. Lap 132 4. and 5. in solution *'C" (Aerosol OT supplier is Fischer Scientific.) Demount clean Bis, R F et al — / REF: Phys, 47,736(1976) Appl BAF-0004 NAME: Hydrochloric TIME: ETCH acid float-off Acid, TEMP: TYPE: COMPOSITION: x...HCl(30%) DISCUSSION: wafers cleaved in air BaF2, used as a substrate for Hot Wall Epitaxy (HWE) (111) and of PbSnTe. The substrate was held at 250°C growth epi growth. The lead tin telluride during film removed by hydrochloric etch undercutting using the float-off technique. Film was in were 70 to 2500 A and used thicknesses a morphological study of the compound. from REF: Suyman, H C et al — J Cryst Growth, 70,393(1984) BAF-0009 ETCH Hydrochloric acid, dilute TIME: NAME: Acid, float-off TYPE: TEMP: COMPOSITION: ... x HC1 x ... H2O DISCUSSION: wafers cleaved in air BaF2, used as a substrate for epitaxy growth of InGaSb. (111) and was vapor degreased in TCE, Substrate rinsed in liquid MeOH, and then acetone. After then epitaxy thin film was float-off removed with dilute HC1. the — Eltoukhy, H & Greene, J E REF: J Appl Phys, 50,505(1979) A BAF-0008 ETCH NAME: Nitrogen TIME: TYPE: Gas, TEMP: RT cleaning COMPOSITION: x...N2 DISCUSSION: (111) specimens cut and polished as circular lenses. Nitrogen blow off was BaF2, used to any particulate matter from surfaces remove evaporation of thin film chromium, before aluminum, or gold with no liquid treatment. REF: Walker, — personal application, 1976 P PHYSICAL OF BARIUM TITANATE, Ba2TiO3 PROPERTIES Classification Oxide Atomic numbers 56, 22 & 8 Atomic 372.57 weight Melting point (°C) Boiling point (°C) Density (g/cm3) © 1991 by CRC Press LLC

158 145 Ferroelectric (KeV/cm) 2—450 activity (Mohs — 6—7 Hardness scratch) (orthorhombic) Crystal (RT) (100) a-pinacoid 286 structure K 193 (1011) rhomb rhombohedral) K (hexagonal — 292 K (100) cube (isometric — normal) Grey-white (solid) Color Cleavage (cubic) (001) BARIUM TITANATE, Ba2TiO3 not occur as a natural compound. There are minerals as mixed General: Does titano- containing such as benitoite, BaTiSi2O9. The primary use of the artificially silicates barium, is ultrasonic the transducer element for titanate generators. Ultrasonics, in con grown as of with systems, are a major method degreaser cleaning for parts, materials, junction vapor equipment from a small beaker-sized ultrasonic and large, walk-in vapor degreasing unit—to modules. Application: The State industry is a major user of ultrasonic equipment Technical Solid processing vapor materials. Relatively large floor model chemical degreasers are used in of Smaller ultrasonic material and parts cleaning. for tabletop units are used with generators vapor or liquid cleaning, and for for bubble stirring etching solutions in processing active semiconductor circuit substrates, and allied materials. wafers, titanate been grown and used as a single crystal, and has Barium studied for general is also with attention to ferroelectric properties. It specific has been studied in its morphology two other pressure/temperature related crystal forms, and it has been fabricated as a hollow polycrystalline sphere evaluation of the pressure effects on the Curie temperature. for HC1, and H3PO4. Etching: hot ETCHANTS TITANATE BARIUM BAT-0001 Hydrochloric acid TIME: 4 min or 4 h ETCH NAME: preferential Acid, RT to 0°C TYPE: TEMP: COMPOSITION: ... HC1, cone. x DISCUSSION: (111) Solution (100) wafers. Ba2TiO3 used at the two times/temperatures shown to and magnetic structures. {Note: Photographs are excellent.) develop domain Camerson, DP — IBM Res Dev, REF. 1,2(1957) BAT-0008a: H & Drougard, M Schlosser, — J Appl Phys, 32,1227(1961) E Ba2TiO3 specimens used in a study of surface layer structure above the Curie Point. Solution used a dip etch for final surface cleaning. as Hooten, — A & Merz, W J BAT-0012: Phys Rev, 988,409,(1955) J with Ba2TiO3 Solution used at RT crystals. several minutes soak. Develops domain single related pole figures, and shows that the nose end of an ingot etches more rapidly than the end and tail Nose and tail more often called seed (Note: tail end.) end. BAT-0002 ETCH NAME: Phosphoric acid TIME: TYPE: Acid, polish TEMP: 155°C COMPOSITION. ... H3PO4 x DISCUSSION: Ba2TiO3 (100) wafers used in a study of ferroelectric domains activated from 2 to 450 © 1991 by CRC Press LLC

159 146 CRC of Metal Etchants Handbook After etching the solution shown, pole in water. Use 4 N NaCl solution for KeV/cm. in — pulse HF to solution to develop 180° domain walls: pulse 5 sec — wait add poling 0.1% move repulse, repeat as needed. Domain walls will and with each pulse sequence. sec 15 — H L & Zachmanidis, P J — J Appl Phys, REF: Stadler, 34,3255(1963) Stadler, L — JAppl Phys, 34,571(1961) BAT-0003: H wafers H3PO4 in a study of etch hillock formation. Etch slightly in (100) BajTiOg used acetone — pole specimens in water — wash in 150°C — wash in aqua regia, RT, at AC sec, and 5 etch in 1% HF, RT, 30 sec to develop grain boundaries. Then, to develop final hillocks: DC pole in water and (2) etch in 1% HF, RT, 30 sec. Hillocks, ad hoc, are (1) charged areas domain walls. Mounds and pyramids were observed on (100) negatively near in that in (110) directions. Changes aligned resistivity were proportional to surfaces, were strain. Pearson, — L & Feldman, W J Jr BAT-0004: Phys Chem Solids, 9,28(1958) G for BAT-0003. of developing grain boundaries shown in Reference method Myerhofer, 112,413(1958) — Phys Rev, BAT-0005: D specimens (100) prepared Ba2TiO3 very thin wafers and used in domain studies. as Solution was used at 120°C as a thinning and polishing etch. Rinse in DI water, then alcohol. BAT-0006: Miller, — Phys Rev, 111,736(1958) R C (100) wafers. used at 155°C as a thinning and polishing etch, then Ba2TiO3, Solution in with a Pt electrode. pole water DC R C & Savage, A — Phys Rev, BAT-0007: Miller, 112,755(1958) (100) Solution used at 155°C, 10—20 wafers. rinse in DI water, then Ba^iO^ min, alcohol before DC poling. in Ibid. BAT-0008b: specimens. Solution used at 140°C, 15 min to 1 h as a polishing and thinning Ba2Ti03 Follow HC1 final cleaning dip: BAT-0008a. etch. with Last, J T — Phys Rev, 105,1740(1957) BAT-0009: prevent specimens. Ba2Ti03 above 130°C (Curie Point of material) to Solution used selective domain etching. BAT-0010: Last, JT-^v Sci Instr, 28,720(1957) BajTiO-j specimens. Wafers were mounted on Teflon or silicone tape, mechanically lapped and etch thinned with solution at 130°C. Removal rate shown as 1 |xm/min. then BAT-0011 ETCH TIME: NAME: TYPE: Cut, forming TEMP: COMPOSITION: ... pressure x DISCUSSION: Ba2TiO3 hemispheres cemented together to form a sphere. The specimen polycrystalline pressure was studying the effects of in on the Curie temperature. used REF: Jaffe, H et al — Phys Rev, 105,57(1957) BAT-0013 ETCH TIME: NAME: Thermal, transition TYPE: TEMP: COMPOSITION: x ... heat DISCUSSION: Ba2TiO3 single crystals used in an electrostatic study of ferroelectric phases. Crystal at structure was rhombohedral at 193 K to orthorhombic change 268 K (RT), to cubic at 293 K. © 1991 by CRC Press LLC

160 147 REF: J & Ahtee, M — J Phys Chem Solids, 44,1(1983) Smolander, PROPERTIES OF TUNGSTATE, BaWO4 PHYSICAL BARIUM Classification Oxide 74 & 8 numbers Atomic 56, 385.28 Atomic weight Melting approx. (°C) 1200 point point Boiling (°C) Density (g/cm3) 5.04 — Hardness 4—5 (Mohs scratch) structure — pyramidal) (111) pyramid Crystal (tetragonal Clear whitish (solid) Color to p( (octahedral) Cleavage 111) BARIUM TUNGSTATE, BaW04 Does not occur as a natural General: although there are other minerals as compound, tungstates copper or lead alone or with molybdenum. Scheelite, CaWO4 is an important of ore, tungstate is wolframite, (Fe,Mn)WO4. There is no use of barium tungsten in industry, as They the minerals and primarily used as a source of tungsten. natural do have some are application as coloring agents in glass. Technical Application: Single crystal barium tungstate as a Solid State material has been evaluated for morphology and compound characteristics, but has found no use as general electronic device, date. an to H3PO4. Etching: BARIUM ETCHANTS TUNGSTATE BWO-0001 Phosphoric ETCH TIME: NAME: acid Acid, polish TEMP: TYPE: COMPOSITION: ... cone. x H3PO4, DISCUSSION: single crystal specimens used in a study of Raman frequency BaWO4 and tem shifts perature Material has the scheelite dependence. tetragonal system — pyramidal structure: class. Other tungstates studied were CaWO4 and SrWO4. REF: Degreniere, et al — J Phys Chem Solids, 45,1105(1984) S PROPERTIES OF BERYLLIUM, Be PHYSICAL Alkaline metal Classification number 4 Atomic Atomic weight 9.0122 Melting point (°C) 1283 (1278) Boiling point 2970 (°C) (g/cm3) 1.85 Density conductance (cal/sec)(cm2)(°C/cm) 0°C 0.440 Thermal Specific heat (cal/g) 0°C 0.41 (0.45 @ 20°C) Latent heat of fusion (cal/g) 260 © 1991 by CRC Press LLC

161 148 CRC of Metal Etchants Handbook 260—275 of Heat fusion (cal/g) 73.9 (k-cal/g-atom) of Heat vaporization 5.0 Atomic volume (W/D) 215 (K-cal/g-moles) 1st energy ionization 9.32 potential ionization (eV) 1st 1.5 (Pauling's) Electronegativity 0.90 (angstroms) radius Covalent (Be+2) 0.35 (angstroms) radius Ionic 11.5 thermal linear of Coefficient expansion (xlO-6cm/cm/°C)25°C 0.25 (micro-ohms"1) Electrical conductance 4 20°C cm) ohms 10~6 (X resistivity Electrical 3.92 (eV) Electron work function 0.009 Cross section (barns) 6—7 (Mohs Hardness — scratch) (1010) prism (hexagonal Crystal — normal) structure Silver-grey (solid) Color (10T0) poor) Cleavage (prismatic, BERYLLIUM, Be Does not occur as a General: element in nature. There are about 20 beryllium- free containing with none major occurrences, though several are quite widely dis minerals as sources The silicates are the main aluminum of ore: beryl, Be3Al2(SiO3)6 tributed. beryllium representative as both an ore and as the precious gem stone sapphire, deep blue; is aqua marine, blue; emerald, bright green, as well as a yellow variety called yellow beryl. pale one pure resembles The in appearance and chemical properties and is metal of magnesium the few metals that will scratch glass, H = 6.5—7. It is the lightest of known metals and is finding increasing use in industry, particularly as an with aluminum for lightweight construction, and other metals where it increases alloy endurance and resistance. Beryllium compounds have a sweet odor and fatigue corrosion particular considered to health, the oxide in are due to dusting during many hazardous cutting. Application: Beryllium metal is not widely used in Technical State processing Solid although has use as a dopant species in some compound semiconductors. It has been used it for the metal and as an aluminum alloy pure metal electrode deposition on quartz radio as frequency crystals to reduce mass loading effects on frequency, although special handling is required to the toxicity of beryllium and its compounds. due Soluble alkalies. acids and Etching: in dilute and Caution be observed Note: handling beryllium should its compounds due to toxicity in and health hazard. There are OSHA regulation requirements that must be met for those processing the material. ETCHANTS BERYLLIUM BE-0001 ETCH Potassium hydroxide TIME: 2—3 min NAME: TYPE: Alkali, cleaning/removal TEMP: Warm (30—40°C) COMPOSITION: x ... *30% KOH or NaOH *450 g/1. © 1991 by CRC Press LLC

162 149 DISCUSSION: as 0.060 wire. Solution was used to etch clean wire prior to material Be, diameter etching, electrodes quartz crystal blanks. After AT-cut heavy water wash, as on evaporation lamp dry. "U" shaped clips of Be wire were and on tungsten coils and evaporated IR hung a oil-pump vacuum system with a 6" small Pyrex bell jar. After metallization, in diameter/high system to at least 10"6 Torr and hold 20—30 min to remove pump vapors, before Be opening. Walker, P personal development, 1968 REF: — BE-0002 NAME: acid TIME: ETCH Hydrochloric removal TYPE: Acid, TEMP: COMPOSITION: x ... HC1 DISCUSSION: as an evaporated thin film used is a study of reactions Be, silicon and oxygen at with different Be was deposited on a (111) silicon substrate containing a layer of temperatures. then The substrate was degreased in TCE: silicon acetone, methanol, and water rinsed. SiO2. Then dipped in 10% HF and water rinsed immediately prior to CVD deposition of 4000 A of SiO2 by beryllium metal evaporation. Wafers were annealed at different tem followed forming in of reactions. Above 400°C Be reacts with SiO2 study an insoluble peratures a possibly BeO, in part. residue, Moore, J B & McCaldin, J REF: — J Electrochem Soc, 124,625(1977) C BE-0003 NAME: acid TIME: 60 sec ETCH Phosphoric Acid, preferential TYPE: 175°C TEMP: COMPOSITION: x ... H3PO4, cone. DISCUSSION: Be specimens. Solution used as a defect and structure development etch. REF: BE-0004a NAME: ETCH TIME: TYPE: Electrolytic, thinning TEMP: COMPOSITION: ANODE: ... HC1 1% CATHODE: 2% HNO3 POWER: ... 97% ethylene glycol (EG) ... DISCUSSION: Be, thin film deposits thinned with this solution for electron microscope study of dis locations. REF: J D et al Baird, Nature (London), 182,1660(1958) — BE-0004b ETCH NAME: Freeze etch TIME: 196°C TYPE: preferential TEMP: - Ice, COMPOSITION: x ... ice © 1991 by CRC Press LLC

163 150 CRC of Metal Etchants Handbook DISCUSSION: Be, deposited on ice under vacuum at - 196°C (LN2) temperature. Produces thin films structure the beryllium. "freeze-out" a of REF: Ibid. BE-0005 Heat TIME: ETCH NAME: forming Thermal, TYPE: TEMP: COMPOSITION: heat x ... DISCUSSION: diameter from Be, to 1.5 mm spheres formed by arc melting under polycrystalline 0.1 He atmosphere. Fifty percent of smaller an were single crystal. Use chips and flakes sizes in copper pot that was water cooled, striking the material with sporadic bursts of power a splatter spheres. to form Ray, A E & Smith, J F — Acta Metall, 11,310(1958) REF: BE-0006 ETCH TIME: NAME: Acid, TEMP: TYPE: removal COMPOSITION: x...6iVHCl x NH4OH (1 mg equivalent) ... DISCUSSION: Be, specimens used in a study of neutron-transfer reactions associated with nitrogen bombardment. REF: M L et al — Phys Rev, 106,251(1957) Halbert, BE-0007 ETCH NAME: TIME: polish TEMP: Electrolytic, TYPE: ANODE: Be COMPOSITION: 4ml...HCl CATHODE: ml ... HNO3 POWER: 15 V 20 4ml...H2SO4 200 ... ethylene glycol (EG) ml DISCUSSION: micro-strain. crystal specimens used in Be, study of single Solution shown used to a polish ingots before straining. REF: Lawley, A et al — Acta Metall, 14,1339(1966) BE-0008 ETCH TIME: NAME: Electrolytic, TEMP: TYPE: removal COMPOSITION: ANODE: Be ml ... H3PO4 100 CATHODE: 30ml...EOH POWER: 30ml...H2SO4 30 ml ... glycol DISCUSSION: Be, (001), (100), and (110) cut wafers used as substrates for growth of BeO. After diamond cutting, were lapped down with 3-fim wafers grit using a wheel. Solution shown © 1991 by CRC Press LLC

164 151 was to polish and remove residual damage prior to oxidation to convert surfaces to used (Note: Glycol probably ethylene glycol.) BeO. was V REF: Acta Crystallogr, 12,136(1959) D Scott, — Met, W HR — JInst Haines, 80,628(1951) B & BE-0009: Mott, used Be, a general etchant for beryllium. specimens. Solution as BeMx ALLOYS, BERYLLIUM metallic alloys do not occur in nature. General: are only nine minerals Beryllium There as minerals, though it appears as a trace element in several others. The listed beryllium occurs important beryl, an aluminum silicate, and it is as an oxide, sulfide, and most ore phosphate. the element is used as an alloy with copper, aluminum, iron, etc., Industrially improve to wear, resistance, and reduce alloy weight. corrosion Application: Beryllium shim stock is used in Solid State processing Technical copper into spring its vacuum evaporation it is cut qualities. small "fingers" to hold semi for In wafers and dielectric substrates in position on a flat plate during metallization conductor because its and, wear characteristics, does not lose it spring capabilities under such heat of Similar for or plate holder designs are used application. holding parts during electrical fingers material metal and in chemical processing where the testing, is not attacked by plating, solutions being used. An aluminum.beryllium mixture (38% Be) has been used as an evaporation alloy on quartz crystal frequency blanks to reduce metal mass loading effects for improved radio of stability. be observed in such operations due to the toxicity should frequency Caution compounds — there is a distinctive sweet odor. beryllium Single acids of HC1, H3PO4, and alkalies; HC1:HNO3 mixtures. Etching: ALLOYS BERYLLIUM ETCHANTS BERYLLIUM:COPPER BECU-0001 NAME: Hydrochloric acid, dilute TIME: 1—2 min ETCH Acid, TEMP: RT TYPE: cleaning COMPOSITION: 1 ... HC1 ... H2O 20 DISCUSSION: as Be:Cu, to 0.030 thick. Material cut strips finger clips to hold wafers in position 0.005 by spring action on evaporation holder plates during metallization of parts. Also used as spring contacts hold specimens in position in test fixtures. After cutting fingers to shape to etch rinse, in the solution shown. Water lightly methyl alcohol rinse, and air dry or clean build-up blow After use, with excess metal dry. on fingers from evaporation, peel nitrogen away metal with tweezers and etch clean as needed. REF: Fahr, — personal communication, 1978 F ~ BECU-0002 ~ NAME: Acetone TIME: 1—2 ETCH min TYPE: Ketone, cleaning TEMP: RT COMPOSITION: x acetone ... DISCUSSION: Be:Cu, strips 0.003 to 0.040 thick. Material cut and used as either finger clips to hold © 1991 by CRC Press LLC

165 152 CRC Metal Etchants Handbook of place wafers/substrates metallization or as holding clips on wafer test during in vacuum evaporation, wire metal is peeled away and/or In brushed, degreased assembly units. excess Test then acetone and nitrogen blown dry. in holder fingers degreased TCE, with rinsed as and "U" clips on tungsten coils similarly cleaned prior to use as an rinsed required. source. evaporation P Walker, application, 1968/1978 — personal REF: ETCHANTS ALUMINUM BERYLLIUM BEAL-0001 Potassium hydroxide ETCH 2—3 min NAME: TIME: Alkali, cleaning TEMP: 30—40°C TYPE: COMPOSITION: x... 30%KOH(NaOH) DISCUSSION: as Al:Be(38%), polycrystalline wire. Solution used to clean wire prior 0.060 diameter as blanks evaporation alloy on quartz crystal radio frequency use to reduce mass to an under After heavily in DI water and dry wash a heat lamp. "U" clips loading. etching, hung on tungsten coils for evaporation and, after evaporation, system was pumped to were to Torr at least 30 min to cool the system and eliminate beryllium vapors due for 10~6 toxicity. REF: P — personal development, 1969 Walker, PROPERTIES OF PHYSICAL BeO OXIDE, BERYLLIUM Classification Oxide Atomic numbers 4&8 weight Atomic 25.02 Melting (°C) point 2550 (°C) point Boiling (g/cm3) Density 2.017 (3.025) (n Refractive = index ) 1.733—1.719 of Limit application (°C) 2400 (J/kg °C) (mean) Specific heat 2180 Coefficient thermal of expansion linear 7.5 25—800°C cm/cm/°C) 10"6 (x °C) 1000 °C Thermal conductivity (W/m 29 108) (x resistivity Electrical 600°C 4 (X1O12)21OO°C 8 Hardness (Mohs — scratch) 9 hemimorphic) — (hexagonal structure Crystal order pyramid 3rd (2133) Color (solid) White (basal Cleavage or pedion) (0001) BERYLLIUM OXIDE, BeO General: Occurs as the mineral bromellite, BeO, and noted from only one location in Sweden. Industrially, oxide is classified as a high temperature refractory ceramic. It is the an as used alone or mixed with alumina as pressed insulator, for crucibles, furnace powder linings, and tubing. Technical Application: Beryllium oxide is a II—VI compound semiconductor, but in fabrication, Solid processing its major use has been as a ceramic substrate for circuit State It particularly high frequency microwave device application. for is fabricated as a pressed © 1991 by CRC Press LLC

166 153 powder (like alumina), and there is ongoing development to reduce grain size for blank frequency circuit to include use as a packaging material. It has been improved assemblies, thin studied single crystal, and deposited as a a film, directly, or converted and as grown nitride to an oxide by thermal oxidation in evaluation as a surface from similar to a coating dioxide. Beryllium and its compounds are toxic and a health hazard. CAUTION: silicon H3PO4, HF, and alkalies. H2SO4, Etching: BERYLLIUM OXIDE ETCHANTS BEO-OOOla NAME: Phosphoric acid TIME: 60 sec ETCH Acid, preferential TEMP: 175°C TYPE: COMPOSITION: x ... H3PO4 DISCUSSION: (0001) Wafers cut from a single crystal and lap/polished with BeO, diamond wafer. The material polarity like compound semiconductors. shows (000 l)A-bery Ilium paste. The is very slowly attacked in this solution. surface (OOOl)B-oxide surface is rapidly etched. The The develops etch pits and possibly dislocation pits on the (0001)A, but the authors solution dislocations. that work is needed to develop further A damaged point on the (0001)B says surface developed a four-sided, square prism etch pit. Crystals tend to grow as pyramids with a (0001) basal plane. preferred Austerman, S — J Appl Phys, 34,339(1963) REF: B BEO-OOOlb NAME: acid ETCH TIME: Sulfuric preferential TEMP: Acid, TYPE: COMPOSITION: x ... H2SO4, cone. DISCUSSION: (0001) wafers. Solution used as a preferential etch in a similar manner as shown BeO, BEO-OOOla for phosphoric acid. under Ibid. REF: BEO-0003 Sulfuric min dilute TIME: 5—10 ETCH NAME: acid, cleaning TEMP: RT TYPE: Acid, COMPOSITION: ... H2SO4 1 ... 1 H2O DISCUSSION: size powder blanks. After cutting BeO, pressed for use as substrates for device to mounting of power diodes, parts were soaked clean in this solution. Follow with heavy DI water washing, rinse, and dry under IR lamp. Also used for cleaning of package MeOH in assembly. parts device Walker, 1963—1964 — personal application, REF: P BEO-0007: V D — Ada Crystallogr, 12,136(1959) Scott, BeO, thin films grown on single crystal beryllium wafers cut (001); (100) and (110). solution Material in a growth and structure study of BeO. A 15% sulfuric acid used developed Material fine parallel to <001) directions. cracks cleaved along these line directions. © 1991 by CRC Press LLC

167 154 CRC of Metal Etchants Handbook BEO-0004 ETCH hydroxide TIME: NAME: Potassium removal TEMP: TYPE: Alkali, COMPOSITION: 10—30%KOH ... x DISCUSSION: pressed powder substrates. Solution BeO, a general etch for the (0001) wafers and is material. Grossmann, J Herman, D S — J Electrochem Soc, 116,674(1969) REF: & J Shehata, & Kelly, R — T Electrochem Soc, 122,1359(1975) BEO-0005a: M (0001) wafers. Solution BeO, as a general etch. used BEO-0006a NAME: Hydrochloric TIME: ETCH acid removal 120°C Acid, TYPE: TEMP: COMPOSITION: HC1, cone. x ... DISCUSSION: (0001) wafers and pressed powder substrates. Referred to as BeO, general etch for a the material. Ehman, 121,1240(1974) F — J Electrochem Soc, REF: M BEO-0006b NAME: TIME: ETCH TYPE: Acid, removal TEMP: Boiling COMPOSITION: x ... H3PO4 ... H2SO4 x DISCUSSION: general and pressed powder substrates. Solution referred to (0001) a wafers BeO, as for the material. etch REF: Ibid. BEO-0005b: Ibid. (0001) wafers. BeO, used as a general etch. Solution BEO-0002 NAME: 10 min or 30—60 ETCH TIME: Acid, dislocation min TYPE: TEMP: Boiling COMPOSITION: 1 ... HF 6 ... H2O DISCUSSION: BeO, (0001) single crystal wafers used in a study of dislocation development. Solution 1st develops defined hexagonal pits after 10 min. With extended etching sharply and very 2nd order prisms and pyramidal planes are developed. REF: Vandervoort, A R & Barmors, W L — / Appl Phys, 37,4483(1966) BEO-0008 NAME: TIME: ETCH TYPE: Mechanical, defect TEMP: COMPOSITION: x ... stress © 1991 by CRC Press LLC

168 155 DISCUSSION: slip single in a study of dislocation, used and fracture. An intron (0001) crystals BeO, was used to point damage surfaces at hardness temperature levels to induce tester various (Note: is a Knoop hardness tester unit This a specially designed diamond defects. using tip.) wedge Bentlo, G G & Miller, K T — J Appl Phys, 38,4248(1967) REF: OF BISMUTH, Bi PROPERTIES PHYSICAL Semi-metal Classification 83 number Atomic 208.98 weight Atomic 271.3 (°C) point Melting 1560 point Boiling (°C) 9.8 Density (g/cm3) 0.020 20°C Thermal conductance (cal/sec)(cm2)(°C/cm) 0.0294 20°C (cal/g) Specific heat 12.5 of (cal/g) fusion Latent heat 12.5 Heat of fusion (k-cal/g-atom) 204.3 (cal/g) of Heat vaporization 21.3 (W/D) Atomic volume 185 energy ionization 1st (K-cal/g-mole) 9.0 1st ionization potential (eV) 1.9 (Pauling's) Electronegativity 1.46 radius Covalent (angstroms) 0.96 (Bi+3) Ionic radius (angstroms) 13.3 thermal of expansion Coefficient linear (xlO-6cm/cm/°C) 106.8 ohms-cm) (micro Electrical resistivity 1271 (°C) pressure Vapor 100 (mmHg) 1200°C 4.6 x 104) Modulus (psi elasticity of 0.034 Cross (barns) section 0.33 ratio Poisson 104) Shear modulus x (psi 1.8 2.56 Hardness scratch) — (Mohs (1011) rhomb Crystal — rhombohedral) structure (hexagonal Grey/reddish-silver Color (solid) (0001) (basal — perfect) Cleavage Bi BISMUTH, Occurs as a native element as General: vein mineral commonly associated with lead, a silver, nickel, and cobalt ores. There are a number of bismuth-containing minerals, mostly as silver lead sulfides and arsenides. The most important ore mineral is bismuthinite, and diamagnetic, Bismuth poor conductor of electricity, is a and expands upon soli Bi2S3. is in crystalline form. Bismuth will burn in dification with a brilliant blue flame with air production heavy, yellow oxide fumes. Although of is hexagonal — rhombohedral it is it usually found in reticulated, arborescent masses and as grains. It has perfect (0001) cleavage, slightly is very brittle, but when heated is and malleable. For many years it was sectile, confused with lead and tin as all are silver-white in color, but bismuth has a reddish hue. but Rarely in industry as the pure metal, used is a constituent in many alloys — © 1991 by CRC Press LLC

169 156 CRC of Metal Etchants Handbook low melting such as those used in sprinkler heads for fire protection. It particularly solders temperature use casting form in low a fabrication of parts. special has as Not used in Solid State processing and fabrication of silicon, Technical Application: gallium arsenide devices though it is an n-type dopant in some compound germanium, and semiconductors. semiconductors in growing II—V compound used such as bismuth selenide, is Bismuth and bismuth telluride, Bi2Te3. It has been grown as a single crystal Bi2Se3 structural for data general morphological studies. and HNO3, aqua hot H2SO4; slowly in HC1, HF, and halogens. Etching: regia; ETCHANTS BISMUTH BI-0001 Nitric acid TIME: NAME: ETCH cleaning Acid, TYPE: TEMP: COMPOSITION: x ... HNO3, cone. DISCUSSION: single crystal specimens from ingots Bi, by the Bridgman technique. Bars cut grown with jeweler's saw. (0001) bar ends were mechanically polished. The solution was used a and a etch to reduce bar dimensions "sizing" to etch clean the bars. as REF: Gallo, C F — / Appl Phys, 34,144(1963) BI-0005: Mullins, W — Ada Me tall, 4,421(1956) W single crystal used in a study of induced grain boundary motion by Bi, specimens general magnetic Solution used as a flux. removal etch. application of BI-0002 NAME: Hydrofluoric acid, dilute TIME: ETCH min 15—20 TYPE: damage removal TEMP: RT Acid, COMPOSITION: 2... HF 98 ... H2O DISCUSSION: (0001) wafers used in Bi, study of slip and failure from applied tension and its a orientation dependence. After mechanical lap and polish, solution used to remove residual damage. Up 0.2 mm damage removed. to Phys Garber, et al — Sov I (Solid State), 3,832(1960) REF: R BI-0003 NAME: Tri-iodide, ETCH TIME: modified TYPE: polish TEMP: RT to hot Halogen, COMPOSITION: x ... KI, sat. sol. x...I2 . x H2O ... DISCUSSION: LN2, wafers cleaved under Bi, nitrogen, (0001) to minimize strain. Etchant used liquid as a KI saturated solution to polish wafers. S REF: B & Meiboom, Abeles, — Phys Rev, 101,544(1956) © 1991 by CRC Press LLC

170 157 BI-0004a NAME: TIME: sec, 10 cycles ETCH 60 polish TYPE: TEMP: Electrolytic, COMPOSITION: ANODE: Bi 35 ...KI CATHODE: g I2 POWER: 1 A/cm2 1 g ... HC1 RATE: 0.015760 sec ... ml 10 200ml...H2O DISCUSSION: wafers cut Bi, sandblasted as 5/8 diameter discs used in a study of anomalous (0001) and effects. used to etch polish to within Solution (xm of surface plane planar orientation skin 1 strain-free surface. After for rinse in 1HC1.1EOH to remove surface film left on etching, material electrolytic etching. {Note: This is an acidified tri-iodide solution; film re from is residual See: Gold.) maining iodine. G Smith, — Phys Rev, 115,1561(1959) REF: F BI-0015a NAME: TIME: ETCH Acid, TEMP: TYPE: polish COMPOSITION: ... HAc 3 ... 1 H2O2 DISCUSSION: crystal specimens. Solution used as Bi, single general cleaning and polishing etch for a bismuth. REF: Rutherford, R J — Proc Am Soc Test Mater, 24,739(1924) BI-0006a ETCH TIME: 1—5 min NAME: Acid, polish RT TYPE: TEMP: COMPOSITION: 6...HNO3 6... HAc 1 ... H2O DISCUSSION: (0001) wafers used in a study of dislocations. Solution used to polish surfaces prior Bi, to preferential etching. Lovell, 30,234(1959) C & Wernick, J H — J Appl Phys, REF: L J BI-0013: M & Stofke, E W — J Appl Phys, 38,5210(1967) Yim, Bi.BiMn (4%), single crystals. The BiMn segments were as ordered filaments in the hexagonal bismuth Ingot was a eutectic crystal. Solution used to polish surfaces in matrix. study of crystal morphology. a BI-0006b ETCH TIME: 15 sec NAME: TYPE: dislocation TEMP: RT Halogen, COMPOSITION: x ... 1%I2 x MeOH ... DISCUSSION: Bi, (0001) wafers used in a dislocation study. After polishing in solution shown under dislocations. BI-0006a, solution was used to develop this {Note: This mixture is used on © 1991 by CRC Press LLC

171 158 CRC of Metal Etchants Handbook germanium, compound and other metals as a polishing, preferential, silicon, semiconductors, surface conditioning Reactions are similar to the bromine-methanol selective or solution. (BRM) mixtures.) REF: Ibid. BI-0015b ~~~~ NAME: acid TIME: ETCH Hydrochloric cleaning TEMP: TYPE: Acid, COMPOSITION: (1) HC1 (2) 1 ... HC1 x ... EOH ... 1 DISCUSSION: crystal specimens. Both solutions Bi, as general cleaning etches after etching single used in iodine solutions to remove residual iodine films from specimens and as a general surfaces etch. Residual surface iodine can be removed by washing in methanol.) {Note: Ibid. REF: RI-0004b: Ibid. skin used a study (0001) wafers anomalous in effects. The 1HC1:1EOH solution Bi, of used to clean residual iodine from surfaces after electrolytic etch was in a tri- polishing iodide solution. type BI-0007 ETCH Nitric acid, dilute TIME: NAME: Acid, preferential TYPE: TEMP: COMPOSITION: x ... HNO3 x ... H2O DISCUSSION: Bi, specimens used in a study of galvanomagnetic properties in longitudinal magnetic fields. Pits by this solution were used to orient the specimens. developed Babiskin, — Phys Rev, 107,981(1957) REF: J Connell, R A & Marcus, J A — Phys Rev, 107,940(1957) BI-0008: single in specimens used Bi, studying the low temperature galvanomagnetic crystal Etch in effects. the solution shown. clean Hurle, BI-0009: 1 — BrJ Appl Phys, 11,336(1960) D'T Bi, (111) wafers. A 1HNO3:1H2O solution used at RT, 30 sec as a light figure orientation etch. Quench DI water slowly at end of etch period to reduce formation of hydrated with oxide. BI-0010 NAME: Neon TIME: ETCH Ionized TEMP: preferential TYPE: gas, GAS COMPOSITION: FLOW: x ... Ne+ ion PRESSURE: POWER: DISCUSSION: Bi, crystal specimens. Neon ion single used to develop structure and bombardment orientation figures. Other metals studied were Al, Cd, Co, Mg, Cu, Sn, and Zn. REF: Yurasova, V E — Kristallografiya, 2,770(1957) © 1991 by CRC Press LLC

172 159 BI-0012 NAME: TIME: ETCH defect Cleave, 195°C TEMP: TYPE: - COMPOSITION: cleave ... x DISCUSSION: cleaved in LN2 and used Bi, cleaved" in a study of thermodynamic (0001) wafers "as liquid helium temperatures. Surface defects properties cleaved wafers can be used for at on orientation the specimens. bulk of 98,359(1955) M & Babiskin, J Steele, Phys Rev, C REF: — _____ ETCH NAME: Nitric acid TIME: Acid, cutting TEMP: TYPE: RT COMPOSITION: ... HNO3 x DISCUSSION: absorption specimens used in a cyclotron alloy study. Wafers were cut and bismuth Bi by acid saw cutting using a linen string saturated in nitric acid. Specimen from ingots surfaces lap polished on 2/0 emery paper with a solution of 2 kerosene: 1 MeOH mechanically after cut. being Rev, Kalt, K et al REF: Phys J 114,1396(1959) — BI-0014b ETCH NAME: TIME: TYPE: Acid, polish TEMP: 70—100°C COMPOSITION: 1 HC1 ... ... HNO3 2 H2O 3 ... DISCUSSION: bismuth alloy specimens etched polished Bi this solution after acid saw cutting and in Residual film remaining after etching in solution shown (BI-0014a). a 5 sec removed by dip concentrated HNO3 at RT. in Ibid. REF: Bl-0016 NAME: Nitric acid TIME: ETCH Acid, TYPE: TEMP: removal COMPOSITION: x ... 20% HNO3 DISCUSSION: Bi, specimens. Material used in a study of ultrasonic attenuation of bismuth at low temperatures. Etching a polygonized subsurface layer about 10' thick is formed showed lapping a during fine crystallite zone. as Reneker, REF: — Phys Rev, 115,303(1959) D H BISMUTH ALLOYS, BiM, General: Do not occur in nature as bismuth metallic compounds, though there are a oxides, number bismuth minerals, mainly as sulfides and of with or without other metal elements. © 1991 by CRC Press LLC

173 l<*0 CRC of Metal Etchants Handbook metal has a melting point (27°C) and, as an industrial alloy with other Bismuth low specific wide a low temperature solder with as melting temperatures controlled has use metals, amount of additive metal: Wood's Metal by or Rose Metal the (50Bi:25Pb:12.5Sn:12Cd) as (50Bi:40Pb:22.9Sn) examples. of No application in Application: fabrication direct Solid State devices, Technical the used as a low temperature alloy solder. Available from suppliers in rod, wire, or though cut pre-forms. may be used as a fuse in package assembly design as part of a protection Wire circuit. for have been grown as single crystals alloys general morphological Several bismuth defect studies. and/or Varies with compound — aqua regia types, cyanides as acid mixtures. Etching: ALLOYS BISMUTH ETCHANTS BISMUTH:ANTIMONY BISB-0001 TIME: ETCH NAME: TYPE: dislocation TEMP: Acid, COMPOSITION: ... 7 HNO3 4 tartaric acid, sat. ... sol. 1 ... H2O DISCUSSION: BiSb, single crystals Te doped. Wafers were cleaved (111) under LN2 from CZ grown ingots with further treatment prior to dislocation etching. Increasing the Te concentration no dislocation Sn doped crystals also studied. increases the content. Zemskov, V S et al — J Cryst Growth, 71,243(1985) REF: ETCHANTS BISMUTH:CADMIUM BICD-0001 ETCH NAME: TIME: Acid, preferential TEMP: TYPE: COMPOSITION: x K3Fe(CN)6 ... ... EOH x DISCUSSION: After Bi:Cd, single crystal specimens. alloy mechanical polishing, specimens were and preferentially etched in the solution shown to develop defect structure. REF: Savas, A & Smith, R W — / Cryst Growth, 71,66(1985) M ETCHANTS BISMUTH:TIN BISN-0001 NAME: ETCH TIME: Acid, preferential TEMP: TYPE: COMPOSITION: x...K3Fe(CN)6 x ... EOH DISCUSSION: BiSn, alloy and single crystal specimens. After mechanical polishing, specimens were preferentially in the solution shown to develop defect structure. etched REF: Savas, M A & Smith, R W — J Cryst Growth, 71,66(1985) © 1991 by CRC Press LLC

174 161 BIS-0002 NAME: TIME: ETCH polish Acid, TEMP: TYPE: COMPOSITION. HC1 ... 95% ... HNO3 5% DISCUSSION: in a study BiSb the temperature dependence of electrical properties. After alloys used of solution shown specimens polishing annealed. with were Jain, L — Phys Rev, 114,1518(1959) REF: A Bi14Ge3O12 GERMANATE, BISMUTH not occur as a natural compound General: has no industrial applications at Does and present. Application: Both this Technical and the silicate compound are under de germanate velopment applications similar to those of artificial garnets, such as YAG — yttrium for a garnet, isometric system, structure as with cube or dodecahedron. aluminum Y3A15O12, the formula Bi12GeO20 the material is called BGO, the With counterpart, BSO, and silicon both are cubic structure, Space Group 123. also Mixed acids and halogens. Etching: BISMUTH SILICATE ETCHANTS BSO-0001 ETCH NAME: TIME: Acid, removal TYPE: TEMP: COMPOSITION: ... x HF x ... HNO3 DISCUSSION: single crystal Bi12Si020 under development as a compound with similar (BSO) material to those of artificial garnets applications YAG etc.). See discussion under Bismuth (YIG, Germanate for additional information. (BIGE-0001) 7,803(1985) Sterudner, & Zmija, i—J REF: Chem Solids, R Phys BISMUTH GERMANATE ETCHANTS BIGE-0001 ETCH NAME: TIME: TYPE: Acid, removal TEMP: COMPOSITION: x HF ... ... x HNO3 DISCUSSION: (BGO) single crystal material Bi12GeO20 by flux method has cubic structure with grown Space Group 123. With silicon replacing germanium (BSO) the material is of similar struc compounds ture. a material development study for was similar to artificial garnets (YIG This and YAG). {Note: Solution shown is for reference only and can include glacial acetic acid, © 1991 by CRC Press LLC

175 162 CRC of Metal Etchants Handbook or HAc, BRM solutions (x% Br2:MeOH) and iodine solutions (tri-iodide used water, H2O. etc. apply.) gold), also on R & Zmija, J — REF: Phys Chem Solids, 7,803(1985) Sterudner, J PROPERTIES OF PHYSICAL SELENIDE, BISMUTH Bi2Se3 Classification Selenide Atomic numbers 83&34 weight Atomic 654.9 (°C) Melting point 710 Boiling point (°C) Density (g/cm3) 6.25—6.98 scratch) (Mohs Hardness — 2.5—3.5 Crystal normal) — (orthorhombic structure (010) b-pinacoid (solid) Color Bluish grey — distinct) Cleavage (pinacoidal b(010) BISMUTH Bi2Se3 SELENIDE, Occurs as the mineral guanajuatite (frenzelite, selenobismitite), and selenium General: be is in part by sulfur. As a mineral specie it may of rare occurrence and has had replaced application no the metal industries. in V—VI Application: Technical is a Bismuth compound semiconductor, and has selenide been grown as a single crystal in developing etching characteristics and semiconducting properties. It shown as being used as a basal (0001) cleaved wafer, which would be is as system, natural mineral is listed the being orthorhombic system with hexagonal though b(010) cleavage. b-pinacoid HC1 aqua regia. Halogens. Etching: and SELENIDE ETCHANTS BISMUTH BISE-OOOla ETCH Hydrochloric acid, dilute TIME: NAME: Acid, TEMP: TYPE: RT removal/polish COMPOSITION: 1 ... HC1 1 ... H2O DISCUSSION: Bi2Se3, (0001) wafers. Solution used to remove lapping damage and polish surfaces. REF: Faust, W — J Electrochem Soc, 105,252C(1958) J BISE-OOOlb ETCH TIME: NAME: Acid, polish TEMP: RT TYPE: COMPOSITION: 1 ... HC1 2 ... HNO3 DISCUSSION: Bi2Se3, (0001) wafers. Solution used for general cleaning and polishing of surfaces. is (Note: 3HC1:1HNO3. The solution shown regia, a modification, and aqua regia- Aqua type solutions reactivity can be reduced by diluting with water.) REF: Ibid. © 1991 by CRC Press LLC

176 163 BISE-0002 NAME: Water ETCH TIME: oxidizing TYPE: TEMP: Electrolytic, Hot ANODE: COMPOSITION: ... CATHODE: x H2O POWER: DISCUSSION: wafers. Materials Bi2Se3, anodized in a study of oxidation reactions. (0001) cleaved were Also Bi2Te3; p-type GaSe, and GaTe. studied p-type Moritani, et al—JAppl Phys, 126,1191(1979) REF: A BISE-0003 TIME: TIME: BRM ETCH Halogen, TEMP: RT TYPE: polish COMPOSITION: ... x Br2 x% x MeOH ... DISCUSSION: of ingot grown in a study crystal new semiconducting compounds. Other Bi2Se3 single were Ag2Se, Li3Bi, TISe, Tl2Se3, SnSe, SnSe2, In2Tl3, AgInTe2, and In2Te3. compounds 1965.) (Note: BRM for this solution was not in use prior to about term The REF: E & Pearson, W Mooser, — Phys Rev, 101,492(1956) B Bi2Te3 TELLURIDE, OF BISMUTH PHYSICAL PROPERTIES Telluride Classification 83&52 numbers Atomic 800.83 Atomic weight 573 point Melting (°C) (°C) Boiling point 7.642 (g/cm3) Density 1.5—2 Hardness scratch) (Mohs — (1011) (bladed) rhomb rhombohedral) — (hexagonal structure Crystal grey Steel (solid) Color (0001) perfect) (basal Cleavage — TELLURIDE, BISMUTH Bi2Se3 In nature the pure mineral is known as tetradymite, free of sulfur, as the General: normal formula trace sulfur with a density of G shows 7.2—7.6, as Bi2(Te,S)3. There are three = other similar minerals, all of which occur in association with gold-bearing quartz veins. There is use in the metal industries, although there is major use of metallic tellurium. no Application: is telluride Technical a V—VI compound semiconductor, and has Bismuth semiconducting been etching characteristics and for properties, along with both evaluated lead and zinc tellurides. It has been fabricated for its optoelectronic characteristics as a laser and and both in its single crystal form diode, as a deposited thin film electroluminescent element. Etching: Single acids and mixed acids of HF:HNO3, HF1:HNO3. BITE-OOOla NAME: TIME: 1—2 min ETCH TYPE: Acid, preferential TEMP: RT © 1991 by CRC Press LLC

177 164 CRC of Metal Etchants Handbook COMPOSITION: 1 ... HC1 HNO3 2 ... ... H2O 6 DISCUSSION: used to develop etch Bi2Te3 (0001) on single crystal wafers. Pits wafers. Solution pits on three alternate were Following etching, rinse in water and dry on filter truncated sides. {Note: SI-0092a-b for discussion of See hexagonal pit development.) paper. truncated Toramoto, I & Takayangi, S REF: Appl Phys, 32,118(1961) —J BITE-OOOlb NAME: TIME: min ETCH 1—2 preferential RT Acid, TYPE: TEMP: COMPOSITION: IO111I...HNO3 ...HC1 10 ml 40ml...H2O lg ...I2 Mix iodine in HC1 and heat Note: 60°C, then cool to RT before adding other constituents. to DISCUSSION: triangular (0001) This etch will Bi2Te3, wafers. etch pits. After etching, rinse develop specimens in ethyl alcohol. {Note: Methyl alcohol could be used as a final rinse as it is a good solvent residual iodine.) for Ibid. REF: BITE-0002 TIME: ETCH NAME: Acid, removal TEMP: TYPE: COMPOSITION: 1 ...HNO3 HC1 ... 1 2 ... H2O DISCUSSION: (0001) wafers. Described as a n-Bi2Te3, etch for n-type bismuth telluride. "removal" {Note: BT-OOOla.) Soc, Drabble, R et al — REF: Phys T 71,568(1958) Proc BITE-0003 ETCH NAME: Water TIME: TYPE: Acid, oxidation TEMP: Hot COMPOSITION: ANODE: ... CATHODE: x H2O POWER: DISCUSSION: (0001) cleaved p-Bi2Te3, Also p-GaSe, p-GaTe and Bi2Se3. Materials were wafers. anodized in a study of oxidation reactions. J REF: et al — A Appl Phys, 126,1191(1979) Moritani, BITE-OOOlc ETCH NAME: Nitric acid TIME: 1—2 min TYPE: Acid, preferential TEMP: RT © 1991 by CRC Press LLC

178 165 COMPOSITION: 30% x HNO3 ... DISCUSSION: bismuth develop hexagonal etch pits in to telluride speci wafers. Used Bi2Te3 (0001) truncated similar to those obtained in etch BITE-OOOla. Pits mens. were Ibid. REF: BITE-0004 Nitric ETCH TIME: NAME: acid, dilute removal TEMP: TYPE: Acid, COMPOSITION: HNO-, ... 1 ... H2O 1 DISCUSSION: and used developing structural-cell data in the coefficients of Bi2Te3, (0001) wafers of this material. After mechanical lap and polish, solution shown was used to expansion residual remove strained surfaces. damage, e.g., M — Br J Appl Phys, 11,415(1960) Francombe, H REF: M H — Br J BT-0005: Phys, 9,415(1958) Francombe, Appl (0001) studied and etched wafers shown under BITE-0004. Bi2Te3 as PROPERTIES OF BISMUTH TRIOXIDE, Bi2O3 PHYSICAL (BISMITE) Oxide Classification 8 & 83 numbers Atomic 466 Atomic weight 860 (°C) Melting point (°C) Boiling point 8.5 Density (g/cm3) 1.81—2.00 index (n =) Refractive 2—3 — (Mohs Hardness scratch) (hexagonal — rhombohedral) rhomb (1011) Crystal structure artificial (orthorhombic) (hkO) prism Straw yellow Color (solid) (basal) (0001) Cleavage TRIOXIDE, Bi2O3 BISMUTH an natural bismite, Bi2O3, is General: mineral hydroxide, and only occurs The probably nature as an earthy coating and small scales. In in it is listed as the hydroxide: chemistry Bi2O3.3H2O. has little use in the metal industries, It in medicine is known as pearl white, but pearl powder, etc. Bismuth metal has wide use as a low melting point solder constituent. Technical Application: compound has had little use in Solid State processing to The thin though is under evaluation as a date, film for its superconducting characteristics. As it a mixed compound: BaPb, xBixO3 (BPB), it is a superconducting oxide used in the devel devices. opment Boundary Josephson Junction (BJJ) of Etching: Soluble in single acids. © 1991 by CRC Press LLC

179 166 CRC of Metal Etchants Handbook TRIOXIDE ETCHANTS BISMUTH BIO-0001 NAME: TIME: Hydrochloric ETCH acid TEMP: removal TYPE: Acid, COMPOSITION: x ... HC1, cone. DISCUSSION: a thin film in study of superconducting oxides. Solution used Bi2O3, a deposited as as patterning removal and etchant. Phys, et — K J Appl al 23,L115(1984) REF: Moriwaki, Jpn BLISTERS occur in natural rock formations as General: or vugs, often produced Blisters cavities gas (water vapor or others) during solidification. Such structure is common by expansion lava northern . . jagged type lava, such as in AA California ... as against Poi-Poi lava . to volcano — represented by the Mauna Loa as in the Hawaiian Islands. Pumice rope-like — a solidified froth of silica, SiO2, as a volcanic extrusion from an acidic magma with a is void density that produces a very lightweight rock used in construction and as a lapping high The so-called 'dinosaur eggs" are concentinary nodules that can range from pea size stone. ' than being foot in diameter, fist-size greater most common, and are a segregation to a beds. silica often found in sedimentary most When completely filled, they solidification of varicolor agates and, if only partly filled, may contain fine clear or colored produce single crystals quartz. Cavities in other rocks may be similar as partly or completely filled by of In intrusion waters producing vein deposits. siliceous obsidian (natural glass) subsequent of may be segregated blebs of calcite, CaCO3. there . "snowflake obsidian". Clear, single . crystal sometimes contains bubbles or voids quartz some crystal plane structure con with taining either entrapped gas or liquids, and the gas/liquid is used in determining the age and atmospheric conditions formation. Incrustations as drusy coatings on rocks and minerals of show blisters voids with similar entrapped gases and liquids, though less may or contain a with volcanic rock, often contains many small cavities filled Basalt, common. common or minerals. segregated blebs silica other compounds the of on and metallic surface are an unwanted phenomenon Blisters metals metal processing — the slow weathering of iron to iron oxide (rust) — very often in forms a surface, such that most construction irons and steels are coated with red-lead to blistered are or Most metals and compounds oxidation. measured for their porosity reduce prevent the number of voids in the material sometimes — produced for a specific intentionally product. associated are natural forms as blisters These all blebs, voids that can be involved or with blister formation. Technical Application: is ongoing study of the formation of blisters and devel There films of solid metals or compounds and thin in as they occur under different opment voids conditions. processing irradiation produce a surface can Any both surface blisters and internal voids. Ion of etc., implantation particle or ionic gas irradiation, radioactive such as Ar+ ion cleaning (P); — all can introduce physical damage within a material that can lead to blisters. If the material layers, has grain structure, such as in thin film metal or epitaxy compound crystalline a there be grain-boundary in-or-out-diffusion of both can and gases creating voids liquids internally or blisters on surfaces. where Much adhesion of thin films, involves they are evaporated, sputtered, concern epitaxially grown, or plated, as all such process steps may introduce entrapped gases or © 1991 by CRC Press LLC

180 167 liquids, that subsequent heat treatment will develop surface blisters with lifting, peeling, such loss of And it often is not apparent until material is heat treated above 400 and adhesion. . . blisters can be observed to start as low as 150°C in a thin film metallization to 500°C . part hot in air. It should be noted that if the a is heat treated in an air oven, on heated plate or a furnace — N2, H2 or other atmosphere — blisters may not appear, yet will in vacuum, the same part is placed on the hot plate in air. Plating solutions can develop appear when if when metal concentration becomes low or plating gas and liquids spontaneously the blisters at the part/plating interface or within the plating are film . . . again, some entrapped metal not until heat treatment. And the preparation apparent surfaces prior to any thin times of deposition can be extremely critical: 2 fim" finish film substrates are an exam alumina ple they are polished with diamond paste, and paste oil can be entrapped in the fine ... cracks . . hydrogen firing at 800 to 900°C was found to be the best method of surface . organic surface other contamination on a Any can be a factor causing subsequent cleaning. or blistering. introduce metal elements in processing can of stress and strain with the The interaction of new compounds due to solid-solid diffusion. Silicides are an example of formation controlled formation a new compound but, if they fail to operate as a buffer layer and of a with such as with aluminum in elements, multilayer structure, another crystallite react other can develop with expansion causing swelling, stress, and form within the bulk and strain eventual or void formation. Where a silicon blister layer is used as a diffusion mask, dioxide as against boron, it can develop a "rosette" crystalline structure in the otherwise amorphous film as borosilicate glass, and such structures have been referred to as blisters. a time under electrical load or during temperature evaluation of multilayer With operating where also solid-solid diffusion. In one example, be cobalt is a metal there can devices, was shown to migrate to wire constituent, device contacts causing embrittlement it bond contact Silver, in particular, but also gold failure. aluminum thin films have been and and to *'creep" with time and temperature or under electric bias with subsequent device known to include swelling, blistering, and contact void formation. The occurrence of "purple failure, failure as of AlxAuy has long been known as a device forms mechanism, plague" crystal swelling, blistering, embrittlement, and operational failure. again, Purple Gold (70Au:21 Al) is used in Note: jewelry trade and as a decorative finish. the BLISTER ETCHANTS BLIS-0001 ETCH Water TIME: NAME: Acid, diffusion TEMP: RT TYPE: hot to COMPOSITION: x ... H2O, liquid/vapor DISCUSSION: GaAs, (100) wafers doped p-type (Ge) and n-type (Si) and used as substrates for se quential sputter Ti and Pt, then annealed at 450°C, 2 min in an open tube with FG will of tops. blisters diameter with pinholes in blister fxm To clean substrates (1) produce 5—6 and strip with HF; (2) boil in chloroform; (3) oxidize in acetone; (4) boil in MeOH; boil (5) dry; (6) swab with 1HC1:1H2O; and N2 NH4OH rinse to remove residual oxide. (7) Surface treatment had no effect on blister occurrence; no blisters with Ti, only. TiPt voids, film with grain boundaries and micro polycrystalline and Pt will catalyze H2 and is O2 in water vapor at elevated temperature . . . nucleating blister-type points in film from of water/gas . plastic deformation and rupture . . blisters can result. As Au/Ti/Pt expansion the film will blister but not rupture due to gold malleability. A solder bonding flux © 1991 by CRC Press LLC

181 168 CRC of Metal Etchants Handbook ZnCl2:NH4Cl:H2O produces with both corrosion and blisters. Heating above of HC1 blisters 375—450°C delamination of films. and develops gas-induced — Solid Films, 109,155(1983) G REF: Henein, Thin BLIS-0002 Oxygen NAME: ETCH TIME: TYPE: Gas, diffusion TEMP: Elevated COMPOSITION: Air, H2, O2 x ... DISCUSSION: thin Gas diffusion into films forms bubbles along grain boundaries with 1.8 Au films. film energy gas entrapped in voids during with growth. Voids unstable below eV activation few hundred angstroms in size, but stabilize by gas filling as bubbloids or poroid bubbles. a Andrew, REF: & Lloyd, J R — Thin Solid Films, 88,125(1982) R BLIS-0003 ETCH TIME: NAME: Irradiation damage TYPE: TEMP: Proton, COMPOSITION: H+, H3 — x H2, DISCUSSION: #6061-Tg Al Proton irradiation at 100 and 200 KeV at -196, -100, alloy sheet. and + 200°C. Large and small blisters, +100, and elongated appear aligned in the round sheet direction after irradiation. At 200°C blisters appear only at grain boundaries. By roll grain heating at 300°C blisters appear at min boundaries and on general surfaces. After 10 scratching a surface, then 100 KeV rad and 20 min at 250°C anneal, blisters appear along cracks — in size as circular blisters with added 10 min at 350°C. Proton beam was increase blister Entrapped with heat expansion was cause of gas occurrence 48H:32H22OH3. hydrogen the solid material surface. in Milack, T et al — Thin Solid Films, 88,2805(1982) REF: Daniels, F A & Cooley, BLIS-0004: — Thin Solid Films, 88,2815(1982) R work that of Milack, BLIS-0003. Similar to BLIS-0005 NAME: Air TIME: 6 min ETCH Gas, TYPE: forming TEMP: 300°C blister COMPOSITION: ... H2, O2, air x DISCUSSION: Au/TiW thin films on Al film deposited on (111) silicon wafers. At temperature and time shown alters from fee to bec cubic structure and, when heated in air, becomes Au in gold. due to aluminum diffusion into silvery Gold on Al/Si (111) developed round, color final doughnut ring blisters?). As Al/TiW/Si with (collapsed Au coating on Al at 300°C spots becomes a silvery colored surface with blisters due to gas grain boundary diffusion (GBD). Addition Nitrided convert from bec to fee. films of N2 improves barrier effect against TiW Al solid-solid diffusion. Some films were TiO3WO7. — REF: R S et al Nowicki, Thin Solid Films, 53,195(1978) © 1991 by CRC Press LLC

182 169 BLIS-0006 Helium ETCH TIME: NAME: ion, gas 900°C implantation Ionized TYPE: TEMP: FLOW: GAS COMPOSITION: ... x ion PRESSURE: He+, POWER: DISCUSSION: Blister He+ implanted at 0.5—1.5 MeV. ion shapes strongly dependent blanks Nb, (111) At 900°C developed "crow-foot" blisters with three (112) on prongs temperature. directional preferred (121) orientation. At lower temperatures only round dome blisters and (211), (112), with toward increase as temperature reduced observed RT. Blister density varied were size by the implant beam. Blisters caused of expansion of implanted He\ with direction Das, S K & Kaminsky, M — J Appl Phys, 44,2520(1973) REF: BLIS-0007 ETCH TIME: NAME: Oxygen TYPE: crystallization 500—550°C Gas, TEMP: COMPOSITION: x ... O2(air) DISCUSSION: metallized structure. With heating all of the Al/TiW/PtSi/c-Si crys substrate following can Al2Pt, A1I2W, WSi2 and TiWSi. occur: O2 present: Al/TiWO. Surfaces tallites With pinhole blisters due to expansion and stress of Al2Pt regrowth, formation, etc., developed at well gas grain boundary diffusion action. Al deposited from 250°C + O2 developed as as Al/O/TiW structure. an Canali, C et al — Thin Solid Films, 88,9(1982) REF: BLIS-0008 ETCH Boron TIME: NAME: 800°C blister forming TEMP: To Metal, TYPE: COMPOSITION: x 0.05—0.2% B ... DISCUSSION: Ni:B deposited as columnar growth structure. Anneal 4 h at 800°C to form films thin brown angular along grain boundaries with voids Ni2B crystallites growing developing Ni2B, grain boundaries. Annealed 4 h and evaluated at 100°C steps from at to 800°C in vacuum 400 and little change up to 600°C. The bubbles and dislocations appeared at grain showed CVD with boundaries from the surface with 0.2% boron. With deep growth of Ni:B cracks films, bubbles were very fine. REF: Skibo, M & Greulich, FA — Thin Solid Films, 113,224(1984) BLIS-0009 ETCH Kovar TIME: NAME: Metal, TEMP: 200°C TYPE: conversion COMPOSITION: x ... Fe, Ni, Co DISCUSSION: Annealed Au/Fe, Au/Co thin film metallization. and at temperature shown, metals Au/Ni will diffuse into overlay gold. Under oxidizing conditions Fe + SiO2 will develop Fe2O3. reactions The for observation of metal diffusion was in Kovar used in device package study construction. It was seen that solid-solid diffusion into gold can develop surface blisters. — REF: W E et ai Schwartz, Thin Solid Films, 114,349(1984) © 1991 by CRC Press LLC

183 170 CRC of Metal Etchants Handbook BLIS-0010 ETCH TIME: NAME: Metal blister TYPE: 200°C and above forming Metal, TEMP: COMPOSITION: Ga x or ... Sm DISCUSSION: The deposited onto Au:Sm (100) substrates. films Ib group of and Au:Ga thin NaCl, rapidly into group Ilia elements IVa elements. Au/Ga and Au/Sm act as will diffuse and with stress differentials causing large blisters diffusion 1.5 mm size as couples diffusion — with a 4*T"-shaped crack dome on top surface of blisters. Blisters tend to blisters rupture along steps on the NaCl surfaces. Segregated white spots appear in films as align cleavage grains, grains. Blister areas were orange in color as pure Au as cracks were Au2Ga other Kirkendall volume and to change was caused by interdiffusion. due voids Thin Nakahara, Kinsbron, E — & Solid Films, 113,15(1984) REF: S Nakahara, S & McCoy, BLIS-0011; J — Thin Solid Films, 88,285(1982) R Pd/Sn PdSn2 using tin and Sn substrates. Similar results observed as described in and BLIS-0010. BLIS-0012 Air TIME: 2—5 min ETCH NAME: blister forming To 400°C TYPE: TEMP: Gas, COMPOSITION: Air ... x DISCUSSION: jim" films deposited on 2 and 4 thin finish alumina blanks. As sputter Au/TiW sputter with about 2000 A Au/500 A TiW(Ti 10%) no blisters were present at RT but, deposited 400°C in a hot plate after air, both circular and elongated blisters appeared. Blisters also on following with density variable under the and process conditions: (1) Up- occurred size gold from a standard gold cyanide bath ... (2) plating cleaning rinse, H2O rinse, then HC1 direct gold up-plate ... (3) HC1 rinse to H2O rinse, then electroless nickel 500 A and coating, followed directly by gold up-plate ... (4) no cleaning of sputtered gold surface prior to or Au/Ni plating ... (5) air oven cleaning evaporated gold surfaces at 150°C Au 2, 4, and 24 h prior to Au or Au/Ni plate ... (6) hydrogen firing of alumina at 800°C for 6 initial evaporation. sputter to Fused quartz blanks similarly processed as a prior Au/TiW The the and 4 fim" alumina blanks. against 2 |xm" alumina showed worst-case control 2 with size, shape (round, elongated or combination), and density-variable blistering with surface before gold up-plating. Presence of HC1 developed both fine blisters and treatment at liquid ruptured blisters, or appeared from grain boundaries, with limited, black extrusion distribution vs. total blister density. Air oven bake erratic the number of large reduced blisters, increased the density of small blisters. but thick nickel layer (about 2000 A) A developed large, circular blisters with complete pop-out and silvery discoloration of Au surface. Hydrogen of alumina blanks prior to any metal evaporation reduced but did firing Ti, eliminate with up-plated Au. Au or blisters only, did not produce blisters. TiW, not all developed cracks and peeling associated with crack locations only, the alumina blank in surfaces. sputtered films, only, and soaked time at With in air on a hot plate, a glassy 400°C WOX dark grey Him with some spectrum colors appeared on surface of gold without blistering. lesser The alumina finish blanks showed a much fxm" blister density with larger size than 4 with 2 |im" finish. The presence of entrapped gas, oils, and liquids, and the solid-solid of diffusion were considered as the causes TiW blistering. Blisters developed on quartz of substrates only when TiW was present, not with other metal combinations. Since these initial © 1991 by CRC Press LLC

184 171 experiments performed, it has been shown that slow, step-heating of Au/TiW thin films were prevent solid-solid of the TiW fractions that cause blistering. will diffusion P & N — personal development, 1984—1985 REF: Walker, Velardi, BLIS-0013 Hydrofluoric ETCH acid NAME: TIME: TEMP: removal Acid, TYPE: RT COMPOSITION: cone. x ... HF, DISCUSSION: evaporated on SST substrates, then aluminum deposited as p-i-n diodes. a-Si:H films thin and lifting observed due to deposit conditions and/or substrate surface Blisters, pinholes, film affects roughness The solar cell efficiency. preparation. surface Mater, B al — J Electron et 13,843(1984) REF: Yacobi, G BONDING natural minerals themselves, as individual components or as mixture General: Many solid bonds. Sandstone is an example of such a two-component bonding components, form sand where, heat and with time, pressure, grains are compacted and cemented system under the intrusion of colloidal iron oxide. The reason that most sandstone is tan to brown in by is presence to the color of the brown iron oxide. The hydrothermal action of hot waters due through subsurface can alter a mineral completely to another compound, percolating rocks as surface deposit a different mineral compound or a firmly attached only alteration, cause Limonite pseudomorphs after pyrite, where the sulfur in surface pyrite is leached coating. the and by oxygen — still retaining the pyrite replaced form as a face striated cube away crystal is an example of complete alternation, called a — pseudomorph after pyrite. limonite Moonstones colloidal to amorphous silica nodules found along seashores — are often — sulfate coated very hard coating of calcium/magnesium a or mixed oxide, white surface with color, and silica is a common drusy surface coating on in rocks and minerals which many may fine crystals, in part. Both air and water be oxidize the surface of a mineral as a can metal oxide surface coating. Petrified wood or wood opal are special cases, where siliceous waters have the cellular structure of the buried wood forming a hard silica rock — entered eye or eye semiprecious gem stones are similarly silicified asbestos minerals. cat's tiger some of compacted mixtures of different minerals, are acting as the bonding types rock Many as mica or hornblende granite or graphic granite. medium, latter as silica in an such The cellular which is filled with the softer structure which are white, pink, and open feldspars, colors of the feldspars. When polished, they grey-blue fine ornamental stones. make In much of metal fabrication involves some form of bonding within the metal industry, to metal and steels are heat treated Irons develop specific structural bonding, or mixture. as the alpha, beta, and delta phases; formation of such iron carbide as Fe3C, etc. marcasite; Other are bonded together by pressure and metals — called cladding — such as a heat copper/gold strip. Metal evaporation or plating form thin film coatings intimately bonded to a Coldweld sealing uses direct pressure, only — 5 to 20 tons — to form copper- surface. or waters bonds by metal cross-diffusion. Like the natural siliceous copper nickel-nickel a wood, resins and lacquers are used penetrating impregnate linen cloth to form plastic to hard, board with the plastic/lacquer insulating the bonding medium. Shatterproof glass as is fabricated by bonding two glass plates with a thin sheet of plastic between as a sandwich, sometimes or wire grid is embedded in the glass for structural rigidity, metal as an electrical a heater system for deicing glass panes. / There are many laminated products — pressed wood, as plywood, /4s one example — Paper again, etc. as the binding medium. resins, is "loaded" with barium sulfate using powder as a binder to increase weight; colloidal silica is used as a filler and binder in many © 1991 by CRC Press LLC

185 172 CRC of Metal Etchants Handbook in the of fire brick, both silica and graphite are used as binders. applications; fabrication say, there many types of glue used to bond similar or different materials Needless to are coatings cooking applied to Teflon ware for a nonstick surface. together, and are most Solid processing probably the State important bonding Application: Technical In wire bonding of devices, substrate circuits, and package assemblies. Several applications are etchant in the this section cover such bonding as methods, rather than etching of formats solutions. of bonding areas described in the General section above apply to Solid Many State the to equipment used in both regard operation and device assemblies. The with products as Etchant includes some bonding techniques here well as cleaning so following Section — see the Mounting Materials lutions for additional information. section Etching: alkalies, alcohols, solvents, variable with material. Acids, ETCHANTS BONDING BB-0001 Ball NAME: Seconds bonding ETCH TIME: TEMP: bonding to 150°C Wire, TYPE: RT COMPOSITION: Au, Al, Ag, Cu x ... wire DISCUSSION: technique. Wire is fed down through bonding vertical capillary tube with a ball Ball a by a hydrogen flame cut-off at the tube tip. Lower tube so that the preformed wire formed is in contact with the contact pad to be bonded. With a combination of time and pressure, ball hemispherical or and ultrasonic vibration, a heat bond contact about 3—4x with without wire diameter is formed on the contact pad. the diameters range from .0007 to about Wire .010. soft .0007 gold wire is Dead for microelectronic circuitry, and Au:Be(2—5%) common used with automatic bonders where a stiffer wire is required. Wire is supplied on spools of 100 to ft. If cleaning is necessary, vapor degrease with TCE or rinse in alcohols with 500 oven bake 125°C. If bond wire fails to stick: (1) RF plasma clean device or substrate air, at or (2) ion plasmas, 5—10 min, and O+ check hardness of the metal pad surface. with N+ oils; first the surface may be contaminated with case, whereas in the second case, In the processing may have hardened the pad, such that a prior wire bond will not stick. soft Aluminum can have an oxide layer (use ultrasonic in bonding). Gold pads as an pads in multilayer common contact pad a high frequency microelec Au/AuGe/Ni metallization, devices, can be excessively hardened by the annealing tronic following metallization. step If occurs, the only correction is to this an additional soft gold evaporated layer before add the wafer is diced into individual units as, once diced, the entire dice lot will be rejects. Ball bonding still widely used, but is limited to a pad area larger than the formed ball is such use it is of limited bond, in high frequency microelectronic circuitry where bond that bonding, pads 5 mils square in area. After under spray clean contacts with acetone; rinse are in MeOH, EOH, Freons, or other solvents. The capillary tubes used for wire feed have a as rounded that should be free of chips and kept clean, e.g., solvent clean end needed, tip or Bonding tips are of replace. ruby, or titanium and tungsten. glass, REF: Harman, G G — Solid State Technol, 1984, 186 B8-0002 NAME: Wedge bonding TIME: Seconds ETCH TYPE: Wire, bonding TEMP: RT to 150°C COMPOSITION: x ... Al, wire © 1991 by CRC Press LLC

186 173 DISCUSSION: bonding technique. solid wedge-tipped rod of tungsten, titanium, steel, etc. Wedge A is flat slightly curved edges to prevent cutting action during pressure bonding. Tip face with in device, on aluminum bonding pad of end lower wedge in contact, Place wire position heating pressure ultrasonic vibration with or without and of part. Special apply and controlled .010 aluminum wire to aluminum alloy pads of SCRs. Ultrasonic application: bonding to of breakthrough needed native aluminum oxide films for a good metal/ vibration insure 30 Prior new aluminum wire, heat treat about using min at about 450°C in bond. to metal (FG) for dead-soft condition, as wire-work hardens forming during bonding. gas rapidly in and air dry as needed after bonding. Rinse alcohols B et al — personal application, 1970—1976 REF: Topas, BB-0003 NAME: Foot bonding TIME: ETCH Seconds TYPE: bonding TEMP: RT to 150°C Wire, COMPOSITION: x wire ... Au, DISCUSSION: bonding called wedge bonding). Bonding (sometimes is a capillary Foot technique tip an upper round shaft for position holding, being cut tube to a rectangular tip with down — face or with convex or concave flat — back-end sharp ledge; front-end curved face center Lower back of tip has extended portion with angled hole for wire to upward. drawn down be and tip face toward the front, facing the operator. Bond flat about .005 width (.002 across and ball- to .0007 length. Bonding is similar to ball bonding without H2 special) .0005 cut-off. ruby, material is of tungsten, titanium, forming etc. Gold wire, .0007 diameter Tip or common; automatic bonders, supplied on 100 for 500 ft spools. With time, wire- AuBe work hardens on spool and shows excessive breakage. Bonding is like ball bonding with the wire brought down in contact with the gold done pad of device, then pressure, with or without ultrasonic vibration (minimum) bonding the The widening formed is elongated — a .0007 wire applied. to about .003 (with an is bond human tip with much the appearance of a width) foot, hence the method name. initial .002 bonding most common, where the initial bond is on Forward device, second bond on a the substrate package pad, but back-bonding can be done ... the reverse of forward bonding. or of "stitch food bonders have the capability of Some bonding", where a multiple line these With bonds made before final bond-end break off. of the relatively flat foot bond, it is is possible to make bonds-on-top-of-bonds . . . "stack bonding". As many as four wires have been so bonded with device pad-pad, pad-substrate, pad-package bonds coming from stack single contact of the device. a pad L Marich, et al — personal communication/application, 1980—1986 REF: A BB-0004 Weld TIME: ETCH NAME: bonding Part, bonding TEMP: Elevated TYPE: COMPOSITION: x Cu ... DISCUSSION: bonding technique. Two opposed Weld electrodes or metal tips similar to a carbon soldering iron, and may be a ring-shaped metal electrode. The wire to be bonded is held an on and welding is accomplished from area, electric spark from the carbon electrodes, bond or an electric pulse from a metal tip. The weld is usually as a cup-shaped joint with some surface weld metal erosion points of the and being bonded. The standard welding splatter techniques use a gas torch with a welding rod material fed against the part or parts being © 1991 by CRC Press LLC

187 174 CRC of Metal Etchants Handbook such as bead-welding a seam, or spot welding. An electrode spark is also used joined, in a to for spectrographic analysis of constituent elements. metal/compound vaporize surface torches requires a similar manner to metal welding, and uses controlled Glass welding in in welding. such as borox are used fluxes welding, clean with water after annealing Where solvents designed for the particular flux. Alloy brazing or a form of high commercial is welding used with alloys above 800°C. Below 800°C it is called soldering. temperature and P personal Tarn, W H — Walker, application (all), 1950/1985 REF: & BB-0005 NAME: bonding TIME: Variable Alloy ETCH Wire, TEMP: RT and 800°C TYPE: bonding COMPOSITION: ... Au, Al, etc. x DISCUSSION: Alloy technique. There are hundreds of alloys available with temperatures bonding from about to 800°C (800 to 2500°C for brazing rather than alloying). Two of ranging 50 common (m.p. are #62 60Pb/40Sn, more 180°C), and #63 (m.p. 220°C) the solders the ... also called 60/40 solder and former most common general solder. Pb/Sn/Ag(5%) the is done with a solder iron using solid or Bonding wire, or a solder pre-form and rosin-core heat. may be pre-tinned for assembly, such as for a PCB, and passed through a furnace Parts a propane; torch, such as or acetylene or oxy-hydrogen may be used depending upon gas directly required. used to solder wire Occasionally to a discrete device, more temperature often used for final attachment of wires internally or externally in package assemblies. Where a resin solder or flux is applied in alloying, bond area should be solvent or alcohol core after bonding remove residual flux. Note: Remaining flux and some commercial cleaned to water contain may will attack assembled components, but good chemicals solvents that is often sufficient for cleaning. washing Tarn, W H & Walker, P — personal application, 1950/1985 REF: BB-0006 ETCH Epoxy bonding TIME: 30—60 min NAME: Parts, bonding 120—150°C TYPE: TEMP: COMPOSITION: ... x or polyimides Ag-epoxy DISCUSSION: paste technique. As an electrical contact both epoxies and polyimides Epoxy loaded are with particles of Ag, Au, Al, Cu, Ni, Pd, fine etc. as a paste. Used unloaded for general Pt, bonding of parts where electrical continuity is not required. Pastes are applied to the wire/ bond pad, device or wire positioned, then the assembly is oven-cured with time and the Widely depending particular compound mixture. the used in microelec temperature upon circuit assemblies for testing, but not in final high reliability tronic Cure schedules packaging. range about 10 to 45 min at 120 from 150°C, and there is ongoing development of higher to temperature pastes (>250°C). Epoxy type pastes do not require cleaning after cure. Alloy base pastes beads of the alloy in a resin fine are similarly used with heat melting, and with do require final cleaning. See BB-0005. S REF: A & Rodriguez, L — personal communication, 1979 Marich, BB-0007 ETCH TIME: 10—20 sec NAME: TYPE: Acid, cleaning TEMP: RT © 1991 by CRC Press LLC

188 175 COMPOSITION: ... H2O2 1 HC1 ... 1 DISCUSSION: diodes. wire leads to discrete silicon attaching Copper, dumet, Pb/Sn joints solder type wires attached vertically by soldering to the aluminum, surface. Operation and silver device or a carbon/metal holding fixture and parts with through a furnace in hand done by passed an forming gas atmosphere. Solution used for light cleaning of formed bonds, following N2 or water then alcohol rinsing and air dry. with rinse, P personal application/development, 1950—1970 Walker, — REF: BB-0008 Alcohols/solvents TIME: 10—30 ETCH NAME: sec Alcohol, cleaning TEMP: RT to hot TYPE: COMPOSITION: x (1) MeOH, EOH (2) x ... TCE, TCA, Freons ... DISCUSSION. solder joints other metal alloys. Both alcohols and solvents used as general Pb/Sn or often for to parts. Water only is alloying sufficient for removal of residual cleaners wire fluxes — borax a major flux — used at RT or hot. Some solder fluxes contain fluorine solder compounds, that particular care should be exercised during cleaning (CaF2 standard such flux). metal Fahr, F — personal communication, 1957 REF: BB-0009 ETCH Cladding TIME: NAME: Pressure, bonding TEMP: TYPE: to molten RT COMPOSITION: x ... pressure DISCUSSION: Metals, plastics, cloth, and wood. Dissimilar metal sheets or strips are formed with pressure/heat by thin sheets/strips through rollers with sufficient temperature to cause passing migration at interface to form a bond by pressure extrusion. A similar process metal-metal the other used or woods using glues or plastics binders, and called veneer. Plasticizing is with include additional adhesives, or applied as impregnation. Linen cloth sheets are plastic may under impregnated to form a nonconductive board (PCBs); sawdust, plant and hair pressure asbestos, are wool, wood pulp, mica flakes, fibers, all used with various chemical glass shapes. binders, as sheet, blocks, or other press-formed Mica and glass wool products and are replacing asbestos for insulation. Plasticized veneer, for relatively chemically inert table tops in is replacing natural soapstone, or marbles. Glass-to-metal tube as a laboratories, seal metal-to-glass made for fabricating graded assemblies; metal wires are glass-beaded is melt/press for in package fabrication with feed-thrus insertion. Mylar (red, blue, insulated white) sheets are pressure clad to clear acetate sheet, as rubylith for photolithographic circuit wafer fabrication with a sticky back is used to hold a mylar in place for scribe & break or, wafer dicing. REF: Siracusa, M et al — personal communication, 1980 BB-0010 NAME: Coldweld TIME: ETCH TYPE: Pressure, bonding TEMP: RT COMPOSITION: PRESSURE: 2—20 tons x ... pressure © 1991 by CRC Press LLC

189 176 CRC of Metal Etchants Handbook DISCUSSION: Copper clad/plated shim steel or pure nickel Solid State packages with a seal or nickel rim lip package sealing of both SCR Hockey Puk, and quartz radio frequency used or for pressure, coldweld is rated for tons of direct system with 5—7 tons as A packages. sealing is an upper and lower die operated by a hydraulic press and the two dies nominal. There surrounded may individual cylinders that mesh for a vacuum seal pulled to about 10 ~3 be by capable pulling gas back-fill after and vacuum. Bottom and top die are individually Torr, of to for package configuration. The package body specific be sealed is seated designed each the lower die, the cover positioned on the package, then the upper die activated to lower in pressure seal. This produces a copper/copper or nickel/nickel metal seal, and eliminates and weld splatter observed in resistance welded packages. Small quartz crystal and any as type 2—5 have been sealed at TO-5 tons pressure; larger silicon semiconductor packages Quartz Hockey at 6—10 tons pressure. packages crystals packages have been SCR Puk in a vacuum system at the 10"10 Torr level or, sealed after vacuum pull and backfill sealed He N2/He with (15%), to reduce mass loading effects using helium as a lightweight or be within Package surfaces to be sealed should package. degreased and dry atmosphere the assembly. before Walker, P — personal application, 1968—1969 REF: BB-0011 ETCH Resistance weld TIME: Seconds NAME: Electric, TEMP: RT TYPE: weld PRESSURE: 10—200 psi COMPOSITION: ... power POWER: 1000—1500 V x DISCUSSION: A standard Raytheon type resistance welder uses a capacitor bank discharge to effect the weld steel package parts, which may or may not be gold plated. The system contains on copper bottom holder and top head for pressure and power discharge, and there a package systems the weld splatter inside the package. These of are still a major method is possibility sealing Solid State packages. Another system uses a powered roller head somewhat like of glass that, tool a as it is rolled across the sealing surface, produces a bead of microspot cutter for may and the head and/or package welds be heated during weld passes. It has sealing, more been circular packages, but it is now on widely used on steel square and flat used paks in Solid State assembly. This operation requires four individual weld passes with 90° rotation after two parallel weld passes. The weld seal produces a very fine weld-bead each minimum internal weld splatter. with package P Walker, personal application, 1962—1980 REF: — BB-0012 NAME: Alloy pre-form TIME: ETCH Metal, Variable TEMP: TYPE: sealing COMPOSITION: x AuGe, AuSn, etc. ... DISCUSSION: metals or metal Pure cut as pre-forms and used for device/part mounting or mixtures package sealing. Operation similar to that discussed under BB-0005 (alloy bonding) as a heated bonding Shaped In, Cu, Au pre-form flats or wires used as vacuum mechanism. cryopumps. crush-seals, indium also used for sealing with Crush-seals do not use system heat, and the pre-form is replaced whenever the system seal is opened and requires re- sealing. al Walker, P et REF: — personal application, 1958—1985 © 1991 by CRC Press LLC

190 177 BB-0013 NAME: Metal TIME: Variable ETCH evaporation cladding TYPE: TEMP: Metal, Variable COMPOSITION: metal ... x DISCUSSION: applied as a Metal cladding. Aluminum, copper, carbon, evaporation when surface etc. have all been used as a thin film metallization on a nickel, of materials: iron, variety metals, mylar, glass, and so forth. Carbon is evaporated on plastic or mylar on plastics, on with sticky-back, used as a sunscreen a windows; aluminum is evaporated sheeting and, plastic or rubber toy balloons, as well as weather balloons for its heat dissipation and on capability. reflective and nickel are replacing silver as mirrors, including telescope Aluminum and are used on clothing. Copper and aluminum flakes or powder are added to lenses, also surface spray as a "glitter" coating and paints sealer. Glassy metals and plastic acrylic-type are evaporated for specific colors of the oxides nitrides nitrides: red, blue, green, gold, or etc. plating has been used in a similar manner for color, and may include color Electrolytic aluminum: additives such as in the anodizing of solution, black, red, green, blue, and so in forth. Spray coating with metal powders are applied to surfaces as a thin film bonded material for both effects and in fabricating Solid State substrates or active devices, such decorative a carbon resistor. Both brass and bronze are used for their yellow color as replacements as film liquid as spray coatings or mixed with direct plastics like aluminum and copper. for gold, Walker, P — personal application, 1955—1985 REF: (mirrors) PHYSICAL OF BORON, B PROPERTIES Metal Classification 5 Atomic number 10.811 weight Atomic point (°C) 2100 (2300) Melting point (°C) 2800 Boiling sub. (2550) Density 2.34 (g/cm3) heat (cal/g) 25°C Specific 0.309 Heat of fusion (k-cal/g-atom) 5.3 Heat of vaporization (k-cal/g-atom) 128 Atomic volume 4.6 (W/D) ionization energy 191 1st (K-cal/g-mole) potential 8.298 ionization (eV) 1st 2.0 Electronegativity (Pauling's) (angstroms) 0.82 radius Covalent radius (angstroms) 0.23 (B+3) Ionic resistivity Electrical 10~6 ohms cm) 20°C 4 (x 1.8 0°C work function (eV) 4.5 Electron (Mohs — scratch) 9.3_ Hardness Crystal structure (hexagonal — normal) (1010) prism, hep Color Grey-white (solid) Cleavage (basal — poor) (0001) BORON, B General: Does not occur as a native element, but is widely found as a constituent in both several such as beryl and chrysoberyl, minerals, beryllium aluminates and major pre- © 1991 by CRC Press LLC

191 178 CRC of Metal Etchants Handbook gem stones, as "Cat's Eye", or yellow and emerald green mock emerald. The cious both SO a group as oxygen salts, some mineral individual minerals, borax, form borates distinctive one of the best known. Boric acid, H3BO3 is of common occurrence Na2B4O7.10H2O, being springs volcanic associated with hot areas. in and metal and little or no use in industry, though nitrides pure borides have appli has The similar dielectrics high temperature ceramics with and characteristics to those of as cation oxide. Boric acid has long been used as a mild antiseptic, aluminum borax is a general and cleaner metal alloy flux, as well as a water softener. and Application: In State processing boron has been the major p-type dopant Technical Solid semiconductor wafers their original development for since devices. Boric acid for silicon first used, then boracine, and then diborane, I^H^ as a gas diffusion was With ion source. implantation, B+ as an ionic species is now used. The diborane also is used for doping I2, drive-in dioxide, for use as a p-type doping SiO2, source, or as a thin film passivating silicon layer with the acronym of BSG. Boron nitride (BN) also is used as a drive-in source with silicon wafers between BN discs. As BC13 as an RF plasma, it is a dry chemical sandwiched thin (DCE) etch removal or patterning of aluminum for films. It is the best etching method to date for such processing due to the inherent difficulty of controlled etching of method oxide device fabrication. aluminum in HNO3, H2SO4, molten salts, and metals. Etching: ETCHANTS BORON B-0001 ETCH NAME: Hydrofluoric acid TIME: Acid, removal TEMP: RT TYPE: COMPOSITION: x HF, cone. ... DISCUSSION: after an amorphous surface B, remaining as ion implantation of boron in silicon layer (100) and (111) wafers. HF used to remove the glassy layer remaining on surfaces after implant. Also on phosphorus and arsenic implantation glassy layers. Acronyms: PSG used ASG, and respectively. Prussin, S et al — J Appl Phys, 57,181(1985) REF: B-0002a ETCH Heat TIME: NAME: Thermal, preferential TYPE: 2000°C TEMP: COMPOSITION: x ... heat DISCUSSION: B, single crystal ingot. During growth and cooling from 2000°C, heat will produce etching: macroscopic similar to that observed by chemical structure hexagonal, spiral, surface pyramidal pits, and oval plateaus. REF: Talley, C P — Nature (London), 182,1593(1958) B-0002b NAME: Nitric acid TIME: ETCH TYPE: Acid, removal TEMP: RT COMPOSITION: x ... HNO3, cone. © 1991 by CRC Press LLC

192 179 DISCUSSION: crystal ingots. B, as a general etch for boron. Sulfuric acid also Solution single used used. can be REF: Ibid. B-0002c TIME: ETCH NAME: Beryllium removal/preferential Molten Metal, TYPE: TEMP: COMPOSITION: x ... Be DISCUSSION: B, nitride test blanks. Metallic beryllium, uranium, nickel, and platinum will as boron boron. Boron Nitride. attack See Ibid. REF: B-0003 RF plasma TIME: NAME: ETCH Ionized growth TEMP: TYPE: gas, COMPOSITION: GAS FLOW: ... BC13 PRESSURE: x POWER: DISCUSSION: films as Describes a method of evaporating the films. and use of ion grown thin B, vaporize the metal and melt the boron as a thin film surface layer. bombardment to Barnes, D et al — Atomic Energy Res Establ (Harwell Mem R/M), 125,4(1951) REF: CARBIDE, B4C BORON PROPERTIES PHYSICAL OF Ceramic Classification 5&6 numbers Atomic 55 Atomic weight 2350 point (°C) Melting 3500 point (°C) Boiling 2.50 (g/cm3) Density 540 air) in Application limits (°C 2260 (°C in atm) inert 2090 Mean specific heat (J/kg °C) 25— 1000°C 5.7 linear expansion Coefficient of thermal 10-6/cm/cm°C) 25—800°C (x 17.3 (w/m Thermal conductivity °C) 800°C) 9.3 Hardness — scratch) (Mohs cube (100) normal) structure — Crystal (isometric Black (solid) Color (001) (cubic) Cleavage BORON CARBIDE, B4C General: Carbides do not normally occur as natural compounds, but are artificially single fabricated different metals. There is a many occurrence of a mineral carbide using called moissanite, CSi, which has been found as small green hexagonal platelets in meteoric SiC. iron Canon Diablo, Arizona. Note that artificial silicon carbide is shown as at the Industrially, carbide is one of boron high temperature refractory ceramics, though © 1991 by CRC Press LLC

193 180 CRC of Metal Etchants Handbook as widely as silicon carbide, but with similar applications as fire brick, furnace not used In tubes, it has been used as a lapping abrasive. powder etc. form, extent, Not Solid State processing to any in to date, other Application: Technical used a lapping and polishing abrasive. There are possible applications as a pressed than as powder for fabrication or in package construction. substrate circuit in Etching: in fused salts. acids. Soluble Insoluble ETCHANTS BORON CARBIDE BC-0001 Potassium hydroxide ETCH NAME: TIME: Molten removal TEMP: 365°C TYPE: flux, COMPOSITION: ... KOH, pellets x DISCUSSION: as pressed B4C, blanks. Material can be etched in fused salts: alkaline hydroxides, powder and carbonates. A Dictionary Carbide Terms — Adams Carbide Corp., Kenil worth, NJ REF: of MBx BORIDES, boron occur in nature as metallic Do compounds, though boron is a con General: not element in many minerals as hydrated silicates, phosphates, sulfides, and carbonates. stituent Na2B4O7.10H2O, Borax, representative of the borate mineral group. is borides a artificially grown in industry as high temperature ceramics with The Mohs are general generally than H = 8. In the hardness formula shown: M = Cr, Mo, Nb, greater U, V, Ta, W, and Zr; and Bx = B, B2, B12, or as a pentaborate, B2O5. The materials are used as furnace tubes, and liners, etc. for their refractive capabilities and general crucibles, lapping inertness. used in powder form as are and polishing abrasives; others chemical Some their dielectric properties in sheet, rod, or flats that are metallized as capacitors or for resistors. Technical No major use in Solid State device fabrication, although there Application: possible assemblies. as circuit substrates and packaging is Some borides are application applications evaluation thin film surface coatings with under similar to those of SiO2 and as A12O3, or as discrete Solid State dielectric elements, sputter evaporated as thin films and planar surface or resistors in circuit fabrication. capacitors have of shown in the following section borides been grown as single crystal Most the for general morphological studies. specimens Boron Nitride and Boron Carbide. See Etching: with compound — soluble in Varies H2SO4, H2O2; alkalies or mixed HNO3, acids; and aqua regia. Note: The are the borides listed: following boride, Tantalum Cerium boride, TaB2 CeB6 Chromium Cr3B2 Titanium boride, TiB2 boride, Molybdenum boride, Mo2B5 Tungsten boride, WB Niobium Nb3B3 Uranium boride, UB2 boride, Rare earth borides, R3Ni7B2 Vanadium boride, VB2 Silicon boride, SiB6 Zirconium boride, ZrB2 © 1991 by CRC Press LLC

194 181 BORIDE ETCHANTS BORIDE ETCHANTS CERIUM CEB-0001 NAME: Heat ETCH TIME: TEMP: Elevated annealing Thermal, TYPE: COMPOSITION: x ... heat DISCUSSION: grown by Czochralski (CZ) method. Also CeB6, were CeCu6, and LaCu6. ingots grown of compounds are orthorhombic in structure. these was grown by arc melting, Both CeAl3 annealed 1 and at 900 to 1000°C. Also grew CeCu2Si2. All materials were used in a week general study. structural Jpn, Onuki, al — / Phys Soc et 4,1210(1984) REF: Y BORIDE ETCHANTS CHROMIUM CRB-OOOla ETCH NAME: acid TIME: Perchloric Acid, removal TYPE: Hot TEMP: COMPOSITION. x ... HC1O4 DISCUSSION: Cr3B2 specimens. Solution is a general etch for this boride. Material used in a composition study. Other borides were Cr2B, Cr3B4, and CrB2O. Compounds will not etch in chromium HC1, or alkalies. HF, HNO3, Ceramics and High Temperature Materials Handbook, Vol 85, #1, Coltronics Corp., REF: 1982 CRB-OOOlb NAME: peroxide TIME: ETCH Hydrogen Acid, TYPE: TEMP: removal COMPOSITION: x... H2O2 DISCUSSION: Cr3B2 specimens. This acid is a general etch for all compounds of this material, as well as other chemical solutions. peroxide Ibid. REF: CRB-OOOlc NAME: Sulfuric acid TIME: ETCH TYPE: removal TEMP: Hot to boiling Acid, COMPOSITION: x ... H2SO4 DISCUSSION: the specimens. Very slow etch attack with this solution, but Cr3B2 higher the metal content, the greater the attack. REF: Ibid. © 1991 by CRC Press LLC

195 182 CRC of Metal Etchants Handbook BORIDE ETCHANTS MOLYBDENUM MOB-OOOla NAME: TIME: Nitric ETCH acid TEMP: removal Acid, TYPE: COMPOSITION: x ... HNO3 DISCUSSION: Mo2B5 is a general etch. Also used on Mo2B; and MoB. Will not specimens. Solution in HC1. {Note: Mixed HF:HNO3 will etch.) etch Ibid. CRB-OOOla REF: MOB-OOOlb ETCH acid TIME: NAME: Sulfuric removal TEMP: Acid, TYPE: Hot COMPOSITION. x ... H2SO4 DISCUSSION: specimens. Solution is a Mo2B5 etch. general REF: CRB-OOOla Ibid. MOB-OOOlc ETCH Sodium hydroxide TIME: NAME: Molten TYPE: removal TEMP: 365°C flux, COMPOSITION: x...NaOH(KOH) DISCUSSION: Mo2B5 specimens. Solution is a general etch. It may be preferential on single crystal material. REF: CRB-OOOla Ibid. MOB-0002 ETCH TIME: NAME: Acetone cleaning Ketone, TYPE: TEMP: COMPOSITION: x ... CH3COCH3 DISCUSSION: of MoB film developed in a study penetration bonding metals at less than 670°C. surface Other metals evaluated were Ni, Fe, Co, Ti, Nb, and Hastalloy B. See Nickel Boride for used details procedure of substrates and borate baths cleaning in process evaluated. See of NIB-0002. REF: Koyama, K et al — J Electrochem Soc, 126,147(1978) NIOBIUM ETCHANTS BORIDE NBB-OOOla ETCH NAME: Sulfuric acid TIME: TYPE: Acid, removal TEMP: Hot to boiling COMPOSITION: x ... H2SO4 © 1991 by CRC Press LLC

196 183 DISCUSSION: specimens. Solution a slow etch on both Nb3B3 and NbB. These borides will Nb3B3 is in: (1HC1:1HNO3). HNO3 or aqua regia etch not HC1; CRB-OOOla Ibid. REF: NBB-OOOlb Potassium hydroxide TIME: ETCH NAME: Molten removal TEMP: 365°C TYPE: flux, COMPOSITION: x... KOH(NaOH) DISCUSSION: specimens. A general etch for this material. {Note: Eutectic mixtures Nb3B3 as lNaOH:lKOH also etch, and may be slightly preferential on single crystals.) will Ibid. CRB-OOOla REF: NBB-OOOlc NAME: acid TIME: Hydrofluoric ETCH removal TEMP: TYPE: Acid, COMPOSITION: X...HF DISCUSSION: Nb3B3 This is a slow etch on this material. specimens. Ibid. CRB-OOOla REF: NBB-OOOld ETCH NAME: Potassium TIME: sulfate TYPE: Acid, removal TEMP: COMPOSITION: x... K2SO4 ... H2O x DISCUSSION: carbonates sulfates will etch this material. specimens. Several will also NB3B3 Some as etch ants. act Ibid. REF: CRB-OOOla RARE BORIDE ETCHANTS EARTH RNIB-0001 ETCH Nitric acid TIME: NAME: Acid, TYPE: TEMP: removal COMPOSITION: x ... HNO3 DISCUSSION: RNi6B2 buttons were grown by arc melting under argon, then each specimen was annealed "R" 2 900°C. In the general formula shown, at stands for rare earth, though other weeks workers use "RE" as the acronym. Here, R = Nd, Ce, Gd, Eu, and Yb. Material used in a and structural study. magnetics REF: Felner, I — J Phys Chem Solids, 44,43(1983) © 1991 by CRC Press LLC

197 184 CRC of Metal Etchants Handbook BORIDE ETCHANTS SILICON SIB-0001 NAME: Water ETCH TIME: TEMP: cleaning Acid, TYPE: COMPOSITION: ... H2O x DISCUSSION: fabricated as 0.5 mm diameter spheres. Water used to clean spheres SiB6 specimens to study of the unit cell space group. prior material is orthorhombic system. Weissenberg The photographs made on the b- and c-axes. were RF Acta Crystallogr, 11,144(1958) REF: Adamsky, — BORIDE ETCHANTS TANTALUM TAB-OOOla ETCH Potassium hydroxide TIME: NAME: Alkali, TYPE: TEMP: removal COMPOSITION: x...x%KOH(NaOH) x...H2O DISCUSSION: TaB2, TaB, and Ta3B4 specimens. This material can be etched in various concentrations of these These borides do not etch in HC1, HNO3, or aqua regia (3HC1:1HNO3). alkalies. Ibid. REF: CRB-OOOla TAB-OOOlb ETCH NAME: TIME: Acid, removal TEMP: TYPE: COMPOSITION: X...HF ... H2SO4 x DISCUSSION: are and specimens. Solutions TaB2 these acids other slow etchants on this material. of REF: Ibid. CRB-OOOla TAB-OOOlc ETCH Sodium peroxide TIME: NAME: Acid, TEMP: TYPE: removal COMPOSITION: ... x Na2O2 x% x ... H2O DISCUSSION: TaB2 and other specimens. The solution is a general etch for this material. Bisulfates as and will also act carbonates etchants. REF: Ibid. CRB-OOOla © 1991 by CRC Press LLC

198 185 TITANTIUM BORIDE TIB-0001 ETCH TIME: NAME: Water cleaning Acid, TEMP: TYPE: COMPOSITION: x ... H2O DISCUSSION: TiC single crystal wafers used in a study of elastic TiB2 Both materials and constants. either (001) or diamond saw cut. cleaved polish surfaces with diamond paste. were Lap with TCE, rinse in Degrease and water. Authors say that both materials appear to alcohol be than diamond. No etch shown. harder Gilman, 32,1406(1961) & Roberts, B W — J Appl Phys, REF: J J BORIDE TUNGSTEN ETCHANTS WB-OOOla NAME: acid TIME: ETCH Hydrofluoric Acid, TYPE: TEMP: removal COMPOSITION: x... HF DISCUSSION: WB2, W2B2, and Beta-WB specimens. A general etch for these materials. WB W2B5, not in HC1; hot H2SO4 or HNO3. will etch Ibid. CRB-OOOla REF: WB-OOOlb ETCH Aqua regia TIME: NAME: Acid, TEMP: TYPE: removal COMPOSITION: ... 3 HC1 1 ... HNO3 DISCUSSION: WB2 and other tungsten borides can be etched in aqua regia. REF: Ibid. CRB-OOOla WB-OOOlc ETCH Sodium hydroxide TIME: NAME: Alkali, removal TYPE: TEMP: COMPOSITION: x... x%NaOH(KOH) x ... H2O DISCUSSION: various WB2 other tungsten borides can be etched in and solution concentrations of these alkalies. REF: Ibid. CRB-OOOla © 1991 by CRC Press LLC

199 186 CRC of Metal Etchants Handbook BORIDE ETCHANTS URANIUM UB-OOOla NAME: TIME: Sodium ETCH peroxide TEMP: removal TYPE: Acid, COMPOSITION: x ... Na2O2 H2O x ... DISCUSSION: UB4, UB12 specimens. Difficult to etch controUably as the materials decompose UB2, and peroxides. in REF: Ibid. CRB-OOOla UB-OOOlb NAME: Nitric ETCH TIME: acid TYPE: removal TEMP: Acid, COMPOSITION: x HNO3 ... DISCUSSION: UB2, and UB12 specimens. Difficult to etch controUably as the materials decompose UB4, in acids. Ibid. REF: CRB-OOOla UB-0002 ETCH NAME: TIME: Cut, TYPE: TEMP: forming COMPOSITION: x ... electricity DISCUSSION: UB, (110) cut single crystal specimens spark cut for fabrication as spheres. Compound has the structure and grows with a preferred (110) orientation. The material is brittle ThB4 fractures Density: on (001) with cubic cleavage. and 3.98 g/cm3. easily Menovsky, al et REF: — J Crystal, 9,70(1984) A VANADIUM ETCHANTS BORIDE VB-OOOla ETCH NAME: Nitric acid TIME: TYPE: Acid, removal TEMP: COMPOSITION: ... HNO3 x DISCUSSION: VB2 and VB specimens. A general etch for these materials. Does not etch in HC1, HF, H2SO4. Ibid. CRB-OOOla REF: VB-OOOlb ETCH NAME: Potassium hydroxide TIME: TYPE: Alkali, removal TEMP: COMPOSITION: x...x%KOH(NaOH) x ... H2O © 1991 by CRC Press LLC

200 187 DISCUSSION: and VB This material can be etched in various liquid concentrations of VB2 specimens. alkalies. Ibid. REF. CRB-OOOla VB-OOOlc Potassium nitrate TIME: ETCH NAME: Acid, removal TYPE: TEMP: COMPOSITION: ...x%KNO3 x ... H2O x DISCUSSION: and VB specimens. Solutions of nitrates will etch VB2 material. Also carbonates, this bisulfates, peroxides. and Ibid. CRB-OOOla REF: ETCHANTS ZIRCONIUM BORIDE ZRB-OOOla Potassium hydroxide TIME: ETCH NAME: removal TEMP: Alkali, TYPE: COMPOSITION: x...KOH(NaOH) x ... H2O DISCUSSION: be Zr3B4, and ZrB12 specimens ZrB, ZrB2, etched in various concentrations of the can alkalies. Will not etch in HC1 or HNO3. REF: Ibid. CRB-OOOla ZRB-OOOlb NAME: peroxide TIME: Sodium ETCH removal TEMP: TYPE: Acid, , COMPOSITION: x ... NaA, DISCUSSION. and other zirconium borides. Etching is violent with peroxides. ZrB Ibid. REF: CRB-OOOla PHYSICAL PROPERTIES NITRIDE, BN OF BORON Classification Nitride numbers Atomic 5&7 Atomic weight 24.8 (°C) Melting point 2730 (°C) Boiling point 2.25 Density (g/cm3) Application limit (°C) 650 heat °C) Specific (mean)(J/kg 25—1000°C 1570 thermal of expansion Coefficient linear 7.5 c-axis // ( x 10"6 cm/cm/°C) 25—800°C 900°C Thermal conductivity (W/m °C) 26 © 1991 by CRC Press LLC

201 188 CRC of Metal Etchants Handbook resistivity (ohms-cm 1013) 25°C 1.7 // c-axis Electrical x 1O10) (ohms-cm // c-axis 480°C x 2.3 =) index Refractive 1.54—1.68 (n 4—8 Dielectric =) (e constant Energy gap (eV) 3—10 band 3.615 Lattice constant (angstroms) scratch) Hardness + (Mohs — 8 — (hexagonal alpha (1010) prism structure Crystal normal) normal) beta (100) cube (isometric — White Color (solid) (110) (dodecahedral) Cleavage NITRIDE, BN BORON although as a General: compound, Does there are several boron- not occur natural containing B(OH)3, borax, NajB^. 10H2O, as examples. Boric acid, minerals: sassolite, occurs in hot springs associated with volcanic action. H3BO3, a nitride it is an industrial ceramic As a high melting point, used as a crucible with under atmosphere conditions (H2 or FG) for the processing of liquid metals, such reducing steels, aluminum aluminum alloys, tin, bismuth, and others. In an oxidizing atmos as and converts B2O3 BN above 650°C. phere to BN In Application: processing pressed powder Solid discs have been Technical State as a diffusion source of boron as used p-type dopant in silicon, with silicon wafers a sandwiched the discs (boric acid was the first such dopant, then diborane, B2H6 as between gas.) a nitride has been CVD grown as The thin films, also for boron doping drive- amorphous in, or for use as a dielectric, e.g., capacitor circuit element. Under pressure, with elevated temperature, amorphous have been converted to hexagonal or cubic single crystal films The latter fabricated as a high temperature functioning diode. BN has been structure. was passivation B2O3 films and applied as thin surface coatings. Also conversion converted to boron carbide, B4C by treatment with CC14 vapor at elevated temperature. to Limited HF, in HC1, Etching: H2SO4, H2O2, H3PO4. solubility NITRIDE ETCHANTS BORON BN-0002a NAME: acid TIME: Phosphoric ETCH TYPE: TEMP: RT to hot Acid, removal/cleaning COMPOSITION: ... cone. x H3PO4, DISCUSSION: as pressed powder blanks and parts. BN, used as a general cleaning and material Solution removal etch. REF: Bulletin C-941 eff 6/81(716/731/3221) — The Carborundum Company BN-0009: Rand, J & Roberts, J F — J Electrochem Soc, 115,423(1968) M as and thin film amorphous coating on silicon, gallium arsenide, BN, other semicon a gold Solution hot ductors. removal of BN through photolithographic patterned used for masks; also used SiO2 and Si3N4 as pattern masks. BN-0010: Kim, C et al — J Electrochem Soc, 131,1384(1984) CVD BN, film amorphous coating deposition by thin on (100), n-type silicon wafers, as then overcoat with Si3N4 to prevent out-diffusion of boron. Wafer heated to drive-in boron and as dopant. Remove silicon nitride with HF p-type remaining boron nitride with hot phosphoric acid. © 1991 by CRC Press LLC

202 189 BN-0002b NAME: Sulfuric TIME: To 1 h ETCH acid removal/cleaning TEMP: TYPE: Acid, RT mg/cm3 10.7 RATE: COMPOSITION: 20%H2SO4 x... DISCUSSION: pressed powder test blanks. Dilute solutions of H2SO4 will attack boron nitride; BN, as solution concentrated not. whereas will Ibid. REF: BN-0002c Nitric acid TIME: To 1 h NAME: ETCH removal TEMP: RT TYPE: Acid, COMPOSITION: RATE: 8.9 mg/cm3 ... HNO3, cone, (fuming) x DISCUSSION: BN, pressed powder test blanks. 'Turning" nitric acid will attack boron nitride. as "yellow" Standard "white" fuming 70%; then is 72%; and "red" {Note: concentration fuming. When fuming nitric is shown, it is usually red fuming.) 74% REF: Ibid. BN-0002d ETCH Hydrofluoric acid TIME: To 1 h NAME: Acid, removal TYPE: RT TEMP: COMPOSITION: RATE: 17 mg/cm3 x ... HF, cone. DISCUSSION: BN, as pressed powder test blanks. Solution will attack boron nitride. REF: Ibid. Ibid. BN-OOOlb: pressed powder discs for boron drive-in as sandwiched silicon wafers. Soak in BN, of rinse heavily in running DI water, and dry under IR HF, Use HF 5 min, RT, for lamp. cleaning BN. BN-OOOla ETCH Paper TIME: NAME: Abrasion, cleaning TEMP: TYPE: RT COMPOSITION: x ... filter paper DISCUSSION: BN, as pressed powder discs. Light hand lapping on Whattman #5 filter paper used to Results clean with N2 blow off. Discs used in a metal plating study. followed were surfaces, poor to metal failure to due to the powdered surface. adhere REF: Walker, P & Dokko, P — personal application, 1985 BN-0002e NAME: Sodium hydroxide TIME: To 1 h ETCH TYPE: Alkali, removal/cleaning TEMP: RT COMPOSITION: RATE: 8.9 mg/cm3 x ... 20% NaOH © 1991 by CRC Press LLC

203 190 CRC of Metal Etchants Handbook DISCUSSION: BN, powder test blanks. Lower concentrations used for cleaning; higher as pressed more rapid concentrations for removal. Ibid. REF: BN-0002f ETCH Lead oxide TIME: NAME: flux, removal TEMP: Molten TYPE: Molten COMPOSITION: x...PbO DISCUSSION: pressed powder test blanks. Molten flux metal oxides attack BN BN, conversion as with B2O3. to REF: Ibid. BN-0003 ETCH Hydrogen peroxide TIME: NAME: Acid, removal TEMP: RT to TYPE: hot COMPOSITION: x...H2O2 x ... H2O DISCUSSION: in thin films on silicon. Various BN, used amorphous etch patterning as concentrations through metal masks. film Hirayama, M & Shomo, J — / Electrochem Soc, REF: 122,1671(1975) BN-0004 NAME: Argon 5 h ETCH TIME: Gas, TEMP: 1000°C TYPE: crystallization COMPOSITION: ... Ar x DISCUSSION: BN, crystal films. Initially deposited single copper substrates as clear, amorphous on coatings. Heat treatment as shown above showed conversion to single crystal hexagonal BN. BN much below 600°C were unstable in moist atmospheres and devitrified; deposited during showed from the substrate delamination cooling after de thick films spontaneous Films deposited at low temperature also swelled and partly dissolved in water, and position. films toward thick white, opaque, rather than clear. tended Motojima, Thin et al — REF: Solid Films, 88,269(1982) S BN-0005: J et al — Thin Solid Films, 110,7(1983) Szmidt, BN, single crystal thin films grown by reactive pulse plasma on silicon, (111) and (110) orientated wafers, and n-type. Films were called Borazone and consisted mainly of beta- p- BN. BN-0006 NAME: TIME: ETCH Metal, Molten TEMP: TYPE: removal COMPOSITION: x Be, U, Ni, Pt ... DISCUSSION: crystals BN, cubic boron nitride. Single as with grown junctions fabricated under (100) 55 K atm pressure at 1700°C. For n-type, doped with Be; for p-type, doped with Si. Fabricated © 1991 by CRC Press LLC

204 191 as diode the BN appears capable of operating up to 53O°C and possibly 1300°C. Diamond a shows semiconducting but is more difficult to fabricate. (Note: Silicon also properties, has carbide, as a high temperature diode.) been Si3C, fabricated et Science, — C October 1987 REF: Mishima, al (Ed) — Sci News, 132,241(1987) Greenberg, BN-0007: J new development as a BN, reported as shown in BN-0006. (100) diode Merbarki, et al — J Cryst Growth, 61,636(1983) BN-0008: M platelets specimens as hexagonal single crystal (0001) were yellow to col BN, grown BN has a layer structure like graphite parallel to the orless. Growth was with boron c-axis. in silicon flux under nitrogen in an induction furnace at 1850°C. a PROPERTIES OF PHOSPHIDE, BP PHYSICAL BORON Phosphide Classification Atomic 5 & 15 numbers 41.79 Atomic weight (°C) 1300 Melting point Boiling point (°C) Density (g/cm3) resistivity (ohms-cm) 0.41 (100) Electrical 5.64(111) Carrier (n) (x 1017 cm3) 1.0 (100) 3.07 (111) concentration mobility (cm2/V/sec) 145 (100) 36.5 (111) Electron (u) constant (angstroms x 10"6) 4.539 Lattice 4.536 (111) (100) Hardness — scratch) 9 (Mohs + (Vicker's — kg/mm2) 3000-4000 Crystal structure (isometric — normal) (100) cube Color (solid) Red-orange (cubic) (001) Cleavage BP BORON PHOSPHIDE, not occur as a natural compound, though there are many boron minerals General: Does group, arsenates, and sulfates. The borate carbonates, as hydrous salts, such phosphates, as borax, has major industrial use. BP is not normally as in metal processing, although used it be a phosphorus additive in irons and steels, brass, bronze, etc. can Application: a phosphide is Technical III—V compound semiconductor with the Boron individual common of such compounds. The polarity elements are silicon dopants: (111) boron, p-type; phosphorus, n-type. They have been occasionally used for dual-doping, but this is recommended as there can be drastic alteration of the material resistivity with not heat processing. subsequent (CZ) material been grown by the The has method; and in a molten flux, Czochralski both methods as single crystals. It also has been deposited as an oriented thin film. It does evaluation not elevated temperature, and is under at as a high temperature diode, oxidize similar to silicon carbide and boron nitride. As a thin film it has been fabricated as a photovoltaic device. Etching: Alkali electrolytic solutions. Molten flux salts. © 1991 by CRC Press LLC

205 192 CRC of Metal Etchants Handbook PHOSPHIDE ETCHANTS BORON BP-0001 NAME: TIME: ETCH preferential Molten TYPE: TEMP: Molten flux, COMPOSITION: 3 ... NaOH NaA ... 1 DISCUSSION: and (111) grown as single crystal platelets by a flux method using Cu3P or BP, (100) the Ni12P5O at high temperature and under high pressure. Remove crystals from flux as flux deep etching of HF:HNO3. The (111) crystals are mixtures red in color; (100) crystals, by in The molten flux etch shown was used to orange/red. dislocations and other structure. develop The surface is wavy, representative of slight misorientation. Growth temperature was (111) with pressure 18 atm under argon. 1300°C of Y Kumashiro, al — J Cryst Growth, 70,515(1984) REF: et Kumashiro, Y et al — J Cryst Growth, 70,507(1984) BP-0002: (100) and (111) single crystal thin films grown by CVD on silicon substrates of BP, from like BP crystal plates were removed The the silicon by etching away the orientation. silicon in HF:HNO3. A form of float-off for film study under TEM. BP-0003 ETCH Sodium hydroxide TIME: NAME: Electrolytic, removal TYPE: TEMP: BP COMPOSITION: ANODE: NaOH CATHODE: ... 10% x POWER: A/cm2 0.1—10 DISCUSSION: crystal BP, Solution used in a dark room under red light for general single wafers. and polishing — higher removal may show some preferential attack. P-type concentrations etches than 100 x faster than n-type. more 123,259(1976) Chu, & Chu, S S REF: J Electrochem Soc, T L — PHYSICAL PROPERTIES OF BORON TELLURIDE, B2Te3 Classification Telluride Atomic numbers 5 & 52 Atomic weight 404.47 point (°C) Melting ~1800 (°C) point Boiling Density (g/cm3) (Mohs — scratch) 7—8 Hardness structure Crystal — normal) (100) cube (isometric Color (solid) Grey/black Cleavage (cubic) (001) BORON TELLURIDE, B2Te3 General: Does not occur as a natural metallic telluride, although there are several other minerals natural selenide minerals. Most boron and are silicates or phosphides, and telluride there is the natural occurrence of boric acid, B(OH)3, as the single crystal sassolite or © 1991 by CRC Press LLC

206 193 extracted the water of hot springs. The telluride has little use in the metals industry from than as possible compound semiconductor. other a Boron Technical a III—IV compound semiconductor and has telluride Application: is selenides, studied, as an isomorphous series with widely and as telluride- quite been alone, crystals. There is no major application as selenide-sulfide State devices at the mixed Solid time, it may be used as a thin film material in heterostructural although present devices. Mixed of HF:HNO3:HAc/H2O; dichromates alone, acids as acid mixtures. Etching: or TELLURIDE ETCHANTS BORON BTF-0001 ETCH Potassium chromate TIME: 10 min NAME: Acid, preferential 95°C TYPE: TEMP: COMPOSITION: K2Cr2O7 X...0.5M DISCUSSION: wafers used in a dislocation study. Solution B2Te3, develop dislocations on (111) will (111)A — boron surface only. the Harper, C A — Handbook of Materials and Processes for Electronics, REF: McGraw-Hill, New 1970, 7 York, Gatos, 1963 C & Lavine, M C — Lincoln Lab Tech Rep, 293, January BTE-0002: H single crystal material used in a general development study. B2Te3, PROPERTIES OF BORON TRIFLUORIDE, BF3 PHYSICAL Classification Fluoride Atomic numbers 5 & 9 Atomic weight 67.82 point (°C) 127 Melting - (°C) Boiling - point 101 2.99 liquid (g/cm3) Density Hardness — scratch) 1.5—2 (Mohs (isometric — Crystal (100) cube structure normal) (solid) Color Colorless Colorless (gas) Cleavage (cubic) (001) BORON TRIFLUORIDE, BF3 Does not General: as a natural compound, although there are other metallic occur fluorides, as fluorite, CaF2, and cryolite, Na2AlF6, both of which have important optical such Note and as fluxes in metal processing. use that cryolite has a refractive index properties (n = 1.33 X) that is the closest of any mineral to that of water (n = 1.00), such that it "disappears" when into water. The trifluoride is not used in the metal industries introduced flux as but, compound, could be used as a a in soldering similar to fluorite appli fluoride cations. Technical Application: Boron trifluoride is under study and development in Solid State orientation. processing thin film with single crystal a It has possible optical characteristics as and applications, and is under evaluation for defect structure. Etching: H2SO4: mixed acids of HF:HNO3. © 1991 by CRC Press LLC

207 194 CRC of Metal Etchants Handbook TRIFLUORIDE ETCHANTS BORON BTF-0001 NAME: TIME: ETCH TEMP: preferential Acid, TYPE: COMPOSITION: 1 ...HF ... 3 HNO3 DISCUSSION: thin films grown by CVD. Solution used to BF3, defects in a (100) oriented develop structure study. J — J Electron Caine, 13,341(1984) REF: E Mater, 70Cu:30Zn BRASS: not occur as a natural alloy, although there General: some carbonates and Does are The rosasite, (Cu,Zn)CO3.(Cu,Zn)OH3, and barthite, 3ZnO.CuO.3As2O5. arsenates. minerals representative such hydrates. are of H2O of ancient origin, circa 4500 B.C., as some possible artifacts of brass Brass is have found Egyptian tombs of the Pharaoh dynastic in but they are rare and were been period, by the discovery of bronze, circa 5000 B.C. There pre-dated still individual bronzes and are brasses but far more trinary mixtures of Cu:Zn:Sn (Bronze, Cu:Sn) which are more today, called brass. are other brass mixtures containing Pb, Al, Ni, Mn, P, and commonly There it addition tin, in Brass is more widely used as to is not as brittle as bronze, and is Fe, Sn. easily fabricated. A few of the better known brasses are shown more below: Formula Name Red brass 85Cu:15Zn or brass 67-72Cu:28-32Zn:xPb:xFe spring Cartridge brass 67Cu:33Zn Yellow (ordinary) Wire brass 61Cu:39Zn addition to the above, there are some In named brasses, such as muntz well-known metal, and German silver. All brasses, as pewter, as several other metal alloys, are well heat treated for a specific hardness, such as V4- or V2-hard, as against the dead-soft heat treatment of or gold wire used in Solid State device bonding. Brass is a fair aluminum conductor and excellent thermal transfer characteristics, such that it is used as electrical has also sink mounting devices in electrical testing. It heat is quite resistant to atmospheric a for and can be used outside under variable weather conditions. Brasses are available corrosion, a rod, range of forms — in tube, sheet, wire, thin shim stock, bulk material for shaping wide cutting plastics and finely powdered brass is added to or and paint as a coloring pigment. — cartridge can drawn or extruded into shaping, such as for It casings, which is not the be case of bronze. Technical Application: Brass is not used in the direct fabrication of Solid State devices, but it used in package designs, as general heat sinks, or device test blocks. Where critical is such microelectronic high frequency devices, gallium arsenide FETs are being tested as problem elevated conditions, there can be a under of out-diffusion of zinc from temperature the brass into the device under test. This can alter or destroy device characteristics. To surfaces prevent occurring, copper plate the brass from to a sufficient thickness, such this that the copper will act as a blocking layer against zinc diffusion, vs. the temperature level being used. There are many uses of brass parts in material processing. Shim stock has been used as © 1991 by CRC Press LLC

208 195 a mask for applying ink to a semiconductor wafer that is then etch-patterned, or the pattern shim used a metal evaporation mask. Rods are used as either holders for probes patterned as in or probes themselves. Brass platens have been the use for many years for testing, as in — rocks and minerals — as well as lapping other compounds. An abrasive materials many is directly to the platen surface, or a added pad is glued to the surface, then slurry felt-type pad saturated with an etch solution; or an abrasive slurry is drip-fed the the pad with onto the rotated. Examples are the Buehler, Speed-Fam, or Strausbaugh lapping/polishing platen machines. Alpha-brass grown as single crystals for morphological studies. has been mixed H2SO4, HNO3, aqua regia, and other HC1, acids. Etching: H3PO4, ETCHANTS BRASS BRA-OOOla NAME: TIME: ETCH Acid, RT TEMP: TYPE: removal COMPOSITION: (1) ... HNO3 (2) (6) ... KC1 16 ... H2O 100 ... H2O 160 DISCUSSION: Brass, or eyelet. A general two-step cartridge, for cleaning brass. Etch with the etch dilute nitric acid solution, water rinse; then follow with the salt solution, and water rinse. REF: Oberg, & Jones, F D — Machinery Handbook, 4th ed, The Industrial Press, New E 1968 York, P & Campos, R — personal application, 1961 BR-0002a: Walker, as on trailers. Used the (2) solution piping 6 g KCl:100 ml H2O Brass/bronze cryogenic light cleaning of parts. for BRA-0008a ETCH Scale dip or fire-off dip TIME: NAME: Acid, TEMP: RT TYPE: removal COMPOSITION: 1 ... HNO3 ... H2O 1 DISCUSSION: the Brass parts. As a "scale" dip, specimens solution is used to remove oxide prior and to a brite dip. As a "fire-off" dip, solution is used as a general removal etch for brass, bronze, copper, copper alloys. and Bulletin — The American Brass Co. REF: #B-11D Maddin, R & Asher, WR-^v Sci Instr, BRA-0004: 21,881(1957) Brass A Saran plastic thread wetted specimens. the solution mixture was used as with an acid-saw to cut specimens. BRA-0005: McGuire, — Yale University, Ph.D. dissertation (1949) T R specimen. Acid-saw cutting method reference from BR-0004. Brass, BRA-OOOlb ETCH TIME: NAME: TYPE: Acid, removal TEMP: RT COMPOSITION: 4 ... HC1 1 ... HNO3 © 1991 by CRC Press LLC

209 196 CRC of Metal Etchants Handbook DISCUSSION: Brass cartridge or eyelet. A general etch for both brass and bronze. {Note: specimens, as very to aqua regia.) is Solution close REF: Ibid. Ibid. BRA-0002: were cryogenic Brass piping and parts and etch cleaned in this solution. bronze trailer BRA-0002c NAME: Sulfuric acid, dilute TIME: ETCH Acid, TYPE: TEMP: removal COMPOSITION: 1 H2SO4 ... 10 ... H2O DISCUSSION: and bronze cryogenic trailer piping and parts. Solution used for corrosion removal. Brass REF: Ibid. BRA-0008b ETCH Bichromate finish dip TIME: NAME: Acid, finish TYPE: TEMP: COMPOSITION: 12 oz ... H2SO4 4oz ... NaCr2O3 1 gal ... H2O DISCUSSION: Brass, and copper parts. Solution used to remove scale (oxide). Produces a bronze, finish. semi-matte Ibid. REF: BRA-0008C NAME: Matte dip TIME: ETCH Acid, TEMP: TYPE: finish COMPOSITION: 2...H2SO4 ... 1 HNO3 ... *ZnOorZnS x *x saturate the solution = DISCUSSION: Brass, bronze, and copper alloys. Solution will produce a matte finish on parts. REF: Ibid. BRA-0006 ETCH TIME: NAME: TYPE: Acid, removal TEMP: COMPOSITION: ... NH4OH x x ... H2O2 DISCUSSION: Brass specimens and parts. Used as a general etch for brass. Solution reaction reduced with the addition of water as a cleaning etch. © 1991 by CRC Press LLC

210 197 REF: T & Deardon, W H — Metallographer's Handbook of Etching, Pitman & Bergland, London, 1931 Sons, BRA-0013a NAME: TIME: Phosphoric ETCH acid TEMP: preferential Hot TYPE: Acid, COMPOSITION: x ... H3PO4 H2O ... x DISCUSSION: used in a study CuZn(30%) striations and slip. Use very dilute solutions specimens of defect Solution cannot be used electrolytically development. it will polish specimens. for as (NH4)2SO4:NH3 solution did not work. Mechanical hand polishing used to reduce damage A and depth, did not show below a damage depth of about V4 mm. slip McLeon, — J Inst Met, 95(1947—1948) REF: D Boswell, F W C & Weinberg, F — J Appl Phys, 31,1835(1960) BRA-0019: specimens. were blanks Alpha-brass lapped down and etch thinned for di Specimen movie observation dislocation movement. A 16 mm rection camera with a 2" focal length, of 1.6F lens was used to record the results. (Note: A similar movie was made while etching silicon wafers 1957.) in BRA-0013b ETCH NAME: TIME: preferential Acid, TEMP: TYPE: COMPOSITION: 2NH4Cl.CuCl2.H2O x ... KOH (NaOH) ... x DISCUSSION: specimens. Solution will develop striations and slip. See BRA-0013a for CuZn(30%) further discussion. Ibid. REF: BRA-0014 Jacquet's etch TIME: ETCH NAME: Electrolytic, polish TEMP: TYPE: ANODE: COMPOSITION: Brass 345 ... HC1O4 CATHODE: ml 655 ... HAc POWER: ml DISCUSSION: Brass specimens. Solution used as a general electrolytic etch. REF: Barrett, & Levenson, L H — Trans Am Inst Min Met (England), 137,112(1940) C BRA-0015 ETCH Sodium chloride TIME: NAME: preferential TEMP: Electrolytic, TYPE: COMPOSITION: ANODE: Brass x ... 5% NaCl CATHODE: POWER: DISCUSSION: Brass specimens. Solution used to develop etch figures. REF: Fesch, C H & Whyte, S — J Inst Met, 904,10(1913) © 1991 by CRC Press LLC

211 198 CRC of Metal Etchants Handbook BRA-0007 ETCH chloride TIME: NAME: Ferric removal TYPE: to hot TEMP: Acid, RT COMPOSITION: 30—35°B6 ... x FeCl3 x ... H2O DISCUSSION: and copper alloy parts. Solution used as Brass, general etch for metals to bronze, a irons, and nickel, and may be for steel, cleaning only, polishing, or pref include surface (Note: Ferric chloride solutions are mixed as erential. percent as shown; or by Normal; Baume, The latter is a measure of solution viscosity. A common mixture is as 35°B£.) °B6. N/A REF: BR-0008d ETCH NAME: Bright dip TIME: Acid, removal TEMP: RT TYPE: COMPOSITION: 2 ...H2SO4 gal gal ... HNO3 1 V2floz...HCl 1—2qt...H2O DISCUSSION: bronze, and copper alloys. Surfaces Brass, usually oxide stripped with a scale are dip or pickling solution, such as the solution shown, prior to a brite dip. REF: Ibid. BRA-0008d ETCH solution TIME: NAME: Pickling clean RT Acid, to hot TEMP: TYPE: COMPOSITION: 12—15%H2SO4 x... DISCUSSION: bronze, and copper alloys. Solution used to soak and remove oxide and Brass, scale prior further treatment of material. to Ibid. REF: BRA-0009 ETCH NAME: Phosphoric acid TIME: Electrolytic, polish TEMP: TYPE: ANODE: Brass COMPOSITION: x ... 35% H3PO4 CATHODE: POWER: DISCUSSION: Brass, as single crystal alpha-brass. Wafers were cut and polished in the solution shown. Specimens were in a study of slip modes. used 4,271(1956) Wilsdorf, & Fourier, REF: J — Acta Metall H J BR-0010: Wilsdorf, H — Z Metallkd, 45,14(1954) BRA-0012: Fourie, J T — Acta Metall, 8,88(1960) slip Alpha-brass single crystal specimens used in a study of as during plastic deformation. Power used was 2.67 V. © 1991 by CRC Press LLC

212 199 BRA-0016 NAME: TIME: ETCH preferential Pressure, TEMP: TYPE: COMPOSITION: deformation ... x DISCUSSION: deformed in a study Alpha-brass secondary slip. Also studied copper single crystals of slip nucleates at the end of primary slip crystals. when internal stress fields Secondary lines high. are Phil T Thornton, PR — & Mag, 10,314(1964) REF: Michell, E BRA-0017 TIME: 120 min ETCH NAME: TYPE: Acid, cutting TEMP: RT COMPOSITION: 200 ml (1) HC1 (2) 1 ... HNO3 ... g ... 1 ... H2O 50 FeCl3 ... H2O 250 ml DISCUSSION: specimens 3/16" thick are soaked in solution (1) used to cut brass, aluminum, and Brass growth copper. used to cut tin and zinc. (Note: An excellent review of metal (2) Solution methods.) Honeycombe, Rev, 4,1(1959) REF: RWK-Me/ BRA-0018 NAME: Nitric acid TIME: ETCH TYPE: Acid, cleaning TEMP: RT COMPOSITION: 1 45%HNO3 ... ... H2O 1 DISCUSSION: mm 29.38% Cu)]. Cut as [(Cu:Zn) with square blanks and plated with Alpha-brass 12 containing radioactive tracer ^Cu64 used in a study of the mechanisms of Cu2O copper Brass formation. cleaned: (1) degrease with TCE; (2) clean in solution shown; and (3) was 15 dry. plating, blanks were water soaked for air h to oxide tarnish surfaces. See After CUO-0016. REF: Birley, S S & Tromans, D — J Electrochem Soc, 118,636(1971) PHYSICAL PROPERTIES BROMINE, Br2 OF Halogen Classification number 35 Atomic Atomic weight 159.83 point (°C) - Melting (- 7.2) 7.3 Boiling point (°C) 58.78 Density (g/cm3) 20°C 3.12 (g/cm3) 59°C 2.93 Thermal (x 10~4 cal/cm2/cm/°C/sec) 0°C 0.091 conductivity Latent heat of fusion (cal/g) 16.2 Specific (cal/g/°C) 0.107 heat Solubility (100 ml H2O) 50°C 52 ml © 1991 by CRC Press LLC

213 200 CRC of Metal Etchants Handbook ionization potential 11.84 1st (eV) (angstroms) Ionic 1.96 radius (Br+1) 6.7 section Cross (barns) pressure (°C) Vapor 9.3 Crystal (orthorhombic—normal) structure (100) a-pinacoid red-brown Dark Color (liquid/solid) solid) (001) Cleavage (basal — BROMINE, Br mercury are the only two elements and are liquid at standard General: Bromine that pressure (22.2CC and 76 mmHg). Mercury is found as a temperature native element and solid, nature, bromine is not, being primarily extracted from sea water and from the soil of in but in It form of an alkaline halide. plains is a dark red-brown liquid with an offensive alluvial the elements: a of the halogen group of member fluorine and chlorine are gases; odor and is a liquid; and iodine, a solid. It is more reactive than iodine bromine less reactive than but either or fluorine, with fluorine being the most reactive element known. All of the chlorine form diatomic as F2, Cl2, Br2, and I2, even though they are occasionally halogens molecules the e.g., as monatomic, in Br, Cl, etc. shown literature dibromide, important most bromine is as ethylene use C2H4Br2, which is added The of leaded ethyl gasoline to remove by-products of tetraethyl lead. It also is used to medicinal for purposes, or NaBr as sedatives; in silver emulsions (AgBr) for photography; and in the KBr of ingested gas" as bromine-acetone. It is poisonous if manufacture and can produce "tear can on skin sores are difficult to heal. The vapors the be a severe irritant to eyes, which nose, and throat. As a low percentage mixture in methyl alcohol (up to 3%), it is a major polish and removal etch many metals and metallic compounds, and can be a preferential etchant for 3%, used about 20% in MeOH. These Br2:MeOH mixtures have acquired the above to The polish bromine concentration that alters from BRM. to preferential can acronym exact it some by method of application, such that to is not accurately defined. BRM vary degree are often used on semiconductor wafer surfaces after cutting and prior to final etchants cleaning as chemical/mechanical (chem/mech) lapping solution to remove residual sub a with damage cutting and mechanical lap/polish after abrasives. The so surface remaining also are used for general removal, as a jet for thinning, lutions In all cases, when used etc. as etch solution, bromine can be replaced an iodine with similar results and, as bromine, by is so volatile, iodine is often preferred when solutions are to be used above room temperature. Bromine has mixed with other alcohols or solvents, and shows similar results as with been solutions. BRM is used as an additive to other etch solutions, such as Camp #4, now known It CP4. as The CP4 contained 0.6 ml Br2 and, original used without bromine, is called CP4A. when There are several CP4 modifications where the Br2 has been replaced by I2, Cu(NO2)3, AgNO3, etc. as Application: used in etching solutions is described in the preceding Technical Bromine General It has been solidified and studied by freezing. section. Etching: Soluble in MeOH. The following is a selected list of BRM solutions as applied to several semiconductor under materials, and other compounds. Additional solutions are shown metals the individual elements/compounds in this Etchant Section: © 1991 by CRC Press LLC

214 201 Use Material Formula Ref. GaAs Polish AlAs, AS-0001 Br2:MeOH 0.5% Preferential 10mlPEtch:10mlBr2"PBr CdTe CDTE-0006a Etch"(P: 10mlHC!:10ml HNO3:5 ml H2O) Polish GaAs GAS-0006 0.05% Br2:Me0H GaAs Polish 1% Br2:MeOH GAS-0003a GaAs GAS-0004b Polish/thinning 1.5%Br2:Me0H GaAs Selective 5% Br2:MeOH GAS-0009 GaAs Preferential 1% Br2:EOH GAS-0013 GaAs removal Oxide Br2:MeOH 2% GAS-0132 Polish GaP Br2:MeOH 20% GAP-0007 Preferential cone. Br2, GaP GAP-0010 GGG Preferential GGG-OOOlb HBr, cone. Gs, Si Preferential Br2 250 ml 30% KOH:25 ml GE-0012b 30HF:50HNO3:30HAc:0.6Br2 Ge, Si, Polish/preferential GE-0065c InSb InAs, "CP4" CdlnTe Polish/clean 1% Br2:MeOH CIT-0001 CdP2 Selective 1% Br2:MeOH CDP-0001 CdSe 4% (0001) Br2:MeOH Polish CDSE-0002 CdSe Clean 1% Br2:MeOH:xlMHCl CDSE-0004 Br2:MeOH 10% Polish CdTe CDTE-0010 2% Br2:MeOH CdTe Polish/removal CDTE-0009 CdTe 2% Br2:Glycol (Te) removal Smut CDTE-0011 Cu Dislocation M FeCl3:l 1.25 1 12MHC1:1 M 1 CU-0015 HBr CuInSe2 6K2SO4:1H2O2:1H2O then 1% Polish/clean CUIS-0003 Br2:MeOH Br2:MeOH (100) Polish GaSb 2% GASB-0004c lBr2:10MeOH GaSb Preferential GASB-0008a InAs 5—10% Br2:MeOH Dislocation INAS-0005 InP 0.5% (100) Br2:MeOH Step-etch INP-0007 HBr (48%) InP 9 N Preferential INP-0026 5HF:lBr2 InP Preferential INP-0017b InP 2H3P04lBr2 Preferential INP-0038 InP 2H2SO4:lHBr(47%) Dislocation INP-0051 Fe xBr2:MeOH Oxide removal FE-0100 SnO2 lHBr:lH2O + Cr, pes Removal film) (thin SNO-0002 W CBrF2, ionized plasma RF W-0011 ZnSe xBr2:MeOH Polish/removal ZNSE-0001 ZnSe xBr2:CS2 Polish/removal ZNSE-0001 BROMINE ETCHANTS BR-0001 ETCH NAME: Methyl alcohol TIME: TYPE: preferential Alcohol, TEMP: RT to 0°C COMPOSITION: CH3OH(MeOH) ... x DISCUSSION: the liquid to 0°C with liquid nitrogen, LN2. A Br2, specimens solidified by freezing © 1991 by CRC Press LLC

215 202 CRC of Metal Etchants Handbook of MeOH the surface was used to develop etch figures and crystalline structure of drop on mass. the a general etching study of bromine vs. iodine as applied on Used solidified in A and of solid bromine was placed on wafer surfaces wafers. allowed (111) silicon piece to similar A iodine was used with just sufficient heating piece liquefy, and to liquefy. of were compared. artifacts surface P & Waters, W P — personal application, 1957 REF: Walker, BRONZE, Cu:Sn does not occur in nature as a specific single crystal, although native General: Bronze antimony, contains of iron, silver, bismuth, lead, amounts and tin. It often small copper the natural occurrence of a copper-tin was that led to the discovery and probably alloy of as pure copper was bronze mined throughout southern Europe development extensively the Near East in ancient times, e.g., 5000 B.C. or earlier. Pure copper is soft and and and the two copper carbonate minerals, which are usually associated with copper malleable deposits, are recognized by their brilliant colors: azurite (deep blue) and malachite vein easily temperatures both reduced to pure copper at easily between 200 to 250°C. green); are (bright minerals also have been in use as semi-precious gem stones Those ancient times two since are used in jewelry. and still of use gold and the pre-dates the use of bronze, it was the development Although copper that led to the "Bronze of bronze and the beginning of man's metal culture. Pure Age" copper too soft, but bronze can be cast, shaped, and honed to a fine cutting edge far is to sliver of flint or bone, as the latter fracture, chip, and superior easily. Although that weathering is in comparison to bronze and steels, it is highly resistant to brittle and irons corrosion. artifacts have been discovered Bronze archaeological digs, pre-dating the in Christian era, and are still usable as weapons or tools with little wear or alteration. Today there many types of bronze with specific names, such as aluminum-bronze; are sea water phosphor-bronze; bearing bronze, and others. With the devel manganin; bronze; the brass, is not brittle like bronze, and which addition of other metal of Cu:Zn, opment the two mixtures, the terms elements and bronze have become synonymous in many in brass as are mixtures of Cu:Zn:Sn they other metal constituents. instances plus still has many industrial uses, such as the sea Bronze bronze for its resistance to water salt and phosphor-bronze which, when used as thin sheet, has excellent spring char water and Because high copper content, both bronze die brass are excellent electrical acteristics. of heat conductors — copper telephone wires are and alloy rather than pure copper, and an bronze/brass are used in working with tools materials as they are nonmagnetic and magnetic unaffected by the magnetic flux. Cryogenic liquid piping and fittings are made of bronze as the structure is tough, and unaffected by continual severe changes in temperature, material up as down to - 196°C (LN2), and back RT to 100°C on a hot day. such from Application: Bronze is not used in direct Solid State material Technical fabrication, although spring clips are widely used to hold semiconductor wafers in phosphor-bronze holders position in vacuum systems, or as metallization in device test fixtures. Bronze/ during brass parts also are used as heating or cooling blanks; as abrasive lapping platens; as electrical contacts; probes; electronic assembly packaging material; as electrical pin an inking and as evaporation masks; and electrical test blocks. There is reference to brass having been grown and studied as a single crystal, but we has have similar reference for bronze, although it is probable that it no been so grown and studied. Etching: HNO3, H2SO4, and acid mixtures. © 1991 by CRC Press LLC

216 203 BRONZE ETCHANTS BRO-0001 ETCH NAME: TIME: removal TYPE: TEMP: Acid, COMPOSITION: HC1 ... 5 ... HNO3 100 DISCUSSION: specimens. Solution Cu:Sn(30%), a general etch for bronze. (Note: standard bronze is a dilute form of aqua regia This can be used on both bronzes and brasses.) is and Oberg, & Jones, F D — Machinery Handbook, 4th E The Industrial Press, New REF: ed, 1951 York, BRO-0002a NAME: TIME: ETCH Variable TYPE: cleaning TEMP: RT Acid, COMPOSITION: 5 ... HC1 HNO3 ... 100 ... H2O 150 DISCUSSION: brass cryogenic trailer Bronze Solution used as a general surface cleaner and piping. removal of dirt and grease for these parts. After etching, heavy water wash and pat from dry toweling. Where severe corrosion was present, parts were with scrubbed in lightly solution with a stainless steel brush. REF: Campos, R & Walker, P — AF Contract to Clean Cryogenic Trailers, 1961 BRO-0002b ETCH Sulfuric acid TIME: 1—10 min NAME: Acid, cleaning RT TYPE: TEMP: COMPOSITION: ... 1 H2SO4 10 ... H2O DISCUSSION: and brass cryogenic trailer piping and parts. Solution used as a corrosion removal Bronze etch to light scrubbing with a stainless steel brush. Water wash after etching and include dry pat toweling. with Ibid. REF: BRO-0003 ~~~ ETCH NAME: Ferric chloride TIME: TYPE: Salt, macroetch TEMP: COMPOSITION: x...5%FeCl3 ... x H2O DISCUSSION: artifact. Solution used as Bronze macro-etch on bronze arrowheads found at the biblical a Migdol Fort, dated in the 6th century A.D. The etch developed a dendritic cast structure. used (Note: of ferric chloride are concentrations in structure development etching Various of both bronzes and brasses.) Sci REF: J et al — Peiles, Am, 244,61 (August 1976) © 1991 by CRC Press LLC

217 204 CRC of Metal Etchants Handbook BRO-0004a ETCH NAME: TIME: macroetch TYPE: TEMP: Electrolytic, COMPOSITION: ANODE: g CrO3 CATHODE: ... 1 90 POWER: 1.5—2 VDC ml ... H2O DISCUSSION: aluminum bronze. 88—96Cu:2.3—10.5Al:xFe:xSn, used to develop struc as Solution in material. ture this Met Dig, AIB (22),23(1983) — Buehler Ltd REF: 21 BRO-0005 NAME: TIME: ETCH 30, or 90 min 15, TYPE: anisotropic TEMP: RT Salt, COMPOSITION: x *FeCl3 ... *1.4g/cm3 DISCUSSION: as magnesium bronze. Solution was used in a centrifuge to produce a Bronze:Mg, positive ( ) and negative (-) gravity during the + period. Used to form pits and via-holes etching in both bronze and gallium arsenide specimen sheets or wafers. REF: Kuiken, K & Tilburg, R P — J Electrochem Soc, 130,1722(1983) N BRO-0004b ETCH TIME: NAME: TYPE: Acid, microstructure TEMP: COMPOSITION: ... NH4OH x ... x H2O2 DISCUSSION: specimens. Solution used to develop Bronze Also used on copper. microstructure. REF: Ibid. BRO-0004c ETCH NAME: Chromic acid TIME: TYPE: Electrolytic, TEMP: preferential ANODE: Bronze COMPOSITION: 1%CiO3 CATHODE: x... POWER: DISCUSSION: Red brass specimens. Solution used to develop structure in a cast alloy that was furnace cooled. Ibid. REF: BRO-0004d ETCH NAME: Chromic acid TIME: Swab TYPE: Acid, preferential TEMP: RT COMPOSITION: lg ...CrO3 99ml...H2O © 1991 by CRC Press LLC

218 205 DISCUSSION: as as (See BRO-0004a). Solution used bronze a wet chemical etch Bronze, aluminum rather than electrolytic. (WCE) with a swab wetted in solution to specimen surfaces Apply to develop structure. REF: Ibid. BRO-0004e ETCH NAME: ALN3-1 TIME: Dip TYPE: Acid, macroetch TEMP: RT micro-, COMPOSITION: 5 ... HNO3 ml ml 5 H2SO4 ... 4g ... CrO3 1 g ... NH4C1 90 ... H2O ml DISCUSSION: Red brass specimens. Solution used to develop microstructure. REF: Ibid. © 1991 by CRC Press LLC

219 206 CRC of Metal Etchants Handbook PROPERTIES Cd PHYSICAL OF CADMIUM, Classification metal Transition number Atomic 48 Atomic weight 112.4 point Melting (°C) 320.9 Boiling point (°C) 765 (g/cm3) Density 8.65 (cal/sec)(cm2)(°C/cm) conductance 20°C Thermal 0.22 heat 20°C (cal/g) Specific 0.055 vaporization Latent (cal/g) of heat 286.4 Atomic volume (W/D) 13.1 energy ionization (K-cal/g-mole) 1st 207 (eV) potential ionization 1st 8.99 (Pauling's) Electronegativity 1.7 radius Covalent (angstroms) 1.48 Ionic radius (angstroms) (Cd+2) 0.97 coefficient Linear expansion of thermal 29.8 (xl0-6cm/cm/°C)20°C Electrical resistivity (micro-ohms-cm) 20°C 6.83 (eV) Electron work function 4.07 °C) pressure (mmHg in Vapor 611 (barns) Cross section 2450 — scratch) Hardness (Mohs 2 Crystal structure (hexagonal — normal) alpha prism, hep (1010) normal) — (isometric beta (100) cube Color (solid) White-silver (basal/cubic) Cleavage (0001)/(001) CADMIUM, Cd not occur as a General: element. There are three cadmium minerals of which Does native greenockite, CdS, is of importance as an ore, though cadmium occurs only a trace as constituent several minerals. Greenockite does occur as single crystals, but is most common in ZnS. a associated with zinc deposits, e.g., sphalerite, coating It is a by-product of as drusy ore refining, volatilizing first and collected as zinc brown oxide. As the pure metal it the is white, very soft, with a relatively bluish-silver melting point and, like silver, tarnishes low in air (presence of sulfur). When heated in air, it burns to the oxide. It has uses similar to those of zinc and, as a surface plating, is more corrosion industrial than zinc salt (NaCl) spray, though it is slowly attacked by salts in a natural sea to resistant is and cadmium compounds are toxic. It several widely used in the environment, water of bolts and screws as, due in part to its plating it has excellent low friction binding softness, ability. a constituent in many low melting point alloys, and used as a bearing alloy for It is It low of friction and resistance to fatigue. coefficient is in the standard cells used for its EMF measurement, in vehicle batteries with zinc, and as the "cadmium battery" for elec tronics, such transistor radios and hearing aids. As the sulfide, CdS, it is a bright yellow as for glass, enamel, and paint. pigment a Application: In State Technical it is Solid p-type dopant in several com processing, pound semiconductors. Like indium, it is used alone or as a constituent in low melting not solders for assemblies, though it is package recommended for space hardware. device As the pure metal pre-form, rings or flats, it is used as a metal crush-seal in vacuum equipment, as in cryo-pumps. such It is a metal element in a number of binary and trinary compound semiconductors such © 1991 by CRC Press LLC

220 207 as sulfide, CdS, cadmium selenide, CdSe, and cadmium telluride, CdTe, as well cadmium ZnCdS, CdHgTe, trinary materials. It also has been grown and studied as a single as and general defects, and superconductivity. for crystal morphology, HNO3, mixed acids, and halogens. Etching: HC1, ETCHANTS CADMIUM CD-OOOla TIME: NAME: ETCH polish Acid, TEMP: TYPE: COMPOSITION: HNO3 1 ... 2...CH3COOH(HAc) ... H2O2 2 DISCUSSION: (111) and (100) single crystal wafers used in a morphological study. Wafers were Cd, polished solution the etch shown. in New Gilman, Johnston, W S — Dislocations in Crystals, John Wiley & Sons, & REF: J J 1956 York, V J CD-0015a: Met Abstr 8,94(1958) DeCarlo, — specimens. Development work on polishing Cd cadmium and zinc. of both pure CD-0015b: V J & Gilman, J J — Trans Am Inst Min Met Eng, DeCarlo, 206,511(1956) Cd Similar work to that of specimens. CD-0015a. CD-0002 ETCH NAME: Neon TIME: TYPE: Ionized gas, preferential TEMP: COMPOSITION: GAS FLOW: ... Ne+ PRESSURE: x ions POWER: DISCUSSION: Cd, specimens. Neon ion bombardment used to develop structure and crystal single Mg, figures. studied were Al, Bi, Co, metals Cu, Sn, and Zn. orientation Other Yurasova, REF: E — Kristallografiya, 2,1770(1957) V CD-0003a NAME: TIME: sec, then ETCH 5—10 polish 30—60 sec TYPE: Acid, TEMP: 20°C COMPOSITION: RT (1) ml ... HNO3, fuming 75 10 ml ... HNO3, fuming (2) 25 ml ... H2O 70 ml ... HAc DISCUSSION: Cd, Use etch (1) to polish and follow with (2) as specimens. wash; rinse in DI water a and blow dry with nitrogen. REF: Tegart, W J McG — The Electrolytic & Chemical Etching of Metals, Pergamon Press, London, 1956 CD-0007: McAfee, J — Aust Eng Yearbook, (1944) Cd specimens. Solution used to polish cadmium. Author refers to using a dip etching technique. © 1991 by CRC Press LLC

221 208 CRC of Metal Etchants Handbook CD-0004 ETCH TIME: NAME: Silicone forming TYPE: TEMP: Plastic, 120°C COMPOSITION: silicone ... x DISCUSSION: 44 to 1200 |xm diameter Cd by whipping the molten metal in a spheres from formed oil bath. A study of size warm of material on superconductivity. silicone effects Hein, A & Steel, M V — Phys Rev, 105,877(1957) REF: R CD-0005 ETCH etch TIME: Variable NAME: Tri-iodide removal/polish TEMP: 40—80°C TYPE: Halogen, COMPOSITION: ...I2 4g 20 g ...KI ml... H2O 80 20ml...MeOH DISCUSSION: cadmium alloys. Solution used Cd clean specimens pellets and slugs prior to use and to evaporation, follow with MeOH rinse, DI water rinse, and N2 blow-dry. Also used to in remove cadmium or to clean surfaces after alloying. alloys Fahr, — personal communication, 1978 REF: F CD-0006 NAME: Ammonium hydroxide TIME: ETCH min 10—15 TYPE: cleaning TEMP: RT Alkali, COMPOSITION: x ... NH4OH DISCUSSION: Cd powder used for epitaxy growth of CdSe and (Cd,Se)l _xZnx. Material was cleaned as follows: soak in solution shown, (2) rinse in DI water, and (3) vacuum dry at 50°C. (1) cleaned, without material can be stored for up to 2 weeks Once requiring re-cleaning the surfaces. REF: S U & Parks, MJ — JpnJ Appl Phys, 223,1070(1984) Kim, CD-0008 ETCH TIME: NAME: Mechanical, defect TYPE: TEMP: COMPOSITION: x ... stress DISCUSSION: Cd dislocation free single crystals used in a study of non-basal glide of (1011) oriented wafers in (1210) direction. the Price, Phys, B — J Appl REF: 32,746(1961) P CD-0009: P B — J Appl Phys, 32,1750(1961) Price, Cd, dislocation free single crystals used in a study of non-basal glide (1022) of (1022) oriented in the (1123) direction. wafers CD-0010: Coleman, R V & Sears, O W — Ada Metall, 5,131(1957) Cd, single crystals. Describes a method of growing crystals. © 1991 by CRC Press LLC

222 209 CD-0011 NAME: Hydrochloric TIME: ETCH acid thinning TEMP: TYPE: Acid, COMPOSITION: HC1 ... x x H2O ... DISCUSSION: used in a study of the de-Hass-Van-Allen effect in cadmium at high Cd specimens fields. Solution to reduce thickness of specimens. magnetic used ADC 17,847(1964) Phil Mag, Grasse, REF: — P Kratechuil, Hemela, J — Ada Metall, 14,1757(1966) CD-0012a: & single crystal specimens used in a Cd of dislocations developed in deformed study crystals. annealing to remove oxide, crystals were etch cleaned/polished in HC1 at After 1 min preferential etching. RT, before CD-0012b ETCH TIME: 5 min NAME: Acid, dislocation TEMP: RT TYPE: COMPOSITION: 160 ... CiO3 g g ...Na2SO4 20 ml H2O 500 ... DISCUSSION: single crystals subjected to Cd used in a study of dislocations developed deformation from strain. After etching in solution shown for 5 min, rinse in DI water. Solution used to develop dislocations. Ibid. REF: CD-0003b Tri-iodide NAME: TIME: ETCH TEMP: TYPE: to hot polish Halogen, RT COMPOSITION: ...I2 lg 3g ...KI 10 ml ... H2O DISCUSSION: as single crystals and alloy specimens. Cd, used for general removal and Solution polishing. etching, rinse in MeOH. See CD-0005. After Ibid. REF: CD-0013 NAME: TIME: ETCH Mechanical, orientation TYPE: RT TEMP: COMPOSITION: x ... indentation DISCUSSION: Cd single crystal wafer used in a study of lattice and grain boundary diffusion. Indent can surfaces diamond point, and direction of cracks developed a be used to crystal- with lographically orient the material. REF: Wajda, E S — Ada Metall, 3,39(1955) C CD-0014: G & Hien, N L — Phys Rev, 110,1002(1958) Lang, Cd single crystal wafers cut from ingots by an acid saw technique. © 1991 by CRC Press LLC

223 210 CRC of Metal Etchants Handbook CD-0015 ETCH TIME: 1—2 min NAME: Trichloroethylene cleaning Hot Solvent, TEMP: TYPE: COMPOSITION: x ... TCE DISCUSSION: pre-forms and alloy wire. Parts were vapor degreased in TCE before use Cd cut in microelectronic and package assemblies. After degreasing, parts were stored devices alloying nitrogen dry box until ready for use. a in Marich, L A et al — personal communication, 1983 REF: PROPERTIES PHYSICAL CADMIUM ANTIMONIDE, CdSb OF Antimonide Classification 48 & 51 Atomic numbers 234.17 weight Atomic point (°C) 1000 Melting (°C) Boiling point (g/cm3) Density Hardness (Mohs — scratch) 6—7 structure (isometric — Crystal (100) cube normal) Color Metallic grey (solid) (cubic) Cleavage (001) CADMIUM ANTIMONIDE, CdSb Does not occur as General: natural metallic compound, although there is native an a timony, and half a dozen minerals as arsenides, su If ides, not including several antimonates, etc. The important mineral is stibnite, Sb2S3, as an ore which may contain both gold most silver. and no industrial application at present other is being evaluated as a compound There than semiconductor. Application: Cadmium antimonide is a II—V compound semiconductor Technical and has evaluated for characterization of its physical and semiconducting properties. been or Etching: single acids, mixed acids, other halogens. HC1, CADMIUM ANTIMONIDE ETCHANTS CDSB-0001 ETCH NAME: Hydrochloric acid TIME: TYPE: Acid, TEMP: polish COMPOSITION: x HC1, cone. ... DISCUSSION: (100) wafers used in a CdSb, of indium doping acting as a donor impurity. With study increase of indium, diamagnetism becomes temperature dependent. Develops two types of bonds holes and Sb) as local donor sites with 3 Sb sp-hybrid (In and mixed conduction. REF: Pilat, I M — Phys Rev, 110,354(1959) © 1991 by CRC Press LLC

224 211 PHYSICAL OF CADMIUM ARSENIDE, Cd3As2 PROPERTIES Arsenide Classification 48 & 33 Atomic numbers 486.05 Atomic weight > 1000 Melting (°C) point point Boiling (°C) Density (g/cm3) ~6 — scratch) 6—7 Hardness (Mohs (isometric — normal) (100) cube Crystal structure normal) prism — (hexagonal (10T0) Greyish Color (solid) (0001) Cleavage (basal) CADMIUM ARSENIDE, Cd3As2 Does not occur in nature as a metallic compound and, General: present has no industrial at application than as a possible semiconductor compound. other compound Application: is a II—V arsenide semiconductor and has Technical Cadmium evaluated for its physical and semiconducting characteristics alone and as a been mixed single of Cd3As2:Zn3As2. crystal HC1, acids. acids, and mixed Etching: other ARSENIDE CADMIUM ETCHANTS CDAS-0001 ETCH NAME: Hydrochloric acid TIME: TYPE: Acid, polish TEMP: COMPOSITION: x HC1, cone. ... DISCUSSION: single specimens and Cd3As2:Zn3As2 as mixed crystal crystals used in a Cd3As2 single of the anomalous thermal conductivity of these materials. Solution shown will polish study materials. both J Spitzer, et al — P Appl Phys. 37,3795(1966) REF: D PROPERTIES PHYSICAL CADMIUM FLUORIDE, CdF2 OF Classification Fluoride Atomic numbers 48 & 9 Atomic weight 150.4 Melting point 1100 (°C) point 1758 Boiling (°C) Density (g/cm3) 6.64 (Mohs — scratch) Hardness 2—3 Crystal structure (isometric — normal) alpha (100) cube, bec (isometric — tetrahedral) beta (111) tetrahedron Color (solid) White / (cubic/octahedral) Cleavage 11) (001)/(l CADMIUM FLUORIDE, CdF2 General: Does not occur in nature as a compound due to its solubility in water. The © 1991 by CRC Press LLC

225 212 CRC of Metal Etchants Handbook form is cubic (bcc), and the normal room temperature structure; whereas alpha body-centered form the high temperature structure. Atomic structure is similar to fluorite, CaF2, is beta the or cell eight fluorine atoms surrounding a central Cd unit Ca atom (bcc). The main a with of cadmium as the pure metal comes from sphalerite, ZnS, source a constituent trace of as in ore (about 0.2%), and there are three minor cadmium minerals: as a sulfide, element the carbonate. and oxide, been little use as the fluoride in industry There date, but as a sulfide (CdS) it is has to of the one and most stable yellow pigments used in paints, and for the coloring of best glass. metals as an alloy with bismuth are low temperature alloys. Cadmium Application: No use in Solid State processing to date, although it has Technical major for grown as a single crystal both studied general morphology and, when doped, been and its semiconducting properties. As a CVD thin for it has been evaluated as a dielectric, film as has optical properties similar to fluorite, but is less used due to it solubility. Thin water films have been used for cadmium also doping of semiconductor materials. drive-in Etching: Soluble in water and acids. CADMIUM FLUORIDE ETCHANTS CDF-OOOla ETCH TIME: NAME: Water polish/removal RT Acid, TEMP: TYPE: COMPOSITION: x ... H2O DISCUSSION: As the material is slightly soluble in cold CdF2 water can be used to specimens. water, surfaces. Mix with alcohol {Note: reduce etch rate.) polish to Hodgman, C D et al — Handbook of REF: and Physics, 27th ed, Chemical Chemistry Rubber Cleveland, OH, 1943, 356 Co., Sullivan, W — J Vac Sci Technol, B2,202(1984) CDF-0004: P as CVD deposited thin films on GaAs wafers CdF2 in a study of dielectric coatings. used After resist patterning, film was photo annealed (EBA). Fluorine desorbs during E-beam annealing, and the remaining CdFx can be removed by water washing. Also studied SrF2 (SRF-0001). CDF-OOOlb NAME: Hydrofluoric TIME: ETCH acid Acid, TEMP: RT TYPE: polish/removal COMPOSITION: x ... HF, cone. (2) x ... HF (3) x ... (1) HF x... x ... MeOH/EOH H2O DISCUSSION: to HF solutions CdF2 be used specimens. polish surfaces, or for general removal. can Solution (3) is best for rate control, as CdF2 is insoluble in alcohols. REF: Ibid. CDF-0003 ETCH Heat TIME: NAME: Thermal, annealing TYPE: 600—800°C TEMP: COMPOSITION: x ... heat DISCUSSION: undoped CdF2 crystal ingots, as both doped and single materials. Used in a study of © 1991 by CRC Press LLC

226 213 expansion and semiconducting properties. During annealing, if oxygen is present coefficients brownish CdOx will form on the ingot surface. a film Phys L Fortiz, M — J & Chem Solids, 46,401(1985) Acuna, REF: A SELENIDE, CdIn2Se4 CADMIUM INDIUM cadmium not as a natural compound. See occur selenide for additional General: Does discussion. general Application: Cadmium indium selenide is a ternary semiconductor compound Technical with polar similar to binary compounds. It is a ternary chalcogenide under characteristics as and its semiconductor capabilities both for a bulk single crystal development application as well as an amorphous glassy material. element compound, and other chalcogenides, This have been to fabricate circuits as an alterable used memory ele amorphous-semiconductor ment for computer applications. Etching: Aqua regia and additive mixtures of aqua regia solutions. CADMIUM INDIUM ETCHANTS SELINIDE CDISE-OOOla ETCH regia, variety TIME: NAME: Aqua polish Acid, TYPE: TEMP: COMPOSITION: HC1 ... 4 ... HNO3 1 DISCUSSION: single crystal specimens used to fabricate photoelectrochemical cells from CdIn2Se4 chalcogenides. ternary mechanically polish with 0.5 \xm alumina. Etch in solution First, RT, follow "poly sulfide". (See CDISE-OOOlb) at shown; seconds, then rinse in 10% with KCN. REF: Tennes, R et al — J Electrochem Soc, 129,1506(1982) CDISE-OOOlb ETCH TIME: NAME: Acid, TEMP: TYPE: polish COMPOSITION: ... *aqua 1 regia 10... 2MKOH -I- S/NajS *3HC1:1HNO3 DISCUSSION: CdIn2Se4 single crystal specimens. Solutions of aqua regia diluted with KOH, S, or Na2S as alternate polishing solutions. (See CDISE-OOOla) used REF: Ibid. CDISE-0002 ETCH NAME: TIME: TYPE: TEMP: COMPOSITION: © 1991 by CRC Press LLC

227 214 CRC of Metal Etchants Handbook DISCUSSION: Chalcogenides amorphous-semiconductor elements for alterable memory ele used as computer ments Excellent discussion of this subject.) applications. in (Note: 1979 — D Devices, Sci Am, December Amorphous REF: Adler, Semiconductor TELLURIDE, CdIn2Te4 INDIUM CADMIUM not occur in nature as General: native compound, although there are a number Does a selenide telluride metallic compounds, but not with cadmium. There are and industrial of no other than as a compound semiconductor. applications, Application: The material is a II—III—VI trinary compound Technical semiconductor and under development as a possible laser diode or for photovoltaic devices. is Soluble in acids of HC1:HNO3 or HF:HNO3 types, and halogens. Etching: mixed TELLURIDE INDIUM CADMIUM ETCHANTS CDITE-0001 NAME: ETCH TIME: 10—30 sec BRM Halogen, polish TEMP: RT TYPE: COMPOSITION: x 1% Br2 ... ... MeOH x DISCUSSION: CdIn2Te4 cut wafers from both p- and n-type doped polycrystalline ingots. Specimens as Surfaces were a study of general morphology. in were chem/mech polished in solution used shown to remove native oxide, lap damage, and contamination. Band gap: 0.88 eV. Dielectric constant: 200. group crystal structure: S4. Space Ou, S S al — J Appl Phys, 57,354(1985) REF: et OF Cdl2 IODIDE, PROPERTIES PHYSICAL CADMIUM Iodide Classification Atomic numbers & 53 48 Atomic weight 366.25 point (°C) 388 Melting Boiling point 713 (°C) (g/cm3) Density 5.67 Hardness (Mohs — scratch) 2—3 structure (hexagonal — normal) (1010) Crystal prism Color Brownish (solid) (basal — Cleavage (0001) perfect) CADMIUM IODIDE, Cdl2 General: Does not occur as a natural compound as it is soluble in water. The mineral greenockite, CdS, the most stable compound and is found in association with sphalerite, is zinc ZnS. a minor constituent in the is sulfide, and is collected during refining Cadmium of the ore. Heated in air pure cadmium metal will burn to a brown powder of cadmium oxide, CdO. though are industrial applications for the There no the sulfide as * "cadmium iodide, yellow" is one of the most stable pigments in paints and as a glass coloring agent. © 1991 by CRC Press LLC

228 215 Technical Cadmium iodide is a II—VIII compound semiconductor and Application: evaluation. It a layered structure similar to CdS and ZrS2 with distinctive basal under is (0001) cleavage. grown as a single crystal by zone been under argon for general study and It has refining Processing is done under argon semiconductor wafers react to moisture characterization. as the in air. most soluble hot and cold Easily and in acids. Etching: water IODIDE ETCHANTS CADMIUM CDI-0001 NAME: Water TIME: ETCH Acid, TEMP: TYPE: polish COMPOSITION: x ... H2O DISCUSSION: Water cleaved from an ingot grown by zone refining Cdl2, argon. wafers (0001) under to polish surfaces. Material is under general study. can be used Unnilrishnan, N V et al REF: J Phys Chem Solids, 45,1205(1984) — PHYSICAL OF CADMIUM OXIDE, CdO PROPERTIES Oxide Classification numbers 48 & 8 Atomic weight 124.41 Atomic Melting point 900 del (°C) Boiling (°C) point Density (g/cm3) 8.192 Hardness (Mohs — scratch) 4—5 Crystal structure — normal) (100) cube (isometric (solid) Brown/black Color (001) Cleavage (cubic) OXIDE, CdO CADMIUM as a natural compound General: called cadmium oxide, CdO. It has been Occurs and as minute octahedrons and as a black, brilliant coating on observed ZnCO3 smithsonite, (calamine), contains trace cadmium and indium. Cadmium metal is easily converted which 350°C. a to by heating in air to about brown There is no industrial application for the oxide oxide, although cadmium metal is an alloy in steels, and has wide use in low temperature solders. Technical The oxide has had no use in Solid State processing to date, Application: semiconductors there a number of compound are containing cadmium as selenides although and tellurides. The oxide has been studied for general morphology as a single crystal, but semi is an unwanted compound in processing cadmium-containing compound considered conductors. Etching: HC1 and NH4OH easily soluble. © 1991 by CRC Press LLC

229 216 CRC Metal Etchants Handbook of ETCHANTS CADMIUM OXIDE CDO-0001 Ammonium TIME: 5—15 sec ETCH hydroxide NAME: TEMP: TYPE: Acid, cleaning RT COMPOSITION: ... NH4OH x DISCUSSION: a surface oxide on cadmium pellets used for metal CdO and epitaxy, or as evaporation cadmium used for soldering. Solution used to clean surfaces. as alloys Fahr, F personal communication, 1978 REF: — CDO-0002 NAME: Hydrochloric acid TIME: ETCH Acid, removal TEMP: TYPE: COMPOSITION: x cone. ... HC1, DISCUSSION: study on cadmium used for epitaxy growth of HgCdTe CdO in a oxide of native films etching and oxidation. Remove cadmium oxides with HC1. chemical Aspenes, D E & Arwin, H — J Vac Sci Technol, A(2), 1309(1984) REF: PROPERTIES OF PHYSICAL CdP2 CADMIUM PHOSPHIDE, Classification Phosphide numbers Atomic 15 & 48 weight Atomic 192.37 (°C) Melting point >1000 Boiling point (°C) (g/cm3) Density 4.5 — (Mohs scratch) Hardness 6—7 (isometric — tetrahedral) structure Crystal (111) tetrahedron (solid) Color Grey-black (octahedral) Cleavage (HI) PHOSPHIDE, CdP2 CADMIUM Does not occur as a natural mineral, although there General: many phosphates with are a radical. The artificial compound has been PO4~ industrially as an additive in making used steels, but has no other major applications. in Technical compound is under evaluation The Solid State as a surface Application: thin film deposited on single crystal indium phosphide, InP, for possible photo diode ap plications. PHOSPHIDE ETCHANTS CADMIUM CDP-0001 ETCH NAME: BRM TIME: TYPE: Halogen, removal TEMP: RT COMPOSITION: x ... 1% Br2 x ... MeOH © 1991 by CRC Press LLC

230 217 DISCUSSION: deposited as thin film on InP, (100) wafers as a photo diode, and studied for CdP2 a Solution shown to etch-form mesa structures in the thin film. used noise generation. — Appl Phys Lett, 39,168(1981) N Susa, REF: OF CADMIUM SELENIDE, CdSe PHYSICAL PROPERTIES Selenide Classification Atomic 48 & 34 numbers 191.3 Atomic weight (°C) point Melting -1000 Boiling point (°C) Density (g/cm3) —6 (eV) 1.8 Band gap (Mohs — 5—6 Hardness scratch) (hexagonal — structure (10T0) prism Crystal normal) Color (solid) Yellowish (basal — distinct) Cleavage (0001) CADMIUM CdSe SELENIDE, Does not as a natural mineral although there are several selenium metallic General: occur as berzelianite, Ag2(S,Se); such Cu2Se; tiemannite, HgSe. There are compounds, aguilarite, applications other than as a compound semiconductor. no industrial Application: Cadmium selenide is a II—V Technical semiconductor with compound hexagonal It is a polar compound with regard to prism, (10T0) faces, and has structure. surface, basal cleavage. distinctive wafer processing is done with the (0001) (0001) Most though second order prism faces, (1120) have been used. It has been grown as a single crystal ingot by the Horizontal Bridgman (HB), Czochralski (CZ), and Zone (FZ) methods. Epitaxy growth on substrates is by Vapor Transport Float and Vapor Epitaxy (VPE). Also developed as the trinary compound: CdSj.xSex. (VT), Phase both variety have been fabricated from devices compounds, such as photoconduc- A of solar cells, piezoelectric devices, photoconductors, and tors, diodes. See CdS for other laser piezoelectric applications. Aqua HNO3. and its varieties and in mixed acids with Etching: Halogens. regia SELENIDE CADMIUM ETCHANTS CDSE-OOOla ETCH NAME: regia, variety TIME: Aqua TYPE: Acid, preferential TEMP: COMPOSITION: 1 HC1 ... ... 3 HNO3 DISCUSSION: (0001) wafers used in a study CdSe, etch pit and structure development of the material. of Authors say that both (0001 )A and (000T)B surfaces develop similar etch figures and a film heavy remains after etching. The Se film can be removed with H2SO4. (Note: selenium This is an extensive article on etching of II—IV compound semiconductors.) — REF: E P et al Warekois, / Appl Phys, 33,690(1962) © 1991 by CRC Press LLC

231 218 CRC of Metal Etchants Handbook CDSE-0002a ETCH TIME: 5 sec NAME: BRM cleaning TYPE: TEMP: Halogen, RT COMPOSITION: 4% ... Br2 x x ... MeOH DISCUSSION: and (1120) CdSe, in a study of surface etching and morphology (0001), (1010), used stability of CdSe:Sx on cells. Dip in BRM solution; rinse in the photoelectrochemical solution, DI H2O, and repeat BRM dip. This was one then several etch polysulfide of evaluated. This was treatment #1. treatments Hodes, O & Manassen, REF: et al — J Electrochem Soc, 128,2325(1981) J CDSE-0002b NAME: Aqua TIME: 15 sec ETCH regia cleaning RT Acid, TYPE: TEMP: COMPOSITION. ... 3 HC1 1 ... HNO3 DISCUSSION: (0001) and other orientations (CDSE-0002a). This is treatment #3: dip in CdSe, fresh aqua rinse in Sx=, then DI H2O, and repeat aqua regia. regia; Ibid. REF: Gatos, H C & Lavine, M C CDSE-0005b: Lincoln Lab Tech Rep, 293, January 1963. — CdSe, (0001) used in a defect study. Aqua regia developed sharply bevelled pits on the (0001)A surface, not on (0001)B, cadmium (A) and selenium (B) surfaces, respectively. but CDSE-0002C ETCH regia TIME: 5 sec NAME: Chrome cleaning RT Acid, TYPE: TEMP: COMPOSITION: CrO3 6 ... HC1 10 ... 4 ... H2O DISCUSSION: (0001) and other orientations (CDSE-0002a). This is CdSe, #2. Dip in solution treatment shown; in Sx= solution, then rinse in DI H2O and repeat chrome rinse dip. {Note: This regia is one variety of the chrome regia etchants.) REF: Ibid. CDSE-0002d ETCH TIME: NAME: Acid, TEMP: RT TYPE: cleaning COMPOSITION: 3 ... HC1 (2) (1) ... C1O3 6 1 ... HNO3 10 ... HC1 DISCUSSION: CdSe, (0001) and other orientations (CDSE-0002a). This is treatment #2, as a com regia; bination #3, then #2. Dip in aqua treatments Sx= solution rinse: water rinse; repeat of aqua regia — follow with chrome regia dip; Sx= rinse; water rinse, and repeat chrome regia. REF: Ibid. © 1991 by CRC Press LLC

232 219 CDSE-0002e NAME: Photo TIME: 4—5 sec ETCH etch cleaning TYPE: TEMP: Electrolytic, RT COMPOSITION: ANODE: ... CATHODE: 9.7 HC1 POWER: 0.3 ... HNO3 H2O ... 90 DISCUSSION: and other orientations (CDSE-0002a). CdSe, is treatment #5. Solution (0001) This was as a photo etch under AMI used and was short circuited with a shown illumination carbon electrode. Use aqua regia #3 treatment, then the electrolytic counter shown, solution rinse Sx~ solution, and water rinse. in Ibid. REF: CDSE-0002f Aqua variety TIME: 4—5 sec ETCH regia, NAME: cleaning TEMP: TYPE: Acid, RT COMPOSITION: 97% ... HC1 3% ... HNO3 DISCUSSION: as a deposited CdSe thin film on a titanium substrate. This is treatment polycrystalline #6 a reduced activity aqua regia solution using reduce etch rate on the thin polyfilm. to Follow treatment #3 procedure (CDSE-0002b) using solution shown above; then the photo etch step under CDSE-0002e. shown Ibid. REF: CDSE-0002g TIME: NAME: To ETCH 20 h TEMP: reactive Electrolytic, TYPE: 35°C COMPOSITION: ANODE: M KOH CATHODE: x ... 1 ... NajS POWER: x x... S ... x H2O DISCUSSION: a (0001), and (1120) wafers used to study the overgrowth of CdS CdSe, (1010) from polysulfide and decay of photoelectric electrolyte following different surface treat current ments to include polycrystalline thin film CdSe on titanium substrates. The electrolyte shown was used evaluation vehicle, e.g., S will replace Se in CdSe until CdS film stabilizes as the thickness in stabilizes the CdSe/CdS interface. and REF: Ibid. CDSE-OOOlb ETCH NAME: TIME: 8 sec TYPE: Acid, preferential TEMP: 40°C COMPOSITION: 1 HC1 ... ... HNO3 30 ... CH3COOH (HAc) 10 DISCUSSION: CdSe, (0001) wafers used in a study of etch pit and structure development of II—IV © 1991 by CRC Press LLC

233 220 CRC of Metal Etchants Handbook semiconductors. The surface developed aligned hexagonal pits in the compound (0001) with both (OOOl)Se surfaces were coated and selenium after shown; solution (0001)Cd can be removed by dipping in H2SO4. etching, which REF: Ibid. CDSE-0003 Aqua regia, dilute TIME: ETCH NAME: polish Acid, TYPE: TEMP: COMPOSITION: HC1 3 ... HNO3 1 ... 12 ... H2O DISCUSSION: polycrystalline thin films deposited on titanium electrodes. The dilute aqua regia CdSe solution shown used to clean and etch polish surfaces. (See CDSE-0002f). was Tomkiewicz, M al — J Electrochem Soc, 129,2016(1982) REF: et CDSE-0004 ETCH TIME: NAME: BRM Halogen, TEMP: RT TYPE: cleaning COMPOSITION: ... l%Br2 x ... x MeOH DISCUSSION: n-type wafers used in a study of photocurrent decay in polysulfide CdSe,(1120), elec trolytes corrosion and stability. Back surfaces for wafers were metallized for ohmic contact of with front face exposed in an electrolytic solution. A cotton swab soaked in the solution shown was to wipe-clean surfaces prior to each measurement in the electrolyte. See used CDSE-0002g. 132,1649(1985) & Canfield, D — / Electrochem Soc, K REF: Frese, CDSE-0005a ETCH NAME: TIME: 8 sec Acid, preferential TEMP: 40°C TYPE: COMPOSITION: 0.1 HC1 ... ... 30 HNO3 20 ... 18tfH2SO4 DISCUSSION: (0001) wafers used CdSe, a study of etch pit development. The (0001)A developed in hexagonal etch pits; the (0001)B developed no pits. Both surfaces were coated with selenium films etching. Rinse in H2SO4 to remove residual selenium. after REF: Gatos, H C & Lavine, M C — Lincoln Lab Tech Rep, 293, January 1963 CDSE-OOOlc ETCH TIME: 8 sec NAME: TYPE: preferential TEMP: 40°C Acid, COMPOSITION: 1 ... HC1 10 ... CH3COOH(HAc) 30 ... HNO3 1 ... 8NH2SO4 © 1991 by CRC Press LLC

234 221 DISCUSSION: (0001) wafers in an etch pit development study on II—IV compound semi CdSe, used develops hexagonal pits on (0001)A, only, not on (0001)B. Re etch conductors. Solution films with dip in H2SO4. selenium residual move REF: Ibid. CDSE-0006 NAME: 20 sec ETCH TIME: removal TEMP: RT TYPE: Acid, COMPOSITION: ... 5 HC1 HNO3 1 ... DISCUSSION: Czochralski (1120) CdSe, cleaved from or (CZ) grown ingots. Solution (0001) wafers as a used removal/polish etch. First, mechanically lap with Linde A (0.3 |xm) general alumina, etch in solution shown. Also worked with CdS. then Heller, A al — J Electrochem Soc, 124,697(1977) REF: et CDSE-0007 ETCH NAME: hydroxide TIME: (1) 10—15 min Ammonium (2) Heat Acid, clean TEMP: RT TYPE: 300°C COMPOSITION: x NH4OH (2) x ... heat (1) ... DISCUSSION: and (Cd,Se)xZn,_x CdSe crystal thin films grown in a material study. Prepare single metals by (1) cadmium powder: soak clean in solution shown; DI H2O rinse; dry at 50°C, (2) selenium bake at 300°C, then regrind. Authors caution that improper cleaning powder: cause detonation. can JpnJ S & Park, MJ REF: U Appl Phys, 23,1070(1984) Kim, — CDSE-0008 NAME: Nitric acid TIME: (1) Wash (2) 15 min ETCH Acid, cleaning TEMP: RT 400°C TYPE: COMPOSITION: (1) ... 25%HNO3 (2) x ... heat x DISCUSSION: substrates thin co-evaporated on Ti (0001) CdSe as polycrystalline films. Heat films treat in air at 400°C, 15 min, to homogenize films. Clean CdSe surfaces with HNO3: then in 1 S:5 M Na2S:l M KOH to remove residual selenium. M Haak, — et al REF: J Electrochem Soc, 131,2709(1984) R CDSE-0009a ETCH Aqua regia TIME: NAME: Acid, cleaning TEMP: TYPE: COMPOSITION: (1) 3 ... HC1 (2) x ... 10%KCN 1 ... HNO3 DISCUSSION: substrates. films electrodeposited on CdSe, thin Solution used was 0.1 M titanium CdSO4:0.01 M SeO2:0.5 M H2SO4 at 6 mA/cm3 power. CdSe films were etch cleaned in © 1991 by CRC Press LLC

235 222 CRC of Metal Etc hunts Handbook regia; cyanide (2) used to remove residual Se with DI water rinse. Fabricated aqua solution solar (PECs) with n-type CdSe films. photoelectrochemical as cells R P et al — J Vac Sci Technol, 19,406(1981) REF: Silberstein, ~~ CDSE-0009b ETCH TIME: Xenon NAME: reactive Light, TEMP: TYPE: COMPOSITION: x...Xe DISCUSSION: cleaved wafers used in CdSe study of insulated gate FETs and IGFETs with (1010) a aluminum. Studied contact potential difference (CPD) and time resolved charge evaporated (TRCI) injection the aluminum interface. Wafers were cleaved in an ultra high vacuum at studied. at 10~10 Torr. CdS wafers similarly x Flooding surfaces with high intensity (UHV) 2 light shows potential and injection effects in Al, CdSe and CdS. xenon Ibid. REF: SILICON ARSENIDE, CdSiAs, CADMIUM Does minerals occur as a natural compound; the primary cadmium General: are not but mainly there are several arsenates, although none contain cadmium. There is sulfides, no industrial use, other than as a compound semiconductor. Technical Application: material is a II—IV—V compound semiconductor, and has The laser, evaluated characteristics as a possible its photoconductor, and photo-diode. been for material has been grown as a single crystal, and as a thin film layer in heterojunction The structures. Etching: and mixed acids: HC1:HNO3 or HF:HNO3. HC1, SILICON ETCHANTS CADMIUM ARSENIDE CSA-0001 NAME: TIME: ETCH Acid, TEMP: TYPE: polish COMPOSITION: 1 ... HF 3 ... HNO3 l...H2O DISCUSSION: CdSiAs2, (001) and (111) wafers cut from an n-type, indium doped ingot grown by Vapor Transport in a tin flux. Wafers were etch polished in the solution shown before (VT) silver and contacts were evaporated. gold Avirovic, N REF: al — J Cryst Growth, 67,185(1984) et PHYSICAL PROPERTIES OF CADMIUM SULFIDE, CdS Classification Sulfide Atomic numbers 48 & 16 Atomic weight 144.5 Melting point (°C) 100 atms 1750 Boiling (°C) point Density (g/cm3) 4.82 (4.9—5.0) Refractive index (n =) 2.506—2.529 © 1991 by CRC Press LLC

236 223 Energy gap (eV) 2.45 band (Mohs — 3—3^ Hardness scratch) (hexagonal Crystal alpha m(1010) prism — structure hemimorphic) beta tetrahedron tetrahedral) (isometric — (111) Color (solid) Yellow distinct) a(l 120) Cleavage (prismatic — CdS SULFIDE, CADMIUM three natural compounds with There CdS, the more important, General: are greenockite, is fairly abundant. It is rarely found as crystals, but as as coatings or incrustations it common other primarily zinc compounds, e.g., sphalerite, ZnS (zinc blende). on minerals, an is ore of cadmium, and the natural compound is also used as a yellow industrial It for paints. glass optics there are applications In its piezoelectric properties for in pigment type devices alone or in conjunction with quartz, SiO2. filter Cadmium Selenide, CdSe, (See for similar applications.) Application: Cadmium is a II—V compound semiconductor with hex Technical sulfide faces, It is compound with regard to prism polar (1010), and has distinctive structure. a agonal such that wafer (0001) is usually done with (0001) basal surfaces. The cleavage, processing order prism face, (1120) has been used. second a piezoelectric material it As been dual-evaporated in alternate orientation layer has structure: ... n. As many as 15 thin film layers have been so deposited on CdS/SCd/CdS radio crystals blanks for both frequency alpha-quartz and electronic filter-type frequency structures. both grown CdS a single crystal ingot in is the alpha and beta-CdS form, or epitaxially as deposited as an amorphous thin film, a-CdS. It also occurs naturally as an amorphous film. There is trinary compound as Znx.,CdxS. a it is soft (H = 3—3.5) it has been fabricated as Solid State devices, Although relatively photoconductors, and cells, thin film transistors, as laser diodes. such solar etched acids most Easily and NH4OH. Etching: in SULFIDE CADMIUM ETCHANTS CDS-OOOla ETCH NAME: Hydrochloric acid TIME: Acid, damage removal TYPE: TEMP: COMPOSITION: ... HC1, x cone. DISCUSSION: remove (1013) wafers. Solution CdS, to and cutting and lapping damage (0001) used surfaces. Material used in from defect study. a REF: R A — J Appl Phys, 50,842(1979) Scranton, CDS-00020: A et al — J Electrochem Soc, 123,697(1977) Heller, CdS, (1120) cleaved wafers. Solution used 20 sec at RT to lightly polish clean surfaces as a etch. First lap polish with Linde A (0.3 fxm alumina), then apply solution. general Richaid J et al — CDS-0017: Vac Sci Technol, A2(2), 132(1984) D by thin doped with O2 and deposited CdS spray pyrolysis on glass and sapphire films substrates, or substrates pre-coated with SnO2 or ITO. CdS surfaces were cleaned with HC1 after deposition. — Chikawa, & Namayama, CDS-0019a: J J Appl Phys, 35,2492(1964) T CdS single crystal specimens used in a study of dislocations, structure and growth etch mechanisms. first polished in HC1 before thermal Specimens were treatment to develop defect and structure. © 1991 by CRC Press LLC

237 224 CRC of Metal Etchants Handbook CDS-0005b ETCH acid TIME: 10 sec NAME: Hydrochloric polish TYPE: TEMP: Acid, RT COMPOSITION: 9ATHC1 ... x DISCUSSION: cut perpendicular and parallel CdS, the single crystal ingot c-axis used (100) wafers to study of copper diffusion as insulating in on CdS. Solution was used to polish a layers prior copper evaporation. surface to Ibid. REF: CDS-OOOlb Potassium dichromate TIME: 10 min ETCH NAME: polish/preferential TEMP: 95°C Acid, TYPE: COMPOSITION: K2Cr207 X...0.5M x... 16#H2SO4 DISCUSSION: CdS, Solution used to etch polish both CdS and ZnS wafers with similar wafers. (111) etch a polished surface containing dislocation highly pits on (111)B (sulfur) Produces results. shallow disc-like structure on the surface; (cadmium) surface or (lll)B (zinc) surface. (111)A REF: Ibid. Simheny, et al — J Appl Phys, 39,152(1968) CDS-0005a: M (100) wafers CdS, perpendicular and parallel to the single crystal c-axis used in a cut study of copper diffusion as insulating layers in CdS. Solution used as a preferential etch at 90°C 5—10 min to observe defects induced by copper. for CDS-OOlla ETCH 2 min NAME: TIME: preferential RT (25°C) Acid, TYPE: TEMP: COMPOSITION: ... fuming 6 HNO3, 6...CH3COOH(HAc) 1 ... H2O DISCUSSION: (0001) wafers. The (0001)S surface develops hexagonal etch pits, but CdS, a sulfur only film (0001 )Cd. {Note: HNO3, white fuming = 70%; yellow fuming = 72%; on fuming red = This is a major 74%. on etching II—VI compounds.) article REF: Warekois, E P et al — J Appl Phys, 33,690(1962) CDS-0004a: Gatos, C & Lavine, M C — Lincoln Lab Tech Rep, 293, January 1963 H A (0001) wafers in a similar defect etching study. (Note: CdS, major article on used etching of this compound.) CDS-0002 ETCH NAME: 1—2 min TIME: Acid, RT TIME: TYPE: removal COMPOSITION: 1 HC1 ... 1 ... CH3COOH(HAc) 1 ... H2O DISCUSSION: interest (0001) wafers used with particular CdS, on the (0001)A (cadmium) surface. © 1991 by CRC Press LLC

238 225 Work done with thin film deposits on alpha-quartz substrates as Ag/CdS/quartz. Me also polish CdS then remove lapping damage with solution shown. {Note: The chanically wafers, is a frequency device structure.) Ag/CdS/quartz assembly radio C J Appl Phys, 47,366(1976) Lubbert, REF: — CDS-OOllb TIME: ETCH NAME: preferential Acid, TYPE: TEMP: COMPOSITION: HC1 ... 1 ... HNO3 1 DISCUSSION: wafers. This solution CdS, conical etch pits on (0001)S surfaces that (0001) develops hexagonal form. The (0001)Cd surface is rough and granular. approach REF: Ibid. CDS-0003 ETCH acid TIME: 1 min NAME: Hydrochloric preferential TEMP: Hot TYPE: Acid, COMPOSITION: x HC1 vapor ... DISCUSSION: (0001) wafers used in an etch pit study. Wafers were wetted in water prior CdS, to being in HC1 vapor to develop etch pits. held Eland, Rev, J — Phillips Tech REF: 22,266(1960—1961) A — Pisarerko, CDS-0012: & Sheinkman, M K Zh Sov Phys (Solid State), 3838(1960) D CdS, (0001) cleaved wafers used in a study of dislocations. Hold wafers 4—5 cm above 20—30% HC1 in the vapors at 100°C for 1—2 min, then wash in DI H2O. Other liquid evaluated, this solution gave the best results. etchants but Reynolds, D C & Czyzak, S J — / Appl Physt 31,95(1960) CDS-0013: (0001) study used in a CdS, of dislocations. Used a boiling solution of HC1 with wafers H2O wafers hot vapors, and followed with DI in rinse. The (0001)A surface does not held develop pits; the (0001 )B surface develops pits. Two dislocation density materials evaluated: 101 and 107/cm2. CDS-0022 ETCH TIME: NAME: Perchloroethylene cleaning Solvent, TYPE: TEMP: COMPOSITION: x...CC12:CC13(PCE, Perk) DISCUSSION: CdS, wafers. Mechanical lap and polish and then clean with the following sequence: (100) (1) decrease in PCE, (2) wash in HC1, (3) DI water rinse, and (4) rinse in acetone. REF: J W — J Electrochem Soc, 128,1817(1981) Sherohman, CDS-0006a ETCH NAME: TIME: 2—3 min TYPE: preferential TEMP: RT Acid, COMPOSITION: x ... H2SO4 x ... 0.3MKMnO4 © 1991 by CRC Press LLC

239 226 CRC of Metal Etchants Handbook DISCUSSION: CdS, Referred to as a new optical quality etch for II—Y compounds. (100) wafers. slowly a color. The permanganate should be added green as there is violent is dark Mixture the sulfuric acid. Produces smaller etch pits (?) and a cleaner surface than reaction with the Etch". CDS-0002.) This etch was compared to HC1; H3PO4 and dilute "Chromate (See See which etches for II—V compounds. {Note: are Silicon Dioxide section for HNO3 also standard glass cleaner solution.) comparative Rowe, REF: E & Forma R A — J Appl Phys, 39,1917(1968) J CDS-0007a ETCH acid TIME: NAME: Hydrochloric preferential, Hot TEMP: Acid, TYPE: vapor COMPOSITION: x HC1, vapors ... DISCUSSION: (0001) wafers used in a study of defects and dislocations. Wafers were suspended CdS, HC1 vapors. The (0001)A surface develops dislocation etch pits; none on (000T)B. in Woods, Appl — BrJ REF: Phys, 11,296(1960) J C Reynolds, CDS-0008: & Green, L R — J Appl Phys, 29,559(1958) C This reference cited for use of HC1, vapor. CDS-0007b ETCH TIME: 10 min NAME: Acid, preferential 80°C TYPE: TEMP: COMPOSITION: ml H2SO4 5 ... 1250ml...H2O lg ...Cr2O5 DISCUSSION: and (1010) wafers CdS, in a study of defects and dislocations. Place wafers (0001) used solution at RT and bring in to 80°C; rinse in DI water, then in MeOH. Etch pits results up were as follows: sec Hexagonal with variable side lengths. Etch for (0001)A: pits only and pit sides are 30 of equal length. (0001)B: Conical pits only. (1010): Triangle side perpendicular to the c-axis; apex in the (000T)B direction. pits—one (1120): No developed. pits Ibid. REF: CDS-0009: E — Seitz Naturforsch, 13a,542(1958) Votava, CdS specimens. Used HC1 by immersion, rather than as hot vapor. Results were similar to those in CDS-0007a. obtained CDS-0010 ETCH Hydrochloric acid, dilute TIME: NAME: Acid, cleaning TEMP: RT TYPE: COMPOSITION: x ... HC1 x...H2O DISCUSSION: CdS, (0001) wafers used to fabricate photojunctions by diffusing copper into insulating © 1991 by CRC Press LLC

240 227 CdS. surfaces were rinsed in the solution shown and then in DI water prior to copper Wafer diffusion. REF: R et al — J Appl Phys, 32,1324(1961) Rockemuehl, R M J & Bracht, W R — Sullivan, Electrochem Soc, 114,295(1967) CDS-0014: V chem/mech (lll)_wafers. as 30HCl:70H2O as a used polish for both the CdS, Solution and (lll)S surfaces using rotation on a pellon type cloth. (lll)Cd CDS-0015a ETCH TIME: NAME: TYPE: Acid, RT polish TEMP: COMPOSITION: g KC1 13.7 ... ... HC1 0.5 ml ... H2O ml 100 DISCUSSION: (111) wafers. CdS, used as a chem/mech polish at 58 rpm rotation on a pellon- Solution type pad. Used to polish the (lll)Cd surface. REF: Pritchard, A A & Wagener, S — J Electrochem Soc, 124,961(1977) CDS-0015b ETCH TIME: NAME: Acid, polish RT TYPE: TEMP: COMPOSITION: g KC1 13.3 ... ... 16 ml HC1 ml ...H2O 100 DISCUSSION: (111) wafers. Solution used as in CdS, to polish the (lll)S wafer surface. CDS-0015a REF: Ibid. CDS-0016 ETCH TIME: NAME: Acid-slurry, polish TEMP: RT TYPE: COMPOSITION: ml ... HNO3 90 10 g ...AgCl3 1000 ml... H2O 300 ml silica ... DISCUSSION: wafers wafer. Solution used to CdS, polish (0001) at 240 rpm with pellon- chem/mech type pad. REF: Pickhardt, V Y & Smith, D L — J Electrochem Soc, 124,961(1977) CDS-OOllc NAME: TIME: 5—15 min ETCH TYPE: Acid, polish TEMP: 95°C COMPOSITION: x... 16ATH2SO4 x ...0.5WK2Cr2O7 © 1991 by CRC Press LLC

241 228 CRC of Metal Etchants Handbook DISCUSSION: CdS, Solution is a general polish for (lll)Cd surfaces, but develops (1010) wafers. on (TTT)B surfaces. pits etch the REF: Ibid. CDS-0007c TIME: 10 min ETCH NAME: preferential 80°C Acid, TYPE: TEMP: COMPOSITION: ml H2SO4 1 ... ... Cr2O3 0.08 g ... H2O ml 100 DISCUSSION: (1010) wafers. Solution used as a preferential etch. CdS, REF: Ibid. CDS-0018 ETCH NAME: TIME: preferential Acid, TEMP: TYPE: COMPOSITION: HCl 2 ... EOH ... 5 DISCUSSION: (0001) wafers used in a study of electrochemical coupling. Solution used CdS, develop to pits defects. and Wilson, B—JAppl Phys, 37,1932(1966) REF: R CDS-0019b NAME: Heat TIME: ETCH 2—5 sec (1) TYPE: Thermal, dislocation TEMP: (1) RT COMPOSITION: (1) x ... HCl, cone. (2) x ... heat DISCUSSION: CdS, crystal specimens used in a study of dislocations, structure and growth single to Specimens HCl before thermal etching in develop dislocations and mechanisms. polished structures. Chikawa, J & Nakayama, T — J Appl REF: 35,2492(1964) Phys, CDS-0021 NAME: V2 h ETCH TIME: Acid, removal/cleaning TEMP: TYPE: Boiling COMPOSITION: 1 ... 5%NaOH 1 ... 10%NaCN DISCUSSION: hole CdS plated and diffused used in a study of the dependence of copper wafers ionization relative to imperfections and energy concentration. Solution used to wash impurity and remove excess copper remaining after diffusion; follow with water rinsing until pH paper neutral. is REF: Bube, R H & Dreeben, P B — Phys Rev, 115,1578(1959) © 1991 by CRC Press LLC

242 229 CDS-0023 NAME: ETCH Xenon TIME: TEMP: TYPE: Light, reactive COMPOSITION: x ... Xe DISCUSSION: and CdSe (1010) cleaved wafer in UHV. Wafers CdS, as (0001) wafers fabricated devices aluminum gates for IGFETs. High with xenon light will gate insulated intensity activity of aluminum in both materials. See: CDSE-0009a-b. affect the Technol, R al — J Vac Sci et 19(3),406(1981) REF: P Sinerstein, OF PROPERTIES PHYSICAL CADMIUM TELLURIDE, CdTe Telluride Classification 48&52 numbers Atomic 240 Atomic weight 1041 point (°C) Melting Boiling point (°C) 6.20 Density (g/cm3) 1.45 Energy band gap (eV) 5—6 (Mohs scratch) — Hardness (isometric (111) tetrahedron tetrahedral) — structure Crystal Black (solid) Color (001) Cleavage (cubic distinct) — TELLURIDE, CdTe CADMIUM Does not occur as a natural compound. There General: several tellurides and tellurates are with and other metals. Cadmium telluride has had little iron in industrial metal processing, use other than as a compound semiconductor. Technical Application: Cadmium telluride is a II—V compound semiconductor with the sphalerite, ZnS, It is similar to other polar type compounds with positive (111) structure. opposed surfaces l)Cd, and negative (11 l)Te (11 wafer surfaces which show different water as characteristics, such that the material is more often used in the (100) orientation for etching processing, device the polarity effects have been widely studied. It has been grown though (HB), as crystal by the Horizontal Bridgman single Czochralski (CZ), and Float Zone a (FZ) methods. Also grown as an epitaxy thin film by Vapor Transport (VT), Chemical Vapor Deposition and by Vapor Phase Epitaxy (VPE). It is isomorphous with InSb, (CVD), CdxHglxTe. further as a trinary semiconductor: grown Devices made from both the and binary and trinary compounds include photoconductors, photodiodes, and laser diodes. halogens. Etching: of HF:HNO3, HC1:HNO3, and acids Mixed CADMIUM TELLURIDE ETCHANTS CDTE-0006b ETCH NAME: EAgl etch TIME: TYPE: preferential TEMP: Acid, COMPOSITION: 10 ml ... *Eetch 5 mg ... AgNO3 *See CDTE-0015b © 1991 by CRC Press LLC

243 230 CRC of Metal Etchants Handbook DISCUSSION: CdTe, and (110) wafers. The (110) wafers were cleaved; the (100) and (100), (111) with saw orientations were mechanically polished All "chrome green" (CrO) were cut. (111) |xm grit. Several etches developed as polish as preferential solutions for studying 1—3 and polarity defects. (Note: Cr2O3 is the and green form of chromium oxide.) CdTe normal Inoue, M et al — J Appl Phys, 33,2578(1962) REF: Iwanaga, H J — J Cryst Growth, 62,690(1979) CDTE-0031: structures. (111) wafers used in a study of pit (110) Solution used at RT, 3 min. CdTe, and (lll)A surface develops triangle pits; (lll)B also developed triangle pits, but The deeper than (lll)A. Isosceles triangles with pointed bottoms developed on the (110)B, and on Etch similar flat bottoms on the (110)A. with time 3 min at RT. pits CDTE-0006a ETCH NAME: E etch TIME: TYPE: Acid, TEMP: RT polish COMPOSITION: 10ml...HNO3 20ml...H2O 4g ...K2Cr2O7 DISCUSSION: and (110) wafers used in CdTe, of defect etches and a study (100), (111), development polarity effects on CdTe. This solution is a polishing etch and was of before preferential used etchants applied. See CDTE-0006b-f. were Ibid. REF: Ibid. CDTE-0017d: (111) wafers. Solution used at RT with agitation CdTe, produced a mirror polish. and Rate: 4.2 fim/min. See CDTE-0017a. CDTE-0006c ETCH NAME: EAg2 etch TIME: TYPE: Acid, TEMP: RT preferential COMPOSITION: 10 *EEtch ml ... mg AgNO3 10 ... ♦See CDTE-0006a DISCUSSION: CDTE-0006a,b CdTe, and (110) wafers. See (111), for discussion. (100), REF: Ibid. CDTE-0006d ETCH NAME: P etch TIME: TYPE: Acid, TEMP: RT polish COMPOSITION: 10 ml... HC1 10ml...HNO3 5 ml ...H2O DISCUSSION: CdTe, (111), (100) and (110) wafers. Solution used as a polishing etch prior to pref- © 1991 by CRC Press LLC

244 231 erential for defects and polarity effects. See other CDTE-0006 references for ad etching discussion. ditional REF: Ibid. CDTE-0017e: Ibid. Solution produces pits as used at RT with wafers. Rate: 12.S (111) CdTe, agitation. CDTE-0017a. See fjim/min. CDTE-0006e ETCH etch TIME: NAME: PBr Halogen, TEMP: RT TYPE: preferential COMPOSITION: 10 (1) Petch (2) ml ml ... Petch 10 ... mg ... Br2 5 mg ... Br2 10 DISCUSSION: CdTe, (100), and (110) wafers. Both solutions develop etch pits. They also can (111), CDTE-0006 used junction delineation solutions. See other p-n references for further be as discussion. Ibid. REF: CDTE-0006f ETCH Heat TIME: NAME: Thermal, preferential TEMP: 600°C TYPE: COMPOSITION: x heat ... DISCUSSION: (111), (100), and (110) CdTe, used in developing polish and preferential etch wafers solutions and other methods of developing structure. Wafers were placed in vacuum at 5~10 mmHg. Thermal develops etch structures that can be correlated with chemical liquid etching See other references. etching. CDTE-0006 Ibid. REF: CDTE-0012a NAME: TIME: ETCH TYPE: float-off TEMP: Acid, COMPOSITION: x HNO3 ... ... H2O x DISCUSSION: (0001) films CdTe, on muscovite mica thin cleaved substrates. After growth the grown films were removed from the mica by the float-off technique with the solution shown for TEM study structure. of Davenere, 70,452(1984) et al — J Cryst Growth, REF: A CDTE-OOOla ETCH TIME: 2 min NAME: Acid, preferential TEMP: RT TYPE: COMPOSITION: 3 HF ... 2 ... H2O2 1 ... H2O DISCUSSION: CdTe, (111) wafers. The (11 l)Cd surface shows a near-polish with cup-like figures that © 1991 by CRC Press LLC

245 232 CRC of Metal Etchants Handbook upon further The (TU)Te surface develops triangular etch pits. The Te disappear etching. dipping remains can be removed by etching in HC1. that film after E P et al — J Appl Phys, 33,690(1962) REF: Warekois, Ibid. CDTE-0017f: CdTe, Solution used at RT with agitation. Polished the (lll)Cd surface. (111) wafers. jim/min. Rate: CDTE-0017a. 3.4 See CDTE-OOOlb ETCH TIME: 8—10 min NAME: Acid, polish TYPE: RT TEMP: COMPOSITION: ...HF 1 1 ...HNO3 DISCUSSION: etch Described as a CdTe, polish wafers. for both wafer surfaces, (lll)A (111) good (!TT)B, and does not develop etch pits. The grey tellurium film and after etching remaining can removed by dipping in HC1. be Ibid. REF: CDTE-OOOlc ETCH NAME: TIME: Acid, preferential TEMP: TYPE: COMPOSITION: 2...HF 3 ... HNO3 1 ... H2O DISCUSSION: CdTe, (111) wafers. Solution will develop triangle etch pits on the (lll)B face but a semi-polish on (lll)A. Ibid. REF: CDTE-0002 TIME: ETCH NAME: Acid, polish TEMP: TYPE: COMPOSITION: ... H2SO4 (2) (1) ... Br2 x x ... K2Cr2O7 x ... MeOH x DISCUSSION: (111) n-type CdTe, doped with either aluminum or chlorine. Wafers were first wafers number mechanically etch polished in the then (1) solution shown. After etching, polished, rinse in the BRM number (2) solution. REF: Vazquez-Lopez, et al — J Appl Phys, 50,5390(1979) C Ibid. CDTE-0017g: (111) wafers. Solution mixture was CdTe, and was used at RT 3gH2SO4:7gK2Cr2O7, with agitation. Produced polished surfaces. Rate: 2.3 jjim/min. See CDTE-0017a. CDTE-0024b: Ibid. CdTe, (111) wafers and other orientations used in a study of anodic oxidation. Etch clean wafers in solution (1) before oxidation. © 1991 by CRC Press LLC

246 233 CDTE-0004 NAME: ETCH min (2) 30 sec TIME: (1) 1 TEMP: RT Acid, TYPE: preferential RT COMPOSITION: (2) ...0.1%Br2 HF (1)3... x x ... MeOH 2 ... H2O2 H2O 1 ... DISCUSSION: in and Solution used to CdTe, defect ingots. both wafers and wafers (111) develop a study of twinning. Etch in solution (1) and DI water rinse; follow with solution ingots in polish surfaces DI The BRM solution will rinse. accentuating the defects water (2) and the acid solution. See CDTE-OOOla. developed by Mater, A et al — J Electron W 12,551(1983) REF: Vere, CDTE-0005a NAME: ETCH TIME: isotropic & TYPE: defect Acid, TEMP: COMPOSITION: ml 5 x 0.5% (1) Br2 ... HNO3 ... 42 (3) HF (2) ... x MeOH ml 10 H2O 20 ... H2O2 2 K2Cr207 29 ... H2O g DISCUSSION: a Mechanical lap with CdTe, on (111) glass plate in the following wafers. abrasives (1) 240-grit SiC; (2) order: SiC and (3) 0.3 |xm alumina. Then use solution (1) to 600-grit chem/mech by dripping solution onto a polishing pad with hand lap or mechanical polish area Wax surfaces with a pattern opened coat with the black wax (Apiezon-W) rotation. acting as a dike. Use etch solution (2) to chemically etch-mill pits into the bulk CdTe surface. Then use (3) as a defect etch to develop dislocations in the previously etched pits. solution will develop in the material bulk. Remove the dark Te film remaining in pits This defects for etching alcohol. (Note: See Silicon, SI0092a-k with similar bulk defect after defect study.) Weirauch, D F — J Electrochem Soc, REF: 132,250(1985) CDTE-0005b NAME: TIME: discussion ETCH See isotropic Acid, TEMP: RT TYPE: defect COMPOSITION: "A" 5 ml ... HNO3 (1) x ... H2O (2) 42 ... HF "B" 10 ml ...H2O 29 ...H2O2 2g ...K2Cr2O7 29...H2O DISCUSSION: CdTe, (111) wafers. Mechanically polish: (1) 5 |xm, then (2) 0.3 |xm alumina. Plate surface with using AuCl3, 15 sec. (Note: Standard electrolytic gold plating bath or gold etch electroless?). (1) as 4 *'A":r*B", and solution polish surfaces after first scratching Mix through gold film to induce microcracks in the CdTe. Then polish etch, RT, 2 sec into RT, scratched solution (2) as a defect etch, Use 20 sec. Remove grey Te film in areas. etched areas with solution (1). Cleave wafers on (110) for observation and study of scratched damaged zones in cross-section. REF: Ibid. © 1991 by CRC Press LLC

247 234 CRC of Metal Etchants Handbook CDTE-0007 ETCH NAME: TIME: polish TYPE: TEMP: Acid, COMPOSITION: HF ... 3 ... H2O2 2 l...H2O DISCUSSION: Authors say that CdTe, solution leaves a high Te content surface film (111) wafers. this and suggest that high electropositive elements tend to after at the surface for etching pile-up unknown. CDTE-OOOla, where solution was developed and used as a preferential reasons See etch. Films, T et al — Thin Solid REF: 113,157(1984) Reiyi, V CDTE-0008 ETCH NAME: BRM TIME: Halogen, polish TYPE: RT TEMP: COMPOSITION: ... Br2 x MeOH x ... DISCUSSION: wafers grown by the Horizontal Bridgman (HB) method, and used for CdTe, (111) oriented of on both (lll)A and (lll)B CdTe surfaces. Wafers were me growth epitaxy lapped and then polished chanically a BRM solution prior to epitaxy. Epitaxy growth in was Vapor Transport (VT) using a vertical, three-zone furnace under argon with wafers by the at Epitaxy would grow only on bottom. (111)A surface and showed triangular steps the with (110) slopes. Note: Argon was used to thermally_etch both surfaces while still in the growth system: (111)A showed terracing; whereas (111)B showed random etching only. the Kuwamoto, H / Cryst Growth, 69,204(1984) REF: — CDTE-0009 NAME: TIME: 5 ETCH min BRM removal/polish Halogen, RT TYPE: TEMP: COMPOSITION: x ... 2%Br2 ... MeOH x DISCUSSION: CdTe, wafers, n-type, high resistivity. Mechanically polish with 0.3 \im alumina, (111) p,m. etch then solution shown to remove about 20 with A Te rich surface film is left. the Rinse in MeOH to remove residual bromine, DI water rinse, and N2 blow dry. Place wafers Cd in hold 8 h at 900°C with 0.5 atm Cd back-pressure to suppress and vacancies. vacuum, Then indium pads for ohmic evaporate See CDTE-0005a and CDTE-0002. contact. REF: Nozaki, S et al — / Electron Matert 14,137(1985) CDTE-0021: A et al — J Appl Phys, 39,5336(1968) Sagar, CdTe, (111) wafers. Used a 0.5% Br2:MeOH solution as a general polishing etch, RT, surface up 45 min. Clean Te to deposits that remain with CS2. © 1991 by CRC Press LLC

248 235 CDTE-0010 NAME: BRM ETCH TIME: polish TYPE: TEMP: Halogen, RT COMPOSITION: 10% ... Br2 x x ... MeOH DISCUSSION: p-type. After CdTe, lap and polish, degrease in TCE, and (111) wafers, mechanical DI water. Use rinse shown to etch polish surfaces. in solution Selim, A & Kroger, E A — J Electrochem Soc, F REF: 124,401(1977) CDTE-OOlla ETCH NAME: TIME: TYPE: Acid, dislocation TEMP: COMPOSITION: x ... x% Br2 (2) 3 ... HF (3) x ... (1) Br2 2% x MeOH 2 ... H2O2 x ... glycol ... ... H2O 3 DISCUSSION: of used as substrates for epitaxy (111) wafers CdTe on both (11 l)Cd and CdTe, growth surfaces by LPE (liquid phase epitaxy) — deposited substrate surfaces were rich (lll)Te Te. in preparing substrates, use solution (1) as a polish etch. After epitaxy, use solution In Follow to dislocations in the epitaxy layers. develop with solution (3) to remove black (2) "smut" remaining after dislocation etching by dip cleaning, RT, 5 sec, then MeOH rinse, DI water and N2 blow dry. Dislocation etch (2) develops star-shaped pits and low angle rise, between boundaries epitaxy layers that show correspondence the the two polar wafer grain in Astles, M et al — J Electron Mater, 13,167(1984) REF: CDTE-OOllb ETCH TIME: NAME: Acid, preferential TEMP: RT TYPE: COMPOSITION: 1 HC1 ... 1 ... HNO3 DISCUSSION: reaction (111) CdTe, in an etch wafers study. The (lll)Cd surface develops used triangular etch pits with a surface background of shallow, triangular etch figures. The (TTT)Te surface is with a Te film in which triangular figures appear to have been etched. covered Ibid. REF: CDTE-0012b NAME: TIME: ETCH BRM Halogen, polish TEMP: TYPE: RT COMPOSITION: x ... 1% Br2 x ... MeOH DISCUSSION: CdTe, wafers used for epitaxy (111) of CdTe/Bi/CdTe (111). Muscovite mica, growth cleaved (0001), also used as a substrate — blow mica clean with N2, and apply no liquids. © 1991 by CRC Press LLC

249 236 CRC of Metal Etchants Handbook polish CdTe in solution shown before epitaxy. Material used in a study of Etch substrates superlattice capability. et al — J Cryst Growth, 70,452(1984) Davenere, REF: A Sci et — J Vac al Tecknol, A2(2),418(1984) Pessa, CDTE-0020: M p-type wafers used as substrates for epitaxy CdTe, of CdTe thin films. (111), growth were polished in a BRM solution. Final clean in vacuum with chem/mech ion Wafers Ar+ for 10 min at 2.5 KeV power. bombardment Bhat, I & Ghandhi, S K — J Electrochem Soc, 131,1923(1984) CDTE-0021: (100) CdTe, cut 3°-off toward (110), and used for epitaxy growth of HgTe thin wafers Clean substrates follows: (1) degrease with solvents, and (2) etch in 2% Br2:MeOH as films. and 20 of surface depth jxm polish simultaneously. remove to CDTE-0013 NAME: TIME: ETCH Acid, TEMP: RT TYPE: polish COMPOSITION: ...HF 3 2...H2O2 2 H2O ... DISCUSSION: (111) wafers used as substrates for epitaxy growth of HgCdTe on CdTe and (lll)Cd (lll)Te in a study of epitaxy surfaces and lattice mismatch. Solution used to morphology etch polish wafers prior to epitaxy. The negative Te surface produced the better lattice match. REF: Edwall, et al — J Appl Phys, 55,145(1984) A D CDTE-0016a ETCH acid, dilute TIME: 2 min NAME: Nitric removal/polish 30°C Acid, TYPE: TEMP: 100 jjum/min COMPOSITION: RATE: HNO3 x ... x ... H2O DISCUSSION: (111) wafers used in a phase equilibria and properties study. CdTe, used as a Solution general and polishing etch. It leaves a layer of Te and Te-oxides on surfaces that removal CDTE-0016b. be by the solution shown under removed can REF: Phillips Res Rep, #4,361(1969) CDTE-0016b ETCH NAME: TIME: TYPE: Alkali, TEMP: 60°C removal COMPOSITION: x ... 10%NaOH Na2S2O4 ... x ... H2O x DISCUSSION: (111) wafers CdTe, in a properties study. Solution used to remove Te and Te- used oxides remaining as surface films on wafers after etch polishing in nitric acid. See CDTE- etchants. 0016a. Tellurium section for additional see Also REF: Ibid. CDTE-0017h: Ibid. CdTe, (111) wafers. Solution mixture was: 10% NaOH:x NajSO^ used at RT with Rate: agitation. a bright surface. Produced 1—2 jim/min. See CDTE-0017a. © 1991 by CRC Press LLC

250 237 CDTE-0017a NAME: Sodium TIME: ETCH hydroxide polish TYPE: TEMP: Alkali, RT p,m/min 1.6 RATE: COMPOSITION: ... 50%NaOH x DISCUSSION: wafers used in an etching reaction and rate CdTe, Solution produced (111) experiment. bright In this work, HC1 and H2SO4 surface. RT showed no removal. Agitate solution a at etching. Rate determined by weight loss and should during used as a guide. be REF: P & Milnes, A G — J Electrochem Soc, 128,924(1981) Gaugash, CDTE-0017b ETCH BRM TIME: NAME: TYPE: Halogen, preferential TEMP: RT RATE: 2.2 jim/min COMPOSITION: ...0.5%Br2 x mg ... AgNO3 10 ... MeOH x DISCUSSION: reaction wafers CdTe, in an etch (111) and rate experiment. Solution was medium used red in color and produced pits on (111) surfaces. Was also used as a p-n junction etch. See CDTE-0017a for discussion. further Ibid. REF: CDTE-0017c Nitric TIME: ETCH acid NAME: burn TYPE: Acid, TEMP: RATE: 3.5 jim/min COMPOSITION: ... x cone. HNO3 DISCUSSION: on (111) Solution left a dark CdTe, wafers. surface that could be removed precipitate easily by light mechanical rubbing. See CDTE-0017a for additional discussion. REF: Ibid. CDTE-0017i ETCH TIME: NAME: TYPE: Acid, polish TEMP: RT COMPOSITION: 8 jim/min RATE: 1 ... HC1 50 ... HNO3 18 ... H2SO4 10 HAc ... DISCUSSION: CdTe, (111) wafers used in an etch and rate experiment. Solution produced polished surfaces. See CDTE-0017a. REF: Ibid. © 1991 by CRC Press LLC

251 238 CRC of Metal Etchants Handbook CDTE-0017J ETCH NAME: TIME: preferential TYPE: TEMP: Acid, RT fim/min 60 COMPOSITION: RATE: ... 45% HF 2 ... 1 HNO3 HAc ... 1 DISCUSSION: wafers. Solution used CdTe, agitation and produced pits. See CDTE-0017a (111) with additional discussion. for REF: Ibid. CDTE-0018a BRM TIME: NAME: ETCH polish TEMP: TYPE: Halogen, COMPOSITION: ... Br2 1 20 ... MeOH DISCUSSION: CdTe, used for fabrication of CdTe:HgTe heterojunctions. Solution used (100) wafers CdTe surfaces. Produces a clean, highly reflective surface. to polish Almasi, GS& Smith, REF: C—JApplPhys, 39,233(1968) A CDTE-0018b NAME: regia, dilute TIME: ETCH Aqua TYPE: Acid, polish TEMP: COMPOSITION: ... HC1 3 1 ... HNO3 1 ... HAc DISCUSSION: CdTe, (111) wafers used to growth CdTe:HgTe heteroj unctions. Solution may leave a black smudge surface, but it does not affect device performance. on Ibid. REF: CDTE-0019 TIME: ETCH NAME: Acid, structure TEMP: TYPE: COMPOSITION: 1 ...HF ... H2O2 2 2...H2O DISCUSSION: (111) wafers cut from CdTe, ingot grown by the Vertical Bridgman (VB) technique. an Specimens cleaned in the following sequence: were Br2:MeOH, RT, 3 min to etch 13% remove work damage, and DI water rinse. EAg-1 etch (CDTE-0006b) used to develop etch by pits surfaces. Substructure was developed (lll)Cd the solution shown. This structure on was cellular due to subgrains from supercooling (?), or from high temperature stress (?) during Slow ingot growth will reduce such structure. growth. REF: Oda, O et al — J Cryst Growth, 71,273(1985) © 1991 by CRC Press LLC

252 239 CDTE-0022 NAME: Isopropyl TIME: ETCH alcohol cleaning TYPE: TEMP: Alcohol, RT COMPOSITION: C2H7OH(ISO, ... IPA) x DISCUSSION: single crystal ingot by CdTe, (CZ) method is difficult due to growth as Czochralski low angle grain boundary development. At less than twinning ingot is poly-CdTe. and 50°C, 50—150°C single crystal, but some (122) directional defects. CdTe is iso- Between good by with thin films grown on InSb CdTe MBE showed high perfection of morphous InSb. Clean surfaces with alcohol as shown. (Note: MBE = films. beam epitaxy.) molecular REF: R F C et al — Appl Phys Lett, 39,954(1981) Farrow, Yellin, N al — J Electron Mater, 14,85(1985) CDTE-0023: et Vertical growth. poly-CdTe ingot grown by ingot Unseeded Vapor Growth CdTe Initial Place poly-ingot in closed quartz ampoule under excess Te/Cd vapor (VUVG). Vapor for Transport conversion to single crystal. (VT) CDTE-0024a ETCH TIME: NAME: TYPE: Electrolytic, oxidation TEMP: ANODE: CdTe COMPOSITION: 1WKOH CATHODE. x... ... MeOH POWER: x mA/cm2 1 + ... light DISCUSSION: CdTe, (111) and other orientations. Wafers used in a study of anodic oxidation. After etch cleaning in H2SO4:K2Cr2O7, evaporate gold on wafer back prior to anodic wafers Voltage shown evaporate nickel as for gated FET type devices. Then oxidation, above. with a potential drop across wafer. anneal Talasek, R T & Syooaios, A J — J Electrochem Soc, 132,887(1985) REF: CDTE-0024a: CdTe, wafers, and other orientations, used in a study of anodic oxidation. (111) MERCURIC ETCHANTS CADMIUM TELLURIDE CDHT-0001 ETCH TIME: NAME: Acid, polish TEMP: TYPE: COMPOSITION: 1 ... HC1 6... HNO3 DISCUSSION: CdTe:HgTe specimens. Solution used as a polish etch on this material. After etching, rinse in lHChlMeOH. — Gatos, & Lavine, M C C Prog Semicond, 9,1(1965) REF: H Agajanian, AH — CDHT-0002: State Technol, 16,73(1973) Solid Cd,_xHgxTe Reference has additional specimens. solutions for this compound. etch CDHT-0003: Agajanian, AH — Solid State Technol, 18,61(1975) Cdi_xHgxTe Reference for additional etch solutions for this material. specimens. CDHT-0004: Agajanian, AH — Solid State Technol, 20,36(1977) Cdt.xHgxTe specimens. Reference for additional etch solutions for this material. © 1991 by CRC Press LLC

253 240 CRC of Metal Etchants Handbook PROPERTIES PHYSICAL OF CALCIUM, Ca Classification metal Alkaline Atomic number 20 Atomic weight 40.08 (°C) Melting point 845 Boiling point (°C) 1420 (1487) (g/cm3) Density 1.55 Thermal conductance (cal/sec)(cm2)(°C/cm) 0.3 heat 25°C Specific (cal/g) 0.149 (cal/g) fusion of heat Latent 52 (cal/g) vaporization of Heat 1000 volume (W/D) Atomic 29.9 energy (K-cal/g-mole) ionization 1st 141 ionization 1st (eV) potential 6.11 (eV) work Electron function 2.706 Electronegativity (Pauling's) 1.0 Covalent radius (angstroms) 1.74 Ionic (angstroms) radius (Ca+2) 0.99 Linear of thermal expansion coefficient 22.3 (xl0-6cm/cm/°C)20°C ~*) Electrical conductance (micro-ohms 0.218 cm) Electrical resistivity (x 10~6 ohms 0°C 3.91 106) Modulus of elasticity (psi x 3.2—3.8 (psi) strength Tensile 6900 section (barns) Cross 0.43 Vapor pressure (°C) 1207 — scratch) (Mohs Hardness 1.5—2 kfg/mm2) — (Brinnel 16—18 (isometric Crystal normal) structure — (100) cube, fee (solid) Color Silver-white (cubic) Cleavage (001) CALCIUM, Ca but not as a free element General: nature occur is widely distributed in carbonate Does in — calcite, CaCO3 and aragonite, CaCO3 as the primary single minerals — in massive crystals form chalk, limestone, dolomite (containing magnesium and calcium), marl, sea shells. as CaSO4.2H2O a sulfate, the minerals gypsum, calcium and the dehydrated anhydrite, As CaSO4. The sulfates are known as Plaster of Paris. The name — calcium — is from Latin calx = hence the name for limestone. Both calcium carbonate and calcium hydroxide lime, Calcium in waters and produce "hard" water. ground oxide, CaO, is "quick occur natural and, as slack lime, Ca(OH)2. Lime as mortar was in use by the Romans in the 1st lime" A.D. fresco a wall century has been discovered in Asia Minor dated to about 1600 B.C. and CaF2, phosphate the Huorite, apatite are of importance. and in is fifth Calcium in abundance and, the addition to its occurrence in inorganic element minerals, is found in leaves, teeth, and bones, such that it is an essential ingredient for mammillary growth. calcium and phosphorus are supplied by milk. Both calcium exposed silver-white in color although it turns yellowish when Metallic to is heated as air with nitrogen. It will burn if it in air, is electropositive like alkali metals, reacts and is used as a deoxidizer in metal alloys and steel. In its oxide, sulfate, carbonate, and in fluoride it is used as mortar, cement, plaster, as a flux in glass and metals, forms paper agriculture making, refining, water purification, and in sugar to neutralize acid soil. When © 1991 by CRC Press LLC

254 241 limestone pressurized and heated, the natural metamorphic process, it becomes marble. is materials have used since ancient times for construction, objets d'art, or utensils, Both been plates there drinking cups. Alabaster is a pure white form of marble, and as are such and black, and that marbles color banded. The limestone called onyx is limestones and both are are many other limestone forms and names. there natural calcium, derived from the carbonates, and organic calcium, derived from Both are form medicinally in pill seashells, for human consumption. As a dry powder both used paste, and available in the chemical laboratory and, when mixed as a are calcium magnesium be applied to the skin to neutralize acid burns. can Application: Metallic calcium is not used Technical Solid State processing to any in extent, it may be an element in tungstates, molybdates, and garnets though are artificially that fabricated. It has been grown as the nitride, CajNg. Etching: Deliquesces in water to the hydroxide. Soluble in acids; slowly soluble in alcohols. CALCIUM ETCHANTS CA-OOOla ETCH acid TIME: NAME: Hydrochloric removal TYPE: TEMP: Acid, RT COMPOSITION: ... cone. x HC1, DISCUSSION: Solution used Ca the general study of the metal. Process and hold under specimens. in to prevent reaction with air (nitrogen). argon Foster, REF: & Alyea, H N — An Introduction to General Chemistry, 3rd ed, D Van W New 1947, Nostrand, 395 York, CA-OOOlb ETCH Air TIME: NAME: Gas, reactive TEMP: TYPE: to hot RT COMPOSITION: x ... air DISCUSSION: Ca, as metal specimens. Reacted in air to develop a yellowish, stable coating of pure oxynitride, for See CAN-0001 the the pure nitride formation. Ca2N3Ox. Ibid. REF: CA-OOOlc NAME: Water TIME: ETCH TYPE: reactive TEMP: RT to hot Acid, COMPOSITION: x ... H2O DISCUSSION: produce Reacted in water Ca metal. the hydroxide, Ca(OH)2, called "slacklime". to When "lime" (CaO) is reacted with water, it is called "quicklime". Both limes, mixed with gypsum and clay, are cement. REF: Ibid. © 1991 by CRC Press LLC

255 242 CRC of Metal Etchants Handbook CA-OOOld ETCH TIME: NAME: Sulfur reactive TYPE: TEMP: Metal, Hot COMPOSITION: S x... DISCUSSION: and mixed with sulfur to form anhydrite, then water added to form metal. Ca Powdered plaster of CaSO4.nH2O. It is still used for Paris, body casts; major use Plaster gypsum as construction as general plaster, plaster wallboard; for holding small stones in mineral is in as cutting; d'art. shaped objets REF: Ibid. PHYSICAL CARBONATE, CaCO3 PROPERTIES CALCIUM OF Classification Carbonate numbers & 8 Atomic 20, 6 100 weight Atomic (°C) 1339 Melting point point (°C) Boiling 898.6 1.71 (g/cm3) Density (n = ) w = 1.65849; Refractive = 1.48625 index e (Mohs — scratch) 3 Hardness structure (hexagonal — rhombohedral) Crystal rhomb (1011) Color Clear/white (solid) (rhomb — (1011) Cleavage perfect) CaCO3 CALCIUM CARBONATE, aragonite two natural minerals — There and primary — both rep are General: calcite a group of minerals with the resentative formula MCO3. The Calcite Group is of general in with M = Ca, Mg, Fe, structure Zn, and Co. The Aragonite hexagonal-rhombohedral Mn, is orthorhombic Group structure with M = Ca, Ba, Sr, and Pb. Within each group the in minerals isomorphous, giving rise to a wide variety of subspecies. are is carbonates more stable of these two calcium Calcite and is discussed here. Common the rhombic Iceland It has perfect (1011) Spar. cleavage, though twinning is common name: and forms a bi-crystal with c(0001) as a common vertical axial plane. When pure, it is transparent and although it may have pale shades of red, green, blue, yellow, etc. As clear, transparent, flat-faced the single crystal acts as a lens, but is more common in rhomb, a stalagmites, (chalk) limestone, or as stalactites, or and nodular forms, such masses compact are found in caves or around geysers. It is one of die most widely as minerals distributed even a small fraction in volcanic rocks ("snowflake" obsidian — natural glass containing as of sedimentary Common and widespread in "flowers" rocks of varied character calcite). of as cement — to massive formations — chalk and limestone. Under pressure and vein heat, metamorphic compaction, it is marble. It is deposited from lime-bearing waters, the carbonates, vs. waters that form the silicates. Also found as calc-sinter or siliceous-bearing around derivation). springs and as calcareous rock from sea life shells (organic travertine hot temperature 90°C from about Formation (springs/caves) to 800—900°C (volcanic). varies the carbonates wide industrial use in Calcium manufacture of mortars and cements; have as a building and ornamental material; as a flux in metallurgy; as blackboard "chalk" in paint glass fertilizers, animal feed; and in in as whitewash. For human con (soda-lime); sumption it is a de-acidifier as aspirin, Maalox and, in paste form, used to neutralize acids — burns magnesia — the mineral magnesite, MgCO3 (also a member of the Calcite Group). © 1991 by CRC Press LLC

256 243 As single crystal, due to its high birefringence, it is used as a polarizing prism in microscopes a should be carefully to prevent scratch damage. and handled and No in Solid State processing use fabrication though Application: Technical current under evaluation as a cleaved substrate for thin film metal evaporation and semiconductor it is morphology studies, similar to the present uses of sodium chlorides, NaCl. epitaxy growth is constituent a — soda-lime — this glass in the primary type used to fabricate As glass resist glass masks. As a constituent in alloy fluxes, it is used in some photo applications solder for assemblies. Both calcium and magnesium are kept in chemical laboratories for device of acid as already mentioned. neutralization burns for crystals single extensively studied have their optical characteristics. Natural been Soluble in HC1 with effervescence, other acids, and slightly soluble in water. Etching: CARBONATE ETCHANTS CALCIUM CAC-0001 ETCH acid TIME: 5—10 sec NAME: Hydrochloric polish TEMP: RT TYPE: Acid, COMPOSITION: ... x cone. HC1, DISCUSSION: "Iceland (1011) substrates from CaCO3 cleaved Spar". Specimens were used natural in a study of surface energies of calcite. After cleaving, surfaces were etch polished and rinsed in Solution shown used as a rapid polish with effervescence of the material. alcohol. Gilman, J — J Appl Phys, 31,2208(1960) REF: J CAC-0002 NAME: acid, dilute TIME: Variable ETCH Hydrochloric polish TEMP: TYPE: Acid, RT COMPOSITION: 1 ... HC1 10 ... H2O DISCUSSION: as polarizing prisms. Solution used to lap/polish remove scratches from CaCO3, micro scope using a felt pad. Also to clean marble surfaces. prisms Walker, — personal application, 1952 REF: P Gross, K A — Phil Mag, 12,801(1965) CAC-0005: study CaCO3, wafers used in an energy cleaved of deformed and annealed natural (1011) calcite using X-ray techniques. A 10% HC1 solution was used to polish surfaces. CAC-0003a ETCH Nitric acid, dilute TIME: 90 sec NAME: Acid, TEMP: RT TYPE: dislocation COMPOSITION: 1 ... HNO3 x...H2O _ DISCUSSION: r( 1011) cleaved wafers and other CaCO3, A study of dislocations and plastic orientations. deformation evaluating a number of acids. Alkalies are too slow at room temperature and CO2 mineral an excessive rate of attack with show evolution. Weak acids with an inert acids carrying liquid are best. If a dislocation moves away from the original etch pit due to stress, © 1991 by CRC Press LLC

257 244 CRC of Metal Etchants Handbook pit becomes and, with further etching, a sharp-bottomed pit will appear the flat-bottomed new pictures.) point. (Note: A very fine article with excellent the at dislocation R Gilman, & Keith, J J — Acta Metall, 9,1(1961) E REF: CAC-0003b NAME: Formic acid TIME: 15 sec ETCH Acid, dislocation TYPE: RT TEMP: COMPOSITION: x...HCOOH(90%) DISCUSSION: _ cleaved wafers. CaCO3, CAC-0003a. r(1011) See REF: Ibid. Keith, R E & Gliman, J J — Acta Metall, 8,1(1960) CAC-0004: Formic r(1011) wafers used in a dislocation pit etch development study. cleaved CaCO3, acid gave best results with only one type pit. CAC-0003b.l ETCH NAME: Formic acid, dilute TIME: 5 sec TYPE: Acid, TEMP: RT dislocation COMPOSITION: 1 ...HCOOH(90%) H2O 1 ... _ DISCUSSION: cleaved wafers. CaCO3, CAC-0003a. r(1011) See Ibid. REF: CAC-0003b.2 NAME: Formic acid, dilute TIME: ETCH sec 1V2 TYPE: dislocation TEMP: RT Acid, COMPOSITION: 1 HCOOH(90%) ... ... H2O 10 DISCUSSION: r(10Tl) cleaved wafers. See CAC-0333a. CaCO3, REF: Ibid. CAC-OOO3b.3 ETCH Formic acid, dilute TIME: 45 sec NAME: Acid, dislocation TEMP: RT TYPE: COMPOSITION: ...HCOOH(90%) 1 1 ...EOH DISCUSSION: CaCO3, r(1011) cleaved wafers. See CAC-0003a. REF: Ibid. CAC-0003b.4 ETCH NAME: Formic dilute TIME: 90 sec acid, TYPE: Acid, dislocation TEMP: RT COMPOSITION: 1 ...HCOOH(90%) 1 ... glycerin © 1991 by CRC Press LLC

258 245 DISCUSSION: r(10ll) cleaved See CAC-0003a. CaCO3, wafers. Ibid. REF: CAC-0003c.l acetic acid NAME: 360 sec ETCH Glacial TIME: dislocation TEMP: RT TYPE: Acid, COMPOSITION: ... x CH3COOH(HAc) DISCUSSION: r(1011) cleaved wafers. CaCO3, CAC-0003a. See REF: Ibid. CAC-0003c.2 NAME: Acetic acid, dilute TIME: ETCH sec 75 TYPE: dislocation TEMP: RT Acid, COMPOSITION: 1 ...CH3COOH(HAc) H2O 1 ... DISCUSSION: CaCO3, cleaved wafers. See CAC-0003a. r(1011) Ibid. REF: CAC-OOO3C.3 ETCH Acetic acid, dilute TIME: 30 sec NAME: TYPE: dislocation TEMP: RT Acid, COMPOSITION: 1 ... CH3COOH(HAc) 10 ... H2O DISCUSSION: _ r(1011) wafers. See CAC-0003a. CaCO3, cleaved REF: Ibid. CAC-0003d NAME: Propionic acid TIME: ETCH min 6 TYPE: cleaning TEMP: RT Acid, COMPOSITION: ... CH3CH2COOH x DISCUSSION: _ CaCO3, r(1011) cleaved wafers. Solution showed no attack in 6 min, but did give some cleaning action. CAC-0003a. See Ibid. REF: CAC-0003d.l NAME: Propionic ETCH dilute TIME: 120 sec acid, TYPE: Acid, dislocation TEMP: RT COMPOSITION. ... CH3CH2COOH 1 1 ... H2O DISCUSSION: CaCO3, r(10Tl) cleaved wafers. See CAC-0003a. REF: Ibid. © 1991 by CRC Press LLC

259 246 CRC of Metal Etcnants Handbook CAC-0003e ETCH acid TIME: 15 sec NAME: Lactic dislocation TEMP: TYPE: Acid, RT COMPOSITION: ... (85%) x CH3CHOHCOOH DISCUSSION: _ cleaved wafers. CAC-0003a. CaCO3, r(1011) Ibid. REF: CAC-0003f Maleic TIME: 10 sec ETCH acid NAME: dislocation TEMP: RT TYPE: Acid, COMPOSITION: ... HOOCCH:CHCOOH, sat. sol. x ... H2O x _ DISCUSSION: cleaved wafers. See CAC-0003a. CaCO3, r(1011) Ibid. REF: CAC-0003g NAME: Tartaric acid TIME: 10 sec ETCH Acid, dislocation TEMP: RT TYPE: COMPOSITION: x HOOC(CHOH)2COOH, sat. sol. ... ... x H2O DISCUSSION: r(1011) cleaved wafers. CaCO3, dislocations with a fresh solution. Used Developed after 2 months, there was no reaction. See CAC-0003a. REF: Ibid. CAC-0003h ETCH TIME: NAME: EDTA cleaning TEMP: Acid, TYPE: RT COMPOSITION: x ... (HOOC-CH^NCHjCHj DISCUSSION: _ (1011) cleaved wafers. There CaCO3, no reaction with this solution. Also no pit was forming reaction with oxalic acid. See CAC-0003a. REF: Ibid. CAC-0014: jCeith, R E & Gilman, J J — Acta Metall, 8,1(1960) Formic CaCO3, wafers used in a dislocation pit etch development study. cleaved (1011) acid gave best results producing only one type pit. PHYSICAL PROPERTIES OF CALCIUM FLUORIDE, CaF2 Classification Fluoride Atomic numbers 20 & 9 Atomic weight 76.08 Melting point (°C) 1360 Boiling point (°C) Density (g/cm3) 3.18 (3.01—3.25) © 1991 by CRC Press LLC

260 247 Refractive (n =) 1.4339 index (Mohs — 4 Hardness scratch) kgf (Knoop mm"2) — 163 1.06 radius Ionic (angstroms) cm"2) -273°C 543 free (ergs Surface energy (111) -195°C 450(111) — Crystal (100) cube structure (isometric normal) Yellow-green/variable Color (solid) 111) Cleavage o( (octahedral-distinct) FLUORIDE, CaF2 CALCIUM as the mineral fluorite, is fairly General: and found as a vein deposit, Occurs common, or silver, zinc, etc. Like diamond, it is one of the few minerals with distinctive alone, with of even it is in the normal class though the isometric system, where most (111) cleavage, shown cubic (001) cleavage. It is noted for its wide range of colors materials can vary that within crystal, or be banded. Colors can be altered by heat, X-rays, UV light, pressure, a and may blue fluorescence. etc., show of in as a solder flux was the discovery use fluorine, and is the major ore for It before used in the making of hydrogen fluoride (HF), e.g., hydrofluoric acid. Fluorite as fluorine, powder major a use in making opalescent glass and enamel, such as for cookware. It has used colors, jewelry making for its is even though the mineral is relatively soft. in in Application: is no direct use There Solid State device fabrication, although Technical it is under evaluation as a surface coating for its optical properties. It is used as a microscope prism for high birefringence, and has applications as a filter element or as lenses. There its still use the powdered material as a solder flux in package fabrication. is of crystal been studied as the natural single has due to its transparency for Fluorite widely the physical, electrical, and electronic effects of various treatments, such as observing X- ray, etc., already mentioned in the proceeding General section. pressure, Slow salts. acids, water — easily in ammonium Etching: in FLUORIDE CALCIUM ETCHANTS CAF-0001 NAME: Water TIME: ETCH removal TEMP: Acid, TYPE: COMPOSITION: x ... H2O DISCUSSION: CaF2, (100) thin films deposited on GaAs, (100) substrates. After deposition, wafers were photolithographically for an open square pattern, then E-beam annealed. processed annealing, processed was used to wash away the CaF2 thin films. Also After SrF2 water with HC1 (SRF-0001) used to wash-away the strontium compound. dilute REF: P W — J Vac Sci Technol, B2,202(1984) Sullivan, CAF-0004: Tu, C W — J Vac Sci Technol, B2,24(1984) InP CaF2, (110) thin films deposited on and substrates of similar orientation. Thin (100) films were grown by MBE, including SrF2, BF2, and BaxSr,.xF2 co-deposited from the two for compounds. used to wash away CaF2; dilute HC1 Water SrF2; HF for BaF2 and the mixed compound. © 1991 by CRC Press LLC

261 248 CRC of Metal Etchants Handbook CAF-0002 ETCH acid TIME: NAME: Sulfamic dislocation TYPE: TEMP: Acid, COMPOSITION: ...H2NSO3H 6g 100 H2O ml... DISCUSSION: wafers used in CaF2, dislocation study. Specimens were studied as- (111) cleaved a further surface conditioning prior to preferential etching in cleaved solution without the shown. R P — J Appl Phys, 34,419(1964) REF: Steijn, ~~~ CAF-0003 ETCH alcohol TIME: 5 min Ethyl NAME: Alcohol, TEMP: RT TYPE: cleaning COMPOSITION: x ... EOH DISCUSSION: (100) cleaved wafers. Both CaF2, fluorite and artificially grown material were natural used an X-ray reflection study. Specimens prepared by immersion in alcohol with light in on surfaces a cotton swab during the cleaning period. using scrubbing V P — Acta Crystallogr, 11,848(1958) Barton, REF: Walker, P et al — personal application, 1968 CAF-0008: natural CaF2, (111) crystals prepared for light irradiation study. Specimens octahedral, rpm on polished metallographic wheel at high a with a pellon-type pad soaked with Buehler alcohol. Intense light of different frequencies colors used to develop internal defect. Similar light frequency evaluated on alpha-quartz radio frequency blanks. Artificial material effects thin as wash-cleaned in alcohols prior to metallization with Au:Cr was fabricated lenses films. CAF-0005 ~~~~ ETCH NAME: Nitric acid TIME: Acid, preferential TEMP: TYPE: COMPOSITION: x...0.2/VHNO3 DISCUSSION: (111) cleaved wafers used in a study of cleavage and dislocation pits as CaF2, compared to Solution shown developed trigon pits diamonds. those on natural diamond faces, but like no etch would artificially develop similar pits on diamond. The CaF2 was difficult to cleave on (111). Patel, R et al — Phil Mag, 9,951(1964) REF: A Amelinck, S et al — Physica, 23,270(1975) CAF-0007: etch (111) wafers used in a study of oriented pits. Pits can occurs on natural CaF2, fluorite faces under normal growth conditions, and can appear on both natural and artificially grown cleaved surfaces without etching. material CAF-0006a ETCH NAME: Ammonia TIME: Seconds TYPE: Base, polish TEMP: RT COMPOSITION: x ... NH3 © 1991 by CRC Press LLC

262 249 DISCUSSION: as natural crystals as octahedron, (111) solid forms. Solution used to clean CaF2 fluorite sections, (111) bulk crystals. As (111) cleaved of solution used to polish polish and faces for microscope study. thin specimens P mineralogy Walker, study, 1952 REF: — CAF-0006b NAME: hydroxide TIME: Seconds ETCH Ammonium cleaning TYPE: RT Base, TEMP: COMPOSITION: x ... NH4OH DISCUSSION: specimens CaF2 artificially grown and cut lenses. Specimen surfaces were lightly as polish by hand lap on a hard felt surface saturated with the solution prior to vacuum cleaned with and thin films. Water wash metallization nitrogen blow dry after cleaning. Au/Cr Walker, — REF: personal application, 1975 P CAF-0009 ETCH Sulfuric acid TIME: NAME: Acid, preferential TEMP: TYPE: COMPOSITION: x ... H2SO4, cone. DISCUSSION: CaF2, wafers cleaved from natural fluorite crystals. Solution developed triangular (111) and pits correspondence between the opposed positive 1:1 negative (111) faces of etch with wafers. Pandya, N S & Pandya, J K — REF: Sci, 27,437(1958) Curr CALCIUM FLUORIDE ETCHANTS SILICON CASF-0001 ETCH TIME: NAME: Acid, removal TEMP: TYPE: COMPOSITION: x... HF x ... HNO3 DISCUSSION: CaSiF2 single crystals were used in evaluating cohesive energy features of tetrahedral semiconductors. Forty were studied. materials Solids, Aresti, et al — REF: Phys Chem A 45,361(1984) J CALCIUM TIN FLUORIDE ETCHANTS CATF-0001 ETCH NAME: Ammonium hydroxide TIME: TYPE: removal/cleaning TEMP: Base, COMPOSITION: x ... NH4OH DISCUSSION: CaSnF2 deposited as a thin film in forming a semiconductor-dielectric-semiconductor © 1991 by CRC Press LLC

263 250 CRC of Metal Etchants Handbook structure. Compound to as a spinel, deposited as a Ge/CaSnF2 multifilm (SIS) referred silicon (111) structure on substrates. Sci W al G J Vac et Technol, B2,212(1984) Tu, REF: — OF CALCIUM MOLYBDATE, CaMoO4 PHYSICAL PROPERTIES Classification Oxide Atomic 42, & 8 numbers 20, 200 weight Atomic point (°C) 1200 Melting (°C) Boiling point 4.35 Density (g/cm3) Refractive index (n =) 1.974—1.984 (Mohs — scratch) 3—3.5 Hardness structure Crystal — normal) (111) pyramid (tetragonal (solid) Yellowish Color (001) Cleavage (basal) MOLYBDATE, CaMo04 CALCIUM not occur as General: compound, but the mineral powellite, Ca(W,Mo)O4 Does a pure found as a mixed element compound with about is CaWO4. The pure molybdate has 10% been to as powellite in the literature. referred molybdenite, pure The be made by roasting compound MoS2 with coke and lime, can the material then used in making other molybdenum compounds. The pure metal is used in fabricating high steels, and other compounds in the dyeing of silk or other fabrics. speed have Application: and artificial single crystals natural been studied for Technical Both morphology; electronic and electrical properties; and crystallographic structure changes general pressure and temperature. with Soluble acids. Etching: in CALCIUM MOLYBDATE ETCHANTS CAMO-0001 NAME: Pressure ETCH TIME: TYPE: Pressure, alternation TEMP: COMPOSITION: x ... pressure DISCUSSION: CaMoO4 as single crystals were studied in a high pressure chemistry test of molybdnates and tungstates about 56 Pa pressure. Other materials evaluated were CaW04, PbWO4, at a and etch shown, but H3PO4 is No general removal solution on tungstates. CdMoO4. REF: Hazen, R M et al — J Phys Chem Solids, 46,253(1985) PHYSICAL OF CALCIUM NITRIDE, Ca2N3 PROPERTIES Classification Nitride Atomic numbers 20 & 7 Atomic 148.26 weight Melting point (°C) 900 Boiling point (°C) © 1991 by CRC Press LLC

264 251 Density 2.63 (g/cm3) (Mohs — 5—6 Hardness scratch) (isometric Crystal alpha (100) cube — structure normal) beta prism normal) (tetragonal (110) — Color (solid) Brown/black (001) Cleavage (cubic/basal) CALCIUM NITRIDE, Ca2N3 not occur as a natural compound even though there General: over 2S0 calcium Does are as sulfides, carbonates, silicates, etc. (Nitrogen alone does not form pure minerals fluorides, compounds.) nitride at no application in industry The present, though several calcium compounds has nitride of importance, such as calcite, CaCO3. are Application: Technical used in Solid State processing at present, though it has been Not substrates as crystal thin film on calcium single in material evaluation. There are grown a applications as a dielectric for its optical properties, or as a surface protective possible similar of those coating other nitride compounds. to Soluble dilute acids. Etching: in CALCIUM NITRIDE ETCHANTS CAN-0001 NAME: Nitric acid TIME: ETCH Acid, TYPE; TEMP: RT removal COMPOSITION: x HNO3 ... x... H2O DISCUSSION: Ca2N3 thin films deposited on calcium substrates in a study of the use of high purity nitrogen to Deposited at 600°C, nitride is tetragonal — at 675°C is contamination. reduce (MGN-0001), Also with magnesium nitride worked and references work structure. cubic with lithium nitride (LIN-0001). If O2 or air is present during deposition in the N2 done the white CaO or MgO appear in of otherwise black nitride films. spots atmosphere, Aubry, J & Streiff, R — J Electrochem Soc, 118,650(1971) REF: CaWO4 TUNGSTATE, OF CALCIUM PHYSICAL PROPERTIES Tungstate Classification 8 & 20, 74, Atomic numbers 289.92 Atomic weight >1200 Melting point (°C) point Boiling (°C) 6.06(5.9—6.1) R Density (g/cm3) 1.918—1.934 =) (n index Refractive (111) pyramid — pyramidal) Crystal (tetragonal structure Yellow/brownish (solid) Color distinct) (pyramidal Cleavage — P(lll) CALCIUM TUNGSTATE, CaWO4 General: Occurs in nature as the mineral scheelite, CaWO4, which is a major ore of or tungsten. mineral forms under pneumatolytic The hydrothermal conditions in pegamatites, © 1991 by CRC Press LLC

265 252 CRC of Metal Etchants Handbook as ore in association with granites. It is commonly yellow to brown in color, and or veins salt bright a black light. Fused with under of phosphorus it melts a yellow-white fluoresces glass at about 1200°C with a to blue color. a fine it a major ore of tungsten, and the is light is used during grinding to Industrially black complete segregation of the gangue material. Also insure as a fine blue pigment in used glass enamels. and at this Application: in Solid State processing application time, though it Technical No been grown and studied as a single crystal for defects and general morphology, to include has possibly frequency applications. Hot and mixed acids. Etching: H3PO4, CALCIUM TUNGSTATE ETCHANTS CAW-OOOla NAME: Phosphoric ETCH TIME: acid TYPE: removal TEMP: 250°C Acid, COMPOSITION: x ... H3PO4 DISCUSSION: CaWO4, (001) wafers. Ingots were grown with (100) orientation and wafers were cut as (001) orientation. Solution used to remove work damage after mechanical lap and basal polish. REF: —Phil Mag, 10,911(1964) Lockayne, B CAW-OOOlb NAME: ETCH TIME: regia Aqua Acid, TEMP: 55°C TYPE: preferential COMPOSITION: ... HC1 3 ... 1 HNO3 DISCUSSION: (001) wafers used in a study of deformation and slip. Solution CaW04, to develop used slip and dislocation etch pits. patterns Ibid. REF: CAW-0002: Lockayne, B—BrJApplPhys, 16,423(1965) CaW04, (001) wafers. Ingots were grown with (100) orientation, and and cut (001) basal as of low-angle grain boundaries. After mechanical lap, solution used to etch free polish and dislocation distributions. develop ~~~ CAW-0003a ETCH TIME: NAME: TYPE: Acid, polish TEMP: 200°C COMPOSITION: RATE: 0.009—0.06 ^m/sec 3 H3PO4 ... 1 ... CrO3, sat. sol. DISCUSSION: CaWO4, (100) wafers. Solution used to etch polish specimens in a study of dislocations. REF: Ibid. © 1991 by CRC Press LLC

266 253 CAW-0003b NAME: TIME: min ETCH 2—25 dislocation TYPE: TEMP: Acid, RT |xm/sec .003 COMPOSITION: RATE: ... HF 1 sat. sol. ... 2 CrO3, DISCUSSION: wafers. Solution used to develop dislocation pits and pits showed a CaWO4, (001) 1:1 from to negative wafer surfaces. correspondence positive Ibid. REF: CAW-0004 Phosphoric acid TIME: NAME: ETCH polish TEMP: Hot TYPE: Acid, COMPOSITION: x H3PO4, cone. ... DISCUSSION: CaWO4, crystal specimens used in a study of Raman frequency shifts and tem single perature Other tungstates studied: SrWO4 and BaWO4. dependence. Chem Degreniers, al — J Phys et Solids, 45,1105(1984) REF: S CAW-0005a NAME: Phosphoric acid TIME: 15 min ETCH Acid, TEMP: TYPE: 300°C polish COMPOSITION: x H3PO4 ... DISCUSSION: single crystal specimens used CaWO4, a study of plastic deformation. Solution used in to remove residual lap damage and polish, though it can be rough if etching is over 15 min. Use a basket to hold specimens, place in acid at RT, then bring up to 300°C boiling point Pt reduce above 150°C before removal to boiling water quench. If quenched — 150°C, to surface specimen cracks. Arbel, A & Stokes, R J — J Appl Phys, REF: 36,1460(1965) CAW-0005b NAME: 15—20 min ETCH TIME: TYPE: dislocation TEMP: 100°C Acid, COMPOSITION: 1 ... H3PO4 1 ... sat. sol. NH4C1, ... 2 H2O DISCUSSION: single crystal specimens used CaWO4, a study of plastic deformation. Solution used in to develop defects after material stressing. Place specimen in solution at RT, raise to 100°C at for then quench directly into water period, RT. etching REF: Ibid. CAW-0006 ETCH NAME: TIME: TYPE: Pressure, alteration TEMP: COMPOSITION: x ... pressure © 1991 by CRC Press LLC

267 254 CRC of Metal Etchants Handbook DISCUSSION: CaWO4 used in a high pressure chemistry test of materials above 56 Pa single crystals CaWO4, tungstates were studied: PbWO4, molybdates PbMO4, and Both pressure. and noted as the mineral scheelite. CdMo4. CaWO4 R J et al — Hazen, Phys Chem Solids, 46,253(1985) REF: M OF Cf PROPERTIES PHYSICAL CALIFORNIUM, Actinide Classification Atomic 98 number Atomic weight 251 point (°C) Melting point (°C) Boiling Density (g/cm3) radius (angstroms) (Cf+3) Ionic 0.98 800 (years) Half-life section (barns) 3000 Cross (g/amp-h) 3.1 Electrochemical equivalents potential (eV) 44.1 Valence electron Hardness (Mohs — scratch) 3—4 structure (isometric — normal) (100) Crystal cube Color Grey (solid) Green (gas) (cubic) (001) Cleavage CALIFORNIUM, Cf A naturally occurring gas as one General: the radioactive decay series. No use in of industry at the present time. Technical Application: No use in Solid State processing to date. It has been studied in solid form. Soluble in Etching: HC1. ETCHANTS CALIFORNIUM CF-0001 NAME: Hydrochloric acid TIME: ETCH removal TYPE: Acid, TEMP: COMPOSITION: x ... HC1, cone. DISCUSSION: specimens. Solution used to Cf material in a study of the properties of the dissolve the isotope (fermium). 2Fm52 Phys Friedman, M et REF: — A Rev, 101,1472(1956) al CARBIDES, MXC General: There is only one known occurrence of a carbide mineral in nature — the mineral moissanite, found as small green hexagonal platelet in the meteoric iron from CSi, originally Canon — though the material was Arizona produced as artificial carbo Diablo, rundum, SiC. Both carbides and borides are part of the ceramic industry of today, though the ancient pottery" pottery is still referred to as "ceramic industry where silicate glaze (SiO2) with or © 1991 by CRC Press LLC

268 255 without additives for color as enamels have been in use since about 3500 B.C. when mineral Egyptians first soda-lime glass. There are many industrial applications for the developed fire-bricks, temperature as for furnace lining such crucibles, and, when high the ceramics, carbon, for radiation resistant materials used in atomic nuclear equipment con mixed with also called Ceramics *'Cermets". See General discussion under Ce struction. have been chapter, further discussion. this for ramics, Several carbides are Technical as a ceramic in Solid State processing Application: used circuit substrates, in package construction, or as electrical stand-off insulators. As an as discrete active they are designed as resistors and capacitors, or may be co-deposited device, a planar dielectric in a substrate circuit. as type capable SiC, carbide, doped, is a semiconductor when of operating as a Silicon boron above 500°C. Boron nitride and diamond also show semiconducting diode at characteristics elevated temperatures. individual as are not listed, here, as several are of sufficient importance The carbides their both dielectrics that they are under and own listed sections following their ceramics parent metals. See the Material Index for numbers. Borides are as a collective listed heading. Also see oxide, A12O3; silicon dioxide, SiO2; and boron nitride, BN. Many of aluminum compounds are as ceramics or as dielectrics. these used See solutions. compounds for Difficult. Etching: separate OF C PROPERTIES PHYSICAL CARBON, Ceramic Classification number 6 Atomic Atomic 12.01 weight point 3727 (3550) Melting (°C) point (°C) 4830 (4827) Boiling (g/cm3) (2.09—2.23) Density 2.26 Thermal conductance (cal/sec)(cm2)(°C/cm) 0.057 heat (cal/g) 25°C 0.165 Specific Heat of (k-cal/g-atom) 171.7 vaporization volume (W/D) Atomic 5.3 1st ionization energy (K-cal/g-mole) 260 1st ionization potential (eV) 11.264 Electronegativity (Pauling's) 2.5 radius (angstroms) Covalent 0.77 (angstroms) (C+4) radius 0.16 Ionic Coefficient linear expansion 0.6—4.3 of thermal 10~6 cm/cm/°C) 20°C (x x 10~6) 3.0 (K"! Electron function (eV) 4.82 work section Cross 0.0034 (barns) Vapor pressure (°C) 4373 Electricity resistivity (x 10"6 ohms cm) 0°C 1375 Bond dissociation (kJ mol-1) 606 energy energy (kJ mol-1) 713 Cohesive Tensile strength (kgf cm-2 x 10~4) 7.7 10~4)] Thermal coefficient [F(cmK min""2 x endurance 2.04 Relative F match 52 © 1991 by CRC Press LLC

269 256 CRC of Metal Etchants Handbook (Mohs — carbon (hard) 6—7 Hardness scratch) 1—2 graphite, natural mm2) kgf (vitreous) 2200—2859 (Vicker's — — carbon 10—100 pressure — (Scleroscope strike) bounce) (vitreous) (Shore-ball carbon — 120—150 Crystal (0001) plates 6-sided structure (hexagonal — rhombohedral) black Coal (solid/powder) Color perfect) Cleavage (basal — (0001) CARBON, C nature as the mineral graphite, C, (plumbago, black lead). Industrially General: in Occurs be the form is diamond. Carbon can pressure recognized by its extreme carbon, called high feeling, black softness, and metallic luster. The two terms are interchangeable greasy color graphite carbon. It is the "lead" in pencils as it was first thought to be a form of lead — or is with the hexagonal system crystallographically like micas It the prominent basal (Pb). in known is micaceous cleavage, which cleavage more apparent in graphite than in as (0001) contain carbons. monolayer hexagonal planes The the atomic "benzene grown artificially structure with strong binding energy within the monolayer, but weak binding energy ring" monolayers. between natural graphite these benzene-type carbon rings are vertically In directly above other from layer to layer; whereas in carbon the rings are off aligned each many alternate of this structure variation Because types of carbon between set monolayers. be artificially fabricated, often constructed to improve the binding energy materials can monolayers. In at 500°C, grain spacing is 10—20 A, whereas at 2500— between fabrication structure, A Further, with controlled granular spacing. the material can 3000°C, 70—1000 cut parallel or perpendicular to grain orientations, be producing different characteristics. thus In to being mined as natural graphite, carbon is obtained from petroleum, addition and asphalt from coal — anthracite (hard), tar; bituminous (soft); from natural natural and such as methane; and from the burning of vegetation. When partially fired to remove gases, vapor water gaseous impurities, but below the ignition point, it is called "coke", and burners similarly as charcoal. The charcoal processed of ancient times were a hardwoods race among themselves, processing hardwood trees as a coke-type fuel for the metals and glass industries, well as for cooking fires throughout Europe, the Middle East, and Asia. as was being prior to 1350 B.C. (Iron Age) for the smelting of bronze and today Cooking done a processing fuel in the fabrication and is of steels. As lampblack, a near- coke primary powder of or as finely divided carbon oil, down to colloidal structure, it liquid by-product a black pigment for glass, enamels, cement, etc. It also is still the black "lead" in pencils, is term a being the misnomer, as it is graphite or carbon, not lead. "lead" metal addition use as a fuel or additive to its products, carbon parts have many In to uses for its high temperature, and both electrical and heat transfer capabilities. It industrial extremely is to chemical attack and, coupled with its high temperature capability, is inert such used crucible for processing liquid metals, a as in semiconductor ingot growth pots, as as a metal evaporation crucible, or as crucibles in heavy metal processing. For its heat transfer capabilities as a bulk item, it is used as graphite susceptor plates, alone, or SiC and parts, in as heater strips for alloying systems; or disassembly and recovering coated epitaxy rejected parts; as furnace linings and heater rods or furnace tubes, and as boats, flats, of as etc., vehicles for parts in alloy furnaces. holding bulb a it was one As the first light wire filaments — is still so used in special of applications — or wires can be embedded in glass or plastics as a heater grid, and are used gap as wires for spark plugs. As a pair of rods, it is used for spark ignition automotive welding vaporizing a metal surface for or analysis of elements. Also as rods, spectrographic due to its low neutron cross-section, carbons are the damping rods in atomic piles in nuclear pigment, energy As powder, in addition to being a plants. it is used as a dry lubricant like © 1991 by CRC Press LLC

270 257 molybdenum and, sprayed on glass or plastic, acts as a sunscreen. As a powdered sulfides in alcohol Dag is one commercial product) it is used as a spray or paint-on mixture (Aqua metal vehicle the replication technique: after drying, the carbon thin film can surfaces on as for for or, coated with thin film gold study reflectivity, for a scanning removed be microscope (SEM) study. The dry powder has electron brushed on preferentially etched microscope been to defects for microscope examination, as has magnetite and barium titanate. surfaces enhance barium include latter the particles in surface studies of magnetization titanate, or The of nickels, irons, etc. magnetic this book is concerned with inorganic materials, carbon is a major element in Although chemistry C, organic H, O, N — the four elements of our carbon-base life — . . humans, animals, and vegetation. There are thousands of chemicals, solvents, forms . containing organic elements involved in both gases chemistry and medicine. and these any Although alone is not used to Application: extent in Solid State Technical carbon fabrication at present, it is under development as device thin film colloid (c-C) or amorphous a (a~C) structure, as grown by CVD methods using a variety of sources for the deposited such CC14, carbon tetrachloride, carbon, benzene, C6H6, and other such compounds. as with Deposition 400 to 600°C and, between subsequent temperature annealing, the carbon is films are being converted to a crystalline diamond-like carbon (DLC) film; also referred to by the i-C. Additional laser anneal has been used to increase the size of crystallites acronym eventually, it hoped to achieve a complete single crystal diamond structure. As and, is is is hardest of known substances and it chemically inert, it has tremendous diamond the addition a film surface coating, in thin to the diamond semiconducting applications as characteristics. thin silicon, also are deposited on Carbon Si, wafers for the fabrication of thin films for silicon See Silicon Carbide section SiC. additional discussion. There are film carbide, composite materials in use or under development carbon both the industrial and Solid in State as parts and device structures. areas sections on carbides, graphite, and diamond. See Etching: Acid resistant to most chemicals under normal conditions. Dissolves in boiling HNO3, KOH, and in molten fluxes of alkalies and metals. H2SO4, H3PO4, ETCHANTS CARBON C-OOOla Potassium TIME: ETCH hydroxide NAME: flux, TYPE: TEMP: 350°C Molten removal COMPOSITION: ... KOH(NaOH) x DISCUSSION: alkalies C, graphite or thin film deposit. Molten flux of as will attack carbon and bulk graphite, and may be slightly preferential. REF: Kohl, W H —Handbook of Materials and Techniques for Vacuum Devices, Reinhold, New York, 1967 C-OOOlb ETCH Potassium hydroxide TIME: NAME: Alkali, TYPE: TEMP: Boiling removal COMPOSITION: x... 50%KOH(NaOH) DISCUSSION: C, as bulk graphite or thin film deposit. Hot, concentrated solutions of alkalies will dissolve graphite and carbon. REF: Ibid. © 1991 by CRC Press LLC

271 258 CRC of Metal Etchants Handbook C-OOOlc ETCH acid TIME: NAME: Nitric removal Acid, TEMP: TYPE: COMPOSITION: x ... HNO3, cone. DISCUSSION: bulk graphite or thin film deposit. Nitric acid will dissolve graphite or carbon C, as conditions. acid, acid or CO2 + N2O, depending upon etching hydrocyanic mellitic forming Ibid. REF: C-0002a: Bulletin CD-101-5M-SC-282, Stackpole Corp., 1982 as graphite or carbon specimens. Nitric acid will dissolve material and C, produce mellitic hydrocyanic acid with both CO2 and NO. acid, C-OOOld ETCH NAME: TIME: reduction Acid, TYPE: TEMP: COMPOSITION: 20ml...HNO3 40ml...H2SO4 g ...KC1O4 20 DISCUSSION: as bulk graphite or thin film deposit. This solution volume will dissolve C, gram one of forming graphitic acid. carbon Ibid. REF: C-0002b NAME: Sulfuric acid TIME: ETCH Acid, removal TEMP: Boiling TYPE: COMPOSITION: ... H2SO4, cone. x DISCUSSION: C, as both carbon and graphite parts. Solution will form mellitic acid or benzene pentacarboxylic acid CO2 and SO2. with Ibid. REF: M L et al — Phys Rev, 106,251(1957) C-0006a: Halbert, reactions specimens a study of neutron-transfer in by nitrogen ion bombardment. C, used was etched in "fuming" Carbon acid. {Note: Only reference to sulfuric acid as sulfuric "fuming".) C-0003 ETCH Phosphoric acid TIME: NAME: TYPE: polish Acid, 240°C TEMP: composition: x ... H3PO4, cone. DISCUSSION: C, as natural graphite, cleaved as (0001) basal specimens and studied for magnetic domains. Mechanical with carborundum paste (SiC), then with 8 jim diamond paste. polish to Use to hold specimens during etching crucible reduce thickness. Solution also used silica to etch thin and to pinhole specimens for electron microscope (EM) study. {Note: Material e.g., was "plumbite", which is a common name for graphite, called plumbago.) REF: Grundy, PJ — BrJ Appl Phys, 16,409(1965) © 1991 by CRC Press LLC

272 259 C-0004 NAME: Argon 15 min ETCH TIME: gas, TYPE: preferential Ionized TEMP: Argon GAS: COMPOSITION: x Ar+ ions PRESSURE: ... POWER: DISCUSSION: C, graphite specimens. Argon ionic bombardment produces (0001) cleaved pyrolytic pits. conical etch A REF: Gaza, GE — J Appl Phys, 31,1657(1960) Tarpinian, & C-0005 ~~ ETCH TIME: NAME: Water cleaning Acid, RT TYPE: TEMP: COMPOSITION: x...H2O DISCUSSION: as thin films deposits on Si, SiO2, Al, A12O3, KBr, C, ZnMn, GaAs and InP. NaCl, Deposition by RF Plasma using butane, C4H10, with the glow discharge from ultra-pure was transparent electrodes. 8—360 A/min. Film was rate: and amorphous in carbon Growth Water used to wash and clean surfaces to observe hydrophobic/hydrophilic re structure. Film referred to as a diamond-like carbon (DLC) film. action. Zelez, RCA — REF: Rev, 43,665(1982) J C-0006b ETCH TIME: NAME: TYPE: Acid, removal TEMP: COMPOSITION: x ... H3PO4 x ... CrO3 ... NaCN x DISCUSSION: for described as a general specimens. Solution carbon. Other chromates can be C etch and NaCN added for an equivalent 1 ml of used, NH4. REF: Ibid. C-0007a ETCH 1—3 min NAME: TIME: cleaning TEMP: RT TYPE: Acid, COMPOSITION: ml 50 ...HF ml ...HNO3 150 100 ... CH3COOH (HAc) ml DISCUSSION: C, as epitaxy reactor plates and susceptors, or for Silox system deposition of SiO2 thin films. Graphite used in metallic compound growth, such as silicon on silicon, susceptors plain gallium antimonide, etc. They may be indium graphite or coated with silicon arsenide, carbide. The solution shown is used to etch clean plate surfaces to remove silicon and/or and silica water wash after acid cleaning Heavily wipe dry with toweling; then growth. vacuum oven bake at 130°C and 10""3 Torr pressure overnight. CAUTION: Where phos- © 1991 by CRC Press LLC

273 260 CRC of Metal Etchants Handbook gases have used as a dopant during silicon growth, it can ignite under liquid phorus been during cleaning. et al — personal application, 1970—1975 Walker, REF: P C-0007b Hydrogen/chlorine 1—3 min NAME: ETCH TIME: TEMP: 1100°C TYPE: Gas, cleaning COMPOSITION: HC1, (2) x ... H2 vapor ... (1) x DISCUSSION: epitaxy reactor susceptor plates for Si/Si(l 11) epitaxy growth. Susceptors with C, as or SiC The hot hydrogen in reactor system used to clean graphite surfaces without coating. introduction HC1 vapors for additional cleaning. to prior of REF: Ibid. Ibid. C-0007c: lap C, boats and disc parts. Lightly as parts on Whattman filter paper to furnace alloy then fire through belt furnace in clean, gas (85% N2:15% H2) at 450°C prior to forming using fabricated parts, or after cleaning old boats and discs. Firing can be done in a newly humpback furnace. hydrogen C-0008 NAME: Carbonization ETCH TIME: TEMP: Elevated forming Thermal, TYPE: COMPOSITION: x ... heat DISCUSSION: C, wood product by charring. Hard woods are partly burned to remove volatiles, as a resultant material called charcoal. When natural coal is so processed, the is called "coke". it Charcoal been a fuel for glass and metal fabrication since ancient times, and also is has industries as cooking used Coke is widely used in metal processing a today, as a fuel. primary fuel such as for steel manufacture. In the fractionation of petroleum, the pure carbon fraction is called lampblack and used as a pigment. Metal surfaces are carbonized with hot CO2 treatment for hardening and black carbon is to iron it becomes steel. The carbonization process has been a when added in since early manufacture of irons and steels step times. Two notable steels fundamental the the Damascus both were widely used during steel, Middle Ages in Europe. are and Toledo Solid State processing of epoxies and In used for electrical contact, one polyimides method removal is to heat to the char-point with subsequent scrape-off. Carbon thin films of deposited treatment with either heat are or laser annealing, converted to diamond-like and, painted carbon in an alcohol solution is Carbon onto material surfaces, hardened by (DLC). evaporation removal of the alcohol carrier, the resultant film used for surface replication. Molasses has used as an etching solution constituent on quartz frequency crystal blanks, been can after carbon flakes on surfaces but vacuum metallization. Carbon powder has been leave defects onto surfaces to enhance surface material and structure for microscope study. brushed There are several major products uses for carbon, such as electrical ignition wires; to damping atomic reactors; as an additive in high temperature ceramics for both rods electrical and high temperature capabilities; as powder sprayed on plastic sheeting for sun a screen as a heater strip or rod; as applications; black pigment in paint, glass, cement. REF: N/A © 1991 by CRC Press LLC

274 261 PHYSICAL OF CARBON DIOXIDE, CO2 PROPERTIES Gas Classification 6 & 8 Atomic numbers 44.01 Atomic weight 5.2 (°C) Melting atms point -56.6 - solid Boiling point 78.5 (°C) 1.56 Density (g/cm3) solid -79°C 1.101 liquid, (g/1) -37°C (g/1) liquid, 0°C 1.97 =) 1.38—1.46 index Refractive (n ml RT 1.45 g Solubility (100 H2O) 1.79 g (100 ml H2O) 0°C — solid 1.5—2 (Mohs Hardness scratch) (isometric Crystal normal) solid (100) cube structure — (gas) Color Colorless White solid) (crystalline (cubic) (001) Cleavage CARBON DIOXIDE, CO2 in nature as a fraction of air, in waters, and in the General: In certain areas Occurs soil. can associated as a gas from subsurface be and volcanoes, or be released into it magmas atmosphere from earth fissures. It is a by-product of combustion; comes from decaying the matter; and the gas resulting from fermentation, such as beers and wines. Animal life is air, extracts oxygen, and release carbon dioxide; whereas vegetation uses carbon breathes the oxygen a into the atmosphere ... releasing symbiotic life cycle. dioxide, back of decomposition carbonate minerals or reduction certain their metallic ores can The of the gas. Like nitrogen, it will not support combustion — it is a by-product of release — and can be lethal when oxygen is not present. Skin contact should not be combustion with ice as it can cause burn-like blisters. made dry a commercially prepared food product, it is dissolved in water As soda water, seltzer as water, carbonated water. In addition to the or fermentation of beers and wines ... the natural British "bubbly" is champagne ... it is added to soft drinks for effervescence as a car bonated beverage. as solid ice (-79°C) it is used as a temporary refrigerant, such as for Industrially, dry epoxy shipped polyamide pastes that are of frozen for extended shelf- transportation and as used large volumes, it usually is transported Where a cryogenic liquid at around life. in In chemical processing, dry ice has been used as a freezing mixture in -37°C. acetone (-100 - 80°C) for the removal of water vapor from other gases, or as a chilling medium to etching, a hardening agent, or as an oxidizer. in as Application: Not used directly in Solid State device design, Technical it is though occasionally as a drying gas or cleaning used at room temperature like nitrogen, argon, agent and helium, but at elevated temperatures can be reactive as an oxidizer or carbonizer. CO2 has been through etching solutions for stirring action only or as an active element bubbled oxidation as etch action. The gas also has been used as a hot furnace gas for an oxidizing and with usually combination agent, air and/or oxygen, or as a mixed gas in the carbon with fraction forming carbides, specifically silicon carbide on silicon surfaces. As dry ice in laboratories, it is used as a temporary refrigerant for the storage of such materials gallium, bromine, epoxy, and polyamide formulations. as Dry ice is one of the few compounds that sublimes directly from the solid to the gaseous it state passing through a liquid state, though without can be liquefied under pressure as a © 1991 by CRC Press LLC

275 262 CRC of Metal Etchants Handbook gas. It been studied as a crystalline mass of dry ice and grown as a single cryogenic has morphological studies. crystal for without Etching: melting. Solid sublimes CARBON DIOXIDE ETCHANTS COD-0001 nitrogen TIME: ETCH NAME: Liquid forming TEMP: Freezing (- 196°C) gas, Cryogenic TYPE: COMPOSITION: LN2 x ... DISCUSSION: grown a single crystal using CO2, cold temperature cryostat in order to measure a as index. and varies with wavelength, refractive is between n = 1.38 and 1.46. Index the Appl K et al — J E Phys, 39,2968(1968) Tempelmeyer, REF: COD-0002 NAME: Methyl alcohol TIME: ETCH TYPE: Alcohol, TEMP: chilling COMPOSITION: (1) MeOH (2) x ... acetone x ... DISCUSSION: as "dry ice". Used as a mixture of chunks in methanol or CO2, it is a acetone solid It used removal of water vapor in gases. for has been used for drying of "cold solution" from argon A-l cylinders where argon was used to backfill sealed quartz tubes pressurized containing wafers for closed tube gallium diffusion in fabrication SCRs. Both liquids silicon above structure act as shown etchants on solid CO2. can — REF: & Orwin, H P personal application, 1974 Walker, COD-0003 ETCH NAME: Carbon dioxide TIME: TYPE: Gas, TEMP: oxidation COMPOSITION: x...O2 CO2 x ... DISCUSSION: is a furnace gas mixture to oxidize as metal to chromium trioxide CO2 used chromium study of in a Cr2O3. Torkington, S & Vaughn, J G — R Vac Sci Tecknol, A(3),795(1985) REF: J CERAMICS The term General: still applied to the pottery industry which has been in existence is for 10,000 years, and it includes many natural minerals, such as corundum, A12O3, some a quartz, as two crystal varieties; and as and group, both the feldspar and clay minerals. SiO2, Aluminum silicates as orthoclase or microcline, KAlSi3O8, and albite, NaAlSi3O8 are found in some of all rocks and, with weathering, break down forming clay minerals: kaolinite, 60% as metal admixture with sand, iron, and other Al2H2(SiO4)2, oxides is common clay — an of from Kaolin is a high purity form feldspars. kaolinite which, when heated, burns to the a white enamel and is used for fine "bone" china, pottery, and porcelain. that Fuller's a form of clay is absorbs water, as does montmorillonite. Bentonite Earth is a colloidal clay that will swell in water, and is used as a packing around piping in oil © 1991 by CRC Press LLC

276 263 fields, as a filler for rubber products or binder in manufacturing of lead pencils, e.g., and powder. carbon pottery, finely powdered clays will form a wet plastic mass that can be shaped, In making by then remove the water content. The wet mass is called slip. For heating hardened to such tile pottery, porcelain, brick or tile, and products, piping, it is kiln general clay as prior 1400°C. is a porous product called bisque; firing to second firing the at fired First coated with a feldspar silicate paste to make the clay water tight surfaces glaze); prior are (a third as for enamels, coat or paint with metallic oxides for color — hematite, to firing, for red for blue; chromium trioxide cobalt green, etc. as ocher; Fe2O3, uses a high silicate content clay, is fired Hard above 1600°C without further porcelain at and forms porous pottery ware, such it terra cotta, bricks, crockery, etc. This treatment, as of clay, when fired at a lower temperature along with red ocher (hematite) is standard type fabrication and, if NaCl (halite, common salt) is added, produces a glaze. Refractory brick such as contain both magnesium and chromium oxides for high tem ceramics, fire-brick, a It application of silicates and glass as the surface glaze on clay stability. was perature with development of soda-lime glass, circa pottery B.C.) that produced the (Egyptians 3500 ceramic name: pottery. become of quality refractory production has high separated from the ancient The ceramics original pottery field in modern times as the ceramics industry, which includes both and products general as fire-brick and tile, as well as high purity alumina or beryllia substrate such in Solid circuit fabrication. used State of ceramics now composite with variety are metal oxides, some of Many manufactured include carbon or graphite. As an example, most which substrates are pure A12O3, alumina as white ceramic, but there is a black alumina containing a which can be electrically carbon active rather than an insulator. Alumina is supplied as pressed powder blanks; as amorphous, fused alumina, called fused sapphire; as single crystal sapphire. The sapphires are clear and transparent, and or only be from similar quartz blanks by material hardness . . . H = 7 can differentiated . single = 9 (sapphire). Both sapphire and quartz . . crystal blanks used as (quartz) H usually oriented as basal (0001) surfaces. substrates are etc.) yellow/brown garnet (YIG, YAG, slightly blanks are available Transparent, tinted (001) or (110) orientation, cubic, or dodecahedral, respectively. Red fused alumina — in — pouring manufactured by ruby a liquid melt into high temperature resistant metal forms is fabricated, as variety of products are so A such as tubes, rods, flats such molybdenum. wire bonding tips, or further processed as high temperature ball-bearings (ruby (substrates) spheres). Although glass industry is a separate entity ... the clay, pottery, silicate, glass, the glass and are inter-related . . . and industries is not normally considered a ceramic, ceramic but the Solid State industry used both silica and quartz blanks as substrate. Clear, fused amorphous silica, oriented single crystal quartz. The latter, as alpha-quartz; processed as or artificial frequency both natural quartz and from boules. In glass applications radio crystals such substrates, the material is often grouped with and called a ceramic or dielectric. as The ferrites another group of materials that are distinct, but can be classified as are in type with regard to some applications materials Solid State processing. They are ceramic supplied as flats or blanks like other substrates as mixtures of iron, carbon, and other metal additives. They coal black in color with highly polished surfaces, and specifically are for circuit of microelectronic formulated resistors at different frequencies. All of fabrication substrates, including the ferrites, are metallized, then photolithographically patterned these as circuits or discrete devices. mentioned Technical of the ceramic material All above have wide use and Application: application in Solid State circuit fabrication, in addition to their normal applications as stand-offs furnace furnace tubes and liners; insulated fire-brick; in both vacuum systems and © 1991 by CRC Press LLC

277 264 CRC of Metal Etchants Handbook fixtures, or device packages; as tubes or beads for high temperature thermocouples, test in alumina as boiling beads; the pressed powder solution as a tool crucibles; chemical or the cutting tool, itself; or as lapping abrasives, sharpener; mention only a few such as to uses. fabrication the ceramics are primarily device — for mounting of discrete In insulators after metallizing and circuit patterning of the devices, Several also are used as substrate. discrete such as the ferrites as resistors, or glass and ceramics as dielectrics, and devices, filter for elements. those ceramics referred to as cermets are shown here. The others are listed under Only individually sections. their named See individual ceramics, borides, glass, etc. Etch solutions vary with Etching: type material, all are generally difficult and etch. to CERMET ETCHANTS CMT-OOOla ETCH NAME: TIME: TYPE: Acid, TEMP: RT removal COMPOSITION: 1...HF HNO3 5 ... H3PO4 ... 60 DISCUSSION: as a deposited thin film Cr.SiO coating. Solution used for both surface (30%) surface and material removal. Over 30% SiO limits the cleaning rate. (Note: There is a wide etch variety cermet materials.) of Technology, Miassel, & Glang, R — Handbook REF: Thin Film LI McGraw-Hill, New of York, 1970. CMT-OOOlb ETCH NAME: TIME: TYPE: Acid, removal TEMP: 50—60°C COMPOSITION: 20 ... K2Fe(CN)6 g g 10 ...NaOH 100ml...H2O DISCUSSION: (30%) as a deposited thin film coating. Solution Cr:SiO for both surface cleaning used and removal of the material. REF: Ibid. CERAMIC ETCHANTS CERM-0001 ETCH TIME: NAME: Metal, TEMP: TYPE: contacts COMPOSITION: x PdCl2 ... x ... H2O x ... SnCl2 DISCUSSION: palladium Dipping parts in a stannous Ceramics. chloride solution prior to electroless © 1991 by CRC Press LLC

278 265 nickel produces a light Pd coating that aids in the gripping power of nickel. Nickel plating evaluated at with a 0.001 mm thick deposit. plating 95°C D REF: Sauer, H A — J Electrochem Soc, 107,250(1960) & R Turner, — Met Finish, 53,59(1955) F Pearlstein, CERM-0002: in CERM-0001 for palladium Reference cited solution. PROPERTIES CERIUM, Ce PHYSICAL OF Lanthanide Classification Atomic 58 number 140.13 Atomic weight point 795 Melting (°C) Boiling point (°C) 3468 (g/cm3) 6.67 (6.90) Density conductance 0.026 Thermal (cal/sec)(cm2)(°C/cm) heat (cal/g) 25°C 0.042 Specific of fusion 1.2 Heat (k-cal/g-atom) of (cal/g) 8.5 heat Latent fusion vaporization (k-cal/g-mole) 95 Heat of (W/D) 21.0 Atomic volume 1st ionization energy (K-cal/g-mole) 159 ionization potential (eV) 6.54 1st (Pauling's) Electronegativity 1.1 radius (angstroms) 1.65 Covalent radius 1.07 (Ce+3) Ionic (angstroms) Electrical conductance (micro-ohms~!) 0.013 resistivity (10~6 ohms cm) 20°C Electrical 75 Poisson's 0.248 ratio modulus (x Young's 6.3 106) Tensile strength (psi) 15.000 Yield strength (psi) 13.200 Magnetic susceptibility emu/mole) 2.430 (10~6 work function 2.84 Electron (eV) (barns) section 0.7 Cross Hardness (Mohs — scratch) 1—2 kgf/mm2) (Vickers — 24 structure (isometric — normal) (100) cube, fee Crystal (solid) Steel-grey met. Color Cleavage (cubic) (001) Ce CERIUM, Does not occur as a native element though there are over General: minerals containing 50 cerium. include fluorides, oxides, These phosphates, niobates, and tantalates. carbonates, As a group, there is the Cerium Group of metals, which also are members of the Rare Earths. One use of cerium metal in industry is as an alloy with iron producing major and ... cerium producing sparks for cigarette the gas lighters, gas ignition spar- "flints" kers, etc. As cerium oxide it is used to make incandescent gas mantles, producing an intense white with only slow disintegration of the material. light Technical Application: Though not used to any extent in Solid State processing to date, © 1991 by CRC Press LLC

279 266 CRC of Metal Etchants Handbook has possible as a doping element in compound semiconductors or as an element it application garnets. in manmade dilute acids. Etching: in Soluble CERIUM ETCHANTS CE-0001 ETCH TIME: Nitric NAME: acid TEMP: RT removal TYPE: Acid, COMPOSITION: HNO3 ... x ... H2O x DISCUSSION. Material be etched in dilute acids. specimens. can Ce C D et REF: — Handbook of Chemistry and Physics, 27th ed, Chemical Hodgman, al Co., Cleveland, Rubber 1943, 364 OH, CE-0002: P — Mineral study, 1954 Walker, monazite, as fraction in the mineral element (Ce,La,Di)PO4. H2SO4, HC1 and Ce an used in a separation evaluation of constituents of the single crystal elements of the HNO3 material. PHYSICAL OF CERIUM DIOXIDE, CeO2 PROPERTIES Oxide Classification numbers 58 & 8 Atomic Atomic weight 172.13 point (°C) Melting 1950 Boiling (°C) point (g/cm3) 7.3 Density (Mohs — scratch) 5—6 Hardness Crystal structure (isometric — normal) (100) cube Color (solid) White/yellow (cubic) (001) Cleavage CeO2 CERIUM DIOXIDE, not occur in nature as an General: though there are some 50 cerium containing Does oxide of the Rare Earth group, minerals there is the allied Cerium Group of metal elements. and The can be fabricated as a thread, oxide woven into a cloth-like material used as then a gas mantle that produces an intense white light at incandescent heat, and is still used for lanterns, such the Coleman lantern using white gasoline as the gas source. as processing Technical used in Solid State Not at present, but may have Application: application as a thin film protective coating on semiconductors similar to that of other oxides material. and as a high temperature dielectric/ceramic or nitrides, Etching: H2SO4, HNO3. CERIUM OXIDE ETCHANTS CEO-0001 ETCH Sulfuric acid TIME: NAME: TYPE: Acid, removal TEMP: COMPOSITION: x ... H2SO4 © 1991 by CRC Press LLC

280 267 DISCUSSION: Ce2O3 specimens. Both materials can be dissolved in this solution. CeO2 or 27th C et Hodgman, — Handbook of Chemistry and Physics, D ed, Chemical REF: al Co., Cleveland, OH, 1943, 368 Rubber Cs OF CESIUM, PROPERTIES PHYSICAL metal Alkali Classification 55 number Atomic 132.9 Atomic weight 28.61 (°C) Melting point 690 (°C) point Boiling 1.892/1.873 (g/cm3) Density 18°C/20°C 0.0440 Thermal conductance (cal/sec)(cm2)(°C/cm) liquid 0.052 (0.048) 20°C (cal/g) heat Specific 3.913 Heat (cal/g) fusion of 3.766 heat of fusion (cal/g) Latent 146 vaporization (cal/g) of Heat 70 (W/D) Atomic volume 90 (K-cal/g-mole) 1st ionization energy 3.89 potential ionization 1st (eV) 0.7 (Pauling's) Electronegativity 2.35 (angstroms) Covalent radius (Ce+I) 1.67 Ionic radius (angstroms) 1.89 Electron work function (eV) 0.10 10~6) x susceptibility Magnetic (cgs 97 of Coefficient linear expansion thermal (xl0"6cm/cm/°C)20°C 20 Electrical resistivity (ohms cm x 10~6) 0°C 30 section Cross (barns) 509 (°C) Vapor pressure 4—5 (Mohs — scratch) Hardness cube, bcc (100) — normal) Crystal structure (isometric Silver-white (solid) Color (spectra) Blue (gas) (001) — Cleavage perfect) (cubic Cs CESIUM, Does not occur as a native element. A primary ore is the mica lepidolite, and General: rare extracted mineral. It also is the from certain mineral springs as a halogen. It pollucite potassium, an metal with characteristics similar to alkaline and has a high affinity for is oxygen. Due to the latter, it is used as an oxygen "getter" in radio tubes and photo-electric cells, and be used in ion-pump vacuum systems as a replacement for titanium as a could of getter. used as a catalyst in hydrogenation is certain organic compounds in chemical It processing. Technical Application: There has been no use of the pure element in Solid State pro an cessing, though it has been used as date, additive to special garnets, ferrites, etc. It to is under evaluation as a nitride, CsN, for both a surface coating and for optical characteristics. Etching: Water and acids. © 1991 by CRC Press LLC

281 268 CRC of Metal Etchants Handbook ETCHANTS CESIUM CS-0001 Water NAME: TIME: ETCH TEMP: to hot TYPE: Acid, RT removal COMPOSITION: H2O x ... DISCUSSION: specimens. Like many of the rare earth elements, the material reacts with water Cs metal recognizable with sound, converting to the hydroxide with release of hydrogen, a hissing and that used to hydrogenate other compounds is materials, particularly in organic such it chemistry. Foster, W & Alyea, H REF: — An Introduction to General Chemistry, 3rd ed, D Van N Nostrand, York, 1948, 422 New PROPERTIES OF BROMIDE, CsBr PHYSICAL CESIUM Bromide Classification Atomic & 35 55 number weight Atomic 213 Melting point (°C) 636 point (°C) 1300 Boiling (g/cm3) 4.44 (4.5) Density index =) 1.6984 Refractive (n Wavelength limits (micron) 0.2—40 modulus (psi Young's 106) 2,3 x Coefficient of linear thermal expansion 48 (xlO-6/cm/cm/°C) Hardness (Mohs — scratch) 2—3 Crystal structure — normal) (100) cube (isometric (solid) Clear Color — perfect) Cleavage (cubic (001) CESIUM BROMIDE, CsBr Does not occur as a solid natural compound, though cesium metal is extracted General: from hot as a bromide or iodide in solution. springs processing, used industry Not a compound in metal in but does have some medical as applications. Technical Application: Not used in Solid State processing though it can be used as a bromine-type etchant on semiconductors and other metallic compounds. solution for has evaluated It a single crystal been general morphology, and for defect studies. as The material has been used for its optical and filter element properties of infrared transmission even though is hygroscopic. it Soluble Etching: cold water and acids. in CESIUM BROMIDE ETCHANTS CEBR-0001 NAME: Ethyl alcohol TIME: ETCH TYPE: Alcohol, polish TEMP: RT COMPOSITION: X...EOH © 1991 by CRC Press LLC

282 269 DISCUSSION: (100) specimens. is hygroscopic and soft. Polish surfaces with alcohols. CeBr, Material infra-red transmission. Used for REF: CEBR-0002 NAME: TIME: ETCH TYPE: Hot Metal, decoration TEMP: COMPOSITION: ... HAuBr4 (2) x ... Au (3) x ... Ag (1) x DISCUSSION: (001) Used in a study of dislocation development by metal decoration. specimens. CeBr, (2) surfaces (1) or evaporate metals shown in solution and (3). Heat treat and Coat with anneal metal decoration drive-in. "Colloidal" gold will diffuse into CeBr and deposit for at sites. dislocation Amelinck, S Phil Mag, 3,307(1958) REF: — CEBR-0003 NAME: ETCH TIME: polish TEMP: RT TYPE: Alcohol, COMPOSITION: ... MeOH 25 1 ... H2O DISCUSSION: (001) wafers CsBr, to measure the elastic constants using ultrasonic resonance. used Mechanically lap with A/O 302 grit; polish rough with 303V2 grit; then Linde A; and lap then sapphire dust on cloth. Use kerosene as the carrier liquid for mechanical lap/polish. Etch polish solution shown and rinse in isopropyl alcohol (IPA), then rinse in carbon in CC14. See Iodide. tetrachloride, Cesium — D & Bulef, M I J Appl Phys, 31,1010(1960) REF: Menes, PROPERTIES OF CESIUM CHLORIDE, CeCl PHYSICAL Chloride Classification numbers 58 & 17 Atomic weight Atomic 168.37 Melting point (°C) 645 point (°C) Boiling 1290 Density (g/cm3) 3.97 Refractive index (n =) 1.6418 Hardness (Mohs — scratch) 1.5—2.5 Crystal structure — normal) (100) cube (isometric (solid) Color Colorless Cleavage (cubic) (001) CESIUM CHLORIDE, CsCl Does not General: as a natural solid compound though cesium metal is extracted occur from hot springs and ocean water. The latter may be as a CsCl saline solution. metal There no use of the compound in industrial is processing, but it may have some medical applications. © 1991 by CRC Press LLC

283 270 CRC of Metal Etchants Handbook Application: No in Solid State processing to date, though it can be used Technical use as etching metals and compounds on a chloride. an as solution been grown as a single crystal by solution evaporation and by molten flux growth It has properties study. for in and alcohols. Etching: water Soluble CESIUM CHLORIDE ETCHANTS CSCL-0001 Water TIME: ETCH NAME: removal TEMP: RT Acid, TYPE: COMPOSITION: x ... H2O DISCUSSION: grown as single crystal CsCl solution evaporation, and from a molten flux. Also as by CsCl:Na2CO3(10%) Water can be used to remove and polish specimen surfaces. crystals. used in growth methods and properties study. Materials a J P Smakula, A — Avakian, Appl Phys, 31,1720(1960) REF: & PROPERTIES OF CESIUM DIOXIDE, Cs2O PHYSICAL Classification Oxide numbers & 8 Atomic 55 Atomic weight 281.82 point (°C) 300 del. Melting point Boiling (°C) (g/cm3) 4.30 Density (Mohs — scratch) 5—6 Hardness Crystal structure (isometric — normal) (100) cube Color (solid) Red-orange (cubic) (001) Cleavage Cs2O CESIUM DIOXIDE, not occur as a natural compound as General: is soluble in water though it may Does it as a surface temporary coating on other cesium minerals under occur dry conditions. very As metal has a high affinity for oxygen like titanium, it is used as cesium oxygen an "getter" vacuum tubes, and could be in in ion pump vacuum systems. used Technical Application: No use in Solid State processing to date, though the hydroxide, CsOH, has used in etching formulations. been mono-oxide, crystal has been grown and studied as a single This from molten Cs2O, as Specimens (111) cleaved with difficulty, were the (100)/(110) planes direction or fluxes. (001) basal plane are the more normal cleavage planes in the isometric system — normal (cubic) class. Soluble in water and Etching: alcohols. CESIUM DIOXIDE ETCHANTS CSO-0001 ETCH NAME: Sodium hydroxide TIME: TYPE: Alkali, cleaning TEMP: COMPOSITION: x... liVNaOH © 1991 by CRC Press LLC

284 271 DISCUSSION: (111) wafers with difficulty from molten flux grown single crystals Cs2O, cleaved to flux), in a compound study. Solution used used clean surfaces and ditungstate (lithium cleaving. after C B & Clerk, G W — J Appl REF: 37,3910(1966) Finch, Phys, PLATINIDE CESIUM ETCHANTS CEPT-0001 NAME: etch TIME: 10—60 sec ETCH Railing's polish TYPE: RT Acid, TEMP: COMPOSITION: 100 ml ... HC1 5g ...CuCl3 100 ... EOH ml DISCUSSION: in melted in fabrication, and used arc a study of metallic compounds. CePt specimens used as a general removal and polishing etchant. Other compounds evaluated: Solution Ho2O17, Ho2Fe17, Ho2Co14Fe3, UCe2, UPt3, UNi2, UCo2, V3Si, V3Ge, Zr2Nl7, MoSi2, CeSi2, Y2(CoM)17 Crystals TiSi2. the modified Bridgman method were grown where M = Al, by Fe, Cu, and Ni. REF: Slepowronsky, M et al — J Cryst Growth, 65,293(1983) PHYSICAL PROPERTIES CESIUM IODIDE, Csl OF Iodide Classification 55 & 53 Atomic numbers 259.83 weight Atomic (°C) 621 point Melting point 1280 Boiling (°C) Density (g/cm3) 4.52 index (n Refractive 1.7876 =) Hardness — scratch) 2—3 (Mohs structure cube — normal) (100) Crystal (isometric (solid) Color Clear Cleavage (cubic) (001) CESIUM IODIDE, Csl General: Does not occur as a natural compound, but may be found as a liquid fraction in hot and ground water like bromide and chloride. springs but used industrial metal processing, Not can have medical applications. in Technical Application: Not used in Solid State processing, though it can be used as an etchant metals and compounds. on It has been grown and studied for physical properties as a single crystal. Etching: Soluble in water and alcohols. © 1991 by CRC Press LLC

285 272 CRC Metal Etchants Handbook of ETCHANTS CESIUM IODIDE CSI-0001 TIME: NAME: ETCH RT Alcohol, warm TEMP: TYPE: polish/removal to COMPOSITION: MeOH ... 25 1 ... H2O DISCUSSION: oriented single Csl, wafers used to measure elastic constants with ultrasonic (100) crystal frequencies. rough lap with A/O 303 Mechanical then polish lap with resonance abrasive, 302V2, both as slurries on an iron lap platen. Mechanically fine polish with Linde A A/O (iron alumina with diamond dust on a cloth, all using kerosene as the liquid lap), then in final polish, use solution shown, rinse chemical isopropyl alcohol (IPA), then carrier. For tetrachloride, CC14. Preparation method can be used on bromides and chlorides. carbon J Bulef, & Menes, M — I Appl Physt 31,1010(1960) D REF: PROPERTIES OF CHLORINE, Cl2 PHYSICAL Halogen Classification 17 Atomic number 35.45 weight Atomic -102 (-100.98) Melting point (°C) -33.7 (-34.6) Boiling point (°C) 1.57 -33.6°C (g/cm3) Density 3.214 — (g/1 0°C liquid) 0.182 conductivity 20°C 10~4 Thermal (x cal/cm2/cm/°C sec) 21.6 of (cal/g) Latent heat fusion 0.116 20°C heat Specific (cal/g/°C) 215 ml Solubility (100 ml H2O) 20°C 13.01 (eV) potential ionization 1st 1.81 (angstroms) radius Ionic 33 section (barns) Cross -71.7 (°C) pressure Vapor - .000768 index (n =) gas Refractive 140 (C.T. Critical temperature °C) 83.9 atms) (C.P. pressure Critical (110) prism Crystal normal) — (tetragonal structure Yellow-greenish (solid) Color (001) Cleavage (basal) C12.6H2O HYDRATE, I OF CHLORINE PHYSICAL PROPERTIES Hydrate Classification 8 & 1, 17, numbers Atomic 170.01 Atomic weight 9.6, del. (°C) point Melting point (°C) Boiling 1.23 Density (g/cm3) f°C temoerature Formation water) in 0 © 1991 by CRC Press LLC

286 273 Hardness — scratch) solid 1.5—2.5 (Mohs structure (hexagonal rhombohedral) r(10Tl) rhomb Crystal — Light Color yellow (solid) (lOTl) (rhombic) Cleavage CONTAINING CHLORINE ETCHANTS (22.2°C gas standard greenish-yellow and pressure at and 760 a is Chlorine temperature to that of fluorine. Chlorine mmHg) a disagreeable odor and, if breathed, very similar has irritating the membranes of the eyes, nose, to throat. In contact with excessively is and air it produces heavy white fumes of hydrogen chloride, HC1, which also moisture a in is irritant can cause suffocation, even death. Fluorine and chlorine are the gaseous severe and and the which include bromine (liquid) group, iodine (solid) with of halogen elements weight and reactivity in the order shown. As chlorine can be reducing at atomic liquefied under atm of pressure, it was one of the 6 gases to be liquefied as a cryogenic gas. 0°C first chlorine is introduce into water containing ice, and is chilled, it will solidify as the If greenish-yellow hydrate, C12.8H2O. the metal all metals and alloys are subjected to corrosion studies by other In industries at compounds, the effect of chlorine include various temperatures and, and elements which will combine with most elements, it is of major concern in developing acid as chlorine In alloys. processing, silicon has been etch polished or thinned by resistant semiconductor germanium chlorine under intense light. Both water and silicon have been bubbling through electrolytically at 300°C with a jet etched gaseous chlorine. of Chlorine a number of useful acids and compounds in addition to several dangerous forms As hydrogen (hydrochloric acid or muriatic acid). HC1 a solution in water, gases: chlorine, was discovered by Glauber (circa 1648) from the interaction of sodium chloride, NaCl it salt) and sulfuric acid, H2SO4. Priestley (1772) collected gaseous hydrogen chloride (common salt, named "marine-acid and because it was produced from it and it is now called air" muriatic acid. Both hydrochloric and sulfuric acids occur in nature associated with volcanic activity — the releases chlorine and sulfur as gas — which combine with hydrogen and salt volcano the air if submerged in the ocean, from the salt water. Hydrochloric acid is used as in or, solvent in materials; in the preparation of chlorides and chlorine; general the cloth a of diges in as a industry; and plays a major role in human medicine dyeing disinfectant; ... 0.2 to 0.4% HC1 in gastric juices. tion use of gas in warfare during World War I led to The outlawing of the use of gas in the war the Geneva Convention, which has been accepted by most humane nations of the by times Gas used in warfare since ancient been and, unfortunately, is still being world. has to some extent. The Japanese attempted gas warfare used the Chinese, on a small against scale, World War II — fortunately, the during were blowing in the wrong direction, winds or changed direction, and the Japanese got the worst of it. Anthrax, a cattle disease, was evaluated during World War II by the British — virulent permeates not mammilary life but as a bacteria kills the ground and remains lethal it only Recently it was reported the Russians used gas in for years. and Iran has Afghanistan, accused of gas warfare. Iraq World of gases developed Some used during the War I are described below, mainly and as they can be a by-product of metal and metallic compound processing when chlorine and its compounds used, and some knowledge of their danger should be considered: are 10,000 Cl2 Chlorine. A 1 part chlorine to • parts of air concentration causes severe — breathing difficulty which will incapacitate a man within about 5 min. The Germans 1915. used first time on April 22, for the The gas is wind-borne, about 2.5 chlorine times heavier than air, and is carried as a ground hugging cloud across the surface. © 1991 by CRC Press LLC

287 274 CRC of Metal Etchants Handbook possible reason the Axis powers not using gas in Europe during World War One for be II the fact that, though variable by locale and season, the prevailing due could to — the and English Channel blow inland Sea across Germany. off North winds coming is used as a jet etch, as a furnace gas • metal corrosion study, and is Chlorine gas in other as part of an etching system. solutions and HC1O4 are acid through bubbled HC1 or in combination with other acids. HC1, etches, pressurized cylinders, alone, from di-, and chlorosilanes from liquid sources are used in silicon epitaxy growth, and tri-, to can produce vapors if released chlorine the atmosphere. both and heavy water, C12:H2O, as well as HC1 and HC1O4, are used as disinfectants in • Chlorinated Chlorinated lime, is a bleaching agent in the wood and textile industries. water. CaOCl2, in will bacteria, and is used destroy sewage disposal. Chloral, Chloramine, NH4C1, is a medical hypnotic, Chloroform, CHC13, is a medical anesthetic alone CCI3CHO, or with iodine, I2, as a solution; and also has been used as a metal surface dissolved Carbon tetrachloride, has been used in dry cleaning, and is still used cleaner. CC14, solvent. type or as a metal cleaning extinguishers, Many of die "pyrene" in fire such as trichloroethylene, TCE, are being replaced due to their chlorinated solvents, Ethylene nature. C2H5C1, is a medical anesthetic like chloro carcinogenic chloride, and occasionally been used as a cleaning and drying solvent for metals. form, has COCI3 — Phosgene. Primarily a respiratory irritant, and more poisonous • chlorine. than It was a war gas during World War I. Caution should be observed in mixing etch also compounds, with and other chlorine acid as certain mixtures solutions hydrochloric produce phosgene. Phosphene, PH3, as a gas, is used as an n-type dopant in silicon can fabrication, and should not be confused with phosgene, (hough it too is dan device if breathed. gerous burns; (C3CCH4C1)2S Mustard gas. Severe • — attacks lungs, larynx, and bronchial skin tubes. Probably the best known of the World War I gases as so many soldiers were affected. Hitler, example, was severely gassed near the end of World War I; in for he was hospital at the end of the war, and had gastritis problems for the rest fact, in his life, of the contributing causes to one final physical degenera his possibly of the treatments he was given over the years also contributed. tion ... — • or chloropicrin. Induces coughing, vomiting, and un CC1:NO3 Nitrochloroform, a The hypochlorite, NaCIO, as sodium 0.5% solution is consciousness. compound to reduce the effects of gangrene, which was referred used as trench foot in both to World I and World War II, and has been a major cause of death or loss of limbs War all with ancient time. Secondary effects of since of these war gases associated wars asthma, weakened heart, and gastritis. are also "tear be made of Mention gas" — a lachrymator — which is a slight should tear irritant, mainly affects the eyes and and glands. There are several concentration inhalation mixtures of bromine-acetone which comprise the family of tear gases. They are not per manently debilitating are widely used throughout the world for crowd or mob dispersal. and odor enough, has an astringent, slightly pleasing gas and, in light con Interestingly tear many individuals can withstand the "tearing" effect for several minutes, al centrations, though the become irritated and inflamed. Many mixtures of bromine-methyl alcohol eyes metallic are as etchants for metals and (BRMs) compounds, but do not produce the used tear gas effect unless acetone is used with the mixtures. Bromine itself is poisonous and can be a irritant. Methyl alcohol is wood alcohol, also poisonous if ingested. severe than number and gases, chlorine forms a Other of important compounds. Sodium acids chloride, chloride, halite, NaCl, and potassium mineral the mineral sylvite, KC1, both the occur in sea water and as sublimation products around hot springs and volcanoes. Ammonium used chloride, salt ammoniac (chloramine) NH4C1, mineral in sewage disposal, also is the found as a sublimate around volcanic fumaroles. Halite is common salt and essential to the © 1991 by CRC Press LLC

288 275 human bitter in taste, which is not retained by the body as is common salt, is diet. Sylvite, "sea commercially used as a dietary replacement for true salt. In Solid salt", called and crystal study, and KC1 are used as single NaCl wafers, and cut as (100) materials State both for thin film evaporation of metals and epitaxy growth of oriented substrates compounds. deposited films are removed by water as the float-off technique for study by The thin microscopy addition, In electron both of these salt chlorides are used (TEM). transmission solutions, as molten fluxes, or in solder fluxes. etch in following is a selected list of chlorine-containing etchants. Aqua regia solutions are The in See Etchant Section under individual materials for additional a the list. separate shown solutions. Ref. Use Material Formula Al Removal AL-0003b HCl, cone. removal Heavy Al AL-0003b 20H2O 1HC1:1— Polish AL-0030 Al 4HF:35HNO3:61HC1 Al AL-0030 Preferential 4HF:35HNO3:61HCl:100H2O Electropolish AL-0017 Al lHC!04:5Me0H AlAu(2%) ALAU-0001 Electrolytic, defect XHC1O4:XEOH Cleaning AlSi(5%) ALSI-0001 1HC1:1H2O ALSB-0002a AlSb Polish acid H-Tartaric 4HC1:4HNO3:1 Macroetch AlSb ALSB-0006 1HC1:1HNO3 Oxide removal ALO-OOOlb A12O3 35 rag CrO3/l ml HClO4:20 A12O3 Preferential ALO-0016 X6ATHC1 As Polish AS-0003C 1HC1:2HNO3:12HAc Polish/Removal Ba BA-OOOlb HCl, cone. BAT-0001 Structuring HCl, cone. Be Removal BE-0002 HCl, cone. Electropolish Bi 10mlHCl:lgI2:200mlH2O BI-0004 Removal Bi2O3 BIO-0001 cone. HCl, Bi2Te3 Preferential BITE-OOOla 1HC1:2HNO3:6H2O Removal WB2 WB-OOOla Regia" 3HC1:1HNO3 "Aqua Removal Brass 4HC1:1HNO3 BR-OOOlb Bronze Polish Cd3As2 CDAS-0001 cone. HCl, CDSE-OOOla Preferential CdSe 1HC1:1HNO3 CdSe CDSE-0003 Polish 3HCl:lHNO3:10H2O CdSe CDSE-OOOlb 1HC1:30HNO3:30HAc Preferential CdS removal Damage CDS-OOOla cone. HCl, CdS CDS-OOllb Preferential 1HC1:1HNO3 Preferential CdS HCl, vapor CDS-0001 Polish HNO3:5 10 ml H2O CdTe 10 ml HCl: ml CDTE-0006d Etch" "P ml 10 CdTe Br2 mg 10 Etch: P Preferential CDTE-0006e "PBrEtch" Removal/polish Ca HCl, cone. CA-0001 Polish CaCO3 HCl, cone. CAO-0001 CaWO4 Preferential Regia" 3HC1:1HNO3 "Aqua CAW-OOOlb Removal CF-0001 Cf cone. HCl, Cr CR-0003 Removal 3HC1:1H2O2 Cr B6) lHCl:2FeCl3(35° Removal/polish CR-0010 Electropolish ml 500 EOH Co HCl:500 ml CO-0001 © 1991 by CRC Press LLC

289 276 of Metal Etchants CRC Handbook Formula Material Use Ref. Cu Polish sol. sat. lHCl:3FeCl3, CU-0025 Cu lHCl:lH2O:lFeCl3 sat. sol. Preferential CU-0013b ml Removal 10 HNO3 CUjO ml HCl:1000 CUO-0014b cone. Cleaning HC1, Ga GA-0002 GASB-OOOla Removal GaSb HC1, cone. GASB-0008b HC1:1 ml H2O2:2 ml H2O Preferential GaSb 1 ml GaAs Cleaning HC1, vapor GAS-0028 lHCl:lHNO3:8glycerin GaAs Polish GAS-0050 GaAs Preferential GAS-0057 2HC1:1HNO3:2H2O Polish 1HC1:2HNO3 GaP GAP-0002 Removal GAP-0014 GaP cone. HC1, GaP Regia" "Aqua Selective 3HC1:1HNO3 GAP-0011 Cleaning GaP 1HC1:1HC1O4:6HNO3 GAP-0017 Preferential Ge N HC1 13 GE-0132a Electrolytic, defect Ge GE-0133a X%KC1 x%NaCl shaping Electrolytic, Ge GE-0129e Ge 7HC1:1HNO3:+glycerin Removal/polish GE-0173 GeAs Removal/polish GEAS-OOOlb 2HC1:1HNO3 Removal Au Regia" "Aqua 3HC1:1HNO3 AU-0001 In Removal HC1, cone. IN-0003 InSb Polish INSB-OOOle lHCl:2NaClO3:3H2O INSB-0002d Removal InSb 2HC1:1HNO3 INSB-0014a InSb Preferential #1" xHCl:x0.2 "Etch N FeCl3 InAs Removal INAS-OOOlb 1MHC1 InP Removal INP-0020a HC1, cone. InP Polish 6HC1:1HNO3:6H2O INP-0021a InP Preferential INP-0021b 40HCl:80HNO3:lBr2 InP Selective INP-0035 3HC1:1H3PO4 IR-0001 Ir Removal 3HC1:1HNO3 "Aqua Regia" Fe Preferential FE-0103b 45HCl:5HNO3:40MeOH Fe thin FE-0104 Electrolytic, HaO4:HAc Cleaning Fe FE-0108 1HC1:1H2SO4:1H2O Fe:Si Electrolytic, form xHC104:xHAc FESI-0007 Fe.Be Electrolytic, thin FEBE-0001 20HCl:20HNO3:60MeOH PbS Dislocation 1HC1:3 PBS-0001 Thiourea PbZrO3 Polish HC1, cone. PBZO-OOOla Mg cutting saw Acid MG-0001 xHCl:xH2O FE-3001 Preferential Fe3O4 1HC1:5H2O MnO2 Removal MNO-0002 HC1, cone. Cleaning MO-0013b Mo cone. HC1, Removal xHCl:xHNO3 Mo MO-OOOlg MO-0008a Polish Mo Regia" "Aqua 3HC1:1HNO3 Preferential HgSe HGSE-OOOlb 1HC1:1HNO3 Polish HgSe HGSE-OOOla 1HC1:50HNO3:10HAc: 20 10WH2SO4 Polish HGTE-OOOla 1HC1:6HNO3:1H2O HgTe HGTE-OOOlb Preferential HgTe 1HC1:1HNO3 defects HGCT-0001 Stain, HgCdTe 1HC1:1HNO3:1H2O Clean NI-0004b Ni 10HCl:33HNO3:67H2O NICR-0003 Removal Ni:Cr 3HC1:1HNO3 "Aqua Regia" © 1991 by CRC Press LLC

290 277 Ref. Use Material Formula Ni:Cr Preferential NICR-0004a 45HCl:5HNO3:50MeOH NB-0004a Cleaning Nb xHCI:xH2O OS-OOOlb Removal Os 3HC1:1HNO3 "Aqua Regia" PD-0001 Cleaning Pd "Aqua 3HC1:1HNO3 Regia" PT-0001 Pt Removal 3HC1:1HNO3 "Aqua Regia" PtSb2 Preferential PTSB-OOOla 1HCI:1HNO3 Removal PTSB-0002 PtSb2 1HC1:1HNO3:1H2O Cleaning "Aqua 3HC1:1HNO3 Regia" QTZ-0003 SiO2(Qtz) Ru "Aqua Regia" 3HC1:1HNO3 RU-0001 Removal Polish HC1, SC-OOOla cone. Sc xHCl:xHNO3 Sc SC-OOOlc Removal Si 1HC1:3HNO3 SI-0171 Defect SI-0186a Electropolish Si xKF:xKCl:2H2O SI-0017 Si Cleaning HC1, cone. Cleaning SiO2 SIO-0038b 4OHF:37HC1 Cleaning 3HC1:1HNO3 Regia" SIO-0051 "Aqua SiO2 Cleaning Si3N3 Regia" "Aqua 3HC1:1HNO3 SIN-0016 ml HCl:100 Cleaning/pin-holing 10% CrO3 500 Si3N4 ml SIN-0018 AGCL-0003 Cleaning AgCl cone. HC1, NaCl (100) Polish, NACL-0002b NaCl, sat. sol. 70HCl:30H2O (100) NACL-0005 Polish, NaCl 1HC1:50HAc:1H2O: (100) Preferential, NaCl NACL-0007a sat. sol. lFeCl3 1HC1:1H2O Steel Preferential ST-OOOla Preferential Steel HC1:1 5 g picric ml ml 100 acid: ST-OOOle EOH 1HC1:2HNO3 Cleaning/removal Steel ST-0007b Steel 4HC1:1HNO3 Removal ST-0007a SrF2 SRF-0001 Removal 1HC1:1OH2O Polish TaN Regia" "Aqua 3HC1:1HNO3 TAN-0001 Te Preferential lHCl:lCrO3:3H2O TE-OOOlc Te Polish 3HC1:1HNO3 "Aqua Regia" TE-0002 Tl slow Removal, HC1, cone. TL-0004 Th 3HC1:1HNO3 Regia" "Aqua Polish TH-0002 (100) Sn 100 ml HCl:10NH4NO3: Defect, SN-0002a 500H2O:xCuSO4 SN-OOOla Sn X5%HC1:XIPA Removal Sn Regia" "Aqua 3HC1:1HNO3 Preferential, (100) SN-0005b 20HClO4:70HAc Sn Electropolish SN-0007 SNO-OOOlb SnO2 1HC1:5H2O Electrolytic, removal Ti x20% Cleaning HC1 Ti-OOOla Ti HC1, Removal cone. TI-0004c TiO2 Regia" "Aqua 3HC1:1HNO3 TiO-0004 Cleaning W Regia" "Aqua 3HC1:1HNO3 Removal W-OOOld Polish xHC1O4:xH3PO4 W W-0018b V Removal Regia" "Aqua 3HC1:1HNO3 V-0002a ZN-OOOla Zn Removal 1HC1:1H2O Preferential ZNS-0002c ZnS 1HC1:1HNO3 Preferential "Aqua Regia" 3HC1:1HNO3 ZnTe ZNTE-0005b © 1991 by CRC Press LLC

291 278 CRC of Metal Etchants Handbook Material Use Ref. Formula ZnTe Polish ZNTE-0002c 3HC1:4HNO3 Removal Zr ZR-0007 Regia" "Aqua 3HC1:1HNO3 ZRO-0002 Electropolish ZrO 1HC1O4:9HAc REGIA AQUA originally developed in This Middle Ages of Europe as 3HC1:1HNO3 solution was the the time, was thought to be a universal etchant for all and, It was the first at materials. capable dissolving gold, in addition to the Platinum Group metals: Pt, Os, Rh, solution of to course, those time it has been found not Of be the ultimate etchant, but is in Re. since on a number of metals and metallic compounds . . . as the 3:1 mixture . . . with use today other constituent to include water dilution and other chemical additives — applied variations, cleaning, general polishing, or preferential depending upon the material. for removal, there chrome two other ''regia" termed formulations: (1) addition, regia, with In are regia replacing and (2) glyceregia, where aqua HNO3, is diluted with glycerin. CrO3 the Any solution containing nitric acid and glycerin should Note: handled with extreme be care it is the precursor of nitroglycerin. CAUTION: HNO3:MeOH, red fuming, was ... shown of first rocket fuels, and can one explosive. These two regia etchants are the at be the of the following list end aqua regia and its varieties. of Although aqua regia has been shown in the previous "Chlorine Containing . . . " list, it is that it would be useful to present the following list covering both aqua regia and felt metallic variations, to a number of metals and applied compounds. The use of aqua its as and its variations is not limited to the materials as shown. An example: if AgCdTe2 regia be though so could AgTe2. . . can we have no reference available for the latter. etched, that a polish etchant can be Note general removal etchant; whereas, a removal etchant a types, is a polish etchant. Also, both necessarily can be used for pattern etching of thin not films and/or structure etching through a mask, e.g., pits, channels, etc. The preferential etchants can general defect development or for a specific type dislocation, such as be for passivation, faults. regia is used for surface aqua it can be either chlorination stacking Where oxidation, and these factors apply to other etchant solutions. or Aqua and variations regia Use Ref. Material Formula Step-etch "purple AlxAu, AIAU-0002 3HCl:llHNO3:10H2O plague" Preferential Al:Si 5HC1:1OHNO3:84H2O ALSI-0003 ALSB-0002a Preferential/polish AlSb 4HC1:3HNO3 Polish/macro-etch AlSb ALSB-0003/ 1HC1:1HNO3 0006 Polish BI-00145 Bi 1HC1:2HNO3:3H2O B1SB-0002 BiSb Polish 20HC1:1NH03 BISE-OOOla Bi^ Polish 1HC1:2HNO3 BITE-0002 Removal Bi2Te3 1HC1:12HNO3 Preferential Bi2Te3 BITE-OOOla 1HC1:2HNO3:6H2O BRO-0001 Removal Bronze 5HCl:1000HNO3 BRA-OOOlb Removal Brass 4HC1:1HNO3 CDISE-OOOla Polish CdlnSej 4HC1:1HNO3 Preferential CDSF-OOOla CdSe 1HC1:1HNO3 © 1991 by CRC Press LLC

292 279 Ref. Material Use Formula Cleaning CDSE-0002b CdSe 3HC1:1HNO3 CDSE-0005b CdSe Preferential 3HC1:1HNO3 CDSE-0003 Polish CdSe 3HC1:1HNO3:12H2O CDSE-0006 Removal CdSe 5HC1:1HNO3 CdS CDS-OOOlb Preferential IHC1:1HNO3 CdTe Polish CDTE-0006d 2HC1:2HNO3:1H2O CdTe Preferential CDTE-OOllb 1HC1:1HNO3 Polish CDTE-0018b CdTe 3HCl:lHNO3:lHAc CdTe:HgTe Polish CDHT-0001 1HC1:6HNO3 CaWO4 Preferential CAW-OOOlb 3HC1:1HNO3 Polish CaWO4 CAW-0002 3HC1:1HNO3 Cu2O Removal CUO-0019 10HCl:1000HNO3 Polish CuGaSej CGSE-0001 3HC1:1HNO3 CuInSe2 Polish/stain 3HC1:1HNO3 CISE-0001 Polish CuInSe2 CISE-0002 1HC1:1HNO3:1H2O Removal CuGaTe2 CGTE-0001 1HC1:1HNO3 Thinning curr-oooib CuInTe2 1Hc1:1HNO3:2H2O Preferential Apatite FAP-OOOla 3HC1:1HNO3 Preferential Ga GA-0002 3HC1:1HNO3 GaAs Polish GAS-0052 1HC1:2HNO3:2H2O Polish GaAs GAS-0044d 3HC1:3HNO3:2H2O Polish GaAs 3HC1:1HNO3 GAS-0056a GaAs GAS-0057 Preferential 2HC1:1HNO3:2H2O GaAs Polish/junction GAS-0056c 5HC1:1HNO3 Polish GaAs 2HC1:3HNO3:2HF GAS-0005a GaAs Removal 1HC1:2HNO3:1H2O GAS-0140d GaAs Preferential GAS-0167c 1HC1:1HNO3:2H2O GASB-OOOlc GaSb 1—2HC1:1HNO3 Removal passivation GaSb Surface 30HCl:lHNO3 GASB-0007b Polish GaP GAP-0002 1HC1:2HNO3:1H2O Polish GAP-0008 GaP 2HC1:1HNO3:2H2O GAP-0011 Selective GaP 3HC1:1HNO3 Cleaning 3HC1:1HNO3 GaP GAP-0012 GaP Cleaning GAP-0017 1HC1:6HNO3:1HC1O4 3HC1:1HNO3 Preferential GAP-0022b GaP Dislocation GaP + Ag/Fe 1HC1:1HNO3 GAP-0022e GE-01773 Ge Removal/polish 7HC1:1HNO3: + Gly GeSn GESN-0001 3HC1:1HNO3 Removal GeAs Removal, slow GEAS-OOOlb 2HC1:1HNO3 Glass:PdNiP Clean/removal PDNP-0001 2HC1:1HNO3 Au 3HC1:1HNO3 Removal/pattern AU-OOOla Cleaning AU-0003b 3HC1: Au lHNO3:20—50H2O Au:Cs Removal 3HCl:lHNO3:xH2O AUCS-0001 InSb 1—5HC1:1HNO3:4—6H2O INSB-0001b,d Polish/preferential Polish InSb 2HCl:5HNO3:4HAc INSB-OOOlc INSB-0004 InSb Polish 2HC1:2HNO3:3H2O/25H2O INP-0020b InP 1—2HC1:1HNO3 Removal Polish InP INP-0021a 6HC1:1HNO3:6H2O Preferential InP 40HCl:80HNO3:lBr2 INP-0021b InP Selective INP-0062g 1—2 HC1:1—2HNO3 © 1991 by CRC Press LLC

293 280 of Etchants Handbook CRC Metal Formula Use Material Ref. 1HC1:3/1.5/2/2.5 HNOj InP Selective/step-etch INP-0064a,k InP Polish IHCI.IHNO3 INP-0070 Ir/IrV 3HC1:1HNO3 Removal/patterning IR-0001 Preferential Fe 45HCl:5HNO3:50H2O FE-0003b Dislocation Fe FE-0011 10HCl:lHF:5HNO3 Electropolish Fe 1HC1:1HNO3:2H2O FE-0030 lHCl:lHN03:3Me0H Fe:Be Electro-clean FFBE-0001 MgTe 1HC1:1HNO3 Removal MGTE-0001 10 AT HgSe 1HC1:50HNO3:10HAc:20 Polish HGSE-OOOla H2SO4 HGSE-OOOlb HgSe Preferential 11HC1:1HNO3 6HC1:2HNO3:3H2O HgSe Preferential HGSE-OOOlc Polish HgTe 1HC1:1HNO3:1H2O HGTE-OOOla HgTe 1HC1:1HNO3 Preferential HGTE-OOOlb HgCdTe Defect/strain 1HC1:1HNO3:1H2O HGCT-0001 HgCdTe Preferential HGCT-0002a 2HC1:1HNO3:3H2O Mo Removal xHCl:xHNO3 MO-OOOlg Polish Mo 3HC1:1HNO3 MO-0008a Mo Cleaning MO-0010 1HC1:1HNO3 Removal Mo xHCl:xHNO3:xH2O/MeOH/EOH MO-0022b Removal Fe2Mo3O8 1HC1:2HNO3 FEMO-0001 MoS2 Removal MO-0004 3Ha:lHNO3:5H2O Ni Removal NI-0005 4HC1:1HNO3 NI-0004b Cleaning Ni 10HCl:33HNO3:67H2O PMA-OOOla Permalloy Polish 3HC1:1HNO3 Nichrome 1HC1:1HNO3:3H2O Removal/cleaning NICR-0006 Nichrome Removal 3HC1:1HNO3 NICR-0003 Preferential 45HCl:5HNO3:50MeOH Nichrome NICR-0004a Removal RENi2 REN-0001 4HC1:1HNO3 Os OS-OOOlb Removal/cleaning 1HC1:3HNO3 Pd Removal/cleaning PD-0001 3HC1:1HNO33H2O PdAg Removal/cleaning PDAG-0001 3HC1:1HNO3 PdAu Removal/cleaning 3HC1:1HNO3 PDAU-0001 Cleaning Pd:H 3HCl:lHNO3:xH2O PDH-0001 Removal/cleaning 3HC1:1HNO3 Pt PT-0001 Pt:Pd Preferential/removal 3HCl:lHNO3:xH2O PTPD-0001 Pt:Au Preferential/removal 3HCl:lHNO3:xH2O PTAU-0001 Cleaning Pt:Rh 3HC1:1HNO3 PTRH-0001 PeH Cleaning 3HCl:lHNO3:xH2O PTH-0001 PtSb2 PTSB-OOOla-b Preferential 1HC1:1HNO3:xH2O SiO2 Cleaning (Qtz) 3HC1:1HNO3 QTZ-0003 RH-0001 Rh Cleaning 3HC1:1HNO3 RU-0001 Ru Removal 3HC1:1HNO3 Sc xHa:xHNO3 Removal SC-OOOlc TiWSi2 3HC1:1HNO3 Removal TWSI-0001 SI-0108a Cleaning Si 1HC1:1HNO3 Cleaning Si SI-0108C 3HC1:1HNO3 Cleaning SiO2 3HC1:1HNO3 SIO-0052 Cleaning Si3N4 3HC1:1HNO3 SIN-0007 Removal 1HC1:1HNO3:1H2O AG-0007 Ag © 1991 by CRC Press LLC

294 281 Use Ref. Material Formula Pb:Sn:Ag 1HC1:3HNO3:6H2O AGPS-OOOlb Removal/cleaning Polish SAT-0001 AgSbTe2 1HC1:1HNO3: AgFeTe2 Polish SIT-0001 sat. sol. 2K2S2O7, ml 300 Steel, HC1:1O ml HNO3: 10 ml Electrolytic ST-OOOli 15 HAc:5 ml glycerin ST-0007a (hi-speed) Removal Steel 4HC1:1HNO3 ST-0007b hard Steel, Removal/cleaning 1HC1:2HNO3 TaN Polish 3HC1:1HNO3 TAN-0001 Te Removal/polish TE-0002 3HC1:1HNO3 Te Polish 3HC1:1HNO3:1H2O TE-0008 Th Polish 3HC1:1HNO3 TH-0002 Sn 3HC1:1HNO3 Preferential SN-0005b SnTe 20K2Cr2O7, 11HC1:1HNO3: sat. sol. Polish SNTE-0001 Cleaning TIO-0004a TiO2 3HC1:1HNO3 TiW 3HC1:1HNO3 Removal TIW-0006 W Removal 3HC1:1HNO3 W-OOOld V Removal V-0002a 3HC1:1HNO3 Preferential 1HC1:1HNO3 ZnS ZNS-0002b ZnTe Preferential 3HC1:1HNO3 ZNTE-0005b Polish ZnTe 3HC1:4HNO3 ZNTE-0002c 3HC1:1HNO3 Zr Removal ZR-0007 Zr2Pd Polish/removal ZRPD-0001 3HC1:1HNO3 Zr3Rh 3HC1:1HNO3 Polish/removal ZPRH-0001 Chrome regla Preferential Au AU-0017 (10—20%) 3HC1:1CiO3 Si Preferential SI-0019 5HCl:lCiO3(10%) Preferential Si3N3 SIN-0002e 5HCl:lCrO3(10%) Polish AG-0012b ml gCrO3:50 O.5HC1:5 H2O Ag Preferential AG-0012c H2O 0.01HCl:5 ml gCrO3:25 Ag Preferential Ta TA-OOOlc lHCl:lCrO3:3H2O Polish/acid saw cut TA-0002a-b Ta lHCl:lCrO3:lH2O cut saw Acid Te lHCl:lCrO3:3H2O TE-0012a Te Polish TE-OOOlc 1HC1:1CiO3:3H2O Removal 3000 6 N HC1:2O g Cr, ml metal SNO-0005 SnO2 Glyceregia Macro-etch/cleaning ST-0018 HCl:10 ml HNO,: 30 ml Steel 20—50 ml glycenn 7HCl:lHNO3:x glycerin Ge GE-0173 Polish/removal GaAs Preferential glycerin 1HC1:1HNO3:8 GAS-0050 PbAg 1HC1:1HNO3:4 Preferential glycerin PBAG-0001 PbSn:PbTi CHLORINE, Cl2 General: Chlorine gas is too active to remain in the free state although it can be a immediately temporary of volcanic eruptions which product converts to hydrochloric acid, © 1991 by CRC Press LLC

295 282 CRC of Metal Etchants Handbook Sulfur also a volcanic by-product, converting to sulfuric acid, H2SO4. These two HC1. is the primary acid producers in the atmosphere whether from volcanic gases are corrosive industrial that Acid rain is one result, another is smog. Note as smog action or pollutants. existence since ancient times. has been in minerals, form to compounds as natural many such as combines Chlorine metallic (horn silver). Probably the best known and one of the most widely used cerargyrite, AgCl halite, is (sodium chloride) as common salt, and "sea salt", the mineral compounds NaCl common The as a dietary replacement for used salt. Man has extracted KC1. latter sylvite, oceans since ancient times by evaporating sea water salt shallow basins — the from in is used — though both salt and sulfur still mined in quantity, today, from salt method are or similar domes domes, and from tremendous salt beds buried in the earth from the sulfur evaporation ancient shallow seas that go back in age for millions of years. of chloride, as is one of the most important — and abundant — minerals Sodium halite, world. chemical is a major material in the the industry, used as a concentrated brine in It the processing, well as being separated for as sodium metal content and gaseous in metal Chlorine is a greenish-yellow gas with a disagreeable smell, chlorine. is extremely and irritating membranes of the nose, eyes, and throat. Dispersed in the air as a cloud, usually to HC1, recognized a heavy white vapor, it is easily as by its astringent action. It can liquefy as of at only 6 atm of pressure, and was one under die first gases to be liquefied. With 0°C added water and cooled with ice, it will form a highly unstable greenish-yellow crystalline hydrate. The will combine to form compounds with most elements, other than oxygen, gas or carbon, there are many industrial uses for both metallic sodium and gaseous nitrogen, and latter of the production the hydrochloric acid. chlorine; in mixture usually gas, with water, as a in of hydrochloric and hypo- The combination acids yields oxygen in a highly active state. Hypochlorous acid, HC1O is bleach. chlorous used released a disinfectant, the When oxygen kills bacteria. Perchloric acid, HC1O4, is as acid, powerful used as a replacement for nitric agent, HNO3, in etch solutions. a oxidizing is not an oxidizer in dilute solution and its perchlorate It are the mostly stable salts of salts the of chlorine. oxy-acids under Application: chlorine Technical been used Pure pressure as an electrolytic gas has jet etch, or bubbled through an etch solution as part of the reaction process in Solid State device fabrication. acids of as mentioned in the General section above, and shown in the chlorine, The containing of materials with formulas of chlorine A—Z etchants have wide list preceding in metal and metallic compound processing usage liquid acids. as In using the chlorine as a cleaning gas, hydrochloric acid is used in epitaxy addition, in and other chloride compounds have been several use as doping element carriers systems, in semiconductor diffusion for several years. Phosphorus oxy-chloride, POC13 (pockle) for n-type phosphorus; trichloride, BC13, as a gas, for p-type boron, or as dry chemical boron thin (DCE) the selective etching of in film aluminum for patterning structure. etching The following list of chlorine etchants includes growth as a single crystal for morpho logical studies. Etching: N/A CHLORINE ETCHANTS CL-0001 ETCH NAME: Pressure TIME: TYPE: Pressure, preferential TEMP: COMPOSITION: x ... pressure © 1991 by CRC Press LLC

296 283 DISCUSSION: grown as single crystal in vacuum and under cryogenic temperature and pressure Cl2 a of etch by varying vapor pressure surfaces the vacuum. Preferentially crystal conditions. N et al — Rare Gas Solids, Vol 3, Academic Press, New REF: 1970 Schwentner, York, CL-0002b Chlorine TIME: ETCH NAME: etching RT to hot Gas, TYPE: TEMP: COMPOSITION: ... x Cl2 x ... acid solutions DISCUSSION: as gas bubbled through an acid solution has been used to create Cl2, a stirring and/ both or action. etching Ibid. REF: CL-0002a Hydrochloric TIME: 1—5 min ETCH acid NAME: cleaning TEMP: TYPE: 1200°C Gas, 800— COMPOSITION: x ... HC1, vapor DISCUSSION: as hot vapor with dissociation of H2 and Cl2 with the HC1, chlorine vapor used for acid general action in epitaxy systems. This includes cleaning of the quartz tube, graphite cleaning such plate, materials to be epitaxially deposited, and as silicon (111) wafer sub susceptor strates for Si, Ge, GaAs thin film growth in device fabrication. REF: Walker, et al — personal application, 1970—1985 P CL-0003 ETCH TIME: NAME: Chlorine gas TEMP: Electrolytic, jet TYPE: COMPOSITION: ANODE: Cl2 x ... CATHODE: ... H2O POWER: x DISCUSSION: gas used as a jet under pressure for electrolytic Cl2 of etched holes in germanium forming wafers. Germanium section for reference. See REF: CL-0004 NAME: Chlorine water TIME: ETCH Acid, TEMP: TYPE: RT disinfectant COMPOSITION: x...C12(HC1) x ... H2O DISCUSSION: Cl2, as gas dissolved in water . . . chlorinated water, chlorine-water. Used as a general disinfectant in for cleaning metal surfaces, and in drinking water to kill bacteria. water, a gas Pure used, but more often HC1 or can dry chemical chlorine compound, such as a be hypochlorate, is used. As a very dilute solution of HC1 it is used in medicine for human consumption an acidifier. as REF: Roe, J H — Principles of Chemistry, 7th ed, C V Mosby, St Louis, MO, 1950 © 1991 by CRC Press LLC

297 284 CRC of Metal Etchants Handbook PROPERTIES PHYSICAL OF CHROMIUM, Cr Classification Transition metal Atomic number 24 Atomic weight 52 Melting point (°C) 1875 (1890) (°C) point Boiling 2582 (g/cm3) Density 7.2 (cal/sec)(cm2)(°C/cm) conductance Thermal 0.16 25°C (cal/g) heat Specific 0.11 of heat Latent (cal/g) fusion 21.6 (k-cal/g-atom) Heat of fusion 3.3 (k-cal/g-atom) vaporization of Heat 76.635 Atomic volume (W/D) 7.23 1st ionization energy (K-cal/g-mole) 156 ionization (eV) potential 1st 6.76 (Pauling's) Electronegativity 1.6 (angstroms) Covalent radius 1.18 (angstroms) radius Ionic 0.63 (Cr+3) linear expansion Coefficient of thermal 6.2 (xl0-6cm/cm/°C)20°C Electrical resistivity (micro-ohms-cm) 12.9 x 10~6) (emu susceptibility Magnetic 3.6 (eV) function work Electron 4.37 section Cross (barns) 3.1 (°C) pressure Vapor 2139 — scratch) Hardness (Mohs 9 (Knoop load) g 100 — 700—1200 — kgf mm~2) (Knoop) 940 structure Crystal normal) — (isometric (100) cube bcc (solid) Color Steel grey/silvery poor) (cubic Cleavage — (001) CHROMIUM ETCHANTS CONTAINING chromium compounds are used as the oxidizing agent in a number of etch Several Two dioxide, used are chromium solutions. CiO3 and potassium dichromate, K2Cr2O7, widely acids. used both as an additive to other alone In another instance, metallic chromium is or added to solutions. Such solutions have been used on a wide range of metals and metal compounds in to oxides and nitrides as surface cleaners to remove contamination, addition polishing, thinning, as preferential or dislocation etchants. for and + be that the should and chromous ions—Cr noted + and Cr+ + + are extremely It chromic and difficult to remove from surfaces even tenacious prolonged and heavy water with washing. is particularly true in cleaning quartz and glassware with the standard "glass This shown solution H2SO4:K2Cr2O7. It has been of that quartz diffusion tubes etched cleaner" in the glass cleaner still contained traces of chromium ions even after 3 days of heavy water washing. This due to chromium's affinity for oxygen forming Cr2O3 and other Cr-com- is surfaces. in final rinse of glassware plexed a "chrome etch" solution containing either A is ammonium or sulfate at 30—40°C nitrate recommended where subsequent diffusion eerie can contaminate parts with chromium which, in turn, can degrade the eventual electrical characteristics a device. of There are nearly 100 etch solutions shown in this Etchant Section that contain chromium, the about being preferential/dislocation types and half other half polish/removal, all used © 1991 by CRC Press LLC

298 285 for structuring. As has been mentioned previously, many etchants are named thinning or developer after is particularly true for the dislocation etchants containing and their this etch, circa have formulated for silicon. Sirtl's initially 1962, was one that chromium been first and, over the years, several modifications of the Sirtl etch have of introduced the been specific of particular types of dislocations and defects. Such named chro for enhancement preferential Schimmel, are Secco, containing, Wright, Erhard's, and others. mium etchants formulated "chrome commercially mixed, was available for controlled re The etch", of chromium and chromium oxide, initially, for the processing of chrome glass masks moval used (CGMs) and is not included in the following "Chromium Con in photolithography, Chrome the has already been listed under Etchants*'. "Chlorine Containing taining regia Etchants". of a selected list of some The the more prominent etchants containing following is as applied to metals and compounds. Additional solutions are shown under their chromium materials. individual Use Ref. Material Formula Cleaning AL-0032 Al sat. 27H2SO4:70H2O;3Na2Cr2O7, t sol. AL-OOOla removal Oxide A12O3 35mlH3PO4:20gCiO3/l BTE-0001 Preferential B2Te3 K2Cr207 M 0.5 Matte BRA-0008b finish/clean Brass H2SO4:4 ozNa2Cr2O7:l gal 12 oz H2O CDS-0007b Preferential CdS 5 ml ml gCr2O5:1250 H2SO4:i H2O CDTE-0006a E Etch CdTe Polish 10mlHNO3:10mlH2O:4g K2Cr2O7 CDTE-0006b Dislocation CdTe etch:5 AgNO3 mg 10 ml E CAW-0003a Polish CaWO4 sol. 3H3PO4:lCrO3, sat. C-0006b Removal (dissolves) Cu xH3PO4:xCrO3:xNaCN CU-0017 Cleaning Cu 6H2SO4:12CrO2:82H2O CU-0027b Oxide removal/matte Cu gal oz 12 Na2Cr2O7:l H2SO4:4 oz H2O GAS-0041 GaAs Polish \N 17JVHAc:l 12WHC1:1 1 K2Cr207 GAS-0059 Dislocation A/BGaAs g mg CrO3:8 HF:2 1 ml H2O:1 ml AgNO3 GE-0040 Electrolytic Ge Ag mg Cr2(SO4)3:2 M 0.5 GETE-0001 Polish GeTe sat. sol. lHNO3:20K2Cr2O7, Electropolish AU-0009 Au g K2Cr2O7, sat. H2SO4:100 ml 1000 sol. TE-OOOlc Preferential Te 1HC1:1CiO3:3H2O FE-0012b Electropolish Fe/Ni xHAc:xCiO3:xH20 SI-0039 Preferential Si lHF:2CrO3(33%) etch Sirtl SI-0017 Preferential Si CrO3:1.5H2O 2HF:1 0.75 M Schimmel SI-0036 Preferential Si K2Cr2O7 Secco 2HF:1 M 1.15 Preferential Erhard's 1HF:1CiO3(%?) SI-0158 Si Preferential Si SI-0045 g/l):30HNO3: 60HF:30CrO3(l g Cu(NO3)2 60HAc:60H2O:0.2 Wright Preferential SI-0132 Si Syer 1HF;1CiO3(38%) Cleaning SI-0066b Si 1% NajCrA Ta Cleaning TA-0003a xH2SO4:xK2Cr2O7, sat. sol. © 1991 by CRC Press LLC

299 286 CRC of Metal Etchants Handbook Ref. Use Material Formula sat. lHNO3:llHCl:20K2Cr2O7, SnTe sol. Polish SNTE-0001 HBr:20 Cr:20 g 1 H2O ml ml Removal SNO-OOOla SnO2 U ml 300 HAc:30 ml CiO3 g H2O:25 Electropolish U-0002a U xHNO3:xCiO3:xA12O3 powder polish and Lap U-0002e H3PO4:120 ml H2SO4:310 ml ml 67 Polish UC UC-0001 CeO3 g H2O: 78 CrO3:5 Zn H2O g NaSO4:15 g g 16 Polish ZN-0008c ml H2O CrO3:500 g Zn 160 Preferential ZN-0009 ZNSE-OOOlb ZnSe 40H2SO4:60K2Cr2O7, sol. sat. Cleaning ZNS-OOOla ZnS N K2Cr207, sol. H2SO4:5 sat. M 16 Preferential ZnS Dislocation 0.5 M K2Cr207 ZNS-0002 ml H2SO4:300 ml K2Cr207, 1000 Cleaning SiO2, Qtz SI- sol. sat. Si3N4 cleaner Glass Cr CHROMIUM, There occur as General: native element. Does are some eight minerals containing not a several lead chromates, but the primary ore is the mineral chromium, FeCr2O4. chromite, The is variable as iron can be replaced with magnesium, and chromium with formula As the chromium, it is one of the hardest known metals (H = 9), and is aluminum. pure under atmospheric conditions. stable normal extremely metals industry chromium ore is reduced as an iron alloy In ferrochromium the called ferromanganese ferrosilicon) and, this alloy added and iron, produces stainless steel (like to and other special steels. It is (SST), hardening agent in both iron and other metal alloys. a The can be easily plated electrolytically and is best known as chrome plate. It metal on a thin film coating that can forms highly polished, and has long been used hard be vehicles bumpers, trim, and engine parts. — vertical RF plasma sputter systems have Large, been used for chrome plating of razor blades. Such a system has a vertical, central rod of chromium and, a single sputter cycle, thousands of blades are racked around the inner for facing the which can be 4 ft long and an inch or more in diameter. Many small barrel rod tools by chrome plated electrolytically or and RF sputter for general surface parts are wear resistance. protection or chromates such the potassium salts, sodium as are highly colored and Chromium and active oxidizers. Used as reducing agents to produce chromium hydroxide, extremely Cr(OH)3, they "chrome tannage9' as used in the treatment of leather goods, chiefly gloves of calf are as called kid. Because of their brilliant yellow color, some salts are skin "chrome glazed enamels. and as a paint pigment, yellow" in some special glasses, ceramics, and used and Potassium mixed with sulfuric acid dichromate a deep yellow/red solution that produces turns coal black with usage. It has long been referred to as the "glass cleaner" solution, and used clean laboratory glassware. Caution should be observed in handling as it is an to Sulfuric active to include human skin. solution, acid can react violently extremely oxidizing water, particularly when hot — always slowly with sulfuric to water; not water to add sulfuric. uses Application: chromium has several Technical Metallic in Solid State and important semiconductor processing. It is a dopant element in some compound semiconductors, but a primary use in thin film, multilayer metallization as the initial evaporation metal on a is are highly where gold, platinum, and palladium surface used as the top metal. The polished precious metals do not adhere well to polished surfaces as they are extremely inert to high oxidation; the other hand, chromium has a on affinity for oxygen, also alloys readily © 1991 by CRC Press LLC

300 287 with other metals and compounds, such that it is an excellent tie-down metal as a thin most Chromium evaporates the solid phase, not becoming liquid, but going directly film. from gas to it sublimes — and redeposits as a crystalline structure. Because of this phase the — like other lapped rough surface, surface, metals adhere well. As a rough crystalline a pads has a general standard for metallization been and there are Au/Cr multilayer, long as Pd/Cr, Pt/Cr or others, Au/Pt/Cr, etc. such Au/Pd/Cr, chrome either a tungsten rod plated with chrome is used as a one-shot, In evaporation, or boat chrome pieces/powder in a tungsten source is the source. In either throw-away chunk the after subsequent exposure to air (oxygen), with surface will oxidize to green case, use, trioxide, Cr2O3, such that, if the source is to be re-used, it requires heavy chromium out- gassing remove the oxide before further metallization. If not sufficiently out-gassed, the to evaporated layer be a thin film of resistive, glassy trioxide. initial will patterning, evaporated glass blanks are chromium photolithographic (ap For soda-lime mask. A 2000 the chrome photo resist thick) They commonly have an anti- proximately — (AR) coating — oxygen introduced into the evaporation bell jar to form an oxide reflective about (tan A thick layer color) after chromium has been evaporated, and before opening 400 brilliant bell AR coatings have been deposited up to Such first order blue or carmine the jar. These chrome glass masks with or red. AR coating have been used as mirrors in a without variety processing applications. One interesting of for a chrome glass plate application without AR coating is for a permanent fingerprint identification system. Skin oils act as a mask and on chrome, and very clear fingerprints can be developed by light etching activator a ceramic nitrate/sulfate solution. This was developed by these authors and, in ammonium used for present, is a viable approach not better definition than inking. though at (VT) ingots chromium using a Vapor Transport of growth method with an High purity atmosphere gas carrier are supplied commercially as a mass of solid chromium iodine not Some single crystal. crystallites, of the larger, individual crystals, which are single a study units out for morphological chipped of the metal. crystal have been Easily in HC1 or dilute HNO3, or H2SO4. "Chrome Etch" is eerie Etching: ammonium nitrate sulfate. or ETCHANTS CHROMIUM CR-OOOla ETCH NAME: Hydrochloric acid TIME: Acid, TYPE: TEMP: RT removal COMPOSITION: x ... HC1, cone. DISCUSSION: Cr, thin film deposits as a plated surface coating. Solution used to develop cracks in a study of chromium surfaces. CrH will crack subsurface bulk Cr, and cracks propagate brittle corrosion stress. by and Smith, W H — Acta Me tall, 103,51(1956) REF: Walker, application, — personal CR-0002a 1960—1980 P metal evaporation build-up Cr, vacuum glass and film bell jars or internal fixtures. on Remove parts, soak in solution, and scrub with a SST brush. Black smut remaining can be and removed and wiping with toweling. Can be used on steels, glass, ceramic, water with copper parts. Nichols, D R CR-0017a: Solid State Technol, December 1979 — Cr, evaporation deposits in vacuum systems. Solution used for cleaning of bell jars and maintenance fixtures. This is an excellent article on the {Note: and cleaning of metal vacuum evaporator systems.) © 1991 by CRC Press LLC

301 288 CRC of Metal Etchants Handbook CR-0002b ETCH acid, dilute TIME: NAME: Hydrochloric removal TYPE: TEMP: Acid, RT COMPOSITION: HC1 ... 1 H2O 1—20... DISCUSSION: deposits in vacuum systems and crystalline chrome pieces. Cr, so evaporation Dilute 1:1 1:5 used to clean vacuum base plates to bell jars without removal from the lutions and Soak heavy toweling with solution system. soak/scrub surfaces. In chrome glass mask and fabrication 'dusting" from chromium particles can be a major cause of film pin-holing and, * eight fixturing ten evaporation runs per day, with may require cleaning on a daily basis. to chromium breaking large chunks of high purity down for use as an evaporation After source, pieces were soaked in the more dilute solutions, DI water washed, and dried under an IR lamp. Ibid. REF: CR-0003 TIME: ETCH NAME: Acid, removal TEMP: RT TYPE: COMPOSITION: HC1 3 ... 1 ... H2O2 DISCUSSION: specimens. Referred to as a general Cr for chromium. etch REFS: Catalogue, MRC (1984) Metals CR-0017b ETCH TIME: NAME: Acid, cleaning TEMP: RT TYPE: COMPOSITION: 1 ... HC1 1 ... glycerin DISCUSSION: Cr, as evaporated deposits in vacuum systems. Solution used to remove chrome deposits from stainless glass, ceramic, and copper parts. Do not use on iron. steel, Ibid. REF: CR-0017c NAME: TIME: ETCH Acid, TEMP: TYPE: RT cleaning COMPOSITION: ...KMnO4 5g 7.5 g ...NaOH 30 ml ...H2O DISCUSSION: deposits as evaporation deposits in vacuum systems. Solution used to remove chrome Cr not from glass and ceramic. Do steel, use on aluminum. REF: Ibid. © 1991 by CRC Press LLC

302 289 CR-0005 NAME: TIME: ETCH patterning Acid, TEMP: TYPE: Warm COMPOSITION: ... 453.6 2NH4NO3.Ce(NO3)3.4H2O g 125 H3PO4 ... ml 2500 ml H2O ... DISCUSSION: deposits on glass substrates. Solution used for patterning chrome glass thin Cr, film photo resist masks. {Note: This is one form of the "Chrome masks using eerie as Etch" nitrate. acid can replace the phosphoric.) ammonium Nitric April D al — Semiconductor Int, et 1981, 179—196 Angle, REF: L CR-0006 Chrome TIME: NAME: Variable ETCH etch patterning RT Acid, or 30°C TEMP: TYPE: 22 A/sec RATE: COMPOSITION: g 1 2NH4NO3.Ce(NO3)3.4H2O ... 10 ml ...HNO3 ml ... 100 H2O DISCUSSION: thin evaporation on soda-lime glass used in fabricating photo resist Cr, chrome film without Chrome 2000—2500 A with or thickness a Cr2O3 anti-reflective (AR) glass masks. 400 A thick (light tan color). Without nitric acid, rate was 40 coating Solution A/second. as was used as a patterning etch with intense white light (halogen) flooding the shown Pattern vertical. etch sharply surface. Small, half-moon structures along etched edges, edges to termed defect structures that appear are be related to the chrome/glass "mouse-nips", interface — possibly glass surface defects or due to initial growth nucleation of Cr metal/ Cr2O3 anomalies. diluted to ml and used at room temperature without intense light showed Solution 500 step-etch of A/sec. Solution used as a slow rate in studying the internal structure of a 1—3 chromium deposits and the chrome/glass interface. the black spots were observed Random on glass surface after chrome removal which could be removed with nitric acid, e.g., the black probably or CrO2, both of which form CrO oxides. Low spots in the polished either glass surfaces can contain an amorphous silica smear from surface polishing? Work compared to commercial Etch" (KTI). *'Chrome development, Walker, Tarn, W — personal & Optifilm Co., 1974—1975 REF: P CR-0007 NAME: Chrome etch TIME: Variable ETCH Acid, TYPE: TEMP: 28°C patterning COMPOSITION: 1 ... 2NH4SO4.Ce(SO4)2.2H2O g ml 5 ...HNO3 25 ml ... H2O DISCUSSION: Cr, thin film evaporations on glass substrates used for chrome glass mask fabrication for photo applications. resist Bulletin REF: Rev-HPD/VB/TM/83/lK, MRC Corp., 1975 1116B, CR-0004: Trost, E — personal communication, 1974 used Cr, film evaporation on soda-lime glass thin for chrome mask fabrication. Prefers © 1991 by CRC Press LLC

303 290 CRC of Metal Etchants Handbook ammonium nitrate than die sulfate, as the sulfate can leave a scum on glass eerie rather surfaces. CR-0015 ETCH Chrome etch, variation TIME: 1—2 min NAME: removal TEMP: RT TYPE: Acid, COMPOSITION: g 12 H4NO3.Cd(NO3)3.4H2O ...IN 60ml...H2O DISCUSSION: on deposited by Au.Cr, evaporation thin alumina substrates used in a films E-beam etching study of fine line microelectronic pattern definition. Standard photo resist circuit techniques with 1350J lacquer. After patterning, gold was removed with tri-iodide etch used solution and with commercial "chrome etch" chromium (KTI) to develop the solution the Chromium also removed with the solution circuit. for comparative purposes. Both shown solutions satisfactory for one mil line were with the solution shown etching more definition rapidly. This solution also used for general stripping of chromium from substrates, follow with acid, 1—2 min, DI water rinse 1—2 min, MeOH rinse, and nitrogen blow RT, nitric dry. Walker, — personal application, 1983 P REF: CR-0010 TIME: NAME: ETCH TEMP: Acid, TYPE: removal COMPOSITION: *FeCl3 2 ... HC1 ... 1 *30—35°B6 DISCUSSION: Described as Cr general etch for chromium. specimens. a REF: CR-OOOlc TIME: ETCH NAME: Electrolytic, TEMP: TYPE: polish ANODE: COMPOSITION: CATHODE: 64% ... H3PO4 POWER: ... 15% H2SO4 H2O 21% ... DISCUSSION: a plated coating. Solution used to polish specimens surface film deposits as Cr, thin surfaces. chromium brittle in cracks of study etching with before HC1 a in REF: Ibid. CR-0018 TIME: ETCH NAME: Oxygen TEMP: Gas, oxidation TYPE: COMPOSITION: (2) x ... CO2 ... x (1) O, © 1991 by CRC Press LLC

304 291 DISCUSSION: thin films on glass microscope slides used in a study of chromium Cr, evaporated oxidation. adhesion used a steel stylus with a 0.125 radius to produce parallel Scratch test and gram-weight into underlying glass with different the loads. Cuts vertically scratches cutting transmitted light. Oxidation was done in vacuum under observed back pressure under varied included with H2, Ar and methane in addition to O2 and CO2 to form Cr2O3. treatment and See noted adhesion tenacity increased with time. that SIO-0040 for preparation of was It substrates. (Note: Improved glass with time has been observed on both soda-lime adhesion glass alumina substrates.) and Torkington, R & Vaughn, J G — J Vac Sci Technol, A(3)795(1985) REF: S CR-0019 NAME: plasma TIME: ETCH min 15 RF gas, TEMP: Ionized TYPE: removal FLOW: COMPOSITION: GAS He PRESSURE: 0.5 Torr 68 ... POWER: 100 3O...C12 W 20 O2 RATES: See discussion ... DISCUSSION: Cr, films used as a mask along with PMMA photo resist for photolithographic thin develop patterning. at 150°C, 30 min, and PMMA in 1 MIBK:3 IPA at 22—23°C, Pre-bake 150 sec for a 3000 A PMMA layer. Etch rates were: (1) 35 A/min for PMMA; (2) 110 kl min for Cr. Sewell, H J Vac Sci Technol, 15,920(1978) REF: — CR-0008 NAME: EB-5 TIME: 1—3 min ETCH Kodak patterning TEMP: TYPE: Acid, RT COMPOSITION: x ... NaOH x ... K3Fe(CN)6 DISCUSSION: thin films evaporated on glass as photo masks or on silicon wafers coated Cr, SiO2. with Used an evaluation of different epoxy polymers as E-beam (EB) photo resists. Solution in used chromium etch pattern deposited shown — polybutadiene as photo resist coating to than showed higher sensitivity to EB x KTFR. Develop coating with cyclo- 300 hexanon at 180°C. REF: Hirai, et al — J Electrochem Soc, 118,669(1971) T CR-0016 ETCH Chrome etch, variety TIME: NAME: Acid, patterning TEMP: TYPE: COMPOSITION: 164 ...Ce(NH4)2(NO3)6 g ml ... 42 HC1O4 1000 ml ...H2O DISCUSSION: Cr, evaporated thin films. Solution used to remove chromium films evaporated on glass trisulflde masks. Cr/As2S3/Glass, with the arsenic was used to improve photo Metallization resist pattern definition. After pattern etching chromium with the solution shown, pattern CR-0006). etch As2S3 with 5% NaOH. (Note: See discussion under remove REF: Mednikarov, B — Solid State Technol, 1984, 177 © 1991 by CRC Press LLC

305 292 CRC of Metal Etchants Handbook ALLOYS, CrxMy CHROMIUM not Does nature as metallic alloy compound. There are about a dozen occur General: in the which FeO.Cr2O3 and crocoite, PbCrO4, are chromite, chief chromium minerals of ores. chromium with nickel forms high Industrially, brazing alloys (soldering chromium temperature and above 800°C). There are a wide range of such mixtures as nichromes below, brazing more temperature and are discussed in applications, detail under Nickel Alloys. for specific A is 80% Ni:20% Cr, used Chromel steel brazing, and the same mixture has other names. in As wires — chromel-alumel — it is a widely used thermocouple in the medium paired There range data tables available. power/temperature are several iron/ temperature with alloys as trinary mixtures in addition to other chromium:metal binary nickel/chromium systems. Technical Other than as general brazing alloys in Solid State processing Application: sputter mainly package construction — nichrome is — evaporated as a contact pad and, for as a thin film with photolithographic patterning, used as an etching mask, e.g., silicon via hole and etching with KOH solutions. pit one chromium is shown here, others are under Nickel and Iron Alloy sections. Only alloy mixtures alloys the subject of study as both been and/or in single crystal form. All have Varies with alloy Etching: but mainly as mixed acids of the oxidation/reduction mixture, types etc.). (HF:HNO3, ALLOYS CHROMIUM TITANIUM ETCHANTS CHROMIUM CRll-0001 ETCH NAME: TIME: Acid, removal TYPE: TEMP: COMPOSITION: X...HF x ... HNO3 x ... glycerin DISCUSSION: Cr:Ti, alloy specimen. Solution is a general etch for chromium, titanium and their alloys. REF: Berglund, & Deardon, W H — Metallographer*s Handbook of Etching, Pitman & T London, Sons, 1931 PROPERTIES OF CHROMIUM TRIOXIDE, Cr2O3 PHYSICAL Metal oxide Classification numbers 24 Atomic 16 & Atomic weight 152.03 Melting point (°C) 1990 Boiling point (°C) (g/cm3) Density 5.21 (Mohs — scratch) Hardness 8—9 (Knoop — kgf mm""2) -2000 Crystal structure (hexagonal — normal) (1010) prism Color (solid) Green Cleavage (basal — perfect) (0001) © 1991 by CRC Press LLC

306 293 CHROMIUM Cr2O3 TRIOXIDE, Does not as a natural compound. The most important ore of chromium General: occur mineral is chromite, the FeO.Cr2O3. its a material and used is for glass-like green color as a trioxide Chromium industrially glass coloring pigment. {Note: Iron imparts a light greenish tinge to paint Potassium or glass.) K2Cr2O7, added to sulfuric acid, H2SO4, is the standard "glass cleaner" chromate, crystals solution. Solid used in the fabrication of Not State devices at the present Technical Application: It has possible application as a thin film surface protectant to time. optical properties include for It is used on chrome glass masks as an anti-reflective (AR) coating. anti-reflection. powder form is a lapping and polishing abrasive called "chrome green" and, as In it are to solutions, is mainly preferential. There etch other chromium oxides: CrO an additive CrO2 (brown/black); CrO3 (red); and Cr2O3 (black); green). The latter most often (bright recognized a reaction coating on chromium metal used as an evaporation source in as metallization of devices. used that thin films Note been CrO2 as magneto-optics memory devices. have Single crystals of chromium trioxide have been grown and studied for general mor phology and structure. defect Insoluble in acids, alkalies and alcohols soluble in the "chrome etch" Etching: water, eerie Soluble nitrate or sulfate. containing in fused alkalies. CrO2 formulations ammonium in HNO3. soluble ETCHANTS CHROMIUM TRIOXIDE CRO-0001 ETCH Chrome etch TIME: NAME: Acid, removal TEMP: RT to 30°C TYPE: COMPOSITION: 1 ... 2 A^ H4SO4.Ce(SO4)2.2H2O g ml HNO3 5 ... 25 ml ... H2O DISCUSSION: as amorphous thin films grown on chromium metallized glass masks. Cr2O3 solution The will both the trioxide and the chromium. etch Bulletin 1116B, Rev-HPD/VB/TM/883/lK, MRC Corp 1975 REF: CRO-0002 ETCH NAME: Chrome etch TIME: TYPE: Acid, TEMP: 30°C removal COMPOSITION: 1 2 AT H4NO3.Ce(NO3)3.4H2O g ... ml 10 ...HNO3 100 ml ... H2O DISCUSSION: as amorphous Cr2O3 films grown on chromium metallized glass masks. The solution thin will etch both the trioxide and chromium. REF: Walker, P & Tarn, W H — personal development and application, 1976 CRO-0003: Troost, — personal communication (1976) E chromium amorphous Cr2O3, grown on thin metallized glass masks. Recommends films the use of the nitrate rather than the sulfate as the sulfate compound can leave a residual film on the glass. © 1991 by CRC Press LLC

307 294 CRC of Metal Etchants Handbook CRO-0004 ETCH etch TIME: NAME: Chrome removal TYPE: TEMP: Acid, Warm COMPOSITION: ... AT H4NO3.Ce(NO3)3.4H2O g 2 453.6 H3PO4 125 ml ... H2O ... ml 2500 DISCUSSION: thin films and thin film chromium deposited on Cr2O3 substrates. amorphous glass is general etch for both trioxide and metal. Solution a R — Smith, J Appl Phys, 34,1442(1964) REF: K CRO-0005 NAME: Chrome etch TIME: ETCH TYPE: removal TEMP: Acid, COMPOSITION: 164 ... Ce(NH4)2(NO3)6 g 42ml...HC104 1000ml...H2O DISCUSSION: a cleaning film contamination on evaporated chromium. Solution used as a Cr2O3 as thin etch. removal and B — Solid REF: Technol, 1984, 177 Mednikarov, State CRO-0006a NAME: Sodium hydroxide TIME: 5—7 min ETCH Molten dislocation TEMP: 550°C TYPE: flux, COMPOSITION: ... NaOH, pellets x DISCUSSION: single both cut and cleaved from Cr2O3, crystal boules. Cut wafers were (0001) wafers mechanically polished on a wooden lap with diamond paste. Wafers with (1011) orientation were prismatically cleaved in air at RT, and used as-cleaved. After etching in the [(10T0)] recover alkali, hydroxide with water to away specimens. Then wash specimens fused leach hot HC1 to clean surfaces, then wash in DI water in dry in air. On basal (0001) surfaces, and etch were triangular with edges parallel to pits On (1011) pits were five sided (1120). structures. Dislocations were normal to (0001), random and along grain boundaries. Density measured to 5 x lOVcm2. Potassium hydroxide, KOH, gave less distinct structures. be Appl Brower, S REF: Farabaugh, E N — J W Phys, 36,1489(1965) & CRO-0006b ETCH NAME: Hydrochloric acid TIME: TYPE: Acid, cleaning TEMP: Hot COMPOSITION: x HC1, cone. ... DISCUSSION: used and (1011) Cr2O3, Solution (0001) to clean surfaces after preferential wafers. etching. After cleaning, wash in DI water and air dry. See CRO-0006a for additional discussion. REF: Ibid. © 1991 by CRC Press LLC

308 295 CRO-0007 NAME: Chrome TIME: ETCH etch removal TYPE: TEMP: Acid, COMPOSITION: Chrome x etch ... DISCUSSION: and deposited by E-beam thin (EBE) film evaluated for photo a as P2Cr5 evaporation See CRO-0001 for chrome etch solution voltaic effect. (Note: referenced.) K Crita, M — J Appl Phys, 57,5325(1985) REF: Toda, & CRO-0008 NAME: TIME: Chromium ETCH trioxide growth 1770 K Material, TYPE: TEMP: 4 x 1013 COMPOSITION: PRESSURE: atm ... x Cr2Ox DISCUSSION: chromium a single crystal from pressed as powder pellets. Furnace Cr2O3 (111), grown aluminum tube with a boat pre-coated with Cr2Ox, then processed at temperature was an shown pressure a CO/O2(2%) atmosphere. The O2 partial pressure affected material and in temperature RT grains were n-type; at high At grains converted to p-type. density. large Cr2O3 is hexagonal, not isometric (cubic). (Ill) should be (1010) (Note: prism?) REF: R W A et al — J Electrochem Soc, 132,884(1985) Young, Torkington, R & Vaughn, J G — J Vac Sci Technol, A(3),795(1985) CR-0009: S an films oxidizing chromium metal specimens in by O2 or CO2 thin grown Cr2O3 When the metal is used atmosphere. an evaporation metallization source, it com (Note: as oxidizes evaporation with a green after coating.) monly trioxide GENERAL CLEANING, There are many aspects to the cleaning of General: as related to material surfaces processing part and equipment maintenance. Selection of the particular solvent, acid, or or metallic to dependent upon the metals, is compounds, and other materials alcohol use and may be a combination of solutions and involved, in what are called clean/etch steps sequences . . using liquids, hot vapors, . gases, molecular gases, and molten fluxes. ionic Cleaning may include pressure, such as in steam cleaning, or as steam drying. Water alone considered the universal solvent and, as it is neutral with a pH 7 on the is Scale, it the general washing and final rinse solution used after any acid or Sorenson is to step, followed by an alcohol rinse often remove residual surface water, alkali cleaning with drying in air, nitrogen, argon, or helium. Where heavy dirt and oil contamination then present to parts, they are water washed, are include scrubbing with a soap or detergent on the with chelating and sequestering agents. In without processing of critical parts, solution or as missile and space hardware, both Ivory and such soaps are considered as two of Castille the purity compounds for detergent cleaning highest and Joy liquid soap has been solutions, used in cleaning of semiconductor wafers and electronic hardware for the same reason. Ionic and nonionic or a wetting agent such as Glyptal may be added to such detergent agents, and cleaning agents have been added to acid etch solutions, as well, for a solutions, wetting action. cleaned glassware and quartzware are assist in either soap solutions or Laboratory drying. solutions, by heavy water washing and acid And in the processing of soda- followed lime glass blanks as photo resist masks, one step in the cleaning process includes soap solution scrubbing. soaps and detergents are cleaners or degreasers for removal of dirt, All not grease, and used on all materials, oil, just metals and metallic compounds. or Most small parts as used in the electronics and Solid State industries are free of heavy light contamination, as dirt, and only require such degreasing prior to any chemical treatment. © 1991 by CRC Press LLC

309 296 CRC of Metal Etchants Handbook parts are in clean containers, which may be as plastic bags sealed under Such delivered envelopes, and or may be coated with a removable plastic coating, nitrogen, plastic boxes, sheeting cutting tools; diamond saw blades, or lucite drilling with a sticky- lathe or such as In some cases, there may be back greases and organics from these paper covering. oils, carriers on such surfaces, even though introduced are relatively clean. and wrappings they step in cleaning such parts, and this applies in particular to semiconductor The first their metals and and assembly parts, is to degrease, liquid or vapor, with wafers associated a degreasers developed for this purpose from been large glass beaker Vapor solvents. have TCE to cabinet sized units with boiling liquid, hot vapor, spray heads, with or of boiling ultrasonic vibration, may include overhead chain hoists to handle heavy single without and stainless parts multiple basket. Parts are placed in a in steel basket — lowered into the or a solvent for heavy cleaning, or just into the hot vapor head above the hot boiling for solvent general fine cleaning. The basket is then slowly removed from the vapor head with and drying of hot part. If streaking is observed on surfaces, return parts to the hot automatic the a often until clean. The solvent is in needed closed, recirculating system, and as as vapor hot chamber is separated from the the spill-over chamber by a wall with working, return spill-over of cleaned solvent to the feed chamber section. The hot working continual working is surrounded with water cooling coils near the top, hot rising vapors cool and chamber on steel stainless collect side walls as droplets and return to the chamber bottom — with the parts drag-loss solvent to the atmosphere when the are removed slowly. Both minimum of (TCE) and perchloroethylene (PCE — Perk) are being replaced with either trichloroethylene (TCA) to Freons as the solvents due trichloroethane the carcinogenic nature of chlorinated or residue Freons being more widely used solvents. they are inert and leave no are on as surfaces, as possible Cl+ such from TCE and Perk. ions Acid and alkali solutions may be as wet chemical etching (WCE) or as electrolytic etching (EE) liquid solutions, or vapors; or as dry chemical etching (DCE) for ionic for as RF These may be as surface cleaning only, or include minimum polish gases plasmas. as solutions coming into wide use are bromine (also iodine) BRM removal. (Br2:MeOH) and polish almost all metals and metallic compounds. Such BRM solutions may clean etch, prior to degreasing or after degreasing as either a chem/mech lap and polish to used be steps, damage previous cutting or lapping from or as a free-etch for subsurface remove surface cleaning and polishing. Both acids and alkalies general be used to oxidize a may surface a cleaning step, such as boiling water, nitric acid or hydrogen peroxide, then as with by oxide with HF. Electrolytic oxidation the KOH or H2SO4 and followed stripping oxidizing solutions are used in a similar manner, or used to permanently anodize a other surface. Clean/etch follow the general order: etch damage removal; degrease; solution sequences There clean; etch final acid dip etch clean. alcohol are a number of such sequences rinse; described in the Discussion section of Etchant Formats, and can involve any one or all of the steps mentioned. just processing equipment facility equipment require on-going maintenance clean Much and boilers water in particular — and such items as lines and DI water stills. Hard water ing — the electrolytic reaction between dissimilar metals cause and such as calcium compounds, and sulfates, or aluminum hydroxide gel to deposit out in piping, and in boilers magnesium is as purity water, such as DI water, High an excellent medium for algae growth, scale. such that the water can become contaminated with both flakes of scale from piping as well as skeletons algae. Improper pipe assembly from weld joints can contribute both particulate of and used, oil-type contamination from fluxes matter and the piping, itself, can unwanted used disintegrate, particles. Stainless steel piping introduce in nuclear reactors is slowly internally etch polished to remove proturberances to prevent such particulates occurring. oil If maintained, air compressors can introduce properly into air lines, and all not equipment is prone to collection of dust and oils from the atmosphere; insulation on high © 1991 by CRC Press LLC

310 297 power lines are spray washed, particularly, in arid areas to remove dust and dirt electric and prevent RF generators and their associated lines and insulation, such build-up arcing: clean in require cleaning even in a systems, room environment, also to used as epitaxy Pressurized cans of Freon are used for light cleaning in addition to other prevent arcing. water piping Water or is flushed with hydrogen peroxide or potassium solvent washing. followed and heavy water flushing, solutions, boilers and stills are etch by permanganate acid solutions . . . HC1, citric acid, etc. with cleaned Cleaning section includes general references for parts and equipment cleaning, and This maintenance on water systems. Specific applications plant metals and metallic compounds or be found the individually numbered etchants as part of the Discussion section of will under formats. their to metal processing technology there addition several general methods for cleaning In are materials, or approaches used in cleaning parts and surfaces in the home, in small of businesses, and areas not classified, strictly, as an industrial operation. Several of similar are in actual etchants, but a material or method applied these a particular area of work, not realized specific and so forth. It should be materials, that the modern home uses many on chemicals on a daily basis, such that some discussion of these items is felt worth mentioning. Note that of the items have no reference listed due to the commonality of usage. several those desiring information, consult any chemical text book, see the information For further pamphlets with product, or contact supplied manufacturer as they often have a brochure the brochures available on their specific products. and CLE-0001 NAME: Citric acid TIME: ETCH Acid, TEMP: TYPE: cleaning COMPOSITION: ... (COOH)CH2C(OH)(COOH)CH2COOH x DISCUSSION: equipment. for cleaning of power acids used A comparison of formic and Organic plant acids for citric water systems. cleaning REF: C M et al — Am Loucks, Mech Eng Meet, New York, November—December Soc 1958 CLE-0002: Data Sheet #585 — Chas. Pfizer & Co., Inc. (1958) Analytical methods Citrosolv process for determination of dissolved Fe+ + and Fe+ + + of copper after equipment cleaning. or assay Alfano, S — Electric World, 5 February 1962 CLE-0003: use citric ammoniated The acid for removal of boiler oxides. of Pfizer CLE-0004: #557 — Chas. Sheet & Co., Inc. (1958) Data Chemical cleaning of equipment with citric and ammoniated citric acid solutions. CLE-0005 ~~ NAME: ETCH TIME: TYPE: Sequestrant, cleaning TEMP: COMPOSITION: ... acids/alkalies x 4- ... sequestrants DISCUSSION: The use of sequestering and chelating agents added to solutions used for the cleaning of systems. water REF: Loucks, CM — Power, December 1961 © 1991 by CRC Press LLC

311 298 CRC of Metal Etchants Handbook CLE-0006 ETCH NAME: TIME: cleaning TYPE: TEMP: Acid, COMPOSITION: acid(s) x ... DISCUSSION: heat chemistry and cleaning of A and the exchangers in general of presentation boilers maintenance. plant — Chem Eng, 5 March 1962 Loucks, REF: CM Sheet — Chas. Pfizer & #593 Inc. (1958) Data CLE-0007: Co., alkaline solutions by immersion or electrolytic etch Use of scale, and for of removal stripping. paint Conf, S W E — Int Water Bell, October 1961, Pittsburgh, PA. CLE-0008: & Alfano, magnetite and copper from boiler surfaces by Removal etching. of chemical CLE-0009 Water TIME: Variable ETCH NAME: cleaning RT Acid, to boiling TYPE: TEMP: COMPOSITION: ... H2O x DISCUSSION: Water is the universal solvent, neither an acid nor a base, being neutral with pH H2O. on the Sorenson Scale. It is used to quench and stop etching action by soaking; by a dip 7 by holding part in running water in a beaker, or running water as a cascade system; rinsing; a called, a Commercial on industrial water is so spray. and used for general cleaning; or as (DI) water is deionized by boiling and collecting the resulting steam for high deionized cleaning at Water can be used chilled; purity room temperature (RT); or warm, requirements. immersion to latter is used as boiling water The or steam or oxidize a surface. hot boiling. hydrated oxide may then strip with The as a cleaning step. It also is used as a cleaning, HF removal, polishing solution on soluble or such as the halides. compounds, Water vapor — As a fine mist (fog) for light surface cleaning applied by spraying. Several metallic such as AlAs as hygroscopic, absorbing water moisture in the compounds, and alkaline compounds (KOH, NaOH) deliquesce and liquefy with atmosphere, chemical air. oxidize iron and several iron alloys will to to iron oxides (brown "rust") Pure exposure on atmosphere the brown discoloration observed conditions, "tin" cans, cast normal under cooking utensils. Construction girders are coated with red lead to minimize such oxi iron dation. Steam Hot water vapor under pressure is used as a cleaning vehicle, as well as a — source medium electricity generation or mechanical operation, even as a cutting power for steam metals alloys. Dry cleaning uses steam on pressing, there are steam irons, and for tables restaurants, building walls, vehicle in are spray steam cleaned, medical engines instruments are steam cleaned using an autoclave, these are only a few examples of the use of steam a cleaning agent. as minerals treatment ground waters contain Natural and organic contamination, Water — well as industrial wastes, such that water treatment is a as industry, itself. Water can major be (arid areas); soft (mountain areas); acidic, hard, HC1 in volcanic areas; acidic with with tannic acid in swamps; there are hot sulfur spring and ground waters; and saline water along seacoasts. Industrial commercial water . . . filtered to or solid matter . . . so called"'water remove with the rocks removed" is standard tap water. It still contains dissolved minerals, and is water, aerated for drinking water, potable oxygenize as against saline nonpotable water. to It is the general cooling or wash water in industry, business, and the home. © 1991 by CRC Press LLC

312 299 Such may be additionally treated to remove calcium and magnesium sulfates (hard water with further additives for soft water. Most soaps alone, or detergents, are water), chemical to some with or without specific additives in their formulas. water softeners degree, collected water by boiling, the resulting steam distilled in a separate purity High is distillation). In Solid State processing this is referred to as DI water, may container (still even double-, and include ion exchange beds containing resins to remove be triple-distilled, and is ionic contamination. Although distilled water positive potable, it lacks both negative animal dissolved of natural water essential to content life, and tastes "flat". the mineral DI water is used in car batteries and steam irons, as well as for critical cleaning of This parts. may it electronic be just demineralized, not distilled, sometimes shown as dmH2O, And against DIH2O. as volume water starts with (1) agriculture (greatest cycle of use); (2) The usage greatest may be prior to, or following agricultural industrial, and (3) human and animal which use; consumption. of waste water is of treatment concern throughout the industrialize world. The major major cities have water waste disposal and All plants where both aerobic and treatment anaerobic are used to clarify the water — it is actually sufficiently clean for use as bacteria limited water although, if it drinking not discarded as run-off water, it is usually — for is use agriculture . . . beginning in usage cycle all over again. the REF: Eisenberg, D & K ads man n, W — The Structure and Properties of Water, Oxford University Press, York, 1969 New CLE-OOlOa ETCH TIME: Variable NAME: Kerosene cleaning RT Hydrocarbon, TEMP: TYPE: COMPOSITION: x ... C,o—Ci6 DISCUSSION: gasoline are hydrocarbon derivatives obtained by the fractionation of Kerosene and crude and are used for cleaning of metals, or both fuels. Petroleum ether, C4—C7, also is oil, as solvent with a lower boiling range, e.g., 35—80°C vs. 175—300°C and 40—225°C a for kerosene gasoline, respectively. They are still used as general degreasing solvents at and being temperature but, due to flammability, are warm replaced by other nonflam room to and nonexplosive solvents, such as the Freons. mable (2) clean/etch used for iron is (1) etch with NaCO3; sequence rinse in kerosene/ One benzene, and (3) wash in alcohol. REF: Foster, W & Alyea, H N — An Introduction to General Chemistry, 3rd ed, D Van Nostrand, New 1947, 652 York, — Measor, & Afzulpurkar, K K C Phil Mag, 10,817(1964) CLE-0035: J specimens used in a study of oxidation rates, for clean/etch Fe, shown for iron sequence under CLE-0010. CLE-0023 ETCH Air TIME: NAME: Gas, cleaning TEMP: TYPE: to hot RT COMPOSITION: x ... N2/O2(24%) DISCUSSION: Natural atmospheric air or air in pressurized cylinders, as dry air, is used for both drying as and to remove light contamination, such cleaning dust, and there are the household surface and heavy duty industrial vacuum cleaners for floors, rugs, and furniture. Industrial clean include rooms in-coming air, and may filter electrostatic generators to remove paniculate © 1991 by CRC Press LLC

313 300 CRC of Metal Etchants Handbook content where parts are being fabricated. Such rooms are closely monitored for dust critical count, a cases, to less than 10 ppm. Air-conditioning units can include in paniculate some elements. control as well as electrostatic humidity, Air compressors supply spray water to for cleaning, in addition to their use for mechanical or electrical operations. pressurized air REF: N/A CLE-00024 Qyogenics TIME: NAME: ETCH cleaning TEMP: - TYPE: or below gas, Liquid 100°C COMPOSITION: LN2, and others x ... DISCUSSION: been subzero gases or chemical liquids have other used to soak or spray clean or LN2 of materials. Pressurized cans of Freon are used surfaces spray clean electronic parts, as to both gas or cold liquid, and such cold sprays are used on specimens surfaces during a examination for their chilling action and cleaning function. See the section microscopic both for additional information as "Cold Etchants". on Water REF: N/A CLE-OOlOb ETCH NAME: Benzene TIME: Aromatic, cleaning TEMP: RT to warm TYPE: COMPOSITION: x QH, ... DISCUSSION: Benzene is a coal derivative, as are its homologs, toluene (methyl benzene) and C6H6. (dimethyl CnHn6. with general formula xylene All are used as general cleaning benzene) some alone, in a clean/etch sequence. In solvents, instances, they are the specific solvent or applied to a metallic compound due to the material reactivity with water or other quenching and cleaning Some benzene compounds are used as hardening agents for photo solvents. lacquers in processing, such as for gallium arsenide devices. These resist photolithographic "aromatic are due to their sweet smell. They the relatively heavy are called compounds" alcohol after parts are usually rinsed in and, to remove the residual solvents. liquids use, CLE-0010. See Ibid. REF: CLE-OOlOc NAME: Alcohol TIME: Variable ETCH Alcohol, cleaning RT to hot vapor TYPE: TEMP: COMPOSITION: EOH, ISO, etc. x...MeOH, DISCUSSION: are used alone, as a general cleaning solvent; Alcohols one or more steps in clean/ as etch or as the final rinse sequences; etching and water quenching. Some compounds after that are reactive to water are directly quenched in alcohol or the alcohol used as the etchant. Under normal conditions after acid etching, first water quench, then follow with cleaning rinse, simple or without nitrogen blow drying, or alcohol air drying. Note that solutions with with nitric should not be directly quenched acid methyl alcohol ... the com containing bination of red fuming nitric and methanol was one of the first rocket fuels. of Alcohols from different sources and three derived the more widely used in industry are are methyl, ethyl, and isopropyl. Methyl alcohol (methanol) with the acronym of MeOH, from is alcohol, as it was initially distilled wood wood pulp. Ethyl alcohol (ethanol) with © 1991 by CRC Press LLC

314 acronym EOH, though it can be extracted from other vegetation by reduction is grain alcohol, starch. It nonpoisonous, drinking alcohol; whereas the other alcohols discussed of is the IS0 or IPA is rubbing alcohol. poisonous. acronyms here with Isopropyl are alcohol methanol or ethylene glycol to it poisonous and Industry ethanol contains 5% make is sometimes used. Absolute alcohol is water) pure nonpotable, although 95% (5% ethanol as 200 proof-gallon as drinking alcohol, loo%, used in medicine. classified and alcohols absorb water, such that they are used to remove residual water remaining All will a surface following water on with MeOH being more widely quench/rinse after etching, used. They also evaporate rapidly, a chilling effect. When alcohol is used as a producing this effect has been used to cool a specimen surface during microscope study. Hot spray, vapors can be used degreasing or final cleaning like Freons, TCE, TCA, etc., but alcohols for commonly are more with nitrogen blow-off for drying. Both MeOH and used as liquids for used of etch formulations are either solution viscosity control or cleaning EOH as part Nital (HN0,:EOH) is a widely used cleaning/polishing/preferential etch on irons and action. steels, one example. Many cleaning solutions, as well as shaving lotions and perfumes as contain alcohol. REF: Ibid. CLE-00 15 NAME: Acids TIME: ETCH hot vapor to TEMP: RT TYPE: Acid, cleaning COMPOSITION: . . acid or acid mixtures . . x DISCUSSION: Acids and acid mixtures are used for both etching and cleaning, with specific mixtures depending on the material being processed. acids, such as acetic acid (3-5% in Weak or an both cleaners and medical antiseptics. Strong acids, such vinegar) iodine solution are or even concentrated, are cleaners for the more chemically inert metals, or H,SO, HCI, as used in they on other metals and metallic compounds. are dilute form N/A REF: CLE-00 16 NAME: Halogens TIME: ETCH to RT boiling or gas TEMP: Halogen, cleaning TYPE: COMPOSITION: ... Br,, C12, F2 I,, x DISCUSSION: The halogen of four elements includes fluorine, the most reactive element known, group the only halogen not used on and tissue as a cleaner or disinfectant. Fluorine, as human . . . glass of HF, oxides hydrofluoric acid, is the primary reducing acid for removal metal (SiO,) is etch polished in liquid HF, and frosted in the vapors. Bromine, Br,, is poisonous, can cause goiter, so not used on humans, but is a widely used cleaning and etching it is when with methanol solution mixed Br,:MeOH - the BRM solutions, and bromine - acetone is "tear gas". Pure choline gas is occasionally used as a cleaning and mixed with etching agent, and several of the chlorine compounds are discussed under the Chlorine is tincture section. Iodine, as a mixture iodide, KI, and ethanol potassium of iodine, with and a major medical disinfectant. The I,:KI:H,O solutions in metal processing are the tri- iodide for gold, and other metallic compounds. Similar solutions are general dis- etchants infectants for plastics, glass in the laboratory, or in the medical facility. REF: N/A © 1991 by CRC Press LLC

315 302 CRC of Metal Etchants Handbook 10d CLE-00 Acetone ETCH TIME: NAME: hot TEMP: RT to TYPE: Ketone, cleaning COMPOSITION: . . . . (CH,),CO x DISCUSSION: affinity for water absorption, such that it is Acetone as a final rinse has a high used water quenching to remove residual water from surfaces. It is used, alone, and after etching rinse or as with alcohols. As a solvent, acetone is the primary the only solvent in conjunction used pressurized can as a spray to clean agent for dissolving photo resist lacquers, from a to specimen clean equipment (spinners, etc.) used surfaces prior photo resist application, to after photo resist patterning and thin film metalliza- soaklspray in application, and as a . . . the lift-off technique. tion mixture with it is used as both a chilling solution for other etch mixtures, and As a ice removal argon. water vapor from other gases, such as pressurized a drying agent for as of specimen study it also is for its chilling action, direct spray, been used on used As a and has to reduce heat distortion, or reduce electron impingement damage effects under a microscope a . microscope (TEM) transmission electron using is used a Yellow Room in photolithographic processing, temperature in Where acetone is not This control RH. 72°F and 40% only critical nominally humidity and are controlled, RH, an acetone. in for photo use of lacquers, If humidity is much above 50% resist but the acetone spray will absorb water vapor from the air and deposit droplets on the specimen surface being cleaned . . contaminating surface . . . not cleaning it. See the section . the for Etchants". Water on "Cold REF: Ibid. CLE-0014 Trichloroethylene TIME: Variable ETCH NAME: TEMP: RT to vapor hot TYPE: Solvent, cleaning COMPOSITION: . . x TCE, Perk, TCA . . DISCUSSION: TCE of the chlorinated solvents, all of which are carcinogenic to some degree is one and, still used for general cleaning and degreasing, are being replaced with though they are liquid, vapor degreasers are used with hot or and Freons inert solvents. other Vapor more spray in cleaning all metals, metallic compounds, and general parts. See the Discussion sections of individual materials for the use of these solvents in specific processing. N/A REF: CLE-0017 1-10 min TIME: ETCH NAME: Argon RT TEMP: TYPE: Ionized gas, cleaning Material COMPOSITION: ANODE: Pt, C etc. CATHODE: Pb, x ... AT+ ions cclminute GAS PRESSURE: milliTorr as (mT) POWER: KeV range DISCUSSION: which vacuum, under plasma Ar+ ions, are developed by an RF gas. as Argon ionized the as used target being material RF magnetron (ring magnet on or as DC be may power depositing metal($ to control plasma). These are RF sputter vacuum systems. A basic production type system consists of (1) four target holders above a rotatable specimen holding © 1991 by CRC Press LLC

316 platen; (2) standard vacuum hardware; RF andlor DC controls; (4) a horizontal feeding (3) section. This latter capable of brought up-to-air; whereas the working vacuum inpuVexit being under at least a chamber is held be used Three target locations can Torr for vacuum. metals/alloys, the fourth location for ion cleaning argon multilayer different of deposition levels prior to materials used, but a nominal range is metal deposition. Power vary with from KeV with a 0.5 mT argon over-pressure (back pressure). 100-150 has been the main Irradiation: Although used for cleaning, all of the argon ionized gas gases, some reactive and nuclear particles have all been used in bulk and thin inert gases, The films, thin studies. studied both for adhesion and structure alteration; film material latter, materials thin films for induced damage, compound regrowth, gas entrapment, bulk and or blister formation, and so bubble All such ionic gases and particles can introduce forth. sub-surface damage into a specimen, even ions when being used for surface cleaning, Ar+ levels vs. material being such that power cleaned can be critical. and irradiation studies are shown under the individual metals and gases ionized Other compounds. metallic REF: E et Farnsworth, - J Appl Phys, 29,1150( 1958) H a1 18 CLE-00 ETCH NAME: Hydrogenloxygen TIME: OO°C, 1 600- TEMP: TYPE: Gas, cleaning nominal COMPOSITION ... H,, O,, etc. x DISCUSSION: + , removal is the reducing atmosphere for against H state, as its molecular in H, ionized hydrogen oxides of referred to as from metal firing. It also is used for surface surfaces, cleaning of high temperature metals and alloys, or ceramics and dielectrics, such as alumina and beryllia prior to metallization as microelectronic circuits. Both hydrogen and substrates gas (FG) (85% forming as a nonflammable mixture, are used in Solid State H,), N,:15% of solder assemblies to prevent oxidation of parts and subsequent and metal processing in of alloys. is usually done metals and an inert atmosphere, failure. Heat treatment adhesion embrit- nitrogen or argon, but it such be done with hydrogen for specific hydrogen as can tlement the surface. Note that platinum and palladium as powders - platinum black or of used - absorb large volumes of hydrogen, and are will for such purpose palladium black as hydrogen storage systems. hot under 0,; OJAr, 021N2, or OJCO, are used to grow metal oxides Pure Oxygen: in growing and water vapor as include gas furnace conditions, may thin films on silicon. SiO, oxides are "hard" oxides, as compared to the Such hydrated forms grown from boiling hard oxides are H,02, and from electrolytic KOH solutions. Where the HNO,, or water, used as etch masks and for surface passivation, the hydrated oxides are often used as a BHF. . . . deposited, then stripped with HF or surface cleaning step As an mixture is one of the most widely used methods of oxy-hydrogen torch, the gas metals or working glass, other than acetylene or propane torch. As a hot flame, brazing such torches can be for brazing, annealing, or surface cleaning in the assembly of used parts, although the cleaning function is of only minor concern. REF: N/A © 1991 by CRC Press LLC

317 CRC of Metal Etchants Handbook 304 19 CLE-00 TIME: Variable chemical etching ETCH NAME: Dry TEMP: RT etchlclean TYPE: RF plasma, Material ANODE: COMPOSITION: CATHODE: Variable by x ... CF, material x (5%) 0, ... in cclmin GAS PRESSURE: milliTorr (mT) range POWER: KeV DISCUSSION: mixture shown application gas mixture for many metals and metallic is a generally The etching surfaces. There are cleaning of in both the a number of other singular compounds and mixtures designed for specific materials, and all gases are used in their ionic species gases or (CLE-0018), the an RF plasma. Where gas is reactive, such as molecular as form against BCI,, the Ion Etching, RIE, and there are several other specialized is called Reactive system as acronyms. own systems with their is one of the major divisions of etching as used in this Dry chemical etching (DCE) a is more often applied for selective structuring of Solid State devices than text, and as cleaning method. Bollinger, D REF: et Solid State - March 1984, 117 a1 Technol, CLE-0020 ETCH Indium TIME: Variable NAME: TYPE: Metal, cleaning TEMP: Molten COMPOSITION: ... In x DISCUSSION: In, as a molten metal is used as a surface cleaner and light material remover in liquid InP, wafers during the phase epitaxy (LPE). It is used with indium phosphide, specifically InP. In LPE systems the wafer substrates are attached to a of film additional growth thin across the surface of the to effect is wiped horizontally graphite plate that molten metal film growth. In order to reduce defects being introduced into the growing film epitaxy thin what from the substrate, the initial operation uses is called the melt-back technique, where the substrate surface is cleaned with the molten metal before controlled growth is initiated. melt-back may be done on the Further thin film during growth, also to improve growing the of the film. Similar LPE melt-back is done with other materials, such as gallium quality used growing gallium arsenide melt-back is thin films on gallium arsenide substrates. in High Molten Flux: and chemically inert metals, such as titanium, melting temperature molybdenum, tantalum, and tungsten are surface cleaned or etched in molten metals. The flux can be or mixture of chemical compounds, applied to any material, often as a a metal of are used in the growth single preferential etch in addition to cleaning. Such fluxes also such and garnets crystals, as See CLE-0029 ferrites. Hone: CLE-0022 - Abrasion. - REF: NIA CLE-002 1 TIME: NAME: ETCH TYPE: Methods, cleaning TEMP: COMPOSITION: x . . . solvents/acids/alkalies . DISCUSSION: liquidslvapors; (2) acids - HCI; solvent Methods of surface cleaning described for (1) mixtures; H,O,; HAc, alone or as HNO,; (3) alkalies -both hydroxides and/or carbonates; © 1991 by CRC Press LLC

318 (4) heat treatment vacuum, wet or dry atmospheres of N,, Hz, 0, or air; (5) aqueous - - H,O, H,O,:NH,OH, and (6) ultrasonic - detergents, solvents, acids, or and oxidation and of abrasives included. the alkalies. Also electrolytic solutions, use REF: Tech Tel 3143(1958) Bell Pub, CLE-0022 ETCH NAME: Abrasion TIME: TEMP: RT TYPE: Abrasive, cleaning COMPOSITION: x . . . . etc. gritlpaper abrasive DISCUSSION: lapping a surface for general cleaning. Sand for scouring; sandpapers, such Abrasive of or emery; smooth paper or rough filter paper only; colloidal liquid suspensions of Sic as or AI,O,. Applicable to use on several materials, other than those usually thought of SiO, such even some plastics. metals, glass, woods, and as abrasives, as of steel, copper, plastic with or without detergents are used to remove heavy Pads and as pots as in general cleaners of parts, and contamination on industrial equipment and well copper are a household. brushes of steel, brass, plastic, or in used in a similar pans Hand Grinding wheels and arbor brushes; bead-blast cleaning with sand under manner. pressure; steel, glass plastic beads rotating to clean surfaces as in removing old paint from small and parts. Abrasives most often used in slurry form. In Solid State material processing a mixture are W-5 garnet (15 of grit) in water pm glycerin is widely used for lapping wafers with and final water washing. Finely powdered white alumina (Linde A and Linde B) and diamond grits of than less pm 1 final surface polishing and cleaning. size are used for REF: N/A CLE-0025 ETCH TEMP: NAME: Borax TEMP: RT hot Borate, cleaning TYPE: to COMPOSITION: x . Na,B,O,. 10H,O . . . x ... H,O DISCUSSION: 3000 years with several uses: been in use for over as the natural mineral, Borax, has for washing cleaning of cloths and dishes; as an antiseptic and preservative; and a solvent as for metallic in soldering and oxides in alloying metals. In washing brazing; as a general flux it is a water softener for hard water. The Arabs and Egyptians were using both borax and niter (sodium carbonate) solutions mummification, and as a flux for gold soldering, as in back was B.C. during the Egyptian Dynastic Period. "20 Mule Team Borax" far as 4500 from Death Valley California mined area beginning in the late 1800s. the In processing, to include Solid State materials, borax has been used for surface metal cleaning, and as a constituent in some cleaning and etching solutions with other acid com- ponents. Dana, E REF: & Ford, W E -A Textbook of Mineralogy, John Wiley & Sons, New York, 1950, 743 CLE-0027 TIME: ETCH NAME: Broom RT TEMP: TYPE: Broom, cleaning COMPOSITION: x straw, wood, plastic, etc. ... © 1991 by CRC Press LLC

319 CRC Metal Etchants Handbook of 306 DISCUSSION: and mops in use since most ancient times for general removal of have Brooms been The twigs, rushes, or leather floors, tables, walls, etc. first brooms were wood litter on handle with plaited grass or leather as a tying rope. strips tied together on a wooden Large in in the Pacific area, as are tree leaves in use and southern palm leaves are still Africa Asia. of straw The feathers also is of ancient origin, both still in use today as the use and household long-handle brooms for floors and tables or a feather duster. standard short- or have today history of use and brooms plastic brooms of many sizes and a long Horse hair in both industry and household use, to include large push brooms. The standard shapes are may be of cloth, with or without oil for additional dust collection or for polishing latter such action, or vehicle driven street sweepers as heavy-duty floor polishers to include waxing, rotating brushes. their circular, with thick but assembly The fairly is an ('I," diameter) similar to a broom, standard mop is of with be used as a dry a wet mop. The latter is used oil, or can cloth strings or strips that to hold water and a roller squeezer, bucket the bucket may be on wheels. There mop and squeegee type mops with foam plastic inserts for throw-away and replacement when the are becomes too plastic stiff and loses absorbency. and dusting, mopping, scrubbing, brushing. The soft camel's hair Common terms are in painting and cosmetics, and there is a special static brushes have special application on engineering vellum, or in static sensitive areas. The brush body brush used removal replaceable strip of radioactive polonium, Po, behind the camel's hair brush contains a or wide) with a handle. Continual rubbing across a paper 2" plasticlwood (about section . . . it can a metal surface can build up a static charge of electricity surface or cloth, even make paper lift curl when the hand approaches and . and . . an electric spark discharge can dry weather, a common households during cold or in when an occur. This is occurrence then - building up a static charge reaches for a door - across a rug individual walks a static discharge. The static brush, . zap . . . . when wiped across a surface, will . handle the static charge. There are other, larger static eliminators available that blow cold remove hot the or polonium strip to remove the charges and there are smaller "spike air across electrically activated to eliminate static. houses have static arresters Most charge" units grounding. Static electricity e.g., and in the soil, wire metal (against lightning), rods buried to collect dust in some homes is used businesses as part of the air-conditioning and many O,, for elimination of smoke, or heating duct systems. See CLE-0033 for use of ozone, CLE-0028 for use of a brush. The legendary Broom is most often depicted with wooden twigs as the broom Witch's and is a plant called Witch's Broom, the tassels sometimes used as a dusting section, there The tail of a fox is called a brush, and has been used as such, as have been other broom. animal furs. NIA CLE-0028 ETCH Brush TIME: NAME: Brush, cleaning TEMP: TYPE: RT COMPOSITION: x ... bristles (pig), plastic, etc. DISCUSSION: Brush is another name for broom (CLE-0027) but is discussed here separately due to some specific applications than just general cleaning more as associated with brooms and mops. As a hand brush, notably for personal grooming, pig's bristles have been in use since ancient times, today, plastic fibers other fiber-like materials are more prevalent. and Most well known as a brush and comb set for personal use, the comb is made of - © 1991 by CRC Press LLC

320 originally - or tortoise shell - now, also of plastic, metal, etc. With metal bristles, wood type one known as a Curry Comb used for grooming horses; another, with a of brush is scrubbing parts -removal on metal a heavy duty wooden handle and steel bristles, as brush film metal plating, thin scale (oxidation and other contamination products), old paint, of metal build-up on extraneous evaporation. Smaller steel or brass thin film parts due to metal for general scouring of pots and pans in cooking, or to "brush bristle brushes are used of a softer surface for decorative purposes. Plastic pattern" metal, plastic, leather, wood a wood or plastic housing are similarly used for scrubbing. Scouring pads brushes fiber in metal or plastic mesh - with or without soap detergent in the pad, are general - fine scrubbing brushes. a dusting brush used as an item of apparel, or A fox's as tail is called a brush, used like duster. Other forms of special brushes are part of manicure sets, such as the a feather brush finger-like chamois skin small eye brushes for make-up used for polishing nails, and is a hand-sized straw for general surface cleaning, whisk broom shadowing. The "broom" of for removing used clothing by "whisking". There is a special dusting notably lint from - a wooden handlelholder about 'I," wide - the brush portion about 2" in depth - brush about ft . . . originally designed for use on a drafting table to remove dust total length 1 detritus from erasers, pencils, etc. used and drawing, also now used as a general table in rubber/ duster. There are long metal bristled brushes with the bristles set in a slightly mobile plastic base, used for grooming and carding the fur of cats and dogs, or as a carding comb CLE- used horse curry comb already mentioned under for separating flax fibers. Also the 0027. REF: N/A CLE-0029 NAME: Hone ETCH TIME: TEMP: RT cleaning Stone, TYPE: COMPOSITION: ... rock, metal, etc. x DISCUSSION: used used and sharpening, and may be for cleaning dry, water wetted, or are Hones with oil. Arkansas stone is a hard, fine grained and dense aluminum oxide rock impregnated used for sharpening metal knives long . . "honing". Natural emery is a mixture of by . and respectively, - A1,0, and Fe,O,, ore aluminum oxide and magnetite, magnetic iron to Arkansas stone in use. Turkish emery is considered of highest quality, similar and both Sic, types of stones are also referred to as whetstones. And today, artificial silicon carbide, known commercially as carborundum, also is used as a hone. All of these rock type materials = 919 + , second only to diamond and capable of cleaning, have a Mohs H of hardness rating polishing all other materials. There also are artificially hardened or fabricated or cutting, metals, metal alloys, carbides, and borides. The carbides may as shaped parts for use be materials. a drill or hand drill, and used for cutting, shaping, or cleaning of other press with some countries the itinerant knife grinder still comes around with his foot-powered In a leather strop and stone grinding wheel; straight razors are sharpened with a combination of hone; and meat carving knife set includes a serrated a tong for sharpening. Hand and metal electric hones use a series of hard steel discs across which the knife edge is drawn for sharpening. or term "stoning" is sometimes applied to the use of rocks as a cleaning The surface conditioning agent, such as wood being stoned to develop a grain finish structure. REF: NIA © 1991 by CRC Press LLC

321 308 CRC of Metal Etchants Handbook CLE-001 0e ETCH NAME: Ether TIME: warm TEMP: TYPE: Ether, cleaning RT to COMPOSITION: . . . . C,H50C2H, x DISCUSSION: (ethyl by treating ethyl alcohol with sulfuric acid to produce a ether) is Ether made with a pleasing odor. It has long been used as a general anesthetic, liquid volatile colorless, largely replaced by other less inflammable but has explosive chemical compounds been and will and bum in air. It is an excellent solvent for fats, gums, and resins, and as ether ignite NH,, be some household cleaning solvents, though ammonia, in is more may a constituent used (Windex). widely is Ether in many chemical processes, and is a fuel additive in high performance used racing cars. It is occasionally in Solid State chemical processing as a cleaning and dry used or nitrogen solvent similar to alcohols gas. Ibid. REF: 1 CLE-0003 ETCH NAME: Rubber TIME: TYPE: RT Organic, cleaner TEMP: COMPOSITION: . . . . rubbers x DISCUSSION: from the South American rubber tree was imported to Rubber in the early 1800s England as rubber as it was found to erase pencil marks from paper by rubbing. It is still Indian so long yellowish rubber widely 1" squares, 2" a soft bars of "gum rubber" as used, to include used in engineering drafting. Other than as a paper pencil mark remover, there are many rubber products, today, from vulcanized to plastic rubber products. In industry vehicle tires artificial rubbers are Buta-A used in vacuum equipment, and two and Viton as gasket seals as Buna-N, isoprene, neoprene, etc. are others there such dextrin, C,H,,05, as a by-product in the reduction of starch for its sugar gum is British mixed with water is called mucilage (glue). Animal glues are from hooves when content, . . . none of which from flour and water horns; acrylics from plastics; and white paste glue . . but can be dissolved with . of the alcohols and other fluid cleaners some are cleaners described here. Methyl ethyl ketone, MEK, is one such solvent. NIA REF: CLE-0032 NAME: Sand ETCH TIME: TYPE: Rock, cleaner TEMP: RT COMPOSITION: grains . . . . SiO,, x DISCUSSION: as water-washed, roughly rounded of silicon dioxide, Sand grains When mixed SiO,. as slurry, sand has been used since ancient times to scour and clean cooking utensils. a water called sandblasting dry or air or nitrogen as the carrier gases, it is pressure, Under using bead blasting, as it may be artificially fabricated "beads" of glass. In either case, pressurized sand particles are used in many areas and industries to clean material surfaces from removing grime from rock building paint removal from parts; to general cleaning or roughening faces to with surface; to develop grain structure a metal woods or both cleaning and polishing in action. S.S. White Dental units were initially developed with a rubber tube and small exit nozzle using finely powdered sand under pressure to clean teeth. They have been adapted © 1991 by CRC Press LLC

322 for general industrial use a method of cleaning, cutting, or shaping of parts. One example as such use is the fabrication of screws, as these mobile nozzles are one of the few of in cutting a re-entrant angle, to form a circular hollow within a solid methods capable of or in used the fabrication of jewelry and They also are the pattern frosting of etc. material, in using hydrofluoric acid, HF, which is particularly dangerous. These S.S. glass, rather than the in of the semiconductor field for both dicing White units were initially used early days more recently, for angle shaping exposed and, p-n wafers and as general surface cleaners junctions around the wafer edge. other natural rocks that, when powdered, are There are as cleaning, removal, many used polishing abrasives. Selection depends on the Mohs hardness, abrasive size, and particle or shape, sand has - e.g., quartz forms sharp slivers with faster cutting action a rounded shape as colloidal silica, a fine polish. All - the submicron-sized spherical particles produce of a Mohs hardness silicas have H = 7, but it is the particle shape that controls the cutting, cleaning action. polishing, or Corundum, (H = 9) has sharp, flat grains; garnets (H = 5) have blunt grains AI,O, down in size during use, giving finer and finer cleaning and polishing action; that break limestone, CaCO,, = 4-5) has soft grains; diamond, (H = lo), the hardest material, (H angular grains most gives fine polishing action, and is has commonly used in an oil and and carbides or cubic boron nitride, paste. Artificial borides B,N, and silicon carbide, Sic, with a hardness of H = 9 +, can have a blocky grain structure with rapid cutting action. Lava soap contains a high percentage from of silica grains that were originally obtained rock extrusion from volcanic magmas. Pumice is pumice, a froth-like, physically light used as well a whetstone for cleaning other materials, as as a lightweight building stone. REF: NIA Of CLE-00 1 NAME: Ozone ETCH TIME: to warm RT TEMP: Gas, TYPE: cleaning COMPOSITION: x ... 0, DISCUSSION: as ozone, occurs naturally in the atmosphere in small quantity. Fluctuation of the 0,, in ozone-oxygen level concern, as ozone acts as the high altitudes over the Antarctic are of sun. be stable for years at very cold a screen against ultraviolet light rays from the It can at room temperature, but decomposes rapidly above temperatures, months almost 100°C; and explosively at instantaneously Ozone can be formed from normal 0, by passing 300°C. e.g., the pungent odor associated with lightning storms. air through an electric discharge, The rapid of flames from a burning wood fire produces some ozone, and it is quenching of 1 ppm in air can be injurious to health. part some chemical processes; an extremely powerful oxidizer, and Ozone is electrically powered ozone generators are used as air fresheners. There are small cigarette in buildings such as theaters, restaurants, etc. ash units available that will dissipate the smoke from a burning cigarette. Larger units, tray with air being blown through an electric discharge, are used clean metal surfaces in to part industry: the in the ozonized air for a few seconds to clean. is held REF: Ibid. CLE-0034 TIME: Soap NAME: ETCH to RT TEMP: hot TYPE: Organic, cleaning COMPOSITION: ... 3C,,H,,COO x © 1991 by CRC Press LLC

323 310 CRC of Metal Etchants Handbook DISCUSSION: Soap by treating fats and oils with sodium or potassium hydroxide. Sodium is made while soaps are are soft. Other oils may be added, such as lanolin potassium hard, soaps soap. Other oils are used, (Palmolive soap) as palm oil Dove (from sheep) in such or - of - sandlewood, lemon, Attar Roses, are all natural herbals with scented chemicals and the highest purity soaps are Ivory and Castille soap, both recommended used. Two of for cleaning critical parts, such as missiles and space hardware. Lava soap contains a the of powder (volcanic silica froth rock), specifically designed for of pumice high percentage heavy grease, oil, and grime; anyone who has removal in the U.S. military is familiar of been semisoft, yellow blocks of lye soap, with a high sodium hydroxide content for with the chemical cutting action. Both KOH and improved may NaOH as "lye", and be referred to hydroxide as "caustic soda". water solution, alone, they have a soapy feeling sodium In high concentration, can cause and bums on the in blisters and, not are skin, though they dangerous as acids. The hydroxides are chemical bases, and when mixed as Normal as quite neutralize a Normal acid solution. solutions will liquid soaps that grade many skin creams with added palm, lanolin, or There are into Both liquid and dry powdered coconut oils. used for dishes and clothes washing are soaps called soaps, and contain chelating or sequestering agents that improve wetting detergent control sudsing or de-foaming. Pure oils alone have long been action, action for foaming to clense skin. The ancient Greeks rubbed themselves with olive oil, then scraped it used Chapstick off Today there are many oils and creams as sunscreen lotions, and a stigil. with is a thickened petroleum jelly similar to'vasoline. The latter may be mentholated. Egyptian records dating back to 4000 B.C. list of formulas as their priesthood were the hundreds and medical in the Mediterranean area. original chemists practitioners REF: Ibid. CLE-0036 TIME: NAME: ETCH Vacuum TEMP: RT TYPE: Vacuum, cleaning COMPOSITION: x . . . vacuum . DISCUSSION: the removal Vacuum is created air and other gases from a container. by of mechanical A - roughing pump) with internal moving vanes and is constructed vacuum pump (oil pump that physically pull air from a closed glass or metal chamber chambers an attached through hose create a vacuum in the chamber. They are nominally rated for a to vacuum Ton level km), and are used as the initial pump in industrial vacuum systems. These mechanical (1 are called pumps pumps, and there are similar cryo-pumps, chilled with roughing that LN,, LHe without oil. operate the D & used in and metal processing range from small R as Vacuum systems Solid State to large systems, but all operate in a similar manner. Once the initial type units production is completed with a roughing pump, system is switched over to a high vacuum pumpdown the pump hot oil; cryo-pump with helium and charcoal getter; turbo-pump; ion pump - with - cryo-pumps the most prominent as oil-free systems. There are large, walk-in currently testing chambers, vacuum those used in such satellites; and belt systems, where a con- as tinuous roll of material, such as mylar, can be fed through and metallized. Vacuum work but is most often the to Torr, on modem systems are capable of levels done to 10-lo and lo-" Tom. Note that space vacuum is considered to be on the order of 10-l8 Torr. There are sputter systems; ion milling systems; and RF dry chemical etching RFIDC systems, using ionized gases. The two latter systems are used for structuring material surfaces and multilayer thin films. © 1991 by CRC Press LLC

324 Any vacuum can be used with vacuum, alone, as a drying and cleaning agent, system in can include heat inorganic material processing. And organic material, such as or in now foodstuffs, the operation combining a drying action with vacuum vacuum are packed, a plastic bag. This product sealing the may in quick-freezing be but vacuum freezing, as is a different process as moisture is retained. vegetables the household vacuum cleaner, Other there are units capable vacuum systems include and vacuum air blowing by including or Large industrial systems either of a reversing switch. for cleaning floors, vacuum removal of water and, may oil spills in the ocean be where vacuum removal oil. Vehicle mounted systems are used in street cleaning with occur, for of vacuum air blowing, and rotating brushes. of a combination and REF: N/A CLE-0037 Oil ETCH NAME: TIME: warm TEMP: RT to cleaning TYPE: Oil, COMPOSITION: x ... oil DISCUSSION: as a cleaning solution. Mineral oil from petroleum or coal; animal oil, such as Oil used from lanolin or vegetable oils, such as olive, peanut, linseed, safflower, or cottonseed sheep; Olive oil been used in the Middle East and Mediterranean are as a body cleansing oil. has at least 3000 B.C. oil since - the body, then scrape excess away with a wooden into rub oil as stigil. also is worked into leather to make it pliant, bone well as for cleaning action: or Oil soap is a soft, high oil content soap used alone for cleaning, or following by saddle waxing. Linseed is rubbed into wood to bring out grain structure, as well as for cleaning and oil Cottonseed oil in large quantities for the making of soaps. Oil mops are polishing. is used of cloth pads saturated with oil, used for cleaning made polishing floors, and oiled hand and clothes on etc. The oil aids in furniture, table tops, and dirt removal, and leaves a thin dust protective surface coating to prevent drying out. Light oils, such as 3-in-1 oil, are used to both remove and dirt from parts as well as a lubricant; there are various grades and dust of car engine oils, some chemical detergents added to improve cleaning thickness with plastic compounds from a thin oil, to grease consistency, to are that grade action. There of which have been used as cleaners in addition to their properties such as solids, all lubricants. can homogenized or thickened to cream consistency, such be cold cream used Oils as facial cleanser as a . lanolin and coconut . . as the base ingredient in such oil widely used . . . suntan lotions are similar from a light oil to cream consistency with facial creams sunscreen additives. There product containing small spheres of artificial additional is a new in a suntan lotion cream, the sponges helping to retain sponge oils and perspiration. body Natural long been used, soaked in water sponges have oil for cleaning or . . . called "spong- ing", and, today there are plastic sponges used in a similar manner. Thickened oils also become grease-paints in various colors for facial decora- greases: tion . used in religious ceremonies since earliest times, the American Indian "war paint", . . grease is a heavy . . . removal is often with cold cream. Cosmoline circus clown today the to coat weapons and other metal parts for long-term storage to prevent rusting, and used a light soft platens are coated with lapping oil or glycerin also as a rust preventative. iron Spermiceti - whale oil - is actually a wax-like substance obtained from the head of the sperm primary use, again, since ancient times, has been for illumination whale. Its . an . . lamp. The spermiceti flame was used to establish oil International Candle-Power unit the as a light intensity measurement. oil nut oils are used in cosmetics. Coconut oil has been mentioned, bur aimond Some - orange, used; peanut oil most often used is cooking. Oil from citrus fruits in widely © 1991 by CRC Press LLC

325 CRC of Metal Etchants Handbook 312 tangerine - food flavoring, in air fresheners, facial creams, soaps . . . the lemon, lime, for "zests" colored rinds additives. Many flowers produce oils, such as violets as called food latter The roses. and Roses, both used as in soaps, etc. Aromatic Attar of as air fresheners, Oil of Cedar was in use in wood days in Asia Minor from the Cedars of oils: biblical and pre-dates even the use of cedar, circa Lebanon, Sandlewood Both used B.C. as 3000 air fresheners incense . . . . . . both fine odor and as a preservative sandlewood as cedar for . the . cedar chest. . clothing insect pests against for storage of are another category derived from oils. Paraffin beeswax from Waxes is from petroleum; the honeybee honeycomb; wax the conifer tree of the same name; carnauba castor oil from the castor oil from the beechnut tree; bean; beechnut from from the bush myrtl; oil myrtl oil from cow hooves. All of these natural oils can be used neat's foot formulations. in wax And many artificially derived chemicals as oils or waxes, such as banana oil. Such there are are waxes, such as oils mixed with for polishing and cleaning, as wax beeswax:paraffin oil alone. more water repellant surface finish than long-lasting, often produces a REF: N/A - CLE-0038 ETCH NAME: TIME: RT to boiling TEMP: TYPE: Alkali, cleaning COMPOSITION: . . . 2- 10% KOH/NaOH . x DISCUSSION: of general metal cleaners and, Hydroxide solutions electro- in low concentration are may as a pickling bath or for surface conditioning. Other base chemicals plating, be used (>pH Sorenson Scale) may be used with the hydroxides or by themselves, such as 7, carbonates and wash parts thoroughly until the soapy feeling borates. After alkali cleaning, is removed. when used hot to boiling, of surfaces Higher solution concentrations, particularly can preferential etchants on metals, and will produce be severe skin bums. Some cleaners, such as Drano, contain hydroxide and should not household be handled with bare hands. REF: N/A - CLE-0039 ETCH NAME: TIME: TYPE: Electrolytic, cleaning TEMP: ANODE: COMPOSITION: x KOH ... CATHODE: x% or x . acids POWER: .. . DISCUSSION: are used as Hydroxides with deplating by surface oxidizing solutions anodelcathode as a the is stripped with reversal, or oxide method of surface cleaning. Acids such as HF HCl and H,SO, also may be used as electrolytic surface cleaners, or used as wet chemical etching without electric current. HNO, and cleaners (WCE) will be oxidizing like the H202 alkalies. REF: N/A CLE-0040 TIME: NAME: Ammonia ETCH TYPE: Base, cleaning TEMP: RT COMPOSITION: x . . NH,/NH,OH . . © 1991 by CRC Press LLC

326 DISCUSSION: Both and ammonium hydroxide are general surface cleaners, and also used to ammonia drained into acid sump, which is then neutralized neutralize acids. Chemical acid sinks are an alcohols are disposed with ammonia before effluent release into a city sewer system. Note that be mixtures can explosive, or alcohoUacid toxic acid separately, as drain, not of down an will kill bacterial action used in water waste disposal operations. and alcohols medicinal "smelling salts". Crystalline ammonia tarnish observed on silver, is the The the in to due of sulfur compounds in part air, is easily removed with often the presence or saturated cloth. There are similar compounds ammoniated compounds supplied as a paste brass, bronze, copper, for such as "Brasso". and N/A REF: CLE-004 1 Zeolite TIME: ETCH NAME: TYPE: Mineral, cleaning TEMP: RT COMPOSITION: x . . (Ca,Na2)O.A1,0,.9Si0,:6H,O . . DISCUSSION: 30 zeolite minerals as natural hydrated silicates, the formula shown is There are some the mineral mordenite which for as a calcium, sodium, or aluminum silicate. They is typical are in granular form as drying compounds. Commercial Dri-Rite is dyed light blue in used from the air, it turns light pink. Oven baked above 125°C color and, as it absorbs moisture to collected water, granules return to the blue color, and material can be re-used. remove Place a small amount in the bottom of a glass desiccator jar, cover and seal with a vacuum grease, and remain dry without oxidizing. Hygroscopic compounds, such as material will are held desiccators. In food processing, desiccator drying, to include heat and a AIAs, in off and is one preparation method, to draw zeolites are used in shipping liquids light vacuum cartons as a drying compound against possible breaking or spills. or packages NIA REF: CLE-0042 TIME: Variable ETCH NAME: Hydrofluoric acid RT to hot TEMP: Acid, cleaning TYPE: COMPOSITION: ... HF x DISCUSSION: is the primary reducing and oxide removal acid used Hf State material processing. in Solid or other mixed with etchant, water or alcohol diluted, alone, a concentrated as It is used fluorine compounds, as buffered hydrofluoric acid (BHF) solutions. It will remove the "native oxide" that automatically forms surfaces as a passivating layer when on metal immerse - has long been used in the etch patterning exposed glass to atmosphere, and of - vapors for frosting. It is considered a cleaning solution for stripping of thin to polish solution mixture, oxidation/reduction acid in film oxides only, otherwise it is the reducing with be as HNO,, should H,O, used in handling any fluorine containing the oxidizers. Caution acid or compound due to health hazard. REF: N/A CLE-0043 ETCH NAME: Heat TIME: TYPE: Thermal, cleaning TEMP: >22.2"C COMPOSITION: . . . . heat x © 1991 by CRC Press LLC

327 CRC of Metal Etchants Handbook 314 DISCUSSION: Thermal of metals and metallic compounds used as a cleaning or drying heat treatment vacuum conditions, or inert gas atmospheres under furnace con- under agent, alone, with heat also is used in fabricating metal alloys (irons, steels, coppers, aluminums, ditions. Pure structure, such characteristics specific etc.) for and material strength, ductility, hardness, as factor, With and the main so may act as a preferential structure and forth. temperature as defect With reactive atmospheres, in etchant. passivate or addition to cleaning action, to condition by nitridization, oxidation, surfaces halogenation, etc. with sulfurization, Drying as use of light or IR the such white for drying automotive paints or heat includes lamps, parts after water washing or acid treatment. general Clothing is dried cleaned by hanging in sunlight; salt is collected by evaporation of and by foodstuffs in the sun or are dried either hanging in a cool, dry storage area. sea water; These are all methods of cleaning and drying with the use of some form of heat. REF: NIA OF COBALT, Co PHYSICAL PROPERTIES Transition metal Classification Atomic number weight Atomic Melting point ("C) Boiling point ("C) Density (g/cm3) Thermal conductance (cal/sec)(cm2)("C1cm) heat (cal/g) Specific 25°C fusion heat of Latent (callg) (callg) Heat of vaporization Atomic volume (WID) energy 1st ionization (k-cal/g-mole) (eV) 1st ionization potential Electronegativity (Pauling's) Covalent (angstroms) radius Ionic (angstroms) radius thermal expansion of Coefficient linear 10 - cmlcml°C) x ( 6.24 Electrical resistivity (ohms-cm) 1121 Curie temperature ("C) 0.32 Poisson ratio 30.6 Young's modulus (psi X lo6) 37.0 strength annealed X - (psi 10') Tensile 0.50 (cm2kg Compressibility x 4.18 function (eV) Electron work 37 (barns) section Cross Hardness (Mohs 8+ scratch) - 125 (Brine11 - kgflmm) (10i0) normal) - Crystal structure (hexagonal prism, hcp Color (solid) Grey-reddish Cobalt blue (gaslpigment) Cleavage (prismatic) ( ioio) © 1991 by CRC Press LLC

328 COBALT, Co not occur as a element. There are some 20 cobalt minerals, the General: Does native and smaltite, CoAs,.NiAs,, CoAsS and arsenides. Cobaltite, sulfides most important being cobalt minerals occur large quantity. They are associated with nickel, though no are in ores, metasomatic contact deposits. Both metallic nickel iron and copper deposits commonly as is black Fe304, magnetic iron magnetite, show slight, natural magnetism, but can and cobalt natural mineral. Irons as steels can be artificially magnetized, but are primary magnetic and magnetic under processing conditions. not normal steels, use of is as an alloy with iron in the industrial of cobalt Primary production steel, an alloy of SST. Stellite, and tungsten is used including stainless cobalt, chromium, lathe tools and, as it will hold a sharp edge at red heat, is for for medical knives, used scalpels, etc. It in many of the iron magnets. Cobalt produces a deep blue is a constituent "cobalt blue", used a pigment in paints and glass. The salts of cobalt are highly color, as or turn from will pink pink to blue with colored, particularly blue. Solution saturated paper changing approach wet weather and, as a writing fluid, is "invisible ink'' -pale pink, the of blue when heated. to it has a radioactive half-life of about 5.75 years, and is *Co, As the isotope cobalt-60, cobalt, in testing. CAUTION: Some alloys containing and when sub- used nuclear studies To. radiation, can become radioactive with conversion of the cobalt jected to fraction to Cobalt, and chromium can all nickel, easily electroplated as hard thin film surface be coatings, though nickel and chromium are more widely used due to quantity availability. Technical Application: is used as an n-type dopant in some compound semi- The metal as a blocking and CoSi,, for use Co,Si CoSi, and is under evaluation as a silicide: conductors, is used in radiation testing *Co, in heterostructures. As already mentioned, cobalt-60, layer radiation - for alpha particle Pb, pellets usually converting lead, by State devices, of Solid with a 24-h half-life. - been grown as a single crystal for general morphological and defect studies, and It has e.g., primarily in the development of silicides. thin film, deposited has as an epitaxy been also interesting study: brush iron powder on a cobalt surface, and the iron will align One according to the magnetic domains in the cobalt specimen. itself H3P04, etched in acids, most commonly as electrolytic solutions: HCI, Etching: Easily and mixed acids. COBALT ETCHANTS co-0001 TIME: 2-3 min ETCH NAME: polish TEMP: RT TYPE: Electrolytic, Co ANODE: COMPOSITION: CATHODE: SS HCI ml 500 . . . . V POWER: 2 . EOH ml . . . 500 DISCUSSION: Co, (0001) wafers and with other orientations used in a study of growth habits. After in etching, boiling DI water, then rinse in alcohol and dry with hot air. wash REF: Cliffe, D R & Farr, J P G - J Electrochem Soc, 11 1,299(1964) CO-0002 TIME: NAME: Iron ETCH TEMP: RT TYPE: Metal, preferential COMPOSITION: Fe, powder ... x © 1991 by CRC Press LLC

329 316 CRC of Metal Etchants Handbook DISCUSSION: Co, and (0001) in a structure study. As cobalt is slightly other orientations wafers used brushing iron across specimen surfaces, the iron will align itself by magnetic, powder zones/domains. developing magnetic - Acta REF: Hall, E 6,l lO(19.58) 0 Metall, CO-0003 TIME: ETCH NAME: 5°C TEMP: TYPE: Electrolytic, polish ANODE: COMPOSITION: CATHODE: . HClO, . .. 23 POWER: 77 . . . . HAc DISCUSSION: (0001) wafers used to study stacking faults developed by nuclear magnetic resonance. Co, used to polish and was done electron microscope (EM). Solution an etch-thin with Study study. specimens for microscope 9,607(1964) J T - Phil Mag, Morgan, REF: - - -- co-0004 ETCH Neon TIME: NAME: Ionized gas, preferential TEMP: TYPE: GAS FLOW: COMPOSITION: x ... Ne+ ion PRESSURE: POWER: DISCUSSION: metals on Nef ion bombardment used in a study of etch figures obtained specimens. Co irradiation treatment. Other metals evaluated were Bi, Cd, Mg, Cu, Sn, and Zn. by Al, V E - Kristallografya, 2,770(1957) REF: Yurasova, CO-0005 NAME: Phosphoric acid TIME: ETCH Electrolytic, TYPE: TEMP: polish ANODE: COMPOSITION: CATHODE: . . . . H3P0, x POWER: DISCUSSION: Co 5/16" in diameter polished in the solution shown prior to oxidation experi- spheres cobalt has a structure transition 450°C. As and 400 at Oxidation was done in air ments. as expected, the oxidation patterns differentiated between the two structures: 420°C, at point 420°C, hexagonal, hcp, and above, cubic, fcc, oxidation figures were observed. below REF: V J & Leidheiser, H - J Chem Phys, 21,570(1953) Kehrer, PHYSICAL PROPERTIES OF COBALT OXIDE, COO Oxide Classification 27 & 8 numbers Atomic 74.9 Atomic weight 1935 Melting point ("C) Boiling point ("C) Density (g/cm3) Hardness (Mohs scratch) - © 1991 by CRC Press LLC

330 Crystal structure (isometric normal) - cube (100) Color (solid) Greenlbrown (pigment) Cobalt blue Cleavage (cubic) (00 1) OXIDE, COBALT COO a natural compound, although occur as are over 15 cobalt not General: Does there important ores are as sulfides and minerals. The has no major most arsenates. The oxide as in metal processing, but cobalt a compound important additive in the making use is an steels. The oxide does have application as a coloring agent (cobalt blue) in the glass and of and ceramics industries, a hydrogenation catalyst. There are four cobalt oxides, is used as monoxide being used the referent here. the as used but the mon- Solid State processing, not Technical Application: The oxides are in has grown and studied as a single crystal. oxide been and acid mixtures. Etching: HF ETCHANTS COBALT OXIDE COO-0001 5 min TIME: ETCH NAME: Hydrofluoric acid RT TEMP: TYPE: Acid, preferential COMPOSITION: ... HF x DISCUSSION: COO, (100) wafers. Cut and polish with diamond paste. Solution will mechanically lap develop dislocations and sub-boundaries. 14,328(1952) Soc, V W et a1 - J Am Ceram Nehring, REF: COO-0002 ETCH NAME: Heat TIME: 1000 K TYPE: Thermal, preferential TEMP: COMPOSITION: . . Heat . . x DISCUSSION: (100) wafers cleaved and strain annealed for use in a study of magnetic suscep- COO, degrees Kelvin. Pure in COO heat NiO. Note that temperature is shown and both tibility for to develop defects domain structures. used and Rev, J R - 104,929(1956) Phys Singer, REF: COO-0003 ETCH NAME: Oxygen TIME: TYPE: Gas oxidation TEMP: COMPOSITION: x 0, ... DISCUSSION: (100) wafers used in a study of COO, to Co,O,. Prepare specimens by (I) oxidation abrading surface with 800-grit Sic; (2) polishing with 0.5 diamond grit in kerosene, and (3) acetone with ultrasonic agitation prior to oxidizing. Process used in a study in washing oxidation mechanisms. of & Smeltzer, W W - J Electrochem Soc, 128,896(1981) K REF: Przybylski, © 1991 by CRC Press LLC

331 CRC of Metal Etchants Handbook 318 PROPERTIES OF COBALT PHYSICAL SULFIDE, Co3S4 Sulfide Classification & 16 27 numbers Atomic 305.06 weight Atomic 200 1 > ("C) Melting point point ("C) Boiling 4.85 (4.8-5) Density (g/cm3) 5.5 (Mohs - scratch) Hardness: fcc (100) cube, normal) - Crystal structure (isometric greytreddish Steel Color (solid) Cleavage (octahedral) (111) Co3S4 COBALT SULFIDE, as the mineral Co3S4, often associated with iron and copper General: Occurs linnaerite, and be an admixture with these as sulfides. Fairly widely distributed as ore deposits, may ore of cobalt with an No direct industrial use other structure analogous to the spinel group. than an ore of cobalt. as Not used in it is a Technical Application: Solid State processing at present, though mineral and may spinel-type an operating device. The reference have similar applications as a natural as Cogs,, and there are other cobalt sulfides, such as jaipurite, CoS is for shown mono-sulfide. mineral Etching: Soluble acids. in COBALT SULFIDE ETCHANTS COS-0001 Sulfurous acid TIME: ETCH NAME: TEMP: TYPE: Acid, preferential COMPOSITION: . . . . H2S03, conc. x DISCUSSION: fabricated as a single crystal sphere 0.28 mm in diameter, used in a study of Cogs,, was used crystal structure. The solution shown to develop defects and structure. REF: S Geller, Acta Metall, 15,1195(1962) - PROPERTIES OF COLEMANITE, Ca,B,O,,.SH,O PHYSICAL Borate Classification 5, 8, 2 25, Atomic numbers Atomic weight 396.4 - 1200 ("C) Melting point Boiling point ("C) Density (g/cm3) 2.42 - scratch) 4-4.5 Hardness (Mohs (1 10) prism Crystal structure (monoclinic - normal) Clearlwhitish Color (solid) Cleavage (b-pinacoidal) (0 10) COLEMANITE, Ca,B,O,,.SH,O General: Occurs as a natural mineral associated with borax, and was first discovered in Death Valley, California. It is mined along with borax and has similar medical and industrial © 1991 by CRC Press LLC

332 applications as and welding flux; as a washing and cleaning detergent; and as a soldering antiseptic or an preservative. been no in Solid State processing to date, although Technical Application: There has use and pyroelectric properties, as both the natural and been it has evaluated for ferroelectric synthetic crystal. Hot HCI. Etching: COLEMANITE ETCHANTS COL-0001 ETCH NAME: TIME: Hydrochloric acid Hot TYPE: Acid, removal TEMP: COMPOSITION: x ... HCl, conc. DISCUSSION: .5H,O, (010) cleaved wafers. Both the natural and CazB,O,, were artificial compound (010), pyroelectric properties. The material cleaves easily on studied for ferroelectric and is soluble in and HCI. et a1 H H J Appl Phys, 33,1720(1962) REF: Wieler, - OF COLUMBIUM, Cb PHYSICAL PROPERTIES (See NIOBIUM, Nb) COLUMBIUM, Cb a rare element not a native metal element. It is considered to General: Does occur as be which commonly is found in pegmatites as the mineral series columbite-tantalite. It is quite widely distributed and varies from nearly pure columbite to pure tantalite depending upon locale. When it was called columbium but, today, is called niobium. first discovered as industry used as the pure metal and been an alloy constituent in steels for In it has high temperature, hardness, and chemically inert characteristics. Items shown here are its See section on Niobium for physical properties and for references published as columbium. solutions and applications. additional The metal, as niobium, has some specific device development Technical Application: in Solid State device fabrication as the Josephson Junction device, applications NbzSn,. Etching: Hot HzS04, HF and mixed acids. ETCHANTS COLUMBIUM 1 CB-000 NAME: ETCH TIME: TYPE: Acid, polish TEMP: COMPOSITION: 2 HF ... . . . . 4 H,SO, 2 . . . . HNO, ... HF 2 DISCUSSION: Cb, single crystal specimens used in a study of anodic oxidation. Solution used to clean and polish to oxidation. Anodic solution used for oxidation was: 0.1 surfaces prior % H,P04 at 5.5 mA/cmZ. REF: Bakish, R - J Electrochem Soc, 107,653(1960) © 1991 by CRC Press LLC

333 CRC of Metal Etchants Handbook 320 CB-0002a ETCH NAME: TIME: TEMP: TYPE: RT Electrolytic, polish ANODE: COMPOSITION: CATHODE: H2S04 ml . . .. 90 POWER: 0.1 A/cm2 ... HF ml 10 DISCUSSION: Cb, used in a study of grain boundaries and etch pits. Solution single crystal specimens to and polish surfaces prior clean preferential etching. Use mild agitation during used to Solution also used on tantalum. etching. & Huegel, F J - Acta Metall, 5,339(1957) B Micheal, A REF: CB-0002b ETCH NAME: TIME: RT TEMP: TYPE: Acid, preferential COMPOSITION: ml ... HF 10 H,SO, . . . . ml 10 ... H20 ml 10 drops . . H20, x . . DISCUSSION: crystal specimens Cb, single in a study of grain boundaries and etch pits. Solution used used by immersion with agitation to develop sub-boundaries and etch pits. Etch pit density increased with time reduced in size. and pits Ibid. REF: CB-0003 ETCH NAME: TIME: polish TEMP: TYPE: Electrolytic, ANODE: COMPOSITION: HF ... 10 CATHODE: 90 H,04 ... POWER: DISCUSSION: single crystal alloys. Five crystals grown with increasing amounts of columbium: Ta:Cb. and of Material used in a study 80%. alloy strength. Solution used to clean 60, 30, 40, 20, polish specimens. and & Hendrickson, A A - Acta Metall, 14,1121(1966) REF: Peters, B C PHYSICAL PROPERTIES OF COPPER, Cu Classification Transition metal Atomic number 29 Atomic weight 63.57 point Melting ("C) 1083 ("C) point Boiling 2595 Density (g/cm3) (8.8-8.9) 8.94 Thermal conductance (cal/sec)(cm2)("C/cm) 0.94 (cal/g) 20°C Specific heat 0.0918 (caVg) fusion of Latent heat 48.9 (50.6) Heat (k-caVg-atom) of vaporization 72.8 Atomic volume (WID) 7.1 © 1991 by CRC Press LLC

334 I st ionization energy (k-callg-atom) (eV) ionization 1st potential Electronegativity (Pauling's) radius (angstroms) Covalent radius (angstroms) Ionic linear expansion thermal of Coefficient 20°C x lo-" ( cm/cm/"C) 0.593 ') Electrical conductance (micro ohm- 1.673 ( ohms cm) 20°C x Electrical resistivity 4.47 (eV) function work Electron 3.8 Cross section (barns) 2207 Vapor pressure ("C) 30,000 Tensile strength (psi) annealed 2.5-3 Hardness (Mohs scratch) - Crystal structure (isometric normal) fcc - (100) cube, Copper-red Color (solid) green (oxide) Emerald (flame) None Cleavage (parting, only) COPPER, Cu as a native element, usually of secondary origin and found in many General: Occurs seldom localities commercial quantities. It is found in beds and veins associated with but in azurite, as green copper ore, and such blue copper ore, both copper compounds, malachite, hydrated carbonates of copper. The iron being containing copper and sulfur, and the pyrites mineral cuprite, all occur veins. The symbol, Cu, is from the Latin cuprum, Cu,O, in copper from in (Cyprian bronze) as, comes ancient times, the island of which the Greek cyprium its copper mines. It is thought that copper was the first metal employed Cyprus was noted for man, after gold, as both occur in fair quantity in the free state of southern Europe and by Mediterranean the The two sulfides chalcopyrite, area. and chalcocite, represent CuFeS, Cu,S of 75% mined in the world. about the copper ore copper is ductile and malleable, like gold, Pure an excellent conductor of heat and and electricity are both gold and silver, all first used as as ornaments, plates, and other body utensils. Bronze, Cu:Sn, was the first metal alloy used by man, leading him out of the Stone Age into the Age about Bronze B.C. Brass, is not as brittle as bronze, and 5000 Cu:Zn, with 4000 B.C. but, the discovered in Egyptian tombs, circa said have are been artifacts to tin in Great Britain discovery of - Tin the ancient Rome Isles bronze was the major - of alloy until the discovery of iron metal by the Hittites of Asia Minor around 1350 smelting B.C. there are a large number of alloy mixtures of both bronze and brass. Today an one of the copper mined About the world is used for electrical wiring as third in alloy improve hardness. It is fabricated as rods, tubing, sheet, to as bulk material for and a wide number of products. As sheeting, it is used in building construction, such as a roof covering or as gutters which, with time and exposure to the atmosphere, can rain green turn - a copper sulfate. It also is available as high purity verdigris - copper (OFHC copper) in electronics and Solid State processing. Copper is easily electroplated, and many used are so plated. Gold, silver, products copper are known as the "coinage" metals, although and nickel is a lower cost replacement for silver. now In Solid State processing copper is Technical Application: as an n-type dopant in used some compound semiconductors. As a thin film metallization along with other metals, such well as in device construction as a contact pad on semiconductor devices as used as gold, for circuits on substrate dielectrics. It is as multilayer mixture such as AulCu; AuICulNi; AuICulCr; alternating layers CuIAu may be a series of or as of the two thin films. Used in © 1991 by CRC Press LLC

335 CRC of Metal Etchants Handbook 322 manner on such as aluminum, iron, steel, nickel, and molybdenum fab- a similar metals, parts and ricated as package elements. test by vacuum evaporation, E-beam evaporation, RF Thin standard be film deposits can by electrolytic sputter The latter method is used in plating from a solid target or plating. (PCBs) and some PC the metal parts used in test and package assembly. boards of copper wire or strap contacts, Solid parts, as copper alloys or OFHC copper, to include and pins are copper both their electrical used heat dissipation characteristics. As a or for copper is the coppertnickel coldweld or the weld packages, resistance as clad material, such metal. seal copper has been grown, as have several copper alloys, all studies for their Single crystal characteristics, and trinary compound semiconductors containing copper general physical study: are under CuInS,; and CuInTe,, as examples. CuInSe,; mixed FeCl,, HNO,, hot H2S04, slowly acids, HCl and NH,OH. in in Etching: Soluble and ionized gases. ETCHANTS COPPER cu-0001 ETCH NAME: Sodium hydroxide TIME: Alkali, cleaning TEMP: TYPE: COMPOSITION: ... x% NaOH (1) x (2) .. .. H,S04 2 1 ... HNO, DISCUSSION: Cu, coupons. Solutions used to clean copper wire prior to plating. First, clean wire and solution in water DI wash; follow with (2) acid mixture, and and water rinse. In (I), DI 0.001" before nickel plating. plating, initially deposit copper to A C G C & Ehitich, 50,453(1979) - J Appl Phys, Bailey, REF: cu-0002 TIME: 1 rnin ETCH NAME: Nitric acid removal TEMP: RT Acid, TYPE: COMPOSITION: . . . . HNO,, conc. x DISCUSSION: Cu, single crystal ingots cut as cylinder shaped specimens. Nitric acid was used to remove cutting work damage from surfaces. Jr - J Appl Phys, 35,1262(1964) REF: Reshon, D D CU-0003a TIME: 1-10 min ETCH Nitric acid, dilute NAME: Acid, cleaning TEMP: RT TYPE: COMPOSITION: 1 HNO, ... ... 20 H,O DISCUSSION: piping. Cu used for cleaning piping on Solution 2000 gallon LN, and LOX transport trailers. Included and bronze parts. Parts were soaked to remove general con- steel, brass, tamination, heavily blown dry with nitrogen. Where parts were stored or water washed and prepared for shipment they were sealed with warm nitrogen filled plastic bags. REF: Walker, P & Campos, R - personal application, 1962 © 1991 by CRC Press LLC

336 CU-0003b TIME: min 1-10 ETCH NAME: Hydrochloric acid, dilute TEMP: RT TYPE: Acid, cleaning COMPOSITION: 1 HCI ... 10 ... H20 DISCUSSION: Cu for general cleaning of steel, piping on cryogenic transport tailers. Solution used CU-0003a. parts. See discussion under brass bronze, and REF: Ibid. CU-0008a NAME: TIME: ETCH Nitric acid, dilute TEMP: Acid, cleaning TYPE: COMPOSITION: . . . . HNO, 1 1 ... H20 DISCUSSION: and Cu alloys. Solution used to remove copper oxide from parts prior to etch polishing Cu a Copper Brite Dip solution with (CU-0028). REF: ID, The American Brass Co. Bulletin B-1 - --- - CU-0004a Hydrochloric acid, dilute ETCH NAME: TIME: TYPE: Acid, cleaning TEMP: COMPOSITION: 1 ... HCl 1 ... H20 DISCUSSION: cold and Pure copper was annealed and alloys. drawn. Specimens were used in Cu Cu temperature transport properties. Solution used to clean specimens. a study of low L et al - Phys Rev, 1 15,314 (1959) R REF: Powell, cu-00 10 TIME: NAME: dilute Nitric ETCH acid, TEMP: TYPE: Acid, removal COMPOSITION: . . . x . HNO, ... H20 x DISCUSSION: Cu used in irradiation effect studies. Solution was used as a single crystal specimens general removal etch. Vook, R REF: & C - Phys Rev, 109,1529(1958) Wert, 9,237(1961) Hurdon, M J & Averbach, B L - Acta Metall, CU-0009a: Cu referred to as a "heavy etch" for copper and used single crystal specimens. Solution surface prior to studying dislocation density to clean in deformed specimens. Ferric chloride was used to develop dislocations and other structures after deformation. CU-0089: Magnuson, G D & Carlston, C E - J Appl Phys, 34,3267(1963) Cu used in an argon bombardment damage study. A weak solution single crystal wafers was used to remove lap damage prior 10 KeV Ar' ion sputter. © 1991 by CRC Press LLC

337 CRC of Metal Etchants Handbook 324 CU-001 la TIME: Dip ETCH NAME: Brilliant etch TEMP: RT TYPE: Acid, macro-etch COMPOSITION: . . . HNO, . ml 50 ml 0.5 ... AgNO, . H20 .. . 50 ml DISCUSSION: Cu Cu used to develop macro-structures on metallographic speci- and alloys. Solution mens. REF: Digest, #2,23(1983) - Buehler Ltd A/B 21 Metals CU-00 12 Silica TIME: Variable NAME: ETCH TYPE: Mineral, cleaning TEMP: RT COMPOSITION: . . . . SiO,, sand x ... H,O x DISCUSSION: parts sheet, pans and piping. For general removal of heavy contamination, such as Cu and dirt from copper and copper alloy surfaces. Method shown has been used as oxidation hand scouring of for As a dry abrasive using nitrogen for a pressure jet, used for parts. surface of other metal plating on copper parts, such as from power cleaning and removal used on other metal parts (steels, stainless steel, nickel) electrodes in vacuum systems. Also of vacuum systems to produce a rough surface for better adhesion of evaporating metals and reduction of on glass photo resist masks. chromium dusting during evaporation W - personal communication, 1975 H REF: Tam, CU-0013a NAME: TIME: ETCH Ferric chloride removal/preferential TEMP: TYPE: Salt, COMPOSITION: ... FeCI,, sat. sol. x DISCUSSION: single crystal spheres used in a study Cu surface plane development. Parts were first of cleaned dilute nitric acid before etching in this solution. in Economou, N A REF: Trivich, D - Electrochem Acta, 3,292(1961) & Ibid. CU-0009b: Cu single crystal specimens. A ferric chloride solution was used to develop dislocations and other structure after specimens were subjected to deformation. CU-0014 ETCH TIME: NAME: Ferric chloride, dilute removallpreferential TEMP: Hot Salt, TYPE: COMPOSITION: ASTM # 100 300 g . . .. FeCl, (2) 90 g . . . . FeCI, (1) 200 ml ... H20 1000 H20 ml . . . . DISCUSSION: and Cu alloy parts. Both solutions used as general removal Cu etchants on copper parts. - Phys Rev, 109,1964(1958) REF: Mackliet, C A Ibid. CU-0009~: © 1991 by CRC Press LLC

338 Cu single crystal specimens in a study of dislocation density after specimen de- used was used to dislocations and other formation. A dilute ferric chloride solution develop include structures. Also studied aluminum single crystals bulk deformation X-ray to study for observations. ASTM CU-0080a: E407-70 Cu, specimens. Standard ASTM is 10 #lo0 FeCI,:90 ml H20. solution g - --- CU-00 1 5 ETCH NAME: TIME: Acid, dislocation TEMP: TYPE: COMPOSITION: ... 1 M FeCI,.H20 I 1 ... M HCl 1 ... 0.25 HBr 1 M DISCUSSION: etch dbJocations and single crystal wafers of Cu used to various orientations. Solution in single crystal copper surfaces prior to irradiation studies. structures change observed No in but initial background terrace structure changed to a finely dislocations after irradiation, surface. Required several annealing periods, pitted etching after each anneal, to remove with surface pits. REF: Young, F W Jr - J Appl Phys, 33,749(1962) cu-ooO3c ETCH TIME: NAME: TEMP: TYPE: Acid, cleaning COMPOSITION: H2S0, 6 ... ... cro, 12 . H20 82 . . . DISCUSSION: cryogenic trailer piping, including brass, bronze and stainless steels. Solution used Cu as a "Brite Copper" dip. See for other similar solutions. Cu-0028 Ibid. REF: - cu-0043 NAME: TIME: 5-10 min ETCH cleanlcondition TEMP: RT Acid, TYPE: COMPOSITION: 5 . . . . FeCl, (40%) 10 ... HNO, 82 . H20 . . . DISCUSSION: cleaned Cu alloys as sheet Cu foil were and in this solution prior to being plastic or seal. adhesion plastic/metal to obtain a good surface cleanliness is essential laminated. Metal solution This of plastic sheet were evaluated gave the best adhesion results. Several types and also were applied to aluminum. I - Epoxy Resins, Reinhold, New York, 1950, 190 REF: Skeist, © 1991 by CRC Press LLC

339 326 CRC of Metal Etchants Handbook CU-00 18 TIME: ETCH NAME: TEMP: TYPE: Acid, preferential COMPOSITION: H2S04 . . . . x x . . . Cu(N02), . DISCUSSION: of different orientations Cu spheres. Various solution concen- single crystal wafers and were as the pH of evaluated affect characteristics of different crystal planes. trations solutions 1957 May, 12-16 a1 - Electrochem Soc Meet, WDC, et Gwathmey, REF: A T CU-0019a NAME: Copper sulfate, dilute ETCH TIME: TYPE: TEMP: Salt, preferential COMPOSITION: ... . x cuso, x ... H20 DISCUSSION: OFHC copper specimens. Solution used to develop structure caused by fatigue Cu cracking. - Acta Metall, 8,402(1960) REF: Bendler, H A cu-0020 ETCH NAME: TIME: TYPE: Acid, preferential TEMP: COMPOSITION: ... x cuso, . x . . . . H2S03 DISCUSSION: Cu single crystal wafers of different orientations and spheres were etched in various concentrations of solution in a study of crystallographic face orientation. this Chem Phys, T Benton, A F - J & 8,43 l(1940) REF: Gwathmey, A CU-0011 b NAME: General etch ETCH Swab TIME: Acid, micro-etch TEMP: RT TYPE: COMPOSITION: NH,OH 50 .. . . ml 50 . . . . H202 ml DISCUSSION: Cu and Cu alloy specimens. Metallographic specimen surfaces are lightly scrubbed with a swab soaked in solution shown to develop microstructure in material studies. the A/B 12,23(1983) 21 REF: - Buehler Ltd Metals Digest, CU-0022a ETCH NAME: Nitric acid, dilute TIME: TYPE: Acid, polish TEMP: COMPOSITION: .. . . HNO, x x ... H20 DISCUSSION: Cu single crystal specimens as spark-cut rods 6.5 cm long. Degrease, thermally anneal, © 1991 by CRC Press LLC

340 then electropolish phosphoric acid. After subjecting samples to strain, chemically polish in (1 11) surfaces and, although solution shown. This a high polish on in the solution produces crystal planes, the is well defined. After polishing specimens they attack other it does (1 11) dislocations and structures caused by strain. to were preferentially etched develop Z S & Basinski, S J - 9,51(1964) Mag, Phil Basinski, REF: al J Appl Phys, 32,369(1961) CU-0023: Magnuson, - G D et crystal spheres Cu a (1 10) orientation cut flats. Solution used to polish single with prior to spheres ion bombardment 20 During bombardment approximately Hg' km studies. material was and redeposited on the surfaces in hillock form. of removed CU-0024a TIME: sec ETCH NAME: 30 TEMP: RT TYPE: Acid, dislocation COMPOSITION: Br, (B) 45 . .. . HCI ... (A) 1 . . . . HAc 250 30 . . . H,O . DISCUSSION: Cu, (1 l), within 2-3" orientation. Mix the two solutions together when ready to use. 1 in size will etch pits that increase develop triangular surface linearly with etch time. Solution (Note: Surface damage etch pits increase in size; but dislocation etch pits normally do not.) D - J Appl Phys, 3,1071(1960) J REF: Livingston, CU-0025 ETCH NAME: min TIME: 5-10 TEMP: TYPE: RT Acid, dislocation COMPOSITION: . . . . HCI 20 ml 1ml HAc ... . . . FeC1,.6H20 . g 4 drops . . . 8 Br, . ... H,O ml 150 DISCUSSION: Cu wafers of various orientations. Specimens were point damaged using single crystal temperature a sapphire stylus deformed by high then annealing prior to etching in the and solution shown to develop dislocations and stress structures. REF: Bailey, Phys, M A T - J Appl Gwathmey, 31,215(1960) J & CU-0026 ETCH NAME: TIME: Acid, polish TYPE: RT TEMP: COMPOSITION: ml FeCI,, sat. sol. ... 75 ml 25 . . . HCI . DISCUSSION: Cu, (100) wafers. Solution has been used as both a polish etch, as well as a preferential type etch to internal (010) plane directions in a (100) surface. develop REF: Bums, J - Phys Rev, 119,102(1960) CU-0010b: Ibid. Cu single crystal wafers. Solution used as a polish etch. © 1991 by CRC Press LLC

341 CRC of Metal Etchants Handbook 328 CU-0008b TIME: ETCH NAME: acid, dilute Sulfuric TEMP: Acid, oxide removal TYPE: COMPOSITION: x ... H2S0, (12-15%) DISCUSSION: Cu alloys. Solution used as a pickling solution for the removal of scale and Cu and surfaces. from copper oxides REF: Ibid. CU-0008~ TIME: NAME: Dichromate finish dip ETCH polish TYPE: Acid, TEMP: COMPOSITION: . . . . H2S04 12 oz oz . . . . NaCrO, 4 ... 1 gal H20 DISCUSSION: Cu alloys. Solution will remove heavy oxides and leave a matte type surface and Cu finish. Ibid. REF: -- - CU-0027 NAME: ETCH TIME: TYPE: Acid, removal TEMP: COMPOSITION: (1) 1 HNO, ... 40 . ... NH, (2) H202 10 . ... ... 20 H202 DISCUSSION: removaVpolish etchants for copper. Cu and alloys. Both solutions shown as general Cu & Pitman & Dearden, WH - Metallographer's Handbook of Etching, Berglund, T REF: London, 1931 Sons, CU-0005a Phosphoric acid ETCH TIME: NAME: TYPE: Electrolytic, polish TEMP: 70-178°C COMPOSITION: ANODE: CATHODE: .. . H,P04 . x POWER: DISCUSSION: single crystal spheres used in a study Cu oxidation reactions. Electropolish in solution of to oxidation. vacuum prior xHN0,:EOH; and H+ ion clean in in shown; chemical clean Young, F W Jr et REF: a1 Acta Metall, 4,145(1956) - CU-0006: Young, F W Jr - J Appl Phys, 32,192(1961) different Cu single crystal waters and in a wide range study of the effect of used spheres etch solutions on development of dislocation etch pits. CU-0007: Young, F W Jr - Bull Am Phys Soc, 5,190(1960) Cu single crystal wafers and spheres a study of dislocation variation in structure used in flats. oriented contained (1 1 1), (1 10) and (100) surface planes. Spheres to related as © 1991 by CRC Press LLC

342 CU-0028 Seconds TIME: Brite dip NAME: ETCH Copper RT TEMP: polish TYPE: Acid, COMPOSITION: 7 3 2gal 250ml 5 3...H,S04 600ml 3 ]gal 125ml 7 250ml l...HNO, 1 0 0 5 ... ml '1, fl oz 4 ml HCI 20 0 250ml 1-2qt 130ml 1 10 2 l...H,O DISCUSSION: (1) De- The following cleaning procedure is recommended: Cu specimens and parts. dry, TCE Dl hot rinse - MeOH rinse - N, blow - then (2) NH40H dip grease: (i) H,O RT to remove native oxide at DI H,O rinse - MeOH rinse, and - blow dry. All of N, - dip in solution - immediate water quench and rinse. rapid the solutions are extremely of a highly surface that may not be planar due to rapidity polished Produces reflective, (1) Not recommended where critical dimensional tolerances are required. Solution attack. to clean copper vacuum system parts and copper electrical test holders for microelec- used clean boards (PCBs). plated PC tronic devices. Also to copper personal communication, 1979 - (1) Fahr, F REF: (2) Walker, P & Fahr, F - personal application, 1979-1980 CU-0029a: OFHC copper parts used as microelectronic device test carriers. Solution used to Cu, "bum" marks from machine cutting. Solution was too rapid and erratic to remove residual maintain critical dimensions. Hydrogen firing at 300 to 4W°C was satisfactory. Parts more plating. AulNi prior cleaned to Westinghouse Data Sheet (date, number unknown) specimens and parts. (3) Cu CU-0030: Solution applied for general polishing. Metals Handbook ASTM 8th ed, 1974 Cu specimens and parts. Solution #2, CU-0031: (4) applied as a general polishing etch. CU-0032: (5) Kohl, W H Handbook of Materials and Techniques for Vacuum Devices, - Reinhold, New 1967 Cu specimens parts. Applied as a general polishing solution. York, date) (6) Bulletin the American Brass Company (no ID, Cu specimens and CU-0008e: B-1 as a general polishing parts. Described and copper alloys. solution for copper CU-0087: Chen, H (7) - Y Electrochem Soc, 1 18,681(1971) J Cu, OFHC copper discs used as cathodes for electrolytic plating of gold from gel sec, RT. Two electrolytes. Degrease copper acetone and Brite Dip 10 parts TCE, then with pm used in both acidic and cyanide cellulose compounds solutions. 0.5 gold for gelling and deposits evaluated. Deposit rates gold were (1) at 0.15 mA/in2, 2 pm/h, thick (2) at of 0.15 mA/in2, 0.6 p,rn/h. Electrographic porocity meter and pore printing used to evaluate Ib/in2 - at 8 V and 800 pore print pressure. deposits CU-0029b: Ibid. Cu, OFHC copper parts, after AuINi plating (Au 2000 A:N~ 500 A). Solution (1) used at pinholing, grain struc- (icelacetone) to evaluate completeness of metallization and/or 8OC ture, and grain boundary diffusion of liquids. © 1991 by CRC Press LLC

343 CRC of Metal Etchants Handbook 330 CU-0008d TIME: Matte dip ETCH NAME: TEMP: TYPE: Acid, finishing COMPOSITION: 2 H,S04 . . . . HN03 . . . . 1 . x . . . *ZnO or ZnS solution *Saturate the DISCUSSION: and alloy parts. For decorative purposes the solution will produce a matte type Cu Cu with finish and beaded structure. surface dull reflectivity REF: Ibid. CU-0032 min TIME: 15 ETCH NAME: Ammonium persulfate Salt, cleaning RT TYPE: TEMP: COMPOSITION: ... (NH4),S208 x 2-5% DISCUSSION: and other Cu, (1 Solution used to clean surfaces 11) single crystal blanks orientations. prior to oxidation experiments (Cu,O). REF: J P et a1 - Acta Metall, 103,273(1956) Baur, CU-0019c: Ibid. a study copper single crystal specimens Cu, OFHC of the formation of fatigue used in cracks using an electron microscope (EM) for observation. An ammonium sulfate solution was used cracks. to develop CU-0024b ETCH NAME: TIME: polish Electrolytic, TEMP: TYPE: COMPOSITION: ANODE: CATHODE: .. H,P04 . 60 . 40 H,O POWER: ... DISCUSSION: Cu, used (111) wafers a study dislocations. etch pits associated with in Solution of was used to electropolish specimens before preferential etching. shown REF: Livingston, J D - J Appl Phys, 3 1,1071(1960) cu-0024c ETCH NAME: sec TIME: 30 Acid, preferential RT TYPE: TEMP: COMPOSITION: 45 . . . HCl . ... HAc 30 250 . ... H,O 1 ... Br, DISCUSSION: with Cu, (1 11) to develop etch pits associated used dislocations. Mix wafers. Solution the Br, + HAc, first; then add to the HCl:H,O. Pits observed contained flat bottoms and © 1991 by CRC Press LLC

344 varied from to large in size as sharply defined triangles. Solution referred to as a small Wernick etch. & of modification a Lovell REF: Ibid. CU-0069 NAME: ETCH TIME: TYPE: Acid, cleaning TEMP: COMPOSITION: . . x . . HNO, H,O ... x DISCUSSION: used in a study of Cu in electron irradiated copper. single crystal specimens recovery nitric was used to clean and wash surfaces. Dilute acid Corbett REF: W et a1 - Phys Rev, 114,1452(1959) J Bendler, H A - Acta Metall, 8,402(1960) CU-0019b0: Cu of OFHC copper used in an electron microscope study of fatigue single crystals etchant. a crack selective acid solution was used as A dilute nitric and cracks their formation. used ammonium persulfate solutions. Also - -- - -- 1 a CU-006 NAME: Nitric acid TIME: ETCH - 20°C or less TEMP: TYPE: Electrolytic, thinlpolish ANODE: Cu COMPOSITION: CATHODE: x . . HNO, (33%) . . POWER: DISCUSSION: Cu foil. Solution used was a double-jet to polish and thin copper for TEM study. Copper specimens were also nickel plated; palladium and platinum immersion plated; electroless evaporated with gold in of thin films and deposition reactions. Final coating of and a study was done as part of a thin film adhesion study. Nickel all metals with electroless nickel also rapidly on Pd than unplated Cu. plates more Flis, REF: & DuOette, J - J Electrochem Soc, 131,254(1984) J CU-0022b ETCH Phosphoric acid TIME: NAME: Electrolytic, polish TYPE: TEMP: ANODE: COMPOSITION: CATHODE: x H,PO, . . . . POWER: DISCUSSION: Cu single crystal specimens. First, spark-cut as rods, then etch polish in the solution shown prior thermal annealing to reduce dislocation content. to Ibid. REF: Inman, M C & Barr, CU-0074a W - Acta Metall, 8,112(1960) L Cu single crystals were cut as cylinders and electropolished in the solution shown in a study antimony diffusion into copper. of CU0024d: Ibid. a dislocation study. First, in used plane. Wafers 2-3" of within 11) wafers Cu, (1 cut etch polish in solution shown before dislocation etching (CU-0024a). © 1991 by CRC Press LLC

345 CRC of Metal Etchants Handbook 332 CU-006 1 b ETCH NAME: TIME: 0°C TEMP: TYPE: Electrolytic, polish ANODE: Cu COMPOSITION: . HNO, . .. x CATHODE: . . POWER: 6 V . . MeOH x DISCUSSION: Cu, foil. See discussion under used to electropolish copper before CU-0061a. Solution sequences plating a study of nickel adhesion. various in REF: Ibid. CU-0062a ETCH TIME: Toluene NAME: TEMP: TYPE: Ester, cleaning COMPOSITION: x .. . . C,H,CH, DISCUSSION: specimens. Solution used in a study of surface cleaning. Toluene is excellent for Cu of removal as palmitic, stearic and oleic acids from copper and gold surfaces. fatty acids, such say that than one monolayer of contamination remains. Fatty acids were less Authors 51C isotope tagged. 10,167(1961) G D et a1 - Int J Appl Radiat Isot, Fatzer, REF: - --- cu-0063 NAME: Ethyl alcohol TIME: ETCH TEMP: TYPE: Alcohol, cleaning COMPOSITION: x ... EOH DISCUSSION: study. First, blanks as Cu, used for a metallization, stress and failure plated substrates ultrasonically clean in EOH, then Ar+ ion sputter clean in vacuum prior to CVD deposition of Ni, and Ti with copper substrates at and increased to 350°C. Metallizations A120, 200°C, up A1203/Cu; Al,O,/Ti/Cu, was (3) Al,O,/Ti/Ni/Cu. Tensile strain (2) to 10% and (1) were observed. After metallization, temperature cycle increased to 600°C. Alumina showed par- cracks after deposition and was allel amorphous, a-Al,03, 400--450°C. Without a below interface alumina and copper, alumina peels from copper. metal between Jarvinen R et a1 - REF: Solid Films, 114,31 l(1984) Thin CU-0064: Walker, P & Velardi, N - personal application, 1985 Cu, OFHC copper parts. After gold plating of parts and DI water washing, final rinse for final with or ethanol and nitrogen blow dry. Used either methanol cleaning then acetone, drying of parts. and CU-0065a NAME: Trichloroethylene TIME: Minutes ETCH Solvent, cleaning 75-80°C TEMP: TYPE: COMPOSITION: x TCE ... DISCUSSION: is a and other metals and compounds. TCE Cu, OFHC parts, semiconductor packages, general degreasing solvent as a liquid, hot or cold, with or without ultrasonic agitation, used as a spray or hot vapor. The latter as vapor degreasers. Vapor degreaser systems can be from a beaker on a hot plate to large tanks with overhead cranes for handling large parts, © 1991 by CRC Press LLC

346 and operate with of hot liquid (in an ultrasonic tank), hot vapor head above a combination a mobile spray nozzle. Where the part is cleaned a vapor degreaser, working tank, and in a hot will dry pulled from the hot vapor head. Where used as it is slowly or cold as part the liquid, after degreasing, then rinse in acetone, then MeOH DI EOH, and water wash or blow is considered carcinogenic and is being replaced by 1-1-1 nitrogen dry. TCE trichlo- TCA. roethane, been used for gross leak testing of hermetically sealed pack- TCE also has ages. REF: Walker, - personal application, 1970-1985 P CU-0065b TIME: Minutes ETCH TA NAME: Freon TEMP: 75 to 85°C TYPE: Solvent, cleaning COMPOSITION: x Freon TA . . . . DISCUSSION: OFHC copper parts, semiconductors other metals or compounds. Solution Cu, used and a similar as that described for TCE in manner (CU-0065a). There are several Freon mixtures various alcohol additives to include aziotropes, such as with TF, Freon TM, etc. Freon Freon a Dupont registered trade name, and other manufacturers have similar solutions is own trade names, such as the Genusolves (Allied Chemical), etc. Freons evaporate with their or completely, leaving no residual on cleaned surfaces, such contamination from the solvent that they are of major use in the cleaning of semiconductor and assembly parts. Freons are also used leak testing of hermetically sealed packages as, if as special mixtures for gross is a leak, the solution completely evaporates; whereas TCE so there and similar solvents leave can used a residue within the package. REF: Ibid. cu-0033 TIME: 3-10 min ETCH NAME: Acid, TYPE: TEMP: polishlclean RT COMPOSITION: 20 . . . 2NH,NO, .Ce(NO,), .4H20 g . ml ... HNO, 10 150 ml ... H,O DISCUSSION: Cu, wire and OFHC copper parts. This solution is similar to commercial "chrome etch" formulations and was developed for use on chromium evaporated on soda-lime glass as and parts. photo resist be used on both nickel as well as copper thin films it can masks, but The solution a very slow polishing and is and useful where part cleaning etch for copper dimensions are critical. By varying the nitric acid content, removal rates can be closely controlled on the angstroms/minute level. application, 1975 and - personal development P Walker, REF: CU-0067 TIME: ETCH NAME: TEMP: TYPE: Acid, preferential COMPOSITION: . . . . HNO, 1 10 H20 ... © 1991 by CRC Press LLC

347 CRC of Metal Etchants Handbook 334 DISCUSSION: Cu, a study of grain boundary diffusion. Specimens wet cut and bicrystals used in lapped with in the solution shown to develop grain and then etched alumina 600-grit boundary structure. Austin, REF: & Richard, N A - J A Phys, 32,1462(1961) E Appl ~ cu-0034 min TIME: 1-10 Nitric ETCH acid NAME: TEMP: RT Acid, cleaning TYPE: COMPOSITION: (1) x HNO, (2) 1 . ... HNO, ... 25 ... H,O DISCUSSION: piping used in parts. cryogenic Solutions and parts of Copper polycrystalline cleaning and LN, transport trailers. Also copper as a general cleaner for copper used gallon 200 alloys. cleaning, 1962 & Walker, P - cryogenic parts Campo, F REF: cu-0035 ETCH NAME: Potassium cyanide TIME: TYPE: Acid, removal TEMP: COMPOSITION: x 20% KCN ... DISCUSSION: Cu, films. Solution used to remove copper thin Ge, Si, and copper from surfaces. GaAs - personal communication, 1984 REF: Valardi, N CU-0036a TIME: 5 min NAME: acid, dilute ETCH Nitric polish TEMP: RT TYPE: Acid, COMPOSITION: 1 ... HNO, 1 ... H,O DISCUSSION: Cu single crystal specimens used in a study of plastic flow at 90 and 170°C. Solution used as a polishing etch. Acta Metall, 6,338(1958) - Conrad, H REF: CU-0036b NAME: TIME: 45 min ETCH - 10 to O°C TEMP: Electrolytic, polish TYPE: COMPOSITION: ANODE: CATHODE: ... HNO, 1 POWER: ... MeOH 2 DISCUSSION: Cu single crystal specimens. After etching rinse in (1) tap water, (2) water, (3) D1 acetone rinse, and (4) air dry. REF: Ibid. © 1991 by CRC Press LLC

348 CU-0037 ETCH NAME: TIME: TYPE: Acid, sizing TEMP: COMPOSITION: x . . 30% HNO, . . DISCUSSION: surface effects used in a study of specimens on plastic properties. Cu single crystal to required dimensions. (Note: This use of the term "sizing" Solution used to etch specimens a physical action, the use of chemicals as size in reducing ink running in paper.) not reflects Rosi, F D REF: - Acta Metall, 5,349(1957) CU-0038a ETCH NAME: TIME: Electrolytic, polish TEMP: TYPE: ANODE: COMPOSITION: CATHODE: x H,PO, . . . . POWER: DISCUSSION: crystal spheres used in a study of oxidation on smooth convex surfaces. single Cu oxide with shown, then etched to remove the solution cutting Spheres were polished after controlled oxidation. before Harris, REF: W W al - Acta Metall, 5,574(1957) et CU-0038b ETCH NAME: 5-10 TIME: min Electrolytic, oxide removal TEMP: TYPE: ANODE: COMPOSITION: CATHODE: x KCI, sat. sol. ... POWER: 30-50 mA/cm3 & 5-10 V DISCUSSION: Cu crystal spheres. Solution used to remove native oxide left after electropolishing single phosphoric acid controlled oxidation. in before Ibid. REF: CU-0039: Evans, U R J - & Chem Soc, 2,651(1929) Stockdale, J for etchants shown in CU-0038a and CU-0038b. Reference Phelps, R T et a! - Ind Eng Chem Anal Ed, 18 1,391 (1948) CU-0040: specimens. Used solution to remove native oxide from parts. Cu - Greenfield, I G Wildorf, CU-0041a: G F & J Appl Phys, 32,827(1961) H oxide. specimens. Used solution to clean copper surfaces of residual Cu a 1 CU-004 NAME: acid, dilute TIME: ETCH Phosphoric TYPE: Electrolytic, polish TEMP: ANODE: COMPOSITION: CATHODE: . . .. H,PO, I I ... H,O POWER: DISCUSSION: Cu single crystal specimens used in a study of the effects of neutron irradiation on plastic deformation. Solution to polish specimens before irradiation. used REF: Greenfield, I & Wilsdorf, H G F - J Appl Phys, 32,827(1961) © 1991 by CRC Press LLC

349 336 CRC of Metal Etchants Handbook CU-0024e ETCH acid, dilute NAME: Phosphoric TIME: Electrolytic, polish TYPE: TEMP: COMPOSITION: ANODE: . H,PO, CATHODE: 60 . . . POWER: ... H,O 40 DISCUSSION: Cu, in an etch pit and dislocation (1 Solution used to polish 11) wafers used study. CU-0024a). to surfaces prior preferential etching (See REF: Ibid. J & Whitmore, CU-0044: - R T Phys Chem Solids, 31 ,I 15(1960) Moser, J single crystal hemispheres grown or Cu from a rod. Specimens were thermally machined etched high temperature in vacuum to develop facets, spirals, and etch pits. Solution at used polish specimens prior to thermal treatment. shown to cu-0042 ETCH NAME: Neon TIME: Ionized gas, preferential TEMP: TYPE: GAS COMPOSITION: FLOW: ... Ne+ ions PRESSURE: x POWER: DISCUSSION: single crystal specimens. Neon ion Cu used to develop structure and bombardment orientation figures. Other metals studied were Al, Bi, Cd, Co, Mg, Sn, and Zn. REF: Yurasova, V - Kristallografiya, 2,770(1957) E CU-0024g ETCH 30 sec NAME: TIME: TEMP: TYPE: Acid, dislocation RT COMPOSITION: HCl ... 45 30 HAc ... 250 ... . H,O ... Br, 1 DISCUSSION: Cu, single crystal wafers within (1 11) of 2-3" orientation. Solution develops triangular CU-0043a.) and pits increase in size, linearly, etch etch time. (See pits with REF: Ibid. cu-0045 ETCH NAME: TIME: TYPE: Acid, TEMP: 70°C polish COMPOSITION: 1 . H,PO, ... ... 1 HNO, 1 ... HAc DISCUSSION: Cu single crystal specimens. Etch polish in the solution shown. Specimens used in a study ductile fracture. of REF: Saimoto, S et a1 - Phil Mag, 12,3 19(1965) CU-0046: Ebeling, R & Ashby, M F - Phil Mag, 13,437(1966) © 1991 by CRC Press LLC

350 Cu single crystal specimens. as shown above. Specimens used in a study Etch polished dispersion hardening. of - - -- - -- cu-0047 TIME: min ETCH NAME: 1-2 TYPE: Acid, removal TEMP: 60-70°C COMPOSITION: . . . . ml H3P04 33 . . . . HNO, 33 ml . . . . HAc 33 ml DISCUSSION: specimens used in an etching study. The solution will remove copper and copper Cu and is particularly good for oxide removal. oxide, J - Metalen, 9,2,(1954) (in Dutch) J REF: de Jong, Tegart, CU-0073: Etching The Electrolytic and Chemical WJ of Metals, Pergamon - McG Press, England, 1956 specimens. Solution described as a polish etch for copper, and a removal etch for Cu oxide. Cu,O CU-0048 NAME: TIME: ETCH TEMP: TYPE: Acid, oxidation COMPOSITION: x . . . . cuso, + ... 0, DISCUSSION: Cu single crystal sphere ground to shape and electropolished with (1 1 (loo), (1 lo), l), and (210) flats lapped and polished. Mixture was used to oxidize surfaces in shown (31 1) growth spirals in of a study Cu,O. Miller, G T & Lawless, K R - J Appl Phys, REF: 29,863(1958) cu-0011c ALN3-1 ETCH NAME: TIME: Dip TEMP: RT TYPE: Acid, macro-, micro-etch COMPOSITION: 5 . . . . HNO, ml 5 ml . . . . H,S04 4 g ... cro, 1 g . . . . NH4Cl 90 ml . . . H,O . DISCUSSION: micro-etch depending and copper alloys. Solution is Cu a macro- or specimens both upon type alloy and used in a material structure study. REF: Ibid. CU-0011d TIME: Swab 1 ETCH NAME: Geard # TEMP: RT Acid, preferential TYPE: COMPOSITION: 5 ... HCl ml FeCI, 20 g ... H,O ... ml 100 © 1991 by CRC Press LLC

351 CRC of Metal Etchants Handbook 338 DISCUSSION: Cu, copper alloys. A general micro- or macro-etch on most alloys of specimens and by swabbing the copper. Apply surface. Ibid. REF: CU-0069 ETCH Smog TIME: NAME: corrosion TEMP: TYPE: Gas, COMPOSITION: x ... SO,, H,S, O,, HCI, CI,, vapor) Air (+ x . . H,O, vapor (as RH) . . DISCUSSION: specimens used in a study of atmospheric corrosion using an artificially developed Cu with with vapor as humidity factor. Also studied silver water same smog smog variable but in dry air. atmosphere, a1 D W et 128,275(1981) - J Electrochem Soc, REF: Rice, CU-0050b ETCH TIME: NAME: Electrolytic, polish TEMP: TYPE: ANODE: COMPOSITION: CATHODE: x . . . . HNO, x ... EOH POWER: DISCUSSION: CU-0050a for discussion. as a polish etch. See Cu Solution used single crystal spheres. REF: Ibid. CU-005 1 TIME: ETCH NAME: TEMP: forming TYPE: Thermal, COMPOSITION: x ... heat DISCUSSION: single crystal spheres formed by asymmetric cooling of copper on a tungsten ribbon Cu a copper sphere. high vacuum. Used of tungsten carbide growth on oxidation study in an in - Z Naturforsch, 122,1003(1957) C REF: Menael-Kopp, cu-0060 TIME: Variable NAME: Ammonium peroxydisulfate ETCH TYPE: Salt, TEMP: 45°C polish COMPOSITION: x x% (NH,),S,O, ... + . . . HgC12/PdCI, . DISCUSSION: Cu specimens used in a study of the effects of the solution shown. The addition of metal salts increase the removal rate. (Note: Solution also called ammonium persulfate.) will 2,118(1964) Technol, D & Diggery, B A - Electrochem Schlabach, T REF: © 1991 by CRC Press LLC

352 CU-006 1 NAME: ETCH TIME: 15-40 h TEMP: polish TYPE: Electrolytic, ANODE: Cu specimen COMPOSITION: H3P0, CATHODE: Cu sheet 600 ml ... CUO POWER: 1 .O- 1.1 V ... g 12.9-19 . . . . H20 RATE: 0.01-0.2 pnlmin 400 ml DISCUSSION: still HNO,, rinse in water and while introduce wet in specimens Cu specimens. First, dip Hold specimen surface in a horizontal position during etching. into solution shown above. H3P04, 30 sec. With 12.5 g CuO and with potential still applied, After in etching, rinse high copper specimens gave the best results. There were some parallel ripples on purity A in height. less than surfaces 100 - Electrochem Technol, 2,274(1964) W Powers, R REF: CU-0068 NAME: Chlorine TIME: ETCH Gas, TYPE: removal See discussion TEMP: COMPOSITION: vapor . . . Cl,, . x DISCUSSION: 3" of orientation, with some twinning observed, Cu, (100) single crystal within wafers cut were a study of the surface reactions with chlorine gas. Three general reactions were used in observed at temperature levels: different less than 150°C, growth; (2) 150-580°C, (1) CuCl a gas, gas. (3) above 650°C, CuCl as as and Cu3C13, Technol, J Vac Sci - A(3),786(1985) REF: Winters, H F CU-0013b TIME: ETCH NAME: TEMP: preferential Acid, TYPE: COMPOSITION: HCI ... 1 ... H20 1 x ... *FeC13 the solution. *Saturate DISCUSSION: 1 cm diameter. After polishing with nitric acid and then ferric Cu, single crystal sphere chloride, the solution shown was used to preferentially etch. Developed (001) pole figures. REF: Ibid. CU-0052 TIME: Variable ETCH NAME: Copper sulfate TYPE: Acid, oxidation TEMP: RT COMPOSITION: x . . . 50 gll CuS04.5H20 pH: 3.8 . DISCUSSION: 1) (31 and 5/, and 3/," diameter with (100), (1 lo), (1 1 l), (012). spheres crystal Cu, single epitaxy relationships used in a study flats. Solution to oxidize surfaces of of Cu20. In 5 min a general orientation pattern will form; 24-60 h oxide will show pitting; 5 sec to 90 © 1991 by CRC Press LLC

353 340 Handbook Metal Etchants CRC of crystals form. in the solution, wash in DI water and After oxidizing spheres h and Cu20 nitrogen. with dry blow REF: Lawless, K R G T Jr - Acta Crystallogr, 12,594(1959) & Miller, -- - cu-0053 TIME: ETCH NAME: Thermal, forming TEMP: TYPE: COMPOSITION: . . . x . heat DISCUSSION: Cu, single crystal spheres formed by melting the tip of single crystal wire. Wire was mm diameter; spheres, 2-3 mm diameter. Other materials used were Ag and Au. 1-2 K & Gerisder, H - J Electrochem Soc, 110,350(1963) REF: Rose, D J F & Gwathmey, A T - W Appl Phys, 31,225(1960) CU-0086: Young, single crystal specimens. Heating in ultra high vacuum (UHV) develops facets and Cu, etch pits. spiral 1 b CU-007 ETCH NAME: Water TIME: Acid, float-off TEMP: TYPE; COMPOSITION: ... H20 x DISCUSSION: Cu, evaporated on NaCl, (100) substrates in a general study of thin film thin films by by deposition, copper was removed After film dissolving the NaCl surface TEM. defects (0001) water using float-off technique. Copper thin films deposited on mica, with the were removed A study of copper structure. substrates with 10% HF. Ibid. REF: 1 a CU-007 NAME: TIME: ETCH Deformation, defect TEMP: TYPE: COMPOSITION: stress .. . . x DISCUSSION: slip caused single in a study of secondary used by stress deformation. Cu, crystals Secondary nucleates at the end of primary slip lines when the internal stress fields are slip high. Also studied single crystal alpha-brass. Mag, & Thornton, P R -Phil 10,314(1964) T E REF: Mitchell, CU-0062b ETCH NAME: TIME: Acid, cleaning TYPE: TEMP: COMPOSITION: 1 ... H2S0, 1 . . . . *K,Cr,O, © 1991 by CRC Press LLC

354 DISCUSSION: Cu, crystals used in a cleaning study. The solution shown was radiotracer tagged single with 35S isotopes and used as a surface cleaning etch. and 5'Cr 0 D et - Int J Appl Radiat & Isot, 10,167(1961) a1 REF: Fatzer, CU-0062~ 2 min ETCH TIME: NAME: TEMP: 120°C Electrolytic, TYPE: polish Cu COMPOSITION: ANODE: ... x% CATHODE: x CrO, POWER: DISCUSSION: Cu under specimens. See discussion CU-0062a and CU-0062b. REF: Ibid. CU-0085 TIME: 60 min ETCH NAME: TYPE: Acid, cutting TEMP: RT COMPOSITION: (1) ml . . . 200 HCI (2) 1 ... HNO, . g 50 FeC1, ... H,O . 1 . . . . 250 . . H,O ml . DISCUSSION: copper, I/," thick. Terylene thread soaked in solution (1) used to cut specimens Cu and brass. Solution (2) used for tin and zinc. (Note: Excellent review of metal aluminum methods.) growth Honeycombe, R W REF: - Rev, 4,1(1959) K Metal1 CU-0087 ETCH TIME: NAME: Argon TYPE: Ionized gas, cleaning TEMP: COMPOSITION: GAS FLOW: x ... ions PRESSURE: AT+ POWER: DISCUSSION: wafers used as substrates for thin film deposition of copper by 11) condensation Cu, (1 Ar+ cleaned bombardment ion which can were Substrates produce twinning. of metallic vapor to copper deposition. Epitaxy growth of copper evaporated at an prior as a function angle showed the greater the angle, the greater the increase of twinning observed. (Note: that normal Growth of produce a columnar growth structure rather than will silica at an angle amorphous thin films.) REF: Lafourcado, L et a1 - C R Acad Sci (Paris), 249,230(1959) CU-0088: Yurasova, E - Zh Tekh Fiz, 28,1966(1958) V single crystal Cathode positive sputtering as ion bombardment used in Cu, specimens. of surface micro-relief and a study Etch pits observed in Cu and Zn and slip traces erosion. on deformed Zn. COPPER ALLOYS General: Copper occurs as a native element as well as in a number of single crystal metallic compounds: horsfordite, Cu,Sb; mohawkite, Cu,As; rickardite, Cu,Te,; barzelianite, copper The two major copper sulfides are chalcocite, Cu,S and covellite, CuS. The Cu,Se. sulfides: iron bornite, CuFeS, and chalcopyrite, CuFeS,. The latter mineral structure is a © 1991 by CRC Press LLC

355 342 CRC of Metal Etchants Handbook for the ternary chalcogenides. Possible the two most well known copper base artificial to their brilliant colors, are copper carbonates: malachite (green) and minerals, due the being primary copper well as semi-precious gem stones. Cuprite, (blue), both azurite ores as the major oxide of copper, also an ore as are all the copper alloy compounds Cu,O, is in vein deposits alone, or are associated with iron. mentioned. They occur artificial alloys copper, the two most well known being bronze, many of There are Cu:Zn. Mixtures Cu:Sn Cu:Sn:Zn are used for bell metal and gun metal, and and brass, of are special mixtures such as phosphor-bronze; silicon bronze; manganese bronze. There there similar alloys are brass: cartridge brass, wire brass, aluminum brass, etc., and mixtures of of ductile the alloys referred to as heavy metal. As pure copper is soft, of Cu:W are some malleable it is usually used in some form of alloy for strengthening purposes, although and copper, the highest purity form of copper, has application for its low electrical OFHC and resistance dissipation characteristics. heat many copper and copper alloys in Solid Technical Application: There are uses for pure material processing as evaporated contact pads in device fabrication, as State as- package sembly and, of major importance parts PCBs (laminated plastic linen boards, today, as copper plated) used to hold electronic circuit assemblies for computers and similar products. Such boards of being inserted and removed in a variety of equipment, and are are capable used widely of operating functions. in the miniaturization and brass are copper as test blocks for mounting semiconductor devices. OFHC both used parts; Cu:W alloys, are used as physical weights for belt furnace alloying of metal, Heavy phosphor-bronze, sheet is cut and used as holding spring clips for both metal Cu:Sn:P, of is a flat plate, or devices on a test plate, as evaporation Cu:Be. There are wafers on and polyimide pastes containing copper powder as one constituent for use as electrical epoxy contact materials, e.g., "loaded" epoxies. Several binary and trinary copper alloys have been grown and studied as single crystals for general morphology and structure. There are also and and quarternary sulfide trinary selenide compound semiconductors containing copper. type with H,PO,, and mixed acids, variable alloy. HNO,, Etching: Soluble in ETCHANTS ALLOY COPPER C0PPER:ANTIMONY ETCHANTS CUSB-0001 Nital ETCH NAME: TIME: TYPE: Acid, preferential TEMP: COMPOSITION: x . .. . HN03 x . . EOHIMeOH (H,O) . . DISCUSSION: be SbAu,Sb Cu,Sb, could and observed on material without etch- specimens. Structure ing. Solution shown was used to accentuate defects and structure. REF: Savas, M A & Smith, R W - J Cryst Growth, 71,66(1985) © 1991 by CRC Press LLC

356 C0PPER:BERYLLIUM ETCHANTS CUBE-000 1 TIME: NAME: ETCH TEMP: TYPE: Acid, structure COMPOSITION: ... H,O, ml 100 20% 35 ml ... KOH ... H20 ml 125 DISCUSSION: specimens. Specimens used in a study of the effects of pressure on age Cu:Be:Ni alloy to and structure. hardening. Solution used develop defect V A - Acta Metall, 9,216(1961) Phillips, REF: - CUBE-0002 TIME: ETCH NAME: Nitric acid, dilute RT TYPE: Acid, cleaning TEMP: COMPOSITION: ml ... HNO, 100 ... 100 H,O ml DISCUSSION: thick, cut Cu:Be, used as spring clips to hold spring shim stock, 0.010.015" and SST plates during metallization. After cutting and shaping, clips semiconductor wafers on MeOH, and N, blown dry. Solution shown in were in hot TCE vapors, rinsed degreased DI rinse; MeOH (3) (2) rinse; water lightly etch clean (1) etch; before use: clips used to a com- (4) N, blow dry. Same method used to clean clips after metal depositing with and scrap/removal of loose metallization build-up, and etch cleaning. physical bination of REF: Fahr, Walker, P - personal application, 1980 F & ETCHANTS C0PPER:CERIUM 1 CUCE-000 ETCH NAME: Femc chloride TIME: Acid, removal TEMP: TYPE: COMPOSITION: x . 25% FeCI, ... DISCUSSION: CeCu,, as a single crystal ingot by the Czochralski (CZ) method. Material is grown LaCu, orthorhombic structure and was used in a material growth study. Also developed in CZ grown ingots, and CeAI, by arc melting and aging at temperature. CeB, and CeCu,Si, chloride solutions are are No etchant shown. (Note: Ferric single crystals. also grown as etchants for copper and copper alloys or compounds.) general REF: Onuki, Y et al - J Phys Soc Jpn, 4,1210(1984) C0PPER:GALLIUM ETCHANTS CUGA-000 1 a TIME: NAME: ETCH TEMP: Acid, preferential TYPE: COMPOSITION: . . FeCI, x .. EOH ... x © 1991 by CRC Press LLC

357 CRC of Metal Etchunts Handbook 344 DISCUSSION: Cu:Ga used in a study of transformation due to strain. Specimens were alloy specimens icelbrine solution, or at elevated quenched directly into an subjected to strain temperatures, solution. Solution shown used to develop defects and structure. Also studied NaOH a 10% and Cu:Zn alloys. Cu:Ga:Ge Metall, - Acta 6,243(1958) B T REF: Massaski, b CUGA-0001 ETCH NAME: Ammonium hydroxide TIME: Base, TYPE: TEMP: preferential COMPOSITION: .. . NH40H . x ... x H,O DISCUSSION: specimens. Solution used Cu:Ga develop defects and structure. See CUGA- alloy to a for additional discussion. 0001 REF: Ibid. C0PPER:GERMANIUM ETCHANTS 1 CUGE-000 NAME: Phosphoric acid TIME: ETCH Electrolytic, polish TYPE: TEMP: COMPOSITION: ANODE: .. . H,PQ CATHODE; x POWER: DISCUSSION: Cu:Ge of varying compositions grown and used in a study of optical absorption alloys alloys above K. was erratic for germanium concentration Solution 7% Ge, as the at 4.2 not polish. Other alloys were studied. material will Rayne, A REF: - Phys Rev, 121,456(1961) J ETCHANTS C0PPER:GOLD CUAU-0001 NAME: TIME: ETCH TYPE: polish TEMP: Electrolytic, COMPOSITION: ANODE: CATHODE: ... HAc x POWER: CrO, x ... DISCUSSION: Cu,Au specimens used in a study of long range order from strain hardening. single crystal Solution to polish specimens prior to straining. used REF: Davis, R G & Steloff, N S - Phil Mag, 12,297(1965) CUAU-0002 TIME: Phosphoric acid NAME: ETCH TEMP: TYPE: Electrolytic, polish ANODE: COMPOSITION: CATHODE: . . . . H,PQ x POWER: © 1991 by CRC Press LLC

358 DISCUSSION: Cu,Au used in a study of ordering strength and dislocations in single crystal specimens to specimens. The material superlattice materials. Solution polish used Ni,Mn also was studied. J & Miller, D S - Phil Mag, 6,87 l(1961) REF: Markoikowski, M C0PPER:LANTHANUM ETCHANTS CULA-0001 NAME: TIME: ETCH Ferric chloride TYPE: Acid, removal TEMP: COMPOSITION: .. . 25% FeCI, . x DISCUSSION: grown as single crystal ingots by the Czochralski (CZ) method. See discussion LaCu, Copper:Cerium (CECU-0001) for further discussion. under Onuki, REF: - J Phys et Jpn, 4,1210(1984) al Y Soc C0PPER:NICKEL ETCHANTS 1 CUNI-000 ETCH NAME: Nitric acid TIME: TYPE: Acid, preferential TEMP: COMPOSITION: . .. . HNO, x DISCUSSION: single crystal specimens fabricated as spheres. Solution will develop pole figures CuNi (100), crystal and (1 11) plane locations, and is not actually preferential as a finite (1 lo), at form etchant. Schmunk, R E & Acta Metall, 8,396(1960) Smith, C S - REF: ETCHANTS PALLADIUM COPPER CUPD-0001 ETCH NAME: acid Nitric TIME: TYPE: Acid, removal hot RT TEMP: to COMPOSITION: . . . . HNO, 1 ... H,O 1 DISCUSSION: thin films co-evaporated on Pyrex blanks in a material study. Quartz was evaluated Cu:Pd SiPd. Solution used to etch remove or etch pattern but it will form as a substrate material, thin film after annealing cycles. van REF: Langeveld, A D Thin Solid - 109,179(1983) Films, C0PPER:ZINC ETCHANTS CUZN-0001 ETCH NAME: TIME: TEMP: TYPE: preferential Acid, COMPOSITION: .. . FeCI, x . EOH ... x © 1991 by CRC Press LLC

359 CRC Handbook Metal Etchants of 346 DISCUSSION: Cu:Zn a study of transformations due to strain. Solution used alloy specimens used in CUGA-0001a for additional discussion. defects and to develop structure. See Acta Metall, 6,243(1958) - Massaski, T B REF: OF COPPER BROMIDE, CuBr, PHYSICAL PROPERTIES Bromide Classification 29 35 & numbers Atomic 223.4 Atomic weight 498 ("C) Melting point ("C) point Boiling 3.0 X (glcm3) Density 2-3 scratch) - Hardness (Mohs (100) a-pinacoid Crystal structure (monoclinic-normal) Black Color (solid) (basal) Cleavage (001) COPPER CuBr, BROMIDE, Does not occur as a natural compound due to high solubility in water, but can General: other in and be extracted from ocean waters and some hot springs like occur solution bromides, chlorides and some iodides. There is no major industrial use. Technical Application: Copper bromide has been studied in association with some 40 other compounds semiconductor characteristics and, even though water soluble, may for useful optical characteristics other bromides. have like some Etching: Water and alcohols. ETCHANTS BROMIDE COPPER CUBR-0001 TIME: alcohol ETCH NAME: Ethyl RT TEMP: TYPE: Alcohol, removal COMPOSITION: . . . . EOH (MeOH) x DISCUSSION: used in an evaluation of cohesive energy features CuBr single crystals tetrahedral of etchant semiconductor materials. Solution shown was used as a general polish and removal on surfaces. Some 40 materials were studied. a1 - J Phys Chem Solids 45,361(1984) et A REF: Aresti, OF COPPER CHLORIDE, CuCI, PROPERTIES PHYSICAL Chloride Classification 29 & 17 Atomic numbers 134.48 weight Atomic 498 point Melting ("C) 993 point ("C) Boiling 3.045 Density (g/cm3) 2-3 Hardness (Mohs scratch) - (100) cube Crystal structure (isometric normal) - Yellow Color (solid) Cleavage (cubic) (001) © 1991 by CRC Press LLC

360 COPPER CHLORIDE, CuCI, Does not in natural as a solid compound due to water solubility, but can General: occur in from ground waters in solution, particularly and areas associated with extracted be ocean May occur as a mixed component in arid areas with potassium chloride, copper mining. sulfates. There is no major use in industry, other than as a copper source carbonates, and plating in a component electrolytic copper etch solutions. in or as In Application: it has been used as a copper doping Technical Solid State processing in some compound semiconductors and, as in the general metal source industries, for elec- trolytic copper plating. The chloride also has used as a constituent in some preferential been and for copper plate-out solution with subsequent heat treatment drive-in for etchants, from copper. It has along studied with with other halides for semiconducting defect decoration been can have applications as an optical filter. properties, and and alcohols. Etching: Water CHLORIDE COPPER ETCHANTS CUCL-0001 ETCH Ethyl alcohol TIME: NAME: TYPE: Alcohol, removal TEMP: RT COMPOSITION: . . . . x (MeOH) EOH DISCUSSION: as single crystals were used in an CuCl of cohesive energy features of evaluation tetrahedral semiconductors. Alcohols were used for general removal and polishing of sur- faces. Forty were studied. materials Aresti, A REF: et Phys Chem Solids, 45,361(1984) al - J IODIDE, CUI COPPER PHYSICAL PROPERTIES OF Iodide Classification 29 & 53 Atomic numbers 190.4 Atomic weight 605 point Melting ("C) 1200 ("C) point Boiling 5.62 Density (g/cm3) 2.346 Refractive index (n = ) 2.5 (Mohs Hardness - scratch) Crystal structure (isometric - tetrahedron tetrahedral) 11) (1 Brown (solid) Color Cleavage (dodecahedral) (1 10) COPPER IODIDE, CuI General: Occurs in as the mineral marshite, CuI, as a minor compound associated nature due copper is little use of the natural mineral with the metal industry deposits. There to in scarcity, but the artificial compound has both chemical and medical applications. Technical Application: There is no use in Solid State device fabrication, to date, other than use as a constituent in etching solutions. The compound has been charac- occasional terized for semiconducting properties, and has possible application in optics as a filter element. Etching: K1, KCN, and NH,OH © 1991 by CRC Press LLC

361 Handbook Metal Etchants CRC of 348 ETCHANTS COPPER IODIDE CUI-0001 TIME: ETCH NAME: Potassium iodide RT TEMP: TYPE: Halogen, removal COMPOSITION: ... KI x . . . H20 (EOH) . x DISCUSSION: CuI in an evaluation of cohesive energy features of tetrahedral grown as single crystals etch. shown general removal and surface polishing as a Forty semiconductors. Solution used were evaluated. materials 45,361(1984) A et a1 - J Phys Chem Solids Aresti, REF: COPPER OXIDE, Cu,O PHYSICAL PROPERTIES OF Oxide Classification 29 8 & numbers Atomic 143.14 weight Atomic 1235 ("C) point Melting 1800 ("C) point Boiling 5.85-6.15 Density (g/cm3) 2.849 ) = (n Refractive index 3.5-4 scratch) Hardness (Mohs - octahedron (1 1 1) Crystal structure (isometric plagiohedral) - Black (CuO) Color (solid) (Cu20) Copper-red (solid) Emerald green (flame) interrupted) - Cleavage (cubic (001) Cu,O OXIDE, COPPER the natural mineral cuprite, Cu,O (red General: ore), it is a primary ore of As copper incrustations black The latter, as CuO. tenorite, also occurs as and copper, the monoxide: cuprite is brilliant conchineal-red. Both colors appear on pure copper parts with whereas air, but the green "verdigris" is copper sulfate from sulfur in the atmosphere. exposure to industrial ores Other than copper, both forms are important as coloring agents in paints of and glass, and the mineral is used for its flame color in pyrotechnics. Technical Application: Though not used Solid State material processing, both in general polycrystalline to fabricated discrete rectifiers, similar single crystal forms are used the and to selenium rectifiers. Cu,O grown by oxidation of OFHC copper surfaces and, has been on alpha-brass, by copper plating and water soak-tarnishing as a copper hydrated thin film. Both methods in material studies. Most of the listed references here are for removal used of "native oxide" films in copper material processing. Etching: HCl (CuO). HNO,, NH,OH, and acid mixtures (Cu,O). © 1991 by CRC Press LLC

362 COPPER OXIDE ETCHANTS cuo-000 1 Ethylenediamine TIME: ETCH NAME: TYPE: Acid, oxide removal TEMP: COMPOSITION: x % . ethylenediamine 1 . . . DISCUSSION: thin film on Cu20, acid will remove the oxide as a native oxide surfaces. This amino not etch the pure copper metal. but will Stiegler, REF: & Noggles, T S - J Appl Phys, 3 1,1827(1960) J 0 CUO-0002 Nitric acid, dilute TIME: ETCH NAME: removal Acid, TYPE: TEMP: COMPOSITION: x ... HNO, x ... H,O DISCUSSION: Cu,O as a oxide on copper surfaces. Dilute solutions are used to remove native native control oxidized and copper surfaces. Cleaned specimens were polish at 1030 oxides etch 1095°C for to h and then annealed for 40 to 150 h. Large area single crystals (10 to 3-4 mils) were size with 40 increasing as annealing time was increased. formed Toth, REF: S et a1 - JAppl Phys, 31,1117(1960) R B-1 ID, The American Brass Co. CUO-0003: Bulletin Cu, Cu alloys. Used a and 1:l mixture for removal of native oxide and to etch polish copper surfaces. CUO-0004: & Campos, R - personal application, 1961-1962 Walker, P alloys as Used a Cu cryogenic trailer piping. for of surface solution removal 1:20 by soaking and contamination. Solution with an SST applied scrubbing Heavy DI brush. wash after etch cleaning and wipe dry with water toweling. lint-free CUO-0005 TIME: NAME: dip ETCH Copper Brite polish TEMP: TYPE: Acid, COMPOSITION: .. .. H2S0, 3-7 ... 1-7 HN03 ... . 0-5 HCI 1-10 ... H20 DISCUSSION: Cu, and Cu alloys. There are several specific mixtures of this "Brite Dip" which is oil/grease contamination sometimes a "scale" removal etch. Used to remove referred as to oxide, etches as surface polish or copper for copper. Solutions are extremely reactive, and a bright copper surface. They should not be used on parts requiring close di- producing mensional control as etching proceeds by the surface contam- pinholing and undercutting of such ination, surface planarity and tolerances cannot that be maintained. See CU-0028 for other specific mixtures. REF: Walker, P & Fahr, F - personal application, 1978-1983 © 1991 by CRC Press LLC

363 350 CRC of Metal Etchants Handbook CUO-0006a ETCH NAME: Ammonium hydroxide TIME: TYPE: Hydroxide, oxide removal TEMP: RT hot to COMPOSITION: x . . . NH40H . DISCUSSION: oxide. Solution will remove both Cu20 and CuO oxides and slowly etch Cu,O, native copper. REF: Hodgman, C al - Handbook of Chemistry and Physics, Chemical Rubber Co., et D 1943, 380 OH, Cleveland, CUO-0007: Walker, P - personal application, 1980-1985 used in test assemblies of microelectronic devices. Surfaces were OFHC copper parts cleaned by then wash in DI water, and final rinse with soaking parts in solution shown, and N, dry. MeOH, blow N J Appl Phys 32,900(1961) F - CUO-0017: Horn, with iron and grown by the Czochralski (CZ) method in a single crystals doped CuO of femtes. Other study grown ferrites studied were Fe,O,, and iron doped ZnO, Ga203, and MnO. and CUO-0008 NAME: Phosphoric acid TIME: ETCH TYPE: Acid, TEMP: 130°C polish pmtmin COMPOSITION: RATE: 1 x . . .. H3P04 DISCUSSION: Cu20, as rectifiers in a study of etching effects on device operating para- material use Etching will will increase current. meters. reduce the forward current while a lapped surface Tekh & B 27,2786(1957) - Zh Usachev, Fir, P Makovskii, F A REF: CUO-0009 NAME: TIME: 1-2 min ETCH TYPE: Acid, removal 60-70°C TEMP: COMPOSITION: 33 ml . . .. H,P04 ml . . . 33 HNO, . 33 ml .. . . HAc DISCUSSION: Cu,O, as a native oxide on copper specimens. Solution will etch both copper oxide and copper, but is removal of oxides. particularly good for REF: de Jong, J J - 9,2(1954) (in Dutch) Metalen, Tegart, W J McG - CUO-0015: and Chemical Etching of Metals, Pergamon The Electrolytic Press, England, 1956 Cu,O, native oxide on copper surfaces. Solution can be used to etch both copper and copper oxides good for oxide removal. and is very cuo-0010 ETCH NAME: Ammonium sulfate 15 TIME: rnin TYPE: Acid, cleaning TEMP: RT COMPOSITION: 2-5%(NH,),S04 . . . . x © 1991 by CRC Press LLC

364 DISCUSSION: Cu,O thin films grown on OFHC copper by oxidation. Clean copper with solution as before oxidation. etching, wash in DI water. shown After REF: Baur, - Acta Metall, 103,273(1956) P et J a1 cuo-0011 TIME: 10 min Oxygen ETCH NAME: preferential TEMP: TYPE: Gas, 250°C mmHg PRESSURE: COMPOSITION: 10 0, ... x DISCUSSION: Used in a study Cu, single crystal oxidation rates as related to crystallographic sphere. of plane zones. faces and J al - Chem Phys, 8,431(1940) REF: Gwathmey, et A T Gwathmey, A T al - J Phys Chem, 46,969(1942) CUO-0012: et Oxidation rate varies single crystal spheres and oriented flats. cut with crys- Cu, with (100)<(210)<(111)<(110)<(311). the following decreasing order: tallographic faces in Thickness variation can as much as fivefold. Rate varies with orientation, temperature, be oxygen pressure. and CUO-0013 ETCH NAME: TIME: Variable Oxygen TYPE: preferential TEMP: Variable Gas, COMPOSITION: x ... 0, DISCUSSION: A comprehensive article of oxidation of materials - thick- spheres. Cu, single crystal orientation, rates. Other Ni, Fe, Nb, Co, materials were ness, epitaxy Ge, Ag, Mg, Cr, Al, Cd, Be, Pb, Sb, Ta, Mn, Fe-Ni, brass, and U. Included cleaved or cut wafer Pd, Zn, of some of the materials. surfaces Gwathmey, REF: A & Lawless, K R - Gatos, T Ed - The Surface Chemistry of H C Metals and Semiconductors, John Wiley & Sons, New York, 1960, 483 CUO-00 14a TIME: ETCH NAME: removal TEMP: RT TYPE: Acid, COMPOSITION: . .. . H,SO, ml 300 400 . . . . HNO, ml 5 ... HCI ml .. .. H,O 295 ml DISCUSSION: Cu specimens. Described as a copper oxide removal etch. (Note: See Copper CU-0028, Dip solutions. This Brite of the is a variation CU-0032 solution.) REF: Kohl, W H -Handbook of Materials and Techniques for Vacuum Devices, Reinhold, New York, 1967 © 1991 by CRC Press LLC

365 352 CRC of Metal Etchants Handbook 14b CUO-00 2-3 TIME: sec NAME: ETCH TEMP: RT TYPE: Acid, removal COMPOSITION: . . . . HNO, 1000 ml HCl ... ml 10 DISCUSSION: Cu etch. a copper oxide removal specimens. Described as Ibid. REF: CUO-0006b Ammonium chloride TIME: ETCH NAME: removal TYPE: RT Salt, TEMP: COMPOSITION: . . . x% NH4Cl . x DISCUSSION: specimens, or as a native oxide Cu,O copper. Described as a copper oxide removal on etchant. Ibid. REF: CUO-00 16 TIME: 15 h Water NAME: ETCH TEMP: RT TYPE: Acid, oxidation COMPOSITION: ... H20 x DISCUSSION: thin films plated from solution onto alpha-brass, Cu,O with 29.38% Cu. Plating Cu:Zn pH containing M CuSO,: 1.57 (NH4),S04 for and 7 balanced with NH,OH, was: 0.04 solution tracer ,06Tu. After plating, 12 mm blanks were soaked in water for 15 h to oxide tarnish, of sealed in polyethylene bags for radiation count. A study and the then DI washed, water fo mechanisms Cu20 formation. REF: Birley, S & Tromans, D - J Electrochem Soc, 1 18,636(197 1) S OF PHOSPHIDE, Cu,P PHYSICAL PROPERTIES COPPER Phosphide Classification 29 & 15 Atomic numbers 221.73 weight Atomic 1200 - ("C) point Melting Boiling point ("C) 6.4-6.8 Density (g/cm3) 6-7 Hardness (Mohs scratch) - (100) cube Crystal structure (isometric normal) - Greytblack (solid) Color Cleavage (cubic) (001) COPPER PHOSPHIDE, Cu,P General: Does not occur in nature as a pure metallic phosphide, although the mineral and tsumebite, Pb,Cu(PO,), are minor phosphate minerals. Ar- Cu,(OH)PO,, libethenite, tificial copper phosphide is fabricated in industry as phosphor-bronze, and used for its spring qualities. © 1991 by CRC Press LLC

366 Technical Application: As the material is widely used in Solid State phosphor-bronze holding parts during vacuum metal- or processing as spring clips for semiconductor wafers lization, and as general holding clips during device testing. has been grown as a single crystal with germanium doping for evaluation The material semiconductor. as a compound (HF:HNO,). Soluble in HNO, and mixed acids Etching: ETCHANTS COPPER GERMANIUM PHOSPHIDE CUGP-000 1 TIME: NAME: ETCH RT TEMP: Acid, removal TYPE: COMPOSITION: ... HF x x . HNO, . . . ... H20 x DISCUSSION: single crystal ingots grown by the Horizontal Bridgman (HB) method as a p- CuGe2P3 parallelapipeds (001), (1 10)/(110), and me- type semiconductor. Specimens were cut as (Note: polished a material properties evaluation. chanically Solution shown can be used in to etch clean phosphor-bronze.) 985) (1 J E - J Phys Chem Solids, 8,95 1 McDonald, REF: OF SELENIDE, Cu,Se COPPER PHYSICAL PROPERTIES Selenide Classification Atomic numbers & 34 29 Atomic weight 206.10 1200 > Melting point ("C) ("C) Boiling point 6.7 (g/cm3) Density 1 scratch) - 3-4 Hardness (Mohs (100) cube normal) - Crystal structure (isometric Silver-white Color (solid) Cleavage (cubic) (001) SELENIDE, COPPER Cu,Se in nature as General: Occurs berzelianite, Cu2Se and klockmannite, CuSe. the mineral The variety umangite, CuSe.Cu,Se is dark cheny-red in color, and there are other trinary or quaternary constituent copper selenides, such as and silver. crookesite, containing thallium as main use of The minerals is industrial minor ores of copper and selenium. these Technical Application: Trinary copper selenides are under evaluation as tetrahedral The compound in Solid State, but not used as devices at the present time. semiconductors are trinary compounds. following two copper selenides Etching: Soluble in mixed acids. © 1991 by CRC Press LLC

367 354 CRC of Metal Etchants Handbook SELENIDE COPPER GALLIUM ETCHANTS CGSE-000 1 TIME: ETCH NAME: Aqua regia, variety RT TEMP: polish TYPE: Acid, COMPOSITION: 1 HCI ... 1 ... HNO, DISCUSSION: crystal evaluated for cohesive energy features of tetrahedral semicon- CuGaSe, single Forty studied. (Note: See copper indium materials were addition so- ductors. selenide for lutions.) Solids, Chem a1 - J Phys 45,361(1984) et REF: Aresti, A INDIUM SELENIDE COPPER ETCHANTS CISE-0001 NAME: 2 min TIME: ETCH polishlstain TEMP: RT Acid, TYPE: COMPOSITION: 1 ... HCI . . . . 1 HN03 DISCUSSION: single crystal Crystalline ingot grown by Horizontal Bridgman (HB) CuInSe, specimens. then large single process, grains were cut out and mechanically lapped with 0.3 crystal pm alumina. After indium diffusion, the solution shown was used to acid stain the p-n junction after angle lapping. Shih, T et REF: J Phys, 66,420(1984) a1 Appl - CISE-0002b: Ibid. Annealed under Se vapor to produce a p-type layer as a CuInSe, singe crystal wafers. used as a junction p-n junction. Solution stain. CISE-0005: Ciszek, T F J Muter, 14,451(1985) - Electron ingots grown by CuInSe, or the Bridgmanlstockberger process with slow directional LEC solidification for large grains. Material is p- or n-type depending on the charge. Preferred crystal growth habit is (1 12) tetragonal. -- -- - CISE-0002a ETCH NAME: Nitric acid TIME: Acid, TYPE: TEMP: junction COMPOSITION: x . . . . HNO, DISCUSSION: CuInSe, wafers annealed under Se to produce a p-type layer as a p-n junction. Solution used a junction stain. as REF: Tell, B et a1 - J Appl Phys, 48,2477(1977) © 1991 by CRC Press LLC

368 CISE-0003 ETCH TIME: NAME: Aciahalogen, cleaning TEMP: TYPE: COMPOSITION: (2) x ... 1% Br, 6 ... (1) H,SO, x . . . . MeOH H,O, 1 ... H,O ... 1 DISCUSSION: wafers. CuInSe, a melt by directional freezing with a preferred (1 12) p-type Grown from were and polished sequentially in these two cleaned tetragonal orientation. Specimens acid to remove carbon and oxygen contamination. solutions Phys, Appl J 66,320(1984) - J H von REF: Bardeleben, von H - J Appl Phys, 66,586(1984) J Bardeleben, CISE-0004: CuS SULFIDE, PHYSICAL PROPERTIES COPPER Classification Sulfide 29 & 16 Atomic numbers 159.29 Atomic weight 103 Melting ("C) point del. ("C) 220 Boiling point Density (g/cm3) 4.6 index (n Refractive = ) 1.45 (Na) Hardness (Mohs-scratch) 1.5-2 prism (1010) (hexagonal-normal) Crystal structure (solid) Color Indigo blue (basal) Cleavage (0001) COPPER SULFIDE, CuS General: Occurs mineral covellite, CuS in association with other copper vein ores. as the sublimate. secondary and, occasionally, as a volcanic origin Industrial use is as It is of in copper ore in association with the other vein ores. a minor Technical Application: direct use in Solid State processing, but has been artificially No artificial materials grown crystal. Both the natural and a single have been studied for as general morphological data. HN03, HCI, H,SO,, and KCN. Etching: Soluble in SULFIDE COPPER ETCHANTS cus-0001 Nitric NAME: ETCH acid TIME: TYPE: Acid, removal TEMP: RT COMPOSITION: 1 HNO, ... 10 ... H,O DISCUSSION: CuS specimens as the natural mineral covellite. Solution used as a slow removal etch copper of purplish tarnish on surfaces in a general study of the the minerals. REF: Walker, P - mineral study, 1953 © 1991 by CRC Press LLC

369 356 CRC Metal Etchants Handbook of ETCHANTS COPPER GALLIUM SULFIDE CUGS-0001 Hydrochloric acid NAME: ETCH TIME: TEMP: TYPE: Acid, cleaning COMPOSITION: x HCI ... DISCUSSION: in quartz ampoules with tin as a metal than 630°C CuGaS, single crystals grown at less HCI. Clean quartz ampoule with boiling HCI and rinse in solvent. Clean copper with EOH. platelets on the tin during compound grown and have a metallic luster. The SnS nucleate with crystal color. A Ga,SnS,-, crystals are transparent was transparent and CuGaS, red crystal was orange in color. CuGa,S, is cubic and CuGa,S, is sphalerite CuGaSn, colorless. A (Note: Reference to "cubic" is isometric structure isometric system, tetrahedral class. the class commonly call the cubic system, normal system.) K & Sugiyama, K - J 12,43(1983) Mater, Electron Tsubaki, REF: PHYSICAL PROPERTIES OF COPPER DISULFIDE, Cu,S Sulfide Classification 29 & 16 numbers Atomic 159.20 weight Atomic loo 1 point Melting ("C) Boiling point ("C) 5.5-5.8 Density (g/cm3) 2.5-3 Hardness (Mohs- scratch) (1 10) a-pinacoid normal) - Crystal structure (orthorhombic cube (100) normal) 1°C >9 - (isometric Lead grey Color (solid) - indistinct) Cleavage (pinacoidal (1 10) (octahedral - poor) 11) (1 SULFIDE, Cu,S COPPER in nature as the mineral chalcocite, Cu,S and is found as a vein deposit General: Occurs with ore along minerals. It is mined for both the copper and sulfur content. other copper CuSO, "Blue Vitrol" has important Other as copper ores in industry, the chemical than use in agriculture as an algicide, and additional use in chemical processing. Technical Application: Copper sulfide, Cu,S, with indium is a trinary compound doped and and device applications. semiconductor, under evaluation for general properties and have CuS been Cu,S, natural and artificial minerals, both The pure sulfides as studied for general morphology. The CuInS, material in the following section is in trinary the crystallographic tetragonal system, and under evaluation as a trinary compound semi- conductor. Etching: Soluble in single acids, and mixed acids. © 1991 by CRC Press LLC

370 COPPER INDIUM SULFIDE ETCHANTS CIS-0001a TIME: 3-4 min ETCH NAME: Nitric acid TEMP: TYPE: RT Acid, dislocation COMPOSITION: . HNO, . . x . DISCUSSION: Grown as small single crystals CuInS,, preferred (1 12) surface (1 12) wafers. with was used develop dislocations on the to orientation. Nitric acid sulfur surface, as 12)B (1 is a polar compound. A sulfur film material on the surface after etching. (Note: is left Remove with sulfur disulfide, sulfur CS,.) REF: - J Electrochem F A 129,1570(1982) Thiel, Soc, CIS-0001b sec 10-15 TIME: BRM ETCH NAME: Halogen, dislocation TEMP: RT TYPE: COMPOSITION: x 2% Br, ... x .. . MeOH . DISCUSSION: CuInS,, (1 12) wafers. Solution used to develop dislocations on the (1 12)A positive CuIn polar surface. Ibid. REF: CIS-0001~ TIME: min ETCH NAME: 45 TYPE: Acid, dislocation TEMP: RT COMPOSITION: . . H,SO, 3 . . 1 ... H,O, 1 H,O ... DISCUSSION: 12) wafers. used to develop dislocations on the (1 12)A positive CuIn CuInS, (1 Solution polar surface. REF: Ibid. CIS-0002 ETCH NAME: TIME: 10 sec TYPE: Acid, polish TEMP: RT COMPOSITION: 1 HCI ... . . . . HNO, 1 ... 1 H,O DISCUSSION: CuInS, wafer. Crystals are tetragonal system. Mechanically polish wafers with diamond grit, then etch polish with the mixture shown, and rinse in water. REF: Phys R T et al - J Barradas, & Chem Solids, 45,1185(1984) © 1991 by CRC Press LLC

371 CRC Handbook Metal Etchants of 358 CIS-0003 NAME: Aqua regia ETCH TIME: TYPE: Acid, polish TEMP: COMPOSITION: 1 HNO, . . . . 3 HCl ... DISCUSSION: grown by travelling heater CuInS, (THM) using starter powdered wafers. Ingots method indium flux in a sealed quartz material Cut wafers were mechanically with an ampoule. with polished 0.06 MeOH, Then degreased TCE, rinsed in alumina. then in pm acetone, etch polish with aqua regia. and Hsu, REF: J et - J Cryst Growth 70,427(1984) a1 CIS-0004a ETCH NAME: Nitric acid, dilute TIME: polish Acid, TYPE: TEMP: COMPOSITION: 1 . . . . HNO, 3 ... H,O DISCUSSION: CuInS,, n-type wafers. Etch polish in this solution. Russak, M REF: Creter, C J & Electrochem Soc, 132,1741(1985) - CIS-0004b ETCH TIME: NAME: TYPE: Acid, photo-etch polish TEMP: COMPOSITION: x ... HCl . .. . x HNO, x ... H20 DISCUSSION: CuInS, n-type wafers. Solution used with intense white light to photo-etch polish sur- faces. REF: Ibid. & - Appl Phys Lett 37,428(1980) Hodges, P CIS-0005: Tenne, R P solution as etch. Used a polishing CuInS, wafers. et a1 - CIS-0006: Phys & Chem Solids 8,887(1985) Takeuchi, S J (1 1 1) oriented single crystal ingots grown by a Growth Material Freeze method. CuIn,S,, n-type, growth was (1 11) preferential. Wafers were cut and mechanically lapped and was study a semiconducting properties. of in and polished Cu,PS,:YCVBr COPPER PHOSPHO-SULFIDE, Does not occur General: a natural compound, although there are several copper sulfide as minerals containing iron, bismuth, arsenic, and antimony, but not phosphorus. The structure sulfo-gennanate, argyodite, 4Ag2S.GeS2 - isometric with has been to as the silver referred octahedral, 180Yotation (1 11) Spinel Law twinning, e.g., habit, on o(ll1) as bi-crystal and or multiple twin lamellae. Sphalerite, ZnS, shows similar twinning lamellae, but is isometric system, class, not normal (cubic) class. tetrahedral There is no industrial use of the compound to date, although copper sulfide minerals are important ores for both elements. There are many copper phosphate compounds in chemistry. © 1991 by CRC Press LLC

372 Technical Application: The has been grown by Vapor Transport (VT) from compound (VLS) materials with CI,, Br,, and I,. As undoped Cu3PS4, vapor/liquid/solid halogen doping: iodine, Cu,PS,:I, red crystals. crystals are transparent yellow; doped with were transparent and has been studied for general morphology. the material Electrically is a conductor, HNO, and Etching: soluble in NH40H. PHOSPHO-SULFIDE ETCHANTS COPPER CPS-000 1 ETCH NAME: Nitric acid TIME: TEMP: TYPE: Acid, removal COMPOSITION: x . . . . HNO, DISCUSSION: single crystal platelets grown by Vapor Transport (VT) with a CuI liquid Cu,PS,:I, flux. Crystals are transparent, in color, forming in the isometric system, normal (cubic) class, red high 43m space group. Nitric acid was used as a general etching solution. as temperature REF: Tributsch, H Betz, G - J Electrochem Soc, 131,640(1984) & CPS-0002 ETCH Ammonium hydroxide TIME: NAME: Base, removal TEMP: TYPE: COMPOSITION: x . . NH40H . . DISCUSSION: Crystal grown Cu,PS,:halogens. Br,, I,. Halogens: by Vapor Transport (VT) be- CI,, tween 870-900°C and above 970°C. A vapor/liquid/solid (VLS) flux was used: PSCI, (liquid); (black powder). was grown as yellow, transparent crystals. Materials C0,S Cu3PS, was to the natural mineral argyodite, conductors, and structure referred were 4Ag2S.GeS,. used as a removal Solution shown can With the flux shown, crystals of Cu,PS,:Cl be etchant. were grown. also 61,275(1983) Growth, al - J Cryst et Fiechter, S REF: COPPER TELLURIDE, Cu,Te, PHYSICAL PROPERTIES OF Classification Telluride Atomic numbers 29 & 43 Atomic weight 551.28 Melting point ("C) loo0 point ("C) Boiling 7.4 Density (g/cm3) - scratch) Hardness (Mohs 3.5 Crystal structure (isometric - tetrahedral) (1 12) tetrahedron Color (solid) Purplelblack Cleavage (tetrahedral) (1 12) TELLURIDE, Cu,Te, COPPER General: Occurs as the natural mineral rickardite, Cu4Te3, and weissite, Cu,Te3. Both minerals occur in massive form associated with pyrite and tellurium ores in minor quantity. tellurium and copper. There is no industrial other than as minor ores of use Technical Application: Copper telluride doped with either gallium or indium has been © 1991 by CRC Press LLC

373 360 CRC of Metal Etchants Handbook as evaluated a possible compound semiconductor of the I-VII type. Grown as a single crystal trinary compounds show a distinctive (1 12) growth habit. these of Variations Etching: aqua regia. ETCHANTS COPPER TELLURIDE CUTE-0001 Aqua regia, variety TIME: ETCH NAME: removal Acid, TYPE: TEMP: RT COMPOSITION: HCl 1 ... HNO, 1 ... DISCUSSION: natural mineral specimens as the used as a surface cleaning Cu,Te, rickardite. Solution light removal etchant in a material study. and Walker, P REF: mineralogy study, - 1953 TELLURIDE COPPER GALLIUM ETCHANTS CGTE-0001 TIME: ETCH NAME: Aqua regia, variety TEMP: TYPE: Acid, removal COMPOSITION: x ... HCl x . . . . HNO, DISCUSSION: CuGaTe,, used in an evaluation of cohesive energy features of tetrahedral single crystals semiconductors. were studied. Forty materials Solids, & J Phys 45,361(1984) Chem - REF: Aresti, A et al COPPER INDIUM TELLURIDE, CuInTe, General: Does not occur as a natural metallic compound, though there are other binary and trinary telluride is no application of the compound in the metal industries. minerals. There Application: indium telluride has been grown as a ternary compound Technical Copper and is under development and study for its semiconducting characteristics. semiconductor, Soluble acids mixed Etching: of in with without water. HCl:HNO, or INDIUM TELLURIDE COPPER ETCHANTS CUIT-000 1 a TIME: ETCH NAME: Hydrofluoric acid, dilute TEMP: TYPE: Acid, float-off COMPOSITION: HF ... 1 1 ... H,O DISCUSSION: thin films. The thin films were deposited on glass substrates by CVD. Films CuInTe,, - the float-off technique for by undercut etching of the glass were removed from the glass electron microscope (TEM). removal substrates and study under a transmission films from of - 3 Vac Sci Technol, 14,769(1977) REF: Kazmnerski, L L © 1991 by CRC Press LLC

374 CUIT-0001 b TIME: Aqua ETCH regia, NAME: variety TEMP: RT TYPE: Acid, thinning 1000 kmin COMPOSITION: RATE: 1 ... HCI . HNO, . . 1 . 2 ... H,O DISCUSSION: films. Thin films were deposited on CuInTe,, by CVD. Before removal from thin glass (CUIT-0001a) were etch thinned in the solution shown. After float-off glass, the films studied an using were electron microscope (EM). specimens morphologically Ibid. REF: CUIT-0002 ETCH NAME: Aqua regia, variety TIME: Acid, removal TEMP: TYPE: COMPOSITION: x ... HCI . HNO, .. . x DISCUSSION: crystals used in an evaluation of CuInTe,, of tetrahedral single cohesive energy features were studied. semiconductors. Forty materials REF: Aresti, A et - J Phys & Chem Solids, 45,361(1984) al OF AI,O, PHYSICAL PROPERTIES CORUNDUM, Oxide Classification & 8 13 numbers Atomic 101.94 Atomic weight 2050 ("C) Melting point 2250 Boiling point ("C) 3.95-4.10 Density (g/cm3) 1.75-1.76 (n = Refractive index ) 9 - scratch) Hardness (Mohs (10il) rhomb rhombohedra]) - structure (hexagonal Crystal Greylblack (solid) Color (basal) Cleavage 1 (0oO AI,O, CORUNDUM, The natural mineral is widely distributed and associated with chlorate type General: in well limestone and rocks, as two latter in massive amounts, such as as the dolomite. The AI,O,.Fe,O,, it is a major abrasive. Clear, color chalk cliffs of Dover, England. As emery, tinted varieties are gem stones: ruby (red); sapphire (blue), etc. It is still used as a lapping and polishing Aluminum Oxide, abrasive. See for discussion. AI,O,, additional The Technical Application: little application in Solid State processing natural mineral has other than as a polishing abrasive, but the artificially pressed powder or single crystal (sapphire) blanks have major as circuit substrates, and other high temperature ceramic use applications. Also there are amorphous ruby parts artificially fabricated. See Aluminum Oxide for an expanded discussion. © 1991 by CRC Press LLC

375 362 CRC of Metal Etchants Handbook has been for many years, and was first grown as an artificial Natural corundum studied for artificial rubies Verneiul process and sapphires. by late 1800s the in crystal single the mixed acids, and molten fluxes. Etching: Single acids, ETCHANTS CORUNDUM 1 COR-000 Metal NAME: TIME: ETCH removal TEMP: TYPE: Metal, COMPOSITION: x ... Si DISCUSSION: (0001) natural A1203, Metallic silicon vacuum evaporated on corundum corundum discs. will the material. etch Reynolds, REF: & Elliot, A B M - Phil Mag, H F 13,1073(1966) COR-0002 ETCH NAME: Potassium bisulfate TIME: flux, removal TYPE: Molten 590°C TEMP: COMPOSITION: x . .. . pellets K2S0,, DISCUSSION: as natural corundum. Al,03, will dissolve in potassium bisulfate when used as Material a molten flux. Has been used in the metallographic study of single crystal compounds. REF: Dana, E Sons, & E -A Textbook of Mineralogy, 4th ed, John Wiley & W S Ford, York, 1950, 482 New COR-0003 ETCH NAME: Hydrochloric acid TIME: Acid cleaning TYPE: Hot TEMP: COMPOSITION: x ... conc. HCI, DISCUSSION: natural single crystals cut and polished Al,O,, on the z-axis (0001) basal en cabachon plane as star sapphires. Wash in HCl after polishing, then in H20 for general cleaning. REF: Walker, P mineralogy development, 1953 - PHYSICAL PROPERTIES OF CRONSTEDITE, 4Fe0.2Fe,0,.3Si02.4H20 Silicate Classification 14, 1, 26, 8 Atomic numbers 859 Atomic weight >loo0 Melting point ("C) ("C) Boiling point 3.34-3.45 Density (g/cm3) 1.80 = ) (n Refractive index 3.5 Hardness (Mohs - scratch) prism (hkO) Crystal structure (monoclinic - normal) BlacWbrownish Color (solid) perfect) - Cleavage (basal (001) © 1991 by CRC Press LLC

376 CRONSTEDITE, 4Fe0.2Fe20,.3Si02.4H,0 a minor natural mineral in association with other iron ores in England General: Occurs as ore No industry other than as a minor in of iron. Brazil. and use natural mineral has been studied in Solid State for general Technical Application: The thin section, transmitted light is brilliant emerald-green, and In and morphology defects. may and as light frequency lenses material filters. the have application H2S0,, HF. Etching: CRONSTEDITE ETCHANTS CRON-000 1 TIME: ETCH NAME: Hydrofluoric acid, dilute TEMP: RT TYPE: Acid, dislocation COMPOSITION: ... HF x ... H20 x DISCUSSION: cleaved wafers used in 4Fe0.2Fe,03.2Si02.4H20, material study. So- (001) a general used to develop dislocations on the cleaved surfaces. Authors say their specimens lution brittle, although natural material is shown to be elastic in thin section. They also were e.g., kaolinite, AI2O3.2Si0,.2H2O. to chronstedite a kaolin-type mineral, as referred Steadman, R & Pugh, J D - Phil Mag, 12,969(1965) REF: OF CRISTOBALITE, SiO, PHYSICAL PROPERTIES Oxide Classification 8 & 14 Atomic numbers -60 Atomic weight 1200 > ("C) Melting point point ("C) Boiling 2.27 (g/cm3) Density 1.486 (n = ) Refractive index 7 - Hardness (Mohs scratch) prism (1 10) Crystal structure (tetragonal - normal) alpha (1 1 1) octahedron (isometric - beta normal) White Color (solid) - poor) Cleavage (cubic (001) SiO, CRISTOBALITE, A naturally occurring high temperature form General: silica and considered as a of polymer of quartz. Occurs in small white octahedrons, often twinning according to the Spinel 275OC Law. The alpha to beta forms to have a transition temperature range between 195 initial formation temperature The alpha-cristobalite is tetragonal; whereas with >1200°C. beta-cristobalite is isometric. use of this form There is no industrial silica as a natural product due to scarcity. See of silicon dioxide, SiO, for major discussion. Technical Application: There is no use of cristobalite in Solid State processing, although have as a thin film, or its various mixtures and forms as glass (silica) SiO,, silicon dioxide, major applications. Artificially grown cristobalite has been observed as minute crystals in quartz epitaxy © 1991 by CRC Press LLC

377 - 364 Handbook of Metal Etchants CRC a by-product of and metallic compounds. Both natural and tubes as oxidizing other metals been have artificial crystals studied. Etching: HF, KF, NH,F CRISTOBALITE ETCHANTS CRIS-0001 Heat TIME: ETCH NAME: 195-275°C TEMP: TYPE: Thermal, conversion COMPOSITION: x .. . heat . DISCUSSION: as alpha-cristobalite carried through inversion point to beta-cristobalite on a hot- SiO,, using polarized light for observation. Authors say that transformation time stage microscope sec. less 0.1 was than Krisement, 0 & Tromel, G - Z Naturjorsch, 14a(7),685(1959) REF: CRIS-0002 ETCH Hydrofluoric acid TIME: Minutes NAME: Acid, TEMP: RT TYPE: preferential COMPOSITION: x (I) HF, conc. (2) x ... HF, vapor (hot) .. . . DISCUSSION: SiO,, as single crystal alpha-cristobalite and beta-cristobalite used in a general natural preferential compounds. Solutions used to polish and SiO, etch specimens of study natural a structure study. in Walker, P REF: mineralogy study, 1952-1953 - CRIS-0003 ETCH TIME: NAME: Thermal oxidation TEMP: TYPE: COMPOSITION: x ... air DISCUSSION: Si, (100) wafers cut from Czochralski (CZ) ingots used in a study of re-dissolution of precipitated oxide. Material at 1000°C for 256 days. Precipitated dislocation com- oxidized plexes (PDCs) as plate-like structures on (100) surfaces parallel to (1 10) directions. appeared Precipitates were cristobalite. (Note: Crystallites of cristobalite have been observed in quartz tubes furnace a by-product after silicon oxidation at elevated temperatures.) as - J Appl Phys Lett, 39,987(1981) REF: Shimura, F © 1991 by CRC Press LLC

378 PHYSICAL PROPERTIES DEUTERIUM, D OF (,H) Heavy hydrogen Classification isotope H, Atomic number 1.07825 Atomic weight (protium) 2.00147 (D,) *(deuterium) 2.01605 (tritium) - 252.7 (101.42)* ("C) Melting point (3.82)* 2254.3 - Boiling ("C) point (D,O)* 1.11 Density (g/cm3) 1-2 (Mohs Hardness - scratch) solid (100) cube normal) - structure (isometric Crystal Colorless gaslliquid Color White (solid) solid) - Cleavage (cubic (001) DEUTERIUM, D in nature in all substances containing hydrogen in a ratio General: Occurs about 5000: 1 of or D. The latter is called deuterium H, to heavy hydrogen, as (light) hydrogen normal - By repeated electrolysis of water, using a deuteron. as a transmutation particle and, light hydrogen off-gases and deuterium is concentrated about the nickel-iron electrodes, D,O, initially thought of "heavy water", sixfold in the residue. This was the original source essential the design to be of an atomic bomb. High concentrations of deuterium also can in obtained from metal processing areas where electrolytic cleaning tanks containing sodium be or potassium hydroxide have been years as collected in a sludge concentrate. in operation for Deuteron particles are used in cyclotrons and particle accelerators for bombardment D,O, has been producing protons, alpha particles medicine, heavy water, or In neutrons. as a tracer compound the study of water elimination by the human body. It was used in deuterium appeared in perspiration within hours of ingestion, but required about shown that 30 days for complete elimination in urine. is not used general processing and fabrication in Technical Application: Deuterium in State, though it has been Solid in chemical processing as a tracer element. Many metals used and metallic compounds are now being hydrogenated for special purpose applications as a-SiN:H a-Ge:H, a-Si:H. - the development of in or films thin hydrogen storage batteries light hydrogen. using normal of hydrogen shown under the Physical Properties Deuterium and the other isotopes have applications in atomic physics, radiation chemistry, and in section irradiation studies. TiD,, Several of their compounds are shown here in this section on deuterium, such as ErTi,:D,. and ScD,, Etching: See parent element for applicable chemicals. metal ETCHANTS DEUTERIDE TID-0001 ETCH TIME: NAME: TYPE: Acid, removal TEMP: COMPOSITION: x . . .. HNO, DISCUSSION: were as thin films. Molybdenum blanks TiD, used as substrates for metallization with © 1991 by CRC Press LLC

379 CRC of Metal Etchunts Handbook 366 materials were treated with heavy hydrogen, 3H, to titanium and scandium. The furnace ErTi, was form deuterides, also deuterided. Technol, et - J T Sci a1 19(1), 119(198 1) Vac Adachi, REF: SCD-000 1 TIME: ETCH NAME: TEMP: TYPE: Acid, removal COMPOSITION: x ... HF x ... HN03 DISCUSSION: as films. See TID-0001 for discussion. ScD, thin REF: Ibid. ~ DEU-000 1 NAME: Deutron ETCH Particle, TYPE: TEMP: transmutation COMPOSITION: x . . . . deutrons DISCUSSION: used cyclotrons to produce protons, alpha particles, and Deutron particles neutrons. in the study of transmutation of elements and materials. Used in Foster, REF: Van & - An Introduction to General Chemistry, 3rd ed, D Alyea, H N W Nostrand, York, 1947, 77 New 300 & 1 TRIT-000 ETCH NAME: TIME: TYPE: Acid, cleaning TEMP: RT COMPOSITION: 1 . . H,SO, . . HCI ... 1 ... H,O 1 DISCUSSION: used SST for handling tritium tubing in atomic reactors a heavy isotope of hydrogen. - bore of tubing etch cleaned in this type of solution to remove burrs and draw marks Internal highly polished for a spontaneous ignition of tritium during flow prevent internal surface to with water, then with heavily passage. After etching, rinse and use the heat of a MeOH, and dry tube lengths. See FE-0024 for general tube cleaning. heat torch flame to personal - communication, 1972 Mills, T REF: PHYSICAL PROPERTIES C DIAMOND, OF (carbon) Nonmetal Classification 6 (carbonlgraphite) Atomic number 12 (carbonlgraphite) weight Atomic 1900 (to carbon) Melting point ("C) 2000 (to air) in CO, - ("C) Boiling point 3.516-3.525 (g/cm3) Density (1.3-1.4) 2.4195 ) = Refractive index (n 5.68-5.70 constant (e = ) Dielectric (cm- Absorption constant © 1991 by CRC Press LLC

380 (type 0.12 xtls) I1 Wavelength (microns) - 0.405 (type 14.8 xtls) I1 - 0.226 (microns) 4.8 Absorption band (microns 0.4 - eV) 4.36 x 28-105°C 1V6) expansion ( Volume 45 (eV) Hole mobility 5+ (eV) Activation energy 800 cm- ') sec '/V Electron mobility (cm 9 Carrier lifetime (X sec) 7 (5.6) Energy (eV) gap 3.567 Lattice constant (angstroms) 10 scratch) - (Mohs Hardness 1 octahedron 1) (I Crystal structure (isometric - normal) Colorless ( + pastel hues) Color (solid) Cleavage (octahedral perfect) - (1 11) C DIAMOND, the as or graphite. General: Occurs as a native element high pressure form of carbon I), which is called the "diamond" o(l1 crystal structure Diamond is the atypical octahedron, Both of the elemental semiconductors, silicon and germanium, are called "diamond" form. The crystallographic structure. selenium are physically and elements sulfur, carbon, and metals, such as of chemically related to the transition class carbon, manganese, molybdenum, than CaF,, have (1 is cleavage, rather both cubic (100) as 1 1) fluorite, Diamond and etc. producing refractive index, - normal class. Because of its high isometric to common the is the most prized gem stone in birefringence, it world and is found as transparent high the colors, with the clear, blue-white being "top-water"; yellow most common; stones in various also green, orange, brown, but carbon content, and called and black (high and "bort"), diamonds have carbon flecks internally. Diamonds are found in "blue ground" pipes many Africa; one occurrence in the U.S.; in stream gravel in Brazil, Southeast Asia, India, and in syndicate controls diamond production and DeBeers mid-continental U.S. The the northern throughout the world. sales trigon system. At high using a high pressure Diamonds have been grown artificially temperature, in diamond will bum to oxygen, in vacuum 1900°C it will convert to CO,; at those diamonds that not meet gem-grade quality, are do graphite. "Industrial diamonds" primarily used as finely powdered lapping and polishing abrasives either and an oil are in in a solvent slurry, embedded in metal, rubber, or plastics, and as a "diamond" blade paste, for cutting. is the hardest known element or compound and is used in determining hardness It of minerals and materials in the Mohs hardness scale of 1-10, with diamond H other = 10. the Mohs-Wooddell scale: Diamond H = 42.5, which is the more accurate. Some Using 9+), borides the and approach diamond in hardness (H = artificial carbides of and the Knoop hardness scale (kfg/mm2) using the pressure of a shaped diamond stylus gives an even more accurate measure of hardness. Technical Application: Oriented single crystal diamonds are used mounting substrates as in semiconductor device both heat sinks and active elements as the assembly in assembly structure. abrasive in an oil paste is still a major lapping and polishing Diamond for all medium metals metallic compounds. As diamond grit impregnated metal or resinoid blades, saw and been in use for cutting rocks and minerals since the blades have 1800s, and are the primary method of as wafers, and the dicing of wafers as discrete devices, cutting Solid State ingots circuit well the as of ceramics as as or dielectric substrates. As diamond embedded cutting blocks and other shapes in rubber, metals, plastics, etc., used for general lapping, honing, polishing, similar applications. As a single crystal material it is fabricated for and optoelectric device applications, and is under study for various reactions, such as irradiation-produced © 1991 by CRC Press LLC

381 CRC of Metal Etchants Handbook 368 those observed NaCl; for its brilliant phosphorescence with applied color centers, similar to in vacuum; electrical discharge in a similar manner in ultraviolet light. and under reactions it is an n-type semiconductor, capable boron, operating as a diode above with Doped of 500°C like both BN. And carbon thin films are Sic deposited, then converted by and being to (DLC) structure with possible applications as both an annealing a diamond-like-carbon film or surface passivator. Such DLC structure also is referred to as electrically active thin i-C structure. In this book there are three sections: (1) Carbon, C-; (2) an Diamond, D-; and the basic types of this material. Graphite, GR-, as in acids alkalies. Soluble by dry chemical etching (DCE); and Etching: Insoluble and fluxes. molten in DIAMOND ETCHANTS 1 D-000 ETCH NAME: TIME: TYPE: Ionized gas, removal TEMP: GAS FLOW: COMPOSITION: ... XeC PRESSURE: x POWER: x . . . NO,, fumes . DISCUSSION: (111) wafers used to fabricate photoelectric devices. Degrease D, clean surfaces and with water and alcohol prior to photo resist patterning. Gases shown used to etch a grating structure in the diamond surface by ion beam assisted etching (IBAE), which is a form of reactive ion etching (RIE). Efemow, N N REF: et J a1 Technol, B3,416(1985) Vac - Sci - -- --- D-0002 TIME: xx h Hydrofluoric ETCH NAME: acid Acid, cleaning TEMP: Hot TYPE: COMPOSITION: x . . . . conc. HF, DISCUSSION: HF (1 11) wafers irradiation damage studies. in used to clean surfaces prior to D, used follow with irradiation, after etching. through washing in water REF: W et al Primak, Phys Rev, 103,1184(1956) - D-0003 ETCH NAME: Boron TIME: TYPE: Metal, TEMP: implantation COMPOSITION: x B ... DISCUSSION: (1 11) wafers cut 6"-off toward (1 10) D, in a study of diamond semiconducting used properties. Boron was ion implanted for a 5 X 1015 concentration at 200 KeV for maximum amorphous implantation (IZ) structure. REF: Maby, F W et al - J Appl Phys Lett, 39,157(198 1) D-0004 TIME: NAME: ETCH TEMP: TYPE: Electron, crystallization COMPOSITION: . laser x ... © 1991 by CRC Press LLC

382 DISCUSSION: D, thin film carbon deposits by laser annealing. The resulting crys- crystallized from is called diamond-like-carbon (DLC) structure and shown to be high tallization in hydrogen. edges. Compressive stress crystallite with greatest stress at cracking was observed Tensile crystallites. the of causes inward bulging - Thin REF: Films, 1 12,41(1984) Nir, D Solid D-0005 ETCH TIME: NAME: Tungsten Metal, preferential TYPE: 1500°C TEMP: 1 200- COMPOSITION: x ... W DISCUSSION: D, a study of plasticity. Tungsten metal used to etch diamond (1 11) platelets used in surfaces at elevated temperature. Evans, T REF: Wild, R K - Phil Mag, 12,479(1965) & D-0006 ETCH TIME: NAME: Oxygen (air) preferential Gas, TYPE: 1000°C, nominal TEMP: COMPOSITION: x . . O,, moist air . . DISCUSSION: D, (loo), 1 l), and (1 10) oriented wafers used in a defect development study. Heating (1 O,/H,O or O,/N, pure develop structure in but will not air moist in develop structure, will atmospheres. Below 1000°C trigon pits show a positive (+) orientation; above 1000°C a more hexagonal (-) pits tend to be 1000°C to rounded in shape orientation. Above negative 1000°C, but not on than all orientations below sharply triangular. Pits observed on rather (100) above that temperature. Evans, P R REF: Sauter, T - Contemp Phys, 2,217(1961) & D-0007 ETCH TIME: NAME: Abrasion TEMP: TYPE: Abrasive, hardness COMPOSITION: x Sic ... DISCUSSION: (1 11) specimens used in a study of D, of crystallographic directions the relative hardness in the (1 1 1) surface. There are eight (1 1 1) octahedral exterior surface planes; four bulk (100) cubic planes at 45"; and two planes at 90" in each (1 11) surface. Author says dodecahedra1 planes are resistant to abrasion. be Hardness differences can all observed using the (Note: geologic Sclerometer test - a diamond stylus across a single crystal oriented surface draw in plane direction under a specified load to determine directional bulk plane a known bulk hardness. This is a standard geological mineral test.) REF: E M - Phil Mag, 6,701(1961) Wilks, D-00 10 TIME: 5 min, nominal NAME: ETCH Soap TYPE: Detergent, cleaning TEMP: Hot COMPOSITION: . . . . Joy soap x © 1991 by CRC Press LLC

383 370 CRC Handbook Metal Etchants of DISCUSSION: D, small parts used as stand-offs in device assembly. Units as squares (1 11) oriented to metallization angled surface section. Prior an by evaporation others or rectangles, with and (Au/Cr or AulNi, respectively) as thin films, parts were degreased in hot TCE plating or vapors, soaked in a soap solution, then followed by heavy DI water and then scrubbed and washing, N, parts were photo resist patterned after cleaning, and used blow dry. Some and passive device structures. active as both REF: Fahr, F Walker, P - personal application, 198011984 & - D-0008 NAME: Methane TIME: ETCH Gas, growth TYPE: TEMP: COMPOSITION: ... x CH, DISCUSSION: carbon from methane on i-C, initially deposited predeposited with thin films of as glass gold or aluminum. Deposition of carbon was by RF plasma and films were annealed either (DLC) to develop a diamond-like-carbon which is also called the i-C structure. structure, carbon were then evaporated with additional metals and patterns developed by The films photolithography to standard MIM (metal-insulator-metal) device test structures for produce evaluation of dielectric properties of the i-C films. REF: Lamb, J D Woolam, J A - J Appl Phys, 57,5420(1985) & Szmidt, J a1 - Thin Solid Films, 110,7(1983) D-0009: et thin films by reactive pulse plasma of graphite onto silicon, (1 11) and D, deposited Used in a comparative study of diamond and boron nitride as surface (1 10) substrates. coating dielectrics. D-0011 NAME: TIME: ETCH TEMP: TYPE: Thermal, preferential COMPOSITION: . heat x . . . DISCUSSION: trigon pits on diamond the etching of (111) D, study of single crystal specimens. A surfaces. 1,1445(1968) Patel, A R & Patel, S M - Br J Appl Phys, REF: D-0012: Mitchell, E W J Phys Chem Solids, 8,444(1959) J - of work diamonds. on specimen. A review D, done D-0013 ETCH TIME: NAME: TYPE: Pressure, fabrication TEMP: COMPOSITION: . . . . pressure x DISCUSSION: Trigon system consisting of three large D, as artificial diamond. A Pressure fabricated 60' 100,000 central point capable of pressures in excess of aimed at a cylinders at pressure pressure psi. a small carbon sample at the center point on a holding base and apply Place to structurally condense the carbon to form a diamond. REF: Sci Am, (May 1978) © 1991 by CRC Press LLC

384 D-00 14 TIME: ETCH NAME: TEMP: plating Electroless, TYPE: COMPOSITION: nickel .. . . x DISCUSSION: 4 pm sized particles embedded nickel. Material fabricated by in D, polycrystalline as Method (SSM). Plated specimen the used in a study of possible catalytic Shock Sinter discs diamonds during electroless nickel plating with a phosphate type of face orientation reaction bath. 131,3026(1985) & Lancsek, T S - J Electrochem Soc, N Feldstein, REF: et Cowan, U.S. Patent 3,401,019 al D-0015: - Shock Method of fabricating polycrystalline diamonds. for Reference Sinter D-0016 ETCH TIME: NAME: Iodine Halogen, passivation Elevated TYPE: TEMP: COMPOSITION: ... x I, . . . . H,O/MeOH x DISCUSSION: as single crystal elements. Iodine washed onto surfaces as a surface passivation with D, H,PO,. adsorption. to reduce chemical attack by acids, specifically, some This acts REF: MxO MxN DIELECTRICS, or of the natural oxide or silicate minerals can be considered as dielectric General: Many are these or their artificial counterparts natural minerals so used. of compounds, and several Quartz, and corundum, AI,O, are representative of natural oxide dielectrics; zircon, SiO,, well as as a fluoride dielectric, as MgF,, as the natural halides. ZrSiO,, a silicate; sellaite, is a major dioxide, TiO,, usually as transparent, clear artificial titanium rutile, mineral The compound used in fabricating microelectronic circuits, as well as being used as dielectric . artificial gem stone "titania" the In the metal industries, the majority of the natural minerals are used as ores for general metal content, than as dielectrics, though several are used as surface coatings their rather resistance, of the nitrides All passivation, corrosion are artificial, and the nitridization for etc. surfaces with hot nitrogen gas furnace treatment has long been used for hardening of metal corrosion resistance of surfaces and metal and show dielectric properties just as do nitrides the and silicates. oxides All of minerals mentioned, nitrides and artificial compounds Technical Application: the dielectric levels are used in Solid State device specifically designed for processing. They may as discrete resistors or capacitors or be thin film coatings fabricated as planar surface as elements on a device or on a circuit substrate. As dielectric materials also have electrical and light frequency charac- of the majority they are used as filter elements, as well as capacitors or resistors, and there are teristics, materials as resistors in microelectronic fabrication that are specifically designed used ferrite microwave frequency levels. for be fatlicated as pressed powder blanks (crystalline), All of the dielectric materials may as hydrogenated as deposited amorphous as single crystal films, or films, thin films, thin such as colloidal c-SiN:H, etc. TiO,, as an example, is supplied as a pressed powder blank or oriented single crystal blank an - parallel or normal to the c-axis, each with different dielectric constant values. © 1991 by CRC Press LLC

385 CRC Metal Etchants Handbook of 372 materials The listed here but appear following their parent metals, such are dielectric not aluminum as oxide, after aluminum, etc. See individual compounds. Etching: OF DYSPROSIUM, Dy PHYSICAL PROPERTIES Lanthanide Classification 66 number Atomic 162.50 Atomic weight 1407 point Melting ("C) 2600 ("C) Boiling point 8.54 (g/cm3) Density 0.024 Thermal conductance (cal/sec)(~m~)(~C/cm) 0.041 heat (callg) Specific 25°C 25.2 of Latent heat fusion (callg) 67 vaporization of (k-caYg-atom) Heat 19.0 Atomic volume (WID) 157 1st ionization energy (k-cal/g-mole) 6.8 1st ionization potential (eV) 1.56 Covalent radius (angstroms) 0.92 (DY+~) (angstroms) Ionic radius 92.6 298 (micro ohms-cm) resistivity Electrical K 2.55 x Compressibility (cm2/kg 10.64 Magnetic moment (Bohr magnetons) 35,700 Tensile (psi) strength 32,600 Yield strength (psi) 99,800 Magnetic susceptibility ( x emu/mole) 1384 ("C) Transformation temperature 8.6 linear of Coefficient thermal expansion ( 10-6/cm/cm/0C) 25°C x 940 Cross (barns) section 3-4 Hardness (Mohs - scratch) prism, hcp (1070) Crystal structure (hexagonal - normal) Grey Color (solid) Cleavage (basal) (oO01) DYSPROSIUM: Dy a member Does native element. It is occur as a of the rare earth yttrium General: not in the lanthanide series, and is mainly found group in minerals such as gadolinite in pegmatites and with other rare earths. The fergusonite salts are noted for their brilliant yellow metal color, but there is little use of the metal in industry due to scarcity. Technical Application: There has no use of the metal in Solid State processing, to been though it has been grown as a single crystal for general morphological study. Spheres date, have been used to evaluate magnetic properties, and material defects by etching. Etching: Mixed acids with HNO, + HAc/HCl/HF/H,O,. © 1991 by CRC Press LLC

386 DYSPROSIUM ETCHANTS DY-000 1 TIME: ETCH NAME: TEMP: preferential Acid, TYPE: COMPOSITION: ... HNO, 4 6 ... HAc DISCUSSION: Solution shown as single crystal spheres in a study of magnetic properties. used Dy, used to develop defects and grain structure. 109,1544(1958) Rev, Phys, - a1 et D R REF: Behrendt, Bond, W - Rev Sci Instr, 22,344(1951) L DY-0002: Reference for method of making single crystal spheres. 25,410(1954) DY-0003: W L - Rev Sci Instr, Bond, Dy, specimens. Reference for crystal structure of the material, and other physical data. © 1991 by CRC Press LLC

387 374 CRC of Metal Etchants Handbook C,H,O,M ELECTRIDE, class of crystalline materials called "Electrides" has been developed General: A new a metal development It is a cross between alkalides. and semiconductor original from of an organic solvent molecule of cylindrical or rope-like structure enclosing fabricated from cation in a cavity. Initial development required fabrication below an alkali but 20°C, a - has produced stable compounds new 45°C. The compounds are highly reactive solvent up to can spontaneously disintegrate, but and of several millimeters in size have single crystals been by special vacuum evaporation and drying techniques. grown compounds have shown optical, opto-electric (including infrared), magnetic The and those Solid State semiconductors and, with further stability devel- properties similar to of may well lead to a new class of semiconductor compounds. Some work with other opment, semiconductors organic is included. also Application: None Technical at present. Etching: N/A at present. ELECTRIDE ETCHANTS 1 ETD-000 NAME: TIME: ETCH TYPE: TEMP: COMPOSITION: DISCUSSION: Electride, C,H,O,M, where M = Li, Na, P, K, Rb, Ce, the alkali metals. An alkali anion, such as enclosed in the cavity of a cylindrical or rope-like solvent potassium is and shows possible semiconducting properties. These compounds molecule structure, type and between metals semiconductors. are a cross color from black Vary dark blue. in to Dye, REF: L - Sci Am, (Sept J 66 1987), ORG-0002 TIME: ETCH NAME: forming TEMP: TYPE: Pressure, COMPOSITION: . . . . x pressure DISCUSSION: C,,H,,, as single crystal anthracene were grown and evaluated as an organic semicon- ductor. The material contains three benzene rings, and can be a derivative from both petro- leum and coal. Matte, H REF: Pick, H - Z Physik, 134,566(1953) & ORG-0003 NAME: TIME: ETCH TYPE: forming TEMP: Pressure, COMPOSITION: . . .. pressure x DISCUSSION: C,,H, as single crystal naphthalene were grown and evaluated as an organic semicon- can ductor. The two benzene rings, and contains be a derivative of petroleum and material coal. REF: Pick, H & Wissman, W - Z Physik, 6,959(1955) © 1991 by CRC Press LLC

388 1 ORG-000 TIME: ETCH NAME: TEMP: Pressure, forming TYPE: COMPOSITION: pressure . . . . x DISCUSSION: coal fabricated and substances, such as derivatives from petroleum as Atomatic single crystals, are predicted to have semiconducting properties. a1 J Chem Phys, 23,1733L(1955) - Many, A REF: et & POLYIMIDE EPOXY epoxies, and polyimides are artificial compounds formed by the All General: plastics, simple hydrocarbons and their derivatives. Epoxies are liquid paste for- of polymerization at self-h&dening an "A" room temperature or as as a singular compound that is mulations both component, proportionally ready for use, and when types oven cured. and "B" mixed used for mounting The epoxy compounds, alone, are nonconductive sealing compounds - metal powder additives or substrates As a loaded-epoxy parts on for sealing packages. used in the electronic and Solid State industries for the assembly -they are conductive pastes and parts. Silver of devices Ag-epoxy, has high electrical conductivity and is widely epoxy, used, although aluminum and copper are also available. As all epoxies can slowly gold, at self-harden are often refrigerated with only the quantity to be room temperature, they a specific assembly be at room temperature when ready to for used. used mixed life of 4 to 8 h, once mixed, while others may set in Some mixtures have a working sec. Both epoxies and polyimides are air oven cured between 100-150°C for 20 to 5-10 200°C, and 250-300°C capability is under devel- Some polyimides cure up to 50 min. opment. and temperature, 6 months to 1 or 2 years, even 3 years at room from Storage-life is epoxy epoxies have still useful after 3 some been and polyimide can be refrig- years. Both from +40°C, and some are kept frozen from 0 to -40°C. They are often shipped erated at - 78°C). Refrigerating extends working-life and shelf- the in dry ice (solid CO, at supplier even though they still listed for 6 months to 1 year usability. life, are physical contact danger epoxies most is no and polyimides, but there can with There If some processing problems. be overtured, particles may flake. Where silicon diodes were nitrogen in a glass package, with time, silver epoxy dried and flaked causing mounted under such that the use of epoxies and polyimides are not recommended device contact failure, high used and the mounting substrate for reliability type assemblies. Where silver epoxy is turn coal-black on plasma cleaner system, the epoxy will then put through an oxygen RF insufficient to affect electrical . . a surface silver oxide is formed. It is usually . the surface contact integrity on test samples, but such discoloration often is not acceptable for a finished product. The black oxide can be removed by rinsing assemblies in ammonium hydroxide. used Technical loaded epoxies and polyimides are and in Both unloaded Application: State devices assemblies for electrical testing. Discrete semiconductor devices, resis- Solid etc. are mounted on circuit substrates with a small dot of epoxy, or for tors, capacitors, sealing, to include a pressure extruded package. package is an epoxy mounted device failure under test, the Where there and epoxy can device 200°C), then scraping replaced by heat-charring the epoxy (heat to about be removed and circuit. There without affecting other components of the devicelepoxy is equipment away the available for this purpose . . . it consists of a hot stage, a jet of hot nitrogen, and a metal etching tong scraping. For complete removal and cleaning of a circuit substrate, acid for can be used. Etching: Mixed acids or heat. © 1991 by CRC Press LLC

389 376 CRC of Metal Etchants Handbook ETCHANTS EPOXY GOLD EPOXY EPAU-0001a TIME: min ETCH NAME: 1-3 Acid, RT TEMP: TYPE: removal COMPOSITION: 30 . HNO, . . rnl . 10 ml ... HCl ... H,O 100 ml DISCUSSION: particles in Au, spherulitic paste, such as Epo-Tech an epoxy matrix as a contact #81. as an electrical contact in device assembly. Where parts are unaffected Used or for general removal, the shown has been used removal and cleaning. Water content was etchant for depending upon variable, desired soak time. P Walker, REF: personal development/application, 198 1 - b EPAU-0001 ETCH Heat TIME: NAME: Thermal, TEMP: TYPE: removal 300-4W°C COMPOSITION: x heat ... DISCUSSION: Au, pellets in an epoxy matrix used as an electrical contact paste, such as Epo-Tech #81. Heat part carbonizes (chars) and then scrape surface to remove remaining until epoxy Carbon section char. See for specific etchants. REF: Ibid. SILVER EPOXY EPAG-000 1 a ETCH NAME: TIME: min 1-3 Acid, TYPE: removal RT TEMP: COMPOSITION: 1 HF ... . . . HN03 3 . DISCUSSION: pellets in an epoxy matrix Ag, as an electrical contact paste, such as Ablestik used #519. Widely used in assembly of semiconductor devices for electrical test evaluation and in package assembly. Solution to etch remove silver epoxy. used Walker, REF: P - personal development/application, 1980 - -- --- EPAG-000 1 b ETCH NAME: Heat TIME: TYPE: Thermal, removal TEMP: 300-400°C COMPOSITION: x ... heat DISCUSSION: Ag, pellets in an epoxy matrix used as an electrical contact paste in device and parts © 1991 by CRC Press LLC

390 assembly for in a final packaging of units. Heat part until epoxy carbonizes, test evaluation or then scrape surface for removal. Ibid. REF: ALUMINUM EPOXY I EPAL-000 NAME: Sulfuric acid TIME: ETCH TEMP: TYPE: Acid, removal Hot COMPOSITION: . . . . H2S04 x DISCUSSION: in an epoxy Al, or boron doped. Used with n-type silicon solar cells. Can pellets matrix used a contact paste on aluminum where #62 solder is used (180°C as be Ti doped m.p.). (Note: Solution is a general removal solution for plastics.) epoxy used for p-type silicon. Brochure: Electroscience Lab, NJ, 1983 REF: PROPERTIES ERBIUM, Er PHYSICAL OF Lanthanide Classification 68 Atomic number 167.28 Atomic weight 1497 Melting point ("C) 2900 ("C) Boiling point 9.05 Density (g/cm3) 0.023 (callsec)(cm2)("C/cm) Thermal conductance 0.040 25°C (callg) heat Specific 4.1 (k-callg-atom) of Heat fusion 24.5 Latent heat of fusion (cal/g/"C) 67 Heat of vaporization (k-cal/g-atom) 18.1 Atomic volume (WID) 1.57 Covalent radius (angstroms) (Er+') 0.89 Ionic radius (angstroms) (107) (lo7) 86.0 Electrical resistivity (micro ohms-cm) 298 K 9.2 of thermal linear expansion Coefficient cm/cm/"C) x 10 - ( 25°C 2.39 x lo-') Compressibility (cm2kg 166 Cross section (barns) 9.5 (Bohr magnetons) Magnetic moment 42,400 (psi) strength Tensile 38,700 strength (psi) Yield 44,100 Magnetic susceptibility emu/mole) (X 4-5 scratch) (Mohs Hardness - (ioio) hcp prism, structure (hexagonal Crystal normal) - Dark grey Color (solid) (basal) Cleavage (ooo1) ERBIUM, Er Does not occur as a native General: It is a member of the rare earth yttrium element. group in the lanthanide series (elements 63-71). Most rare earths are found in acidic pegmatite dikes: mineral gadolinite, for the yttrium group; monazite, for the cerium the group; or allinite, for both groups, e.g., cerium group includes elements 57-43, All of the in air rare earth elements are considered quite active metals similar to alkalines: they bum © 1991 by CRC Press LLC

391 CRC of Metal Etchants Handbook 378 their oxides; oxides dissolve in water to hydroxides with hydrogen evolution; and to the As their of the rarer rare earths, it erbium is one salts are brilliantly colored, often yellow. in industry. use has found little There has been only minor use in Solid State processing, to date. Technical Application: a single crystal It has a general study of the growth of rare earth elements been grown as in has used develop defects and structure. It also thermal etching been deposited by with to (magnetron) sputter and CVD as a thin film on silicon RF conversion to a silicide: with ErSi, and ErSi, for evaluation as a blocking layer in device construction. As an Er,Si, used in the growth of artificial garnets possible device additive element, it has been with applications. HF:HNO,; etc. Thermal heat treatment. HF:H,O,, Etching: Mixed acids ETCHANTS ERBIUM ER-0001 NAME: Heat TIME: ETCH TEMP: TYPE: Thermal, preferential COMPOSITION: heat ... x DISCUSSION: single crystal specimens. study of rare earth elements. After crystal Er, A growth method annealing developed defects, low angle grain boundaries, growth, other structure. Ad- and ditional metals studied were dysprosium, gadolinium, holmium, thulium, terbium, and ytt- rium. 34,3323(1963) Phys, Appl E - J H Nigh, REF: ~ ER-0002 TIME: ETCH NAME: removal TYPE: Acid, TEMP: COMPOSITION: HF ... x x . . HNO, .. DISCUSSION: Er, an evaporated thin film with Si on (110) GaAs wafers Si doped n-type used as in ERSI-0001 for heat formation of the silicide, under Silicides. etching. See a study of ion beam GAS-0247. Also Soc, Electrochem J a1 - 132,918(1985) et Wu, REF: C S -- -- ERBIUM DIHYDRIDE ETCHANTS 1 ERH-000 ETCH NAME: TIME: TYPE: Acid, Float-off TEMP: COMPOSITION: x H,O ... DISCUSSION: ErH, ErH, formed by epitaxy growth after evaporation of erbium on NaCl substrates. and at 488 K (RT) material was poly-ErH,; K using different NaCl substrate hydrogen at 298 In 1) ErH, (100) on (100) NaCl; (2) ErH, (100) on (100), (1 10) and (1 1 surface orientations: (1) the dihydride in H, will convert from the isometric-normal (cubic) (100) fcc NaCl. Heating thin film orientation to hexagonal-normal (0001) hcp ErH, structure (trihydride). Presence of H, in NaCl surfaces influences dihydride growth. The (100) NaCl substrates were cleaved; © 1991 by CRC Press LLC

392 whereas the (1 10) (1 I I) substrates were cut and polished. Both substrate polishing before and metallization and of the hydride compounds for TEM study can be done with Er float-off water. Khan, M S REF: Rahman Films, Thin 113,207(1984) Solid - ETCHING or dissolving General: Etching material by any medium: is the dissolutionment of any it will solvent as the universal is considered (H,O) water In solid. or liquid, gas chemistry, with time to the state of a water soluble salt. dissolve all natural minerals be as etching solution and, itself can brine (salt water), a major solvent of water an Salt the reflected the ocean waters of by world. Subsurface ground waters as soluble compounds contain elements, such as sulfur, iron, or silica (siliceous water) and, as such can waters hot percolate through rock fissures and strata, they become mineral formers. up nature, not are all minerals formed from solution, but are often altered after In only liquids. by of gases and action As atmospheric action, this process is called forming the in geology or oxidation in chemistry and material processing. As oxidation, iron weathering oxides (rust); the green sulfurization, to iron verdigris (copper sulfate) that appears on as is another applied to atmospheric weathering, particularly in metal copper. Corrosion term alloy evaluations, which are subjected to seacoast environments (salt air) as well as and submerged salt water. being They also are furnace evaluated under various hot gas in all for corrosion effects and chemical stability. Smog has been in existence for conditions, centuries wherever man has built a city or established an industry, such as smoke from hibachi cooking fires Japan, peat smoke in the British Isles, or exhaust smoke from the in . . . most open-hearth operations are no longer in existence due to of metal smelting ores pollution. such of the controlled cleaning and etching Needless materials is the subject of this say, to Acids, alkalies, alcohols, solvents, solid metals, or compounds are all involved, and book. names established as references been certain for different applications. Wet chemical have dry (WCE), of liquid chemicals; the use chemical etching (DCE), for the use of etching for gases; electrolytic etching (EE), where electric current is included; or molten ionized flux etching (MFE), using metals chemical compounds at elevated temperature, are liquified or the four divisions. There are other primary etching methods, and many subcategories main beyond these four, such as the difference between a molecular and ionized gas, the use of been pressure, only, vacuum, etc. This section has use of assembled where the or the to due "NIA" in the be shown as nature, or may articles are general reference referenced usage. common metals and metallic compounds by individual names Technical Application: See specific additional detailed solutions and their applications. for Etching: Generalized. See individual elements and compounds for specific solutions. ETCHANTS ETCHING DIRECT PRESSURE ETCHING (DPE) 1 PRE-000 Pressure TIME: ETCH NAME: Pressure, forming TEMP: RT TYPE: molten to COMPOSITION: x . . . . pressure DISCUSSION: Direct pressure can be an etching agent, though more often as a forming vehicle. In furnace reduction of metal ores, the hot, liquid metal is extracted at atmospheric pressure, © 1991 by CRC Press LLC

393 CRC of Metal Etchants Handbook 380 a raw ingot pigs in the metal industry. Subsequent alloys and parts are and poured as called mixtures, and re-melted as can rough with final lathe grinding1 into forms for shape be poured molds often include pressure as part of the shaping cutting Some to shape. Such technique. as hot formed from a melt in pressurized ruby, are directly as rods, such oxides, molds through heated - - metal through diamond hole-dies (wire) extrusion sheet, etc. Pressure sheet) into a form (plastic packages, lamp shades, etc.). This may (metallglass - rollers forming such as heating a plastic sheet, then include vacuum to draw vacuum pulling a light to shape (TV modules, tote boxes, a desired It may be as direct pressure the material etc.). such as in the compaction of powders (medical pills, metal or plastic parts), and molding, can include heat the material during forming. Extrusion molding is used to form a to melt compound around a device or as a package. plastic assembly compounds, as the micas, are obtained by striking the Pressure such figures on certain (0001) basal plane six-rayed percussion figure on an micas this On surface. produces a iron a combination by Meteoric of heat surfaces have classified structure developed surface. passage through the atmosphere. pressure during and are subjected to increasingly high pressure in Solid State study Single crystals of high - silicon has at least six such crystallographic structures pressure crystallographic structures irons hexagonal steels have alpha, beta and delta phase structures - ice is normally - and but high system, pressure transition form that is isometric (cubic) system, and many has a other and compounds, both natural and artificial, have similar transition pressures1 metals temperatures with an alteration of the atomic lattice to that of another crystal system. In 300,000 atm are used on rocks in the study geology pressures on the order of and physics, NaCl, has been pressurized magma formation. Solid State, liquified sodium chloride, of In plates and a material study, glass many ferrite compounds are similarly in between two has been converted to diamond by direct pressure only. Carbon pressure studied. See individual metals and compounds for specific applications. REF: CHEMICAL ETCHING DRY (DCE) DCE-0001 NAME: RF plasma TIME: ETCH TEMP: cleaningldefect gas, TYPE: Ionized COMPOSITION: GAS FLOW: PRESSURE: ... CF, x POWER: 0, (5%) ... x DISCUSSION: As singular or mixed gases applied by Gas, ionized. an or DC plasma to effect RF etching action for cleaning, general preferential etching or surface structuring. The mixture shown has general usage, and there are several others with specific design applications. ion cleaning, is a fairly standard practice before sputter metallization, Ar+ Argon, as metallic compound Most vacuum sputter systems have one to four alloy, or deposition. with one location used for argon ion cleaning. Specimens are target locations a placed on rotating below the targets, platen Ar+ cleaned, then the platen rotated beneath sputter ion targets for metal or compound deposition. These systems may include a magnet on targets, and are called RF magnetron sputter systems. then BCl,, C1+ or the method is called reactive ion etching as a gas is Where reactive, such (RIE), and there are other acronyms for similar specialized systems. The mixture shown can classified in this category. be RF plasma cleaning systems using N+ or O+ ions are widely used in Solid State material © 1991 by CRC Press LLC

394 processing, such for surface cleaning of semiconductor wafers, or their substrate circuit as of cleaning organic contamination from surfaces, and has assemblies. This form removes removal been used thin films. of for etch germanium uses the RF plasma of argon. In this case, also vacuum system has a an Ion milling which a substrate is waxed down with a low vapor on plate tillable and/or rotatable copper such as pressure M, and a controlled jet of ionized argon used to etch pattern wax, Apiezon thin film a circuit substrate, or similar pattern etch a device structure the metallization for irradiation. Ion a wafer. a general term for similar action, as is bombardment The on is both gas ions latter referring to , He+, Xe', Ne', N', 0+, etc.) and ionized particles: (H' etc. All such etching is done under vacuum conditions, protons, neutrons, deutrons, electrons, electron irradiation can done with an electron microscope (EM), or transmission though be microscope (TEM). electron An ion implantation, 12, where ionized gases are implanted into a is allied operation form p-n junctions, or semiconductor wafer to n+ layers, such p+ in forming semi- and as structures (SI). Both gallium arsenide, as GaAs:Cr, (100) (SI), and indium phos- insulated phide, 1nP:Fe (100) (SI) wafers, as examples. ionized can produce sub-surface damage in materials or thin films and, as All gases many metals and metallic compounds have been studied for such effects. This irradiation, includes effects on thin adhesion, amorphatization, and high reliability radiation testing film chemical etching (DCE) Van with or Triga facilities. Dry der is strictly the use of Graaf ionized gases, not gases used in their molecular state. The latter are included here in this text as of wet chemical etching (WCE). a subsection Bierlein, REF: & T - Rev Sci Insrrum, 30,832(1959) Mastel, K B for specific applications. See individual REF: metals/compounds ELECTROLYTIC ETCHING, EE EE-000 1 TIME: ETCH NAME: Electrolytic etching Electrolytic, TEMP: TYPE: polish ANODE: COMPOSITION: CATHODE: (1) x . . . . acids/salts POWER: alkalies . . . . (2) x . . . . alcohol (3) x DISCUSSION: Any solution used with an electric current applied between Electrolytic etching. liquid the positive +) anode and negative ( - ) cathode to effect anodic etching action where the ( being processed is part anode. Although cathodic etching is referred to in the literature, the as such, it a deplating or film removal type action, not true etching of a bulk part. is Switching from anode-to-cathode is done in some etching sequences, as in growing a hydrated oxide on surface such as silicon. The power applied varies with the type material, a metal metals usually in the milliampere range; whereas with oxides, nitrides, and silicates, and are the insulator materials require amperage levels of current. In electrolytic etching, effectively, both an ampere voltage level and used very should be shown, although are often only and amperes are shown. Many industrial metals and alloys are best electrolytically etched, the but most of the Solid State semiconductor type materials use wet chemical etching. Elec- used trolytic include the use of molecular gas bubbled through a solution, often may etching as a jet etch system. Metal plating from solution is another method of using electrical current applied to a liquid mixture containing a metal salt, such as gold, nickel, copper or chromium sulfides, per chlorides, cyanides, This is not a plating book, etc. se, such that only a few plating © 1991 by CRC Press LLC

395 CRC of Metal Etchants Handbook 382 shown where they systems are used in processing Solid State materials. Electrolytic are widely electroless with nickel under gold from cyanide baths plating, used films, in thin Au/Ni substrate circuit fabrication; or Au, Ag both Cu plating of p-n device junctions, device and and etchant format All appear in this book (Note: in the examples. two as electrolytic solutions "chemical" descriptor term TYPE is always "Electrolytic", first of shown, above. The an "Application" term, as shown above. This approach has been used due followed by to number electrolytic applications involved, even though standard practice would of the say: electropolish, electroplating, etc .) REF: N/A Niggins, J K - J Electrochem Soc, 106,999(1959) EE-0002: Electrolytic etching a study of anodic dissolution of metals and electropolishing. in Rowland, P R 171,931(1963) EE-0003: -Nature the mechanisms electropolishing. of of A study F A - Modern Electroplating, 3rd ed, John Wiley & EE-0004: New Lowenheim, Sons, York, 1974, 52 The electroplating of metals. Includes specific cleaning chemicals and procedures for of materials for plating, as well as plating formulas preparation processes. and REF: See individual where solutions are Electrolytic Format. metals/compounds listed in this (GE) ETCHING GAS 1 GE-000 TIME: ETCH NAME: Hydrogen TEMP: 500-1500°C Gas, TYPE: removaUgrowth COMPOSITION: ... H, x DISCUSSION: used in Gas or gas mixtures or etching action. their molecular state to effect a cleaning Hydrogen firing (reducing atmosphere) - also called furnace firing - is used to remove surface oxides or in the alloy of assembly of parts, to prevent oxidation; and with scale; to hydrogenate pressure included, materials etc.). gas (FG) 85% SiC:H, Forming (Si:H, is used in a similar manner, but is nonflammable or N,:15% H, explosive. in are used as furnace gases at general processing and, Ar, He, etc.) Inert gases (N,, temperature, some are used for elevated reactive qualities, such as nitrogen for surface their . . . combined, these two gases will thin film nitridization, oxygen to grow an oxide or inert gases oxynitrides. open atmosphere, at RT to hot, In the form - N,, most common- ly - but also Ar or He are used as pressure jet blow-off drying systems, or parts are dried in air, without heating (IR lamps, hot plates, etc.). Flame torches are another use with and gases, acetylene; oxyhydrogen; and propylene among the leaders. Such torches are of with for soldering, brazing, drying, or cleaning of used and assemblies. Other gases are parts chlorine as vapors from acids, used as hot from hydrochloric acid, or oxygen from such water, nitric acid and hydrogen peroxide. Chlorine to clean surfaces, oxygen to either oxidize or a surface cleaning step with the oxide removed with hydrofluoric acid. as In any case, this is the use of gases in their molecular state, not as dry chemical etching (DCE) with the gas in its ionized state. REF: See individual materials, general formats. © 1991 by CRC Press LLC

396 MOLTEN FLUX ETCHING (MFE) 1 MFE-000 TIME: Variable ETCH NAME: Molten flux etching preferential TEMP: TYPE: Salt, Elevated COMPOSITION: KOH, Fe etc. ... NaCI, x DISCUSSION: use of a salt flux etching Molten is the (Fe, Cu, etc.); an alkali (KOH, (NaCI); a metal from etc.) state, liquified at their melting point temperature to effect NaOH, their solid or of defects. They can polishing development removal, K0H:NaOH (eutectic), be mixtures: or etc. High temperature, chemically inert metals, such as titanium or mo- NaCI:NaCO,, so etched for both cleaning and lybdenum, are of surfaces. On single crystals, polishing such molten flux alkalies are used for defect development. Molten metals may as silicon, the primary on certain other metals, or be diffused into another to be etching mediums and structure. decorate and enhance dislocations, defects, Molten fluxes also used for single crystal growth of materials, such as garnets and are femtes. The wet chemical etching (WCE) general format is to present molten fluxes, etchant used well as metals, by name, as used as an etching medium or method of decorating when defects. Note that tin and zinc are plated from molten fluxes, as tin plating or galvanized zinc. The part the molten metal, then withdrawn with a thin coated surface. is dipped into See individual materials for specific applications. REF: THERMAL ETCHING (THE) 1 THE-000 ETCH NAME: TIME: Thermal etching TYPE: Thermal, removalldefect TEMP: Elevated COMPOSITION: ... heat x DISCUSSION: etching of metals and compounds is the use of Thermal as an etching medium. pure heat The reference shown as a study of the influence on surface energy of below metals. But thermal etching also is used to develop etch figures on any metal surface or, if a single crystal, to develop dislocations, defects, and structure. Pure thermal etching is done under vacuum conditions; otherwise a gas included, such as in furnace heat treatment and is use only can heat annealing. The of for surface cleaning and, drying be where a specimen and is heated on plate in air, it is called heat-tinting a hot . . . oxide colors used to differentiate conditions sample structure of metals subjected to various test metallographic study of in strain, fatigue, etc. REF: Moore, A J - Acta Metall, 6,293(1958) REF: See individual metals/compounds shown as heat and thermal etching in the wet chemical etching format. © 1991 by CRC Press LLC

397 CRC of Metal Etchants Handbook 384 ETCHING (VE) VACUUM VE-000 1 TIME: ETCH NAME: TYPE: Vacuum, preferential TEMP: Cryogenic to ele- vated COMPOSITION: VACUUM: to 10-10 vacuum Torr ... x . DISCUSSION: as a preferential etching vehicle, Vacuum, often includes a temperature level. used and thermal treatment, ingots, wafers, or parts are subjected to elevated temperatures heat As to some up 2000°C under vacuum; gases are grown as single crystals under pressure cryogenic in vacuum, and the changes in vapor pressure of the system used to preferentially conditions an ultra high vacuum (UHV), etch structure. It has observed that some metals, under been also is shown surface etching effects or hillocks. Vacuum pits used as a drying have as in metal processing, as well as in food processing. medium See REF: individual materials, general formats. (WCE) WET CHEMICAL ETCHING WDC-0001 ETCH Wet chemical etching NAME: TIME: Variable TYPE: Chemical, removalldefect TEMP: Cold, to hot RT COMPOSITION: x . . . . chemicals, solvents, alcohols DISCUSSION: Wet chemical etching is the use of liquids for etching, cleaning, or development of structure, as acids, bases, alcohols or solvents. This is the method of processing primary include gases, such metals compounds, and may metallic as bubble chlorine through and all to etch solution an accentuate multilayer as in plating out from intense or etch; an light, p-n semiconductor devices. structure or junctions in majority of solutions shown in this The are WCE with the format as shown above. book The format also is used for all chemical processing not covered by DCE; EE; or the other methods discussed this in section. individual the under See specific materials. solutions REF: Eu OF EUROPIUM, PHYSICAL PROPERTIES Classification Lanthanide number Atomic 63 Atomic weight 152 point Melting ("C) 826 Boiling point ("C) 1439 Density (g/cm3) 5.26 (callg) 25°C Specific heat 0.0395 Heat of fusion (k-cal/g-atom) Latent fusion of heat (callg) vaporization of Heat (k-callg-atom) Atomic volume (WID) ionization energy (K-callg-mole) 1st © 1991 by CRC Press LLC

398 1st ionization potential (eV) Covalent radius (angstroms) radius (angstroms) Ionic K Electrical resistivity (micro-cm) 298 (cm2/kg X Compressibility Neutron cross section (barns) Magnetic moment (Bohr magnetons) x emu/mole) ( susceptibility Magnetic of thermal linear expansion Coefficient ( x cm/cm/"C) 20°C 2-3 scratch) - (Mohs Hardness bcc (100) cube, normal) - structure (isometric Crystal Steel-grey (solid) Color (cubic) Cleavage (000) EUROPIUM, Eu in it occurs it is extremely rare, as a member of the Rare Earth General: Although nature of elements, and usually assigned to the yttrium sub-group even when found with group in formula, and with a Be,FeY,Si,O,,, is variable sub-group elements. Gadolinite, cerium As "gadolinite earths" the variety is high high cerium oxide content called cergadolinite. yttrium sub-group elements. Often occurs in pegmatites with other rare earth bearing in is similarly variable in rare earth content, and there are (Ce,La,Di)PO, Monazite, minerals. deposits as monazite sands. Monazite often contains a high percentage of some commercial Tho,, mined chiefly for that compound in India. oxide, thorium All rare earths are considered quite active metals, similar to calcium: bum in air they their oxides: the oxides dissolve water with a hissing sound, like quicklime; and to in use in industry due to scarcity. hydroxides are alkaline. Europium has little No major use in Solid State processing at present, Technical Application: though there is a europium containing artificially grown garnet may have use as an optical device, which etc. filter element, as a single crystal and studied for its physical properties, to Europium has been grown paramagnetic behavior. include Etching: Air conversion to oxide. ETCHANTS EUROPIUM 1 EU-000 TIME: ETCH NAME: Argon RT TEMP: Gas, storage TYPE: COMPOSITION: ... Ar x DISCUSSION: specimens. Samples processed under argon. Fresh surfaces prepared by cutting with Eu a knife, then wrapped in tantalum foil and stored in a silica capsule under argon to maintain a bright used in a study of paramagnetic behavior. surface. Specimens REF: Colvin, R V et al - Phys Rev, 122,14(1961). © 1991 by CRC Press LLC

399 CRC Handbook Metal Etchunts of 386 PROPERTIES OF EUROPIUM Eu,O, PHYSICAL OXIDE, Rare earth Classification 63 8 & Atomic numbers Atomic weight 352 Melting point ("C) Boiling point ("C) 7.42 (g/cm3) Density Hardness (Mohs - scratch) 4-5 normal) (isometric Crystal structure (100) cube - Pale rose Color (solid) Cleavage (cubic) (001) OXIDE, Eu,O, EUROPIUM not occur as a natural compound by itself, General: Does it may be an oxide, though in from the mineral gadolinite (see Europium for further discussion). part, as extracted Application: in Solid State processing at present, though europium Technical Not used is one constituent in some artificial garnets. The oxide is obtained by burning the metal in color in and the oxide is hygroscopic. The oxide is pale rose air, and called europia. metal Etching: Soluble in water. EUROPIUM OXIDE ETCHANTS 1 EUO-000 TIME: ETCH NAME: Water TEMP: Acid, TYPE: removal COMPOSITION: x ... H,O DISCUSSION: specimens. Material will dissolve in water with a hissing sound like quicklime, Eu,03 resulting hydroxide is and alkaline. Foster, REF: 3rd & - An Introduction W General Chemistry, Alyea, H N ed, D Van to Nostrand, New York, 1941, 423 EUROPIUM SULFIDE ETCHANTS EUS-0001 NAME: TIME: ETCH TYPE: TEMP: COMPOSITION: DISCUSSION: single crystal spheres fabricated for general morphological study. No etch shown. EuS, are highly reactive. earth element, and both the element and its compounds Europium is a rare As a sulfur compound, it can probably be etched in CS, like sulfur. this is REF: Franzblau, M L et a1 - J Appl Phys, 38,4462(1967) © 1991 by CRC Press LLC

400 FERRIC OXIDE, Fe,O, in nature the iron mineral hematite, Fe203 - common name red General: Occurs as and is a major ore iron. It is found in rocks of all ages and in several forms, iron ore, of botryoidal in to massive earthy "red ocher"; in black from single crystals resplendent color ore"; as ''oolitic hematite", originating probable colloidal precipitate "kidney as a as shape waters around a central sand-grain from forming much like a pearl iron bearing ocean core, oyster. in an be so when it is an admixture of hematite magnetic, it may appear to Although it is not with Fe304 black iron ore. Both occur magnetic the mineral corundum, - magnetite, and Al,03:Fe203/Fe304. Hematite can be distinguished A1203 its cherry-red streak, as emery, by in infusibility a and can be burner flame, to a grey magnetic powder with bunsen reduced soda an RF flame. in Industrially ore of iron. As powder, it is a red paint pigment, and a coloring it is a major in glass, ceramics enamels. Also as a powder, it is "red rouge", used both in agent and as of and polishing abrasive with a Mohs hardness and about H cosmetics a lapping 6. = fabricated artificially by treating ferric chloride be steam at high temperature; or It can with the action of air and hydrochloric acid by iron; and formed from several molten fluxes. on Technical As Application: oxide sesquioxide) it has no direct application in ferric (iron State device fabrication. It is used as a lapping abrasive, as a thin film in the fabrication Solid As of masks; and as an optical filter. resist photo MFe304, it is fabricated as microwave and memory devices; as M,Fe,O,, (garnet) for bubble memory devices, microwave filters, PbFe,,O,,. As already mentioned, also as thin film, and and as surface devices wave photo resist mask. semitransparent in Etching: Slowly HCI. Hematite, Fe203 See FERRIC ETCHANTS OXIDE FEO- 1000 TIME: NAME: Hydrochloric acid ETCH TYPE: Acid, removal TEMP: Warm COMPOSITION: x conc. ... HCI, DISCUSSION: resist on Fe20, a photo film deposited mask. Film patterned by thin soda-lime glass as and etched in hydrochloric acid in photolithography masks for semicon- fabricating photo ductor widely used than chromium as it is harder, less prone to physical processing. More damage, and more handling stable. REF: R - Lipman, communication, 1983 personal - - FeM,M, FERRITE, word Latin: General: The fermm, hence the symbol for iron, Fe, and the word is from "iron" is Native iron does occur, occasionally in large ore bodies, but more Anglo-Saxon. often as small grains in other rocks of basic origin. Iron occurs with two valences: Femc, Fe+ + Ferrous, Fe+ + + , and magnetic iron (extracted from magnetite, Fe,04) contains and valences, it is called ferrosofemc iron. iron of both such that less processing the femte refers to soft In iron with term than iron 0.04% carbon, also called wrought iron . . . the original form of iron first smelted by the Hittites in Asia Minor (Turkey) around 1350 is metallographic used for decorative purposes. In B.C. and still recognized as a constituent by its soft dove-grey color. be it can specimens . . . even refers to a group of metallic compounds as a class of materials Femte also metal iron have been called oxides containing ferrites. In effect, any material containing © 1991 by CRC Press LLC

401 388 CRC of Metal Etchants Handbook may be to as a femtic compound, ferrous or femc, depending upon iron iron referred femte valence. interest for their ferromagnetic, ferro-electric, or compounds are All of ferro- several developed operational devices in with Solid State. optic capabilities as In of semiconductor device assemblies, Application: Technical Solid State development a class of been designed as resistor materials ferrites particular metal additives, has with andlor frequency levels associated with as zinc, manganese, for specific power such etc., - dark black, highly microelectronic circuitry. They are supplied as square blanks the thickness ranges polished surfaces 0.0005 to 0.025, and 1 in of 1" square or larger. X The blanks metallized by plating are or evaporatedtsputtered and other combi- (Au/Ni) (Au/Cr cut to size as a discrete resistor element. Metallization of femte nations), then the required difficult adhesion can be be for, like other highly polished surfaces, metal can this of type when used can be Sic) possible (not abrasion (400-grit by Roughing the a problem. face air - 10 min at 200°C on a hot plate in - will for high lightly oxidizing frequency), or the aid in film metal adhesion. thin Most ferrites as resistor elements are crystalline, pressed powder blanks; others used and Iron, Alloys, Iron See Fe3C. as iron such single crystals, as grown been have carbide, additional discussion Steel sections for and etchant solutions. Etching: mixed acids. Nital, Picral, and ETCHANTS FERRITE 1 HCFE-000 sec 10-60 TIME: ETCH NAME: Kalling's etch RT TEMP: polish TYPE: Acid, COMPOSITION: ml ... HCI 100 ... CuCI, 5g ml ... EOH 100 DISCUSSION: Ho2Co14Fe3 melt fabricated, and used in a study of metallic compounds. specimens arc See Ho2Fel,. studied etchant. Also Cesium a general removal and polishing used Solution as for materials studied. Platinide other 65,293(1983) a1 - J Cryst Growth, Slepowronsky, M et REF: MAGT-0004 ETCH NAME: Hydrochloric acid TIME: TYPE: Acid, TEMP: removal COMPOSITION: x HCl, conc. ... DISCUSSION: specimens from ingots grown by the Czochralski (CZ) method. A study of single Fe,04, Other doped materials by this method. grown iron ferrites were ZnO, Ga,O,, iron crystal and MnO. CuO, REF: Horn, F N - J Appl Phys 32,900(1961) FER-0001a: - mineral study, 1950-1964 P Walker, natural single crystal specimens used in a study of iron oxides. Solution used Fe304 as lHCI:lH,O for surface cleaning. Also studied other natural iron spec- concentrated, and 2Fe203.3H,0 Fe,O,, limonite, and goethite, Fe,O,.H,O [FeO(OH)]. hematite, of imens © 1991 by CRC Press LLC

402 FER-000 1 b TIME: ETCH NAME: Trichloroethylene TEMP: 85°C Solvent, cleaning TYPE: COMPOSITION: TCE, ... . vapor x DISCUSSION: used resistor material for microelectronic circuits. Fe:Mn:Zn, pressed powder blanks as X 1 X .0151.025" size. 1 degreasing in TCE, bake After vapor highly polished Blanks were out in air oven at 30 150°C prior to metallizing with AuINi plating or AuICr for min evaporation. REF: Walker, P et personal 1980-1985 - application, a1 D H - FER-0002: Vac Sci Technol, A3(3),762(1985) Buckley, J Fe:Mn:Zn Fe:Ni:Zn ferrites used in a study of ceramic and microstructure and adhesion of films. The iron absorbs thin even 0, under argon. The study applied sliding in vacuum or metal thin across the surfaces. The metal film remains in place, and bonding contacts film across and were Be surfaces 0,. Cu, Ni, Rh, Co, rubbed of the by assisted was presence this evaluation. in FER-0003 TIME: ETCH NAME: TYPE: Thermal, TEMP: Elevated defect COMPOSITION: .. . . x heat DISCUSSION: a study specimens material used Ferrite as crystalline to determine directions of in magnetization in polycrystalline ferrites. Thermal etching was better than chemical etching to develop well grain boundaries with the remainder of the surfaces relatively smooth. defined thermal etch: mechanically polish surface, then hold in furnace for To first, at the 10 min same temperature and atmosphere used for annealinglsintering. REF: D R - Phys Rev, S31.3758(1961) Callaby, FER-0004 ETCH TIME: NAME: cleaning TYPE: Acid, TEMP: COMPOSITION: x ... HF . .. . HNO, x x ... EOH DISCUSSION: MFeM,, material grown in new semiconducting type compounds as ferrites. evaluating M = Ag, Cu, and M, = S, Se, Te. Solution shown can be used for general cleaning. REF: Zhuze, P et - Zh Tekh Fiz, 28,233(1958) U a1 -- - MAGT-0005 NAME: TIME: ETCH (1) Boiling TEMP: TYPE: Acid, removal (2) Molten COMPOSITION: fused NaSO,, . . . . (2) x (1) conc. ... x HCl, DISCUSSION: Fe,O, single crystal material grown in a "skull melter" with RF generator. This was to Fe,O, FeTiO, (natural mineral is ilmenite). The titano- series from an isomorphic ingot © 1991 by CRC Press LLC

403 390 CRC of Metal Etchants Handbook grown by control (fugacity, fO,). During growth, 0, concentration magnetites are oxygen with was buffered of tin or tin foil to either With shown above, CO,/CO. addition solution dissolved containing and a brown-violet to fine blue or violet color is ferritic material, (Note: This color reaction in solution depending on amount of titanium present. observed the min- pyrolytic solutions a primary method used in determinative containing Ti has in been of ilmenite for many years.) eralogy Growth, J a1 - 61,221(1983) Cryst Aragon, R et REF: COFE-0001 ETCH TIME: NAME: Nital removal Acid, TYPE: TEMP: COMPOSITION: x ... HNO, EOH x ... DISCUSSION: grown cut from ingots wafers by the Verneuil arc-image furnace method. CoFeO, (100) and mechanically polishing, re-anneal at 1200°C After cutting in air for femte several days CoO,(Co,~,Fe,)O. material FIoshino, 46,229(1985) & Peterson, R L - J Phys Chem Solids, REF: K - --- 1 RFE-000 ETCH NAME: Nital TIME: Acid, removal TEMP: TYPE: COMPOSITION: x . . . . HNO, x ... EOH DISCUSSION: as rare ferrites. R = Sm, Gd, Tb, Dy, Ho, and Er. Materials were fabricated We,, earth were arc furnace under argon. Then ingots melt annealed 200 h in sealed quartz in an ampoules. Klirnker, H et a1 - J Phys Chem Solids, 46,157(1985) REF: PROPERTIES PHYSICAL (CaF)Ca,(PO,), OF FLUORAPATITE, Phosphate Classification & 8 20, 9, 15, numbers Atomic 480 Atomic weight 1 200 ("C) point Melting ("C) Boiling point 3.17-3.23 Density (g/cm3) 1.630-1.648 Refractive index (n ) = 5 Hardness (Mohs scratch) - 3rd (2130) prism, order Crystal structure (hexagonal tripyramidal) - Colorless to colored Color (solid) Cleavage (basal imperfect) - (O001) FLUORAPATITE, (CaF)Ca,(POJ, As the natural mineral "apatite", General: are two major subspecies: fluor- and there chloroapatite, with the former more common, and there are a number of additional varieties of differing constituent composition among, subspecies. It is quite widely distributed, the two often occurring in iron and tin mines. It has a variety of colors - blue, yellow, green, pink, © 1991 by CRC Press LLC

404 brown and white. been used as gem stones, even though The fine transparent varieties have soft the mineral is Along with other phosphate rocks and minerals, for this relatively purpose. primary use as industrial fertilizers. apatites the have single crystals have been grown and Technical use Application: Apatite-type doped for long-pulse laser devices, both as a phosphate, and as a silicate oxy-apatite (no as CW chloro- otherwise similar in crystal structure. The fluorapatite, rather than phosphate), but the base material, and doping elements are rare earths. The silicate types are apatite, is developed as lasers. being improved Q-switch regia; fluorine and molten fluxes. Etching: Aqua salts, FLUORAPATITE ETCHANTS FAP-000 1 a min 1-3 TIME: ETCH NAME: Aqua regia TEMP: RT preferential Acid, TYPE: COMPOSITION: ... HCI 3 1 HNO, . . . . DISCUSSION: grown single crystals Ca,(PO,),F:Nd with neodymium, and used as artificially doped long pulse CW lasers. In this study a series of silicate oxy-apatites were grown as possible as MeLn,(SiO,),O for improved Q-switch lasers. General formula of these compounds: materials with Me Mg, Ca, and Ln = Y, La, Gd. SrLa,(SiO,),O and CaLa,(SiO,),O discussed = IrO flakes under in an iridium boat melt argon, and some detail. Crystals grown in were NaF:KF single crystal wafers. Polish wafers in molten eutectic flux: were observed on the prior at 350°C with aqua regia. Aqua regia develops pits at dislocation to preferential etching (Note: Formula for natural fluorapatite is sites. (CaF)Ca,(PO,),, as chloroapatite is and (CaCI)Ca,(PO,),). REF: Hopkins, R H et al - J Electrochem Soc, 1 18,637(197 1) FAP-000 1 b TIME: ETCH NAME: TEMP: 350°C TYPE: Molten flux, polish COMPOSITION: ... NaF 1 1 ... KF DISCUSSION: Ca,(PO,),F and silicate oxy-apatites. Single crystal specimen wafers were polished in FAP-0001a eutectic molten flux shown prior to dislocation etching with aqua regia. See the for further discussion. Ibid. REF PHYSICAL PROPERTIES OF FLUORINE, F, Classification Halogen 9 number Atomic (F2) 38 Atomic weight 233 - Melting point ("C) - 187 ("C) point Boiling © 1991 by CRC Press LLC

405 392 CRC of Metal Etchunts Handbook (g/cm3 Density - 187°C - solid) 1.108 - 18°C (g/l liquid) 1.69 conductance Thermal 20°C cal/cm2/cm/"C/sec) x ( 0.579 (cal/gI0C) 20°C Specific heat 0.18 (callg) Latent heat of fusion 10.1 1st ionization potential (eV) 17.42 Ionic radius (angstroms) 1.33 (F) (barns) Cross section 0.010 ("C) Vapor pressure 202.7 = ) (n index Refractive 1.000195 Hardness (Mohs scratch) solid - 1-2 - normal) solid Crystal structure (isometric (100) cube Color (solid) Yellow-green (liquid) Yellow-green Pale yellow (gas) - solid) Cleavage (cubic 1) (000 FLUORINE CONTAINING ETCHANTS greenish yellow gas at standard temperature and pressure (22.2"C and Fluorine is a pale with mrnHg) be condensed as a pale-yellow liquid can a boiling point of - 187°C. that 760 reactive element known and a member of the It is the most group of elements which halogen includes and iodine, in order of reactivity. Chlorine, too, is a gas; bromine chlorine, bromine, and iodine a solid. Fluorine does occur as a free element in nature although a liquid; not hydrogen found in association with volcanic activity. The traces of fluoride are occasionally as a flux material used been CaF,, which has in mineral is fluorite, known best fluorine "fluorspar" even before discovery of fluorine and its establishment as a the as metallurgy element in 1886 separate Moissan. Prior to its discovery, fluorspar was known to contain by calcium some other element that reacted much like chlorine. Because of its high reactivity and - it will catch fire elements as sulfur, phosphorus, carbon, silicon, and boron with such fluorine, although most metals, with in exception of gold and platinum, will bum in the the presence of the gas. Of all of the compounds of fluorine, the best known is probably hydrogen fluoride, HF - better It is the primary etch for glass, with silicon tetrafluoride, known as hydrofluoric acid. a gaseous is etched by either immersion in the liquid (a smooth as SiF,, by-product. Glass vapor (a rough surface). The latter is widely used for pattern etching of glass surface) or by objects drinking glassware, plates, objets d'art. Microscope slides have been vapor - and deposits where, after roughen surface for improved adhesion of thin film metal to etched the e.g., immersion in HF. the float-off technique, deposition, the metal film is removed by morphological and thin prepared in this manner for have been defect study under Gold films power magnification. high Si3N4 nitride, SiO,, and silicon semiconductor wafers, silicon dioxide, processing In as thin films - 1000 to 3000 A thick - and used as masks against subsequent are deposited oxidelnitride surfaces are photolithograph- epitaxy growth. The pattern etching, diffusion or ically processed by UV exposure of a photo resist coating. The with patterns developed hydrofluoric acid or then removed by etching with oxide or a mixture of underlying nitride to expose the semiconductor surface for diffusion, etching, epitaxy etc. The HF:NH4F solutions are called hydrofluoric acid (BHF) etchants. The ammonium buffered HF:NH4F fluoride, is commonly used as a 40% concentration and added to concentrated HF, NH4F, NH4F saturated is sometimes added as a saturated solution (sat. sol.). This although it solution in is a primary HF for etchant of quartz crystal blanks used for frequency tuning or individual preference by varies NH4F of As radiofrequency devices. the concentration application, the acronym BHF should be considered a general classification term, not a referred specific Such solutions also have been etch mixture. to as buffered oxide etch © 1991 by CRC Press LLC

406 (BOE), though mixture ratio of HF to NH,F varies from BHF is more common. The to 1HF:100NH4F, sol., and may include dilution with water, and the lHF:lNH,F(40%) sat. may fluoride ammonium ammonium bifluoride, NH,F.HF. be with replaced etching cleaning solutions on both semicon- as and Other fluoride compounds are used NaF and as sodium and potassium fluoride, ductors and other metals and compounds such be KF, as solutions for wet chemical respectively. These halide-type compounds used may molten flux etching. as or electrolytic etching or or HF:HNO,:HAc HF:HNO,:H,O HF:HNO,; of HF acid all the Of mixtures, solutions - - etch solutions for a wide range are the oxidation-reduction systems most widely used processing no, or limited, solubility in single acids. Under- material of where they have hundreds of possible ratio combinations standably, there such mixtures and every are with as laboratory, establishes their own particular mixtures required for a specific process step. Much has done and is development and study and been still being done, on these solutions Etchant Section are of this type. Generally speaking, many of the mixtures referenced in this etchants within certain limits: when high in HF or of all solutions are polishing-type these they are self-limiting where excessive reduction or passivation HNO, oxidation produces a used "stain" etch as they produce recognizable color Such solutions are reaction. surface as it is, in effect, a fluorine-burn; whereas patterns. The HF type stain is difficult to remove the The an oxide and easily removed with HF. is most rapid mixture is 1HF:3HNO3, HNO, stain either water, H20 or glacial acetic acid, CH,COOH (HAc or GLA) is used as and inhibitor an or control agent. Although glycerin is sometimes added to these solutions as a viscosity rate glycerin are the precursor agent, it recommended as nitric acid and not mix for control is CH,OHCH,OH, is recom- is required, ethylene glycol, nitroglycerin. If viscosity control The excessive addition mended. water or acetic acid to of mixtures can severely HEHNO, polishing action to the point where controlled etch reaction is highly erratic and results alter are poor. Most of the solutions are used at room temperature, due to their relatively high reactivity and exothermic nature for batch etching of semiconductor wafers, etching is and, done often in a controlled temperature bath. as well other etchants, become progressively preferential as as These solutions, most at toward reduced of their polishing capability 0°C. room tem- is temperature regardless in chilled 8"C, acetone; others with a mixture of ice used at perature. Several mixtures are etchants 0°C. for surface cleaning, used are Such cold nitrogen for with at use chilled liquid etc. junction device, etchants for structure, electrical tuning of a p-n preferential or as slow HF:H202:H,0 solutions where the nitric acid widely used HF mixtures are the Other peroxide, been the oxidizer by hydrogen as replaced has Hydrogen peroxide is supplied H202. should This 30% solution and, chemically, is called "superoxol". not a commercially as confused #2): the etchant that also is called superoxol (Camp be lHF:1H202:4H20 with (GE-0065a). In addition, there is an etch solution called "Peroxide Etch": 1 mlHF:l mlH202: 1HAc (see GE-00600, which should not be confused with the concentrated or dilute H202. pure hydrofluoriclhydrogen peroxide are polishing solutions on most semicon- The etchants hydrofluoriclnitric acids. to those a similar manner used other materials, and and ductor in As it is an extremely violent and reactive oxidizer, in comparison to others, H,02 it has a tendency dissociate rapidly once in solution with heavy oxygen bubble evolution, partic- to when room above ularly temperature. Because of this, such mixtures can become used depleted in the peroxide, such that the peroxide may rapidly be added only when ready for solution use, is stopped when complete dissociation in reached. There are always and use exceptions "age", then used some solutions are . allowed to sit and . . as a "stag- mixed, nant" solution. Potassium permanganate, KMnO,, and chromium trioxide, CrO,, or other chromium compounds, as sodium dichromate, such Na2Cr20,, etc.. are oxidizers and, when mixed with HF, are used as defecVdislocation etchants on many semiconductor materials. Several © 1991 by CRC Press LLC

407 CRC Etchants Handbook of Metal 394 have been and are discussed in the preceding section on solutions HF:Cr03 developed, and with varying halogen concentrations are HF:I, HF:Br, Chromium Containing Etchants. etchants and discussed in sections similar to that for chromium. defecVdislocation as used 30HF:50HN03:30HAc:0.6Br2 was originally developed a defect as (Camp #4) etch: CP4 wafers, figure germanium ingots and etch for (100) and used at and (LOF) light orientation It also is a polishing solution, room has been used on a number of other temperature. and and compounds as a removal, polish, thinning, cleaning or semiconductor, metals, step- room temperature, below room temperature, hot to boiling. Without bromine, it is etch at replaced CP4A the bromine has been modified, with I,, Cu(N02),, and, as CP4, called AgNO,, etc. The HF-type etches is presented to show the wide variety of metals of following list compounds to which solutions are applied. Many additional solutions are shown such and etchant section headings. their appropriate under Material Use Ref. Formula Removal conc. HF, Metallographic xHF:xH,O macro-etch Preferential A1 Removal & AIN cleaning AlSb Polish Polish AlSb & AlSb Oxide removal cleaning Removal HF, conc. Removal HF, conc. Dislocation HF:3HN03 I Damage, removal xHF:xH,O Preferential ml HF:15 ml HN03:45 ml HCl: 15 H,O ml 25 CaWO, Dislocation sat. sol. 1HF:20Cr03, Polish HF, conc. CdF2 CdSiAs, Polish 1HF:3HN03:3H20 CdTe Polish HNO, 1 1 HF: 2HF:3HN03: H20 1 CdTe Preferential CdTe Preferential 1H20 3HF:2H202: Preferential HF, conc. coo (diamond) D Cleaning HF, conc. Thinning Fe,C 1 HF:4HN0,:5H20 HF, GaAs conc. Selectivelremoval Cleaning vapor GaAs HF, Cleaning HF:9H20 GaAs 1 Polish GaAs 2HF:3HN03:2HC1 GaAs Cleaning 1 HAc 1 HNO,: 1 HF: Preferential 1 HF:3H202 GaAs 1 H20,:SOH20 Selectivelstep-etch IHF: GaAs GaAs Polish H,O,: 1 H,O 1 5HF: GaAs "superoxol" 1 HF: I H202:4H20 Preferential GaAs 1 HF: 1 Cleaning HNO, GaAs Polish, rapid 1 HF:3HN03:2H20 © 1991 by CRC Press LLC

408 Formula Material Use Ref. mg AgNO,: 1 ml GaAs ml H20:6 Preferential GAS-0059 HF:2 "AIB" 1 g ca3 Polish Gas 1OHAc b 1 HF:5HN03: GaSb Polish 1 HF: 1 HNO, Gap Polish 1 HF: HNO, I Ge Fracture: HF vs. air HF, conc. medium Preferential 1 HF:8H20 Preferential xHF:xHN0,:xHCI:xH202 Preferential 1HF-3HN0,: 12HAc "Dash Etch" Polishithinning 1 HF:3HN03:8HAc 1 HF: Preferential "superoxol' ' 1H202:4H20 30HF:50HN03:30HAc:0.6Br, CP4 Preferential polish ml ml HNO,:33 ml HF:30 15 Preferential I, mg HAc:80 HF: HNO, 1 1 Ge p-n etch junction 4HF:7HN0,:2H20 Ge cleaning Polish GeN HF, conc. Removal Removal OH20 GeN 1 HF: 1 Removal 1 HNO, HF: 1 GeAs Hf Cleaning 10 ml HF:45 ml HN03:45 ml H20 Hf Removal 1 HF: 1 H202:20H20 Preferential InAs H20,:4H20 "superoxol" HF: 1 1 Preferential InAs 5HAc:0.6Br2 74HF:75HN03: 1 InAs Preferential 1 ml HF:2 ml H20:8 mg 1 AgNO,: gCrO, AIB Etch removal Oxide HF, conc. InSb Polish InSb 10HF:25HN03:20HAc Polish InSb HF:5H202:xH20 I Preferential InSb ''superoxol' 1 1 ' H2O,:4H,O HF: Polish InSb CP4 30HF:50HN0,:30HAc:0.6Br2 Removal InSb 1 HF: 1 HN03 Preferential InSb HNO3:6H,O I 1HF: Dislocation InSb 1 HF: 1 H202:2H20 InP removal oxide Native 100H,O 8HF: Preferential ml H20:8 I ml HF:2 mg AgNO,: InP 1 g 03 Preferential InP OHBr I 1 HF: Dislocation InP I MeOH 5HF: Dislocation InP 1 Br, 5HF: LiF Dislocation ml HF: HN03: 100 ml 100 160 ml HAc: 2 ml Br, Preferential LiTaO, I HF:2HN03 Preferential HF:2HN03 1 LiNbO, Preferential xHF:xH20 MgO Removal xHF:xH202 Mo Removal xHF:xHNO, Mo Removal xHF:xMnO, Mo Polish Mo 3.5 ml HF:96 ml H2S04:0.5 ml HNO,:xCrO, © 1991 by CRC Press LLC

409 of Metal Etchunts CRC Handbook 396 Ref. Use Material Formula Cleaning NB HF, conc. Electropolish Nb HF, conc. Polish HF:4HN03 I Nb NbAlY Removal HF, conc. Cleaning 1 HF: HNO,: 1OHAc 1 Nb,Se Removal HF, conc. Nb3B3 Ni Removal vapor HF, PtSb, Preferential H202 1 1 HF: Preferential H20 1 PtSb, lHNO,: 1HF: PtSb, 3HF:5HN03:3HAc Preferential Preferential Re 8HF-2HN03 Sb Polish "Dash Etch" 12HAc lHF:3HN03: Sb Dislocation 1 HF:2HN03:24HAc: 1 Br, Si Junction stain HF, conc. + intense light Si Oxide removal HF, conc. Cleaning Si vapor HF, Si Cleaning 1 HF: 1 OH,O Preferential "Dash Etch" 1HF:3HN03: 12HAc Si Thinning 1HAc 1HF:5HN03: Si Si Polish HF;5HN03: HAc 1 1 Dislocation 1HF:3HNO3: 1 Si HAc CP4 10HF:50HN03:30HAc:0.6Br2 Polish/preferential Si Si Structure forming 1 5HN03:5HAc 2HF: Polish Si HF:3HN03 1 RemovaYpolish 1 HF: 1 HN03:50H20 Si Cleaning Si xHF:xMeOH Si Defect M CrO,:lH,O IHF:1.5 15 M "Secco" K2Cr20, Si 2HF:O. Preferentialldisloca- tion CrO,: Si .5H20 1 M 1 0.75 2HF: Preferentialldisloca- tion "Shimmel" Preferential/disloca- Si (33%) 1HF:3Cr03 "Sirtl" tion Polish 50 HF:50 ml HN03:100 mg ml KMnO, Junction stain 4HF:2Cu(N03), Preferential xHF:x12 MeOH HF:2 ml mg ml 12:20 10 Preferential Cleaninglslow polish "BHF" 1 HF:9NH4F(40%) 5 removal Oxidelnitride mlHF:20 mgNH4F:200 mlH,O "BHF" Electropolish, jet 30 gNaFI1 rnlHE8.4 Cleaning xHF:xH20 Cleaning HF, conc. 3HN0, 2HF: Removal 2HF: lCrO, (33%) "Sirtl" Polish sat. lHF:xKF, sol. Electrolytic, microstructure Polish removal 1 1 HF: H,O Cleaning, quartzware HF:3HN03 1 © 1991 by CRC Press LLC

410 Formula Material Use Ref. SiO,(Qtz) 1 Thinning, HNO, 1HF: QTZ-0006 alpha-quartz 1 Tuning, alpha-quartz HF:20HN03:20EG Polish, alpha-quartz ml g 50 NH4F.HF:100 HF:50 ml 50 ml Gly H,O: Patterninglpinholing SiO, conc. HF, Removallroughening SiO, vapor HF, Cleaningloxide SiO, 00H20 1 HF: 1 removal SiO, 1HF:2HN03:60H20 "P Etch" Removal SiO, 100NH4F, sat. sol. 1HF: "BHF" Removal SiO, Removal lHF:6NH4F (40%) "BHF" SiO, Step-etch ' "BHF' IHF: 15H20 10NH4F: SiO, Dislocation ml HF:9 g Cr0,: 100 200 ml H20 SiO, Removal "BOE" xHF:xNH,F:xH,O Si,N4 Removal vapor HF, Si,N4 RemovaYpinholing HF, conc. Si,N4 15HF: 10H3P04:60EOH Preferential 1 1 HF: Ta H,O Cleaning "CP4A" Ta 2HF:5HN03:3HAc Acid saw cutfpolish Ta 3HF:5HN03: Electropolish 1 HAc Ta H,O 1 HF:2HN03: 1 Removal (20%) NH4F 1 1 HF: Ta Preferential Ta 2HF:2HN03:5H2S04 Preferential .5HF:2HN03:5H2S04 1 Polish Ta HF:20H20 1 Cleaning TaSi, Tho, x%NH,F Preferential Ti I HF:4HN03:5H20 Removal HF:90 H,O ml 10 ml Ti Removal Ti Polish 3HF: 1 H,O 1 6H3P04: Removal Ti xHF:xHCl:xH,O 1 MeOH HF: 1 Ti Electropolish 1 HF: 1 Tic HN03:6H20 Electrolytic, preferential Tic Electropolish xHF:xHNO,:xHAc HF:45 H,O, ml HN03:45 ml ml 10 TiN Cleaning TIN Removal mH,O g NH4F:625 13HF:452 Removal TiO, 1 HF:24NH4F:5H20 Electrolytic, HNO,: 10H20 1 1 HF: v preferential Removal HF, conc. Polish 1HF: 1H202:4H20 "superoxol" Dislocation 5HF:4H20 1 HNO, ml HF: 100 ml 15 Cleaning HF, conc. Removal Removal 1HF: 1 H,O, Polish xHF:xHNO,:xH,O Cleaning 3HF:2HN03: HAc 1 Polish xHF:xHNO, Removal HF, conc. © 1991 by CRC Press LLC

411 398 CRC of Metal Etchants Handbook Material Use Formula Ref. Polish ZnS 1 HN03 1 HF: Preferential ZnS "Warekois" 1H20 3HF:2H,02: ZnSiP, Polish 1 HNO, 1 HF: Preferential ZnTe "Warekois" 3HF:2H20,: 1H20 Removal Zr 4HF:30HN03. then xH2S04 Electropolish zr 1HF:4HN03:2H,0 Removal Zr ml rnl H,O HN03:50 50 ml HF:50 Preferential, Zr HF:50 8 rnl HNO,:50 ml H,O ml macroetch Polish Zr xHF:xNH4F Cleaning ZrN ml 10 ml H,O, ml HN03:45 HF:45 Removal Zro HF, conc. BUFFERED HYDROFLUORIC ETCH NAME: ACID (BHF) a naturally occurring mineral, manmade obsidian, as well as a is both General: Glass as first developed soda-lime glass around 3500 B.C., and the same product since the Egyptians is still in use formula has been in use as a pottery glaze (ceramic pottery) since today. Glass those and the present glass industry is now a major industry of its own within ancient times, original silicate industries, which clay and ceramics also, today, as separate the include industries. Solid the semiconductor industry, in particular, In been using silicon dioxide, has State, in device fabrication since about 1950. The common term is "oxide", SiO, (glass, silica), still used with reference to silicon dioxide, only, although several other metallic oxides are in use in a similar manner, now as such A1,03, etc. This now also includes nitrides, TiO,, such as Si3N4, and oxynitrides nitride, oxides and nitrides form isomorphous series. as silicon oxides and nitrides are deposited as Such films in many types of device fabrication thin as a final surface passivation, or in processing as a mask against etching, metallization, or irradiation damage; and, when doped with boron, phosphorus, or arsenic, as a drive-in diffusion dopant doped oxides have acquired their own acronyms such as BSG, source. Such and PBSG. PSG, ASG, long (HF) has solution for etching glass. When any been Hydrofluoric acid the primary held it will liquid, if it is be in the hot is immersed in the glass etch polished; whereas vapors, will the surface rough frosted. HF is supplied commercially in a standard 49% or be in polyethylene bottles, as it attacks glass, and most processing laboratories Always solution. it from 5-gallon bottles. For general removal of thin use and nitrides, both film oxides concentrated water diluted hydrofluoric acid are used, but are too rapid for patterning and most thin films only on the order of 1500 to or controlled removal, as are A thick. In 3000 solutions etching pattern film, whether an oxide, nitride, or metal, all acid of will any thin etch down vertically through the film, as well as horizontally at an equal rate. This must be compensated for in fabricating fine-line patterns to prevent destructive undercutting of the metal structure. HF is too rapid buffered hydrofluoric acid solutions have been As for such fine control, many the of BHF which is applied to with HF developed general acronym fluorine + compound Such mixtures also have been referred to as a buffered oxide etch mixtures. (BOE), BHF is more commonly applied. but Because mixture variations the "BHF" term should of be accepted with caution, unless HF:H,O solutions have been referred to as BHF the even specific shown, as formulation is most widely used fluorine compound used to buffer is ammonium fluoride, solutions. The NH4F as HF:NH,F (40%), but others are used (KF, NaF), only, or in addition to NH,F. Also, the ammonium bifluoride (NH4F.HF) compound has been used. © 1991 by CRC Press LLC

412 The solutions limited to silicon dioxide, or silicon nitride, as they BHF of use is not metal list glassy covers several applications are applicable to any compound. The following etchant sections for further and metallic compounds. See the individual on other metals usage. Use Material Formula Ref. xHF:xH,O Al Removal 1 HF: ml H,O ml 199 A1 Macro-etch I HF: AIN 1 H,O OH,O 1 HF: or 1 Cleaninglremoval HF, conc. x% or BaF, NH4F Removal Bi 2HF:98H20 Damage removal xHF:xH,O CdF, Polish 1 HF:9H20 GaAs Cleaning N Ge KF 10-W.1 Electrolytic polish 1 GeN 1 HF: OH,O Removal 1 MeOH 5HF: InP Dislocation lOH,O 2HF: InP Native oxide removal xHF:xH,O Preferential MgO HF: 1 H,O 1 (Qtz) SiO, Removal 1 HF: 1 OH,O i S Cleaning 1 6H,O i S 1 HF: Native oxide removal xHF:xMeOH Si Cleaning 1 1 NH4F(40%) BHF HF(40%): Si Native removal oxide BHF 1HF:9NH4F(40%) Si oxide removal Native SiO, Controlled removal Si3N4 Controlled removal i S 2HF: 1 BHF 3NH4F Native oxide removal ml HF:20 g:NH4F:300 Si ml H,O 5 removal Native oxide BHF Controlled removal BHF xHF:xNH,F:xH,O Native oxide removal SI-0028 removal Controlled removal Controlled jet SI-0174b polish Electrolytic g NaFII HF:8,4 ml 30 SI-0041c Electrolytic polish (MeOH or glycols) xHF:xEOH oxide removal SI-0211 g NaF:96 ml HF:4.3 ml H,O Native 2 108 HF:350 ml g NH4F:1000 ml 1 1 SI-02 removal Controlled H2O removal SI-0220 oxide Native g NH4F.HF:100 HF:50 ml 50 ml H,O: ml Gly 50 SiO, removal Controlled Si,N4 removal Controlled Si,(ON)x Controlled removal Sic Cleaning SIC-0001 xHF:xH,O SIC-0005a Removal xBHF Sic 3b SIC-001 Electrolytic stain xHF:xKF, sat. sol. BHF Sic SiO SIO-0003 removal Controlled 1HF:20H20 Controlled removal SIO-0009 1HF:100NH4F, SiO, BHF sol. sat. Si2N4 Controlled removal Controlled removal 1 SIO-000 1 SiO, 1HF:6 NH4F(40%) BHF © 1991 by CRC Press LLC

413 400 CRC of Metal Etchants Handbook Material Use Formula Ref. BSG As above As above PSG above As BPSG SiO, Cleaning, Corning #7720 BOE xHF:xNH4F:xH20 Removal sol. NH4.HF, ml ml HF:200 sat. Controlled removal 15 above As above As Controlled removal ml NH4F:HF:100 g HF:50 ml 50 H,O: study 10 ml Gly As above Preferential NH,F(20%) 1 HF: 1 Cleaning 1 1 HF: H20 H,O gNH4F:100 ml 20 Polish Preferential x x%NH4F 1HF: 1 H,O Cleaning 1 HF: MeOH 1 Electrolytic polish Controlled removal 2HF:25NH4F:5H20 removal Controlled ml 134 ml HF:452 g NH4F:625 H2O As above Removal H,O I HF: 1 xHF:xNH4F Polish F, FLUORINE, May occur as a free element General: nature associated with volcanic eruptions, but in will immediately combine with other elements such as hydrogen or sulfur to form more stable compounds. In it is used as a corrosive gas in the study of metals and alloys for stability industry mixed chemical are chlorine and other as gases under various temperature against attack, Both drinking water and toothpastes are fluorinated as a medical conditions. against specific tooth decay. is rarely in Solid State processing, although Technical Application: The free gas used etchant as an additional etching assist element to include be bubbled it can a liquid through stining action. It has been grown as a single crystal under pressure and cryogenic conditions in vacuum study. for morphological pressure cryogenic conditions in vacuum. Etching: Vapor under ETCHANTS FLUORINE F-000 1 ETCH TIME: NAME: TYPE: Pressure, preferential TEMP: COMPOSITION: . .. . pressure x DISCUSSION: F2, as a gas can be grown as a single crystal under pressure and cryogenic conditions in in Vary vapor pressure to preferentially etch system. ingot. a vacuum REF: Schwentner, N et a1 - Rare Gas Solids, Vol 3, Academic Press, New York, 1960 © 1991 by CRC Press LLC

414 FRESONITE, Ba,Si,TiO, This mineral a minor occurrence near Fresno, California in the General: was found as than after is no sometime in industry, other 1950. There as a very minor ore of U.S. use titanium. The Technical Application: has been studied in Solid State development as a material piezoelectric similar possible to alpha-quartz. material Mixed Etching: of acids HF:HNO, FRESONITE ETCHANTS 1 FRE-000 TIME: ETCH NAME: TYPE: Acid, removal TEMP: COMPOSITION: HF ... x x ... HNO, DISCUSSION: single Ba,Si,TiO, material. Crystals are space group 4 mm2. Various concen- crystal trations of the acid mixture shown are done on (Ag,Ti),SiO,. The work recommended from have piezoelectric properties similar to those of alpha-quartz. crystals R L et a1 - J Appl Phys, 49,6025(1978) Richards, REF: © 1991 by CRC Press LLC

415 402 Handbook Metal Etchants CRC of Gd OF GADOLINIUM, PHYSICAL PROPERTIES Lanthanide Classification 64 Atomic number 157.25 Atomic weight 1312 Melting point ("C) 3000 ("C) Boiling point 7.89 (g/cm3) Density 0.021 Thermal conductance (cal/sec)(cm2)("C/cm) 0.07 1 heat Specific 25°C (callg) 3.70 (k-callg-atom) of Heat fusion 23.5 fusion Latent heat of (cal/g) 72 Heat vaporization of (k-caVg-atom) 19.9 (WID) Atomic volume 142 (K-callg-mole) 1st ionization energy 6.16 1st ionization potential (eV) 1.1 (Pauling's) Electronegativity 1.81 Covalent radius (angstroms) 0.62 (Gdf3) Ionic radius (angstroms) 131 (134) Electrical resistivity (micro ohms-cm) 25°C 2.56 Compressibility X (cm3/kg loe6) 46,000 Cross (barns) section 7.95 Magnetic moment (Bohr magnetons) 27,800 strength Tensile (psi) 25,100 Yield strength (psi) 356,000 Magnetic susceptibility ( X emulmole) 1260 Transformation temperature ("C) 4 thermal expansion Coefficient of linear 20°C cm/cm/"C) x ( 4 Hardness (Mohs - scratch) hcp prism, (10i0) normal) - Crystal structure (hexagonal Grey Color (solid) (basal) Cleavage (0001) GADOLINIUM, Gd occur as a native element. It is one of the Rare Earths and classified General: Does not BeOFeY,Si,O,,, which is the in gadolinite, sub-group. The primary mineral is yttrium of many of in and contains small quantities variable the rare earth elements: Ce, formula, La, Gd, Cs, etc. Also found in cerium earth minerals of which there are over 50 as silicates and phosphates. Monazite, being phosphate commercially mined (Ce,La,Di)PO,, a major from monazite sands. major use in industrial metal processing due to limited quantities, occasionally No used as element in irons and a doping in solder alloys; and the rare earth oxides are used steels; as coloring agents in glass and enamel. It has Technical Application: use in Solid State processing to date. major been used No as a constituent in some artificial garnets. Gadolinium has been grown as a single crystal in a study of growth methods, defects, and along with other rare earth elements. structure, Etching: Acids. Air conversion to oxide. © 1991 by CRC Press LLC

416 GADOLINIUM ETCHANTS GD-0001 NAME: Heat ETCH TIME: 1000°C 800- TEMP: TYPE: Thermal, preferential COMPOSITION: . heat x . . . DISCUSSION: a method of growing Rare Earth elements as single crystal specimens. Describes Gd, done to develop single crystals. Thermal annealing low angle grain boundaries, was defects, structure. Other elements were dysprosium, holmium, terbium, erbium, thulium, and grown and yttrium. Phys, - J Appl 34,3323(1963) Nigh, H E REF: GADOLINIUM NITRIDE ETCHANTS GDN-0001 NAME: Nitric acid TIME: ETCH Acid, TYPE: removal TEMP: COMPOSITION: . . . HNO, x . DISCUSSION: from alloy arc melted GdN,, in tantalum sheet and specimens formed buttons. Wrap 3-9 weeks at anneal and 2 x lo-' Torr vacuum. Forms in the Cubic Laves 600-900°C A study Rare Earth (RE) nitrides. Other nitrides formed were La, Nd, Sm, Tb, structure. of Y, atm argon and Ce. The SmN,, was formed in a silica capsule under 0.5 Pr, Er, Dy, Ho, to prevent used in a thermal expansion study. Sm evaporation. Nitrides were REF: Ibarra, a1 - J Phys Chem et 45,789(1984) M R Solids, ETCHANTS GADOLINIUM TERBIUM IRON 1 CDTF-000 TIME: NAME: Nitric acid ETCH TEMP: Acid, removal TYPE: COMPOSITION: 1 . . . . HNO, 1 ... H,O DISCUSSION: GdTbFe thin films co-sputtered on inch square glass plates with 10-20 rpm holder rotation during metallization, and films were amorphous structure. Iron for other etchants. See A similar rotation method is used (Note: of chromium for chrome glass for evaporation masks used in photolithographic processing.) REF: Taki, J - J Appl Phys, 55,2799(1984) PHYSICAL GALLIUM, Ga OF PROPERTIES Metal Classification 3 1 Atomic number 69.72 Atomic weight 29.78 Melting point ("C) 2403 ("C) Boiling point © 1991 by CRC Press LLC

417 CRC of Metal Etchants Handbook 404 (g/cm3) Density (cal/sec)(cm2)("C/cm) Thermal conductance 25°C (callg) heat Specific (caltg) of Heat fusion Heat of vaporization (callg) Atomic volume (WID) (K-callg-mole) 1st ionization energy (eV) 1st ionization potential (Pauling's) Electronegativity Covalent (angstroms) radius Ionic radius (angstroms) mrnHg "C) Vapor pressure (760 20°C ( of Cubic coefficient X expansion expansion linear thermal Coefficient of x 10- cm/cm/"C) ( 53.4 Electrical resistivity (micro-ohms-cm) 0°C 3.96 (eV) function Electron work 3 .O Cross section (barns) 1.5-2.5 - scratch) Hardness (Mohs rhomb (10il) - rhombohedral) Crystal structure (hexagonal Greylblack (solid) Color (ioii) poor) - (rhombic Cleavage Ga GALLIUM, not occur as a native element. It is a rare element found as Does General: a trace always other sulfides, and almost ZnS, in bauxite, essentially AI,O,. constituent in sphalerite, 2H,O, an admixture with clays. It is part as the aluminum family of elements - Al, Ga, of TI as the reaction - its salts resembles those of aluminum. Besides mercury, cesium, of In, rubidium, gallium is the only metal that can be liquefied at or near room temperature and high purity m.p. = 29.78"C vs. RT = 22.2"C). Because of this low melting point, (Ga gallium used in the Solid and electronic fields is usually stored under refrigeration. State industrial use is as a temperature solder, as pure gallium or alloyed with A primary low 1600°C, it is used as it is liquid As to room temperature from near lead, zinc, silver, etc. filler in high temperature thermometers. liquid the Application: Both gallium and indium were two of the first p-type dopants Technical the initial development used in germanium as a semiconductor, and gallium is a major of GaSb; gallium several compound semiconductors, as gallium antimonide, constituent in such GaP and gallium arsenide, GaAs. semiconductor has been the major Silicon phosphide, mid-1950s, but gallium arsenide devices have become increasingly im- material since the portant since about the mid-1960s when they first appeared as a viable product. Pure gallium its alloys are used in Solid State and electronics as solders in fabricating and gallium as been indium solders. Both have and indium are used as paste smear assemblies, contacts on molybdenum discs to mount and hold wafers during molecular beam epitaxy (MBE) of specimens for microscope study. or as a general holder References here do not include single crystal gallium, though it can be so grown under vacuum cryogenic conditions like gases. Etching: Soluble in acids, alkalies, and mixed acids. Clean with alcohols. © 1991 by CRC Press LLC

418 GALLIUM ETCHANTS b GA-0001 ETCH NAME: Methyl alcohol TIME: 0 to 8OC TEMP: TYPE: Alcohol, cleaning COMPOSITION: ... MeOH *x Chill with LN, * DISCUSSION: solid material. Because of the low melting point of gallium, Ga stored as it is usually temperature a refrigerator in sealed ampoules so it will not adsorb contaminating at cold in order In it readily adsorbs oxygen. In state to desorb oxygen from gallium, gases. the liquid the place in methyl alcohol chilled with liquid nitrogen, LN,, at or below the gallium temperatures shown. Ibid. REF: GA-0001a Hydrochloric TIME: ETCH NAME: acid TEMP: TYPE: Acid, cleaning COMPOSITION: ... HCl, conc. x DISCUSSION: solid material. Concentrated hydrochloric acid Ga as to clean gallium before was used mixing with The zinc. LPE mixture used as a molten Ga/Zn in was growth of zinc flux ZnSe. selenide, REF: Fujitz, S et al - J Appl Phys, 50,1079(1979) GA-0002 ETCH regia TIME: 3 min NAME: Aqua 10°C Acid, preferential TYPE: TEMP: COMPOSITION: ... HCI 3 ... HNO, I DISCUSSION: specimens were used in a study of Ga transition. Samples were hot superconducting wire and etched in the solution cut to develop grain boundaries. Zinc hemispheres shown also studied. 121,1688(1961) Rev, J F & Mapother, D E - Phys Cochran, REF: GA-0003 ETCH NAME: TIME: Potassium hydroxide TYPE: Alkali, removal TEMP: COMPOSITION: . . . x x% KOH (NaOH) . DISCUSSION: Ga, as a constituent in single crystal GaAs p-type wafers fabricated as light emitting As or Au dot contact pads. Where A1 is removed with HNO,; Ga is removed diodes with with alkalies. Diodes studied for the effects of chemical surface treatment and annealing on © 1991 by CRC Press LLC

419 406 CRC of Metal Etchants Handbook reduce light emission. Strong acids basic solutions are good and 350°C or eliminate emission; Ga(OH), and Ga,O,. 5 min Alkalies also remove N,, increases efficiency. in & Hartnagel, H L - REF: Vac Sci Technol, 19(3),427(1961) Adachi, R J OF GALLIUM ANTIMONIDE, GaSb PHYSICAL PROPERTIES Antimonide Classification 51 & 31 Atomic numbers 191.5 Atomic weight 712 Melting point ("C) Boiling point ("C) 5.60 (g/cm3) Density 6.09 Lattice constant (angstroms) 0.74 Energy (eV) gap 3.34 index (n = ) Refractive 6-7 scratch) - Hardness (Mohs 1 1) tetrahedron (1 tetrahedral) - Crystal structure (isometric Silver-grey Color (solid) (dodecahedral) Cleavage (1 10) GALLIUM ANTIMONIDE, GaSb Does not occur as a natural compound, though antimony does occur as a native General: in quantities, and forms many minerals such as allemontite, element minor SbAs,, and Sb,S,. The latter is of greater importance as an ore, and there are several other stibnite, antimonates. There is industrial use of the no compound. Technical Application: Gallium antimonide is a 111-V compound semiconductor with the sphalerite, structure. It is a (1 11) with (1 1 1)Ga and (m)~b ZnS surface polar compound different etching characteristics, such it is usually showing processed as a (100) surfaces that like similar polar compounds. Single crystal ingots have been grown by the oriented wafer Bridgman Horizontal and the Float Zone (FZ) methods. Thin film (HB); Czochralski (CZ); epitaxy has been by Vapor Transport (VT) and Chemical Vapor Deposition (CVD). growth has been grown as a trinary compound with arsenic, aluminum or indium. Both the It also binary and trinary materials as wafers or thin films have been fabricated as diodes, transistors, laser diodes, or and photo cathodes. electroluminescent diodes Water, Etching: HNO,, halogens and mixed acids of HF:HNO,, HCl:HNO,. HCl, ANTIMONIDE ETCHANTS GALLIUM GASB-0001a Hydrochloric acid TIME: ETCH NAME: Hot TEMP: (80°C) TYPE: Acid, removal COMPOSITION: x HCl, conc. ... DISCUSSION: GaSB, (1 11) and (100) wafers used in a development etch study. When used hot, solution will with moderate to vigorous reaction. attack gallium antimonide 107,108(1960) Soc, & Schwartz, B - J Electrochem Robbins, H REF: © 1991 by CRC Press LLC

420 GASB-0001 b TIME: ETCH NAME: Nitric acid TEMP: RT Acid, removal TYPE: COMPOSITION: (2) 2 . ... HNO, ... HNO,, conc. (1) x H20 ... 1 DISCUSSION: used GaSb, a development etch study. There are three com- (1 11) and (100) wafers in of nitric acid: standard, 70%, sometimes called "white" fuming; mercial concentrations "yellow" and 74%, "red" fuming; All three concentrations were evaluated 72%, fuming. dilute solution shown. In all cases, solutions showed moderate in addition to the vigorous to reaction. Ibid. REF: - GASB-0005 TIME: min 1-5 ETCH NAME: TYPE: Acid, polish TEMP: RT COMPOSITION: HF ... 1 9 ... HNO, DISCUSSION: (100) undoped wafers GaSb, in a study of surface oxidation. Surfaces were etch used polished this solution before oxidation. Oxidation was in in at 300 and 400°C for 1 or air at up build G+O,lGaSb structure. Little or no Sb appears in the oxide but does a for 2 h Ga,O,/GaSb interface. the J L et a1 23,1534(1985) Jpn S Appl Phys, - REF: Harmon, Fuller, C S & Allison, H W - J Electrochem Soc, 109,880(1962) GASB-0009a: GaSb, (1 1 wafers. Solution described as a general polish etch. 1) GASB-0001~ ETCH NAME: TIME: Acid, removal TEMP: RT TYPE: COMPOSITION: 2 ... HCI (2) 1 ... HCI (1) 1 ... HNO, DISCUSSION: and (100) wafers. Etch reaction is shown to be moderate to vigorous with l), GaSb, (1 1 etchants for GaSb. in a development study of both formulations. Used Ibid. REF: GASB-0000d ETCH NAME: TIME: TYPE: Acid, removal TEMP: Hot COMPOSITION: 1 . . . . H202 (30%) . . . NaOH (20%) . 1 DISCUSSION: development study a 1 1) and (100) wafers. A moderate etch reaction. Used in (1 GaSb, of etchants for GaSb. REF: Ibid. © 1991 by CRC Press LLC

421 CRC of Metal Etchants Handbook 408 GASB -0002 sec ETCH NAME: 20 TIME: polish TYPE: TEMP: Acid, RT COMPOSITION: (2) Rinse: hot (3) HOLD: under HCl l...HF HC1, (1) . . 5 . . HNO, HAc ... 10 DISCUSSION: AlGaSb thin GaSb, as substrates for epitaxy growth of (1 11) and (100) wafers used pm diamond paste before polish were polished with 0.25 films. Substrates mechanically HCl, and the acid wet with were placed in vacuum system still etching. Wafers the epitaxy in of H, for several hours 300°C situ atmosphere with heat at an boil to allowed was off in prior to deposition AlGaSb. cleaning of D 3,489(1984) a1 - J Cryst Growth Nenow, REF: et et a1 - J Cryst Growth, 3,439(1984) Wada T GASB-0003: (Ill), and GaSb, Used this solution formulation as a general polishing (100) wafers. etch. GASB-0004a ETCH Water TIME: NAME: TYPE: Acid, removal TEMP: COMPOSITION: ... x H,O DISCUSSION: GaSb, (100) undoped wafers used as substrates for MBE growth of GaSbJGaSb. A study of substrate surface preparation different etching mixtures. Substrates were first lapped with surface was Sic a pad, then with 0.3 pm alumina. Water polishing of on used powder with laptpolish damage remaining before polish etching. to remove 132,659(1985) M et a1 - J Electrochem Soc, Kodama, REF: GASB-0004b NAME: TIME: ETCH Acid, TEMP: polish TYPE: COMPOSITION: ... HF 2 ... HNO, 18 CH,COOH (HAc) . . . . 40 DISCUSSION: GaSbtGaSb. See GaSb, (100) undoped used as substrates for MBE growth of wafers GASB-0004a. The base etch shown above was followed by: (1) hot HCl, 10 min; (2) 2% Br,:MeOH, RT, min; (3) 1HNO3:30HC1, at 5"C, 1 min. After etching, the wafers were 1 in annealed MBE vacuum system using REED at 20 KeV prior to epitaxy growth GaSb/ an Prior to etching, after water polish substrates were degreased in TCE, then acetone, GaSb. then MeOH. After etching, rinse in MeOH and spin dry. GASB-0004~ BRM ETCH TIME: TIME: 2 min TEMP: RT polish Acid, TYPE: COMPOSITION: Br, x ... . 2% MeOH . . . . x © 1991 by CRC Press LLC

422 DISCUSSION: GASB-0004a and GASB- both GaSb, as substrates. See (100) undoped wafers used 0004b, Used substrate surfaces. to etch above, for details. polish Ibid. REF: Ibid. GASB-0009b: (1 11) wafers. Solutions between GaSb, used as general chemlmech polish 1-20% Br, etchants. GASB-0006a ETCH TIME: 20 sec + 10 sec NAME: BRM polish TEMP: RT TYPE: Halogen, COMPOSITION: ... x Br, 0.05% x . . . . MeOH DISCUSSION: (1 p-GaSb, used in a surface cleaning study, as follows: use lens paper 11) wafers solution as pad with a lapping saturated for 20 sec - then dilute with MeOH - lap - continue lapping for 10 sec. Rinse in the solution shown and rinse in water. Authors then With that of bromine is not critical. (Note: percentage the bromine concentration shown, state Gap, GaAs, InP, surface study also included Si, Ge, percentage would not be critical.) This and InSb. InAs Aspenes, D E Studna, A A - J Vac Sci Technol, 20,488(1982) REF: & e GASB-0001 ETCH NAME: TIME: TYPE: Acid, removal TEMP: Hot COMPOSITION: ... HF 1 ... 1 HNO, DISCUSSION: GaSb, (1 11) and (100) wafers. Solution gives moderate to vigorous reaction. REF: Ibid. GASB-0007a ETCH TIME: NAME: TYPE: Acid, passivating TEMP: RT COMPOSITION: x ... HCI DISCUSSION: (lo), undoped and Te-doped wafers used in a cleaning study before MBE both GaSb, rpm 3500 to passivate surfaces after acid etching. thin Spin-on HCI at film deposition. 23,1657(1984) Phys, Appl al - Jpn J M et Kodama, REF: GASB-0007b 1 min TIME: NAME: ETCH TEMP: 5°C TYPE: Acid, removal COMPOSITION: HNO, 1 ... HCI ... 30 © 1991 by CRC Press LLC

423 CRC of Metal Etchants Handbook 410 DISCUSSION: (loo), and Te-doped wafers used in a cleaning study before MBE thin undoped GaSb, 0, contamination surfaces. Passivate surfaces with fmm removed film deposition. This etch (GASB-0007a). HC1 Ibid. REF: GASB-0007~ TIME: 40 sec ETCH NAME: Acid, polish RT TYPE: TEMP: COMPOSITION: 2 ... HF HNO, ... 18 ... HAc 40 DISCUSSION: (100) un-doped and Te-doped wafers used in a cleaning study before MBE thin GaSb, film solution leaves a high deposition. This content surface. Follow with 1HNO3:30HCl 0, on (GASB-0007b), reduces 0, content and leaves a highly reflective surface. Passivate which (GASB-0007a). HCl surface with Ibid. REF: GASB-0008a 20 TIME: sec NAME: BRM ETCH TYPE: Halogen, preferential TEMP: COMPOSITION: 1 ... Br2 ... . 10 MeOH DISCUSSION: (1 11) wafers. solution of bromine-methanol (BRM) GaSb, shallow etch This developed on the pits (1 1 l)A surface. - McGraw-Hill, Handbook of Materials and Processes for Electronics, REF: Harper, C A York, 1970, New 7 GASB-0008b NAME: TIME: ETCH min 1 TYPE: Acid, preferential TEMP: COMPOSITION: 1 rnl ... HCl 1 H202 ... m1 2 ml ... H20 DISCUSSION: GaSb, 11) wafers. The solution develops etch figures. (1 Ibid. REF: GASB-0010 sec TIME: 15 NAME: ETCH RT TEMP: polishlpreferential TYPE: Acid, COMPOSITION: HF ... 1 . . . HN03 . 2 HAc 1 ... © 1991 by CRC Press LLC

424 DISCUSSION: GaSb, I I) wafers other orientations. Solution used as a rapid polish etch and will (1 and develop etch pits. REF: Gatos, H C - J & Soc, 107,427(1960) M C Lavine, Electrochem GASB-OO1 1 TIME: ETCH NAME: TYPE: RT TEMP: Acid, preferential COMPOSITION: ... 1 HF . .. 1 . HNO, ... H20 1 DISCUSSION: (1 1 1) wafers. Solution used to polish faces. (m)~b GaSb, Faust, REF: & Sager, A - J Appl Phys, 3 1,33 l(1960) J W GASB-0012 TIME: ETCH NAME: TEMP: TYPE: Acid, selective 50°C RATE: 10 hsec COMPOSITION: 1 . . H,O, .. 10 . . citric acid (50%) . . [(COOH)CH2C(OH)(COOH)CH,COOH] DISCUSSION: (loo), p-type wafers with surfaces patterned by photolithography. Solution used GaSb, other and to form mesas used be the material surface and can in pits etch selectively to also structures. etched REF: Otsubo, M et J 123,676(1976) Soc, - al Electrochem GASB-OO 13 ETCH NAME: TIME: Acid, selective TEMP: TYPE: COMPOSITION: 3 HF ... 5 ... HNO, 3 ... HAc DISCUSSION: (1 11) wafers GaSb, as substrates for growth of heterojunctions as: GaInIGaInSbl used GaSb(ll1). After MBE growth wafers were cleaved (I 10) and the solution used to develop deposited layer structure. Mroczkowski, REF: et al - J S Soc, 1 17,750(1968) K Electrochem GASB-0014a TIME: 1 ETCH NAME: min Acid, polish TEMP: TYPE: RT COMPOSITION: 1 ... HF HNO, ... 19 . . . . CH,COOH (HAc) 30 DISCUSSION: GaSb, (100) wafers within 0.2" of the crystal plane used as substrates for LPE growth orientation. Substrates Growth habit is sensitive to AlGaSb. were cleaned as follows: (1) of © 1991 by CRC Press LLC

425 CRC of Metal Etchants Handbook 412 with organic solvents; (2) etch solution shown; (3) quench in 18 Ma DI water degrease in MeOH and prior to epitaxy growth: (1) bake at wash. Under (4) vacuum, up to 24 700°C at 550°C, 1 h; (3) melt-back, 10-15 sec, 10°C above growth temperature, h; (2) at heat clean h soak prior to melt back with with etch solution leaves an oxide on a 1-2 gallium. The surface exposure to air will oxidize surfaces. Surfaces were studied by the substrate and in at 6 profiling AES vacuum Sputter etching Torr. argon was done at 1 kV x with 5 x lo-' under vacuum. In profiling, substrates were: (1) cleaved (1 10); (2) etched Torr 400°C; (4) 1 h, at rinsed; (3) then thermal cycled 1 h, at in shown and DI water solution 400°C. (Note: Excellent article on growth temperatures and and melt-back at (5) Ga 550°C; AlGaSb surfaces.) of morphology REF: Takeda, Y et - J Electron Muter, 13,855(1984) a1 GASB-0014b ETCH Hydrochloric acid TIME: x min NAME: TEMP: RT removal TYPE: Acid, oxide COMPOSITION: ... HCI, conc. x DISCUSSION: of (100) as substrates for LPE growth GaSb, AIGaSb. Solution used to wafers used remove oxide from previous etching or exposure to air. Soak wafers in HCl, then blow off rinse - - HCI soak, then MeOH or and nitrogen blow dry. Both methods with acid nitrogen GASB-0014a. effective for removing are oxides. See Ibid. REF: - -- GASB-0014~ TIME: ETCH NAME: A-B etch, dilute Acid, stain TYPE: RT TEMP: COMPOSITION: ... Etch A-B 1 10 ... H20 DISCUSSION: (100) wafers Te-doped and used as substrates GaSb, LPE growth of AIGaSb. After for epitaxy deposition, wafers were cleaved (1 10) and stained in the solution shown to develop AlGaSbIGaSb interface and defect structures in the thin film layer. (Note: The A-B solution A/B. The A-B shown Buiocchi preferential etch normally shown as is Abrahams and the is sometimes Puotinen for the Kern and designation used RCA - etch.) REF: Ibid. Abrahams M S & GASB-0017: J - J Appl Phys, 36,2855(1965) Buiocchi, C Reference for A-B Etch shown in GASB-0014~ (See GAS-0059). Solution mixture is H20:1 g Cr0,:8 g AgNO,. ml HF:2 1 ml GASB-0015a ETCH NAME: min TIME: 1 Acid, preferential TYPE: RT TEMP: COMPOSITION: HF ... 1 9 HNO, ... ... HAc 20 © 1991 by CRC Press LLC

426 DISCUSSION: (1 wafers used in a study 11) growth striations. Mechanically polish surfaces of GaSb, development with shown. See before structure solution (21 1) ori- GASB-0015b for wafer use. entation Tohno, S-I REF: J & Soc, 128,1614(1981) Katsui, A - Electrochem GASB-0015b 1-2 TIME: ETCH NAME: min TEMP: RT TYPE: Acid, preferential COMPOSITION: ... KMnO, 1 0.05 ... HF 20 ... HAc DISCUSSION: develop 1) wafer orientation. Solution used to striations. growth GaSb, (21 Ibid. REF: GASB-0016 ETCH NAME: TIME: TYPE: Acid, preferential TEMP: COMPOSITION: (A) 40 HF (B) 4 ml ... Cu,03 (C) 1 ... A ... g 3 g AgNO, 40 ml ... H,O I ... B ... 40 H,O ... DISCUSSION: GaAISb. Mix GaSb, (100) wafers cleaved and used substrates for epitaxy growth of as solution "C" when use as a preferential etchant on the epitaxy layer. Intrinsic ready for p-type; Te dopant n-type. GaSb material is for REF: P et al Merbarki, J Cryst Growth, 61,636(1983) - PROPERTIES OF GALLIUM ARSENIDE, GaAs PHYSICAL Arsenide Classification & 33 31 Atomic numbers 145 weight Atomic 1260 (1230) ("C) Melting point point Boiling ("C) (g/cm3) Density Thermal conductance 300°F (W/cm/"C) linear thermal expansion Coefficient of 6] [LIL T("C - ') x 10 - 0.35 Specific heat (J/gI0C) 5.654 (5.63) Lattice constant (angstroms) 10.9 ) = Dielectric constant (e 1 ("C) Vapor pressure 1050°C 3.53 index (n Refractive = ) 600-800 Formation temperature ("C) 1.35 gap band Energy (eV) 6-7 Hardness (Mohs scratch) - (100) cube, fcc - normal) (isometric Crystal structure © 1991 by CRC Press LLC

427 414 CRC of Metal Etchants Handbook Color (solid) Cleavage (cubic) GALLIUM ARSENIDE, GaAs Does as a natural compound, although there are several other metallic not General: occur nickel and whose minerals may contain sulfur iron, copper, cobalt, platinum arsenides of of gallium arsenide as as a compound well as arsenic. The only industrial application is semiconductor. is a Technical Application: Gallium arsenide 111-V compound semiconductor with the structure, even though it is referred to as cubic, ZnS It is a (1 11) surface fcc. sphalerite, 11)Ga and (111)~s showing different etching characteristics, such polar with (1 compound processed in (100) orientation as are other such polar compounds. it is usually wafer that and silicon Germanium - were first developed - the two elemental semiconductors 1940s, and gallium arsenide was one of the first compound semiconductors in the late in the mid-1950s. It was initially grown by the Horizontal Bridgman (HB) method. developed It is still so grown, but much (now up to larger wafers diameter) are available as Czochralski 8" ingots. (CZ) film it is grown by horizontal or vertical thin to include OMCVD, epitaxy As an CVD, MBE. by or gallium arsenide Development been much slower than that of silicon, which is of has the major semiconductor that developed the present electronic industry as it is known still more brittle than today. The compound semiconductors, as a group, are either germanium or silicon, problematical in handling and, though gallium arsenide has better high more characteristics than the elemental semiconductors, the control doping to obtain frequency of . . . both problem factor, as was temperature control operational devices was an initial gallium and arsenic can vaporize from the solid compound during processing and, . . . in was far more emphasis on silicon technology addition, there through the late up 1960s. With development of the Schottky Barrier type devices, gallium arsenide has been - fabricated with a gate, source, and drain configuration as a field effect transistor (FET) base wafer semi-insulating (SI) -doped chromium, and the active gold or aluminum the with compound/metal material for such devices are shown here as interface. The the gate at GaAs:Cr, (100 (SI) wafers. now fabricated as low noise or power FETS: the LN-FET or P-FET, are Devices extended to other compound semiconductors, such been respectively. This technology has an as InP:Fe, (100) (SI) wafer. today, with the development of molecular beam epitaxy And multilayered under device development as the (MBE), structures are heterojunction or het- which include different epitaxy layered elements erostructure devices, compounds, plus or GaAs, the devices fabricated of Some etc. metals grown of substrates on oxides, nitrides, trinary compounds FETs, Gunn and IMPATT diodes, thyristors, rectifiers, and GaAs:Al are are developed as solar cells with up to 30% efficiency, as compared to silicon with being evaluation. trinary compounds with phosphorus and indium are under about only 18%. Other arsenide in Gallium single crystal ingot form and used, directly, as a device; is grown as deposited or polycrystalline thin film; or used as a substrate for other a single crystal epitaxy growth in device fabrication. This latter use, as a chromium-doped semi-insulating substrate, is probably the used wafer form for current device processing, although most widely is much of there the on-going development trinary material for an improved solar AlGaAs cell. Etching: Mixed acids HF:HNO, + HCl or H,O,. Alkali + halogen; halogens, molten fluxes. Gases as DCE and thermal etching. © 1991 by CRC Press LLC

428 SELECTION GUIDE: GaAs Br,:MeOH (BRM) (1) 32 (i) Oxide Removal: GAS-01 -0184a; -0005a; -0012a; -0013a; -0004a; Polish: -0200; -0006; GAS-0001a; (ii) ; -0202; -0010 -001 1 -0007a; Preferential: GAS-0002; -0173b (iii) (iv) Selective: GAS-0009 GAS-0004a; -0008 (v) Thinning: (2) Br2:EOH (i) Polish: GAS-0015 GAS-001 3 (ii) Preferential: 1,:MeOH (3) Polish: GAS-0015 (i) (4) NH,OH:H,O, Polish: GAS-0007c; (i) -0006b Selective: GAS-0018; -0023; -0025 (ii) (iii) Staining: GAS-0022 NH,0H:H20,:H20 (5) Oxidation: GAS-01 8 1 (i) GAS-0007c; -0006b Polish: (ii) (iii) Removal: GAS-0001 b (iv) Step-etch: GAS-0022 Junction: GAS-002 1 (v) HCI, conc. (6) Cleaning: GAS-0028; -0207; -0029; -0018b; -01 18; -0199 (i) (ii) 92 Preferential: GAS-01 (iii) Oxide Removal: GAS-01 14 (iv) Removal: GAS-0182b; -0140 (7) HCI, vapor Oxide Removal: (i) GAS-0074 (8) HCl:H20 GAS-0004a; -0 1 17 Cleaning: (i) (ii) -0030 Removal: GAS-0001c; HC1:EOH (9) Oxide removal: (i) GAS-0001d (10) HCI:FeCI, Preferential: GAS-0 174 (i) 1) HCI:HNO, (1 Dislocation: GAS-01 89 -01 86; (i) (ii) Junction: GAS-0056b GAS-0056a; -0179 Polish: (iii) 140c; -01 97 GAS-0190; -0 Removal: (iv) (12) HCl:HNO,:H,O Preferential: GAS-0167c; -0052; -0144a 0044~; (i) Polish: GAS-0057; -0148; -0176; -0178 (ii) (iii) Junction: GAS-0056a (13) HCI:HNO,:Glycerin Polish: GAS-0050; -0006e; -005 1 (i) (14) HCl:H,0,:H20 (i) Polish: GAS-0104; -0141 (ii) Removal: GAS-01 86 (iii) Structure: GAS-0060 © 1991 by CRC Press LLC

429 CRC of Metal Etchants Handbook 416 H20 & (15) H20:02 Oxidation: GAS-0001e; -01 8 1 (i) (Clorox) NaOC1 (16) Polish: -0195a GAS-0012b; -01 13; -01 14; -0184; (i) GAS-0 173a Preferential: (ii) HCI:HAc:K,Cr,O, (17) (i) Polish: GAS-0041 (18) HF, conc. 1 Oxide GAS-0 19 removal: (i) (ii) Selective: GAS-0024 vapor (19) HF, (i) Cleaning: GAS-0129 HF:H,O (20) (i) Cleaning: GAS-01 12 HF:HNO, (21) GAS-0047b (i) Cleaning: GAS-0140d Removal: (ii) HF:HN0,:H20 (22) Cleaning: GAS-0047a (i) Polish: GAS-0044~; -0006d; -0046; -0045b; la -0147; -021 -0146b; (ii) Preferential: -0146e; -01 77 GAS-0146d; (iii) (iv) Staining: GAS-021 la HF:HCI:HNO, (23) Polish: GAS-0055; -0145a (i) (24) HF:HNO,:HAc (i) Cleaning: GAS-0038b (25) HF:HNO,:AgNO,: H,O + Preferential: GAS-0146~; -0048; -01 19b (i) HF:H202 (26) GAS-0049; -0053a; -0144d (i) Preferential: HF:H202:H20 (27) (i) Junction: GAS-02 12b Polish: GAS-0053b (ii) Preferential: -0044f; -0168; -0144e-f; -01 57; -0 167a; -0146f; GAS-0045d; (iii) -0144b (iv) Structure: GAS-0054; -0160 HF:H202:H2S0, (28) (i) Polish: GAS-0088 (ii) Thinning: GAS-0088 HF:CrO,:H,O (29) Dislocation: GAS-0192 (i) (30) HNO,, conc. (i) Oxidation: GAS-0139 Removal: GAS-0140b (ii) (iii) Staining: GAS-0042 (3 1) HNO,:H,O (i) Junction: GAS-01 80 GAS-0145b Polish: (ii) GAS-0043; -0044b; -0183b; -0044a; -0045a; -0120; -0146a Preferential: (iii) (iv) Removal: GAS-0140b (32) HN0,:Tartaric acid (i) Preferential: GAS-0167b © 1991 by CRC Press LLC

430 (33) HN03:H20:AgN03 Preferential: GAS-0045c (i) H3P04:HN03 (34) lOa Polish: GAS-01 (i) (35) H3P04:H202:H20 Selective: GAS-0108a (i) Removal: GAS-0105; -0106 (ii) Thinning: (iii) GAS-0108b (iv) Via-hole: GAS-0109 H3P04:H202:MeOH (36) Polish: lob (i) GAS-01 GAS-0096b Selective: (ii) H3P04:H202:H2S04 (37) GAS-0004d; (i) 10c Dislocation: -01 Vacuum (38) Cleaning: GAS-0156 (i) Ar (39) Argon, Cleaning: GAS-0184 (i) 86b (ii) Thinning: GAS-01 + H2S04:H,0: 0, (40) (i) Cleaning: GAS-0149 1 Oxidation: GAS-018 (ii) (iii) Polish: GAS-01 87b (41 H2S04:Polypropaline ) glycol Dislocation: 21 (i) GAS-01 (42) H2S04:H,02 Cleaning: GAS-0150; -0194 (i) Removal: GAS-01 50 (ii) H2S04:H202:H20 (43) -0200; Cleaning: GAS-0066; -0069; -0074; -01 3 1 ; -01 98; -019 la; -0195b; (i) -0077; -0082; -0083; -0084; -0085; -0086; -0087; -0091; -0088; -0081; -0103; -0125; -0128; -0098; -0099; -0100; -0102; -015 -0152; -0153; 1; -0182a -0154; -0155; -0171; -0172; -0165; -0170; Oxide removal: GAS-01 14 (ii) -0193b Junction: GAS-0099; -0169; (iii) Polish: -0063; -0065; -0069; -0070; -0073; -0075; -0130; GAS-0062; -0056b; (iv) -0007h; -0077; -0089; -0091; -0101; -0182a; -0158; -0159; -0160; -0079; -02 12a 16; -0164 Preferential: GAS-0064; -01 (v) 2c 26; -021 Removal: GAS-0068; -0070; -01 (vi) GAS-0063a,b-m; -0078 -0072; -0076; (vii) Selective: -0006g; -0090 GAS-0067; -0089; (viii) Step-etch: (ix) Thinning: GAS-0090 (44) 12:KI:H20 (i) Selective: GAS-006 Ie-f (45) Quinone:Hydroquinone (i) Selective: GAS-0060 Ce(SO,),:Ce(NO,), + H20 (46) (i) Selective: GAS-0061 b K,Fe(CN),:K,Fe(CN), + H20 (47) (i) Selective: GAS-0061c-d © 1991 by CRC Press LLC

431 418 CRC of Metal Etchants Handbook AIB Etch (48) GAS-0059; -01 -01 19a; -018 1 Dislocation: 30; (i) KOH:H,O (49) GAS-02 10; -02 12d Junction: (i) flux NaOH/KOH, molten (50) Preferential: -0034; -0035; -0157; -0163b; -01 19b; -0122; GAS-0032; -0033; (i) -0123; -0124; -0127; -0162; -0163 molten NaOH:KOH, flux (51) GAS-0036 (i) Preferential: KOH:NaOH:Gly/EG (52) (i) GAS-0036 Preferential: KOH:H,O + 0, (53) 81 (i) Oxidation: GAS-01 KOH:K,Fe(CN),:H,O (54) (i) Polish: GAS-0040 (ii) Preferential: GAS-00 19 -0038b (iii) Staining: GAS-0037; NaOH:H,O, + (55) H,O (i) GAS-01 87 Junction: Polish: GAS-0175; -01 (ii) 15 -01 -0167d; -0173c 83a; -0185; -0187; -0142; Preferential: GAS-003 1; (iii) (iv) Selective: GAS-01 88a GAS-01 (v) Removal: 43 MeOH:Cl, (56) (i) Polish: GAS-0187a ETCHANTS GALLIUM ARSENIDE a GAS-0001 TIME: ETCH NAME: BRM TYPE: Halogen, polish TEMP: RT COMPOSITION: x x% Br, ... x ... MeOH DISCUSSION: The (100) (SI) wafers GaAs:Cr, substrates for epitaxy growth of GaAs. prepared .as following cleaning procedure was used: (1) etch polish in solution shown; (2) damage removaYpolish in H,S04:H202:H20; (3) boil in DI H,O to develop oxide; (4) remove oxide (5) boiling water and (6) remove oxide with HC1:EOH. (Note: Bromine HCl:H20; repeat with shown.) not concentration B F et a1 - J Phys Chem, REF: Lewis, 45,419(1984) Bhat, R - J Electron Muter, 14,433(1985) GAS-0184a: (100) (SI) wafers oriented 6"-off (100) toward (1 1 1)A, also (1 1 I), and (1 10) GaAs:Cr, AlGaAs wafers. Wafers as substrates for OMCVD epitaxy growth of both GaAs and used Prepare substrates by (1) chernlmech polish in solution shown to remove lap damage; layers. 5H2S04:1H202:lH20. and (3) etch clean in (2) degrease, Davis, et a1 - J Cryst Growth, 69,141(1984) G A GAS-0005: (100) wafers used 2"-off toward (1 lo), GaAs, as substrates for epitaxy growth of cut layers. After mixing BRM solution, allow it to sit 10 min before use. Clean substrates GaAs as follows: (1) chemlmech with solution shown; (2) degrease in boiling TCE, and polish in loading Immediately before 10H2S0,:lH202. (3) etch clean then MeOH, with rinse in use before H20. (Note: Allowing the BRM solution to sit 10 min rinse in DI vacuum, © 1991 by CRC Press LLC

432 produces a "stagnant" solution as some the bromine will gas-off while diffusing into the of It has been by other authors that bromine diffusion in methanol is complete methanol. shown 10 about min.) in Eastman, B2,188(1984) F - J Vac Sci Technol, GAS-0012a: Palmateer, S C L & GaAs:Cr, by Bridgman method and by HPLEC from ingots grown (100) (SI) wafers cut annealed shown, chemtmech polished in the solution were LPLEC. or After cutting, wafers 24 h in re-polished in the solution shown or in Clorox. Wafers were then polished H,, then in I 1 H,O just before loading 5H,SO,: an MBE vacuum system for epitaxy growth H20,: in of GaAs. GAS-0214: Inarey, S B - MacLaurin, Vac Sci Technol, A2(2),358(1985) & J (loo), n-type wafers used as substrates for Ge growth and GaAs, metallizing. Clean Au (1) polish with BRM solution; (2) MeOH chemlmech HCI dip: (4) DI H,O rinse; (3) GaAs: and (5) vacuum MBE system Ar+ ion sputter clean prior to Ge growth. in rinse; et Kolodziejski, L A GAS-0237: al - J Vac Sci Technol, B3(2),714(1985) (1 11) wafers used as substrates for MBE deposition of CdTe and CdMnTe thin GaAs, as dilute, magnetic semiconductor superlattices. BRM solutions can be used as removal films polishing and for these compounds. There was a 14% mismatch lattice of CdMnTeI etchants GaAs. Technol, a1 - J Vac Sci 18,(1985) B3(2),7 GAS-0238: Qadri, S B et deposition 10) used as substrates for GaAs, (1 wafers of Fe thin films for a structural MBE BRM mismatch. a 1.34% lattice 10) oriented with (1 were X-ray. Films films of study by etchants for these materials. can be and polishing used removal solutions as GAS-0002 TIME: ETCH NAME: BRM Halogen, preferential TEMP: TYPE: COMPOSITION: 1% Br, ... x ... MeOH x DISCUSSION: GaAs, 1 l)A wafer surfaces etched (1 the solution shown by immersion. Surface etch in will have (322) pit side slopes if the bromine concentration is greater than 1%. The pits plane slope angle as was measured from (1 1 l)A 10" surface. & 122,151 - J Electrochem Soc, Rode, L A l(1975) Kozi, L A REF: - - - - - GAS-0003a BRM TIME: ETCH NAME: Halogen, TYPE: TEMP: RT polish pmlmin on (1 10) RATE: 1 COMPOSITION: ... x Br, 1% x .. . . MeOH DISCUSSION: GaAs, (1 lo), (1 1 l), (100) wafers used in a general etch rate study. Etch ratio shown as: 6:5:4.6:1 (1 10):(~)~~:(100):(111)Ga. Solution used as an immersion etch to es- for etch rates. tablish (1 11)Ga = (1 1 l)A and (111)~s = (111)~ in general crystallo- (Note: notation of polar compounds.) graphic Ghandhi, S K REF: VLSI Fabrication Procedures, John - & Sons, New York, 1983 Wiley GAS-0004a: Budutt, R et a1 - J Electrochem Soc, 128,1573(1981) GaAs, (loo), used as substrates for growth of GaAs layers by LPE. n-type wafers Substrates were prepared follows: (1) Syntron system used to as polish with chemJmech solution shown; (2) degrease; (3) etch clean in IHCI:2H20 and DI water rinse. After LPE with (GaAI)As, substrate wafer was thinned 1.5% Br2:MeOH for microscope growth of © 1991 by CRC Press LLC

433 CRC of Metal Etchants Handbook 420 of the wafers were cleaved (110) and defect etched in study epitaxy layer. Other 1-2 min. to stacking faults. H,P04:H,S0,:H,0,, RT, Defects are similar & L A - personal communication, 1979 Cochran, Gomez, GAS-0200: (SI) wafers used in the fabrication of GaAs FET devices. Wafer back- GaAs:Cr, (100) steel discs and polished with on a shaker table using the solution weighted chedmech shown. - -- - GAS-0006a BRM TIME: 20 sec + 10 ETCH NAME: sec Halogen, polish TEMP: RT TYPE: COMPOSITION: ... 0.05% Br, x ... MeOH x DISCUSSION: (100), n-type wafers used in a surface cleaning study. Cleaning was done as GaAs, chedmech lap on lens paper soaked with solution shown and, after 20 hand follows: (1) sec; with and continue lapping an additional 10 dilute (2) rinse in NH40H:H,0 sec MeOH, solution); (3) rinse in BRM solution shown, and (4) final (AMH water rinse. Method DI Ge, Gap, GaSb, InP, InAs, and InSb. on: Si, also used Vac Aspenes, REF: Studa, A A - J D E Sci Technol, 20,488(1982) & GAS-0004b ETCH NAME: BRM TIME: TYPE: Halogen, thinning TEMP: RT COMPOSITION: 1.5% Br, ... x ... MeOH x DISCUSSION: by After epitaxy (GaAI)As epitaxy growth LPE. wafer substrates for used (100) GaAs, etch thinned the GaAs substrate the was and removed leaving thin (GaA1)As film free for (SFs) study. Stacking faults near the substratdepitaxy interface. Micro-cracks TEM start in the thin sections and attributed were observed probable tensile stress release. to REF: Ibid. - -- GAS-0007a BRM ETCH NAME: TIME: TEMP: RT TYPE: Halogen, isotropic See discussion RATE: COMPOSITION: ... 1-3% Br, x x MeOH ... DISCUSSION: GaAs, (100), and (110) wafer