DEPOSITION TECHNOLOGIESFOR FILMS AND COATINGSScience, Technology and ApplicationsSecond Editionnp NOYES PUBLICATIONSPark Ridge, New Jersey, U.S.A.Edited byRointan F Bunshah
Trang 2utilized in any form or by any means, elec-tronic or mechanical, including photocopying,recording or by any information storage andretrieval system, without permission in writingfrom the Publisher.
Library of Congress Catalog Card Number: 93-30751ISBN: 0-8155-1337-2
Printed in the United States
Published in the United States of America byNoyes Publications
Mill Road, Park Ridge, New Jersey 07656
10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Trang 3This volume is dedicated to Professor JohnThornton for his many pioneering contributions to thinfilm science and technology which have inspired somany of the scientists and engineers working in this field.
Trang 4Editors
Rointan F Bunshah, University of California, Los Angeles (Series Editor)Gary E McGuire, Microelectronics Center of North Carolina (Series Editor)
Stephen M Rossnagel, IBM Thomas J Watson Research Center
(Consulting Editor)
Electronic Materials and Process Technology
HANDBOOK OF DEPOSITION TECHNOLOGIES FOR FILMS AND COATINGS, SecondEdition: edited by Rointan F Bunshah
CHEMICAL VAPOR DEPOSITION FOR MICROELECTRONICS: by Arthur ShermanSEMICONDUCTOR MATERIALS AND PROCESS TECHNOLOGY HANDBOOK: edited byGary E McGuireHYBRID MICROCIRCUIT TECHNOLOGY HANDBOOK: by James J Licari and Leonard R.EnlowHANDBOOK OF THIN FILM DEPOSITION PROCESSES AND TECHNIQUES: edited by KlausK Schuegraf
IONIZED-CLUSTER BEAM DEPOSITION AND EPITAXY: by Toshinori Takagi
DIFFUSION PHENOMENA IN THIN FILMS AND MICROELECTRONIC MATERIALS: edited byDevendra Gupta and Paul S Ho
HANDBOOK OF CONTAMINATION CONTROL IN MICROELECTRONICS: edited by DonaldL Tolliver
HANDBOOK OF ION BEAM PROCESSING TECHNOLOGY: edited by Jerome J Cuomo,Stephen M Rossnagel, and Harold R Kaufman
CHARACTERIZATION OF SEMICONDUCTOR MATERIALS, Volume 1: edited by Gary E.McGuire
HANDBOOK OF PLASMA PROCESSING TECHNOLOGY: edited by Stephen M Rossnagel,Jerome J Cuomo, and William D Westwood
HANDBOOK OF SEMICONDUCTOR SILICON TECHNOLOGY: edited by William C O’Mara,Robert B Herring, and Lee P Hunt
HANDBOOK OF POLYMER COATINGS FOR ELECTRONICS, 2nd Edition: by James Licariand Laura A Hughes
HANDBOOK OF SPUTTER DEPOSITION TECHNOLOGY: by Kiyotaka Wasa and ShigeruHayakawa
HANDBOOK OF VLSI MICROLITHOGRAPHY: edited by William B Glendinning and JohnN Helbert
CHEMISTRY OF SUPERCONDUCTOR MATERIALS: edited by Terrell A VanderahCHEMICAL VAPOR DEPOSITION OF TUNGSTEN AND TUNGSTEN SILICIDES: by John E.J Schmitz
ELECTROCHEMISTRY OF SEMICONDUCTORS AND ELECTRONICS: edited by John McHardyand Frank Ludwig
Trang 5HANDBOOK OF CHEMICAL VAPOR DEPOSITION: by Hugh O PiersonDIAMOND FILMS AND COATINGS: edited by Robert F Davis
ELECTRODEPOSITION: by Jack W Dini
HANDBOOK OF SEMICONDUCTOR WAFER CLEANING TECHNOLOGY: edited by WernerKern
CONTACTS TO SEMICONDUCTORS: edited by Leonard J Brillson
HANDBOOK OF MULTILEVEL METALLIZATION FOR INTEGRATED CIRCUITS: edited bySyd R Wilson, Clarence J Tracy, and John L Freeman, Jr.
HANDBOOK OF CARBON, GRAPHITE, DIAMONDS AND FULLERENES: by Hugh O Pierson
Ceramic and Other Materials—Processing and Technology
SOL-GEL TECHNOLOGY FOR THIN FILMS, FIBERS, PREFORMS, ELECTRONICS ANDSPECIALTY SHAPES: edited by Lisa C Klein
FIBER REINFORCED CERAMIC COMPOSITES: edited by K S Mazdiyasni
ADVANCED CERAMIC PROCESSING AND TECHNOLOGY, Volume 1: edited by Jon G P.Binner
FRICTION AND WEAR TRANSITIONS OF MATERIALS: by Peter J Blau
SHOCK WAVES FOR INDUSTRIAL APPLICATIONS: edited by Lawrence E MurrSPECIAL MELTING AND PROCESSING TECHNOLOGIES: edited by G K Bhat
CORROSION OF GLASS, CERAMICS AND CERAMIC SUPERCONDUCTORS: edited byDavid E Clark and Bruce K Zoitos
HANDBOOK OF INDUSTRIAL REFRACTORIES TECHNOLOGY: by Stephen C Carnigliaand Gordon L Barna
CERAMIC FILMS AND COATINGS: edited by John B Wachtman and Richard A Haber
Related Titles
ADHESIVES TECHNOLOGY HANDBOOK: by Arthur H LandrockHANDBOOK OF THERMOSET PLASTICS: edited by Sidney H Goodman
SURFACE PREPARATION TECHNIQUES FOR ADHESIVE BONDING: by Raymond F.Wegman
Trang 6Donald M Mattox
Society of Vacuum CoatersAlbuquerque, New MexicoGary E McGuireMicroelectronics Center of NorthCarolinaResearch Triangle Park, North CarolinaJerome C Schmitt
Jet Process CorporationNew Haven, ConnecticutMorton SchwartzElectrochemical/Metal FinishingConsultantLos Angeles, CaliforniaArthur ShermanConsultantPalo Alto, CaliforniaRointan F BunshahDepartment of Materials Science andEngineering
University of California at Los AngelesLos Angeles, CaliforniaJan-Otto CarlssonDepartment of ChemistryUpsala UniversityUpsala, SwedenJoseph E Greene
Coordinated Science LaboratoryUniversity of Illinois at
Urbana-ChampaignUrbana, Illinois
Bret L Halpern
Jet Process CorporationNew Haven, Connecticut
Trang 7John A Thornton*
Coordinated Science LaboratoryUniversity of Illinois at Urbana-ChampaignUrbana, Illinois* Professor Thornton died unexpectedly inNovember, 1987.Robert C Tucker, Jr.Praxair Surface Technologies, Inc.Indianapolis, IndianaNOTICE
Trang 8i x
A decade after the first edition of this volume was published, a secondedition is being brought out partly due to the excellent response to the firstedition and also to update the many improvements in deposition technologies,the mechanisms and applications.
The entire volume has been extensively revised and contains 50% ormore new material Five entirely new chapters have been added Theorganization of the book has also been changed in the following respects:
1 Considerably more material has been added in PlasmaAssisted Vapor Deposition Processes.
2 A new chapter on Metallurgical Coating Applications hasbeen added.
The chapter in the first edition on Polymeric Coating techniques hasbeen omitted as it deserves a volume by itself Large topics such as coatingstechnology in microelectronics, diamond films, etc., have been treated inseparate volumes in this series.
Although there are some new competing volumes dealing with selectedtopics on the materials science of thin films, this volume remains the onlycomprehensive treatment of the entire subject of Deposition Technology.
Trang 9The core subjects are the basic technologies for the deposition of filmsand coatings These are the Physical Vapor Deposition (PVD) Processesconsisting of Evaporation, Sputtering, and Ion Plating; Chemical VaporDeposition (CVD) and Plasma-Assisted Chemical Vapor Deposition (PACVD);Electrodeposition and Electroless Plating; Thermal Spraying, Plasma Spray-ing and Detonation Gun Technologies Chapters on other subjects commonto the above technologies are included These are: Adhesion of Coatings,Cleaning of Substrates, Role of Plasmas in Deposition Processes, Structureof PVD Deposits, Growth and Structure of PVD Films, Mechanical andTribological Properties of PVD Deposits, Elemental and Structural Character-ization Techniques, and Metallurgical Coatings A relatively new develop-ment, Jet Vapor Deposition Process, was added as the last chapter in thebook during the page proof stage because of its novelty.
We hope that this volume will be useful to the multitude of disciplinesrepresented by the workers in this field and provide a source for futuredevelopments.
University of California Rointan F Bunshah
Trang 10Almost universally in high technology applications, a composite materialis used where the properties of the surface are intentionally different from thoseof the core Thus, materials with surface coatings are used in the entire cross-section of applications ranging from microelectronics, display devices, chemi-cal corrosion, tribology including cutting tools, high temperature oxidation/corrosion, solar cells, thermal insulation and decorative coatings (includingtoys, automobile components, watch cases, etc.).
A large variety of materials is used to produce these coatings They aremetals, alloys, refractory compounds (e.g., oxides, nitrides, carbides),intermetallic compounds (e.g., GaAg) and polymers in single or multiplelayers The thickness of the coatings ranges from a few atom layers to millionsof atom layers The microstructure and hence the properties of the coatingscan be varied widely and at will, thus permitting one to design new materialsystems with unique properties (A material system is defined as thecombination of the substrate and coating.)
Historically, coating technology evolved and developed in the last 30years in several industries, i.e., decorative coatings, microelectronics andmetallurgical coatings They used similar techniques but only with thepassage of time have the various approaches reached a common frontierresulting in much useful cross-fertilization That very vital process isproceeding ever more strongly at this time.
With this background in mind, a short course on Deposition Technolo-gies and their applications was developed and given on five consecutiveoccasions in the last three years This volume is based on the material usedin the course.
Trang 11It comprises chapters dealing with the various coating techniques, theresulting microstructure, properties and applications The specific techniquescovered are evaporation, ion plating, sputtering, chemical vapor deposition,electrodeposition from aqueous solution, plasma and detonation gun coatingtechniques, and polymeric coatings In addition several other chapters areadded Plasmas are used in many of the deposition processes and thereforea special chapter on this topic has been added Cleaning of the substrate andthe related topic of adhesion of the coating are common to many processesand a brief exposé of this topic is presented Characterization of the films, i.e.,composition, impurities, crystal structure and microstructure are essential tothe understanding of the various processes Two chapters dealing with thisarea are included Finally, a chapter on application of deposition techniquesin microelectronics is added to give one example of the use of several of thesetechniques in a specific area This volume represents a unique collection ofour knowledge on Deposition Technologies and their applications up to andincluding the state-of-the-art It is hoped that it will be very useful to students,practicing engineers and managerial personnel who have to learn about thisessential area of modern technology.
University of California R F Bunshah
Trang 12x vContents1Deposition Technologies: An Overview 27Rointan F Bunshah1.0 THE MARKET 272.0 INTRODUCTION 28
3.0 AIM AND SCOPE 30
4.0 DEFINITIONS AND CONCEPTS 31
5.0 PHYSICAL VAPOR DEPOSITION (PVD) PROCESSTERMINOLOGY 32
6.0 CLASSIFICATION OF COATING PROCESSES 34
7.0 GAS JET DEPOSITION WITH NANO-PARTICLES 36
8.0 MICROSTRUCTURE AND PROPERTIES 38
Trang 1310.9 Electrical Uses 44
11.0 “FRONTIER AREAS” FOR THE APPLICATION OFTHE PRODUCTS OF DEPOSITION TECHNOLOGY 44
12.0 SELECTION CRITERIA 46
13.0 SUMMARY 48
APPENDIX 1: DEPOSITION PROCESS DEFINITIONS 49
Conduction and Diffusion Processes 49
Chemical processes 50
Wetting Process 50
Spraying Processes 51
REFERENCES 54
2Plasmas in Deposition Processes 55
John A Thornton and Joseph E Greene1.0 INTRODUCTION 55
2.0 PARTICLE MOTION 56
2.1 Mean Free Path and Collision Cross Sections 56
2.2 Free Electron Kinetic Energy in a Plasma 58
2.3 Electron Energy Distribution Functions 592.4 Collision Frequencies 613.0 COLLECTIVE PHENOMENA 683.1 Plasma Sheaths 693.2 Ambipolar Diffusion 743.3 Plasma Oscillations 754.0 PLASMA DISCHARGES 764.1 Introduction 76
4.2 Ionization Balances and the Paschen Relation 77
Trang 143Surface Preparation for Film and Coating DepositionProcesses 108Donald M Mattox1.0 INTRODUCTION 1082.0 CONTAMINATION 1102.1 Recontamination 1113.0 ENVIRONMENT CONTROL 1134.0 CLEANING PROCESSES 1194.1 Particulate Removal 1204.2 Abrasive Cleaning 1214.3 Etch Cleaning 1214.4 Fluxing 1224.5 Alkaline Cleaners 1224.6 Detergent Cleaning 1224.7 Chelating Agents 1234.8 Solvent Cleaning 1234.9 Oxidation Cleaning 1284.10 Volatilization Cleaning 1304.11 Hydrogen Reduction Cleaning 1304.12 Electrolytic Cleaning 1315.0 DRYING AND OUTGASSING 1326.0 MONITORING OF CLEANING 1337.0 IN SITU CLEANING 1347.1 Ion Scrubbing 1348.0 PLASMAS 1348.1 Generation of Plasmas 1358.2 Plasma Chemistry 140
8.3 Bombardment Effects on Surfaces 141
8.4 Sputter Cleaning and Etching 143
9.0 STORAGE AND HANDLING 147
Trang 153.0 PVD PROCESSES 159
3.1 Preamble 159
3.2 PVD Processes 160
3.3 Advantages and Limitations 165
4.0 THEORY AND MECHANISMS 1664.1 Vacuum Evaporation 1665.0 EVAPORATION PROCESS AND APPARATUS 1695.1 The System 1696.0 EVAPORATION SOURCES 1726.1 General Considerations 1726.2 Resistance Heated Sources 1756.3 Sublimation Sources 176
6.4 Evaporation Source Materials 178
6.5 Induction Heated Sources 180
6.6 Electron Beam Heated Sources 181
6.7 Arc Evaporation 189
7.0 LASER INDUCED EVAPORATION/LASER ABLATION/PULSEDLASER DEPOSITION (PLD) 192
8.0 DEPOSITION RATE MONITORS AND PROCESS CONTROL 194
8.1 Monitoring of the Vapor Stream 194
8.2 Monitoring of Deposited Mass 196
8.3 Monitoring of Specific Film Properties 196
8.4 Evaporation Process Control 199
9.0 DEPOSITION OF VARIOUS MATERIALS 201
9.1 Deposition of Metals and Elemental Semiconductors 201
9.2 Deposition of Alloys 201
9.3 Deposition of Intermetallic Compounds 205
9.4 Deposition of Refractory Compounds 209
9.5 Reactive Evaporation Process 213
9.6 Activated Reactive Evaporation (ARE) 213
9.7 Materials Synthesized by Evaporation-based Processes 22310.0 MICROSTRUCTURE OF PVD CONDENSATES 22410.1 Microstructure Evolution 22410.2 Texture 23610.3 Residual Stresses 23710.4 Defects 237
11.0 PHYSICAL PROPERTIES OF THIN FILMS 241
12.0 MECHANICAL AND RELATED PROPERTIES 241
12.1 Mechanical Properties 241
13.0 PURIFICATION OF METALS BY EVAPORATION 256
APPENDIX 258
On Progress in Scientific Investigations in the Field of VacuumEvaporation in the Soviet Union 258
Trang 165Sputter Deposition Processes 275
John A Thornton and Joseph E Greene1.0 INTRODUCTION 2751.1 Sputter Deposition Systems 2781.2 Sputter-Deposition Applications 2791.3 Process Implementation 2821.4 History of Sputter Deposition and Background Reading 2832.0 SPUTTERING MECHANISMS 2842.1 Sputtering Rate 2852.2 Momentum Exchange 289
2.3 Alloys and Compounds 292
2.4 Sputtering with Reactive Species 295
2.5 The Nature of Sputtered Species 296
2.6 Energy Distribution of Sputtered Species 298
3.0 SPUTTER DEPOSITION TECHNIQUES 301
3.1 Planar Diode and the DC Glow Discharge 301
3.2 Triode Discharge Devices 3053.3 Magnetrons 3063.4 RF Sputtering 3183.5 Ion-Beam Sputtering 3274.0 SPUTTER DEPOSITION MODES 3284.1 Reactive Sputtering 3284.2 Bias Sputtering 332REFERENCES 3376Ion Plating 346Donald M Mattox1.0 INTRODUCTION 3462.0 PROCESSING PLASMA 3513.0 GENERATION OF PLASMAS 3513.1 DC Diode Discharge 3513.2 RF Discharge 3553.3 Microwave Discharges 3563.4 Electron Emitter Discharge 3563.5 Magnetron Discharges 3573.6 Plasma Enhancement 3584.0 PLASMA CHEMISTRY 3595.0 BOMBARDMENT EFFECTS ON SURFACES 3605.1 Collisional Effects 363
5.2 Surface Region Effects 368
5.3 Near Surface Region Effects 369
Trang 176.0 SOURCES OF DEPOSITING ATOMS 369
6.1 Thermal Vaporization 370
6.2 Sputtering 371
6.3 Vacuum Arcs 371
6.4 Chemical Vapor Precursors 373
7.0 REACTIVE ION PLATING 373
8.0 BOMBARDMENT EFFECTS ON FILM PROPERTIES 373
8.1 Effects: Adatom Nucleation 373
8.2 Effects: Interface Formation 374
8.3 Effects: Film Growth 3748.4 Film Adhesion 3768.5 Film Morphology/Density 3768.6 Residual Film Stress 3788.7 Crystallographic Orientation 3788.8 Gas Incorporation 3808.9 Surface Coverage 3808.10 Other Properties 3819.0 ION PLATING SYSTEM REQUIREMENTS 3819.1 Vacuum System 381
9.2 High Voltage Components 381
Trang 183.4 Substrate Cleaning Procedures 410
3.5 The CVD system 410
3.6 The Gas Dispensing System 411
3.7 The Reactor 413
3.8 The Exhaust System 415
3.9 Analysis of the Vapor in a CVD Reactor 417
4.0 GAS FLOW DYNAMICS 417
4.1 Gas Flow Patterns 420
4.2 Boundary Layers 423
4.3 Mass Transport Processes Across a Boundary Layer 428
5.0 RATE-LIMITING STEPS DURING CVD 4286.0 REACTION MECHANISMS 4367.0 NUCLEATION 4388.0 SURFACE MORPHOLOGY AND MICROSTRUCTURE OF CVDMATERIALS 4429.0 SELECTIVE DEPOSITION 4459.1 Area-Selective Growth 4469.2 Phase-Selective Deposition 45210.0 SOME APPLICATIONS OF THE CVD TECHNIQUE 45311.0 OUTLOOK 455REFERENCES 4568Plasma-Enhanced Chemical Vapor Deposition 460Arthur Sherman1.0 INTRODUCTION 460
2.0 REACTOR INFLUENCE ON PLASMA BEHAVIOR 461
2.1 DC/AC Glow Discharges 461
2.2 AC Discharges with Unequal Area Electrodes 464
2.3 Frequency Effects on RF Plasma Reactor Behavior 466
2.4 Adjusting DC Bias for Fixed Electrode Geometry 467
2.5 Plasma-Enhanced CVD (PECVD) Reactors 4673.0 FILMS DEPOSITED BY CVD 4723.1 Silicon Nitride 4723.2 Silicon Dioxide 4783.3 Conducting Films 481REFERENCES 4829Plasma-Assisted Vapor Deposition Processes:Overview 485Rointan F Bunshah1.0 INTRODUCTION 485
2.0 PLASMA-ASSISTED DEPOSITION PROCESSES 488
Trang 194.0 MATERIALS DEPOSITED BY REACTIVE VAPOR DEPOSITION
PROCESSES 491
5.0 KEY ISSUES IN PLASMA-ASSISTED REACTIVE VAPORDEPOSITION PROCESSES 492
5.1 Plasma Volume Chemistry 492
5.2 Type and Nature of the Bombardment of the Growing Film 4936.0 PLASMA-ASSISTED DEPOSITION TECHNIQUES IN CURRENTUSAGE 495
6.1 Plasma-Assisted Chemical Vapor Deposition 495
6.2 Sputter Deposition 496
6.3 Activated Reactive Evaporation (ARE) 497
7.0 LIMITATIONS OF CURRENT PLASMA-ASSISTED TECHNIQUES4998.0 HYBRID PROCESSES 5019.0 CONCLUSIONS 501REFERENCES 50510Deposition from Aqueous Solutions: An Overview 506Morton Schwartz1.0 INTRODUCTION 5062.0 GENERAL PRINCIPLES 5083.0 ELECTRODEPOSITION 5203.1 Mechanism of Deposition 5203.2 Parameters 5264.0 PROCESSING TECHNIQUES 5365.0 SELECTION OF DEPOSIT 5395.1 Individual Metals 5395.2 Alloy Deposition 5436.0 SELECTED SPECIAL PROCESSES 5506.1 Electroless Deposition 5506.2 Electroforming 5576.3 Anodizing 5606.4 Plating on Plastics 570
6.5 Plating Printed Circuit Boards 571
7.0 STRUCTURES AND PROPERTIES OF DEPOSITS 574
8.0 SUMMARY 596
APPENDIX A - Preparation of Substrates for Electroplating 597
APPENDIX B - Representative Electroless Plating Solution Formulation 599
APPENDIX C - Comparison of Aluminum Anodizing Processes (Types I, II and III) 602
Trang 2011Advanced Thermal Spray Deposition Techniques 617
Robert C Tucker, Jr.1.0 INTRODUCTION 617
2.0 EQUIPMENT AND PROCESSES 618
2.1 Plasma Spray Process 618
2.2 Detonation Gun Deposition Process 626
2.3 High Velocity Oxy-Fuel Deposition 628
2.4 Thermal Control 629
2.5 Auxiliary Equipment 630
2.6 Equipment-Related Coating Limitations 631
3.0 TOTAL COATING PROCESS 6323.1 Powder 6323.2 Substrate Preparation 6323.3 Masking 6333.4 Coating 6333.5 Finishing 635
4.0 COATING STRUCTURE AND PROPERTIES 636
4.1 Surface Macrostructure and Microstructure 6364.2 Microstructure 6374.3 Bond Strength 6434.4 Residual Stress 6444.5 Density 6454.6 Mechanical Properties 6474.7 Wear and Friction 6534.8 Corrosion Properties 6604.9 Thermal Properties 6624.10 Electrical Characteristics 6645.0 SUMMARY 665REFERENCES 66512Non-Elemental Characterization of Filmsand Coatings 669Donald M Mattox1.0 INTRODUCTION 6692.0 CHARACTERIZATION 6713.0 FILM FORMATION 677
4.0 ELEMENTAL AND STRUCTURAL ANALYSIS 681
Trang 215.5 Mechanical Properties 6955.6 Electrical Resistivity 6965.7 Temperature Coefficient of Resistivity (TCR) 6965.8 Electromigration 6975.9 Density 6975.10 Porosity 6985.11 Chemical Etch Rate (Dissolution) 7016.0 SUMMARY 701REFERENCES 70213Nucleation, Film Growth, and MicrostructuralEvolution 707Joseph E Greene1.0 INTRODUCTION 707
2.0 NUCLEATION AND THE EARLY STAGES OF FILM GROWTH 708
2.1 Three-Dimensional Nucleation and Growth 710
2.2 Two-Dimensional Nucleation and Growth 721
2.3 Stranski-Krastanov Nucleation and Growth 728
3.0 COMPUTER SIMULATIONS OF MICROSTRUCTUREEVOLUTION 730
3.1 Film Growth in the Ballistic Aggregation, Low-AdatomMobility, Limit 732
3.2 Effects of Adatom Migration 734
4.0 MICROSTRUCTURE EVOLUTION AND STRUCTURE-ZONE 736
5.0 EFFECTS OF LOW-ENERGY ION IRRADIATION DURING FILMGROWTH 743
5.1 Effects of Low-Energy Ion/Surface Interactionson Nucleation Kinetics 743
5.2 Effects of Low-Energy Ion/Surface Interactionson Film Growth Kinetics 750REFERENCES 76014Metallurgical Applications 766Rointan F Bunshah1.0 INTRODUCTION 7662.0 CORROSION 7663.0 GALVANIC CORROSION 7673.1 Galvanic Cells 768
4.0 EMF AND GALVANIC SERIES 770
5.0 COATINGS FOR GALVANIC CORROSION 770
Trang 227.0 EXAMPLES OF CORROSION-RESISTANT COATINGS 7737.1 Preamble 7738.0 HIGH TEMPERATURE OXIDATION/CORROSION 7769.0 FRICTION AND WEAR 7819.1 Adhesive Wear 7819.2 Fretting Wear 7819.3 Abrasive Wear 7829.4 Fatigue Wear 7829.5 Impact Erosion Wear by Solid Particles and Fluids 7829.6 Corrosive Wear 7839.7 Electric Arc Induced Wear 7839.8 Solution Wear (Thermodynamic Wear) 78310.0 COATINGS TO REDUCE FRICTION AND WEAR 78310.1 Friction 78310.2 Lubrication 78510.3 Wear 785REFERENCES 78715Characterization of Thin Films and Coatings 789Gary E McGuire1.0 INTRODUCTION 7892.0 SURFACE ANALYSIS TECHNIQUES 7892.1 Auger Electron Spectroscopy 7892.2 Photoelectron Spectroscopy 7972.3 Secondary Ion Mass Spectroscopy 8032.4 Rutherford Backscattering Spectroscopy 8123.0 IMAGING ANALYSIS TECHNIQUES 8223.1 Scanning Electron Microscopy 8223.2 Transmission Electron Microscopy 8284.0 OPTICAL ANALYSIS TECHNIQUES 8344.1 Ellipsometry 8344.2 Fourier Transform Infrared Spectroscopy 8384.3 Photoluminescence Spectroscopy 841REFERENCES 845
16Jet Vapor Deposition 848
Trang 234.0 EXAMPLES OF JVD FILMS AND APPLICATIONS 8574.1 Cu, Au Multilayer Electrodes; Al, Al2O3 Microlaminates 8574.2 PZT: Ferroelectric FRAM Nonvolatile Memories 8584.3 Electronic Grade Silicon Nitride 8594.4 Fiber Coating for Composite Materials 8594.5 Coating of Thermally Sensitive Membranes 8604.6 “Ceramic Host–Organic Guest” Films 8604.7 Polymer Deposition: Parylene 8615.0 SUMMARY 861REFERENCES 862
Trang 2427Deposition Technologies: AnOverviewRointan F Bunshah1.0 THE MARKET
Historically, from the late 1950s onward, decorative coatings or aluminumprovided the initial thrust for surface-engineered products for toys, textiles,etc Since then, the uses of deposition techniques in practically all areas ofengineering and many areas of science have produced a dramatic growth insales of equipment and products produced, particularly in the last decade.According to a recent survey (VDI-Technologiezeutrum-FRG), equipmentwith an estimated value of $6 billion was produced worldwide in 1989 for theirfilm surface technology Components and devices manufactured with suchequipment amounted to $60 billion and the value of the end-products whichcontained components made possible by surface engineering is estimated at$600 billion Just one industry, semiconductors, has changed entire productionlines every 5 to 6 years It is further estimated that only 10% of all items whichcan benefit from surface modifications are being processed today.
Surface engineering will remain a growth industry in the next decade,because surface-engineered products increase performance, reduce costs,and control surface properties independently of the substrate, thus offeringenormous potential due to the following:
! Creation of entirely new products
! Solution of previously unsolved engineering problems
! Improved functionality of existing products—engineering or decorative! Conservation of scarce materials
Trang 25Research and development expenditures in surface engineering are veryextensive It is reported that Japan is spending $100 to $150 million for R/Din diamond and diamond-like carbon coatings The payoff is estimated at $16billion by the end of this decade In advance thermal barrier coatings by PVDmethods for high temperature operation of turbine blades, it is estimated thatmore than $10 million have been spent in the United States alone Wear-resistant coatings for disc and heads has attracted much more than $10million in R/D expenditures worldwide The list continues to expand.
2.0 INTRODUCTION
Most materials used in high technology applications are composites,i.e., they have a near-surface region with properties differing from those of thebulk materials This is caused by the requirement that the material exhibita combination of various, and sometimes conflicting, properties For example,a particular engineering component may be required to have high hardness andtoughness (i.e., resistance to brittle crack propagation) This combination ofproperties can be obtained by having a composite material with high surfacehardness and a tough core Alternately, the need may be for a hightemperature, corrosion-resistant material with high elevated-temperaturestrength as is the case with the hot stage blades and vanes in a gas turbine.The solution again is to provide the strength requirement from the bulk and thecorrosion requirement from the surface.
In general, coatings are desirable, or even necessary, for a variety ofreasons including economics, materials conservation, unique properties, orthe engineering and design flexibility which can be obtained by separating thesurface properties from the bulk properties.
This near-surface region is produced by depositing a coating onto it (i.e.,
overlay coating) by processes such as physical or chemical vapor deposition,
electrodeposition, and thermal spraying, or by altering the surface material by
the in-diffusion of materials (i.e., diffusion coating or chemical conversion
coating), or by ion implantation of new material so that the surface layer now
consists of both the parent and added materials.
Trang 26As stated above, the coating/substrate combination is a compositematerials system The behavior of this composite system depends not onlyon the properties of the two components (i.e., the coating material and thesubstrate material), but also on the interaction between the two (i.e., thestructure and properties of the coating/substrate interface) which is integral tothe very important factor of adhesion of coatings In some cases, such as foroverlay coatings, this is a distinct region For others, such as ion implantationor diffusion coatings, it is not a discrete region.
Historically, most solid metallic and some ceramic materials wereproduced by melting/solidification technology Since the advent of depositiontechnologies (i.e., production of solid materials from the vapor), the diversityof materials that can be produced has more than doubled because theproperties of solid materials produced from the vapor phase can be varied overa much wider range than the same material produced from the liquid phase.This is because melt techniques produce solid materials with properties close
to equilibrium properties whereas the deposition conditions may be so chosen
as to produce materials from the vapor phase with properties close toequilibrium (similar to their melt-produced counterparts), or properties far
removed from equilibrium properties (non-equilibrium properties) Moreover,
a much greater variation in microstructure is possible with vapor sourcematerials For example, a copper-nickel alloy produced by solidification fromthe melt will always consist of a single phase solid solution, whereas the samealloy produced by alternate deposition from two sources may consist ofalternate layers of nickel and copper, i.e., a laminate composite or a solidsolution depending on the deposition temperature.
Trang 273.0 AIM AND SCOPE
The aim of this volume is to give the reader a perspective on severalcoating techniques with emphasis on the techniques which are used in criticalor demanding (i.e., high technology) applications Consequently, some of thetechniques such as painting, dip coating, or printing will not be emphasizedexcept as they pertain to some special application like thick film electricalcomponents Nevertheless, a wide variety of techniques and their applicationswill be covered The material is intended to present a broad spectrum ofdeposition technologies to those who may be familiar with only one or twotechniques Hopefully, this will help them to select and weigh variousalternatives when the next technological problem involving coatings facesthem.
The specific deposition technologies to be covered are:
1 Physical Vapor Deposition including evaporation, ion plating andsputtering.
2 Chemical Vapor Deposition and Plasma-Assisted ChemicalVapor Deposition
3 Electrodeposition and Electroless Deposition.
4 Plasma Spraying as well as a very special variant calledDetonation Gun Technology.
There are some generic areas common to several of the depositiontechnologies, the most prominent example being the use of plasmas in manyof the deposition technologies Therefore, a chapter on plasmas in depositionprocesses is included Another common topic is cleaning of the substrate andadhesion of the coating A chapter is included on that topic.
A further common topic is the characterization of the chemical compositionand the microstructure of the coating at various levels of resolution A chapteris included to satisfy this need.
New chapters are added dealing with Metallurgical Applications (Corrosion,Function and Wear), Overview of Plasma-Assisted Deposition Processes,Plasma-Assisted Chemical Vapor Deposition, and Nucleation/Growth of ThinFilms.
Trang 28In each of the chapters on deposition technologies, the theory,methodology, advantages, limitations and applications are discussed.
4.0 DEFINITIONS AND CONCEPTS
In order to avoid potential problems, it is necessary to clarify certaindistinctions which are common and pertinent to deposition technologies.These are as follows:
1 Diffusion vs.Overlay Coatings—Diffusion coatings are producedby the complete interdiffusion of material applied to the surfaceinto the bulk of the substrate material Examples of this are thediffusion of oxygen into metals to form various sub-oxide andoxide layers, the diffusion of aluminum into nickel base alloys toform various aluminides, etc A characteristic feature of diffusioncoatings is a concentration gradient from the surface to theinterior, as well as the presence of various layers as dictated bythermodynamic and kinetic considerations Ion implantationmay be considered to be a special case where the coatingmaterial is implanted at a relatively shallow depth (a few hundredangstrom units) from the surface.
An overlay coating is an add-on to the surface of the part, e.g.,gold-plating on an iron-nickel alloy, or titanium carbide onto acutting tool, etc Depending upon the process parameters, aninterdiffusion layer between the substrate and the overlay coatingmay or may not be present.
Trang 293 Steps in the Formation of a Deposit—There are three steps in theformation of a deposit:
a Synthesis or creation of the depositing speciesb Transport from source to substrate
c Deposition onto the substrate and film growth
These steps can be completely separated from each other or be super-imposed on each other depending upon the process under consideration Theimportant point to note is that if, in a given process, these steps can beindividually varied and controlled, there is much greater flexibility for such aprocess as compared to one where they are not separately variable This isanalogous to the degrees of freedom in Gibbs phase rule For example,consider the deposition of tungsten by CVD process It takes place by thereaction:
Heated
WF6(vapor) + 3H2(gas) ———" W(deposit) + 6HF(gas)Substrate
The rate of deposition is controlled by the substrate temperature At ahigh substrate temperature, the deposition rate is high and the structureconsists of large columnar grains This may not be a desirable structure Onthe other hand, if the same deposit is produced by evaporation of tungsten, thedeposition rate is essentially independent of the substrate temperature so thatone can have a high deposition rate and a more desirable microstructure Onthe other hand, a CVD process may be chosen over evaporation because of
considerations of throwing power, i.e., the ability to coat irregularly shaped
objects, since high vacuum evaporation is basically a line-of-sight technique.
5.0 PHYSICAL VAPOR DEPOSITION (PVD) PROCESS TERMINOLOGY
Trang 30an example, if the activated reactive evaporation (ARE) process is used witha negative bias on the substrate, it is very often called reactive ion plating.Simple evaporation using an RF heated crucible has been called gasless ion
plating An even worse example of the confusion that can arise is found in the
chapter on ion plating in this volume (Ch 6) where the material is convertedfrom the condensed phase to the vapor phase using thermal energy (i.e.,evaporation) or momentum transfer (i.e., sputtering) or supplied as a vapor(very similar to CVD processes) Carrying this to the logical conclusion, onemight say that all PVD processes are ion plating! On the other hand, the mostimportant aspect of the ion plating process is the modification of themicrostructure and composition of the deposit caused by the ion bombardmentof the deposit resulting from the bias on the substrate, i.e., what is happeningon the substrate.
To resolve this dilemma, it is proposed that we consider all of these basicprocesses and their variants as PVD processes and describe them in termsof the three steps in the formation of a deposit as described above This willhopefully remove the confusion in terminology.
Step 1: Creation of Vapor Phase Specie There are three ways to put a
material into the vapor phase-evaporation, sputtering or chemical vapors andgases.
Step 2: Transport from Source to Substrate The transport of the vapor
species from the source to the substrate can occur under line-of-sight ormolecular flow-conditions (i.e., without collisions between atoms andmolecules); alternately, if the partial pressure of the metal vapor and/or gasspecies in the vapor state is high enough or some of these species are ionized(by creating a plasma), there are many collisions in the vapor phase duringtransport to the substrate.
Step 3: Film Growth on the Substrate This involves the deposition of the
film by nucleation and growth processes The microstructure and compositionof the film can be modified by bombardment of the growing film by ions fromthe vapor phase resulting in sputtering and recondensation of the film atomsand enhanced surface mobility of the atoms in the near-surface and surfaceof the film.
Trang 316.0 CLASSIFICATION OF COATING PROCESSES
Numerous schemes can be devised to classify or categorize coatingprocesses, none of which are very satisfactory since several processes willoverlap different categories For example, the Appendix contains a list anddefinitions of various deposition processes based upon those provided byChapman and Anderson with some additions These authors classify theprocesses under the general heading of Conduction and Diffusion Processes,Chemical Processes, Wetting Processes and Spraying Processes Here, theChemical Vapor Deposition process falls under the Chemical Processes, andthe Physical Vapor Deposition Process (Evaporation, lon Plating and Sputtering)falls under the spraying processes The situation can easily get confused as,for example, when Reactive and Activated Reactive Evaporation, and Reactivelon Plating are all classified as Chemical Vapor Deposition processes byYee[3] who considers them thusly because a chemical reaction is involved andit does not matter to him whether evaporated metal atoms or stable liquid orgaseous compounds are the reactants Another classification of the methodsof deposition of thin films is given by Campbell.[4] He considers the overlapbetween physical and chemical methods, e.g., evaporation and ion plating,sputtering and plasma reactions, reactive sputtering and gaseousanodization.[5] He classifies the Chemical Methods of Thin Film Preparationas follows:
Chemical Methods of Thin Film Preparation
Basic Class Method
Trang 32In addition, he considers the following as chemical methods of thick filmpreparation: Glazing, Electrophoretic, Flame Spraying and Painting.
In contrast to the chemists’ approach given above, the physicists’approach to deposition processes is shown in the following classification ofvacuum deposition techniques by Schiller, Heisig and Goedicke[6] and byWeissmantel.[7]
Figure 1.1 Survey of vacuum deposition techniques (Schiller[6])
A different classification comes from a materials background where theconcern is with structure and properties of the deposits as influenced byprocess parameters Thus, Bunshah and Mattox[8] give a classification basedon deposition methods as influenced by the dimensions of the depositingspecie, e.g., whether it is atoms/molecules, liquid droplets or bulk quantities,as shown in Table 1.1.
In atomistic deposition processes, the atoms form a film by condensingon the substrate and migrating to sites, where nucleation and growth occurs.Further, adatoms do not achieve their lowest energy configurations and theresulting structure contains high concentrations of structural imperfections.Often the depositing atoms react with the substrate material to form a complexinterfacial region.
Trang 33the coating For high energy deposition processes, the depositing particlesreact with or penetrate into the substrate surface.
Particulate deposition processes involve molten or solid particles and theresulting microstructure of the deposit depends on the solidification orsintering of the particles Bulk coatings involve the application of largeamounts of coating material to the surface at one time such as in painting.Surface modification involves ion, thermal, mechanical, or chemical treatments,which alter the surface composition or properties All of these techniques arewidely used to form coatings for special applications.
Table 1.1 Methods of Fabricating Coatings
7.0 GAS JET DEPOSITION WITH NANO-PARTICLES
Trang 34Figure 1.2 Schematic diagram of gas deposition apparatus.
advent of evaporation[9] and sputtering processes[10] to produce nano-particles (nm dimensions), the same concept can be used to producecoatings by carrying nano-particles in a gas stream and impinging them ona substrate.[11][12] Figure 1.2 shows a schematic of this process wheremetallic nano-particles produced by evaporation are carried in a gas stream,accelerated through a nozzle and impinged on a substrate to produce acoating Single nozzles or multiple nozzle configurations can be used, thelatter producing an array of dots, for example The attributes of this processare:
1 Direct write maskless processing to produce dots, lines, andother shapes.
2 High deposition rate, 10 - 20 µm per second over a small area.3 Low temperature (room temperature) deposition.
4 Metals, alloys, ceramics, and organic materials can bedeposiited.
5 Multiphase films with uniform mixing can be produced.6 The collection officiency is very high, ~90%, i.e very little waste
or scatter.
Examples of applications of this technique are:
1 Electrical connecting lines in circuits including the repair aspect.2 Fabrication of microelectrodes
3 Oxide superconductor contacts.4 Capacitors
Trang 358.0 MICROSTRUCTURE AND PROPERTIES
Trang 36The microstructure of the depositing coating in the atomic depositionprocesses depends on how the adatoms are incorporated into the existingstructure Surface roughness and geometrical shadowing will lead topreferential growth of the elevated regions giving a columnar type microstructureto the deposits.[13] This microstructure will be modified by substratetemperature, surface diffusion of the atoms, ion bombardment during deposition,impurity atom incorporation and angle of incidence of the depositing adatomflux The structure zone model of Movchan and Demchishin[14] for vacuumdeposited films is discussed in later chapters.
In chemical vapor deposition, the chemical species containing the filmatoms is generally reduced or decomposed on the substrate surface, often athigh temperatures Care must be taken to control the interface reactionbetween coating and substrate and between the substrate and the gaseousreaction products The coating microstructure which develops is very similarto that developed by the vacuum deposition processes, i.e., small-grainedcolumnar structures to large-grained equiaxed or oriented structures.
Each of the atomistic deposition processes has the potential of depositingmaterials which vary significantly from the conventional metallurgicallyprocessed material The deposited materials may have high intrinsicstresses, high point defect concentration, extremely fine grain size, orientedmicrostructures, metastable phases, incorporated impurities, and macro andmicro porosity These properties may be reflected in the physical propertiesof the materials and by their response to applied stresses such as mechanicalloads, chemical environments, thermal shock or fatigue loading Metallurgicalproperties which may be affected include elastic constants, tensile strength,fracture toughness, fatigue strength, hardness, diffusion rates, friction/wearproperties, and corrosion resistance In addition, the unique microstructureof the deposited material may lead to such effects as anomalously lowannealing and recrystallization temperatures where the internal stresses andhigh defect concentration aid in atomic rearrangement.
Trang 37In vapor deposition processes, impurity incorporation during depositioncan give high intrinsic stresses or impurity stabilized phases which are notseen in the bulk forms of the materials Reactive species allow the depositionof compounds such as nitrides, carbides, borides and oxides Gradeddeposits can be formed.
Vapor deposition processes have the capability of producing unique and/or nonequilibrium microstructures One example is the fine dispersion ofoxides in metals, where the oxide particle size and spacing is very small (100- 500 Å) Alternately, metals and alloys deposited at high substratetemperatures have properties similar to those of conventionally fabricated(cast, worked and heat treated) metals and alloys A more recent exampleis the nano-scale laminate composites consisting of alternate layers ofrefractory compounds with unusually high hardness values.
9.0 UNIQUE FEATURES OF DEPOSITED MATERIALS AND GAPS INUNDERSTANDING
It is useful to state at this point some of the unique features of materialsproduced by deposition technologies They are:
1 Extreme versatility of range and variety of deposited materials.2 Overlay coatings with properties independent of the
thermodynamic compositional constraints.
3 Ability to vary defect concentration over wide limits, thus resultingin a range of properties comparable to, or far removed fromconventionally fabricated materials.
4 High quench rates available to deposit amorphous materials.5 Generation of microstructures different from conventionally
processed materials, e.g., a wide range of microstructures—ultrafine (submicron grain or laminae size) to single crystal films.6 Fabrication of thin self-standing shapes even from brittle materials.7 Ecological benefits with certain techniques.
Trang 381 Microstructure and properties in the range of 500 to 10,000 Å—particularly important for submicron microelectronics, reflectivesurfaces and corrosion.
2 (a) Effect of the energy of the depositing species on
interfacial interaction, nucleation and growth of deposit.
(b) Effect of “substrate surface condition,” i.e.,
contamination (oxide) layers, adsorbed gases,surface topography.
3 Residual stresses—influence of process parameters.
Considerable progress and understanding has developed in the lastdecade.
10.0 CURRENT APPLICATIONS
The applications of coatings in current technology may be classed intothe following generic areas:
Optically Functional—Laser optics (reflective and transmitting),
architectural glazing, home mirrors, automotive rear view mirrors,reflective and anti-reflective coatings, optically absorbing coatings,selective solar absorbers.
Electrically Functional—Electrical conductors, electrical contacts,
active solid state devices, electrical insulators, solar cells.
Mechanically Functional—Lubrication films, wear and erosion
resistant coatings, diffusion barriers, hard coatings for cutting tools.
Chemically Functional—Corrosion resistant coatings, catalytic
coatings, engine blades and vanes, battery strips, marine useequipment.Decorative—Watch bezels, bands, eyeglass frames, costumejewelry.A few examples are chosen to illustrate them in greater detail.10.1 Decorative/Functional Coating
Trang 39replaced with lightweight plastic, overcoated with chromium by sputtering forthe appearance to which the consumer is accustomed.
Another extensive application is aluminum-coated polymer films for heatinsulation, decorative and packaging applications.
A rapidly growing application is the use of a gold-colored wear-resistantcoating of titanium nitride on watch bezels, watch bands and similar items.
A new application is black wear-resistant hard carbon films.
10.2 High Temperature Corrosion
Blades and vanes used in the turbine-end of a gas turbine engine aresubject to high stresses in a highly corrosive environment of oxygen-, sulfur-and chlorine-containing gases A single or monolithic material such as a hightemperature alloy is incapable of providing both functions The solution is todesign the bulk alloy for its mechanical properties and provide the corrosionresistance by means of an overlay coating of an M-Cr-AI-Y alloy where Mstands for Ni, Co, Fe or Ni + Co The coating is deposited in production byelectron beam evaporation and in the laboratory by sputtering or plasmaspraying With the potential future use of synthetic fuels, considerableresearch will have to be undertaken to modify such coating compositions forthe different corrosive environments as well as against erosion from theparticulate matter in those fuels.
10.3 Environmental Corrosion
Thick ion plated aluminum coatings are used in various
irregularly-shaped parts of aircraft and space-craft as well as on fasteners: (a) to replace
electroplated cadmium coatings which sensitize the high-strength parts to
hydrogen embrittlement or (b) to prevent galvanic corrosion which would occurwhen titanium or steel parts contact aluminum or (c) to provide good
brazeability New alloy coatings in the micron thickness range have beendeveloped.
10.4 Friction and Wear
Trang 40especially important for critical parts used in long-lifetime applications sinceconventional organic fluid lubricants are highly susceptible to irreversibledegradation and creep over a long time.
10.5 Materials Conservation
Aluminum is continuously coated on a steel strip, 2 feet wide and 0.006inches thick to a 250 micro-inch thickness in an air-to-air electron-beamevaporator at the rate of 200 feet/minute The aluminum replaces tin, whichis becoming increasingly scarce and costly The strip then goes to the lacquerline and is used for steel can production With the change in Eastern Europe,this line has switched to deposition of Cr and Cu on steel.
10.6 Cutting Tools
Cutting tools are made of high-speed steel or cemented carbides Theyare subject to degradation by abrasive wear as well as by adhesive wear Inthe latter mode, the high temperatures and forces at the tool tip promotemicrowelding between the steel chip from the workpiece and the steel in thehigh-speed steel tool or the cobalt binder phase in the cemented carbide Thesubsequent chip breaks the microweld and causes tool surface cratering andwear A thin layer of a refractory compound such as TiC, TiN, Al2O3 preventsthe microwelding by introducing a diffusion barrier Improvements in tool lifeby factors of 300 to 800% are possible as well as reductions in cutting forces.The coatings are deposited by chemical vapor deposition or physical vapordeposition Some idea of the importance of such coatings can be assessedfrom the fact that the yearly value of cutting tools purchased in the U.S is $1billion and the cost of machining is approximately $60 billion.
The last decade has seen major advances in this area and some of theseare:
! Ti alloy nitrides, e.g., (Ti, Al) N! Ti carbonitrides, e.g., Ti (C,N)
! Multilayer coatings of different nitrides