Handbook of
`THIN FilM
`· DEPOSITION
`
`Processes and Technologies
`SECOND EDITION
`
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`
`IPR2015-01087 - Ex. 1040
`Micron Technology, Inc., et al., Petitioners
`1
`
`

`
`Copyright © 2002 by Noyes Publications
`No part of this book may be reproduced or
`utilized in any form or by any means, elec(cid:173)
`tronic or mechanical, including photocopying,
`recording or by any information storage and
`retrieval system, without permission in writing
`from the Publisher.
`Library of Congress Catalog Card Number: 2001135178
`ISBN : 0-8155-1442-5
`Printed in the United States
`
`Published in the United States of America by
`Noyes Publications I William Andrew Publishing
`13 Eaton A venue
`Norwich, NY 13815
`1-800-932-7045
`www. williamandrew .com
`www.knovel.com
`
`10 9 8 7 6 5 4 3 2 I
`
`Library of Congress Cataloging-in-Publication Data
`
`Handbook of Thin-Film Deposition Processes and Techniques I [edited]
`by Krishna Seshan. ·· 2nd edition
`em.
`p.
`Includes bibliographical references and index.
`ISBN 0-8155-1442-5
`I. Thin film devices ·· Design and construction ·· Handbooks,
`manuals, etc.
`I. Seshan, Krishna.
`II. Title.
`•
`TK7872.T55H36
`2001135178
`621.381'72--dcl9
`CIP
`
`NOTICE
`
`To the best of our knowledge the information in this publication is
`accurate; however the Publisher does not assume any responsibility
`or liability for the accuracy or completeness of, or consequences
`arising from, such information. This book is intended for informational
`purposes only. Mention of trade names or commercial products does
`not constitute endorsement orrecommendation for use by the Publisher.
`Final determination of the suitability of any information or product
`for use contemplated by any user, and the manner of that use, is the
`sole responsibility of the user. We recommend that anyone intending
`to rely on any recommendation of materials or procedures mentioned
`in this publication should satisfy himself as to such suitability, and
`that he can meet all applicable safety and health standards.
`
`2
`
`

`
`Contents
`
`Recent Changes in the Semiconductor Industry ....................... 1
`Krishna Seshan
`1.0 COST OF DEVICE FABRICATION .. .......... .... .......... ..... I
`1.1 Role of Cleanliness in Cost of Equipment .............. 3
`1.2 Role of Chip Size Trends, Larger Fabricators,
`and 12" Wafers ........................................................ 4
`1.3 Lithography, Feature Size, and Cleaner
`Fabricators and Equipment.. .................................... 4
`1.4 Defect Density and the Need for Cleaner
`Fabricators ................................ ............................... 5
`1.5 Conclusions ........... .... ........... .... ........ ....................... 7
`2.0 TECHNOLOGY TRENDS, CHIP SIZE,
`PERFORMANCE, AND MOORE'S LAW .. .................... 7
`2.1 Performance of Packaged Chips- Trends .............. 8
`REFERENCES .. ............ ............................. ............................... 9
`
`xvii
`
`3
`
`

`
`xviii Contents
`
`1
`
`Deposition Technologies and Applications: Introduction
`and Overview ..................................................................... 11
`Werner Kern and Klaus K. Schuegraf
`1.0 OBJECTIVE AND SCOPE OF THIS BOOK ..... ......... .. 11
`2.0
`IMPORTANCE OF DEPOSITION
`TECHNOLOGY IN MODERN FABRICATION
`PROCESSES ................................................................... 12
`3.0 CLASSIFICATION OF DEPOSITION
`TECHNOLOGIES ..................................... .... .... .............. 14
`4.0 OVERVIEW OF VARIOUS THIN-FILM
`DEPOSITION TECHNOLOGIES ............ ...................... 14
`4.1 Evaporative Technologies ........ ...... ............ .. ......... 14
`4.2 Glow-Discharge Technologies .................. ...... ...... 17
`4.3 Gas-Phase Chemical Processes ................... .. ........ 20
`4.4 Liquid-Phase Chemical Formation ............. ...... .. .. . 25
`5.0 CRITERIA FOR THE SELECTION OF A
`DEPOSITION TECHNOLOGY FOR SPECIFIC
`APPLICATIONS ................................................... ...... .... 28
`5.1 Thin-Film Applications ......................................... 29
`5.2 Material Characteristics .............................. ........... 30
`5.3 Process Technology ................ : .............................. 32
`5.4 Thin-Film Manufacturing Equipment ........ ........... 35
`6.0 SUMMARY AND PERSPECTIVE FOR THE FUTURE . 36
`ACKNOWLEDGMENTS ...................................................... . 39
`REFERENCES ....................................................................... . 40
`
`2
`
`Silicon Epitaxy by Chemical Vapor Deposition .............. 45
`Martin L. Hammond
`1.0
`INTRODUCTION .............................................. ............. 45
`1.1 Applications of Silicon Epitaxy ................ ............ 46
`2.0 THEORY OF SILICON EPITAXY BY CVD ... ............. 49
`3.0 SILICON EPITAXY PROCESS CHEMISTRY .... .... ..... 52
`
`4
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`

`
`Contents
`
`xix
`
`4.0 COMMERCIAL REACTOR GEOMETRIES ............ .... 54
`4.1 Horizontal Reactor ............................................ ..... 55
`4.2 Cylinder Reactor ...... ...... ........................................ 56
`4.3 Vertical Reactor ............................ .... ................ ..... 56
`4.4 New Reactor Geometry .................................... ..... 56
`5.0 THEORY OF CHEMICAL VAPOR DEPOSITION .. .... 57
`6.0 PROCESS ADJUSTMENTS .......................................... 60
`6.1 Horizontal Reactor .................. ............................... 61
`6.2 Cylinder Reactor .......... ....... ................................... 63
`6.3 Vertical Reactor .......... ............................... .. .......... 64
`6.4 Control of Variables .... ............................. .. ........ ... 66
`7.0 EQUIPMENT CONSIDERATIONS FOR
`SILICON EPITAXY .............. ........................................ . 67
`7.1 Gas Control System .. .. .. ................... ...................... 68
`7.2 Leak Testing .................... ..................... ................. 68
`7.3 Gas Flow Control .............................................. ..... 70
`7.4 Dbpant Flow Control ...... ....................................... 72
`8.0 OTHER EQUIPMENT CONSIDERATIONS ............... . 78
`8.1 Heating Power Supplies ........................................ 78
`8.2 Effect of Pressure .... .. ............................................ 78
`8.3 Temperature Measurement ........................ ............ 79
`8.4 Backside Transfer ...... .... ............................ ............ 82
`8.5
`Intrinsic Resistivity .................................... ....... .. ... 83
`8.6 Phantom p-Type Layer .............................. ............ 84
`9.0 DEFECTS IN EPITAXY LAYERS .................... ............ 84
`10.0 SAFETY .............................................................. ...... ...... 87
`11.0 KEY TECHNICAL ISSUES ................................ ........... 87
`11 .1 Productivity/Cost ................................................... 87
`11.2 Uniformity/Quality .................................... ............ 91
`11.3 Buried Layer Pattern Transfer .................. ............. 91
`11.4 Autodoping ................................................ ............ 96
`12.0 NEW MATERIALS TECHNOLOGY FOR
`SILICON EPITAXY .......................................... ........... 104
`13.0 LOW TEMPERATURE EPITAXY .................... .......... 105
`
`5
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`

`
`xx Contents
`
`3
`
`CONCLUSIONS o o o 000 000 o 00 o o 00 o 000 o 00 0 000 0 00 0 o 00 0 0 00 0 00 0 0 00 0 0 00 0 000 0 oooo· 0 00 00 .oo 106
`REFERENCES oo 000 0 000 000 0 000 0 oooo .......... 0 ...... 0 0 00 o .. 0 .. o o .. o ... o 0 ...... o o o o .. 107
`
`Chemical Vapor Deposition of Silicon Dioxide Films .. 111
`John Foggiato
`loO
`INTRODUCTION ...... ooooooooooooooooooooooooooooooooooooooooooooooooooo 111
`200 OVERVIEW OF ATMOSPHERIC PRESSURE
`CVD
`.. oooooo oo oo ooOooo .ooo.ooOoooooooooooooooooooooooooooo•oo •oo•oo•ooooooooooo oo 112
`201 Basis of Atmospheric Deposition ........ 00 00 00 ........ 00 116
`202 Parameters Affecting Chemical Reactions .... 00000 120
`203 Reaction Chamber Designs oooooooooo .... oo ....... oooooooooo 124
`2.4 Process Exhaust and Particle Containment .... 00000 125
`300 PLASMA ENHANCED CHEMICAL VAPOR
`DEPOSITION oooooooooooooooooooooooooo;;oooooooooooooooooooooooooooooooooooo 126
`301 Deposition Rates 00000000000000000000000000000000000000000000000000 127
`302 Film Characteristics for Different Chemistries 000 132
`400 PROPERTIES OF DIELECTRIC FILMS oooooooo oooooooo·oo· 136
`500 NEW DEPOSITION TECHNOLOGIES 0000000000000000000000 137
`501 Trends for CVD of Dielectric Films oooo oo oo ........ ooo 143
`600 FUTURE DIRECTIONS FOR CVD.OF
`DIELECTRIC FILMS ................ 0000 .............................. 0 147
`700 SUMMARY ooo ooooo oooooooo .............. o ............ oo .. ooooooooo .......... 148
`REFERENCES 0 .. o ...... oo ......... oo 00 00 00 .... 0 ............. 00 .. 00 .. 0 0 0 00 00 00 .. 00 .. 149
`
`4 Metal Organic Chemical Vapor Deposition: Technology
`and Equipment ................................................................. 151
`John L. Zitko
`INTRODUCTION .. oo .. ..... oo.oooo ........... oo ... oooooooooo ............. 151
`1.0
`200 APPLICATIONS OF MOCVD ............................ 000000000 156
`300 PHYSICAL AND CHEMICAL PROPERTIES
`OF SOURCES USED IN MOCVD ... oooo ...... oo oo ooooooooooooo 158
`Physical and Chemical Properties of
`301
`Organometallic Compounds 00 ... 00 00 00 00 00 00 ......... 00 .... 160
`3.2 Organometallic Source Packaging ...................... 168
`303 Hydride Sources and Packaging .......... 000000 .......... 171
`
`6
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`

`
`Contents
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`xxi
`
`4.0 GROWTH MECHANISMS, CONDITIONS,
`AND CHEMISTRY .................... ... ...................... ........ . 173
`4.1 Growth Mechanisms .... ........................................ 173
`4.2 Growth Conditions, Chemistry and
`Materials Purity ................................................... 17 4
`5.0 SYSTEM DESIGN AND CONSTRUCTION ........... ... 181
`5.1 Leak Integrity and Cleanliness .. ... ......... ....... ....... 181
`5.2 Oxygen Gettering Techniques ..... ....... .. .......... ..... 182
`5.3 Gas Manifold Design ............................. .............. 183
`5.4 Reaction Chamber ........................... ...... .............. 187
`5.5 Exhaust and Low Pressure MOCVD ................... 193
`6.0 FUTURE DEVELOPMENTS ............... ............ ............ 194
`6.1
`Improved Uniformity Over Larger Areas ........... 195
`6.2
`In-situ Diagnostics and Control.. ..... .. ....... .. .... ..... 195
`6.3 New Materials ......... ..... ............................. ....... .... 199
`ACKNOWLEDGMENTS ..... .... ............................................ 199
`REFERENCES .................. .... ......... ....................................... 200
`
`5
`
`Feature Scale Modeling ................................................... 205
`VivekSingh
`1.0
`INTRODUCTION ..... .... ....... .. ........ ......... .... .... ............ .. 205
`2.0 COMPONENTS OF ETCH AND DEPOSITION
`MODELING ...... ......................................................... .. . 207
`3.0 ETCH MODELING .. .. .... .. ................................... ........ . 210
`3.1
`Ion Transport in Sheath .................................... ... 212
`3.2 Selection of Surface Transport Mechanism ...... .. 213
`3.3 Surface Reaction Kinetics ......................... ........ .. 214
`3.4 Simplifying Assumptions .... ............ .................... 215
`3.5 Modeling of Surface Re-emission ......... ... .. ......... 216
`3.6 Modeling of Surface Diffusion ........................... 217
`3.7 Numerical Methods ............................................. 219
`4.0 ETCH EXAMPLES .. .. ......... .......................................... 222
`5.0 DEPOSITION MODELING ......................................... 228
`6.0 DEPOSITION EXAMPLES .. .......... .............. .. .......... ... 233
`
`7
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`

`
`xxii Contents
`
`6
`
`7.0 REAL LIFE ................................................................... 237
`REFERENCES ...... ...................... ............................ ......... ..... 238
`
`The Role Of Metrology And Inspection In
`Semiconductor Processing .............................................. 241
`Mark Keefer, Rebecca Pinto, Cheri Dennison,
`and James Turlo
`1.0 OVERVIEW .................................................................. 241
`2.0
`INTRODUCTION TO METROLOGY AND
`INSPECTION .... ...... ... ............ .......................... ............. 242
`3.0 METROLOGY AND INSPECTION TRENDS:
`PAST, PRESENT, AND FUTURE .... ...... ....... ...... ....... 245
`3.1 Trends in Metrology ................ ...... ........ .............. 245
`3.2 Trends in Defect Inspection .... ............... ............. 246
`3.3 Trends in Inspection Strategies .. ... ....... ............... 250
`4.0 THEORY OF OPERATION, EQUIPMENT DESIGN
`PRINCIPLES, MAIN APPLICATIONS,
`AND STRENGTHS AND LIMITATIONS OF
`METROLOGY AND INSPECTION SYSTEMS ...... ... 255
`4.1
`Film Thickness Measurement ,Systems ..... .......... 256
`4.2 Resistivity Measurement Systems ....... .. .... .......... 261
`4.3
`Stress Measurement Systems ........ ................... ... 264
`4.4 Defect Inspection Systems ........ .......................... 269
`4.5 Automatic Defect Classification .................. ....... 277
`4.6 Defect Data Analysis Systems .................. ... ... .... 280
`GLOSSARY ....... ................................................................... 281
`REFERENCES .... ................... ............................................... 285
`
`7
`
`Contamination Control, Defect Detection, and
`Yield Enhancement in Gigabit Manufacturing ............ 287
`Suresh Bhat and Krishna Seshan
`1.0
`INTRODUCTION ......................................................... 287
`2.0 CONTAMINATION AND DEFECT GOALS
`FOR ULSI DEVICES .................................................... 289
`
`8
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`

`
`Contents
`
`xxiii
`
`300 SOURCES OF PARTICLES oooooooooooooooooooooooooooooooooooo ooooo 292
`400 CONTAMINATION AND DEFECT
`DETECTION: TOOLS OF THE TRADE 000000000000000 00 000 293
`Introduction oooooooooooooooooooooooooooooooooooooooooooooooooooo o o OOO 293
`401
`402 Non-Patterned (Bare) Wafer Surface Defect
`Detection oooooooooooooooooooo o oooo o o ooooooooooooooooooooooo o ooooooooooo 295
`Patterned Wafer Surface Defect Detection 0000 00000 297
`403
`500 ADVANCED TECHNIQUES FOR TRACE
`CONTAMINATION MONITORING 00000000 00 00 00 00 00 00 00 00 00 299
`Introduction 0000 0000 0000 0000 00 00 0 .. 00 000 00000 .. 0 0000000 0000 0 00 00 .. 00 0 299
`5 01
`502 Laser Light Scattering-Based In Situ Particle
`Detectors oooooooooooooo o oooo . . . . . . . . oooooo o ooOooooooooOooOooooooOoooooo 300
`503 Residual Gas Analyzers, Mass Spectrometry 00··· 300
`600 SUBSTRATE SURFACE PREPARATION
`TECHNIQUES 0 .... o ·oo 0 000 0 .. o 0 .. 0 ... o . . 0 0 .. 0 .. .. 0 ....... oo 00 0000 .. 00 .. 00 000 304
`Introduction .. 00 .. 00 ...... 00 000 .... 0 .. 00 .. 00 .. 00 .. oo . . ooooooooooooooo 304
`6.1
`602 Aqueous Chemical Cleaning and Etching 00000 .. 00 00 305
`6.3 Role of Organic Contamination 00 .. 00 ........ o 0000 ...... 0 305
`6.4 Summary ooo ooooooo 000 0 .... 0 .. o . . . o . . o . . . . . . . . . . . . . . . . . 0 ...... 0 0 ....... 0 307
`700 CHALLENGES TO ULSI (GIGABIT)
`CONTAMINATION CONTROL 000000000000 .. .................. 0 307
`7.1 Effect of People on Particle Density
`in Cleanrooms .. 0 00 00 00 00 00 00 0 .... 00 .......... 00 00 0 00 ...... 00 .. 0 .. 00 310
`800 PROCESS EVOLUTION ooooooooooooooooooooOOOOOOOO oooooo 0000 00 00 .. 00 311
`9.0 EVOLUTION OF CIRCUIT BASED
`ELECTRICAL DEFECT DETECTION 0000 00 00 ooo oo oOoo 000000 313
`1000 CONCLUSION 000000000000 ........ oo . . . . . . oooooooooooooo ooooooooooooooooooo 316
`ACKNOWLEDGMENT 00000 .. 00 000000 .... o. 000 0000 000 0000 0000 00 000 0000 ooo 0000 316
`REFERENCES 00 0000 .. 00 .. 0 ...... o . . oooooooooooooo 00000000000 .. 00 ..... 00 ... 0 00000000 317
`
`8
`
`Sputtering and Sputter Deposition ................................ 319
`Stephen Rossnagel
`INTRODUCTION oooooooo . . . oo . . . . . ooooooOOOoooooooo . . . . . . . . . . . . . . . . . . . . . . 319
`100
`200 PHYSICAL SPUTTERING THEORY ......................... 320
`2.1 Energy Dependence of Sputtering .00 ... 00 ...... 00.000000 321
`2.2 Energy and Direction of Sputtered Atoms .. 00 ...... 324
`
`9
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`

`
`xxiv Contents
`
`9
`
`3.0 PLASMAS AND SPUTTERING SYSTEMS ..... .. ....... 326
`4.0 DEPOSITION RATES AND EFFICIENCIES .... ... .... .. 335
`5.0 REACTIVE SPUTTER DEPOSITION ............ ... ....... .. 338
`6.0 SPUTTERING SYSTEMS ................................... ......... 344
`7.0 CONCLUSIONS AND FUTURE DIRECTIONS .. ..... . 347
`REFERENCES .................................................................. .... 348
`
`Laser and Electron Beam Assisted Processing ............. 349
`Cameron A. Moore, Zeng-qi Yu, LanceR. Thompson,
`and George J. Collins
`1.0
`INTRODUCTION ............... .. ........................................ 349
`2.0 BEAM ASSISTED CVD OF THIN FILMS .............. ... 351
`2.1 Conventional CVD Methods ... ....................... ... .. 351
`2.2 Electron Beam Assisted CVD .... .. ....................... 351
`2.3 Laser Assisted CVD ................... ......... ... ............. 352
`2.4 Experimental Apparati of Beam
`Assisted CVD ...................................................... 352
`2.5 Comparison of Beam Deposited Film
`Properties ...... ...... ................ ........................... ...... 354
`3.0 SUBMICRON PATTERN DELINEATION WITH
`LARGE AREA GLOW DISCHARGE PULSED
`ELECTRON-BEAMS ....................... .... .... ................... . 365
`4.0 BEAM INDUCED THERMAL PROCESSES ........... .. 368
`4.1 Overview ................................................ .............. 368
`4.2 Electron Beam Annealing oflon-lmplanted
`Silicon ......... ...... ... .. .............. ..... ... ................ .... .... 3 70
`4.3 Electron Beam Alloying of Silicides ................... 372
`4.4 Laser and Electron Beam Recrystallization
`of Silicon on Si02 ............................. ....... .. .............................. 374
`5.0 SUMMARY AND CONCLUSIONS .................... ........ 376
`ACKNOWLEDGEMENTS ................................................. .. 377
`REFERENCES .................................................. .... .......... ...... 377
`
`10
`
`

`
`Contents
`
`xxv
`
`10 Molecular Beam Epitaxy:
`Equipment and Practice .................................................. 381
`WalterS. Knodle and Robert Chow
`1.0 THE BASIC MBE PROCESS ....................................... 382
`2.0 COMPETING DEPOSITION TECHNOLOGIES ........ 385
`2.1 Liquid Phase Epitaxy .................................... ....... 386
`2.2 Vapor Phase Epitaxy and MOCVD ............... ...... 386
`3.0 MBE-GROWNDEVICES ............................................ 390
`3.1 Transistors ....................................................... .... 394
`3.2 Microwave and Millimeter Wave Devices ...... ... 396
`3.3 Optoelectronic Devices ....................................... 396
`3.4
`Integrated Circuits ............................................... 397
`4.0 MBE DEPOSITION EQUIPMENT ....................... .... ... 398
`4.1 Vacuum System Construction ............................. 399
`4.2 Sources ............................................................... .. 403
`4.3 Sample Manipulation ..................................... ..... 411
`4.4 System Automation .................................... ......... 412
`4.5 Performance Parameters ..................... ........ ...... ... 412
`5.0 PRINCIPLES OF OPERATION .................. .... ............. 415
`5.1
`Substrate Preparation ........................... .. ..... ........ . 417
`5.2 Growth Procedure ................................................ 419
`5.3
`In Situ Analysis .................................. ..... .. .. .... .... 425
`5.4 Materials Evaluation ............................................ 427
`5.5 Safety .................................. .. ............................... 431
`6.0 RECENT ADVANCES ............................................ ..... 431
`6.1 RHEED Oscillation Control ................................ 432
`6.2 GaAs on Silicon ................................................... 432
`6.3 Oval Defect Reduction ........................................ 434
`6.4 Chemical Beam Epitaxy/Gas Source MBE ......... 434
`6.5 Superlattice Structures ......................................... 437
`7.0 FUTURE DEVELOPMENTS ....................................... 439
`7.1
`Production Equipment ......................................... 439
`7.2
`In Situ Processing ................................................ 441
`7.3 Process Developments ......................................... 442
`7.4 Toxic Gases and Environmental Concerns ......... 444
`REFERENCES .......... ................................................... .. ....... 444
`
`11
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`xxvi Contents
`
`11
`
`Ion Beam Deposition .............. n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 463
`John R. McNeil, James J. McNally, and Paul D. Reader
`1.0
`INTRODUCTION ......................................................... 463
`2.0 OVERVIEW OF ION BEAM APPLICATIONS .... .... . 464
`2.1 Categories ofKaufman Ion Sources .............. .. .... 464
`2.2 Operational Considerations ................................. 467
`ION BEAM PROBING ........................................... .. .... 468
`3.0
`4.0 SUBSTRATE CLEANING WITH ION BEAMS .. ...... 471
`5.0 APPLICATIONS ........................................................... 475
`5.1
`Ion Beam Sputtering ............................................ 475
`Ion Assisted Deposition ..... ............. ............. ........ 483
`5.2
`5.3 Application Summary ..................................... ..... 496
`6.0 CONCLUDING COMMENTS ............................. ........ 497
`ACKNOWLEDGMENTS ................................. .................... 497
`REFERENCES ............................................................. .. ....... 497
`
`12 Chemical Mechanical Polishing ..................................... 501
`Kenneth C. Cadien
`1.0
`INTRODUCTION ........................... : ...... ............. .......... 501
`2.0 PROCESSING ............................................................... 503
`2.1 Oxide Polish .............................. ............. .. ........... 504
`2.2 STI Polish ............................................................ 506
`2.3 Tungsten Polish ................................................... 506
`3.0 POLISH EQUIPMENT ................................................. 507
`4.0 HISTORY ............................................ .. .. .. .................... 508
`5.0
`INNOVATIONS ............................................................ 509
`6.0 AUTOMATION ................................................... ......... 510
`7.0 WAFERIPADRELATIVEMOTION .............. ............ 510
`8.0 FUTURE CHALLENGES ..................................... .. .... . 510
`CONCLUSION ...................................................................... 511
`REFERENCES .............. .... ...... .............................................. 512
`
`12
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`
`Contents
`
`xxvii
`
`13 Organic Dielectrics in Multilevel Metallization
`of Integrated Circuits ...................................................... 513
`Krishna Seshan, Dominic J. Schepis, and
`Laura B. Rothman
`1.0 GENERAL INTRODUCTION .................. ................... 513
`2.0 HISTORICAL PERSPECTIVE .................................... 517
`3.0 FUNDAMENTAL CHEMISTRY OF ORGANIC
`DIELECTRICS ............................................................. . 524
`3.1 Materials Options ................................................ 524
`3.2 Polyimide Structure ............................................ . 527
`3.3 Depositing Polyimides ................ ...... .................. 53 1
`3.4 Moisture Absorption .......................................... .. 53 I
`3.5
`Solvent Effects ..................................................... 534
`3.6 Oxidation ............................................................. 535
`3.7 Dimensional Stability .......................................... 536
`3.8
`fvt.etal-Polymer Interactions ............................ .. ... 536
`3.9 Photosensitive Organic Dielectrics ................... .. 539
`3.10 Summary .............................................................. 540
`4.0 PROCESSING OF POLYMER FILMS ........................ 540
`4.1
`Substrate Preparation and Polyimide Coating .... 54 1
`4.2 Polyimide Adhesion ....................................... .... . 542
`4.3 Curing ofPolyimides ...................................... ..... 544
`4.4 Diffusion of Water ..... ............. .... .. ..... ........ .......... 544
`4.5 Summaty .............. ........................ ............. ....... .... 546
`5.0 PROCESS INTEGRATION WITH ORGANIC
`DIELECTRICS .................................................... .......... 546
`5.1
`Processes for Forming MLM Structures ..... ........ 54 7
`5.2 Patterning of Organic Dielectrics ................ ........ 5 51
`5.3
`Planarization ............................................. ........... 553
`5.4 Thetmal Budget Considerations .... .. ........ ............ 556
`5.5 Examples or Organic Dielectrics in
`Semiconductor Technologies ................... ...... ..... 558
`5.6 Summary ........................................ ...................... 560
`
`13
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`xxviii Contents
`
`6.0 RELIABILITY ... ..... ............ ... .... ......... ....... ................... 560
`6.1 Adhesion and Its Connection to Diffusion
`of Metal into Polyimide: The Interphase and
`Interface Stress ....... ........... .. ....... .... ............ ... ... .. . 561
`6.2 Effect of Moisture Ingress ................................... 568
`6.3 Mechanical ........................................................... 570
`6.4 Electrical Properties ............................................ 571
`6.5 Long Term Reliability ........................................ , 574
`6.6 Summary .............................................................. 576
`7.0 PERFORMANCE ADVANTAGES OF ORGANIC
`DIELECTRICS .............................................................. 576
`7.1
`Performance Comparisons .................................. 577
`7.2 Performance Conclusions .................................... 584
`7.3 Factors in the Ultimate Limits to Performance ... 584
`8.0 FUTURE TRENDS ............... ...... .. ........ .... ........ ....... .. ... 586
`REFERENCES ....... ... .............................. .............. ... ... .... ... ... 588
`
`14 Performance, Processing, and Lithography
`Trends
`............................................................................ 595
`Krishna Seshan
`1.0
`INTRODUCTION .. ........... ......... ................... ................ 595
`2.0 SCALING THE TRANSISTOR ... ............. ......... ..... ... .. 596
`3.0 LOW RESISTANCE: CHANGE TO
`COPPER-BASED METALLURGY ...... .... ........ ...... ..... 599
`4.0 TREND TO LOW K MATERIALS .............................. 601
`5.0 LITHOGRAPHY ANDPLANARIZATION ... ... ...... .. .. 603
`6.0 CHALLENGES TO CONTAMINATION/
`CLEANING ................................................... .... ............ 603
`6.1 Detection/Types of Contamination ..................... 603
`6.2 Trends in Integrated Processing ..... ... .. .... ... ... ... .. . 604
`7.0 SUMMARY ......................................... ....................... .. 606
`REFERENCES .............................................. .... ... ................. 606
`
`Index
`
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`14
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`3
`
`Chemical Vapor
`Deposition of Silicon
`Dioxide Films
`
`John Foggiato
`
`1.0
`
`INTRODUCTION
`
`The use of chemical vapor deposition for various insulator films is
`paramount in the fabrication of semiconductor devices. The initial use of
`such films for passivation led to the development of low temperature
`techniques for film deposition. With the availability of silane, the pyroly(cid:173)
`sis of silane in the presence of oxygen at atmospheric pressure provided
`the deposition mechanism. Further enhancements in film characteristics
`through the use of phosphorus as a dopant within the film allowed the film
`to provide gettering of impurities during wafer fabrication. This led to the
`need for "smoothing" the films, now known as rejlow, to minimize the
`sharp comers that metal lines had to cover. Reflow was further enhanced
`by the addition of boron as the dopant. This technology continues to be
`used today with better implementation of the reflow processes.
`With the addition of more than a single metal layer, dielectric films
`were needed for electrical isolation. These dielectrics had to be deposited
`at less than 400°C to prevent affecting the underlying metal layer. Initially,
`using silane at atmospheric pressure, suitable films could be formed. The
`
`111
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`15
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`

`
`112 Thin-Film Deposition Processes and Technologies
`
`advent of plasma enhanced film deposition enabled or improved dense film
`deposition. Low frequency power during deposition improved both the film
`deposition process and the film properties. Both atmospheric and plasma
`enhanced films are extensively used today.
`More recently, other reactants in the form of liquid precursors have
`been developed to provide other film properties, generally focused toward
`better step coverage. Although initially used at high deposition tempera(cid:173)
`tures (>650°C), today TEOS (tetraethylorthosilicate) is used as a precur(cid:173)
`sor in plasma enhanced deposition and for atmospheric pressure deposi(cid:173)
`tion with ozone. New precursors are being developed to deposit interlevel
`and intermetal dielectrics. As the technology drives towards 0.10 J.tm
`linewidths and gaps, better gap filling capabilities are needed and, as much
`as possible, dielectric films need an in-situ flow characteristic.
`This chapter focuses on the deposition of dielectric films suitable
`for interlevel and intermetal dielectrics. A brief review of future directions
`of dielectrics for DRAM memory cells is given. Starting with atmospheric
`deposition of films, the first portion of the chapter covers the history of
`this technology. Plasma enhanced CVD follows with a short overview of
`new techniques, including HDP (High Density Plasma), ECR (Electron
`Cyclotron Resonance) and photo enhanced deposition.
`After reviewing the basis for deposition for each of the technologies
`within their respective sections, current deposition methods are reviewed.
`The reaction mechanisms and the film characteristics that are obtained are
`given along with the basis by which the film properties are achieved.
`An important advancement in achieving the ability to reflow depos(cid:173)
`ited films came as a result of incorporating phosphorus as a dopant. Later
`optimizations included adding boron to form boron phosphorus silicon
`glass (BPSG). A review of the dopant incorporation mechanisms is given
`for this important step in enhancing integrated circuit reliability and
`manufacturability of smaller device geometries.
`In summarizing the chapter, film properties from the different tech(cid:173)
`nologies are compared, especially the film properties required for applica(cid:173)
`tions in integrated circuit manufacturing.
`
`2.0 OVERVIEW OF ATMOSPHERIC PRESSURE CVD
`
`The initial techniques for depositing films of Si02 employed atmo(cid:173)
`spheric pressure reactors (APCVD). Operating at atmospheric pressure,
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`16
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`

`
`Chapter 3: CVD of Silicon Dioxille Films
`
`113
`
`the reactor designs were simple, yet provided high deposition rates. By
`using silane (SiH4) and oxygen, injected as separate gases, the surface
`reaction on the heated wafer, typically at 400°C, grew films in the 2000 to
`3000 A/min range. The resultant films had suitable electrical characteris(cid:173)
`tics, however, due to gas phase reactions, the step coverage was poor.
`Examples of such coverage are shown in Figs. 1(a) to 1(c) with the
`notation that a "bread-loafing" effect appears as the film becomes thicker.
`Figure 1a illustrates the conformal deposition initially achieved, however
`with additional deposition (Fig. 1 b), the formation of the "bread-loafing"
`effect can be seen. With typical film thicknesses of 0.5 to 1.0 11m, narrow
`gaps will fill with a void (empty hole) forming as shown in Fig. 1 (c). With
`a better understanding of the reaction mechanisms