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CVD of Nonmetals

Edited by William S. Rees, Jr.

Weinheim . New York Base1 - Cambridge - Tokyo

This Page Intentionally Left Blank

William S. Rccs, Jr. (ed.)

CVD of Nonmetals

Related Reading

A.C. Jones, P. O’Brien CVD of Compound Semiconductors Precursor Synthesis, Development and Applications VCH, 1996, ISBN 3-527-29294-2

T. Kodas, M. Hampden-Smith The Chemistry of Metal CVD VCH, 1994, ISBN 3-527-29071-0

Chemical Vapor Deposition CVD provides a high-quality publication for chemists, physicists and engineers working on all aspects of CVD and related technologies. Published bimonthly as part of Advanced Materials, VCH, Vol. 2, 1996, ISSN 0935-9648

0 VCH Verlagsgesellschaft mbH. D-69451 Weinheim (Federal Republic of Germany), 1996

Distribution

VCH, P.O. Box 10 11 61, D-69451 Weinheim (Federal Republic of Germany)

Switzerland: VCH, P.O. Box, CH-4020 Basel (Switzerland)

USA and Canada: VCH, 220 East 23rd Street, New York, NY 10010-4606 (USA)

Japan: VCH, Eikow Building, 10-9 Hongo 1-chome, Bunkyo-ku, Tokyo 113 (Japan)

ISBN 3-527-29295-0

CVD of Nonmetals

Edited by William S. Rees, Jr.

Weinheim - New York - Base1 - Cambridge - Tokyo

Prof. William S. Rees, Jr. School of Chemistry and Biochemistry and School of Materials Science and Engineering Georgia Institute of Technology Altanta, GA, 30332-0400 USA

This book was carefully produced. Nevertheless, editor, authors and publisher do not war- rant the information contained therein to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

Published jointly by VCH Verlagsgesellschaft mbH, Weinheim (Federal Republic of Germany) VCH Publishers, Inc., New York, NY (USA)

Editorial Directors: Dr. Peter Gregory, Dr. Ute Anton Production Manager: Dip1.-Wirt.-Ing. (FH) Bernd Riedel

Library of Congress Card No. applied for.

A catalogue record for this book is available from the British Library.

Deutsche Bibliothek Cataloguing-in-Publication Data:

CVD of Nonmetals I ed. by William S. Rees, Jr. - Weinheim ; New York ; Base1 ; Cambridge ; Tokyo : VCH, 1996

NE: Rees, Jr., William S. [Hrsg.] ISBN 3-527-29295-0

0 VCH Verlagsgesellschaft mbH. D-69451 Weinheim (Federal Republic of Germany), 1996 Printed on acid-free and chlorine-free paper. All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form -by photoprinting, microfilm, or any other means - nor transmitted or translated into a machine-readable language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. Composition: Mitterweger Werksatz GmbH, D-68723 Plankstadt Printing: Strauss Offsetdruck GmbH, D-69509 Morlenbach Bookbinding: J. Schaffer GmbH & Co. KG., D-67269 Grunstadt Printed in the Federal Republic of Germany.

Preface

Chemical Vapor Deposition (CVD) is, perhaps, one of the most ancient of the scien- ces. Following the definition that a solid coating is prepared from a gaseous precursor by means of a chemical transformation, the charcoal cave paintings of prehistoric art, based on soot, fall into this category. CVD growth of carbon today forms the backbone of much of modern aerospace composites. Although CVD has become ever more complex for electronic applications, it enjoys a position of dominance for the large scale protective overlayering of decorative jewelry with TiN,. Thus, most individuals contact materials on an on-going basis that have been fabricated by CVD.

A work dealing with the simplest form of CVD, the growth of elemental metals, has been edited by Kodas and Hampden-Smith. The epitaxial preparation of compound semiconducting materials by CVD is presented in a book by O’Brien and Jones. The present work covers the area of non-metallic materials.

Historically, device architects were limited in their choices by the range of materials readily available at an attractive economic cost. Likewise, the materials choices often were dictated by what could be prepared in a high purity fashion from easily obtain- able chemicals. Thus, the entry of synthetic chemists into the arena of CVD, particularly those coupled closely to the electonics community, has changed the face of the field. It is becoming more typical today for the device design engineer to state the material required for achievement of a desired property, and, ultimately, to place the burden on the chemist to develop new compounds capable of forming such a composition.

The intent in producing this work was that it would prove both to be a useful reference to the practitioners in the field, as well as a good entry for the novice.

August 1996 William S. Rees, Jr.

Acknowledgments: The chapter authors each are deeply thanked for their effort to develop a high caliber, useful contribution. I am grateful to the chapter reviewers for their time invested in the book. Dr. Peter Gregory of VCH had the inspiration for a three volume series on CVD, the patience to make it a quality work, and the staff to follow through on the production. Mr. James Godard continues to provide excellent assistance to all aspects of my professional life. My wife, Phyllis Waite, and my child- ren, Bryce Alexander and Aerryn Elizabeth Rees, give the comparable boost to my personal life.

William S. Rees, Jr., presently a Full Profes- sor, received his American Chemical Society Certified B.Sc. degree from Texas Tech Uni- versity in 1980. After short stints in Vienna, Austria at the Palias Kinsky and at Cosden Oil and Chemical Company in Big Spring, Texas, he entered into graduate studies, back at Texas Tech University. Subsequent to a switch in schools, he obtained his Ph.D. in 1986 working with Professor M. Frederick Hawthorne at the University of California, Los Angeles. Following a postdoctoral fel- lowship with Professor Dietmar Seyferth at the Massachusetts Institute of Technology, he accepted a joint appointment on the faculty of the Department of Chemistry and the Materials Research and Technology Cen- ter at Florida State University, where he was promoted to Associate Professor in 1993. He moved to the Georgia Institute of Technol- ogy in January 1994, with a joint appointment between the School of Chemistry and Biochemistry and the School of Materials Science and Engineering. He was named the first Director of the Molecular Design Insti- tute in February, 1995.

Professor Rees’ research interests are in the synthesis and characterization of inorganic and organometallic compounds for use in the preparation of electronic materials. This research heavily draws upon the knowledge and techniques of the classical areas of inorganic, organic, physical and analytical chemistry, as applied to a variety of issues in the realm of materials science.

Contents

1 . Introduction William S . Rees. Jr .

1.1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.4.1 1.1.4.2 1.2 1.2.1 1.2.1.1 1.2.2 1.2.3 1.3 1.3.1 1.3.1.1 1.3.1.2 1.3.1.3 1.3.1.4 1.3.1.5 1.3.2 1.3.2.1 1.3.2.2 1.4 1.4.1 1.4.2 1.5 1.5.1 1.5.1.1 1.5.1.2 1.5.1.3 1.5.2 1.5.3 1.5.3.1 1.5.3.2 1.5.4 1.6 1.6.1

Organization of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Scope of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Potential Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Selection of Chapter Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Chapter Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Cross-References Between Chapters . . . . . . . . . . . . . . . . . . . . . . . 3 Where to Find a Topic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Uses of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electronic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Band Gap Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Optical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Structural Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Comparison of Deposition Techniques . . . . . . . . . . . . . . . . . . . . . . 5 Comparison of ChemicalVapor Deposition Sub-Techniques . . . . . . . . 5 Organometallic Vapor Phase Epitaxy (OMVPE) . . . . . . . . . . . . . . . 6 PlasmaCVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 PhotoCVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Pressure Modifications in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Comparison of Non-Chemical Vapor Deposition Technologies . . . . . . 9 9

10 10

11

Spray Pyrolysis Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Molecular Beam Epitaxy (MBE) . . . . . . . . . . . . . . . . . . . . . . . . . Other Physical Vapor Deposition Techniques . . . . . . . . . . . . . . . . . . General Comments on CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reactor Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Important Reaction Locations in CVD Reactors . . . . . . . . . . . . . . . Experimental Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System Reactant Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Reaction Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Reaction Co-Product Removal System . . . . . . . . . . . . . . . . . . . . . . 19 Handling of Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Methods of Energy Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Thermal CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Alternate Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Vapor Analysis in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Reaction Kinetics in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 General Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

X Contents

1.6.2 1.6.3 1.6.4 1.6.5 1.6.6 1.6.7 1.7 1.8 1.8.1 1.8.2 1.8.3 1.9

Vapor Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vapor-Solid Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solid Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control of Reaction Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rate-Determining Steps in CVD . . . . . . . . . . . . . . . . . . . . . . . . . Temperature and Growth Rate Effects . . . . . . . . . . . . . . . . . . . . . . Thermodynamics in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Comments on Precursors . . . . . . . . . . . . . . . . . . . . . . . . . Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Structural Motifs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanistic Insights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24 24 26 26 26 29 29 30 30 32 35 35

2 . Superconducting Materials Douglas L . Schulz and Tobin J . Marks

2.1 2.2 2.2.1 2.2.2 2.2.2.1 2.2.3 2.2.3.1 2.2.4 2.2.4.1 2.2.4.2 2.2.4.3 2.3 2.3.1 2.3.1.1 2.3.1.2 2.3.1.3 2.3.1.4 2.3.2 2.3.2.1 2.3.2.2 2.3.2.3 2.3.2.4

2.3.3 2.3.3.1 2.3.3.2 2.3.3.3 2.3.4 2.3.4.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Overview of Superconductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Physical Properties of Superconductors . . . . . . . . . . . . . . . . . . . . . 40 Low Temperature Superconducting Materials . . . . . . . . . . . . . . . . . 43 Crystal Structures of LTS Materials . . . . . . . . . . . . . . . . . . . . . . . . 43 High Temperature Superconducting Materials . . . . . . . . . . . . . . . . . 44 Crystal Structure of HTS Materials . . . . . . . . . . . . . . . . . . . . . . . . 44 Applications of Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . 48 Large-Scale Applications of Superconducting Magnets . . . . . . . . . . . 48 Low-Field Applications of Superconductors . . . . . . . . . . . . . . . . . . 49 Superconducting Electronics Applications . . . . . . . . . . . . . . . . . . . . 50 CVD of LTS Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Nb3Sn CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Nb3Sn CVD Precursors and Reaction Schemes . . . . . . . . . . . . . . . . 53 Nb3Sn CVD Reactor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Substrates for Nb3Sn CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

55 Nb3Ge CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Nb3Ge CVD Precursors and Reaction Schemes . . . . . . . . . . . . . . . . 56 Nb3Ge CVD Reactor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

57

CVD-Derived Nb3Ge Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 NbC1, Ny CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . NbC1-yNy CVD Precursors and Reaction Schemes . . . . . . . . . . . . . . Reactor Design for CVD of NbC1, N, on Carbon Fiber . . . . . . . . . . . Physical Properties of CVD-Derived NbCI, Ny Films . . . . . . . . . . . .

Physical Properties of CVD-Derived Nb3Sn Films . . . . . . . . . . . . . .

Physical Properties of CVD-Derived Nb3Ge Films . . . . . . . . . . . . . . Effects of Chemical Doping Upon Physical Properties of

59 60 61 62 62 63

NbN CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NbN CVD Precursors and Reaction Schemes . . . . . . . . . . . . . . . . .

Contents XI

2.3.4.2 2.3.5 2.3.5.1 2.3.5.2 2.3.5.3 2.3.5.4 2.3.5.5 2.3.5.6 2.3.5.7 2.3.5.8

2.3.6 2.4 2.4.1 2.4.1.1 2.4.1.2 2.4.1.3 2.4.2 2.4.2.1 2.4.2.2 2.4.2.3 2.4.2.4 2.4.2.5 2.4.2.6 2.4.2.7 2.4.2.8 2.4.2.9 2.4.3 2.4.3.1 2.4.3.2 2.4.3.3 2.4.3.4 2.4.3.5 2.4.3.6 2.3.4.7 2.4.3.8 2.4.4 2.4.4.1 2.4.4.2 2.4.4.3 2.4.4.4 2.4.4.5 2.5 2.6

Physical Properties of CVD-Derived NbN Films . . . . . . . . . . . . . . . 63 CVD of Other LTS Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Nb3Si CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 V3Si CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 V3Ge CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Nb3Ga CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Tic1, N, CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Wl, Ge, CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Ta CVD Film Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 LTS Film Growth by CVD of Hydrides and Organometallics on HotWires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Thermodynamic Analysis of LTS CVD . . . . . . . . . . . . . . . . . . . . . . 67 CVD of HTS Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 CVD Precursor Design Strategies for HTS Materials . . . . . . . . . . . . 68 Metal p-Diketonate Complexes for HTS CVD . . . . . . . . . . . . . . . . 69 Limitations of Alkaline Earth @-Diketonate Complexes for HTS CVD . 71 New Barium Precursors for CVD of HTS Materials . . . . . . . . . . . . . 71 CVDofYBCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Compositional Analysis of CVD-Derived YBCO Films . . . . . . . . . . . 74 Structural Orientations of YBCO Films by CVD . . . . . . . . . . . . . . . 78 Low Temperature CVD of YBCO Using N20 as a Reactant Gas . . . . . 83 Plasma-Enhanced CVD of YBCO . . . . . . . . . . . . . . . . . . . . . . . . . 84 CVD of YBCO Films Using Other Precursors . . . . . . . . . . . . . . . . . 85 Alternative Precursor Delivery Systems . . . . . . . . . . . . . . . . . . . . . 87 CVD Processing of Technologically Related YBCO Films . . . . . . . . . 90 CVD of YBa2Cu408 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Thermodynamic Analysis of YBCO CVD . . . . . . . . . . . . . . . . . . . . 92 CVD of BSCCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 In Situ CVD Growth of BSCCO . . . . . . . . . . . . . . . . . . . . . . . . . . 112 BSCCO Films by CVD Using Fluorinated Metal-Organic Precursors . . 115 Doping Studies in the CVD of BSCCO Thin Films . . . . . . . . . . . . . . 116 CVD of BSCCO on Novel Substrates . . . . . . . . . . . . . . . . . . . . . . 117 Novel BSCCO Film Orientations . . . . . . . . . . . . . . . . . . . . . . . . . 117 Novel CVD Routes to BSCCO Thin Films . . . . . . . . . . . . . . . . . . . 118 Halide CVD of BSCCO Thin Films . . . . . . . . . . . . . . . . . . . . . . . . 119 Thermodynamic Analysis of BSCCO CVD . . . . . . . . . . . . . . . . . . . 120 CVD of TBCCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 CVD of TBCCO Thin Films on Single Crystal Substrates . . . . . . . . . . 121 CVD of TBCCO Thin Films on Metallic Substrates . . . . . . . . . . . . . 128 Doping Studies for CVD of TBCCO Thin Films . . . . . . . . . . . . . . . . 129 Mist Microwave-Plasma CVD of (TI, Pb)-Sr-Ca-Cu-0 Films . . . . . . 129 Thermodynamic Analysis of TBCCO CVD . . . . . . . . . . . . . . . . . . . 129 CVD of HTS Lattice-Matched Metal Oxides . . . . . . . . . . . . . . . . . . 132 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

XI1 Contents

3 . Chemical Vapor Deposition of Conducting Materials Tobias Gerfin and Klaus-Hermann Dahmen

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 3.2 Deposition Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 3.3 Nontransparent Conducting Films . . . . . . . . . . . . . . . . . . . . . . . . . 155 3.3.1 Titanium Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 3.3.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 3.3.1.2 Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 3.3.1.3 Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 3.3.2 Other Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 3.3.2.1 Film Deposition Using Halides . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 3.3.2.2 Film Deposition Using Metal-Organic Precursors . . . . . . . . . . . . . . . 171 3.3.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 3.4 Transparent Conducting Films . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 3.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 3.4.2 Indium Oxide Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 3.4.2.1 Precursors and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 3.4.2.2 Properties and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 3.4.3 Tin Oxide Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 3.4.3.1 Preparation and Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 3.4.3.2 Properties and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 3.4.4 Zinc Oxide Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 3.4.4.1 Precursors and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 3.4.4.2 Properties and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 3.4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

4 . Semiconducting Materials Gary S . Tompa

4.1 4.2

Introduction to Semiconductors and Formation Technology . . . . . . . . . 194 The Growth Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

4.2.1 Competing Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 4.2.1.1 Liquid Phase Epitaxy (LPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 4.2.1.2 Implantation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 4.2.1.3 Molecular Beam Epitaxy (MBE) . . . . . . . . . . . . . . . . . . . . . . . . . . 199 4.2.1.4 Vapor Phase Epitaxy (VPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 4.2.1.5 Others . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 4.2.2 Organometallic Vapor Phase Epitaxy (OMVPE) . . . . . . . . . . . . . . . . 204 4.2.3 4.2.3.1 Reactor History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 4.2.3.2 Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 4.2.3.3 Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 4.2.3.4 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 4.2.3.5 Assisted Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

Organometallic Vapor Phase Epitaxy (OMVPE) System Technology . . . 208

Contents XI11

4.2.3.6 The Deposition Equipment Manufacturers . . . . . . . . . . . . . . . . . . . . 223 4.2.3.7 Cost of Ownership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 4.2.3.8 Choice of Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 4.3 The Substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 4.4 The Reactants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 4.4.1 The Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 4.4.2 The Metal-Organics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 4.4.3 Organometallic Source Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 4.4.4 Reactant Efficiencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 4.5 The Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 4.5.1 Group 11-VI Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 4.5.2 Group 111-V Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 4.5.3 Group 111-V Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 4.5.4 Group IV-IV Materials Silicon, Silicon germanium . . . . . . . . . . . . . . 239 4.5.5 Carbides (Including and Diamond) . . . . . . . . . . . . . . . . . . . . . . . . . 240 4.5.6 Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 4.5.7 Organic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 4.5.8 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 4.6 The Device Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 4.6.1 Field Effect Transistors (FETs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 4.6.2 Heterojunction Bipolar Transistors (HBTs) . . . . . . . . . . . . . . . . . . . . 244 4.6.3

Effect Transistors [(HEMTs (MODFETs)] . . . . . . . . . . . . . . . . . . . . 245 4.6.4 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 4.6.5 Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 4.6.6 Photodiode Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 4.6.7 Solar Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 4.6.8 High Temperature Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 4.6.9 4.7 The Future Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 4.7.1 Selective Area Epitaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 4.7.2 Atomic Layer Epitaxy (ALE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 4.7.3 Real-Time In-Situ Process Monitoring . . . . . . . . . . . . . . . . . . . . . . . 256 4.7.4 Alternative Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 4.7.5 Large Area Production Technology . . . . . . . . . . . . . . . . . . . . . . . . . 257 4.7.6 Insights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 4.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

High Electron Mobility Transistors (Modulation Deped Field

111-V Integrated circuits, Opt0 Electronic Integrated Circuits (OEICs) . 253

5 . CVD of Insulating Materials Andrew R . Barron

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 5.2 Applications for Electrically Insulating Materials . . . . . . . . . . . . . . . 262 5.2.1 Device Isolation and Gate Insulation . . . . . . . . . . . . . . . . . . . . . . . 263

XIV Contents

5.2.2 Passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 5.2.3 Planarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 5.3 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 5.3.1 Deposition Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 5.3.2 Deposition Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 5.3.3 Precursor Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

5.4.1 Silicon Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 5.4.1.1 Silica (SiOz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 5.4.1.2 Silicate Glasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 5.4.2 Aluminium Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 5.4.2.1 Alumina (A1203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 5.4.2.2 Aluminum Silicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 5.4.3 Transition Metal Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 5.4.3.1 Tantalum and Niobium Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 5.4.3.2 Titanium, Zirconium and Hafnium Oxide . . . . . . . . . . . . . . . . . . . . 292 5.4.4 5.5 Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 5.5.1 Silicon Nitride and Oxynitride . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 5 . 5 . 2 Aluminum Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 5.5.3 Transition Metal Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 5.6 Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 5.6.1 Gallium Sulfide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 5.6.2 Indium Sulfide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 5.7 Fluorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 5.8 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

5.4 Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

Superconducting Metal Oxide (SMO) Lattice-Matched Insulators . . . . 294

6 . Structural Ceramic Coatings and Composites W Jack Lackey

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 6.2 Fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 6.2.1 Current Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 6.2.2 Reactor Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 6.2.3 Stress in Coated Fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 6.2.4 Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 6.2.5 Economic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 6.3 Interface Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

Types of Interface Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Layered Oxide Structures as Interfaces . . . . . . . . . . . . . . . . . . . . . 342 CVD of Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Textured CVD Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 CVD of Alumina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Porous Interface Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

6.3.1 6.3.2 6.3.3 6.3.3.1 6.3.3.2 6.3.3.3

Contents XV

6.3.3.4 Coatings of p-Alumina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 6.4 Composite Consolidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 6.4.1 Chemical Vapor Infiltration of Carbon . . . . . . . . . . . . . . . . . . . . . . 350 6.4.2 Chemical Vapor Infiltration of Silicon Carbide . . . . . . . . . . . . . . . . . 360 6.4.3 Chemical Vapor Infiltration of Alumina . . . . . . . . . . . . . . . . . . . . . 361 6.4.4 Chemical Vapor Infiltration of Zirconium Oxide2 . . . . . . . . . . . . . . . 361 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

7 . Other Materials Gertrud E . Krauter and William S . Rees. Jr .

7.1 7.1.1 7.1.1.1 7.1.1.2 7.1.1.3 7.1.2 7.2 7.2.1 7.2.1.1 7.2.1.2 7.2.1.3 7.2.1.4 7.2.1.5 7.2.1.6 7.2.1.7 7.2.2 7.2.2.1 7.2.2.2 7.2.2.3 7.2.3 7.3 7.3.1 7.3.1.1 7.3.1.2 7.3.2 7.3.2.1 7.3.2.2 7.3.2.3 7.4 7.4.1 7.4.2 7.4.3 7.4.4 7.4.5

Halides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Fluorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Group 1 Fluorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Group 2 Fluorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 Transition Element Fluorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 Metal Iodides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 Metal Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 Transition Element Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 Titanium, Zirconium and Hafnium Oxides . . . . . . . . . . . . . . . . . . . 372 Vanadium. Niobium and Tantalum Oxides . . . . . . . . . . . . . . . . . . . 373 Chromium. Molybdenum and Tungsten Oxides . . . . . . . . . . . . . . . . 373 Iron and Ruthenium Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 Cobalt Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Nickel Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Zinc Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Main Group Element Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Antimony Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Indium Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Thallium Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 Rare Earth Element Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 Metal Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 Transition Element Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 Titanium Sulfide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 Molybdenum and Tungsten Sulfides . . . . . . . . . . . . . . . . . . . . . . . . 378 Main Group Element Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 Group 2 Element Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 Group 14 Element Sulfides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 Arsenic Sulfide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Metal Selenides and Tellurides . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Indium Selenide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Germanium Selenide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Tin Selenide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Arsenic Selenide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Antimony and Bismuth Tellurides . . . . . . . . . . . . . . . . . . . . . . . . . 380

XVI Contents

7.5 Metal Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Transition Element Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Titanium, Zirconium and Hafnium Nitrides . . . . . . . . . . . . . . . . . . 381 Vanadium, Niobium and Tantalum Nitrides . . . . . . . . . . . . . . . . . . . 382

7.5.1.3 Tungsten Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382 Main Group Element Nitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . 383

7.5.2.1 Magnesium Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 7.5.2.2 Carbon Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 7.5.2.3 Germanium Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 7.5.2.4 Phosphorus Nitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 7.6 Metal Carbides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 7.6.1 Transition Element Carbides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384 7.6.1.1 Titanium, Zirconium and Hafnium Carbides . . . . . . . . . . . . . . . . . . 384 7.6.1.2 Vanadium, Niobium and Tantalum Carbides . . . . . . . . . . . . . . . . . . 384 7.6.1.3 Chromium, Molybdenum and Tungsten Carbides . . . . . . . . . . . . . . . 385 7.6.2 Main Group Element Carbides . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 7.6.2.1 Boron Carbide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 7.7 Elemental Boron and Metal Borides . . . . . . . . . . . . . . . . . . . . . . . 386 7.7.1 Elemental Boron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 7.7.2 Metal Borides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387 7.7.2.1 Titanium, Zirconium and Hafnium Borides . . . . . . . . . . . . . . . . . . . 387 7.7.2.2 Niobium and Tantalum Borides . . . . . . . . . . . . . . . . . . . . . . . . . . 388 7.7.2.3 Molybdenum and Tungsten Borides . . . . . . . . . . . . . . . . . . . . . . . . 388 7.8 Complex Ceramic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 7.8.1 Metal Carbonitrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 7.8.1.1 Boron-Carbon-Nitrogen Compounds . . . . . . . . . . . . . . . . . . . . . . 389 7.8.1.2 Titanium and Zirconium Carbonitrides . . . . . . . . . . . . . . . . . . . . . 389 7.8.1.3 Niobium Carbonitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 7.8.1.4 Molybdenum Carbonitride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 7.8.2 Titanium Silicocarbide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 7.8.3 Spinels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 7.8.4 Garnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 7.8.5 Other Magnetic Metal Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 7.8.6 Other Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

7.5.1 7.5.1.1 7.5.1.2

7.5.2

List of Contributors

Andrew R. Barron Department of Chemistry Rice University PO Box 1892 Houston, TX 77251 USA

Klaus-Hermann Dahmen Department of Chemistry and Center of Materials Research and Technology (MARTECH) Florida State University Tallahassee, FL 32306-3006 USA

Tobias Gerfin Institut de Chimie Physique Ecole Polytechnique FCdCrale CH-1015 Lausanne

Gertrud E. Krauter Max-Planck-Institut fur Mikrostrukturphysik Weinberg 2 06120 Halle/Saale Germany

W. Jack Lackey Georgia Tech Research Institute Atlanta, GA 30332-0826 USA

Tobin J. Marks Department of Chemistry and the Science and Technology Center for Superconductivity Northwestern University 2145 N. Sheridan Road Evanston, IL 60208-3113 USA

William S. Rees, Jr. School of Chemistry and Biochemistry and School of Materials Science and Engineering Georgia Institute of Technology Atlanta, GA 30332-0400 USA

Douglas L. Schulz National Renewable Energy Laboratory 1617 Cole Boulevard Golden, CO 80401-3393 USA

Gary S. Tompa Structured Materials Industries, Inc. 681 Dover Court Somerville, NJ 08876 USA

1 . Introduction William S . Rees. J r.

Contents

1.1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.4.1 1.1.4.2 1.2 1.2.1 1.2.1.1 1.2.2 1.2.3 1.3 1.3.1 1.3.1.1 1.3.1.2 1.3.1.3 1.3.1.4 1.3.1.5 1.3.2 1.3.2.1 1.3.2.2 1.4 1.4.1 1.4.2 1.5 1.5.1 1.5.1.1 1.5.1.2 1.5.1.3 1.5.2 1.5.3 1.5.3.1 1.5.3.2 1.5.4

Organization of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Scope of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Potential Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Selection of Chapter Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Chapter Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Cross-References Between Chapters . . . . . . . . . . . . . . . . . . . . . . . 3 Where to Find a Topic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Uses of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electronic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Band Gap Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Optical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Structural Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Comparison of Deposition Techniques . . . . . . . . . . . . . . . . . . . . . . 5 Comparison of Chemical Vapor Deposition Sub-Techniques . . . . . . . . 5 Organometallic Vapor Phase Epitaxy (OMVPE) . . . . . . . . . . . . . . . 6 PlasmaCVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 PhotoCVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Pressure Modifications in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Spray Pyrolysis Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Comparison of Non-Chemical Vapor Deposition Technologies . . . . . . 9 Molecular Beam Epitaxy (MBE) . . . . . . . . . . . . . . . . . . . . . . . . . 9 Other Physical Vapor Deposition Techniques . . . . . . . . . . . . . . . . . . 10 General Comments on CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Reactor Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Important Reaction Locations in CVD Reactors . . . . . . . . . . . . . . . 10 Experimental Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Reaction Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Reaction Co-Product Removal System . . . . . . . . . . . . . . . . . . . . . . 19 Handling of Precursors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Methods of Energy Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Thermal CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Alternate Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Vapor Analysis in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

System Reactant Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2 I Inirodriction

1.6 1.6.1 1.6.2 1.6.3 1.6.4 1.6.5 1.6.6 1.6.7 1.7 1.8 1.8.1 1.8.2 1.8.3 1.9

Reaction Kinetics in CVD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 General Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Vapor Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Vapor-Solid Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Solid Phase Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Control of Reaction Location. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Rate-Determining Steps in CVD . . . . . . . . . . . . . . . . . . . . . . . . . 27 Temperature and Growth Rate Effects. . . . . . . . . . . . . . . . . . . . . . 29 Thermodynamics in CVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 General Comments on Precursors. . . . . . . . . . . . . . . . . . . . . . . . . 30 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Structural Motifs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Mechanistic Insights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

1.1 Organization of the Book

This book is intended to cover most aspects of chemical vapor deposition of nonmetal- lic materials. As such, it is organized primarily along the lines of band gap variation in electronic materials, followed by nonelectronic materials. The material is constructed from the smallest band gap-superconducting materials, through intermediate band gaps-conducting and semiconducting materials, and concluding with the largest band gap-insulating materials. Additionally, structural materials and a final chapter, encom- passing compositions which do not neatly fit within earlier sections, form the conclusion of the work. In general, the emphasis has been on the ability to deposit a specific composition of a material. As such, a heavy reliance has been made on tables for com- piling exhaustive lists of earlier literature reports. This is a work which is aimed at an audience broadly comprised of chemists, physicists, chemical engineers, materials scientists, and hands-on electrical engineers involved in the general practice of growth of thin films.

1.1.1 Scope of the Book

Most types of materials which have been deposited by chemical vapor deposition are included in this work. A more specialized compilation of work only on semiconducting materials is also available from VCH [l]. Lastly, a specialized effort examining chemical vapor deposition of elemental metallic films has also been published by VCH [2]. Chemical vapor deposition of organic materials is not present in this text. Additionally, chemical vapor deposition of optical materials is not split out as an independent chapter; rather, it has been enfolded into the presentations of several chapters within the reference work.

1.2 Uses of Materials 3

1.1.2 Potential Audience

The intended audience ranges from synthetic organic and organometallic chemists, to electronic device design architects who are searching for specific materials properties of a given composition. It is intended that the work be a handbook of particular use to those directly involved in the growth of films.

1.1.3 Selection of Chapter Topics

The coverage of this work expands beyond those of other VCH publications on The Chemistry of Metal C V D [2] and C V D of Conzpound Semicoriductors [ 11, and, as an umbrella work, give a feel for the broad and diverse area of chemical vapor deposition of materials, its ramifications into a variety of important technological arenas, and the "how to" of specific processes.

1.1.4 Chapter 0 rg a n i za t i o n

1.1.4.1 Cross-References Between Chapters

Although substantial effort has been invested in securing adequate cross-referencing between specific chapters within the work, inevitably omissions will be located by the astute reader. I t is hoped that they will be brought to the attention of the editor, for correction in the printing of subsequent editions. Most importantly, no effort has been made to particularly curtail components of particular chapters. Thus, one may find the specifics of reactor design in individual chapters, as well as the operating parameters which are unique to a given composition. These discussions are juxtaposed in the text with a treatment of how to deposit individual detailed compositions.

1.1.4.2 Where to Find a Topic

The index has been exhaustively compiled by three different groups. The original inclusion by each individual chapter author has been further checked by both the editor and the VCH publications office. Therefore, we encourage the reader to take great advantage of the index in finding specific areas within the work.

1.2 Uses of Materials

The overall construct of the volume has been to group individual materials by their ultimate use. As such, some compositions may be found in more than one section;

4 1 Introduction

nevertheless, it should lead to a more expedient cross-search for a particular composition for a given utilization. The reader is encouraged to weigh the particular construct of a given chapter against their specific use. For example, not all sub-techniques of chemical vapor deposition are equally applicable to all materials compositions. There- fore, individual chapter authors have augmented the techniques section with hints for a particular materials class.

1.2.1 Electronic Applications

The bulk of chemical vapor deposition, in terms of dollars of ultimate market, is directed to electronic applications. Although low cost added, high volume, applications may be found in structural ceramics, the high value added, multi-use environment of electronic materials has driven much of the search for advances in chemical vapor deposition.

1.2.1.1 Band Gap Classifications

As mentioned above, the work has been divided in electronic materials subsets accord- ing to the band gap: small gap, mid gap, and large gap materials. These concepts should be quite familiar to physicists who have studied band theory. This concept also is a direct extrapolation for chemists, who are familiar with the molecular orbital concept of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for molecules. Thus, in a molecular to solid state transition, one may roughly equate the HOMO-LUMO separation with the band gap.

1.2.2 Optical Applications

There are several opportunities in specific chapters for the reader to glean information related to optical applications of materials. As such, no particular chapter has been devoted to this topic. Particular care has been placed toward construction of the index in this regard.

1.2.3 Structural Applications

As alluded to above, large volume production of structural materials occurs by chemical vapor deposition in the industrial arena. Although, in general, it is not highly sophisticated chemistry which is employed in these materials, and they are, on the whole, fairly well understood, it is nevertheless a large segment of the overall nonme- tallic CVD market. Additionally, decorative coatings may fall under this general category. It is pointed out that titanium nitride - "fake gold" - is produced by chemical

1.3 Comparison of Deposition Techniques S

vapor deposition on a multisquare kilometer per year scale internationally. However, i t lends little to the structural support of the underlying substrate, and purely adds an aesthetic value to the material at a greatly reduced cost to electroplating with precious metals. Therefore, in the definition for this work, “structural” will comprise most nonelectronic uses.

1.3 Comparison of Deposition Techniques

The interested reader is referred to Bunshah’s book on comparative thin film growth sub-techniques [3]. In general, chemical vapor deposition is selected for its application as a non-line-of-sight, high throughput, and low cost per unit, processing technology. The competing technologies which employ ultra high vacuum conditions, e. g., molecular beam epitaxy and related techniques, generally are higher cost capital investment items, and lower throughput per unit time production techniques. Techniques such as sputtering and laser ablation generally are thought to be unapplicable to large substrate areas in a manufacturing environment. Therefore, for very large substrate area, non-line-of-sight, and uniform thickness and elemental composition coverage, it is chemical vapor deposition which has emerged as the premier candidate for thin film growth.

1.3.1 Comparison of Chemical Vapor Deposition Sub- Techniques

This general area is filled with an alphabet soup morass of acronyms, only a few of which will be addressed here. The interested reader is particularly directed to the introduction of Stringfellow’s book [4]. His work is directed exclusively at the compound semiconductor market, nevertheless it includes an exceptional discussion of the kinetics and thermodynamics of chemical vapor deposition processes in general. Additio- nally, a good chemical introduction is included in The Chemistry of Metal CVD [2]. Also, Jensen and Hitchman’s book on chemical vapor deposition has an outstanding introduction to the background of the field, its historical perspective, and the prospects for continued growth in the area [S].

Several chemical vapor deposition techniques have been employed for the growth of a variety of materials, including chloride vapor phase epitaxy (CIVPE), hydride vapor phase epitaxy (HVPE), and organometallic vapor phase epitaxy (OMVPE). Each technique has intrinsic strengths and weaknesses, as well as specific advantages for specific applications. In general, the term chemical vapor deposition (CVD) has been employed widely to describe all processes which result in a coating from a chemical reaction emanating from vapor phase precursors. The subset of these processes producing epitaxial growth of layers upon substrates has been coined VPE (vapor phase epitaxy). Consistent with traditional chemical nomenclature, organometallic (OM) is prefixed to an acronomy when the source molecules possess direct metal-carbon

6 I Introduction

bonding interactions. Accepted alternatives include MO to define any precursor having an organic-containing ligand on a metal core (e. g., amides, alkoxides, P-dike- tonates, etc.)

1.3.1.1 Organometallic Vapor Phase Epitaxy (OMVPE)

As mentioned above, CVD, the most general term describing the deposition process, implies nothing about the crystallinity of the grown layer. Epitaxy is directed at single crystal layers on single crystal substrates. Vapor phase epitaxy (VPE) was coined to parallel liquid phase epitaxy (LPE).

The term organometallic describes precursors which contain a direct metal-carbon interaction, be it o or JC in nature. This is in parallel with traditional chemical nomenclature. Metalorganic, in contrast, now is accepted widely as the description for any metalorganic containing ligand precursor for CVD. This includes, for example, metal alkoxides and metal amides. The metal carbonyl work of Mond, last century, is one early example of OMCVD.

OMVPE research on semiconducting materials began with the work of Manasevit in the late 1960s, when VPE and LPE already were well-developed epitaxial growth techniques [6]. Since the OMVPE process is complex, development proceeded somewhat more slowly than for the much simpler MBE technique. As recent as fifteen years ago, an unsettled issue was whether MBE or OMVPE ultimately would be the dominant technique for production of compound semiconductor materials for commercial device processing. The issues of merit were related to purity and inherent limits on interface abruptness, with the early edge going to MBE. Today these obstacles have been overcome. In general, contemporary devices produced by MBE and OMVPE possess comparable performance characteristics. The prime attractions of OMVPE, relative to other techniques, are its suitability for large-scale production applications and versatil- ity. OMVPE unquestionably is the simplest, most cost-effective, most versatile technique: virtually all semiconductor compounds and alloys can be produced, “dial a die- lectric” is on the horizon, optical coatings can be accomplished on many square meters of substrate with rigorous thickness and composition control, and entire cluster tools designed around CVD for intricate device designs are available commercially at the present time.

The “potential” of CVD has begun to bear fruit in many areas. The process ability to rapidly coat non-planar objects in a cost-effective manner has contributed to a rapid rise in the adaptation of the technique. For example, solar cells and layers now are rou- tinely fabricated by CVD approaches. Additionally, “synthetic gold” coatings (off-stoi- chiometry TiN) are put down for cosmetic reasons on large volumes of personal jewelry. The scratch-resistant material makes for a tough outer shell at an exception- ally attractive economic cost.

Despite these successes, several problems remain, including the need for expensive reactants and the large number of parameters that must be controlled precisely to obtain the necessary uniformity and reproducibility for microelectronic and optoelectronic applications. Additional challenges to overcome include the use of hazardous materials and the generation of a substantial volume vapor phase waste stream.

1.3 Comparison of Deposition Techniques 7

1.3.1.2 Plasma CVD

One method which has been investigated extensively and applied widely over the last decade is plasma-enhanced CVD (PECVD). Many CVD processes employing plasmas still require substrate heating, since plasma temperatures typically are several hundred degrees lower than those demanded for conventional CVD. Thus, the technique often is known as plasma-enhanced CVD (PECVD) or plasma-assisted CVD (PACVD).

Although PECVD can address issues associated with substrate-epilayer thermal stress, the CVD modification presents its own unique set of obstacles to the researcher. Plasmas are extraordinarily complex mixtures and deposition characteristics depend strongly on gas pressure, flow rate, RF power and frequency, reactor geometry and substrate temperature. I n PECVD, i t frequently is challenging to achieve control over ultimate film properties. Additionally, the substrate is bombarded with energetic neu- tral and charged particles, causing chemical and physical damage. The realization of these substantial issues has prompted investigators to explore alternate, non-pyrolytic, means of achieving epitaxial growth on thermally sensitive substrates.

1.3.1.3 Photo CVD

Higher frequency radiation, used in CVD processes, has been termed photochemical, photosensitized, photoassisted or, collectively photo CVD. A simple fact of chemistry demands that, in order for radiation to interact with either a vapor phase entity or a surface adsorbed moiety, there must be energy absorption by the molecule. Reactants traditionally employed in CVD processes have been simple inorganic species demand- ing ultraviolet (UV) radiation. Alternatively, modification by introduction of an appropriate secondary reactant to the system, acting as a photosensitizing agent, has been practiced. The increasing interest in organometallic precursors with pi- as well as sig- ma-bonded moieties opens up the possibility of using a wider range of light sources for photo CVD. A potential disadvantage accompanies this new motif in precursor design. I n general, the higher the level of unsaturation present in a source molecule, the greater the probability for incorporation of carbon into the epilayer derived from it. This often is not merely an inconvenience, frequently i t may prove to be unrecover- able. Thus, caution here outlines the highly interwoven interplay exhibited by variables in complex CVD processes. Attempts to rectify a perceived problem often lead to major adverse consequences elsewhere in the process.

Whatever the wavelength used, however, important features of photo CVD are the potential for significant lowering of deposition temperatures, compared with thermal CVD, and the low substrate damage compared with plasma CVD. Another advantage of photo CVD over both thermal and plasma CVD is the possibility of maintaining a well-defined reaction volume by using either appropriate optical focusing arrange- ments or by using lasers, introducing the possibility of localized deposition - with scan- ning - to produce direct, maskless three-dimensional pattern generation. The use of lasers with high power output offers the opportunity of rapid rastering with the in- creased reaction (and deposition) rates which potentially are achievable. A final im-

8 I Introduction

portant feature of photo CVD is that monochromatic radiation offers the potential for minimizing deleterious side reactions.

However, like MBE, photo CVD is being studied today predominately at the research level, and, although the approach has been used for some specific applications, to date the technique has yet to be fully exploited for commercial implementation. This partially may be attributed to the perceived lower quality of photo CVD films, but i t is also due undoubtedly to the realization that the drawbacks inherent in traditional CVD have not yet been sufficiently serious to merit the focused development of alternate technologies. As problems associated with high temperature deposition become more critical, particularly for microelectronic and optoelectronic applications, photoassisted processes may have a larger role in the preparation of thin films by CVD, especially if coupled with specifically designed precursors. Two noteworthy examples fall into this category. In the first, intricate three-dimensional constructs have been fabricated by laser CVD. Likewise, in some specific processes, substrate temperature has an intrinsic upper limit that presently falls below the temperature demanded for growth of a high quality epilayer.

1.3.1.4 Pressure Modifications in CVD

The typical motive for investigating pressure regime changes in chemical vapor deposition is to ensure either greater uniformity of substrate coating, or to increase the rate of nucleation, and, therefore, deposition of a coating on an underlying substrate. As indicated earlier in the introduction, ultra high vacuum techniques are not covered in detail in this work. Therefore, pressure modifications will be restricted to discussions of the range between a few tenths of a Torr and one atmosphere.

Low Pressure CVD

In general, most reactions involving hazardous or toxic vapor phase precursors are operated at reduced pressure from a safety perspective. Additionally, the enhancement of kinetic steps often occurs by operating at reduced pressure. As indicated in the individual chapters of this book, many reaction schemes involve operation at low pressure, and, therefore, care must be taken with the vacuum system, its maintenance, and the exhaust of a reaction co-product stream. For specific applications of low pressure operation, the reader should consult the appropriate chapter on the material of interest.

Atmospheric Pressure CVD

Whenever possible, more rapid turnaround time, the absence of load locks, the reduced maintenance cost associated with the avoidance of vacuum systems, and the ease of incorporation into continuous processing systems, all combine to make atmospheric pressure chemical vapor deposition an attractive technique. I n general, removal of reaction co-products is accomplished by utilization of a large excess of carrier gas (typically argon or nitrogen). Additionally, it may be noted that the thermal oxidation

1.3 Comparison of Deposition Techniques Y

of silicon to produce silicon dioxide, although not strictly a chemical vapor deposition process, can be conducted fairly well at one atmosphere.

1.3.1.5 Spray Pyrolysis Modifications

Spray pyrolysis, as differentiated from chemical vapor deposition, involves the direct application of either a flame to a vapor phase stream, or the entrainment and transport of particulates or vapors in some direction non-perpendicular to a substrate surface.

Combustion CVD

Combustion chemical vapor deposition is a very attractive process for deposition of structural materials. However, to date, little indication is present that this technique will serve to deposit high quality electronic materials. Nevertheless, for the rapid application of highly economic and environmentally stable coatings to extremely large objects, combustion chemical vapor deposition has many attractive features. Thus, for example, coating of the bottom of ship hulls may be accomplished by workers on scaf- folding using large spray guns operated by elevator hoist.

Aerosol Assisted CVD

Although sometimes differentiated from spray pyrolysis, aerosol assisted CVD is essentially the same motif. I t is, however, typically not conducted in a flame type regime. Nevertheless, frequently, materials are not transported perpendicular to a substrate surface, thereby bypassing one of the crucial elements of chemical vapor deposition - the ability to secure extraordinary step coverage in high aspect ratio materials, due to the non-line-of-sight technique.

1.3.2 Comparison of Non-Chemical Vapor Deposition Technologies

1.3.2.1 Molecular-Beam Epitaxy (MBE)

In contrast to CVD, MBE is conceptually simple and economically complicated. Ele- mental sources are introduced at a controlled rate to a substrate under ultra-high- vacuum (UHV) conditions, generally by means of Knudsen cells. Two decades ago, MBE revolutionized device physics as a technique capable of reproducibly producing sharp interfaces without graded transition regions, thereby forming perfect superlat- tice structures with unit cell junction abruptness. While MBE may be the ultimate research tool for the fabrication of complex and varied structures, presently i t has limitations for commercial applications. The demand of UHV conditions is intense both in terms of capital outlay and operating expense. Therefore MBE has been relegated cur-

10 1 Introduction

rently to playing a major role in laboratory investigations and a reduced role in production environments.

Metulorgariic M B E

OMMBE (MOMBE) and CBE (chemical-beam epitaxy) are hybrid techniques between OMVPE and MBE. To be consistent, Stringfellow has recommended O M M B E , even though M O M B E is far more prevalent in practice [4]. In these techniques, to deposit an epitaxial 13- 15 compound semiconducting layer on a substrate, organometallic group 13 element compounds and (organometallic, hydride, or elemental) group 15 element compounds are introduced into a UHV system. Rigorously, OMMBE is differentiated from CBE by the use of elemental group 15 sources, a distinction not enforced with rigidity. Yet another variation of the fused CVD MBE technique, gas- source MBE (GSMBE), uses elemental group 13 sources combined with hydride group 15 sources. Putting all the acronyms aside, these techniques, although in certain instances possessing advantages over the simpler CVD, are not prevalent in industrial locations at the present. The substantial challenges of maintaining a UHV production system have significantly inhibited this approach to date.

1.3.2.2 Other Physical Vapor Deposition Techniques

The interested reader is referred to the literature [3].

1.4 General Comments on CVD

1.4.1 Reactor Types

The interested reader is referred to the literature [7]. The chapter on reactor design, while somewhat dated in its presentation, offers an outstanding background to the chemical engineering principles necessary for successful achievement of a working CVD system.

1.4.2 Important Reaction Locations in CVD Reactors

I n CVD, all reactants enter the reactor in the vapor phase. In the region of the substrate, they decompose, forming a solid reaction product (deposited film) and vapor phase reaction co-products (residual gas).

vapor phase reactants -+ solid film + vapor phase co-products (1:l)

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