Runyan TEXAS INSTRUMENTS INCORPORATED Semiconductor·Components Division EXAS INSTRUMENTS INCORPORATED Silicon Semiconductor Technology W. R. Runyan Texas Instruments Electronics Series McGraw·HiII McGraw-Hili Beok Company 54276 Silicon Semiconductor Technology The Engineering Staff of Texas Instruments Incorporated • TRANSISTOR CIRCUIT DESIGN Runyan • SILICON SEMICONDUCTOR TECHNOLOGY Sevin • FIELD-EFFECT TRANSISTORS Silicon Semiconductor Technology w. R. Runyan Semiconductor Research and Development Laboratory Texas Instruments Incorporated McGRAW-HILL BOOK COMPANY New York San Francisco Toronto London Sydney SILICON SEMICONDUCTOR TECHNOLOGY Copyright © 1965 by Texas Instruments Incorporated. All Rights Reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of Texas Instru­ ments Incorporated. Library of Congress Catalog Card Number 64-24607. Information contained in this book is believed to be accurate and reliable. However, responsibility is assumed neither for its use nor for any infringement of patents or rights of others which may result from its use. No license is granted by implication or otherwise under any patent or patent right of Texas Instruments or others. 54276 345678 9-MP-9 8 7 6 Preface The purposes of this book are to provide in a single reference the properties of silicon important to those who would use it as a semiconductor and to discuss at length several of the more important semiconductor technologies, such as crystal growing and diffusion. It had its beginning in a set of notes I began compiling shortly after starting work in the semiconductor industry. Since most of my activ­ ities were with silicon, these notes were restricted to information pertaining to that material. A few years later, while teaching a graduate course in semiconductor technology at Southern Methodist University, the notes were expanded from a col­ lection of data to a unified coverage of topics relating to semiconductor material technology and were used as an adjunct to a general text. However, because of my interest in silicon, after the semiconductor material technology was presented in some depth it was then applied specifically to silicon. This in no sense restricts the book's use to those interested only in silicon since the majority of each of those chapters not relating to specific silicon properties discusses each technology inde­ pendent of the material. While this book will be of most interest to device designers and those working as semiconductor technologists, it should also prove of considerable interest to those using devices, both circuit designers and systems engineers, in that it will supply background information and material properties helpful in understanding device performance. An attempt was made to cover all aspects of the technology except those relating to the surface itself. The complexity of surface behavior would warrant a separate volume and is beyond the scope of this book. In addition, where there are books covering some phase ofthe technology in great detail, e.g., Pfann's "Zone Melting," only a cursory treatment is given. -.J. The author would like to thank Harry L. Owens for his continued interest and support, Dr. Lyndon Taylor of the University of Texas and Dr. W. E. Phillips of Texas Technology College for a critical reading of the manuscript, John R. Miller for editorial advice, Virginia Belshaw for typing, Stacy B. Watelski for the photo­ micrographs, Earl W. Scott of Scott's Studio for the crystal photographs of Chap. 4, and the photographic staff of Texas Instruments Incorporated for all other photog­ raphy. In addition, the help of the many other members of the Semiconductor Research and Development Laboratory of Texas Instruments Incorporated is gratefully acknowledged. W R. Runyan v Foreword It is particularly timely for a book to appear on the subject of silicon semicon­ ductor technology. Until the past few years the semiconductor device industry was based largely on germanium technology, with silicon being restricted chiefly to military and power applications. During recent years silicon technology has been developed so that silicon now promises, along with germanium, to have broad usage. Integrated circuits have been developed almost exclusively around silicon technology. While these were developed first for military applications, they will be applied broadly to industrial and consumer markets. It is also evident that future generations of devices will be far more sophisticated than those now in use, and that a much better understand­ ing and blending of material properties with device functions will be required. Dr. Runyan has written a book which should prove to be a useful addition to the literature on semiconductor technology and an aid in this blending process. He is especially well qualified to author such a book since much of his professional career has been devoted to research and development on silicon materials and devices. At present he leads the materials research program in the Semiconductor Research and Development Laboratory at Texas Instruments. This book is a part of the new Texas Instruments Electronics Series, through which we hope to make readily available to the technical community important research findings which will further the progress of the electronics industry. Richard L. Petritz, DIRECTOR SEMICONDUCTOR RESEARCH AND DEVELOPMENT LABORATORY vi Contents Preface............................ ...... .............. ......... v Foreword . vi Chapter 1 . An Historical Note . .. 1 REFERENCES ..................................................... 3 Chapter 2. Silicon-manufacturing Processes . .. 5 2.1 Early Methods of Manufacture. 5 2.2 Summary of Applicable Methods . 7 2.3 Zinc-Silicon Tetrachloride ................................... 7 2.4 Silane Decomposition . 9 2.5 Iodide Process . .. 10 2.6 Silicon Tetrachloride and Trichlorosilane Processes . .. 12 REFERENCES. .. 14 Chapter 3. Silicon-casting Processes . .. 17 3.1 Melting in Mold. .. 17 3.2 Pouring into Mold. .. 22 3.3 Ambit Casting. .. 24 REFERENCES. .. 27 Chapter 4. Crystal Growth . .. 29 4.1 Crystal-growing Environment ................................ 29 4.2 Types of Crystal Growth . .. 30 4.3 Crystallization from a One-component System. .. 32 4.4 Growth from Multicomponent Systems. .. 36 4.5 Teal-Little................................................. 38 4.6 Behavior of Impurities During Growth from the Melt. .. 49 4.7 Miscellaneous Techniques. .. 60 4.8 Growth from Low-temperature Melts ........................ " 63 4.9 Vapor-Liquid-Solid (VLS) Method of Crystal Growth. .. 65 4.10 Growth from the Vapor . .. 65 REFERENCES 78 vii viii Contents o Chapter 5. Crystal Habit and Orientation . .. 84 5.1 Crystal Systems ............................................ 84 5.2 Silicon Structure. .. 88 5.3 Crystal Habit ..... .. 89 5.4 Rough Orientation. .. 93 5.5 X-ray Orientation .......................................... 94 5.6 Optical Orientation. .. 97 5.7 Twinning.................................................. 98 5.8 Detection of Twinning ...................................... 101 5.9 Grain Boundaries. .. 101 5.10 Lineage ................................................ 102 REFERENCES 102 Chapter 6. Doping Procedures ........................................ 104 6.1 Effects ofImpurities on Resistivity. .. 104 6.2 Effect of Segregation Coefficient on Resistivity . .. 107 6.3 Methods of Doping . .. 110 6.4 Discussion of Crystal Yields. .. 114 REFERENCES 116 Chapter 7. Diffusion ................................................ 117 7.l Elementary Theory .......................................... 117 7.2 Diffusion Along a Grain Boundary ............................ l33 7.3 Field-aided Diffusion ........................................ l36 7.4 Numerical Calculations. .. l37 7.5 Diffusion Processes ......................................... 141 7.6 Diffusion Coefficients ....................................... 151 REFERENCES ................................................ 159 Chapter 8. Electrical Properties ....................................... 164 8.1 Resistivity ................................................ 164 8.2 Mobility .................................................. 166 8.3 Drift Mobility ............................................. 168 8.4 Hall Coefficient and Hall Mobility ........................... 169 8.5 Effects of High Field on Resistivity ........................... 172 8.6 Width of Space-charge Region in p-n Junctions ................ 174 8.7 Effects of Pressure ......................................... 176 8.8 Energy Bands ............................................. 182 8.9 Effective Masses for Electron and Holes ....................... 183 8.10 Miscellaneous Effects ..... 185 REFERENCES ............................................... 185 Contents ix Chapter 9. Optical Properties ....................................... 187 9.l Absorption Coefficients. .. 187 9.2 Photoconductivity ......................................... 197 9.3 Reflection Coefficient. .. 198 9.4 Index of Refraction ........................................ 198 9.5 Emissivity ................................................ 200 9.6 Light Emission ............................................ 200 9.7 Tyndall Effect ............................................. 203 9.8 Birefringence ............................................. 203 9.9 Optical Elements .......................................... 204 9.10 Optical Coatings ..........................................