Semiconductor Device Physics and Simulation

Transcription

1 Semiconductor Device Physics and Simulation

2 MICRODEVICES Physics and Fabrication Technologies Series Editors: Ivor Brodie and Arden Sher SRI International Menlo Park, California Recent volumes in the series: COMPOUND AND JOSEPHSON HIGH-SPEED DEVICES Edited by Takahiko Misugi and Akihiro Shibatomi ELECTRON AND ION OPTICS Miklos Szilagyi ELECTRON BEAM TESTING TECHNOLOGY Edited by John T. L. Thong ORIENTED CRYSTALLIZATION ON AMORPHOUS SUBSTRATES E. I. Givargizov PHYSICS OF HIGH-SPEED TRANSISTORS Juras Pozela THE PHYSICS OF MICRO/NANO-FABRICATION Ivor Brodie and Julius J. Muray PHYSICS OF SUBMICRON DEVICES David K. Ferry and Robert O. Grondin THE PHYSICS OF SUBMICRON LITHOGRAPHY Kamil A. Valiev RAPID THERMAL PROCESSING OF SEMICONDUCTORS Victor E. Borisenko and Peter J. Hesketh SEMICONDUCTOR ALLOYS Physics and Materials Engineering An-Ban Chen and Arden Sher SEMICONDUCTOR DEVICE PHYSICS AND SIMULATION J. S. Yuan and J. J. Liou SEMICONDUCTOR LITHOGRAPHY Principles, Practices, and Materials Wayne M. Moreau SEMICONDUCTOR PHYSICAL ELECTRONICS Sheng S. Li A Continuation Order Plan is available for this series. A continuation order will bring delivery of each new volume immediately upon publication. Volumes are billed only upon actual shipment. For further information please contact the publisher.

3 Semiconductor Device Physics and Simulation J. S. Yuan and J. J. Liou University of Central Florida Orlando, Florida Springer Science+Business Media, LLC

4 Library of Congress Cataloging-in-Publication Data Yuan, J. S. Semiconductor device physics and simulation / J.S. Yuan and J.J. Liou. p. cm. (Microdevices) Includes bibliographical references and index. ISBN Semiconductors Computer simulation. 2. Junction transistors- -Computer simulation. I. Liou, Juin J. II. Title. III. Series. TK Y '2'0113--dc CIP ISBN ISBN (ebook) DOI / Springer Science+Business Media New York 1998 Originally published by Plenum Press, New York in 1998 Softcover reprint of the hardcover 1st edition All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

5 To my late father and my mother -J. S. Yuan

6 Preface The advent of the microelectronics technology has made ever-increasing numbers of small devices on a same chip. The rapid emergence of ultra-large-scaled-integrated (ULSI) technology has moved device dimension into the sub-quarter-micron regime and put more than 10 million transistors on a single chip. While traditional closed-form analytical models furnish useful intuition into how semiconductor devices behave, they no longer provide consistently accurate results for all modes of operation of these very small devices. The reason is that, in such devices, various physical mechanisms affect the device performance in a complex manner, and the conventional assumptions (i.e., one-dimensional treatment, low-level injection, quasi-static approximation, etc.) employed in developing analytical models become questionable. Thus, the use of numerical device simulation becomes important in device modeling. Researchers and engineers will rely even more on device simulation for device design and analysis in the future. This book provides comprehensive coverage of device simulation and analysis for various modem semiconductor devices. It will serve as a reference for researchers, engineers, and students who require in-depth, up-to-date information and understanding of semiconductor device physics and characteristics. The materials of the book are limited to conventional and mainstream semiconductor devices; photonic devices such as lightemitting and laser diodes are not included, nor does the book cover device modeling, device fabrication, and circuit applications. It is assumed that the reader has already acquired a basic understanding of device structures and operations, such as those given in Solid-State Electronic Devices, 4th ed. (Prentice-Hall, 1995) or Device Electronics/or Integrated Circuits, 2nd ed. (Wiley, 1986). A two-dimensional device simulator called MEDICI, originally developed by Stanford University (PISCES II) and supported by Technology Modeling Associates, Inc., CA, is used to perform the analysis and to generate the simulation results. Basically, MEDICI solves numerically the fi ve classical semiconductor device equations: Poisson's equation, electron and hole continuity equations, and electron and hole drift-diffusion current equations. Relevant device physics, such as heavy doping effects, concentration, and field-dependent free-carrier mobilities, and concentration-dependent free-carrier lifetimes, are incorporated in the program. The capability of MEDICI goes beyond the traditional device simulator, however, in that it also contains two optional modules which vii

7 viii PREFACE allow one to simulate the device performance, including the effects of lattice heating and heterostructure. A detailed description of MEDICI is given in Chapter 1. The book is organized into nine chapters. Except for the first chapter, which discusses semiconductor fundamentals and the capabilities and features of device simulators, each chapter covers a semiconductor device, providing dc, ac, and transient simulation results, discussions of relevant device physics, and their implications to device design and analysis. The devices covered, in the same order as the chapters, are p-n junction, bipolar junction transistors, junction field-effect transistors, metal-oxide-semiconductor fieldeffect transistors, bipolar/cmos devices, metal-semiconductor field-effect transistors, heterojunction bipolar transistors, and photoconductive diodes. All chapters contain useful figures to illustrate the physical mechanisms and characteristics of the semiconductor devices simulated by MEDICI and, in some cases, those observed in measurements. Extensive references have also been given as an aid to the reader who wishes to carry out an in-depth study on a particular topic. J. S. Yuan and J. J. Liou Department of Electrical and Computer Engineering University of Central Florida

8 Contents CHAPTER 1. Introduction 1.1. Semiconductor Device Fundamentals Mobility and Carrier Scattering Carrier Transport by Diffusion and the Einstein Relation Recombination and Generation Heavy Doping Effects and Band-Gap Narrowing Carrier Concentration in Semiconductors and Fermi-Dirac Statistics Basic Semiconductor Equations Used in Device Simulators Numerical Techniques Used in Device Simulators Capability and Limitations of Device Simulators 1.5. Applications of Device Simulation References CHAPTER 2. P-N Junction 2.1. Device Physics of p-n Junction DC Characteristics of a p-n Junction Diode Forward-Bias Current-Voltage Characteristics Reverse-Bias and Low-Forward-Bias Current-Voltage Characteristics Junction Avalanche Breakdown Temperature Dependence of Steady-State Current Two-Dimensional Effect AC Parameters of a p-n Junction Diode Junction Capacitance Diffusion Capacitance and Conductance Transient Behavior of a p-n Junction Diode Open-Circuit Voltage Decay Short-Circuit Current Decay Reverse Recovery Transient 2.5. Schottky Diodes ix

9 x CONTENTS 2.6. Heterojunction References CHAPTER 3. Bipolar Junction Transistors 3.1. Device Physics Collector Current Base Current Current Gain DC Characteristics and Simulation Current-Voltage Characteristics for Forward-Active and Saturation Operation C u r r ~ n t -Characteristics V o l t a g e for Reverse-Active Operation Current-Voltage Characteristics at Different Temperatures Emitter Crowding and Sidewall Injection Base Pushout and Collector Spreading Current-Dependent Base Resistance Avalanche Multiplication AC Operation and Device Simulation Small-Signal Current Gain Transconductance Output Conductance Junction Capacitances Cutoff Frequency Maximum Oscillation Frequency S-Parameters Transient Operation and Simulation Turn-on Transients Tum-off Transients 91 References CHAPTER 4. Junction Field-Effect Transistors 4.1. Concept and Theory MEDICI Simulation DC Characteristics of Long- and Short-Channel JFETs Transient Characteristics of JFETs Small-Signal Characteristics of JFETs References CHAPTER 5. Metal-Oxide Semiconductor Field-Effect Transistors 5.1. Current -Voltage Characteristics Strong Inversion Weak Inversion MEDICI Simulation DC Characteristics

10 CONTENTS xi Transient and AC Characteristics 5.3. Hot Electron Effect References CHAPTER 6. BiCMOS Devices 6.1. Comparisons of BiCMOS, CMOS, and BIT Principles of BiCMOS Operation BiCMOS Switching Delay BiCMOS Device Simulation BiCMOS Transient Analysis Including High-Current Effects Analytical Approach Numerical Approach Normalized Base Pushout Factor Radiation Effect on BiCMOS Performance Radiation Effects on the BJT in a BiCMOS Device Radiation Effects on the MOSFET in a BiCMOS Device Leakage Paths in BiCMOS MEDICI Simulation Including Radiation Effects The Model Including Effects of Base Pushout and Radiation Scaling Temperature Scaling Geometrical Scaling Supply Voltage Scaling Hot Electron Reliability of BiCMOS Devices. 202 References CHAPTER 7. Metal-Semiconductor Field-Effect Transistors 7.1. Schottky Diode Basic Concept Effect ofinterface States Bias Dependence ofthe Barrier Height Current-Voltage Characteristics Effect of Interfacial Layer on Current Transport Simple MESFET Model MEDICI Simulation Steady-State Simulation Transient Response Small-Signal Analysis Advanced MESFET Structure Heterojunction FETs. 239 References CHAPTER 8. Heterojunction Bipolar Transistors 8.1. Heterojunction Physics

11 xii CONTENTS 8.2. DC Characteristics Collector and Base Currents Offset Voltage Velocity Overshoot and Ballistic Transport Self-heating Effect RF Behavior Junction Capacitance Transconductance Output Conductance Cutoff Frequency Flicker Noise Transient Characteristics Emitter-Coupled Logic Using HBTs HBT Turn-off Transient InP HBTs SiGe HBTs Reliability ofhbts Multiemitter Fingers Emitter Collapse Phenomenon Emitter Ballasting Resistors.... References CHAPTER 9. Photoconductive Diodes 9.1. Horizontal PCE Analytical Model MEDICI Simulation DC Characteristics Transient Characteristics Vertical PCE DC Characteristics Transient Characteristics Self-heating Effects on PCE Performance References INDEX