Semiconductor devices : Physics and technology

3RD EDITION

Semiconductor

Devices

Physics and Technology

S. M. SZE

EtronTech Distinguished Chair Professor

College of Electrical and Computer Engineering

National Chiao Tung University

Hsinchu, Taiwan

M. K. LEE

Professor

Department of Electrical Engineering

National Sun Yat-sen University

Kaohsiung, Taiwan

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ISBN 978-0470-53794-7

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

In memory of

Prof. John L. Moll (1921 ~ 2011)

A pioneer of Semiconductor Devices.

Contents

Preface vii

Acknowledgments ix

CHAPTER 0 1

Introduction

0.1 Semiconductor Devices 1

0.2 Semiconductor Technology 6

Summary 12

PART I

SEMICONDUCTOR PHYSICS

CHAPTER 1

Energy Bands and Carrier Concentration in

Thermal Equilibrium 15

1.1 Semiconductor Materials 15

1.2 Basic Crystal Structures 17

1.3 Valence Bonds 22

1.4 Energy Bands 23

1.5 Intrinsic Carrier Concentration 29

1.6 Donors and Acceptors 34

Summary 40

CHAPTER 2

Carrier Transport Phenomena 43

2.1 Carrier Drift 43

2.2 Carrier Diffusion 53

2.3 Generation and Recombination Processes 56

2.4 Continuity Equation 62

2.5 Thermionic Emission Process 68

2.6 Tunneling Process 69

2.7 Space-Charge Effect 71

2.8 High-Field Effects 73

Summary 77

PART II

SEMICONDUCTOR DEVICES

CHAPTER 3

p-n Junction 82

3.1 Thermal Equilibrium Condition 83

3.2 Depletion Region 87

3.3 Depletion Capacitance 95

3.4 Current-Voltage Characteristics 99

3.5 Charge Storage and Transient Behavior 108

3.6 Junction Breakdown 111

3.7 Heterojunction 117

Summary 120

CHAPTER 4

Bipolar Transistors and Related Devices 123

4.1 Transistor Action 124

4.2 Static Characteristics of Bipolar Transistors 129

4.3 Frequency Response and Switching of

Bipolar Transistors 137

4.4 Nonideal Effects 142

4.5 Heterojunction Bipolar Transistors 146

4.6 Thyristors and Related Power Devices 149

Summary 155

CHAPTER 5

MOS Capacitor and MOSFET 160

5.1 Ideal MOS Capacitor 160

5.2 SiO2-Si MOS Capacitor 169

5.3 Carrier Transport in MOS Capacitors 174

5.4 Charge-Coupled Devices 177

5.5 MOSFET Fundamentals 180

Summary 192

CHAPTER 6

Advanced MOSFET and Related Devices 195

6.1 MOSFET Scaling 195

6.2 CMOS and BiCMOS 205

6.3 MOSFET on Insulator 210

6.4 MOS Memory Structures 214

6.5 Power MOSFET 223

Summary 224

CHAPTER 7

MESFET and Related Devices 228

7.1 Metal-Semiconductor Contacts 229

7.2 MESFET 240

7.3 MODFET 249

Summary 255

CHAPTER 8

Microwave Diodes; Quantum-Effect and

Hot-Electron Devices 258

8.1 Microwave Frequency Bands 259

8.2 Tunnel Diode 260

8.3 IMPATT Diode 260

8.4 Transferred-Electron Devices 265

8.5 Quantum-Effect Devices 269

8.6 Hot-Electron Devices 274

Summary 277

v

CHAPTER 9

Light Emitting Diodes and Lasers 280

9.1 Radiative Transitions and Optical Absorption 280

9.2 Light-Emitting Diodes 286

9.3 Various Light-Emitting Diodes 291

9.4 Semiconductor Lasers 302

Summary 319

CHAPTER 10

Photodetectors and Solar Cells 323

10.1 Photodetectors 323

10.2 Solar Cells 336

10.3 Silicon and Compound-Semiconductor Solar Cells 343

10.4 Third-Generation Solar Cells 348

10.5 Optical Concentration 352

Summary 352

PART III

SEMICONDUCTOR TECHNOLOGY

CHAPTER 11

Crystal Growth and Epitaxy 357

11.1 Silicon Crystal Growth from the Melt 357

11.2 Silicon Float-Zone Proces 363

11.3 GaAs Crystal-Growth Techniques 367

11.4 Material Characterization 370

11.5 Epitaxial-Growth Techniques 377

11.6 Structures and Defects in Epitaxial 384

Layers

Summary 388

CHAPTER 12

Film Formation 392

12.1 Thermal Oxidation 392

12.2 Chemical Vapor Deposition of Dielectrics 400

12.3 Chemical Vapor Deposition of Polysilicon 409

12.4 Atom Layer Deposition 412

12.5 Metallization 414

Summary 425

CHAPTER 13

Lithography and Etching 428

13.1 Optical Lithography 428

13.2 Next-Generation Lithographic Methods 441

13.3 Wet Chemical Etching 447

13.4 Dry Etching 450

Summary 462

CHAPTER 14

Impurity Doping 466

14.1 Basic Diffusion Process 467

14.2 Extrinsic Diffusion 476

14.3 Diffusion-Related Processes 480

14.4 Range of Implanted Ions 483

14.5 Implant Damage and Annealing 490

14.6 Implantation-Related Processes 495

Summary 501

CHAPTER 15

Integrated Devices 505

15.1 Passive Components 507

15.2 Bipolar Technology 511

15.3 MOSFET Technology 516

15.4 MESFET Technology 529

15.5 Challenges for Nanoelectronics 532

Summary 537

APPENDIX A

List of Symbols 541

APPENDIX B

International Systems of Units (SI Units) 543

APPENDIX C

Unit Prefixes 544

APPENDIX D

Greek Alphabet 545

APPENDIX E

Physical Constants 546

APPENDIX F

Properties of Important Element and Binary

Compound Semiconductors at 300 K 547

APPENDIX G

Properties of Si and GaAs at 300 K 548

APPENDIX H

Derivation of the Density of States in a Semiconductor 549

APPENDIX I

Derivation of Recombination Rate for Indirect

Recombination 553

APPENDIX J

Calculation of the Transmission Coefficient for

a Symmetric Resonant-Tunneling Diode 555

APPENDIX K

Basic Kinetic Theory of Gases 557

APPENDIX L

Answers to Selected Problems 559

Photo credits 563

Index 565

vi

The book is an introduction to the physical principles of modern semiconductor devices and their advanced

fabrication technology. It is intended as a text for undergraduate students in applied physics, electrical and

electronics engineering, and materials science. It can also serve as a reference for graduate students and

practicing engineers as well as scientists who are not familiar with the subject or need an update on device

and technology developments.

WHAT’S NEW IN THE THIRD EDITION

r 35% of the material has been revised or updated. We have added many sections of current

interest such as CMOS image sensors, FinFET, 3rd generation solar cells, and atomic layer

deposition. In addition, we have omitted or reduced sections of less important topics to

maintain the overall book length.

r We have expanded the treatment of MOSFET and related devices to two chapters because of

their importance in electronic applications. We have also expanded the treatment of photonic

devices to two chapters because of their importance in communication and alternative energy

sources.

r To improve the development of each subject, sections that contain graduate-level mathematics

or physical concepts have been omitted or moved to the Appendixes,.

TOPICAL COVERAGE

r Chapter 0 gives a brief historical review of major semiconductor devices and key technology

developments. The following text is organized in three parts.

r Part I, Chapters 1–2, describes the basic properties of semiconductors and their conduction

processes, with special emphasis on the two most important semiconductors, silicon (Si) and

gallium arsenide (GaAs). The concepts in Part I , which will be used throughout the book,

require a background knowledge of modern physics and college calculus.

r Part II, Chapters 3–10, discusses the physics and characteristics of all major semiconductor

devices. We begin with the p–n junction, the key building block of most semiconductor devices.

We proceed to bipolar and field-effect devices and then cover microwave, quantum-effect, hot￾electron, and photonic devices.

r Part III, Chapters 11–15, deals with processing technology from crystal growth to impurity

doping. We present the theoretical and practical aspects of the major steps in device fabrication

with an emphasis on integrated devices.

Preface

vii

KEY FEATURES

Each chapter includes the following features:

r The chapter starts with an overview of the topical contents. A list of covered learning goals is

also provided.

r The third edition contains many worked-out examples that apply basic concepts to specific

problems.

r A chapter summary at the end of each chapter summarizes the important concepts and helps

the student review the content before tackling the homework problems that follow.

r The book includes about 250 homework problems. Answers to odd-numbered problems with

numerical solutions are provided in Appendix L.

COURSE DESIGN OPTIONS

The third edition can provide greater flexibility in course design. The book contains enough material for a

full-year sequence in device physics and processing technology. Assuming three lectures per week, a two￾semester sequence can cover Chapters 0–7 in the first semester, leaving Chapters 8–15 for the second semester.

For a three-quarter sequence, the logical breakpoints are Chapters 0–5, Chapters 6–10, and Chapters 11–15.

A two-quarter sequence can cover Chapters 0–5 in the first quarter. The instructor has several options

for the second quarter. For example, covering Chapters 6, 12, 13, 14 and 15 produces a strong emphasis on

MOSFET and related process technologies, while covering Chapters 6–10 emphasizes all major devices. For

a one-quarter course on semiconductor device processing, the instructor can cover Section 0.2 and Chapters

11–15.

A one-semester course on basic semiconductor physics and devices can cover Chapters 0–7. A one￾semester course on microwave and photonic devices can cover Chapters 0–3, and 7–10. For students with

some familiarity with semiconductor fundamentals, a one-semester course on MOSFET physics and

technology can cover Chapters 0, 5, 6, and 11–15. Of course, there are many other course design options

depending on the teaching schedule and the instructor’s choice of topics.

TEXTBOOK SUPPLEMENTS

r Instructor’s Manual. A complete set of detailed solutions to all the end-of￾chapter problems has been prepared. These solutions are available free to all

adopting faculty.

r The figures used in the text are available to instructors in electronic format,

from the publisher. More information is available at the publisher’s website:

http: //www.wiley.com/college/sze

viii

Acknowledgments

In the course of writing the text, we had the good fortune of help and support from many people. First

we express our gratitude to the management of our academic institutions, the National Chiao Tung

University and the National Sun Yat-sen University, without whose support this book could not have

been written. One of us (S. M. Sze) would like to thank Etron Technology Inc., Taiwan, ROC, for the

EtronTech Distinguished Chair Professorship grant that provided the environment to work on this book.

Many people have assisted us in revising this book. We have benefited significantly from suggestions

made by the reviewers who took time from their busy schedules for careful scrutiny of this book. Credit

is due to the following scholars: Prof. C. C. Chang of the National Taiwan Ocean University; Profs. L.

B. Chang and C. S. Lai of the Chang Gung University; Dr. O. Cheng and Mr. T. Kao of the United

Microelectronics Corporation (UMC); Dr. S. C. Chang and Dr. Y. L. Wang of the Taiwan Semiconductor

Manufacturing Company (TSMC); Prof. T. C. Chang of the National Sun Yat-sen University; Profs. T.

S. Chao, H. C. Lin, P. T. Liu, and T. Wang of the National Chiao Tung University; Prof. J. Gong of the

Tunghai University; Profs. C. F. Huang and M. C. Wu of the National Tsing Hua University; Profs. C.

J. Huang and W. K. Yeh of the National University of Kaohsiung; Profs. J. G. Hwu, C. Liu, and L. H.

Peng of the National Taiwan University; Prof. J. W. Hong of the National Central University; Profs. W.

C. Hsu and W. C. Liu of the National Cheng Kung University; Profs. Y. L. Jiang and D. S. Wuu of the

National Chung Hsing University; Prof. C. W. Wang of the National Chung Cheng University; Dr. C. L.

Wu of Transcom. Inc.; and Dr. Y. H. Yang of PixArt Imaging Inc.

We are further indebted to Mr. N. Erdos for technical editing of the manuscript. In each case where

an illustration was used from another published source, we have received permission from the copyright

holder. Even through all illustrations were then adapted and redrawn, we appreciate being granted these

permissions. At John Wiley & Sons, we wish to thank Mr. D. Sayre and Mr. G. Telecki, who encouraged

us to undertake the project. One of us (M. K. Lee) would like to thank his daughter Ko-Hui for preparing

homework problems and solutions. Finally, we are grateful to our wives, Therese Sze and Amanda Lee,

for their support and assistance over the course of the book project.

S. M. Sze M. K. Lee

Hsinchu, Taiwan Kaohsiung, Taiwan

August 2010

ix

Introduction

0.1 SEMICONDUCTOR DEVICES

0.2 SEMICONDUCTOR TECHNOLOGY

SUMMARY

As an undergraduate in applied physics, electrical engineering, electronics engineering, or materials science,

you might ask why you need to study semiconductor devices. The reason is that semiconductor devices are

the foundation of the electronics industry, which is the largest industry in the world. A basic knowledge of

semiconductor devices is essential to the understanding of advanced courses in electronics. This knowledge will

also enable you to contribute to the Information Age, which is based on electronic technology.

Specifically, we cover the following topics:

r Four building blocks of semiconductor devices.

r Eighteen important semiconductor devices and their roles in electronic applications.

r Twenty three important semiconductor technologies and their roles in device processing.

r Technology trends toward high-density, high-speed, low-power consumption,

and nonvolatility.

0.1 SEMICONDUCTOR DEVICES

Figure 1 shows the sales volume of the semiconductor-device–based electronics industry in the past 30 years

and projects sales to the year 2020. Also shown are the gross world product (GWP) and the sales volumes of the

automobile, steel, and semiconductor industries.1,2 We note that the electronics industry surpassed the automobile

industry in 1998. If the current trends continue, in year 2020 the sales volume of the electronics industry will reach

two trillion dollars and will constitute about 3% of GWP. It is expected that the electronic industry will remain

the largest industry in the world throughout the 21st century. The semiconductor industry, which is a subset of

the electronic industry, will surpass the steel industry around 2010 and constitute 25% of the electronics industry

in 2020.

0.1.1 Device Building Blocks

Semiconductor devices have been studied for over 135 years.3

To date, there are 18 major devices, with over

140 device variations related to them.4

All these devices can be constructed from a small number of device

building blocks.

Figure 2a is the metal-semiconductor interface, which is an intimate contact between a metal and a

semiconductor. This building block was the first semiconductor device ever studied (in the year 1874). This

interface can be used as a rectifying contact; that is, the device allows electrical current to flow easily only in one

direction, or as an ohmic contact, which can pass current in either direction with a negligibly small voltage drop.

0 CHAPTER

Fig. 1 Gross world product (GWP) and sales volumes of the electronics, automobile, semiconductor, and

steel industries from 1980 to 2010 and projected to 2020.1,2

We can use this interface to form many useful devices. For example, by using a rectifying contact as the gate* and

two ohmic contacts as the source and drain, we can form a MESFET (metal-semiconductor field-effect transistor),

an important microwave device.

The second building block is the p–n junction (Fig. 2b), which is formed between a p-type (with positively

charged carriers) and an n-type (with negatively charged carriers) semiconductor. The p–n junction is a key

building block for most semiconductor devices, and p–n junction theory serves as the foundation of the physics

of semiconductor devices. By combining two p–n junctions, that is, by adding another p-type semiconductor, we

form the p–n–p bipolar transistor, which was invented in 1947 and had an unprecedented impact on the electronic

industry. If we combine three p–n junctions to form a p–n–p–n structure, it becomes -a switching device called a

thyristor.

The third building block (Fig. 2c) is the heterojunction interface, that is, an interface formed between two

dissimilar semiconductors. For example, we can use gallium arsenide (GaAs) and aluminum arsenide (AlAs) to form

a heterojunction. Heterojunctions are the key components for high-speed and photonic devices.

Figure 2d shows the metal-oxide-semiconductor (MOS) structure. The structure can be considered a

combination of a metal-oxide interface and an oxide-semiconductor interface. By using the MOS structure as

the gate and two p–n junctions as the source and drain, we can form a MOSFET (MOS field-effect transistor).

The MOSFET is the most important device for advanced integrated circuits, which contains tens of thousands of

devices per integrated circuit chip.

Fig. 2 Basic device building blocks. (a) Metal-semiconductor interface; (b) p–n junction; (c)

heterojunction interface; and (d) metal-oxide-semiconductor structure.

*The italicized terms in this paragraph and in subsequent paragraphs are defined and explained in Part II of

the book.

2 Semiconductors

0.1.2 Major Semiconductor Devices

Some major semiconductor devices are listed in Table 1 in chronological order; those with a superscript b are

two-terminal devices, and the others are three-terminal or four-terminal devices.3

The earliest systematic study of

semiconductor devices (metal-semiconductor contacts) is generally attributed to Braun,5

who in 1874 discovered

that the resistance of contacts between metals and metal sulfides (e.g., copper pyrite) depended on the magnitude

and polarity of the applied voltage. The electroluminescence phenomenon (for the light-emitting diode) was

discovered by Round6

in 1907. He observed the generation of yellowish light from a crystal of carborundum when

he applied a potential of 10 V between two points on the crystal.

In 1947, the point-contact transistor was invented by Bardeen and Brattain.7

This was followed by Shockley’s8

classic 1949 paper on p–n junctions and bipolar transistors. Figure 3 shows the first transistor. The two point

contacts at the bottom of the triangular quartz crystal were made from two stripes of gold foil separated by about

50 μm (1 μm = 10–4 cm) and pressed onto a semiconductor surface. The semiconductor used was germanium. With

one gold contact forward biased, that is, having positive voltage with respect to the third terminal, and the other

reverse biased, the transistor action was observed: that is, the input signal was amplified. The bipolar transistor is a

key semiconductor device and has ushered in the modern electronic era.

TABLE 1 Major Semiconductor Devices

Year Semiconductor Devicea Author(s)/Inventor(s) Ref.

1874 Metal-semiconductor contactb Braun 5

1907 Light emitting diodeb Round 6

1947 Bipolar transistor Bardeen, Brattain, and Shockley 7

1949 p–n junctionb Shockley 8

1952 Thyristor Ebers 9

1954 Solar cellb Chapin, Fuller, and Pearson 10

1957 Heterojunction bipolar transistor Kroemer 11

1958 Tunnel diodeb Esaki 12

1960 MOSFET Kahng and Atalla 13

1962 Laserb Hall et al. 15

1963 Heterostructure laserb Kroemer, Alferov and Kazarinov 16,17

1963 Transferred-electron diodeb Gunn 18

1965 IMPATT diodeb Johnston, DeLoach, and Cohen 19

1966 MESFET Mead 20

1967

Nonvolatile semiconductor

memory

Kahng and Sze 21

1970 Charge-coupled device Boyle and Smith 23

1974 Resonant tunneling diodeb Chang, Esaki, and Tsu 24

1980 MODFET Mimura et al. 25

2004 5 nm MOSFET Yang et al. 14

a

MOSFET, metal-oxide-semiconductor field-effect transistor; MESFET, metal-semiconductor field-effect

transistor; MODFET, modulation-doped field-effect transistor.

b

Denotes a two-terminal device; others are a three- or four-terminal device.

Introduction 3