Semiconductors devices physics and technology

Tai ngay!!! Ban co the xoa dong chu nay!!! RD 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 JOHN WILEY & SONS, INC Acquisitions Editor Dan Sayre Marketing Manager Christopher Ruel Senior Editorial Assistant Katie Singleton Editorial Program Assistant Samantha Mendel Production Manager Micheline Frederick Cover Designer Wendy Lai Pre-press Service Robots & Cupcakes This book was typeset in Times Roman by the authors and printed and bound by Quad Graphics/Versailles The cover was printed by Quad Graphics/Versailles cover photo: © 2010 IEEE Reprinted, with permission, from IEDM Technical Digest, S Whang et al, "Novel 3-dimensional Dual Control-gate with Surrounding Floating-gate (DC-SF) NAND flash cell for 1Tb file storage application." 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Praise Jesus Contents Preface Acknowledgments CHAPTER Introduction 0.1 Semiconductor Devices 0.2 Semiconductor Technology Summary vii ix 1 12 PART I SEMICONDUCTOR PHYSICS CHAPTER Energy Bands and Carrier Concentration in Thermal Equilibrium 1.1 Semiconductor Materials 1.2 Basic Crystal Structures 1.3 Valence Bonds 1.4 Energy Bands 1.5 Intrinsic Carrier Concentration 1.6 Donors and Acceptors Summary 15 15 17 22 23 29 34 40 CHAPTER Carrier Transport Phenomena 2.1 Carrier Drift 2.2 Carrier Diffusion 2.3 Generation and Recombination Processes 2.4 Continuity Equation 2.5 Thermionic Emission Process 2.6 Tunneling Process 2.7 Space-Charge Effect 2.8 High-Field Effects Summary 43 43 53 56 62 68 69 71 73 77 PART II SEMICONDUCTOR DEVICES CHAPTER p-n Junction 3.1 Thermal Equilibrium Condition 3.2 Depletion Region 3.3 Depletion Capacitance 3.4 Current-Voltage Characteristics 3.5 Charge Storage and Transient Behavior 3.6 Junction Breakdown 3.7 Heterojunction Summary 82 83 87 95 99 108 111 117 120 v CHAPTER Bipolar Transistors and Related Devices 4.1 Transistor Action 4.2 Static Characteristics of Bipolar Transistors 4.3 Frequency Response and Switching of Bipolar Transistors 4.4 Nonideal Effects 4.5 Heterojunction Bipolar Transistors 4.6 Thyristors and Related Power Devices Summary 123 124 129 137 142 146 149 155 CHAPTER MOS Capacitor and MOSFET 5.1 Ideal MOS Capacitor 5.2 SiO2-Si MOS Capacitor 5.3 Carrier Transport in MOS Capacitors 5.4 Charge-Coupled Devices 5.5 MOSFET Fundamentals Summary 160 160 169 174 177 180 192 CHAPTER Advanced MOSFET and Related Devices 6.1 MOSFET Scaling 6.2 CMOS and BiCMOS 6.3 MOSFET on Insulator 6.4 MOS Memory Structures 6.5 Power MOSFET Summary 195 195 205 210 214 223 224 CHAPTER MESFET and Related Devices 7.1 Metal-Semiconductor Contacts 7.2 MESFET 7.3 MODFET Summary 228 229 240 249 255 CHAPTER Microwave Diodes; Quantum-Effect and Hot-Electron Devices 8.1 Microwave Frequency Bands 8.2 Tunnel Diode 8.3 IMPATT Diode 8.4 Transferred-Electron Devices 8.5 Quantum-Effect Devices 8.6 Hot-Electron Devices Summary 258 259 260 260 265 269 274 277 14.4 Range of Implanted Ions 14.5 Implant Damage and Annealing 14.6 Implantation-Related Processes Summary 483 490 495 501 CHAPTER 15 Integrated Devices 15.1 Passive Components 15.2 Bipolar Technology 15.3 MOSFET Technology 15.4 MESFET Technology 15.5 Challenges for Nanoelectronics Summary 505 507 511 516 529 532 537 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 547 392 392 400 409 412 414 425 APPENDIX G Properties of Si and GaAs at 300 K 548 APPENDIX I Derivation of Recombination Rate for Indirect Recombination 553 428 428 441 447 450 462 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 Index 563 565 CHAPTER Light Emitting Diodes and Lasers 9.1 Radiative Transitions and Optical Absorption 9.2 Light-Emitting Diodes 9.3 Various Light-Emitting Diodes 9.4 Semiconductor Lasers Summary 280 280 286 291 302 319 CHAPTER 10 Photodetectors and Solar Cells 10.1 Photodetectors 10.2 Solar Cells 10.3 Silicon and Compound-Semiconductor Solar Cells 10.4 Third-Generation Solar Cells 10.5 Optical Concentration Summary 323 323 336 343 348 352 352 PART III SEMICONDUCTOR TECHNOLOGY CHAPTER 11 Crystal Growth and Epitaxy 11.1 Silicon Crystal Growth from the Melt 11.2 Silicon Float-Zone Proces 11.3 GaAs Crystal-Growth Techniques 11.4 Material Characterization 11.5 Epitaxial-Growth Techniques 11.6 Structures and Defects in Epitaxial Layers Summary CHAPTER 12 Film Formation 12.1 Thermal Oxidation 12.2 Chemical Vapor Deposition of Dielectrics 12.3 Chemical Vapor Deposition of Polysilicon 12.4 Atom Layer Deposition 12.5 Metallization Summary CHAPTER 13 Lithography and Etching 13.1 Optical Lithography 13.2 Next-Generation Lithographic Methods 13.3 Wet Chemical Etching 13.4 Dry Etching Summary CHAPTER 14 Impurity Doping 14.1 Basic Diffusion Process 14.2 Extrinsic Diffusion 14.3 Diffusion-Related Processes 357 357 363 367 370 377 384 388 466 467 476 480 vi APPENDIX H Derivation of the Density of States in a Semiconductor 549 Preface 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 r 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 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 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 r r r Chapter gives a brief historical review of major semiconductor devices and key technology developments The following text is organized in three parts 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 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, hotelectron, and photonic devices 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 vii KEY FEATURES Each chapter includes the following features: r r r r The chapter starts with an overview of the topical contents A list of covered learning goals is also provided The third edition contains many worked-out examples that apply basic concepts to specific problems 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 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 twosemester 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 onesemester 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-ofchapter 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 Appendix C Unit Prefixes* Multiple Prefix Symbol 18 exa E 15 peta P 12 tera T giga G mega M kilo k 10 hecto h 10 10 10 10 10 10 10 deka da -1 deci d -2 centi c -3 milli m -6 micro μ -9 nano n -12 pico p -15 femto f -18 atto a 10 10 10 10 10 10 10 10 * As adopted by International Committee on Weights and Measures (Compound prefixes should not be used, e.g., not μμ but p.) 544 Appendix D Greek Alphabet Letter Lowercase Uppercase Alpha α Α Beta β Β Gamma γ Γ Delta δ Δ Epsilon ε Ε Zeta ζ Ζ Eta η Η Theta θ Θ Iota ι Ι Kappa κ Κ Lambda λ Λ Mu μ Μ Nu ν Ν Xi ξ Ξ Omicron ο Ο Pi π Π Rho ρ Ρ Sigma σ Σ Tau τ Τ Upsilon υ ϒ Phi ϕ Φ Chi χ Χ Psi ψ Ψ Omega ω Ω 545 Appendix E Physical Constants Quantity Symbol Value Angstrom unit Å 10 Å= nm = 10-3 μm= 10-7 cm = 10-9 m Avogadro’s number Nav 6.02214 × 1023 Bohr radius aB 0.52917 Å Boltzmann constant k 1.38066 × 10-23 J/K (R/Nav) Elementary charge q 1.60218 × 10-19 C Electron rest mass m0 0.91094 × 10-30 kg Electron volt eV eV = 1.60218 × l0-19J = 23.053 kcal/mol Gas constant R 1.98719 cal/mol-K Permeability in vacuum μ0 1.25664 × 10-8 H/cm (4π x 10-9) Permittivity in vacuum ε0 8.85418 × 10-14 F/cm (l/μoc2) Planck constant 6.62607 × 10-34 J·s Reduced Planck constant h h- 1.05457 × 10-34 J·s (h/2π) Proton rest mass Mp 1.67262 × l0-27 kg Speed of light in vacuum c 2.99792 × 1010 cm/s 1.01325 × l05 Pa Standard atmosphere Thermal voltage at 300 K kT/q 0.025852 V Wavelength of eV quantum λ 1.23984 μm 546 Appendix F Properties of Important Element and Binary Compound Semiconductors at 300 K Mobilityb (cm2/V-s) Banda μn μp Dielectric constant 0.66 I 3900 1800 16.2 5.43 1.12 I 1450 505 11 SiC 3.08 2.86 I 300 40 9.66 AlSb 6.13 1.61 I 200 400 12.0 GaAs 5.65 1.42 D 9200 320 12.4 GaP 5.45 2.27 I 160 135 11.1 GaSb 6.09 0.75 D 3750 680 15.7 InAs 6.05 0.35 D 33000 450 15.1 InP 5.86 1.34 D 5900 150 12.6 InSb 6.47 0.17 D 77000 850 16.8 CdS 5.83 2.42 D 340 50 5.4 CdTe 6.48 1.56 D 1050 100 10.2 ZnO 4.58 3.35 D 200 180 9.0 ZnS 5.42 3.68 D 180 10 8.9 PbS 5.93 0.41 I 800 1000 17.0 PbTe 6.46 0.31 I 600 4000 30.0 Lattice constant Bandgap Semiconductor (Å) (eV) Element Ge 5.65 Si IV-IV III-V II-IV IV-VI a I, indirect, D, direct The values are for drift mobilities obtained in the purest and most perfect materials available to date b 547 Appendix G Properties of Si and GaAs at 300 K Properties Si Atoms/cm Atomic weight Breakdown field (V/cm) Crystal structure Density (g/cm3) Dielectric constant Effective density of states in conduction band, NC (cm-3) Effective density of states in valence band, NV (cm-3) Effective mass (conductivity) Electrons (mn/m0) Holes (mp/m0) Electron affinity, χ (V) Energy gap (eV) Index of refraction Intrinsic carrier concentration (cm-3) Intrinsic resistivity (Ω-cm) Lattice constant (Å) Linear coefficient of thermal expansion, ΔL/L×T (oC-1) Melting point (oC) Minority-carrier lifetime (s) Mobility (cm2/V-s) μn (electrons) μp (holes) Specific heat (J/g-oC) Thermal conductivity (W/cm-K) Vapor pressure (Pa) GaAs 22 5.02 × 10 28.09 ~3 × 105 Diamond 2.329 11.9 2.86 × 1019 4.42 × 1022 144.63 ~ × 105 Zincblende 5.317 12.4 4.7 × 1017 2.66 × 1019 7.0 × 1018 0.26 0.69 4.05 1.12 3.42 9.65 × 109 0.063 0.57 4.07 1.42 3.3 2.25 × 106 3.3 × 105 5.43102 2.59 × 10-6 2.9 × 108 5.65325 5.75 × 10-6 1412 × 10-2 1240 ~10-8 1450 505 0.7 1.31 at 1650oC 10-6 at 900oC 9200 320 0.35 0.46 100 at 1050oC at 900oC 548 Appendix H Derivation of the Density of States in a Semiconductor 3-D Density of States For a three dimensional (3-D) structure such as a bulk semiconductor, to calculate the electron and hole concentrations in the conduction and valence bands, respectively, we need to know the density of states, that is, the number of allowed energy states per unit energy per unit volume (i.e., in the unit of number of states/eV/cm3) When electrons move back and forth along the x-direction in a semiconductor material, the movements can be described by standing-wave oscillations The wavelength λ of a standing wave is related to the length of the semiconductor L by L λ nx , (1) where nx is an integer The wavelength can be expressed by de Broglie hypothesis: h , px λ (2) where h is the Planck’s constant and px is the momentum in the x-direction Substituting Eq into Eq gives Lpx hnx (3) The incremental momentum dpx required for a unity increase in nx is Ldpx h (4) For a three-dimensional cube of side L, we have L3 dpx dpy dpz = h3 (5) The volume dpx dpy dpz in the momentum space for a unit cube (L = 1) is thus equal to h3 Each incremental change in n corresponds to a unique set of integers (nx, ny, nz), which in turn corresponds to an allowed energy state Thus, the volume in momentum space for an energy state is h3 Figure shows the momentum space in spherical coordinates The volume between two concentric spheres (from p to p+dp  p2dp The number of energy states contained in the volume is the p2dp)/h3, where the factor accounts for the electron spins 549 Fig The momentum space in spherical coordinates The energy E of the electron (here we consider only the kinetic energy) is given by E or p2 2mn (6) p  2mn E , (7) where p is the total momentum (with components px, py and pz in Cartesian coordinates) and mn is the effective mass From Eq 7, we can substitute E for p and obtain 8π p dp ⎛ 2mn ⎞ 2 π N ( E )dE = = E dE ⎜ ⎟ h3 ⎝ h ⎠ and ⎛ 2m ⎞ N ( E ) = 4π ⎜ n ⎟ E , ⎝ h ⎠ where N(E) is called the density of states The N(E) varies with 550 (8) E as shown in Fig 2a (9) Fig Density of states N(E) for (a) bulk semiconductor (3-D), (b) quantum well (2-D), (c) quantum wire (1-D), and (d) quantum dot (0-D) 2-D Density of States In two-dimensional structures such as the quantum well, the derivation of 2-D density of states is almost the same as for 3-D except that one of the p-space components is fixed Instead of finding the number of p-states enclosed within a sphere, we calculate the number of p-states lying in an annulus of radius p to p + dp The incremental momentum dpx required for a unity increase in nx is Ldpx = h (10) L2 dpx dpy = h2 (11) For a two-dimensional square of side L, we have The area dpx dpy in the momentum space for a unit square (L = 1) is thus equal to h2 Figure shows the momentum space in circular coordinates The area between two concentric circles (from p to p+dp  pdp The number of energy            pdp)/h2, where the factor accounts for the electron spins N ( E )dE = 4π pdp ⎛m = 4π ⎜ 2n h2 ⎝h N (E) = 4π mn m = n2 h π? ⎞ ⎟ dE ⎠ (12) (13) The 2-D density of states does not depend on energy As the top of the energy gap is reached, there is a significant number of available states Taking into account the other energy levels in the quantum well, the density of states becomes the staircase-like function shown in Fig 2b 551 Fig The momentum space in circular coordinates 1-D Density of States In one-dimensional structures such as the quantum wire, two of the p-space components are fixed Compared with 2-D, the p-space becomes a line The wavelength λ of a standing wave is related to the length of the semiconductor L by L = nx , λ/2 (14) The incremental momentum dpx required for a unity increase in nx is 2LdPx  h , (15) The dpx in the momentum space for a line with a unit length (L= 1) is thus equal to h/2 Figure shows the momentum space in line coordinates The length between p to p+dp is dp The number of energy states contained in the line is then 2dp/(h/2), where the factor accounts for the electron spins 1/ N ( E )dE = 2dp ⎛ 2m ⎞ = 2⎜ n ⎟ h/2 ⎝ E ⎠ 1/ 1 ⎛ 2m ⎞ dE = ⎜ n ⎟ h π⎝ ? ⎠ 1/ N (E) ⎛ 2mn ⎞ π ⎜⎝ ? ⎟⎠ E 1/ dE E1/ (16) (17) The N(E) varies with E 1/ as shown in Fig 2c 0-D Density of States In a 0-D structure such as a quantum dot, the values of p are quantized in all directions All the available states exist only at discrete energies and can be represented by a delta function as shown in Fig 2d The density of states in a quantum dot is continuous and independent of energy In a real quantum dot, however, the size distribution leads to a broadening of this line function Fig The momentum space in line coordinates 552 Appendix I Derivation of Recombination Rate for Indirect Recombination A schematic diagram of the various transitions that occur in recombination through recombination centers is shown in Fig 13 of Chapter If the concentration of centers in the semiconductor is Nt, the concentration of unoccupied centers is given by Nt(1-F), where F is the Fermi distribution function for the probability that a center is occupied by an electron In equilibrium, F 1+ e ( Et EF ) kT (1) where Et is the energy level of the center and EF is the Fermi level Therefore, the capture rate of an electron by a recombination center (Fig 13a of Chapter 2) is given by Ra ≈ nN t (1 F ) (2) We designate the proportionality constant by the product vthn, so that vthσ n nN t (1 F ) Ra (3) The product vthn may be visualized as the volume swept out per unit time by an electron with cross section n If the center lies within this volume, the electron will be captured by it The rate of emission of electrons from the center (Fig 13b) is the inverse of the electron capture process The rate is proportional to the concentration of centers occupied by electrons, that is, NtF We have Rb en N t F (4) The proportionality constant en is called the emission probability At thermal equilibrium the rates of capture and emission of electrons must be equal (Ra = Rb) Thus, the emission probability can be expressed in terms of the quantities already defined in Eq 3: en vthσ n n(1 F ) F (5) Since the electron concentration in thermal equilibrium is given by n ni e( EF Ei ) kT 553 , (6) we obtain en υthσ n ni e( Et Ei )/ kT (7) The transitions between the recombination center and valence band are analogous to those described above The capture rate of a hole by an occupied recombination center (Fig 13c) is given by Rc = υthσ p pN t F (8) By arguments similar to those for electron emission, the rate of hole emission (Fig 13d) is Rd = e p N t (1 − F ) (9) The emission probability ep of a hole may be expressed in terms of vth and p by considering the thermal equilibrium condition for which Rc = Rd: e p = υthσ p ni e ( Ei − Et ) kT (10) Let us now consider the nonequilibrium case in which an n-type semiconductor is illuminated uniformly to give a generation rate GL Thus in addition to the process shown in Fig 13, electron-hole pairs are generated as a result of light In steady state the electrons entering and leaving the conduction band must be equal This is called the principle of detailed balance, and it yields dnn = GL − ( Ra − Rb ) = dt (11) Similarly, in steady state the detailed balance of holes in valence band leads to dpn = GL − ( Rc − Rd ) = dt (12) Under equilibrium conditions, that is, GL = 0, Ra = Rb, and Rc = Rd However, under state-state nonequilibrium conditions, Ra ≠ Rb, and Ra ≠ Rb From Eqs 11 and 12 we obtain GL = Ra − Rb = Rc − Rd ≡ U (13) We can get the net recombination rate U from Eqs 3, 4, 8, and 9: U ≡ Ra − Rb = vthσ nσ p N t ( pn nn − ni ) σ p [ pn + ni e( Ei − Et ) kT ] + σ n [nn + ni e( Et − Ei ) kT ] 554 (14)