Preface ...................................................... xvii
CHAPTER I
Semiconductors, Junctions, and MOSFET Overview .................. 1
1.1 Introduction ............................................... 1
1.2 Semiconductors ............................................. 1
1.2.1 Intrinsic Semiconductors, Free Electrons, and
Holes ............................................... 2
1.2.2 Extrinsic Semiconductors ............................ 4
1.2.3 Equilibrium in the Absence of Electric Field ........ 7
1.2.4 Equilibrium in the Presence of Electric Field ...... 10
1.2.5 Nonequilibrium; Quasi-Fermi Levels ................. 12
1.2.6 Relations between Charge Density, Electric
Field, and Potential; Poisson's Equation ........... 13
1.3 Conduction ................................................ 15
1.3.1 Transit Time ....................................... 15
1.3.2 Drift .............................................. 17
1.3.3 Diffusion .......................................... 22
1.3.4 Total Current ...................................... 25
1.4 Contact Potentials ........................................ 26
1.5 The pn Junction ........................................... 32
1.6 Overview of the MOS Transistor ............................ 43
1.6.1 Basic Structure .................................... 43
1.6.2 A Qualitative Description of MOS Transistor
Operation .......................................... 47
1.6.3 A Fluid Dynamical Analog ........................... 49
1.6.4 MOS Transistor Characteristics ..................... 52
1.7 Fabrication Processes and Device Features ................. 54
1.8 A Brief Overview of This Book ............................. 60
References ..................................................... 62
Problems ....................................................... 63
CHAPTER II
The Two-Terminal MOS Structure ................................. 65
2.1 Introduction .............................................. 65
2.2 The Flatband Voltage ...................................... 66
2.3 Potential Balance and Charge Balance ...................... 73
2.4 Effect of Gate-Body Voltage on Surface Condition .......... 75
2.4.1 Flatband Condition ................................. 75
2.4.2 Accumulation ....................................... 75
2.4.3 Depletion and Inversion ............................ 76
2.4.4 General Analysis ................................... 80
2.5 Accumulation and Depletion ................................ 86
2.6 Inversion ................................................. 88
2.6.1 General Relations and Regions of Inversion ......... 88
2.6.2 Strong Inversion ................................... 94
2.6.3 Weak Inversion ..................................... 98
2.6.4 Moderate Inversion ................................ 101
2.7 Small-Signal Capacitance ................................. 102
2.8 Summary of Properties of the Regions of Inversion ........ 111
References .................................................... 111
Problems ...................................................... 112
CHAPTER III
The Three-Terminal MOS Structure .............................. 115
3.1 Introduction ............................................. 115
3.2 Contacting the Inversion Layer ........................... 115
3.3 The Body Effect .......................................... 131
3.4 Regions of Inversion ..................................... 132
3.4.1 Approximate Limits ................................ 132
3.4.2 Strong Inversion .................................. 136
3.4.3 Weak Inversion .................................... 138
3.4.4 Moderate Inversion ................................ 141
3.5 A "VCB Control" Point of View ............................ 141
3.5.1 Fundamentals ...................................... 141
3.5.2 The "Pinchoff Voltage" ............................ 145
3.6 Uses for Three-Terminal MOS Structures ................... 147
References .................................................... 148
Problems ...................................................... 149
CHAPTER IV
The Four-Terminal MOS Transistor .............................. 151
4.1 Introduction ............................................. 151
4.2 Transistor Regions of Operation .......................... 156
4.3 Complete All-Region Model ................................ 158
4.4 Simplified All-Region Models ............................. 172
4.4.1 Linearizing the Depletion Region Charge ........... 172
4.4.2 Body-Referenced Simplified All-Region Models ...... 173
4.4.3 Source-Referenced Simplified All-Region Models .... 176
4.4.4 Charge Formulation of Simplified All-Region
Models ............................................ 177
4.5 Models Based on Quasi-Fermi Potentials ................... 181
4.6 Regions of Inversion in Terms of Terminal Voltages ....... 183
4.7 Strong Inversion ......................................... 186
4.7.1 Complete Strong-Inversion Model ................... 186
4.7.2 Body-Referenced Simplified Strong-Inversion
Model ............................................. 192
4.7.3 Source-Referenced Simplified Strong-Inversion
Model ............................................. 192
4.7.4 Model Origin Summary .............................. 203
4.8 Weak Inversion ........................................... 204
4.8.1 Special Conditions in Weak Inversion .............. 204
4.8.2 Body-Referenced Model ............................. 205
4.8.3 Source-Referenced Model ........................... 206
4.9 Moderate-Inversion and Single-Piece Models ............... 208
4.10 Source-Referenced vs. Body-Referenced Modeling ........... 210
4.11 Effective Mobility ....................................... 212
4.12 Effect of Extrinsic Source and Drain Series
Resistances .............................................. 222
4.13 Temperature Effects ...................................... 224
4.14 Breakdown ................................................ 226
4.15 The p-Channel MOS Transistor ............................. 228
4.16 Enhancement-Mode and Depletion-Mode Transistors .......... 230
4.17 Model Parameter Values, Model Accuracy, and Model
Comparison ............................................... 231
References .................................................... 233
Problems ...................................................... 240
CHAPTER V
Small-Dimension Effects ....................................... 243
5.1 Introduction ............................................. 243
5.2 Carrier Velocity Saturation .............................. 244
5.3 Channel Length Modulation ................................ 253
5.4 Charge Sharing ........................................... 259
5.4.1 Introduction ...................................... 259
5.4.2 Short-Channel Devices ............................. 261
5.4.3 Narrow-Channel Devices ............................ 266
5.4.4 Limitations of Charge-Sharing Models .............. 270
5.5 Drain-Induced Barrier Lowering ........................... 271
5.6 Punchthrough ............................................. 275
5.7 Combining Several Small-Dimension Effects into One
Model - A Strong-Inversion Example ....................... 277
5.8 Hot Carrier Effects; Impact Ionization ................... 280
5.9 Velocity Overshoot and Ballistic Operation ............... 285
5.10 Polysilicon Depletion .................................... 288
5.11 Quantum Mechanical Effects ............................... 293
5.12 DC Gate Current .......................................... 295
5.13 Junction Leakage; Band-to-Band Tunneling; GIDL ........... 302
5.14 Leakage Currents—Particular Cases ........................ 305
5.15 The Quest for Ever-Smaller Devices ....................... 307
5.15.1 Introduction ...................................... 307
5.15.2 Classical Scaling ................................. 308
5.15.3 Modern Scaling .................................... 312
References .................................................... 316
Problems ...................................................... 327
CHAPTER VI
The MOS Transistor in Dynamic Operation-Large-Signal
Modeling ...................................................... 329
6.1 Introduction ............................................. 329
6.2 Quasi-Static Operation ................................... 330
6.3 Terminal Currents in Quasi-Static Operation .............. 334
6.4 Evaluation of Intrinsic Charges in Quasi-Static
Operation ................................................ 341
6.4.1 Introduction ...................................... 341
6.4.2 Strong Inversion .................................. 342
6.4.3 Moderate Inversion ................................ 348
6.4.4 Weak Inversion .................................... 348
6.4.5 All-Region Model .................................. 350
6.4.6 Depletion and Accumulation ........................ 352
6.4.7 Plots of Charges vs. VGS .......................... 353
6.4.8 Use of Intrinsic Charges in Evaluating the
Terminal Currents ................................. 354
6.5 Transit Time under DC Conditions ......................... 355
6.6 Limitations of the Quasi-Static Model .................... 357
6.7 Non-Quasi-Static Modeling ................................ 363
6.7.1 Introduction ...................................... 363
6.7.2 The Continuity Equation ........................... 364
6.7.3 Non-Quasi-Static Analysis ......................... 365
6.8 Extrinsic Parasitics ..................................... 371
6.8.1 Extrinsic Capacitances ............................ 371
6.8.2 Extrinsic Resistances ............................. 374
6.8.3 Temperature Dependence ............................ 378
6.8.4 Simplified Models ................................. 378
References .................................................... 379
Problems ...................................................... 383
CHAPTER VII
Small-Signal Modeling for Low and Medium Frequencies .......... 385
7.1 Introduction ............................................. 385
7.2 A Low-Frequency Small-Signal Model for the Intrinsic
Part ..................................................... 386
7.2.1 Introduction ...................................... 386
7.2.2 Small-Signal Model for the Drain-to-Source
Current ........................................... 386
7.2.3 Small-Signal Model for the Gate and Body
Currents .......................................... 390
7.2.4 Complete Low-Frequency Small-Signal Model
for the Intrinsic Part ............................ 393
7.2.5 Strong Inversion .................................. 396
7.2.6 Weak Inversion .................................... 407
7.2.7 Moderate Inversion ................................ 409
7.2.8 All-Region Models ................................. 409
7.3 A Medium-Frequency Small-Signal Model for the
Intrinsic Part ........................................... 414
7.3.1 Introduction ...................................... 414
7.3.2 Intrinsic Capacitances ............................ 414
7.4 Including the Extrinsic Part ............................. 435
7.5 Noise ................................................... 436
7.5.1 Introduction ...................................... 436
7.5.2 White Noise ....................................... 440
7.5.3 Flicker Noise ..................................... 450
7.5.4 Noise in Extrinsic Resistances .................... 456
7.5.5 Including Noise in Small-Signal Circuits .......... 456
7.6 All-Region Models ........................................ 456
References .................................................... 458
Problems ...................................................... 469
CHAPTER VIII
High-Frequency Small-Signal Models ............................ 473
8.1 Introduction ............................................. 473
8.2 A Complete Quasi-Static Model for the Intrinsic Part ..... 474
8.2.1 Complete Description of Intrinsic Capacitance
Effects ........................................... 474
8.2.2 Small-Signal Equivalent Circuit Topologies ........ 478
8.2.3 Evaluation of Capacitances ........................ 484
8.2.4 Frequency Region of Validity ...................... 491
8.3 y-Parameter Models ....................................... 492
8.4 Non-Quasi-Static Models .................................. 499
8.4.1 Introduction ...................................... 499
8.4.2 A Non-Quasi-Static Strong-Inversion Model ......... 500
8.4.3 Other Approximations and Higher-Order Models ...... 519
8.4.4 Model Comparison .................................. 522
8.5 High-Frequency Noise ..................................... 524
8.6 Considerations in MOSFET Modeling for RF Applications .... 529
References .................................................... 538
Problems ...................................................... 542
CHAPTER IX
Substrate Nonuniformity and Other Structural Effects ......... 547
9.1 Introduction ............................................. 547
9.2 Ion Implantation and Substrate Nonuniformity ............. 548
9.3 Substrate Transverse Nonuniformity ....................... 551
9.3.1 Preliminaries ..................................... 551
9.3.2 Threshold Voltage ................................. 555
9.3.3 Drain Current ..................................... 564
9.3.4 Buried-Channel Devices ............................ 566
9.4 Substrate Lateral Nonuniformity .......................... 571
9.5 Well Proximity Effect .................................... 577
9.6 Stress Effects ........................................... 581
9.7 Statistical Variability .................................. 584
References .................................................... 592
Problems ...................................................... 598
CHAPTER X
Modeling for Circuit Simulation ............................... 600
10.1 Introduction ............................................. 600
10.2 Types of Models .......................................... 601
10.2.1 Models for Device Analysis and Design ............. 601
10.2.2 Device Models for Circuit Simulation .............. 602
10.3 Attributes of Good Compact Models ........................ 606
10.4 Model Formulation ........................................ 608
10.4.1 General Consideration and Choices ................. 609
10.5 Model Implementation in Circuit Simulators ............... 615
10.6 Model Testing ............................................ 618
10.7 Parameter Extraction ..................................... 618
10.8 Simulation and Extraction for RF Applications ............ 635
10.9 Common MOSFET Models Available in Circuit Simulators ..... 638
10.9.1 BSIM .............................................. 638
10.9.2 EKV ............................................... 640
10.9.3 PSP ............................................... 640
10.9.4 Other Models ...................................... 642
References .................................................... 642
Problems ...................................................... 648
APPENDICES
A Basic Laws of Electrostatics in One Dimension .............. 653
В Quasi-Fermi Levels and Currents ............................ 659
С General Analysis of the Two-Terminal MOS Structure ......... 661
D Careful Definitions for the Limits of Moderate
Inversion .................................................. 666
E General Analysis of the Three-Terminal MOS Structure ....... 669
F Drain Current Formulation Using Quasi-Fermi Potentials ..... 674
G Modeling Based on Pinchoff Voltage and Related Topics ...... 678
H Evaluation of the Intrinsic Transient Source and Drain
Currents ................................................... 684
I Quantities Used in the Derivation of the Non-Quasi-
Static y-Parameter Model ................................... 687
J Analysis of Buried-Channel Devices ......................... 690
К MOSFET Model Benchmark Tests ............................... 700
INDEX ......................................................... 713
|
