Contents Contents... v Preface... xiii Chapter 1 Introduction...1 1.1 Compact MOSFET Modeling for Circuit Simulation...1 1.2 The Trends of Compact MOSFET Modeling...5 1.2.1 Modeling new physical effects...5 1.2.2 High frequency (HF) analog compact models...6 1.2.3 Simulation robustness and efficiency...7 1.2.4 Model standardization...8 References...8 Chapter 2 Significant Physical Effects In Modern MOSFETs...13 2.1 MOSFET Classification and Operation...13 2.1.1 Strong inversion region (Vgs>Vth)...17 2.1.2 Weak and moderate inversion or the subthreshold region...18 2.2 Effects Impacting the Threshold Voltage...18 2.2.1 Non-uniform doping effects...19 2.2.2 Normal short channel effects...23
vi MOSFET Modeling & BSIM3 User s Guide 2.2.3 Reverse short channel effects... 23 2.2.4 Normal narrow-width effects... 25 2.2.5 Reverse narrow-width effects... 27 2.2.6 Body bias effect and bulk charge effect...28 2.3 Channel Charge Theory... 30 2.3.1 Accumulation... 33 2.3.2 Depletion... 33 2.3.3 Inversion... 34 2.4 Carrier Mobility... 37 2.5 Velocity Saturation... 39 2.6 Channel Length Modulation... 41 2.7 Substrate Current Due to Impact Ionization...44 2.8 Polysilicon Gate Depletion... 48 2.9 Velocity Overshoot Effects... 51 2.10 Self-heating Effect... 53 2.11 Inversion Layer Quantization Effects...55 References... 57 Chapter 3 Threshold Voltage Model...65 3.1 Threshold Voltage Model for Long Channel Devices... 65 3.2 Threshold Voltage Model with Short Channel Effects... 67 3.2.1 Charge sharing model... 68 3.2.2 Quasi 2-D models for drain induced barrier lowering effect... 71 3.3 Narrow Width Effect Model...77 3.4 Threshold Voltage Model in BSIM3v3... 80 3.4.1 Modeling of the vertical non-uniform doping effects... 80 3.4.2 Modeling of the RSCE due to lateral non-uniform channel doping... 83 3.4.3 Modeling of the short channel effect due to drain induced barrier lowering..85 3.4.4 Modeling of the narrow width effects... 88 3.4.5 Complete Vth model in BSIM3v3... 90 3.5 Helpful Hints... 92 References... 101 Chapter 4 I-V Model...105 4.1 Essential Equations Describing the I-V Characteristics...105
CONTENTS vii 4.2 Channel Charge Density Model...106 4.2.1 Channel charge model in the strong inversion region...106 4.2.2 Channel charge model in the subthreshold region...107 4.2.3 Continuous channel charge model of BSIM3v3...109 4.2.4 Continuous channel charge model with the effect of Vds... 112 4.3 Mobility Model...114 4.3.1 Piece-wise mobility models...114 4.3.2 Mobility models in BSIM3v3...116 4.4 I-V Model in the Strong Inversion Region... 117 4.4.1 I-V model in the linear (triode) region...117 4.4.2 Drain voltage at current saturation, Vdsat...118 4.4.3 Current and output resistance in the saturation region...120 4.5 Subthreshold I-V Model...124 4.6 Single Equation I-V model of BSIM3v3...125 4.7 Polysilicon Gate Depletion Effect...129 4.8 Helpful Hints...130 References... 140 Chapter 5 Capacitance Model... 143 5.1 Capacitance Components in a MOSFET... 144 5.2 Intrinsic Capacitance Model...145 5.2.1 Meyer model...145 5.2.2 Shortcomings of the Meyer model... 151 5.2.3 Charge-based capacitance model...154 5.3 Extrinsic Capacitance Model...161 5.4 Capacitance Model of BSIM3v3...163 5.4.1 Long channel capacitance model (capmod=0)... 164 5.4.2 Short channel capacitance (capmod=1)... 170 5.4.3 Single-equation short channel capacitance model (capmod=2)...178 5.4.4 Short channel capacitance model with quantization effect (capmod=3)... 186 5.5 Channel Length/Width in Capacitance Model...197 5.6 Helpful Hints...198 References...207 Chapter 6 Substrate Current Model...211 6.1 Substrate Current Generation...211
viii MOSFET Modeling & BSIM3 User s Guide 6.2 Substrate Current Model in BSIM3v3...212 6.3 Helpful Hints...215 References...217 Chapter 7 Noise Model...219 7.1 The Physical Mechanisms of Flicker (1/f) Noise... 219 7.2 The Physical Mechanism of Thermal Noise... 220 7.3 Flicker Noise Models in BSIM3v3... 221 7.3.1 SPICE2 flicker noise model (noimod=1)... 221 7.3.2 Unified flicker noise model (noimod=2)... 222 7.4 Thermal Noise Models in BSIM3v3... 229 7.4.1 Modified SPICE2 thermal noise model (noimod=1)... 230 7.4.2 BSIM3 thermal noise model (noimod=2)...230 7.5 Helpful Hints...233 References...240 Chapter 8 Source/Drain Parasitics Model... 243 8.1 Parasitic Components in a MOSFET... 243 8.2 Models of Parasitic Components in BSIM3v3...244 8.2.1 Source and drain series resistances... 244 8.2.2 DC model of the source/drain diodes...248 8.2.3 Capacitance model of the source/bulk and drain/bulk diodes... 250 8.3 Helpful Hints... 254 References...261 Chapter 9 Temperature Dependence Model... 263 9.1 Temperature Effects in a MOSFET... 263 9.2 Temperature Dependence Models in BSIM3v3... 265 9.3 Comparison of the Temperature-Effect Models with Measured Data... 270 9.4 Helpful Hints... 276 References...279 Chapter 10 Non-quasi Static (NQS) Model...281 10.1 The Necessity of Modeling NQS Effects... 281
CONTENTS ix 10.2 The NQS Model in BSIM3v3... 284 10.2.1 Physics basis and model derivation... 284 10.2.2 The BSIM3 NQS model... 289 10.3 Test Results of the NQS Model...292 10.4 Helpful Hints...297 References...301 Chapter 11 BSIM3v3 Model Implementation...303 11.1 General Structure of BSIM3v3 Model Implementation...303 11.2 Robustness Consideration in the Implementation of BSIM3v3... 306 11.3 Testing of Model Implementation... 315 11.4 Model Selectors of BSIM3v3...317 11.5 Helpful Hints...319 References...324 Chapter 12 Model Testing...327 12.1 Requirements for a MOSFET Model in Circuit Simulation... 327 12.2 Benchmark Tests... 329 12.3 Benchmark Test Results... 333 12.4 Helpful Hints... 350 References... 351 Chapter 13 Model Parameter Extraction...353 13.1 Overview of Model Parameter Extraction...353 13.2 Parameter Extraction for BSIM3v3... 355 13.2.1 Optimization and extraction strategy... 355 13.2.2 Extraction routines... 355 13.3 Binning Methodology... 367 13.4 Recommended Value Range of the Model Parameters... 368 13.5 Automated Parameter Extraction Tool... 372 References... 373
x MOSFET Modeling & BSIM3 User s Guide Chapter 14 RF and Other Compact Model Applications...375 14.1 RF Modeling... 375 14.1.1 Modeling of the gate resistance... 376 14.1.2 Modeling the substrate network... 383 14.1.3 A RF MOSFET model based on BSIM3v3 for GHz communication IC s... 385 14.2 Statistical Modeling... 393 14.3 Technology Extrapolation and Prediction Using BSIM3 Model... 399 References... 406 Appendix A BSIM3v3 Parameter Table...409 A.1 Model control parameters...409 A.2 Process parameters...410 A.3 Parameters for Vth model...410 A.4 Parameters for I-V model...411 A.5 Parameters for capacitance model... 414 A. 6 Parameters for effective channel length/width in I-V model... 415 A. 7 Parameters for effective channel length/width in C-V model... 416 A.8 Parameters for substrate current model...417 A.9 Parameters for noise models...417 A. 10 Parameters for models of parasitic components...418 A.11 Parameters for models of temperature effects...419 A.12 Parameters for NQS model...420 Appendix B BSIM3v3 Model Equations...421 B.1 Vth equations...421 B.2 Effective Vgs-Vth...422 B.3 Mobility...423 B.4 Drain saturation voltage...423 B.5 Effective Vds...424 B.6 Drain current expression...424 B.7 Substrate current...425 B.8 Polysilicon depletion effect...426 B.9 Effective channel length and width...426 B.10 Drain/Source resistance...426 B.11 Capacitance model equations...426 B.12 Noise model equations...440 B.13 DC model of the source/drain diodes...443
CONTENTS xi B.14 Capacitance model of the source/bulk and drain/bulk diodes... 444 B.15 Temperature effects...445 B.16 NQS model equations...447 B.17 A note on the poly-gate depletion effect...448 Appendix C Enhancements and Changes in BSIM3v3.1 versus BSIM3v3.0... 449 C. 1 Enhancements...449 C.2 Detailed changes...449 Appendix D Enhancements and Changes in BSIM3v3.2 versus BSIM3v3.1... 455 D.1 Enhancements... 455 D.2 Detailed changes... 456 Index... 459