FET Modeling for Circuit Simulation

Circuit simulation is widely used for the design of circuits, both discrete and integrated. Device modeling is an impor­ tant aspect of circuit simulation since it is the link between the physical device and the sim ulate d device. Curren tly available circuit simulation programs provide a variety of built-in models. Many circuit designers use these built-in models whereas some incorporate new models in the circuit sim ulation programs. Understanding device modeling with particular emphasis on circuit simulation will be helpful in utilizing the built-in models more efficiently as well as in implementing new models. SPICE is used as a vehicle since it is the most widely used circuit sim ulation program. How­ ever, some issues are addressed which are not directly appli­ cable to SPICE but are applicable to circuit simulation in general. These discussions are useful for modifying SPICE and for understanding other simulation programs. The gen­ eric version 2G. 6 is used as a reference for SPICE, although numerous different versions exist with different modifications. This book describes field effect transistor models commonly used in a variety of circuit sim ulation pro­ grams. Understanding of the basic device physics and some familiarity with device modeling is assumed. Derivation of the model equations is not included. ( SPICE is a circuit sim ulation program available from EECS Industrial Support Office, 461 Cory Hall, University of Cali­ fornia, Berkeley, CA 94720. ) Acknowledgements I wish to express my gratitude to Valid Logic Systems, Inc.

Contenu

1 - Circuit Simulation.- 1.1 Introduction.- 1.2 Circuit Simulation Programs.- 1.3 Circuit Analysis.- 1.3.1 DC Analysis.- 1.3.2 Transient Analysis.- 1.3.3 Charge Nonconservation Problem.- 1.3.4 AC Analysis.- 2 - Device Modeling.- 2.1 Model Development.- 2.2 Model Specification.- 2.3 Model Computation.- 2.4 Model Parameter Extraction.- 3 - Diode Models.- 3.1 Introduction.- 3.2 DC Characteristics.- 3.2.1 MOSFET diodes.- 3.2.2 JFET and MESFET diodes.- 3.2.3 Parasitic diode model.- 3.2.4 Schottky barrier diodes.- 3.3 Junction voltage limiting.- 3.4 Charge storage.- 3.5 Temperature dependence.- 3.6 Model parameter extraction.- 4 - Jfet Models.- 4.1 Introduction.- 4.2 DC Characteristics.- 4.3 Device symmetry.- 4.4 Voltage limiting.- 4.4.1 Gate-source voltage.- 4.4.2 Gate-drain voltage.- 4.5 Charge storage.- 4.6 Temperature dependence.- 4.7 Model parameter extraction.- 5 - Mosfet Models.- 5.1 Introduction.- 5.2 Basic dc characteristics.- 5.3 Device dimensions.- 5.4 MOSFET parasitics.- 5.5 Common model parameters.- 5.6 Basic device model (level 1).- 5.7 Second order effects.- 5.8 Bulk doping term.- 5.9 Threshold voltage shift.- 5.10 Mobility reduction.- 5.11 Velocity saturation.- 5.12 Channel length modulation.- 5.13 Subthreshold conduction.- 5.14 Avalanche current.- 5.15 Oxide charging.- 5.16 Device symmetry.- 5.17 Voltage limiting.- 5.17.1 Gate-source voltage.- 5.17.2 Drain-source voltage.- 5.18 Geometry dependence.- 5.19 Level 2 model.- 5.19.1 Threshold voltage.- 5.19.2 Mobility reduction.- 5.19.3 Velocity saturation.- 5.19.4 Channel length modulation.- 5.19.5 Drain current.- 5.19.6 Subthreshold conduction.- 5.20 Level 3 model.- 5.20.1 Threshold voltage.- 5.20.2 Mobility reduction.- 5.20.3 Velocity saturation.- 5.20.4 Drain current.- 5.20.5 Channel length modulation.- 5.20.6 Subthreshold conduction.- 5.21 CSIM model.- 5.22 BSIM model.- 5.22.1 Threshold voltage.- 5.22.2 Mobility reduction.- 5.22.3 Effective beta.- 5.22.4 Saturation Voltage.- 5.22.5 Drain Current.- 5.22.6 Subthreshold Conduction.- 5.22.7 Geomtery dependence.- 5.23 Table lookup models.- 5.24 Depletion devices.- 5.25 Model parameter extraction.- 5.26 Charge storage.- 5.27 Meyer capacitance model.- 5.28 Smoothed Meyer model.- 5.29 Charge non conservation problem.- 5.30 Charge based models.- 5.31 Ward-Dutton charge model.- 5.32 Yang-Chatter je e charge model.- 5.33 BSIM charge model.- 5.34 Second order effects on charges.- 5.35 Temperature dependence.- 5.36 Modeling for Analog Applications.- 5.37 Power MOSFETs.- 6 - Mesfet Models.- 6.1 Introduction.- 6.2 Device symmetry.- 6.3 DC characteristics.- 6.4 Subthreshold conduction.- 6.5 Charge storage.- 6.6 Charge based model.- 6.7 Temperature dependence.- 6.8 Modeling for analog applications.- 6.9 Model parameter extraction.- References.