MOSFET subthreshold region modeling for ultra-low-power circuit design using BSIM3v3

Accurate subthreshold region MOSFET models are critical for the design of quality ultra-low-power integrated circuits. Therefore, it is important that MOSFET device model algorithms accommodate robust modeling of a MOSFET's subthreshold and moderate conduction regions. We have investigated subthreshold and moderate conduction region modeling using the industry-standard BSIM3v3 MOSFET model, subsequently making modifications to improve BSIM3v3's modeling of those regions. These model changes are important because they provide ultra-low-power IC circuit designers more accurate device models, which result in improved circuit designs and fewer IC design iterations. Therefore, these improvements translate into less design expense, shorter time-to-market, potential gain of market share and increased company revenue.; For subthreshold region modeling, we have developed and implemented model changes that improve simulated-to-measured data correlation of subthreshold swings and subthreshold region offsets for non-zero values of substrate voltage VSB. The changes, which have been implemented in a Verilog-A version of BSIM3v3, add features that allow simulated drain current ID to be adjusted, linearly and exponentially, over back bias, significantly improving correlation with measured data.; For ultra-low-power analog circuit design, a crucial region of MOSFET operation is the weak conduction saturation region. We have implemented a change to the BSIM3v3 model that improves simulated-to-measured data correlation in that region, providing more accurate models for use in IC circuit design.; To improve moderate conduction region simulated-to-measured data correlation, changes have been made to the BSIM3v3 mobility model that provide for the modeling of Coulombic scattering effects, especially those that result in subtle changes in the mobility of buried channel MOSFETs near the threshold voltage VTH. The changes allow mobility to be adjusted near VTH, resulting in better correlation between simulated and measured ID.