Practical aspects of MOS transistor model "accuracy" in modern CMOS technology

Compact MOS transistor models are critical infrastructure for circuit design and simulation in modem CMOS technology. However, MOS modeling has become isolated from related disciplines, and has developed benchmarks and guidelines unaffected by the needs and constraints related to the circuit design use of those models. In this paper, model "accuracy" is considered from a practical and wide-ranging viewpoint. First, binned and unbinned models are compared - with particular emphasis on "accuracy" as it relates to the process center, rather than fitting results for one specific set of measured data. Next, that discussion is extended to the generation of digital timing libraries. This paper highlights an important divergence between MOS transistor model requirements for analog and digital design. Analog design imposes a demanding set of constraints on a MOS transistor model which go well beyond simple "accuracy," while digital design demands a new focus on MOS transistor model forms which are simple, fast, and very efficient.