CAD for GaAs IC manufacture-ability-thirteen issues in FET physics

Yield optimisation requires physical descriptions of both active and passive components which must be general enough to work for all CAD users and not tie the designer to a specific process or foundry. Microwave measurements and practical data lead to the conclusion that there are at least thirteen phenomena occurring in FETs and HEMTs that are not well understood physically, but for which good mathematical-physical descriptions must be developed. The authors identify these phenomena and conclude that CAD tools based on physics need to incorporate punch-through effects, full profile, gate recess and surface charge descriptions, and must be at least fully two-dimensional (if not three-dimensional) to predict satisfactorily the electrically observable phenomena occurring in practical FETs and HEMTs. Physics-based FET and HEMT models may eventually prove to be the only valid description for such devices operated under large-signal conditions