A Compact Model Satisfying Gummel Symmetry in Higher Order Derivatives and Applicable to Asymmetric MOSFETs

Abstract

This paper presents a new concept for the MOSFET saturation voltages at the drain and source sides referenced to bulk, and applies them to the popularly used smoothing functions for the effective drain-source voltage ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_ds,eff </i> ). The proposed model not only builds in physically all the terminal-bias variations, but is also extended to include source/drain asymmetry in real devices in a single-core compact model. The new model resolves a key bottleneck in existing models for passing the Gummel symmetry test (GST) in higher order derivatives, which has to be traded off for the geometry-dependent <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_ds,eff </i> smoothing parameter. The complete drain-current model, including the effects of velocity saturation and overshoot as well as source/drain series resistance, has also been reformulated with the same ldquobulk-referencingrdquo concept. It is shown that the proposed model passes the GST in all higher order derivatives without any constraint on the value of the smoothing parameter. It also demonstrates potential extension to modeling asymmetric MOSFETs, which is becoming an important model capability.