Source–Drain Partitioning in MOSFET

The Ward-Dutton (WD) partitioning scheme [IEEE Trans. Electron Devices, vol. ED-27, p. 1571, Aug. 1980] is used extensively to develop transient and high-frequency advanced compact models for MOSFET devices. Recently, it has been shown that WD partitioning fails for field-dependent mobility [IEEE Electron Device Lett., vol. 27, p. 674, Aug 2006] or for laterally asymmetrical doping [IEDM Tech. Dig., p.751, Dec. 2004], [IEEE Trans. Electron Devices, vol. 53, p. 270, Feb. 2006]. This paper is aimed at presenting a generalization of the partitioning concept. We show that, although it is not possible to guaranty a partitioning scheme for general operation of the MOSFET, it is possible to show the existence of a partitioning scheme for small-signal operation of the device accounting for both field-dependent mobility and lateral asymmetry. Application of this new concept in capacitance evaluation of lateral asymmetric MOSFET considerably simplifies the existing capacitance-evaluation methodology and accounts for any arbitrary field-dependent mobility. It also gives a mean to physically understand the unusual behavior delta Cdg in lateral asymmetric MOSFET. We also show how failure of the WD partitioning can affect the present compact-modeling Methodologies.