Finding the asymmetric parasitic source and drain resistances from the a.c. conductances of a single MOS transistor

Layout asymmetry, processing, or hot-carrier stressing can give rise to unequal source and drain parasitic resistances in a MOSFET. In these cases, it is necessary to extract these resistances separately without the aid of other transistors. In this paper, we present a simple method to extract the source and drain parasitic resistances separately. This method, unlike earlier ones that depend on the measurements of the d.c. resistances of several MOSFETs, is based on accurate formulations and measurements of the a.c. conductances with respect to the gate and drain terminals of a single transistor. This allows us to get reasonably accurate estimates of these resistances in a more straightforward manner. We also discuss the main error terms in detail.