A measurement-based charge sheet capacitance model of short-channel MOSFET's for SPICE

Based on the surface potential formulation[1], a charge-sheet capacitance model for short-channel MOSFET's has been developed and implemented in SPICE. No iterations are needed to find the surface potential. The model equations are charge-based and includes the drift velocity saturation, the diffusion current, the effect of the bulk charge, the channel length modulation and the channel side fringing field capacitances. As a byproduct of the development of this capacitance model, an analytic charge-sheet current model has been obtained. The current, charges, their first derivatives(conductance and capacitance) and second derivatives are continuous over all the operating regions. An automatic direct-on-wafer off-chip capacitance measurement system with 14 aF rms resolution has been developed for performing the model parameter extraction.