Numerical simulation of polycrystalline-Silicon MOSFET´s

In this paper we investigate polycrystalline-silicon MOSFET operation by means of a two-dimensional device-analysis program developed at the University of Bologna. The grain-boundary model used in this study allows for both donor and acceptor states at the interface, and assumes a drift-diffusion transport mechanism, consistently with the general structure of the code. Results achieved thus far allow us to interpret the increased threshold voltage experimentally observed in polycrystalline-silicon MOSFET´s and the device transconductance in strong inversion; on the other hand, the current increase occurring at negative gate voltages is not justified by the numerical model so far implemented. It is believed that field-enhanced emission rates and impact ionization are possible mechanims to interpret the above conduction increase.