The Small-Signal Behaviour of Polycrystalline-Silicon MOSFET´s

In this paper we investigate the small-signal properties of polycrystalline-silicon MOSFET´s by means of a newly-developed device-analysis program. The physical model of the grain-boundaries includes both donor and acceptor energy-distributed traps and accounts for time-dependent carrier-storage. The above phenomena are shown to be responsible for anomalously-large parasitic capacitances, which can seriously affect the transistor dynamic behaviour. Moreover, the admittance matrix turns out to be strongly non-reciprocal, and an equivalent circuit is identified characterized by a transadmittance with an imaginary part up to 3-4 orders of magnitude larger than the oxide admittance.