DETERMINATION OF HOT-CARRIER-INDUCED INTERFACE STATE DENSITY IN POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS

Polysilicon thin-film transistors are of great interest for their appl ication in large area microelectronics and especially for their circui t applications. A successful circuit design requires a proper understa nding of the electrical characteristics and in the present work some s pecific aspects related to the hot-carrier induced electrical instabil ities are presented. In particular, generation of interface states nea r the drain junction occurs when the devices are operated for a prolon ged time in the so-called kink regime. In the present work we show bot h experimentally and by numerical simulations how the presence of such interface states affects the electrical characteristics. Furthermore, a novel simple method is proposed to extract, from the analysis of th e sheet conductances, the interface state density. The hot-carrier ind uced interface state density relative to the present devices shows a f eatureless continuous distribution. Reduction of the generated interfa ce states is observed if trapped holes are annihilated by electron cap ture. These results suggest that the interface states are induced by t he presence of trapped holes, in agreement with similar data reported for c-Si metal-oxide-semiconductor structures. (C) 1998 American Insti tute of Physics. [S0021-8979(98)02716-9].