Performance improvement of poly-Si tunnel thin-film transistor by NH3 plasma treatment

Abstract

In this paper, low-temperature polycrystalline silicon (poly-Si) tunnel thin-film transistors (tunnel-TFTs) are demonstrated to show excellent short-channel effects immunity due to their special current transport mechanism: inter-band tunneling. The ammonia (NH3) plasma surface treatment before the deposition of gate dielectric can significantly reduce the grain boundary trap state densities (NGB) of poly-Si channel film and the interface trap state densities (Nit) at the gate-oxide/poly-Si interface. About 27% reduction of NGB by NH3 plasma surface treatment can reduce the minimum drain current ~0.51× and improve the subthreshold slope due to the suppression of trap-assisted tunneling, which dominates the current transport in the subthreshold operation region. In addition, about 37% reduction of Nit by NH3 plasma surface treatment can significantly enhance the on-state current ~2.86× due to the increase of band bending of poly-Si channel potential, which can decrease the tunneling distance to increase the electron tunneling probability. Consequently, the performance improvement of poly-Si tunnel-TFTs by the NH3 plasma surface treatment would be helpful for the development of system-on-panel and three-dimension integrated circuits.