Plasma-Induced Interfacial Layer Impacts on TFETs With Poly-Si Channel Film by Oxygen Plasma Surface Treatment

Abstract

In this paper, tunnel field-effect transistor (TFETs) with polycrystalline-silicon (poly-Si) channel film has been demonstrated to exhibit better short-channel effects (SCEs) immunity than conventional poly-Si thin-film transistors. Oxygen (O2) plasma surface treatment before the deposition of gate dielectric can produce a plasma-induced interfacial layer, which can passivate the interface trap state density ~25%. In addition, the ON-state transconductance $G_{m}$ is improved ~54% due to the decrease of tunneling distance of band-to-band tunneling. However, the $G_{m}$ improvement of poly-Si TFETs is decreased with the scaling down of channel length due to the less trap state density in the small area of poly-Si channel film. Moreover, the O2 plasma surface treatment can also reduce the grain boundary trap state density of poly-Si channel film ~37%, which can reduce the trap-assisted tunneling current of poly-Si TFETs to suppress the length dependence of drain leakage current in the subthreshold region. Consequently, the O2 plasma surface treatment can not only improve the ON-state current and OFF-state leakage current of poly-Si TFETs, but also further improve the SCEs of poly-Si TFETs.