Plasma passivation effects on polycrystalline silicon thin-film transistors utilizing nitrous oxide plasma

Abstract

A novel defect passivation process in polycrystalline silicon (poly-Si) thin-him transistors (TFTs) utilizing nitrous oxide (N2O) plasma has been performed to significantly improve the electrical characteristics of poly-Si TFTs, For example, the on/off current ratio increased to 6.58x10(6); the threshold voltage decreased to 0.55V, and a the field effect mobility increased to 48.2 cm(2)/Vs. The distribution of N incorporated in this oxide and these poly-Si films was examined by means of secoudary ion mass spectroscopy (SIMS) and Auger-electron spectroscopy (AES). It is believed that the nitrogen radicals which dissociated from the N2O gas as well as the hydrogen radicals with dissociated from the residual H2O can both diffuse into the active poly-Si layer to passivate the grain-boundary defect states and accumulate at the gale SiO2/poly-Si interlace lo reduce the interface state density. Thus, the hot-carrier reliability of TFTs M-as also enhanced after the N2O plasma treatments.