The anomalous behavior of hydrogenated/unhydrogenated polysilicon thin-film transistors under electric stress

The characteristics of high-temperature processed thin-film transistors (TFT's) with/without plasma hydrogenation under the stress condition of V/sub ds/=-15 V and V/sub gs/=0 V have been investigated and compared. It is found that, after stress, the subthreshold swing is greatly improved for unhydrogenated TFT's but not for hydrogenated TFT's. Also, the off-state current is deteriorated for unhydrogenated TFT's but, on the contrary, it is improved for hydrogenated TFT's. A model that takes the effect of hydrogen passivation into account is proposed to interpret the anomalous behavior of TFT's under electric stress.