Different Hydrogen Passivation Mechanisms between Low-Temperature and High-Temperature Poly-Si TFT's

We have investigated the different hydrogen passivation effects on low-temperature (LT) processed and high-temperature (HT) processed poly-Si thin-film transistors (TFT's). The hydrogen passivation on LT poly-Si TFT's results in the increase of the field-effect mobility and the decrease of the threshold voltage, while the hydrogenation increases the field-effect mobility and decreases the leakage current in HT poly-Si TFT's. The effective trap-state densities of LT poly-Si TFT before and after 5 h of hydrogenation are estimated at about 4×1012/cm2 and 1.5×1012/cm2, while those of HT poly-Si TFT are about 1.5×1012/cm2 and 1.2×1012/cm2, respectively. The activation energy of HT poly-Si TFT has been increased significantly in the off state with hydrogen passivation, whereas that of LT device has been decreased remarkably in the on state.