Properties of hydrogenated amorphous silicon thin film transistors fabricated at 150°C

Hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) were fabricated by plasma enhanced chemical vapor deposition system. Silicon nitride and a-Si:H were deposited at 150°C. The a-Si:H TFT had field effect mobility of 0.75 cm2/V s, sub-threshold voltage swing of 0.5 V/dec and on/off current ratio >1.5 × 106. The hydrogen was added during the gate insulator of SiNx deposition. The deposition rate of SiNx decreased and the SiH/NH ratio increased with the increasing H2 gas flow rate. The a-Si:H TFT fabricated with the gate insulator with larger SiH/NH ratio had smaller threshold voltage and less threshold voltage shift after the gate bias stress (30 V, 103 s).