Hydrogenated amorphous silicon thin film transistor fabricated on glass and polyimide substrate at 200°C

The properties of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) on both a glass substrate and on a colorless polyimide substrate were compared. Silicon nitride and hydrogenated amorphous silicon thin films were sequentially deposited at 200°C by plasma-enhanced chemical vapor deposition. The field-effect mobilities of the TFTs on glass and polyimide substrates were 0.35 and 0.42 cm²V^-1 s^-1, respectively. The field-effect mobility of TFTs on the polyimide substrate was higher than that on the glass substrate. This was caused by the reduced surface roughness of the silicon nitride and hydrogenated amorphous silicon films on the polyimide substrate. Both on glass and polyimide substrates, the subthreshold voltage swing was about 0.5 V/dec and an on/off current ratio over of 10 ⁷ was achieved. The superior electrical characteristics resulted from the increased hydrogen content in the hydrogenated amorphous silicon film and a higher breakdown voltage of the silicon nitride film was obtained.