Dielectric performance of low temperature silicon nitride films in a-Si:H TFTs

We report on properties of amorphous silicon nitride (a-SiN _x :H) films deposited by 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) at 120 °C and their performance as a gate dielectric in amorphous hydrogenated silicon (a-Si:H) thin film transistors (TFTs). It was found that the films with [N]/[Si] ratio higher and lower than about 1.5 can be clearly distinguished due to different physical properties, structure of electronic defects and better electrical quality of more N-rich materials. a-Si:H TFTs incorporating N-rich a-SiN _x :H dielectric layers exhibited field effect mobility of 0.9–1 cm 2 / V s , threshold voltage of 4 V, subthreshold slope of 0.5 V/dec, OFF-current ∼1 pA and ON/OF ratio more than 10 ⁶.