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

We report on properties of amorphous silicon nitride (a-SiNx:H) films deposited by 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) at 120 degreesC 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,: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 similar to1 pA and ON/OF ratio more than 10(6). (C) 2002 Elsevier Science B.V. All rights reserved.