The Mechanism at Work in 40 MHz Discharge SiH₄/NH₃/N₂ Plasma Chemical Vapor Deposition of SiNx Films at Very High Rates

This paper reports a study on the mechanism involved in depositing SiN x films at very high rates by using 40 MHz discharge SiH 4 /NH 3 /N 2 plasma enhanced chemical vapor deposition (PECVD). The quality of the films is comparable to that of films deposited at low rates at a conventional 13.56 MHz frequency. From film deposition experiments, plasma diagnostic studies, and analytical calculation for both frequencies, we have found that the mechanism of depositing SiN x films at very high rates with a 40 MHz discharge can be explained by the higher dissociation efficiency of both NH 3 gas and SiH 4 gas than at a conventional 13.56 MHz. We also report the performance of a thin film transistor (TFT), applicable to LCD switching devices, that was fabricated with SiN x film deposited at the high rate of 350 nm/min with a 40 MHz frequency.