IR Spectroscopic Study of Silicon Nitride Films Grown at a Low Substrate Temperature Using Very High Frequency Plasma-Enhanced Chemical Vapor Deposition

Abstract

Hydrogenated amorphous silicon nitride (a-SiN x :H) films have been grown from a SiH 4-N 2 gas mixture through very high frequency (VHF) plasma-enhanced chemical vapor deposition (PECVD) at 50˚C. The films are dense and transparent in the visible region. The peak frequency of the SiN stretching mode in the IR absorption spectrum increases with increasing N-H bond density, which is similar to the behavior of a-SiN x :H films grown from SiH 4-NH 3 gas. During storage in a dry air atmosphere , the Si-O absorption increases. A large shift in the peak frequency of the SiN stretching mode in the initial stage of oxidation, which is higher than the shift expected from the increase in the N-H bond density, is mainly caused by the change in the sum of electronegativity of nearest neighbors around the SiN bond due to the increase in the Si-O bond density.