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 ℃ . The films are dense and transparent in the visible region. The peak frequency of the Si–N 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 Si–N 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 Si–N bond due to the increase in the Si–O bond density.