Influence of Deposition Conditions on the Properties of Silicon Nitride Films Prepared by the ECR Plasma CVD Method

Abstract

Properties such as the refractive index, etch rate and resistivity of silicon nitride films (SiN) prepared by an electron cyclotron resonance (ECR) plasma CVD method have been studied and correlated with their compositional and structural properties such as the N/Si ratio, bond configurations, spin density and film density. The microwave power, SiH₄ flow rate under a constant flow rate of N₂ gas and gas pressure during depositions, selected as the deposition parameters, were 50–500 W, 3–12 sccm and 4×10^-4-4×10^-3 Torr, respectively. The refractive index showed a unique correspondence to the N/Si ratio, but Si–H bonds had to be simultaneously taken into consideration in order to explain the dependency of the etch rate. The film density also had a strong influence on the film properties. The resistivity had a strong correlation with spin density, though it was also correlated with other properties such as the N/Si ratio. The compositional and structural properties of the films can be qualitatively explained by the optical emission spectra obtained from the ECR plasma of a SiH₄–N₂ mixture gas.