Composition and mechanical properties of silicon nitride thin films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition technique

The composition of silicon nitride films deposited from a mixture of Ar, N2, and SiH4, at low temperatures using an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) technique has been studied using Rutherford Backscattering Spectroscopy (RDS) and 15N('H, alpha, gamma)12C Nuclear Reaction Analysis (NRA). The nitrogen-to-silane gas flow rates ratio (N2:SiH4) in the mixture of precursors, and the deposition pressure P have been found to have a pronounced effect on the composition of the films. For a given P the amount of silicon (Si) and hydrogen (H) in the films decreases, while that of nitrogen (N) increases with increasing N2:SiH4 ratio. When P is varied for a given N2:SiH4 ratio the amount of Si and H in the films increases with P, while that of N decreases. The mechanical stress in these films is typically compressive and increases with the N2:SiH4 ratio, the substrate temperature T(S), the total gas flow rates of precursors V, and the RF and microwa ve power. It decreases only with P. These results indicate that the films with a minimum sum require to be deposited at a high P in addition to a low N2:SiH4, V, T(S), RF and MW power.