Correlation of refractive index and Si content of silicon oxynitride films.
01 January 1989
The refractive index of plasma-deposited silicon nitride and silicon oxynitride films can be used to estimate the atomic percent Si in the films. This linear correlation is different from previously reported correlations and can even be applied to high temperature LPCVD silicon oxynitride films. While the refractive index can be used to monitor plasma nitride and plasma oxynitride films, it is important to remember that oxynitride films with different N and O contents can have the same refractive index. The Bruggeman effective medium approximation with Si and silicon dioxide as the two phases can be used to model the correlation. Although physically unreal, the model suggests that the large polarizability of Si in the film controls the refractive index and that the polarizabilities of voids, H, N, O, and F can be lumped together with an effective refractive index of 1.46