Complete Optical Characterization of Non-Uniform SiOx Thin Films Using Imaging Spectroscopic Reflectometry

Complete optical characterization of SiOx films non-uniform in thickness is performed using imaging spectroscopic reflectometry. It is shown that by using this technique it is possible to determine the area distribution of the local thickness (area map) of these films with arbitrary shape of this thickness non-uniformity. Furthermore, it is shown that the SiOx films studied do not exhibit the area non-uniformity in dispersion (material) parameters and optical constants. This is possible because imaging spectroscopic reflectometry enables us to determine the area distributions of local thickness and local refractive index simultaneously in an independent way under the assumption that a suitable dispersion model of the refractive index of the films is used. In this paper the dispersion model corresponding to the Cauchy's formula is used. On the basis of this dispersion model the spectral dependence of the refractive index of the SiOx films is determined. The method presented can be used to characterize the nonuniform films consisting of other non-absorbing materials.