Infrared Reflectivity of N on N⁺ Si Wafers

Abstract

A method is established to analyse numerically the infrared reflectivity of n on n + Si wafer. This method has been based on the following two assumptions. a) A continuously varying stratified medium can be approximated as a pile of thin homogeneous layers. b) Complex refractive index of n type Si can be expressed by the classical dispersion theory. This method has been proved by the fact that the computed reflectivity of outdiffused Si wafer with known impurity distribution coincides well with the observed values. Computed reflectivity of n on n + Si epitaxial wafers explains well various experimental results: e. g. , the grown film thickness calculated from interference fringes with “dielectrics on metals” approximation is larger than the true value. This method can be used to detect an anomalous impurity diffusion in the epitaxial films near the substrate.