Spectroscopic Fourier methods for thickness measurements of thick uniaxial wafers, with dispersive birefringence, using polarimetric techniques

摘要

This letter describes the measurement of the thickness of a thick uniaxial sample with a dispersive birefringence, using Fourier methods and standard polarimetric techniques. The formalism is also similar to, and easily adapted to, non-normal incidence thin-film thickness measurements. In a previous paper, a spectroscopic half-wave method for uniaxial wafer thickness measurements was investigated. A number of corrections for the dispersion had to be included in the analysis. It is demonstrated here that the fast Fourier transform over the recorded interval is a more robust measurement, with higher accuracy, and higher repeatability. The signal is treated as a standard frequency modulated signal. An undoped thick wafer of 4H-SiC and doped 4H-SiC are studied as examples.