Phase-shifting interferometer/ellipsometer capable of measuring the complex index of refraction and the surface profile of a test surface

A novel interferometer based on a conventional phase-shifting design is presented. This interferometer is capable of measuring both the real and the imaginary parts of the complex index of refraction and the surface profile of a test surface, n, k, and h, respectively. Maximum-likelihood-estimation theory is shown to be a viable means of extracting the three parameters of interest from the measured data. A Monte Carlo simulation showed limited success in estimating the complex index parameters. The results exhibited bias or deviation from the true values for the system configuration examined. The estimate on the surface profile showed excellent agreement with the true value, although the error in the estimate was an order of magnitude worse than in the case in which only the surface profile is to be estimated.