Ellipsometric Measurement Of Some Usual Optical Material (Film)

The high accurate dispersion curve of film material's optical parameters in specific spectral region is very importance in the area of optical coating design and deposition techniques. Attentions are concentrated on how to compute the accurate spectral dispersion curve of usual film material's optical parameters in the dissertation by using variable angle spectroscopic ellipsometry, one of the international spectroscopic ellipsometry with the highest measurement accuracy at present.Firstly, the theory of ellipsometry is introduced and the sensitivity of ellipsometric parameters with respect to film parameters in ellipsometry and the impact of incident angle on the measurement of ellipsometric parameters are analyzed and discussed, and then simulated concretely in the dissertation.Secondly, the fault of Levenberg-Marquardt algorithm which used in variable angle spectroscopic ellipsometry's data processing software is analyzed. For the purpose of solving the problem in the use of the software, genetic algorithm is introduced into the process of ellipsometric parameters with its good global search capacity and unnecessary initial values. The combination of genetic algorithm and optimal methods based on derivative is of great favor in the programming designed for processing ellipsometric parameters by solving the uncertainty of results obtained by genetic algorithm and the necessity of initial estimate value of optimal methods based on derivative.Finally, a stand-alone data processing software based on the algorithm above has been designed with the help of software of Matlab7.1. By using the software, experimental spectroscopic ellipsometry data of some film materials are analyzed correctly and the fit spectral refractive dispersion curve are with good accuracy compared with the results of measurement system of transmittivity and reflectivity, which proves the effectiveness and reliability of the data process software designed in the dissertation.