Research On Ellipsometric Measurement Of Thin Film Based On Adaptive Genetic Simulated Annealing Algorithm

Ellipsometry is an advanced method to measure optical properties of films and study material surface. Because of the merits of high precision, high speed, nondestructive and non-disturbing, numerous applications of this method are found in a variety of fieds including physics, chemistry, material and biomedicine, etc. However, in the Ellipsometric measurement, we can not get the film parameters directly because the ellipsometer equation is a transcendental equation, ellipsometric data processing is an important part of ellipsometry method. The ellipsometric data inversions for various practical films have being always the hotspot and difficulty for researchers. In this dissertation, we take a research of the process of the application of adaptive genetic simulated annealing algorithm in ellipsometric measurement of thin films. The main task includes three parts.Firstly, the development history and status quo of ellipsometry and ellipsometric data processing are summarized. The theory of ellipsometry is introduced, what's more, the characteristic matrixs for the monolayer films and multilayer films are also educed. These provide theoretical basis for the next work.Secondly, genetic algorithm and simulated annealing are discussed in detail. The two algorithm stand or fall are compared. Combining merits of genetic algorithm and simulated annealing algorithm and improving the genetic operator, a new algorithm named adaptive genetic simulated annealing algorithm is presented to solve the ellipsometric data processing problem.Finally, using the new algorithm to invert the models of single-layer absorbing films, double-layer absorbing films and three-ply transparent films are analyzed and studied. The results obtained may be a good example to demonstrate the feasibility and efficiency of the approach to solve more complex inverse problems in ellipsometry.