Solid body and liquid superficial structure study by ellipsometry considering mathematical inverse problem incorrectness. 2. Features of the return problem at research of the superthin superficial films on semiconductors

The work analyses the features of a return problem ellipsometry, evident at definition of a full set of parameters of reflecting system with a superthin superficial film. The way of the solution of a return problem was developed: the approach to the solution consisting of two consecutive stages is described. Criterion of an optimum values choice of corresponding parameters is formulated for each stage. Optimum values of parameters of a substrate are determined at the first stage, as well as value of parameters the films corresponding to a point of an absolute functional minimum of a return problem. For a case of midget thickness of a film these values are significantly differ from the true film parameters because of experimental errors and discrepancies in the model of the investigated object. The second stage is an obvious consequence of the first one and represents realization of the approach stated in the previous work. At this stage the solution of a return problem the optimum values of parameters of a substrate defined at the previous stage are set and by means of criteria of selection offered in work [1] optimum values of parameters of a film are determined. The stated approach to the solution of mathematically incorrect return problem is successfully tested in numerical experiment for different variants of experimental errors. Influence of the broken layer on substrate surfaces is also discussed in the work.