Multilayer thin film thickness measurement using sensitivity separation method

This paper, for the first time, proposed a new sensitivity separation (SS) method for measuring thicknesses of multilayer thin-film stack with high efficiency and accuracy. Through the analysis of the relationship between the film parameters and the mean misfit error (MSE), a parameter called sensitivity is defined. With this parameter, an estimated rational thickness is assigned to a layer with lower sensitivity first, and then the layer thickness with high sensitivity is further obtained by optimization techniques. This method will greatly reduce the searching range and increase the iterating efficiency. It is a pretreatment method and it can be used with other optimization methods. Both theory and simulation results are provided in detail. The uncertainty problems are discussed and examples are given to verify the effectiveness of this method.