Interfaces and roughness in a multilayer silicon structure

The results of spectral ellipsometric studies of a complex multilayer system consisting of a Si substrate, a SiO2 layer, and a layer of polycrystalline Si are reported. A method for analysis of the multilayer structure is suggested; the method is based on a heavy dependence of experimental data of spectral ellipsometry on the depth of penetration of probing radiation at various wavelengths in the visible region of the spectrum. The actual structure of the system and the parameters of the layers are determined. Processing the ellipsometry data made it possible to identify a natural rough surface oxide SiO2 layer and also a transition layer at the interface between the layer of polycrystalline Si and the layer of natural oxide. The composition and thickness of these layers are determined. It is shown that the deposited Si layer consists of a mixture of the crystalline and the amorphous phases; the percentage of these phases is determined.