Phase-Spectral Ellipsometry Method for Nondestructive Control of the Chemical Composition of thin Metal-Oxide Heterostructures

The problem of insufficient accuracy, informativeness and efficiency of recognition of the structure and composition of inhomogeneous surface layers of thin metal-oxide heterostructures during nondestructive testing by spectral optical methods is considered. It is noted that the currently available methods of studying such layers, as a rule, are destructive in nature. To improve the accuracy, informativeness and efficiency of nondestructive testing of the chemical composition of thin metal-oxide heterostructures, a method of phase-spectral ellipsometry has been developed. In this method, the results of ellipsometric measurements of reflected radiation of various wavelengths are used to determine the distribution function of the complex refractive index of an inhomogeneous surface layer along its depth. To implement the proposed method, a phase spectral ellipsometer circuit with a wavelength as a control signal of the feedback channel has been created. The method of phase-spectral ellipsometry is used to control the distribution of chemical composition over the depth of thin metal-oxide heterostructures on the surface of stainless steel Cr18–Ni10–Ti, oxidized at low temperatures and oxygen pressures. When comparing the obtained results with independent Auger profiling data of oxidized samples, it was found that the distribution of the chemical composition over the depth of the oxide corresponds to the independent Auger data. It is shown that the method of phase-spectral ellipsometry makes it possible to clearly separate and identify various oxidized forms of the alloy. The presented method can be used for nondestructive and especially in-situ study of the distribution of chemical composition over the depth of ultrathin inhomogeneous surface oxides.