Research on SiC epitaxial layer thickness measurement based on infrared interferometry

Abstract

Silicon carbide, as a core material of third-generation semiconductors, has epitaxial layer thickness precision that plays a decisive role in device performance. Infrared interferometry is a key technique for non-destructive measurement of this parameter. Based on the principles of geometric optics and wave optics, this paper constructs a quantitative characterization model for the relationship between epitaxial layer thickness and reflectance response for dual-beam interference mechanisms, combined with the experimental refractive index formula for 6H-SiC crystals. The data processing stage employs preprocessing procedures such as detrending and normalization to extract interference features, uses peak finding algorithms to precisely locate interference extrema, and then applies linear regression to avoid interference order ambiguity, ultimately achieving high-precision inversion of SiC epitaxial layer thickness. For the physical process of multi-beam interference, this paper systematically derives its formation conditions from four aspects: energy attenuation behavior, light source parameter stability, phase jump continuity, and medium spatial uniformity. A multi-beam interference coherent superposition model is then constructed, and Fourier transform techniques are applied to perform frequency domain analysis of reflectance spectra to extract the dominant interference frequency. Empirical validation using silicon wafer sample data yields high-precision thickness measurements consistent with multi-beam theory. The model adopted in this paper integrates solid theoretical foundations with highly feasible algorithmic architecture, accurately applicable to the quantitative determination of SiC epitaxial layer thickness and demonstrating universality for extension to thickness detection of other semiconductor thin-film materials, providing a reliable technical approach for characterizing core parameters of semiconductor materials.