Non-destructive measurement of SiC Epitaxial Layer Thickness Using FTIR Spectroscopy with Cauchy Dispersion Optimization

Abstract

Accurate measurement of SiC epitaxial layer thickness is crucial for third-generation semiconductor device performance. This paper proposes a comprehensive measurement method combining interference optics principles with Cauchy dispersion model and numerical optimization algorithms. The method establishes a thickness solution model based on interference fringe extrema identification in FTIR reflection spectra. A nonlinear least-squares optimization algorithm jointly optimizes thickness and dispersion coefficients. To address multi-beam interference and phonon resonance effects near 797 cm⁻¹, we develop compensation strategies including K-M transformation and frequency-domain filtering. Experimental validation using FTIR spectra at 10° and 15° incident angles demonstrates excellent measurement accuracy: the epitaxial layer thickness is determined as 8.06 ± 0.41 μm, with relative deviation less than 0.15% between different angles. The theoretical model shows strong agreement with experimental data (correlation coefficient 0.89 in non-resonant regions). This method provides reliable technical support for quality control in SiC manufacturing, meeting industrial requirements with measurement uncertainty below 5%.