Research on Thickness Measurement of SiC Epitaxial Layer Based on Equal-Inclination Interference

• 1、Electronics and Information Engineering School, Liaoning Technical University, Huludao 125105

Abstract：To address the demand for accurate thickness measurement of silicon carbide (SiC) epitaxial layers, this paper constructs a thickness calculation model suitable for dual-beam and multi-beam scenarios based on infrared reflectance spectroscopy and equal-inclination interference theory. It resolves key issues in traditional measurements, such as interference fringe disturbance and non-constant refractive index. Firstly, a dual-beam interference model is established, and the thickness calculation formula is derived by combining optical path difference and phase difference. Secondly, a third-order Cauchy dispersion model is introduced to describe the refractive index-wavelength relationship, and parameters are optimized using a nonlinear least squares algorithm. The results show that the SiC thicknesses at incident angles of 10 and 15 are 6.4212 μm and 6.8031 μm respectively, with a relative difference of only 1.6%. Finally, the core necessary conditions for multi-beam interference are derived (interface reflectivity threshold R?R? > 0.01, optical path difference < coherence length). It is determined that multi-beam interference exists in silicon wafer data, and the calculated thicknesses are 10.2212 μm (10 ) and 10.1772 μm (15 ). If SiC is affected by multi-beam interference, the optical path difference condition is disrupted by superimposing the wafer, and the final corrected thicknesses are 8.463 μm (10 ) and 8.532 μm (15 ). Experimental verification indicates that the proposed model features high measurement accuracy and strong scenario adaptability, providing technical support for the thickness detection of semiconductor materials.?????

Keywords： Semiconductor Technology Silicon Carbide (SiC) Epitaxial Layer Equal-Inclination Interference Multi-Beam Interference Cauchy Dispersion Model