Research on Measurement Methods for Silicon Carbide Epitaxial Layer Thickness Based on Optical Interference Principles

Abstract

As a simple and non-destructive analytical technique, infrared interference spectroscopy is of great value in improving device manufacturing performance due to its ability to accurately measure epitaxial layer thickness. Based on a single-reflection and transmission model, this paper establishes theoretical models for calculating epitaxial layer thickness under two scenarios depending on whether the substrate refractive index is greater or smaller than that of the vacuum. By utilizing the property that substrates with higher carrier concentrations exhibit larger refractive indices, and combining the optical path differences between adjacent beams, an overall interference expression is derived from interference principles. This yields the relationship between fringe order and wavelength, leading to an algorithmic formula for epitaxial layer thickness. Meanwhile, variations in reflectivity are treated as shifts in interference peaks during experiments; adjacent peak values are extracted, corresponding wavenumbers and interference fringe orders are identified, and the thickness is calculated under a given angle of incidence. Under these conditions, two methods are employed to determine the refractive index of the epitaxial layer. In summary, this study provides a theoretical analysis of epitaxial layer thickness and verifies its accuracy through reliability assessments. The proposed methodological framework holds potential for broader application.