基于Drude-Lorentz模型与红外反射光谱干涉条纹的碳化硅外延层厚度反演方法OA

To address the problem of large errors in SiC epitaxial layer thickness measurement caused by the simplified constant refractive index in traditional double-beam interference models and the neglect of carrier-phonon coupling effects,this paper proposes a thickness inversion method based on the Drude-Lorentz model and interference fringes in infrared reflectance spectra.The method takes n-type 4H-SiC homoepitaxial wafers as the research object.A complex refractive index dispersion model incorporating carrier-phonon coupling is employed to describe the dispersion characteristics in the infrared band.After preprocessing the infrared reflectance spectrum,extreme points of the interference fringes are extracted to obtain their wavenumber sequence,and the physical relationship between the SiC epitaxial layer thickness and the interference phase is established.By discretizing a preset thickness interval into several nodes,the theoretical refractive index corresponding to each node is calculated.The n-type 4H-SiC epitaxial layer thickness is accurately determined by minimizing the residual sum of squares between the theoretical refractive index and the experimental refractive index at the extreme points.Experimental results show that the residual distribution of the inverted thickness obtained by this method is approximately normal without significant systematic deviation,with a combined uncertainty standard deviation of 0.061μm.This provides a high-precision and high-efficiency solution for thickness measurement of semiconductor thin-film materials.