Measurement Of 4H-SiC Homoepifilms Based On FTIR Technique

Based on the 4H-SiC homoepitaxy infrared reflectance spectrum, thickness determination of epifilms was studied in this thesis at first. Considering the disadvantage of traditional infrared interference method and combining with the classical dielectric function, some modifications have been developed to improve the traditional method. The mean relative error of the measured results has been decreased from 9.2% to 0.26%, and the calculation is very stable. As an important factor in the determination of layer thickness of Si and GaAs, effect of the additional phase shift on thickness determination of SiC has also been discussed in this work. According to the measured results, influence of the additional phase shift increases with decreased layer thickness and exists in nano-scale. As to samples micron-sized in this work, the influence of additional phase shift can be neglected. During the improvement of the traditional method, a new fitting model for thickness determination which aims at the fitting of the fringe orders difference between wave peaks and troughs has been proposed. Since the variation of the refractive index with the incident frequency is tiny, the new fitting model is approximately linear. Just for the linear characteristic, the fitting process is simple, quick, and the fitting result is in great agreement with results obtained from the improved method above.Taking into account the interference superposition method of multiple beam, together with the dielectric theory of SiC, important parameters of epilayer and substrate have been extracted through curve fitting of the reflectance spectrum, for example, the phonon frequency, free carrier concentration and mobility. Curve fitting method has also been applied to Si substrate 3C-SiC heteroepitaxy infrared reflectance spectrum in this work. Layer thickness has been extracted through curve fitting method, as the plasmon frequency fails to be stable, free carrier concentration and mobility have not been extracted eventually. Some assumptions have been given to explain this phenomenon, but more research is needed to find the reason.