Development of a method to evaluate the stress distribution in 4H-SiC power devices

We detected all components of the deformation potential constants of 4H-SiC by first-principles calculations and developed a method to estimate the stress distribution in 4H-SiC power devices by Finite Element Method (FEM) and Raman spectroscopy. The values of b A1 , a E2 , and b E2 obtained by calculations agreed well with experimental results, while those of a A1 , b E1 , and c E2 were about 45% larger. The relationship between phonon frequency and stress was nonlinear as shear stress increased. The multistep FEM analysis reproducing the manufacturing process is also conducted. The stress distribution was converted to the Raman shift and compared with results of micro-Raman spectroscopy. Except for the interface between SiC and the electrode, the analysis results agreed well with the experimental results. It was found that a compressive stress of about 200 MPa at the SiC/electrode interface and a resolved shear stress of about 20 MPa at the epilayer/substrate interface were generated.