Stress-induced cracks in triangular defects of thick 4H-SiC homoepitaxial layers

Our research investigated stress-induced cracking in triangular defects within thick 4H-SiC homoepitaxial layers. While rarely observed in thinner layers, cracks were frequently identified along the sides of triangular defects in thicker layers, suggesting a correlation with internal stress accumulation. Through surface and cross-sectional analyses, we characterized the morphology of these defects and employed molten KOH etching to examine their structural properties. The etching results revealed an increase in external pits with defect growth, indicating an expanding area of influence and rising stress levels within the defect region. Raman spectroscopy and TEM analysis further identified a transition layer between defected and defect-free regions, marking a shift from 4HSiC to 3C-SiC, accompanied by stacking fault-induced stress. Our findings indicate that cracks begin to form along the sides of the defect when stress reaches a critical threshold. This cracking acts as a mechanism to relieve the accumulated stress. This study provides insights into the evolution of triangular defects and highlights the importance of stress management in thick 4H-SiC epitaxial layers for high-performance applications.