Local Strain Distribution and Microstructure of Grinding-Induced Damage Layers in SiC Wafer
The high-angular-resolution electron backscatter diffraction (HR-EBSD) technique has been utilized to evaluate the elastic strain distribution of grinding-induced damage layers in silicon carbide wafers. HR-EBSD analysis, along with transmission electron microscopy observation, revealed that the damage layers formed beneath the wafer surface when the surface was ground by diamond abrasives; the layers were classified hierarchically based on the distribution of elastic strain and lattice defects. In particular, very large elastic strain formed in a defective region of roughly 0.6 μm in thickness, just beneath the ground wafer surface, where lattice defects such as dislocations, stacking faults, and microcracks were introduced inhomogeneously by abrasive interaction and related plastic deformation and fracture. Based on this inhomogeneity, the defective region was itself classified into two types: one, a highly defective region with very large, complicated strain and high defect density; and the other, a basal plane dislocation (BPD)-glide region, with small strain and few BPDs or stacking faults. Beneath the defective region, a strain gradient region of roughly 1.8 μm in thickness, which was unambiguously identified by HR-EBSD strain analysis alone, revealed a monotonic gradient in the dominant compressive strain component, with no grinding-induced defects. Overall, HR-EBSD analysis revealed a nanometer-scale, hierarchical elastic strain distribution in the grinding-induced damage layers.