Anisotropic material removal in ultra-precision micro grinding of single crystal 4H-SiC: Process signals and surface damage evolution

Single crystal 4H-SiC, as a wide-bandgap semiconductor substrate material, is prone to crystallographic anisotropy surface damage during ultra-precision grinding, which degrades grinding surface condition. To reveal the differences in material removal behavior under different crystal planes and crystallographic directions, this study carried out grinding experiments using a hemispherical grinding wheel. C, M and A planes of single crystal 4H-SiC were selected for the analysis of process signal responses and surface morphology evolution. In-situ monitoring of grinding force and acoustic emission was conducted to evaluate the morphology of grinding grooves and characterize the features of microcracks and microchipping. The results showed that the process signal response and the associated surface damage were governed by the crystal-plane structure, with C plane exhibiting the strongest orientation sensitivity. All three crystal planes enabled controllable shaping at a millimeter-scale radius of curvature. Whereas the profile error and roughness results exhibited pronounced dependence on the plane crystallographic orientation. The grinding force increased with the removal depth, with the normal force being most sensitive to crystallographic direction differences. Frequency domain results indicated that F _x and F _y maintained stable characteristic peaks at around 245 Hz and its harmonics, while F _z tended to exhibit broadband energy enhancement. The acoustic emission signal amplitude and intermittency increased with removal depth, and transient bursts were observed with the high propensity for crack propagation and microchipping. The observed anisotropy can be interpreted as reflecting orientation-dependent deformation and fracture behavior, including differences in crack propagation tendency.