A novel liquid film shearing polishing technique for silicon carbide and its processing damage mechanisms

As a third-generation semiconductor material, single-crystal 4H-SiC possesses exceptional properties such as high bandgap, high breakdown voltage, high thermal conductivity, and high electron mobility. However, due to its significant chemical inertness and high hardness, the surface quality after processing is often poor and prone to damage, which severely limits the performance of high-end equipment. To address this, this study proposes a novel liquid film shearing polishing (LFSP) technique to enhance the surface quality of 4H-SiC and reduce subsurface damage (SSD). By employing scanning electron microscopy, transmission electron microscopy, positron annihilation spectroscopy and photoluminescence, the material removal mechanism and microstructural evolution during polishing were systematically studied, and SSD behavior was analyzed in depth. The results demonstrate that, compared to mechanical polishing samples, the LFSP samples exhibit superior surface quality with effective removal of SSD. The material removal rate for 4H-SiC is 25.6 nm/min, with roughness R_a decreasing from 21.87 nm to 0.5 nm over 60 min, and the damage layer thickness reduced to 10 nm. This study indicates that LFSP can achieve high-quality, low-damage polishing of 4H-SiC.