Effects of lights modes and abrasives on UV-photocatalysis assisted polishing of 6H-SiC single crystal

UV-photocatalysis assisted polishing of 6H-SiC single crystal was studied. The color change of methyl orange and the concentration of hydroxyl radical (·OH) under different photocatalytic reaction time were qualitatively detected by spectrophotometry. The effects of three kinds of illumination methods, namely no light, light polishing plate and light polishing liquid, and five kinds of abrasives namely diamond, silicon carbide, silicon dioxide, titanium dioxide and colloidal silica on the polishing of 6H-SiC single crystal were studied. The results show that the concentration of ·OH increases with the increase of illumination time. Under all three illumination modes, the material removal rate (MRR) of different abrasives showed the same pattern, which is light polishing liquid>light polishing disk>no light, and the MRR of at light polishing liquid is 18% to 58% higher than that at no light. Meanwhile, the enhancement of MRR by UV-photocatalysis is greater with the decrease of abrasive hardness, which means that UV-photocatalysis shows greater auxiliary effects. The surface roughness of wafers polished with diamond, silicon carbide, silicon dioxide and colloidal silica decreases with the increase of MRR, while that of wafers polished with the titanium dioxide shows the opposite rule. The reason is that titanium dioxide acts as photocatalyst at the same time, which enhances the chemical reaction, resulting in the chemical reaction rate of SiC surface is greater than the mechanical removal rate.