6H-SiC单晶紫外光催化抛光中光照方式和磨料的影响

研究紫外光辅助催化抛光6H-SiC单晶。用分光光度法定性检测不同光催化反应时间下甲基橙颜色变化和羟基自由基(·OH)浓度，研究无光照、光照抛光盘、光照抛光液3种光照方式及金刚石、碳化硅、二氧化硅、二氧化钛、硅溶胶5种磨料对6H-SiC单晶抛光的影响。结果表明:随着光照时间增加，·OH浓度增加；在3种光照方式下，不同磨料的材料去除率(MRR)均呈现光照抛光液>光照抛光盘>无光照的规律，且光照抛光液时的MRR比无光照时的MRR提升了18%～58%。随磨料硬度降低，光催化辅助作用对MRR的提高幅度升高，即紫外光催化辅助作用越明显；金刚石、碳化硅、二氧化硅、硅溶胶4种磨料抛光后的表面粗糙度都随MRR的增大而减小，但二氧化钛磨料的则相反，原因是二氧化钛磨料同时兼作光催化剂，增强了SiC表面的化学反应速率，使其化学反应速率大于机械去除速率。 

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.