光助芬顿反应对6H-SiC化学机械抛光的影响

为提高6H-SiC晶片化学机械抛光的材料去除率(MRR)并改善其表面质量,采用光助芬顿反应体系对6H-SiC晶片进行化学机械抛光,研究紫外光功率、抛光液pH值、H2O2质量分数和Fe2+浓度对6H-SiC晶片抛光效果的影响。使用原子力显微镜观察6H-SiC晶片表面质量,采用纳米粒度电位仪测量抛光液中SiO2磨粒的粒径分布及Zeta电位,利用可见分光光度法检测溶液中羟基自由基(·OH)的浓度并通过紫外-可见光谱分析紫外光的作用机制。结果表明:引入紫外光提高了6H-SiC的MRR,增大紫外光功率,MRR也随之增加;随pH值、H2O2质量分数和Fe2+浓度的升高,MRR先增大后减小;pH值影响磨粒间的静电排斥力及磨粒的分散稳定性,从而影响6H-SiC的MRR;与采用芬顿反应体系的抛光液相比,采用光助芬顿反应体系的抛光液中产生的·OH数量较多,说明紫外光能够增加反应体系中·OH的数量,从而促进6H-SiC晶片的表面氧化,提高6H-SiC晶片的MRR,并改善其表面质量。

Effect of Photo-Fenton Reaction on Chemical Mechanical Polishing of 6H-SiC

In order to improve the material removal rate(MRR)and improve the surface quality of 6H-SiC wafer,the photo-Fenton reaction system was used for chemical mechanical polishing(CMP)of 6H-SiC wafer.The influences of ultraviolet light intensity,pH values of slurry,H2O2 mass fraction and Fe2+concentration on the polishing effects of 6H-SiC wafer were examined.The surface morphology of the 6H-SiC wafer were observed with atomic force microscope(AFM).The particle size distribution and Zeta potential of SiO2 abrasive particles in the slurry were measured with nanoscale potentiometer.The concentration of hydroxyl radical(·OH)in the solution were detected with visible spectrophotometry and the mechanism of ultraviolet light was analyzed by UV-visible spectroscopy.The results indicate that the MRR of 6H-SiC is increased with the introduction of ultraviolet light,and the MRR is gradually increased with the increasing of the ultraviolet light power.With the increasing of pH values,H2O2 mass fraction and Fe2+concentration,the MRR of 6H-SiC is increased firstly and then decreased.The pH values affect the electrostatic repulsion between the abrasive grains and the dispersion stability of the abrasive grains,thereby affecting the MRR of 6H-SiC.Compared with the polishing solution using the Fenton reaction system,the polishing solution using the photo-Fenton reaction system produces much more hydroxyl radica,indicating that ultraviolet light can increase the amount of hydroxyl radica in the reaction system,thereby promoting the surface oxidation of SiC wafer,increasing the MRR of 6H-SiC and improving its surface quality.