The influence of concentration of hydroxyl radical on the chemical mechanical polishing of SiC wafer based on the Fenton reaction

Aiming at the chemical mechanical polishing (CMP) of single crystal silicon carbide (SiC) based on the Fenton reaction, the concentration of hydroxyl radical (center dot OH) produced in the Fenton reaction and its influence on the chemical reaction rate of SiC were detected by using visible spectrophotometry. The formation rule of center dot OH using Fenton's reagents with different components, and the influence of Fenton's reagents on CMP of SiC wafer, were studied. The experimental results show that center dot OH can chemically react with the SiC surface to produce an SiO2 oxide layer with low hardness. The larger the concentration of center dot OH, the quicker the chemical reaction rate on the SiC surface and the better the polishing quality of SiC wafer. The Fe2+ and H2O2 concentrations, and pH in the Fenton's reagent influence the concentration of center dot OH produced in the Fenton reaction, therefore influencing the polishing quality of SiC surface. Excessive Fe2+ concentration (FeSO4 >= 0.03 wt.%) and pH value (pH >= 5) can lead to the production of flocculent complexes or precipitates during the reaction while an excessive amount of H2O2 (H2O2 >= 10 wt.%) can capture center dot OH produced in the Fenton reaction, thus resulting in a poor polishing quality of SiC surface. Under the condition where the pH value, Fe2+ and H2O2 concentrations are 3, 0.02 wt.% and 5 wt.%, respectively, high-concentration center dot OH can be produced in the Fenton reaction. Based on this, a smooth surface of SiC wafer with a roughness of 0.1869 nm Ra can be obtained after polishing for 1 h.