Basic research on chemical mechanical polishing of single-crystal SiC—Electro–Fenton: Reaction mechanism and modelling of hydroxyl radical generation using condition response modelling

Abstract

Hydroxyl radicals (·OH) can effectively oxidise and corrode single-crystal SiC, and are used for chemical mechanical polishing (CMP). The generation rate of ·OH and its total concentration produced by a CMP process based on the Electro-Fenton reaction can be effectively controlled by regulating the electric field parameters, thereby improving the polishing effect of SiC. The effects of initial H2O2 concentration, Fe3O4 concentration, and voltage on ·OH were studied, and the reaction mechanism was also revealed. Moreover, a conditional-response mathematical model for ·OH generation was established. The generated ·OH first increased and then decreased with increasing initial H2O2 concentration, Fe3O4 concentration, and voltage. When these parameters were 7.5 wt%, 1.5 wt% and 0.75 V, respectively, a maximum total ·OH concentration of 9545.776μmol could be obtained. The conditional-response mathematical model established with initial H2O2 concentration, Fe3O4 concentration, and voltage can accurately predict the total generated ·OH concentration with a relative prediction error of less than 10%. Controlling the electric field parameters can accelerate the conversion of Fe3+ to Fe2+, increasing Fe2+ concentration and enhancing catalytic effect. On the other hand, it also generates a small amount of H2O2 in situ on the cathode, which slows down H2O2 consumption. Furthermore, the Pt anode oxidises water to generate a small amount of ·OH. These combined effects promote ·OH generation. Additionally, the total ·OH concentration achieved in this work was 48.69% greater than that produced by the Fenton reaction. This indicates that applying the Electro-Fenton reaction to CMP of SiC improves the polishing effect.