Chemical–Mechanical Polishing of 4H-SiC Using Multi-Catalyst Synergistic Activation of Potassium Peroxymonosulfate

This study optimized the proportions of synergistic catalysts to efficiently activate potassium peroxymonosulfate (Oxone), generate more reactive oxygen species, and accelerate the chemical oxidation of silicon carbide (4H-SiC) wafers during chemical–mechanical polishing (CMP) for an improved material removal rate (MRR) and surface quality. The Oxone was activated using ultraviolet (UV) catalysis with a photocatalyst (TiO2) and transition metal (Fe3O4) to enhance the oxidation capacity of the polishing slurry through the production of strong oxidizing sulfate radicals (SO4·−). First, the effects of the TiO2, Fe3O4, and Oxone concentrations on the MRR were studied by conducting multiple single-factor experiments. Next, 4H-SiC wafers were polished using different catalyst combinations to verify the synergistic activation of Oxone by multiple catalysts. Finally, the roughnesses, physical features, and elemental compositions of the wafer surfaces were observed before and after polishing. The results showed that CMP with a TiO2 concentration of 0.15 wt%, Fe3O4 concentration of 0.75 wt%, and Oxone concentration of 48 mM decreased the wafer surface roughness from Sa 134 to 8.251 nm and achieved a maximum MRR of 2360 nm/h, which is significantly higher than that associated with traditional CMP methods. The surface of a 4H-SiC wafer polished using CMP with the optimal catalytic system was extremely smooth with no scratches and exhibited many oxides that reduced its hardness. In summary, the proposed UV-TiO2-Fe3O4-Oxone composite catalytic system for 4H-SiC CMP exhibited significant synergistic enhancements and demonstrated excellent surface quality, indicating considerable potential for the polishing of hard materials.