Novel photoelectrochemically combined mechanical polishing technology for scratch-free 4H-SiC surface by using CeO2-TiO2 composite photocatalysts and PS/CeO2 core/shell abrasives

Abstract

4H-SiC is a promising next-generation semiconductor. To obtain a scratch-free SiC surface with less/no residual oxide layer at an ideal material removal rate (MRR), a novel photoelectrochemically combined mechanical polishing (PECMP) technique was proposed. Polystyrene (PS)/CeO2 core/shell abrasives and CeO2-TiO2 composite photocatalysts immobilized on a titanium mesh were synthesized and characterized. The results of hydroxyl radical trapping tests present that the strongest photocatalytic activity is achieved by CeO2-TiO2 when UV-light and anodic bias are applied simultaneously (the optimal conditions). SiC-PECMP comparison tests were conducted in water containing 6.5 wt% PS/CeO2 on a home-made polisher, and after polishing, surface morphologies, surface roughness values (Ra) and MRRs were compared. The best polishing results (Ra: 0.738 nm, MRR: 1.109 μm/h) are realized under the optimal conditions. This was further demonstrated by another verification test, and a scratch-free surface (Ra: 0.113 nm) with less residual oxide layer was obtained. The scratch-free surface is attributed to the elastic core/shell abrasives and to the mild photocatalytic reaction. The ideal MRR is ascribed to the enhanced photocatalytic activity of the composite photocatalysts. Therefore, the feasibility of the proposed method is demonstrated, and this technique may be utilized to manufacture other semiconductors.