a b s t r a c tElectro-chemical mechanical polishing (ECMP), which combines anodic oxidation and soft abrasive polishing, was applied to single-crystal SiC. Ceria (CeO 2 ) slurry was used as an electrolyte for anodic oxidation as well as a polishing medium to remove the oxide layer. As a result of anodic oxidation, the surface hardness decreased from 34.5 GPa to 1.9 GPa, which made it possible to polish the oxidized SiC surface using a very soft abrasive such as CeO 2 . It was found that the material removal rate (MRR) of ECMP for a diamond-abrasive-polished surface was 3.62 μm/h. ECMP using CeO 2 slurry was conducted for 30 min on a diamond-abrasive-polished surface. All the scratches were completely removed and a smooth surface with a root mean square (RMS) roughness of 0.23 nm was obtained.

Preliminary study on anodic-oxidation-assisted polishing (AOAP) of 4H-SiC (0001) using ceria polishing film was demonstrated. In the case of using deionized (DI) water as an electrolyte, rms roughness of 0.16 nm was obtained, which is almost the same as roughness of the surface finished by conventional chemical mechanical polishing (CMP). However, the polishing rate was very low and was 23 nm/h. In contrast, the polishing rate of 0.84 μm/h, which is equal to that of conventional CMP of single-crystal SiC or greater, was obtained when we used 1 wt% of phosphoric acid (H3PO4) as the electrolyte, although the surface roughness increased to rms roughness of 1 nm order. These experimental results indicate that the polishing rate greatly depends on the oxidation rate of anodic oxidation and the balance between the oxidation rate and the removal rate of oxide by abrasive greatly affects the roughness of the processed surface.