Effect of Ferric Nitrate on Semi-Insulating 4H-SiC (0001) Chemical Mechanical Polishing

Semi-insulating 4H-SiC (0001) has high hardness and high chemical inertness, making it difficult to obtain high material removal rates (MRR) during chemical mechanical polishing (CMP). In this paper, the role of chemical additive ferric nitrate in semi-insulating 4H-SiC(0001) chemical mechanical polishing with alpha-alumina as abrasive and KMnO4 as oxidant was discussed. The results showed that 0.5 wt% ferric nitrate can increase the removal rate of semi-insulating 4H-SiC(0001) by 34%, while the semi-insulating 4H-SiC(0001) surface roughness Ra was reduced from 0.123 nm to 0.110 nm. The key point was that the coefficient of friction of the polishing slurry was effectively reduced, which was very beneficial to the ploughing effect of the alpha-alumina abrasive with vermicular thin section morphology which had the highest removal rate. In the second place, the chemical composition of 4H-SiC(0001) corrosion layer was analyzed by XPS under different corrosion conditions. Si 2P spectrum analysis showed that O atoms only attack C atoms to produce Si-C-O structure under acidic conditions. Whereas with the addition of ferric nitrate, O atoms not only attacked C atoms, but also attacked Si atoms to produce softer SiO2 and Si-O-x-C-y structures. At the end of the paper, the chemical mechanical polishing mechanism of semi-insulating 4H-SiC(0001) was given.

Automated summary

The role of ferric nitrate as a chemical additive in the chemical mechanical polishing of semi-insulating 4H-SiC(0001) was investigated in this study. The results showed that ferric nitrate could significantly increase the removal rate of 4H-SiC(0001) while reducing the surface roughness. XPS analysis also revealed the chemical composition of the corrosion layer on 4H-SiC(0001) under different conditions.