Improvement in the planarization of 4H-SiC (0001) achieved by photo-assisted chemical mechanical polishing (P-CMP) using nano TiO₂-based composite abrasive with heterostructure

The planarization of silicon carbide (SiC), crucial for manufacturing power devices resilient to harsh working environments, has garnered significant attention. The utilization of titanium dioxide (TiO₂)-based heterogeneous photocatalysts offers a promising avenue for achieving efficient polishing on SiC surface through photocatalysis-assisted chemical mechanical polishing (P-CMP) in an environmentally friendly manner. In this study, we employed nanodiamonds (NDs) and graphene oxide (GO) to fabricate the composite abrasive TiO₂/NDs/GO. Subsequently, the P-CMP performance of TiO₂/NDs/GO on the Si-face of SiC was systematically investigated. The high-resolution transmission electron microscopy (TEM) revealed the heterostructure between TiO₂ and NDs. Furthermore, P-CMP results indicate that the heterostructure significantly enhances the polishing rate of the composite abrasives on SiC, achieving the highest material removal rate (MRR) of 600 nm/h and reducing the average surface roughness (Sa) to 1.1705 nm. Additionally, due to the lubricating and dispersing effects of GO, the occurrence of NDs aggregation is avoided, preventing scratching on SiC. The measurement of ·OH concentration indicates that the increase in ·OH concentration is the primary factor contributing to the improvement of the MRR. Results from wetting angle and friction coefficient tests reveal that the polishing slurry containing TiO₂/NDs/GO exhibits excellent wettability and provides sufficient frictional force on the SiC surface. X-ray photoelectron spectroscopy (XPS) characterization demonstrates that TiO₂/NDs/GO enhances the oxidation degree of the SiC surface, leading to the formation of a softer oxide layer. Finally, based on experimental and characterization results, a comprehensive analysis of TiO₂/NDs/GO and P-CMP was conducted.