Development of electrical enhanced photocatalysis polishing slurry for silicon carbide wafer

摘要

Single-crystal silicon carbide, as one of the most promising next-generation semiconductor materials, should be polished with atomically smooth and damage-free surface to meet the requirements of semiconductor applications. The research presented in this paper aims to develop an electrical enhanced photocatalysis polishing method for atomic smoothing of Si-face (0001) 4H-SiC wafer based on the powerful oxidability of UV photo-excited hydroxyl radical on nano semiconductor particles. The research identifies the influences of photocatalyst, electron capturer, UV light, voltage and pH value by designing the orthogonal fading experiments of methyl orange and thus develops several slurries for electrical enhanced photocatalysis polishing accordingly. It also demonstrates that photocatalyst, UV light, electron capturer, and acid environment being necessaries for the electrical enhanced photocatalysis polishing process. Electricity can effectively prevent the recombination of electrons and holes generated on the surface of semiconductor particles and therefore enhance the polishing efficiency. Five photocatalysts including 5 nm TiO2, P25, ZnO, CeO2 and ZrO2 have envious selectivity to the UV light. The slurry with P25 as the photocatalyst and H2O2 as electron capturer presents best polishing performance among, which provides a material removal rate of about 1.18 mu m/h and a surface roughness of about Ra 0.0527 nm in an area of 1.0 x 1.0 mu m. Furthermore, it also discusses how the UV light irradiation and electricity promotes the chemical oxidation of hydroxyl radical with SiC by forming "Si-C-O", "Si-O" and "C-O" on SiC surface. The paper concludes that the proposed electrical enhanced photocatalysis polishing is an effective and clean manufacturing method for SiC wafer without rendering toxic chemical effect on environment and human health.