Verification of the Effectiveness of UV-Polishing for 4H-SiC Wafer Using Photocatalyst and Cathilon

Abstract

The polishing of 4H-SiC wafer processed under ultraviolet (UV) irradiation was investigated to verify the phenomena and effectiveness of ultraviolet-ray aided machining (U-RAM). Inductively coupled plasma spectrometry (ICPS) analysis was conducted to quantitatively determine the oxidation/dissolution volume of SiC. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were used to qualitatively analyze the 4H-SiC surfaces. These analyses were used to clarify the compounds that are formed/removed by the decomposition of cathilon dye and water during the polishing of 4H-SiC using TiO2-, cathilon- and TiO2-cathilon (mixed) slurries, all of which contained diamond particles. ICPS measurements indicate that a small amount of Si dissolves in aqueous solutions of cathilon- and TiO2-cathilon. XAS and XPS measurements indicate that SiC composes the bulk of the as-received 4H-SiC, and the surface and thin surface form an interface oxide inside SiC. The chemical-mechanical polishing of 4H-SiC using the TiO2-cathilon slurry forms an oxide, interface oxide, oxynitride and nitride. Diamond particles easily remove these compounds by mechanical scratching. It is possible to attain smaller surface roughness and higher polishing efficiency by combination with chemical reaction of TiO2-cathilon slurry and mechanical action of diamond particles under UV irradiation.