Investigation of Electrolytic Condition on Abrasive-Free Electrochemical Mechanical Polishing of 4H-SiC Using Ce Thin Film

Abstract

Silicon carbide (SiC) is a promising material for power electronic devices; however, the fabrication of low-cost and high-quality single-crystal SiC wafers with a smooth surface remains difficult, due to its high mechanical hardness and chemical stability. We report an abrasive-free electrochemical mechanical polishing (AF-ECMP) for a SiC surface using Ce film deposited on a polishing pad. The SiC surface is oxidized by electrolysis between the SiC (anode) and the polishing plate (cathode), the resulting oxide is then removed by interaction with the Ce film. The excess oxide produces a rough surface during continuous electrolysis on the SiC surface. The periodic electrolysis improves the surface quality, and electrolysis conditions such as duty ratio, duty cycle, and applied voltage are optimized. The abrasive ECMP, using CeO2 particles, broadens the initial scratches on SiC, whereas no scratch broadening is observed by the AF-ECMP. Despite a lower material removal rate (MRR) than the abrasive ECMP, the surface roughness was improved by the AF-ECMP with less polishing time. AF-ECMP produces an atomically smooth SiC surface with a roughness of ∼0.5 nm Ra, which is promising for low-cost and environment-friendly finishing process for SiC.