Improvement of Removal Rate in Abrasive-Free Planarization of 4H-SiC Substrates Using Catalytic Platinum and Hydrofluoric Acid

We used catalyst-referred etching, which is an abrasive-free planarization method, to produce an extremely smooth surface on a 4H-SiC substrate. However, the removal rate was lower than that obtained by chemical mechanical polishing, which is the planarization method generally used for SiC substrates. To improve the removal rate, we investigated its dependence on rotational velocity and processing pressure. We found that the removal rate increases in proportion to both rotational velocity and processing pressure. A lapped 4H-SiC substrate was planarized under conditions that achieved the highest removal rate of approximately 500 nm/h. A smooth surface with a root-mean square roughness of less than 0.1 nm was fabricated within 15 min. Because the surface, which was processed under conditions of high rotational velocity and high processing pressure, consisted of a step–terrace structure, it was well ordered up to the topmost surface.