Atomic-scale flattening mechanism of 4H-SiC (0001) in plasma assisted polishing

Plasma assisted polishing (PAP), in which the irradiation of atmospheric pressure water vapor plasma and ceria (CeO2) abrasive polishing are combined, is a novel finishing technique for single-crystal silicon carbide (4H-SiC). An atomically flat 4H-SiC surface (rms about 0.2 nm) with a well-ordered step/terrace structure was obtained by PAP. Cross-sectional transmission electron microscopy (TEM) observation revealed that plasma oxidation atomically flattened the interface of SiO2/SiC. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) measurement results showed the existence of a thin silicon oxycarbide layer, which is corrosion-resistant to hydrofluoric acid, at the interface. The combination of water vapor plasma oxidation and the mechanical removal of silicon oxide as well as silicon oxycarbide layers by a soft abrasive is effective in obtaining an atomically flat surface of 4H-SiC (0 0 0 1) without introducing crystallographic subsurface damage. (C) 2013 CIRP.