Characterization of 4H-SiC (0001) surface processed by plasma-assisted polishing

Abstract

For the finishing of some difficult-to-machine materials, such as silicon carbide, diamond, and so on, a novel polishing technique named plasma-assisted polishing (PAP) was proposed, which combined with the irradiation of atmospheric pressure water vapor plasma and polishing using soft abrasives. In this article, application of PAP to 4H-SiC (0001) substrate was conducted. We used helium-based water vapor plasma to modify the mechanical and chemical properties of the SiC surface. The results of X-ray photoelectron spectroscopy measurements indicate that the surface was efficiently oxidized after plasma irradiation, and the main product was SiO2. CeO2 was used as the abrasive material in PAP, the hardness of which was near to that of the oxidized surface. The scanning white light interferometer images of the PAP processed surface showed us that scratches disappeared and surface roughness also decreased from 4.410 nm p-v, 0.621 nm root mean square (rms) to 1.889 nm p-v, 0.280 nm rms. From the atomic force microscopy images, step and terrace structure was observed on the surface after PAP, which means an atomically flat surface was obtained. The PAP processed surface was observed using cross-sectional transmission electron microscope, which indicated that almost no crystallographical defects were introduced.