Polycrystalline β-SiC and single-crystalline 4H-SiC surfaces were etched by reactive ion etching (RIE) using NF3 gas plasma. A smooth surface was obtained on the polycrystalline SiC after RIE at NF3 gas pressures of 2 and 10 Pa for 10 min, and neither spikes nor pillars were formed on it. On the other hand, some pillars were formed on the single-crystalline SiC surface by RIE at NF3 gas pressures of 2 and 10 Pa. Though the absence of carbon-rich regions and SiOx on the outermost surface before etching was confirmed by x-ray photoelectron spectroscopy and Raman analysis, x-ray diffraction analysis revealed that graphite crystallites were present in the single-crystalline SiC bulk. It was concluded that the graphite crystallites acted as masks and the pillars grew up from the graphite crystallites in the single crystalline SiC during RIE.

In pure NF3 plasma, the etching rates of four kinds of single-crystalline SiC wafer etched at NF3 pressure of 2 Pa were the highest and it decreased with an increase in NF3 pressure. On the other hand, they increased with an increase in radio frequency (RF) power and were the highest at RF power of 200 W. A smooth surface was obtained on the single-crystalline 4H-SiC after reactive ion etching at NF3/Ar gas pressure of 2 Pa and addition of Ar to NF3 plasma increased the smoothness of SiC surface. Scanning electron microscopy observation revealed that the number of pillars decreased with an increase in the Ar-concentration in the NF3/Ar mixture gas. The roughness factor (Ra) values were decreased from 51.5 nm to 25.5 nm for the As-cut SiC, from 0.25 nm to 0.20 nm for the Epi-SiC, from 5.0 nm to 0.7 nm for the Si-face mirror-polished SiC, and from 0.20 nm to 0.16 nm for the C-face mirror-polished SiC by adding 60% Ar to the NF3 gas. Both the Ra values of the Epi- and the C-face mirror-polished wafer surfaces etched using the NF3/Ar (40:60) plasma were similar to that treated with mirror polishing, so-called the Catalyst-Referred Etching (CARE) method, with which the lowest roughness of surface was obtained among the chemical mirror polishing methods. Etching duration for smoothing the single-crystalline SiC surface using its treatment was one third of that with the CARE method.

not Available.