Suppression of carbon desorption from 4H-SiC by irradiating a remote nitrogen plasma at a low temperature

Abstract

We remotely irradiated a nitrogen plasma onto the carbon-side surface of 4H-SiC at a low temperature, and examined the effect of sample cooling on the characteristics of the nitride layer. An improved nitride layer, which had higher concentrations of carbon and silicon and a lower concentration of oxygen, was formed in the region at depths of more than 0.6-0.9 nm from the top surface. The depth of the fragile nitride layer in the top region, where no improved characteristics of the nitride layer were observed, became smaller with sample cooling. In addition, on the basis of the experimental results, we discussed the difference in the activation energy of the nitriding reaction of 4H-SiC supported by atomic nitrogen and molecular nitrogen in the metastable A 3 Σ + u state.

Nitriding of 4H-SiC by irradiation of fourth harmonics of Nd:YAG laser pulses in liquid nitrogen

“…On the other hand, the carbon concentration was lower than 50% in the entire depth region except the top surface, where the carbon concentration is usually enhanced by the contamination. The lower concentration of carbon than silicon was also observed in the surface nitriding of 4H-SiC using a remote nitrogen plasma [11,12], and the mechanism was estimated to be desorption of volatile molecules such as C 2 N 2 . We also observed the nitride layer in the outside of the crater, as shown in Fig.…”

“…A firstprinciple calculation suggests that the nitriding of the SiC surface can be a solution to this problem [10]. In previous works, we examined the surface nitriding of 4H-SiC by the irradiation of a remote nitrogen plasma [11,12]. A nitride layer with a thickness of 5 nm was formed on the surface of 4H-SiC, but this method had a problem of the decrease in the carbon concentration by the formation of volatile molecules such as C 2 N 2 .…”