Nitriding characteristics of 4H-SiC irradiated with remote nitrogen plasmas

Abstract

We examined the atomic concentrations and the weight densities of SiC surfaces irradiated with remote nitrogen plasmas. The unique approach of this work is that we compared the SiC surface irradiated with atomic nitrogen with that irradiated with a mixture of atomic nitrogen and molecular nitrogen in the metastable A 3 Σ + u state. As a result, it was found that molecular nitrogen in the A 3 Σ + u state has a higher efficiency than atomic nitrogen in the nitriding of SiC surfaces. The weight density measurements have revealed the removal of Si and C from the SiC surface by the irradiation of remote nitrogen plasma. These results suggest that the formation of volatile molecules is less significant when the SiC surface is irradiated with 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 .…”

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

“…In a previous work, we examined the atomic concentrations of SiC surfaces remotely irradiated with nitrogen plasmas. 25) We observed the formation of a nitride layer with a thickness of 1-3 nm. In addition, the thickness of the nitride layer was greater when molecular nitrogen in the metastable A 3 AE þ u state was supplied from the plasma.…”

“…1. The apparatus used in the present experiment was basically the same as that used in our previous work 25) except for the following two points. One was the use of p-BN as the discharge tube, instead of quartz in the previous work.…”

“…The other experimental apparatus and procedures were the same as those in our previous work. 25) A microwave power of 2.45 GHz was applied to a microwave resonator attached on the outside of the p-BN tube. The microwave power was 100 W. The distances (Z ) between the microwave resonator and the sample were 7 and 12 cm.…”