Surface damage of 6H–SiC originating from argon plasma irradiation

Abstract

Damage characteristics of SiC surfaces etched by capacitively coupled radio frequency Ar plasmas at various gas pressures have been studied from the viewpoint of synergy effect of Ar plasma ion and plasma-induced ultraviolet (UV) light irradiations. In the absence of UV light emission at the low gas pressure of 10mTorr, morphology of the etched SiC surface is similar to that of the as-grown surface regardless of an increase in etching time. In contrast, the experimental Si/C ratio at the surface decreases with an increase in etching time, which agrees with the simulation that Si atoms at the surface are preferentially removed by Ar+ ions impinging on the surface. The agreement indicates that the physical etching effect, which originates from the Ar+ impact, contributes to the decrease in the Si/C ratio. In the presence of the UV light emission, the surface morphology at the high gas pressure of 50–100mTorr depends on the etching time. The surface morphology changes as the etching time increases to 200min. The experimental etch depth at the etching time of 200min does not agree with that of the simulation. The experimental etch depth is much higher than the simulated one. The difference connecting with the gas pressures can be related to the factor whether the UV light is emitted from the plasma: the result at the high gas pressure suggests the contribution of the synergy effect caused by the following possible phenomenon: Si–C bonding at the surface is weakened.