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Etching characteristics in three different modes employing an M = 0 helicon plasma were compared. It was concluded that high selectivity could not be realized in the high source power operation mode in principle. The comparison between the time-modulated discharge mode and the low source power operation mode in the continuous discharge revealed that almost identical etching characteristics could be obtained if, and only if, the imposed source power in the continuous discharge was equal to the net source power in the time-modulated discharge. It was also confirmed that the degree of dissociation of process gases could be controlled by adjusting the source power in a continuous discharge by an M = 0 helicon plasma.

The SiO2 etch characteristics were investigated using a narrow-gap reactive ion etching (RIE) apparatus. The etch rate was decreased and the selectivity to Si was increased when the upper electrode temperature was increased. However, the etch characteristics were independent of the absolute temperatures of the electrodes. This phenomenon can be explained in terms of the difference in the polymer deposition rate on walls that have different temperatures.

When applying high-density plasma to SiO2 etching, the ability to control the degree of dissociation is critical. In this study, two methods for controlling the degree of dissociation were evaluated using M=0 helicon wave plasma. One method was time-modulated discharge and the other adjusting the source power in the conventional continuous discharge. It was concluded that almost identical etching characteristics could be obtained, at least in M=0 helicon wave plasma, if and only if the applied source power in the continuous discharge was equal to the net source power in the time-modulated discharge. The probe measurement revealed that the electron temperature did not change with increasing source power; however, the emission spectroscopic study indicated that the high-energy tail of the electron-energy distribution function grew with increasing source power. This is considered to be the cause of the high degree of dissociation.

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The impact of CF4 plasma treatment on the surface roughening of SiC has been investigated for N ion implanted SiC(0001) which is implanted with the energy range from 15 to 120 keV at a dose of 9.2 x 1014/cm2. The N ion implanted sample, which is processed by CF4 plasma, shows small surface roughness of 1.6 nm after annealing at 1700 oC for 10 min, while the sample without CF4 plasma treatment shows the large surface roughness (6.6nm) and micro step structure. XPS measurements reveals that CF4 plasma treatment is effective to dissolved the residual oxide on the surface of SiC which is not removed by BHF acid of SiO2 layer on SiC. It is strongly suggested that the formation of micro step structure with the increase of the surface roughness is promoted by the residual oxide such as SiCOx, on SiC.