The characteristics of RF plasmas as a function of driving frequency f, 0.1-13.56MHz in nitrogen has been observed by optical emission spectroscopic method. The space- and time-resolved profiles of the net excitation rate of molecules and ions have been deduced from spatiotemporally resolved optical emission profiles of their species, i.e. the second positive and the first negative bands. It is found that ionizations due to the secondary electrons from the electrodes by positive ions play an important part in the maintaining mechanism at low frequency as f < 1.5MHz, while a discharge is maintained by bulk ionizations at high frequency as f > 10MHz. The results also show that a discharge at middle frequency as 1.5 < f < 10MHz, is explained from the point of view of the transition of the mechanism which maintains a discharge. It is also shown that the excitation profiles exhibit double layers near the electrodes in nitrogen at 13.56MHz, 60W and the gas pressure p, p > 67Pa.
窒素RFプラズマの発光分光診断
trieejA121_465_2001.pdf
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