Hysteresis through E-H and H-E transitions in Ar-ICP using space- and time-resolved optical emission spectroscopy

Inductively coupled plasma (ICP) has two sustaining modes according to the plasma external condition, such as input power, gas pressure, etc. One is inductive H-mode, where high density plasma is generated by electromagnetic field. The other is capacitive E-mode, where plasma is ignited by static electric field between segments of a current coil. In our previous paper, we studied the static and dynamic optical characteristics during E-H transition. Hysteresis characteristics of the emission intensities of Ar(2p$_{1})$ and Ar(2p$_{9})$ through E-H and H-E transitions in Ar-ICP was studied by using space- and time-resolved optical emission spectroscopy (OES). The 2D-t emission images of Ar(2p$_{1})$ produced by high-energy electrons were quite different from those of Ar(2p$_{9})$ mainly by low-energy electrons. Local non-uniformity of the OES in Ar(2p$_{1})$ was essential during the E-mode. On the other hand, the spatial distributions of both Ar(2p$_{1})$ and Ar(2p$_{9})$ were uniform during H-mode and H-to-E transition. The metastable Ar(1s$_{5})$ with a long lifetime has the effective contribution to keep the H-mode up to a lower coil current region in the H-to-E transition.