Comparisons of the Characteristic on the Mode Transition in an Inductively Coupled Discharge by Exciting Coil Change

The effects on the characteristics of mode transition were investigated in a spiral type inductively coupled discharge with different size antennas, such as different turns, intervals, and heights. In the case of the relatively small intervals, the transition powers, whether the E to H mode or the H to E mode, decrease with the intervals in the two-turn antenna discharge, and the transition powers of three-turn antenna discharge are much smaller than that of two-turn antenna as the heights stay constant. All these results can be attributed to the nonlinear enhancement mechanism of electron heating in the nonlocal kinetic overlapping region. Moreover, the transition powers decrease slowly with the intervals and finally can increase under the circumstance that the dissipated power in the plasma sheath is relatively obvious. Meanwhile, the transition powers seem like keeping at a minimum values in the three-turn antenna discharge with the same intervals. These experimental results can be caused by the increased power loss across the relatively large sheath and Joule heating in the antenna coil, which lead to a decrease in the radio frequency coupling efficiency with the increasing intervals. Therefore, the combined effect of the nonlinear enhancement effect and the thicken sheath is a key factor on the change laws of the mode transition powers in different type antenna discharges. This paper can be significant to industrial production applications and the foundation theory researches on the mode transition in inductively coupled discharges.