The effect of discharge chamber geometry on the ignition of low-pressure rf capacitive discharges

Abstract

This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder ͑"symmetric parallel plate"͒, parallel plates surrounded by a grounded metallic cylinder ͑"asymmetric parallel plate"͒, and parallel plates inside a much larger grounded metallic chamber ͑"large chamber"͒. The breakdown curves for the symmetric chamber have a multivalued section at low pressure. For the asymmetric chamber the breakdown curves are shifted to lower pressures and rf voltages, but the multivalued feature is still present. At higher pressures the breakdown voltages are much lower than for the symmetric geometry. For the large chamber geometry the multivalued behavior is not observed. The breakdown curves were also calculated using a numerical model based on fluid equations, giving results that are in satisfactory agreement with the measurements.

Modes of rf capacitive discharge in low-pressure sulfur hexafluoride

“…In the strong-current γ -mode the electron avalanches developing within the nearelectrode sheaths dominate as a source of charged particles. At the same time, however, the breakdown of near-electrode sheaths may not occur [26].…”

Electron drift velocity in N2O in strong electric fields determined from rf breakdown curves

“…It should be remarked that these features (a multi-valued section, Paschen and multipactor branches at low gas pressure) are only observed in symmetric rf discharges [28], i.e. the planar electrodes must be situated inside a dielectric tube with an inner diameter close to the outer diameter of the electrodes.…”

“…the planar electrodes must be situated inside a dielectric tube with an inner diameter close to the outer diameter of the electrodes. If the electrodes are located inside a grounded chamber of larger dimensions and their radial boundary is not limited with a dielectric tube then the rf breakdown curve will not possess these features [28,29].…”

Similarity law for rf breakdown

“…-Recently a considerable number of papers were devoted to gas breakdown in rf electric field (see [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]). It is associated with a broad application of rf discharge in plasma technology processes as well as with an opportunity to determine the electron drift velocity in a strong rf electric field (see [13,16] and the references cited therein).…”