Kiel 2011 – wissenschaftliches Programm
P 1.1: Fachvortrag
Montag, 28. März 2011, 16:30–16:55, HS H
Secondary electrons in dual-frequency capacitive radio frequency discharges — •Julian Schulze1,2, Zoltan Donko1, Edmund Schüngel2, and Uwe Czarnetzki2 — 1Research Institute for Solid State Physics and Optics of the Hungarian Academy for Science, Hungary — 2Institute for Plasma and Atomic Physics, Ruhr-University Bochum, Germany
Two fundamentally different types of dual-frequency capacitive RF discharges can be used to realize separate control of the ion mean energy, <Ei>, and the ion flux, Γi, at the electrodes: (i) Classical discharges operated at substantially different frequencies, where the low and high frequency voltage amplitudes, φlf and φhf, are used to control <Ei> and Γi, respectively. (ii) Electrically asymmetric (EA) discharges operated at a fundamental frequency and its second harmonic with adjustable phase shift, θ, between the driving frequencies. In EA discharges the voltage amplitudes are used to control Γi, whereas θ is used to control <Ei>. We study the effect of secondary electrons on the quality of this separate control in both discharge types in argon at different gas pressures by PIC/MCC simulations with focus on the effect of the control parameter for <Ei> on Γi for different secondary yields, γ. A dramatic effect of tuning φlf in classical discharges and essentially no effect of tuning θ in EA discharges is observed. This is caused by a transition from α- to γ-mode induced by changing φlf and not induced by changing θ. Thus, the quality of the separate control of ion energy and flux is generally better in electrically asymmetric compared to classical dual-frequency discharges.