Kiel 2011 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 1: Niedertemperaturplasmen / Grundlagen

P 1.1: Fachvortrag

Montag, 28. März 2011, 16:30–16:55, HS H

Secondary electrons in dual-frequency capacitive radio frequency discharges — •Julian Schulze^1,2, 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, <E_i>, and the ion flux, Γ_i, at the electrodes: (i) Classical discharges operated at substantially different frequencies, where the low and high frequency voltage amplitudes, φ_lf and φ_hf, are used to control <E_i> and Γ_i, 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 Γ_i, whereas θ is used to control <E_i>. 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 <E_i> on Γ_i for different secondary yields, γ. A dramatic effect of tuning φ_lf 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 φ_lf 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.