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P: Fachverband Plasmaphysik

P 9: Poster: Niedertemperaturplasmen

P 9.10: Poster

Dienstag, 31. März 2009, 17:30–19:30, Foyer des IfP

The Electrical Asymmetry Effect in capacitively coupled RF discharges - Analytical model and fluid simulation — U Czarnetzki¹, B G Heil¹, T Mussenbrock², R P Brinkmann², J Schulze¹, and •E Schüngel¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Institute for Theoretical Electrical Engineering, Ruhr-University Bochum

Control of the ion energy at the substrate surface is essential for many applications of capacitively coupled RF discharges. Here we propose a completely novel method to control the ion energy via the Electrical Asymmetry Effect (EAE). The EAE is investigated by an analytical model and a fluid dynamic simulation. In contrast to conventional dual-frequency discharges operated at substantially different frequencies, the discharge is driven by a fundamental and its second harmonic with variable phase between the voltage waveforms. The analytical model shows that the symmetry of the discharge is changed electrically by adjusting the phase and that - even in a geometrically symmetric discharge - a DC self-bias is generated, which depends almost linearly on the phase angle. The ion energy at the electrodes can, therefore, be controlled by adjusting the phase. Ion energy distribution functions are calculated explicitly by a fluid/Monte-Carlo simulation at different phase angles at both electrodes. Both, the analytical model and the fluid simulation show, that the EAE is self-amplifying at low pressures due to flux continuity in the sheath. This work is funded by the DFG through GRK 1051. A method for controlling the ion energy based upon this effect is patent pending.