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P: Fachverband Plasmaphysik
P 8: Niedertemperaturplasmen
P 8.4: Vortrag
Dienstag, 31. März 2009, 14:15–14:30, INP-Staffelgeschoß
Sheath dynamics in capacitively coupled RF plasmas — •Kristian Dittmann1, Konstantin Matyash2, Ralf Schneider2, and Jürgen Meichsner1 — 1University of Greifswald, Institute of Physics, Greifswald, Germany — 2Max-Planck-Insitute for Plasma Physics, EURATOM Association, Greifswald, Germany
The RF sheath dynamics in asymmetric capacitively coupled RF plasmas in oxygen, hydrogen and argon is investigated by means of PROES (Phase Resolved Optical Emission Spectroscopy) and simulated with Particle in Cell code with Monte-Carlo collisions (PIC MCC).
Comparing the experimental and simulations results, it was shown that depending on the plasma processing parameters the observed excitation patterns in the sheath have their origin in the electron heating during the sheath expansion phase, energetic electrons in the sheath collapse phase, secondary electrons emitted from the powered electrode, electric field reversal during sheath collapse and electronic excitation due to heavy particle collisions at the powered electrode.
In oxygen RF plasmas an excitation pattern was found which gives an indication for electric field reversal similar to that in hydrogen plasmas. It appears slightly earlier within the RF cycle and its maximum is located not directly at the powered electrode compared to hydrogen case. The detailed analysis of this phenomenon with PIC-MCC simulations revealed, that the electric field reversal in oxygen RF plasmas is determined by the interaction of the electron flow toward the wall during the sheath collapse phase with the negative ions peak at the sheath entrance. Supported by SFB-Transregio 24.