Mainz 2022 – scientific programme

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P: Fachverband Plasmaphysik

P 9: Poster I

P 9.35: Poster

Tuesday, March 29, 2022, 16:00–17:30, P

Langmuir probe measurements in a dual-frequency capacitively coupled rf discharge — •Jessica Schleitzer, Thomas Trottenberg, Viktor Schneider, and Holger Kersten — Institute for Experimental and Applied Physics, Christian-Albrechts-University Kiel, Leibnizstr. 19, 24108 Kiel, Germany

The standard frequency for common rf plasmas used in technology is 13.56 MHz. A difference in the area of the electrodes result in a self-bias voltage at the powered electrode. The gas pressure in the device and the dc self-bias mainly determine the sheath potential and, thus, the ion current density and the ion energy towards the electrode surface. An independent control of these important properties - especially in industrial applications - is desirable but usually not possible. By adding a second frequency (27.56 MHz), a so-called electrical asymmetry effect (EAE) is created, which enables the control of the bias voltage and, thus, the ion energy almost independent of the ion flux by varying the phase angle between the two harmonics. Since the EAE is a relatively new approach to separately control these two parameters, the number of diagnostics performed in such a discharge amounts to a minimum. By using a specially designed Langmuir probe in this dual-frequency plasma, it can be determined to what extend the important plasma parameters, i.e. electron density and electron temperature, change with a variation of the phase between the two harmonics. This work aims to provide an initial insight into the differences between a single- and dual-frequency plasma based on Langmuir probe measurements and offers a comparison of theory and experiment.