SMuK 2021 – scientific programme

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P: Fachverband Plasmaphysik

P 1: Low Pressure Plasma Sources I

P 1.5: Talk

Monday, August 30, 2021, 12:15–12:30, H5

Ion energy and collisions in high power impulse magnetron sputtering discharges — •Julian Held, Sascha Thiemann-Monjé, Achim von Keudell, and Volker Schulz-von der Gathen — Experimentalphysik II, Ruhr-Universität Bochum

High power impulse magnetron sputtering (HiPIMS) discharges are important tools for the deposition of thin, hard coatings. In such discharges, the transport of sputtered and then ionized cathode material towards the substrate determines the deposition rate and, therefore, the usefulness of the discharge for application. To understand how this transport is affected by collisions, we measured the velocity distribution function (VDF) of titanium and chromium ions using high-resolution optical emission spectroscopy. The VDF was found to be mostly Maxwellian, with high temperatures of 9 eV and 4.5 eV for titanium and chromium ions, respectively. Such a Maxwellian distribution implies a surprisingly high frequency of heavy particle collisions. Different types of heavy-particle collisions are discussed and Coulomb collisions are identified as the most frequent process. A simple model is created, following the self-relaxation process of the VDF from the initial Thompson distribution, created by the sputtering, towards the observed Maxwellian distribution. This model shows good agreement to the measured distribution, indicating that the high ion energy is caused by a redistribution of energy from the energetic Thompson distribution into the partly thermalized Maxwell-like distribution, observed in the experiment.