INVITED: From Target to Substrate - About the Generation of Energetic Ions in HiPIMS Discharges

High power magnetron sputtering (HiPIMS) discharges generate ions with high kinetic energies in comparison to conventional dc magnetron sputtering. The peculiar shape of the ion energy distribution function (IEDF) is correlated to the formation of localized ionization zones (IZ) in the racetrack of a HIPIMS discharge, so called spokes. The plasma undergoes a sequence from stochastic spoke formation, to regular spoke pattern rotating in the ExB direction to a homogeneous plasma torus with increasing plasma power. The dynamic of those spokes is analyzed by fast camera measurements, ion energy mass spectrometry, probe array experiments and conventional plasma spectroscopy. The connection between IZ and IEDFs suggests a local maximum of the electrical potential inside these localized IZ. The consequence of this hypothesis on the material analysis in those discharges is discussed.