Recent Diagnostic Studies of Unipolar and Bipolar HiPIMS Plasmas

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   Using a Langmuir probe LP and laser Thomson scattering LTS, the temporal and spatial evolution of the plasma parameters (densities ne and ni, electron temperatures Te, plasma Vp and floating potentials Vf) have been determined in a magnetron discharge operated in two pulsing regimes, 1) conventional unipolar pulsing and 2) asymmetric bipolar pulsing with a positive “kick” pulse.
   In the former case, LTS and LP methods yield good agreement for the electron properties (ne, ni and Te) during both the main HiPIMS pulse and the long afterglow. In the second case, incorporating the “kick” pulse, LP measurements show a modified behaviour in the plasma, with somewhat raised ne and Te measurements during the voltage “kick” phase together with Vp values rising to values close the applied positive voltage over a period of 10’s of s after the “kick” transition.
   By comparing spatially-resolved LP results from unipolar and bipolar pulsing at the same discharge powers and pressures we see that the presence of the “kick” pulse leads to a re-distribution in ne after termination of the main HiPIMS pulse.
   A discussion of the diagnostic techniques and implications of the results will be given.