Time-resolved diagnostics of a bipolar HiPIMS discharge

Bipolar high power impulse magnetron sputtering (HiPIMS) with a yttrium target is investigated with the help of time-resolved diagnostics. The bipolar HiPIMS discharge is operated with a negative pulse with a width of 100 μ s, which is immediately followed by a positive pulse (pulse voltage up to +60 V) with a duration of ∼ 310 μ s. The time-resolved floating potential first rises to a large positive voltage of ∼ 55 V at the beginning of the positive pulse (+60 V) and after 30 μ s drops to ∼ 38 V. It indicates the ignition of a reversed discharge. Further evidence of such a reversed discharge is confirmed by time-resolved mass spectrometry and time-resolved optical emission spectroscopy.