A poly-diagnostic study of bipolar high-power magnetron sputtering: role of electrical parameters

Ion acceleration in a bipolar high-power impulse magnetron sputtering discharge working with Ar gas and using a Ti cathode has been investigated. The multiple discharge diagnostic approaches have been implemented, including the target and substrate current probe measurements, mass spectrometry and laser-induced fluorescence. In particular, the current waveforms were analysed in detail, showing the particularities of the current evolution during the negative (plasma) and positive voltage pulses. It is shown that the substrate current during the positive voltage pulse reveals two peaks, corresponding, as suggested, to two groups of the positive ions repulsed from the cathode by the applied positive potential. These observations correlate well with the mass spectrometry measurements as well as with the two-dimensional ion density mapping performed for several discharge conditions by laser-induced fluorescence imaging technique.