Enhancing ionization and excitation efficiency in HiPIMS plasmas through tailored pulse energy inputs

The objective of the present study is to assess the potential of a new HiPIMS operating regime, called enhanced- high power impulse magnetron sputtering (HiPIMS) (a.k.a. e-HiPIMS). This regime consists of additional voltage pulses superimposed on the main pulse at different times during the discharge to reshape the temporal energy distribution input into the plasma and favor selected excitation and ionization processes. The benefit of such regime is shown by the study of the titanium sputtering using optical emission spectroscopy measurements. First, the decrease observed in Ar lines evidences the lowering effect on the electron temperature T e induced by titanium sputtering processes and more precisely by the titanium itself. Second, the different e-HiPIMS configurations demonstrate the possibility of enhancing certain excitation and ionization reactions over others leading for instance to an increase in Ti + /Ti (368 nm/365 nm lines) signal ratio by a factor of 7 at the maximum compared to a conventional HiPIMS configuration. Such an approach could therefore be beneficial both from a physical standpoint (target consumption, equipment ageing) and from an environmental perspective.