FHiVI$^{2}$: A Fast High-Voltage approach for Ionisation Improvement in the context of plasma-assisted magnetron sputtering

Abstract

Ionisation control remains a key challenge in plasma-assisted processes and more particularly in magnetron sputtering. In this context, the former directly governs species transport and thin-film properties. Although HiPIMS substantially enhances the ionisation rate of sputtered species, its performance remains constrained by the coupling between sputtering and ionisation, which limits discharge tunability. Here, we introduce Fast High Voltage for Ionisation Improvement (FHiVI$^{2}$), a new transient electrical regime designed to improve the ionisation rate without requiring additional elements. By applying an ad hoc very short, high-voltage pulse during plasma sputtering processes, FHiVI$^{2}$ regime is expected to induce a strongly anisotropic electric-field burst intended to enhance sputtered metallic species ionisation while limiting back-attraction losses and sputtering. To assess the ionising potential of this regime, optical emission spectroscopy together with mass spectrometry were carried out. More particularly, mass spectrometry measurements show an improvement of the ionisation rate by a factor of 2.7 compared with the HiPIMS regime, for an applied voltage of 2 kV which correspond to an additional mean power of only 1.2 W, using a 2-inch tungsten target. These findings suggest that FHiVI$^{2}$ provides a flexible route towards improved ionisation control in magnetron sputtering and opens new perspectives for plasma-assisted processes.