Time-resolved ion flux and impedance measurements for process characterization in reactive high-power impulse magnetron sputtering

Abstract

A new planar ion flux probe, based on the Sobolewski method for time-resolved plasma characterization in inherently noisy pulsed plasma discharges, has been developed. The probe was evaluated in a high-power impulse magnetron sputtering (HiPIMS) process, which is a promising ionized physical vapor deposition technique based on pulsed plasma discharges used to engineer thin films with improved properties. Both nonreactive (pure Ar) and reactive (Ar/O2) deposition processes were investigated using a Ti sputtering target. It was found that the process exhibited a nearly hysteresis-free and stable transition region at the chosen deposition conditions. Time-resolved measurements of the absolute ion flux impinging on the probe placed at the substrate position, as well as of the probe sheath impedance, were recorded in the metal, transition, and compound modes during the HiPIMS pulse. Gradual changes in the measured ion flux, as well as the impedance, were seen when transiting from the metal mode to the compound (poisoned) mode. It is therefore suggested that this type of robust plasma probe can potentially be used for reactive process control, where the user would like to stably operate in the transition region over long periods of time.