Study of a HPPMS discharge in Ar/O2 mixture: I. Discharge characteristics with Ru cathode

High power pulsed magnetron sputtering discharges have been actively studied during the last ten years in order to achieve high ionization fraction of sputtered species. These sputtering discharges begin to be well understood in non-reactive mode. However, very few works have been devoted to studying reactive conditions. We report results obtained for these discharges working in an Ar/O2 mixture, with a preionization system to accelerate the current pulse rising. A Ru target was used for deposition of RuO2 conductive oxide. This paper discusses the role played by the presence of oxygen on both the preionization phase and the high current discharge characteristics. A comparison is made of results obtained in an Ar/O2 mixture with those obtained in pure argon. Emphasis is laid on the influence of the O2 flow rate and of the total Ar/O2 mixture pressure. It is observed that the O2 content in the inlet gas mixture strongly affects the preionization phase by the electron attachment to O2 as well as the high current discharge development.