Highly ionized fluxes of sputtered titanium atoms in high-power pulsed magnetron discharges

High-power pulsed dc magnetron discharges for ionized sputtering of titanium films were investigated. The depositions were performed using a strongly unbalanced magnetron source with a planar titanium target of 100 mm diameter. The repetition frequencies were 1 and 20 kHz at 20% and 50% duty cycles and argon pressures of 0.5 and 5 Pa. Time evolutions of the discharge characteristics were measured at a target power density in a pulse up to 740 W cm-2. Time-averaged mass spectroscopy was carried out at substrate positions of 100 and 200 mm from the target. It was shown that argon ions are predominant (69-81%) in total ion fluxes onto the substrate. The Ti+ and Ar+ ion energy distributions with broadened low-energy peaks are extended to higher energies (50 eV relative to the ground potential). The ionized fraction of sputtered titanium atoms in the flux onto the substrate was in the range from 60% to 99%.