The evolution of the plasma potential in a HiPIMS discharge and its relationship to deposition rate

An electron-emitting probe has been used to measure the temporal evolution of the plasma potential Vp along a line from target (Ti) to substrate above the racetrack in a high-power impulse magnetron sputtering discharge pulsed at 100 Hz. The 20 ns time-resolution of the probe allowed us to observe the highly dynamic nature of Vp as the discharge voltage waveform develops, with large negative Vp values (−210 V) and strong potential gradients existing in the magnetic trap region in the first 6 to 8 µs. After 55 to 60 µs, Vp is elevated towards ground potential (0 V) and the bulk electric field collapses. Outside the magnetic trap, i.e. on the open field lines, Vp reveals much smaller axial and temporal variations, similar to those observed in conventional pulsed dc magnetrons.