The dynamics of the electron temperature and density in short-pulse HiPIMS discharge

This work studies the change in electron density and temperature in short-pulse high power impulse magnetron sputtering (HiPIMS) discharge. A planar magnetron with a copper target of 100 mm in diameter was used in the experiments. Plasma measurements were made using a Langmuir probe placed 85 mm from the target. The discharge current pulse durations were 8, 15, and 100 μs, with a fixed amplitude of 100 A and an average discharge power of 1 kW. To maintain the average discharge power at a constant level, a decrease in the pulse duration was accompanied by an increase in the frequency. When the discharge current pulses started, the electron temperature exceeded 10 eV and then decreased to a few eV. The main time of plasma existence in short-pulse HiPIMS is the afterglow phase, during which the electron density reaches a maximum of 1.9–3.2 × 10¹² cm⁻³ and the electron temperature is less than 1 eV. Because the duration of the afterglow phase in short-pulse HiPIMS is longer than the duration of the discharge current pulse, the average integral electron temperature is lower than that in DC and middle-frequency magnetron sputtering. The average integral electron temperature in HiPIMS decreases with decreasing pulse duration.