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High-power pulsed magnetron sputtering (HPPMS or HiPIMS) is an emerging coating technology that produces very dense plasmas and highly ionized sputtering atoms. This paper is focused on discharge properties, unbalanced features and temporal evolution of pulse current of the HPPMS discharge. A hollow cathode was used to suppress the scattering of charges. A coaxial coil surrounding the target was used to control the breakdown voltage and pulse repetition frequency by varying the coil current. A Langmuir probe and an oscilloscope were used to simultaneously measure the floating potential, pulse voltage and pulse current signals. The pulse power density in the discharge reached 10 kW/cm2 with frequencies as high as ~40 Hz and a pulse width about 1~5 ms. The characteristics of the discharge evolution were analyzed using magnetron discharge dynamics.

An experimental study of the effect of applied magnetic field on the properties of the plasma and electrostatic oscillations in an unbalanced magnetron sputtering discharge was carried out. The apparatus consists of a magnetron sputtering target, using the conventional magnetic field configuration, and a coaxial coil around the target for an applied axial magnetic field. The dependencies of plasma parameters on the coil current were studied by two Langmuir probes. The resonance properties of electrostatic oscillations were observed. The results indicate that the applied magnetic field affects the plasma properties for the coil current in a range of 0 A to 8 A. The frequency bandwidth of the electrostatic oscillations in the unbalanced magnetron sputtering plasma is in a range of 0 kHz to 300 kHz. From the spectrum analysis, the eigenfrequency near the target is in a range of 20 kHz to 50 kHz under typical experimental conditions where all the magnetic field, pressure, and power etc are able to have full impact on the spectrum characteristics. The calculated value of the electron temperature as per an ion acoustic standing wave pattern inside the magnetic trap is in good agreement with the experimental result.