Discharge Properties of High-Power Pulsed Unbalanced Magnetron Sputtering

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.