Ionized sputtering with a pulsed hollow cathode magnetron

A hollow cathode magnetron has been operated with a HiPIMS power supply at duty cycles around 1%, and the non-reactive sputtering of several target materials such as copper, aluminum and carbon has been investigated. Systematically varying pulse length, frequency, discharge voltage, pressure and geometry of the magnetic field, waveforms of discharge voltage and current have been recorded. Beyond a material-specific voltage level, the pulse current always shows a runaway behavior stopped only at current densities above 10 A/cm2 due to the limits of the power supply. Furthermore, the plasma has been characterized by time-averaged and time-resolved optical emission spectroscopy as well as by energy-resolved ion mass spectroscopy. The optical spectra showed the contribution of self-sputtering and the portion of metal ions rising with elapsing time during the pulse. Measurement of ion energy distribution functions of different species mostly revealed a low (below 30 eV) and a high (around 100 eV) energy part. Moreover, the portion of singly and doubly charged target ions is increased with the pulsed discharge current. Deposited layers show a dense, fine-grained structure, indicating a high degree of ionization of the layer-forming particles.