The magnetron sputtering has become one of the commonly used techniques for industrial deposition of thin films and coatings due to its simplicity and reliability. At standard magnetron sputtering conditions (argon pressure equal to ~0.5Pa) inert gas particles are often entrapped in the formed films. Inert gas contamination can be eliminated at self-sustained magnetron sputtering process because it is done in the absence of the inert gas atmosphere. The self-sputtering process gives also a unique condition during the transport of sputtered particles to the substrate. It is especially useful for filling high aspect ratio submicron scale structures for microelectronics. So far it has been shown that the self-sputtering process can be sustained in the DC operation mode (DC-SSS). The main disadvantage of DC self-sputtering process is instability related to arc formation possibility. Could magnetron plasma pulsing eliminate this problem?
In this paper results of pulsed-DC magnetron sustained self-sputtering (pulsed DC-SSS) of copper are presented for the first time. The planar magnetron source equipped with a 50 mm in diameter and 6 mm thick copper target has been used in this experiment. The source was powered by the pulsed-DC unit comprised of DC-power supply (based on a 110 kHz resonant converter) and MOSFET power switch. The maximum target power was about 11 kW, which corresponded to target power density of ~550W/cm2.
The magnetron operation was investigated as a function of pulse frequency (20-100 kHz) and pulse duty factor (50-90%) and the discharge extinction pressure level was measured. The plasma emission spectra (400-410nm range) and deposition rates were observed for both DC and pulsed DC sustained self-sputtering processes. The time behavior of voltage and current of the magnetron source during pulsed DC-SSS operation are shown. The results presented in the paper illustrate that a stable pulsed DC-SSS mode process can be obtained at pulsing frequency in the range of 60-90 kHz and duty factor of 80-90%.
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