Carbon Ion Production Using a High-Power Impulse Magnetron Sputtering Glow Plasma

Abstract

The ionization rate of sputtered carbon species in magnetron sputtering glow plasmas is low because of a low sputtering yield, a high ionization energy and a low reaction rate between the carbon and electron in the plasma. In this paper, efficient ionization of sputtered carbon species is realized in high-power impulse magnetron sputtering (HiPIMS) glow plasma. The arrangement of the permanent magnet placed at the back of the target can recover the above issues, which enables a power consumption as high as over 100 kW with a pulse duration as short as 5.5 μs at a source voltage as high as 2200 V. The magnet arrangement affects the production zone of the HiPIMS glow plasma on the target; the plasma moves outward to the radial direction of the target with an increased number of the inner magnets. When the plasma has a larger diameter on the target, a glow easily transits to an arc discharge even at a lower voltage compared with the case of the small-diameter plasma production, because the distance between the plasma and the grounded plate becomes short. Both the highest target voltage without an arc transition and the highest glow current are obtained at n=1, the least number of the inner magnet. In this case, a source voltage of 2200 V brings into the highest instantaneous power of about 144 kW. It is confirmed that higher the source voltage, higher the intensity of the optical emission spectrometry spectrum of carbon ions is. The high power consumption contributes to the high-density argon plasma production. Hence, the least number of the inner magnet results in a higher acceleration energy to bombard the target to efficiently sputter carbon species and a high ion flux bombarding to the target. The longer pulse duration such as 30 μs results in an arc transition at the source voltage as low as 1200 V. Thus, the highest emission intensity of the carbon optical emission obtained for n=1 at 2200 V with 5.5- μs pulse duration. It is observed that the intensities of the optical emission from argon and carbon ions are proportional to the power consumed in the plasma.