Voltage-current characteristics of a high-power pulsed sputtering (HPPS) glow discharge and plasma density estimation

A droplet-free metallic plasma source is promising for enhanced adhesion of films with a smooth coating surface. This paper concerns the study of a highly ionized metallic plasma source using a pulsed Penning discharge designed with a magnetic field oriented parallel to an electric field. Such a plasma is called a high-power pulsed sputtering (HPPS) glow discharge plasma. This technology is related to so-called high-power impulse magnetron sputtering (HIPIMS), though the interaction of the magnetic and electric field in the HPPS glow plasma is different from the HIPIMS plasma. The titanium metallic species are sputtered by energetic argon ion bombardment, causing their ionization in as short as a few microsecond. The typical electrical characteristics are as follows: a peak current of 45 A (0.9 A/cm(2)), a peak power of 18 kW (0.8 kW/cm(2)), and an average power of 1 kW. The target voltage is approximately 400 V at 30 mu s for glow currents of 30-120 A. A negative pulse voltage is applied to the substrate holder electrode to extract ions from the magnetically confined HPPS glow plasma. Using the recovery characteristics of the voltage applied to the substrate, the ion density at the substrate surface is estimated to be on the order of 10(16-17) m(-3) for a singly charged titanium plasma. (C) 2009 Elsevier B.V. All rights reserved.