Generation of droplet-free high-power pulsed sputtering (HPPS) glow plasma with several tens of kilowatts



A droplet free metallic plasma source is promising for enhanced adhesion of films with a smooth coating surface. This paper concerns a highly ionized metallic plasma source using a pulsed Penning discharge. A high-power pulsed sputtering (HPPS) glow discharge plasma is generated using electric- and magnetic-field interactions. The metallic species are sputtered by the energetic argon ion bombardment, followed by their ionization in as short as approximately 3 μs. The plasma source is compact in size (approximately 60 × 60 × 60 mm3) and the plasma is arc-free. The glow plasma is generated at a gap with a length of 10 mm. The magnetic field at the gap is approximately 0.3 T. A pulsed power source with a rectangular-shaped voltage-output is used. Fundamental electrical and optical characteristics are obtained. The glow voltage and current are approximately –0.43 kV and 37 A at 30 μs, respectively, which corresponds to a peak power of approximately 16 kW, where the applied voltage –1.2 kV and a current limiting series resistance is 20 Ω. The consumed energy is approximately 0.41 J, which corresponds to an average power of 250 W at a repetition rate of 625 Hz. The power and energy are changed by circuit conditions. In order to increase the consumed power, the current limiting-resistance is decreased to be 3 Ω, the peak power is increased to approximately 70 kW with a power density of 2.9 kW/cm2, where a current density is 4.5 A/cm2. The ambient gas is argon at a pressure of 2 Pa. In the emission spectra, singly- and doubly-ionized titanium ions are observed, following the generation of argon ions, which shows the ionization of sputtered titanium species. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)