Comparative study of high-power pulsed sputtering (HPPS) glow plasma techniques using Penning discharge and hollow-cathode discharge

Plasma-ion processing enhances the functionality of films used in various industrial and life-science fields, where high-efficiency metal-plasma sources are indispensable for facilitating this process. In this paper, a new sputtering plasma source is proposed. The plasma source is called high-power pulsed sputtering (HPPS) plasma; more than 10 kW of electric power is easily consumed in the plasma despite its compact size. The characteristics are compared with those of a hollow-cathode discharge (HCD) in the same source configuration. In the case of HPPS plasma generated in a magnetic field, the plasma is confined in the magnetic field and as much as 8 kW of power is consumed. When a set of permanent magnets are removed, the plasma changes from a confined state to an expanded state. Thus, a hollow-cathode discharge plasma is generated. As a result, efficient sputtering of the target material ceases; the consumed power decreases to approximately 20% of that of HPPS plasma, which causes the power density to decrease to 5%. The metallic components observed in the optical emission spectrum are significantly less common in the HCD plasma. In the HPPS plasma, the contributions to the optical emission spectrum from titanium- and argon-related species are significant, while no specified emissions are detected in the HCD plasma. Based on the optical emission spectrum intensity, the activated titanium species are not uniformly distributed at the gap. Some parts of the species are commonly on the outer edge of the target, while the argon species are relatively uniformly distributed in the plasma region.