Anode effects on energetic particle bombardment of the substrate in pulsed magnetron sputtering

Pulsed powering of a magnetron discharge in the medium frequency range (20–200 kilocycle) is the basis for a long-term stable run of reactive deposition processes at high deposition rates. Recent investigations indicated another important feature of pulsed powering, which is increased energetic particle bombardment of the substrate. In this paper causes of the strong substrate bombardment are investigated. Values for the thermal substrate load, ion current density onto a floating substrate, and self-bias voltage are compared for DC and pulsed powering. Systematic investigations in unipolar and bipolar pulsed-mode, for varied pulse parameters of duty cycle and frequency, and for several anode configurations are carried out. Different causes for the energetic substrate bombardment can be distinguished. The experiments show the essential influence of the anode configuration on the plasma density and electron temperature in the substrate region. Results suggest new techniques for influencing energetic substrate bombardment and film properties.