Pulsed magnetron sputtering is a highly successful technique for the deposition of transparent dielectric materials. Operating in the mid-frequency range (20-350kHz), the periodic target voltage reversals suppress arcing and stabilise the reactive sputtering process. Asymmetric bipolar pulsed DC power supplies are commonly used to drive this process. For simplicity these supplies are normally assumed to display ‘square wave’ characteristics. However, as pulse frequencies are increased, particularly to in excess of 150kHz, target voltage waveforms increasingly depart from this idealised behaviour. Very significant voltage overshoots are observed in each direction during each half of the pulse cycle.

Concurrent studies are now being carried out to investigate the interrelationships between target voltage waveform, the subsequent plasma characteristics, the flux and energies of ions incident at the substrate and their collective impact on film structure and properties. To ascertain these relationships, metallic and ceramic films have been deposited at various pulse frequencies and duty cycles; time averaged and time resolved Langmuir probe studies have been performed; and ion energy distribution functions have been obtained using an energy-resolved mass spectrometer. The films themselves have been characterised in terms of their structures and properties including hardness, critical load and, in the case of the ceramic films, refractive index. The results to date, presented here, are beginning to shed some light on the complex processes occurring during asymmetric bipolar pulsed sputtering.