Control of structure and properties of coatings deposited by pulsed magnetron sputtering

The structure and properties of magnetron sputtered films depend on the homologous temperature; the ion/atom arrival ratio, and the energy of the bombarding ions. Pulsing the target voltage can strongly influence these parameters and can increase the energy flux delivered to the substrate. The energies of the bombarding ions, and, hence, coating structure and properties are influenced by both the reverse time/duty factor and the pulse frequency. The increasing flux of higher energy ions at increasing pulse frequency causes structure, surface topography and properties to improve up to a certain frequency, and then to deteriorate with further increase. With mid-frequency pulsed substrate bias, the substrate current does not saturate, but increases with increasing bias voltage, and this effect becomes more marked as pulse frequency is increased. Pulsing the substrate bias voltage can thus control the substrate ion current. This has implications for film growth, sputter cleaning, and substrate preheating processes.