Using pulsed direct current power for reactive sputtering of Al2O3

Abstract

Application of steady direct current (DC) power to the reactive sputtering of dielectrics such as Al2O3 is seriously hampered by arcing. This arcing can be alleviated to a great extent when pulsed dc power is applied. By pulsed dc power we mean that the power is applied for a short “on” period, and then removed for a short “off” period. During the “off” period the plasma can discharge the surfaces, provided certain conditions are met. The dependence of adequate discharging, and thus arc prevention, on the duration of the “on” and “off” periods is examined. In addition, the dynamics of plasma density loss in the “off” period and its reestablishment in the initial part of the “on” period are discussed. Reactive sputtering takes place only during the “on” period, and part of this period is lost for effective sputtering due to the time required for full plasma reestablishment. This produces a dependence of the deposition rate on both the duty cycle and the frequency of pulsing, but not on the power consumed. This dependence is examined and the power efficiencies of alternating current and pulsed power dc reactive sputtering are compared and the differences between single and dual cathode systems in published results is discussed.