Pulsed DC Power for Magnetron Sputtering: Strategies for Maximizing Quality and Flexibility

Abstract

Pulsed DC power is widely used for reactive magnetron sputtering, particularly for dielectric compounds. Its introduction was transformational, enabling reactive sputtering of dielectrics that were essentially impossible with straight DC. This was accomplished by periodically discharging the voltage on dielectric films reactively deposited on the target, actually preventing the occurrence of arcs. The concept of voltage reversal to prevent target arcs during reactive sputtering has been known since at least the 1970s, when it was presented in a patent application. Further development showed that a pulsed implementation could be industrially practical. Asymmetric pulsing was a key concept, with a reversal large enough to discharge the target surface, but small enough to prevent sputtering of the chamber surfaces and anodes. An important aspect of this development was the use of voltage reversal as an effective way to handle the few arcs that did occur, since it rapidly removed the energy stored in the cable system, independent of its length. Now, with continuously increasing demands for diverse films deposited at high quality with minimum defects, increased control and synchronization of multiple pulsed supplies is required. This paper covers strategies for delivering higher power and more control to meet current and future requirements.