Parameter Optimization in Pulsed DC Reactive Sputter Deposition of Aluminum Oxide

Pulsed dc power supplies provide enabling capability to dielectric reactive sputtering applications due to their ability to reduce or even eliminate arcing during the deposition process. As this technology matures there has been increasing interest in the semiconductor, optical and industrial coating industries to use pulsed-dc sputter supplies for difficult to deposit films. The fundamental behavior of reverse-voltage pulsing and its ability to reduce arcing has been studied [1,2] but little work has been published on optimizing the available parameters to provide maximum rate, minimum arc activity and maximized process stability and system utilization. Previous studies have shown that in the range of 20 to 100 kHz there is a strong relationship between arc activity and reverse pulse time. In one study a critical duty factor was identified at a pulsing frequency of 60 kHz where arc free operation was obtained over an extended operating period [1]. This paper intends to expand upon these findings to explore whether an optimum duty factor may be established throughout the available frequency spectrum of today’s generation pulsed-dc power supplies. Furthermore, little is understood of how arc intensity, i.e. energy released during the arc, can affect process stability and longevity. Recent technological advances in pulsed-dc power supplies have allowed the range of pulsing frequencies to extend beyond 300 kHz and system architecture now allows for arc intensity discrimination. This study capitalizes on these capabilities as well as the more traditional controls of reverse time (duty factor) and reverse voltage in an effort to characterize their relationship to arc density, and long term process reliability during the reactive deposition of dielectric Al 2 O 3 .