Questions to Consider in the Design of an AC-Sputter System

In the past several years there has been a renewed effort among optical thin film researchers to improve reactive sputtering with either AC or pulsed-DC technology. These related technologies allow one to deposit insulating materials such as SiO2 and Al2O3 in a sputter process that uses metal targets with planar magnetrons. This ability to sputter insulating materials at high rates without arcing represents a breakthrough in technology. Since the invention of the DC magnetron in 1973, arcing has always been one of the limiting factors in reactive sputter deposition. In a 1988 paper, Este and Westwood1 demonstrated an arc reduction technique in which they applied an alternating square wave voltage to a pair of rectangular sputter targets at a frequency in the 100kHz range. Since then a number of researchers have reported on similar arc reduction techniques which allow the deposition of defect free films at DC sputter rates. The results of their work are evident in the number of papers and symposium presentations on AC sputtering and the number of systems currently being set up to sputter oxide coatings reactively. As part of this presentation we will review the current state of the art.