Recent developments in precision optical coatings prepared by cylindrical magnetron sputtering

Abstract

Cylindrical targets give the opportunity to improve the process stability of magnetron sputtering processes although reactive deposition might be a challenge. Sputtering from metal doped oxide targets in connection with a plasma source unlocks the full potential: the process can be driven in well-known mid-frequency mode and the plasma source ensures fully stoichiometric films with low loss. During the last years different developments for oxide cylindrical targets were done. The suitable composition has to be found regarding e.g. the density and an arc-free process as familiar for planar targets. In the tube geometry new manufacturing methods are required that ensure these properties. In the present paper we show some examples of the high refractive index materials tantalum oxide: single film characterization as well as realized complex precision optical filters. The results are accompanied by performance measurements in terms of uniformity over 200 mm glass wavers as well as carrier to carrier and batch to batch. These were measured by the position of a quarter-wave stack’s edge.