Manufacturing of high-precision optical coatings using a novel sputtering system

The deposition of high-precision optical coatings by magnetron sputtering is still a demanding and complex procedure. By using planar targets the inhomogeneous erosion of the target material plays a critical role by means of long-term stability of the process and homogenization by shaping apertures. A novel approach to increase the overall process stability is the use of cylindrical cathodes. These cathodes allow for less arcing due to virtually no redeposition zones and thus for particle optimized processes. Furthermore a much more stable sputter yield distribution can be achieved with respect to long term stability, as the target material is eroded homogeneously. On the other hand optical monitoring is one of the key elements in the manufacturing process of optical precision coatings and must meet quite challenging requirements regarding spectral resolution, noise and measurement time as well as process automation. In the present paper an industry-related sputter concept including a unique monitoring system will be presented. Details on the production procedure of an optical filter, manufactured on the present coating system, will be presented and a characterization regarding optical properties, uniformity and particle contamination will be given.