High performance silver coating with PACA2M magnetron sputtering

Abstract

The performances that are required today for optical components are increasingly demanding, both in terms of the spectral response and the conditions to which the components are subjected. So-called dense deposition techniques for thin film coating currently make it possible to respond in many cases to this ever-increasing requirement. Indeed, conventional evaporation techniques that can address a large number of applications such as metallic coatings, antireflection coatings, mirrors, are no longer sufficient and we currently rely on the dense deposition techniques such as, for instance, magnetron sputtering which allow implementing layers stable and low-ageing behavior. In this paper, we will review the recent achievements at CILAS by magnetron sputtering technique on high-performance silver coatings for space applications. In our premises in Aubagne, CILAS has implemented a large dimension in-line magnetron sputtering coating machine with which such silver coatings are realized. This equipment with oversized dimensions involving a 6 meters by 3 meters vacuum chamber, 12 turbomolecular pumps and 7 planar magnetrons over 2.50m long will be presented in detail. In particular, the wide range of configurations will also be illustrated with complex coatings achievements with respect to the capability of the machine which is equipped with magnetrons, that may be powered in Radio Frequency, Mid Frequency, Direct Current or pulsed Direct Current modes. For several years, CILAS has improved its coating processes to produce high quality silver coatings, taking into account spectral performances, environmental conditions and also coating uniformity over 2meter by 2 meter dimensions. Further developments have been led by CILAS with the support of the French Space Agency as part of Research and Development activities to improve environmental performance; we present here characterization results on samples before and after environmental qualification (temperature, humidity, vacuum heat ...) and on components with dimensions up to 600mm. A multi-year test campaign including stress measurements and adhesion tests on samples and mirror demonstrator will also be presented.