Silicon Direct Bonding for the European Space Agency's Next X-ray Observatory

Abstract

Silicon direct bonding is a manufacturing process used in the fabrication of electronic, optical and mechanical microsystems. Chemical bonds are providing an intimate surface contact and strong structural stiffness that is, for this reason, also suitable for large assemblies. Based on the knowledge of the surface properties and of X-ray optics, we are making mirror imaging systems. The manufacturing process resorts to the highest-grade 12 inch silicon wafers with double-sided super polished and nearly perfect plan parallel surfaces. With readily available semiconductor manufacturing and lithographic tools, the wafers are processed into mirror plates with micrometer accuracy channel structures, yet maintaining the nanometer accurate figure of the silicon wafer. Multiple channeled X-ray mirrors shall subsequently be curved and stacked to form an optical component. We want to use such optical components for a ~3 m diameter segmented optical system that would be part of the Athena observatory.