Coating stress compensation and temporal evolution studies for ion beam sputtered thin films

Ion beam sputtering (IBS) is the state-of-the-art coating technique to produce highest quality optical filters and laser optics. In both fields the requirements regarding surface flatness have increased through the last decade. Since IBS thin films usually show a high compressive intrinsic stress, a suitable compensation approach as well as the precise determination of the material dependent stress values are essential to fulfill challenging specifications. This contribution compares intrinsic stress results for several coating materials realized with different IBS machines in side sputtering and sputter up configuration. Furthermore, a stress compensation approach is discussed on a concrete example including the influence of the substrate material. As a major topic the temporal evolution of the coating stress is investigated. Finally, we present a post coating process step to reduce the surface irregularity around the substrate rim induced by the fixturing.