In-situ stress measurements of sputtered multilayers

The mechanical stress induced during the growth of thin films and multilayers is a critical parameter for the fabrication of reflective x-ray optical elements. Strong stress can cause deformation of the optical surface, de-lamination of the respective coating, or even breaking of the underlying substrate. In order to characterize stress in a growing film or multilayer in a nearly in-situ mode, a dedicated monitor was installed on the ESRF multilayer deposition system. It is based on an autocollimator that measures the curvature change of a sample after subsequent coating steps while keeping it in the vacuum environment. Based on the theory of elasticity, the corresponding stress levels in the coating can be derived. Both the commissioning of the instrument and some initial results on single Ru and B4C films and Ru/B4C multilayers will be presented. A comparison with ex-situ investigations will complement this work.