Investigation of residual stresses in microsystems using X-ray diffraction

Due to the individual steps of manufacturing, various kinds of residual stresses and strains are induced in devices and components of microsystems. These residual stress states often differ considerably from those determined in well-known conventional materials and material compounds. This is caused by the small dimensions of the single components and by the great variety of material combinations used. X-Ray diffraction is a powerful tool also for the investigation of the residual stress states in microsystems, because it enables the non-destructive testing of materials and components, and the investigation of very small measurement volumes. Due to the small thickness of the individual layers in multi-layered microsystems, the X-rays penetrate in many cases deeply into the samples, and diffraction patterns occur in layers of different materials. Using new X-ray optics like fibres and mirrors, the size of the spots to be measured can be reduced to very small lateral dimensions without unacceptable loss of intensity. As a result of this miniaturisation, the material within the volume to be measured differs more and more from the polycrystalline state. In this situation, new detection systems like area detectors can be used successfully. New evaluation procedures are required.