Thin silicon chips with a thickness of 50 m are of light weight and are able to swim on droplets of fluids like for instance water. If the liquid shows a specific wetting behavior with respect to the underlying substrate then droplet and chip can move and self-align. Recent research work was carried out to determine the self-alignment accuracy of 50 m thin silicon dies on plasma programmed surfaces. The self-alignment process sequence for die assembly comprise the following steps: surface programming by CF4 plasma treatment, dispense droplets of water on the metal target areas, pick-up of a 50 m thin chip, move chip tool above the selected target area, let the chip fall down and self-align on the liquid surface on the target area. Within short time the droplet dries off and then the thin die sticks to the substrate. Self-alignment accuracy was measured by infrared microscopy at the position of the alignment marks of top and bottom devices. The paper will report in detai l about sample preparation, selective plasma programming, self-alignment accuracy of thin dies and its dependence of the die size. Furthermore, the chemical composition of the relevant surfaces after CF4 plasma activation were analysed by XPS measurements