Passive and fixed alignment of devices using flexible silicon elements formed by selective etching

Assembly systems consisting of aligning pits combined with flexible holding elements have been produced for both passive and fixed alignment of devices such as chips and optical fibres. The free-standing holding elements were fabricated in bulk silicon using the photovoltaic electrochemical etch-stop technique. The pits were oriented along the [100] direction which resulted in square etch profiles and in underetching of the passivated silicon surface layer. The devices were inserted into the pits and positioned towards aligning corners and edges by specially designed tongues. The chips could be positioned with high precision on the wafer, in contrast to the fibres, due to uneven bottom surfaces of the grooves. Hence, the alignment method presented here is more suitable for chip positioning since the lateral position of the chips does not depend on the pit depth. The presented assembly systems are well suited for building hybrid microsystems, where different types of device are assembled onto a micromachined silicon substrate.