Flexible integration of nonsilicon microstructures on microelectronic circuits

Abstract

A great variety of uses of microsystems opens up when sensors and actuators are supplemented by powerful electronics. In silicon technology, the monolithic integration of micromechanical and microelectronic components into one system is possible in a sequence of process steps, although only very few basic sensor and actuator principles can be put into effect. LIGA technology, with the latitude it offers with regard to lateral geometry at high aspect ratios, and its great variety of materials, allows many different sensor and actuator principles to be put into effect. However, integration with microelectronics circuits so far has been possible only in a hybrid way. The new process described in this paper is characterized by the separation of the molding process from the positioning and bonding processes. First, a microstructured polymer film is produced by hot embossing on an auxiliary substrate. Next this self-supporting polymer film is joined to the prestructured wafer by thermal bonding. In this way it is possible, irrespective of the size of the molding tool and the embossing conditions, to position microstructures on a variety of substrates, e.g. by the pick-and-place technique. Finally, the quality of the joint between substrate and microstructured polymer film is demonstrated by using the film as lost form for galvanoforming metallic microstructures on top of the wafer.