Thin film micromachined structures for large-area applications

Thin-film cantilever and bridge structures composed of a-Si:H, SiN x , μc-Si and Al were fabricated on glass using low temperature surface micromachining processing for mechanical integrity determination and eletrostatic actuation. The free standing length of these structures ( L max ) is related to their thickness ( h ) with a relationship L max (bridges) ≈ 100 h and L max (cantilevers) ≈ 50 h . Although these empirical relations are in qualitative agreement with the structural properties of the structures, the constant as well as the yield for free standing structures is expected to be affected by the processing parameters. Electromechanical actuation of these structures was achieved by applying an electric field between a bottom electrode and a top Al layer of the bridge or cantilever. The critical voltage necessary for the structure to bend enough to touch the bottom electrode is proportional to L −2 where L is the length of the structure. A mechanical model used to predict the bending of the structures as a function of the applied voltage confirms that dependence.