Thin film micromachined structures for large-area applications

Thin-film cantilever and bridge structures composed of a-Si:H, SiNx, mu c-S i and Al were fabricated on glass using low temperature surface micromachin ing processing for mechanical integrity determination and eletrostatic actu ation. The free standing length of these structures (L-max) is related to t heir thickness (h) with a relationship L-max (bridges) approximate to 100/h and L-max (cantilevers) approximate to 50h. Although these empirical relat ions are in qualitative agreement with the structural properties of the str uctures, the constant as well as the yield for free standing structures is expected to be affected by the processing parameters. Electromechanical act uation of these structures was achieved by applying an electric field betwe en a bottom electrode and a top Al layer of the bridge or cantilever. The c ritical voltage necessary for the structure to bend enough to touch the bot tom 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 fun ction of the applied voltage confirms that dependence. (C) 2000 Elsevier Sc ience B.V. All rights reserved.