Amorphous silicon air-gap resonators on large-area substrates

Air-gap resonators composed of bridges of hydrogenated amorphous silicon and aluminum bilayers on glass and polyethylene terephthalate substrates are realized using surface micromachining techniques. The resonance frequency of structures on plastic substrates was found to vary inversely with the square of the length of the bridge span. On glass substrates, this dependence is seen for lengths > 100 mu m, while for lengths < 100 mu m, a decrease in the frequency is attributed to compressive stress. Resonance frequencies of similar to 500 kHz to similar to 2 MHz were measured in bridges with lengths from 160 mu m down to similar to 80 mu m. (C) 2000 American Institute of Physics. [S0003-6951(00)03732-3].