Amorphous silicon air-gap resonators on large-area substrates

Air-gap resonators composed of bridges of hydrogenated amorphous silicon an d aluminum bilayers on glass and polyethylene terephthalate substrates are realized using surface micromachining techniques. The resonance frequency o f structures on plastic substrates was found to vary inversely with the squ are 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 o f similar to 500 kHz to similar to 2 MHz were measured in bridges with leng ths from 160 mu m down to similar to 80 mu m. (C) 2000 American Institute o f Physics. [S0003-6951(00)03732-3].