RESONANT SENSORS USING ELASTIC SURFACE-WA VES

Microsensors are the most widely studied microsystems because of the l arge needs for industrial process controls, for safety and environment survey and protection. In this paper, some applications of micromachi ned resonant sensors using elastic waves are presented. The devices ar e based on the frequency variations induced by the quantity to measure . The frequency being the most accurate quantity when it is measured, then sensors using this principle have a high resolution. For each con sidered application domain (gas measurements, detection in liquids, et c.), it is possible to choose the right elastic wave having the most a daptated parameters. All are generated with interdigital transducers m ade with a photolithographic process. Different materials, generally p iezoelectric, are used as propagation substrates (quartz, LiNbO3) or S ilicon coated first with a thin film of piezo-material as ZnO or AlN.