Mechanical characterisation of micro-resonator structures

Micromechanical resonators have been designed and fabricated using BESOI substrates with different silicon thickness (5 and 15 microns) and 2/spl mu/m buried oxide. Structures have been designed to be used as gas sensors in combination with the use of an active layer (like a polymer) deposited on top of them. Electro-thermal principle had been used for the structure actuation and four piezoresistances, in a Wheatstone bridge configuration, are used to detect the deflection of the structure. Resonator structures are designed as a square mass suspended by three beams. Bridges and cantilevers have been designed and fabricated with different dimensions. One heating element is placed on each external beam and the Wheatstone bridge on the central one. This layout ensures a good thermal isolation of the Wheatstone bridge from the heaters. In this work the influence of the silicon thickness and the structure geometry on the output voltage amplitude of the Wheastone bridge are analyzed.