THERMALLY DRIVEN MICROMECHANICAL BRIDGE RESONATORS

This paper reports the fabrication and characterization of bridge resonators made of single-crystal silicon. The fabrication process involves anisotropic etching in combination with an electrochemical etch-stop technique to obtain uniform membranes and RIE etching to free the bridges. These devices are sensitive to axial loads, and a potential application is their use as sensing elements for mechanical sensors. The drive method chosen is thermal excitation in combination with piezoresistive detection. It allows the resonating element to operate in a closed-loop electrical circuit. Several designs varying in bridge shape and resistor position have been fabricated in order to find the best parameters for a future application in a resonant sensor. Both electrical and optical measurements reveal quality factors from 200 to 400 in air. Resonant frequencies up to 1 MHz could be excited electrothermally.