Design and fabrication of a square shape bulk mode MEMS resonators

This paper reports the design, simulation and fabrication of a micromechanical square shape resonators fabricated in single crystal silicon using a silicon on isolator wafer. Two different types of excitation for square shape resonators were used to stimulate Lame mode and square mode of resonance. The fabricated devices were studied under different bias voltage and in air at room temperature. The highest quality factor measured for the Lame mode resonator was 11,121 and for the square mode was 9,120 for square mode at 3.17 and 4.01 MHz, under the 80 V DC bias voltage across 1.5 mu m actuation gap. It has been shown that by adding raggedy edge, the coupling capacitor has increased. Mass detection capabilities of these resonators were also investigated by adding an extra layer of gold. Frequency and quality factor variation was observed for each of the fabricated resonators. Adding a mass of 76 pgr leads to resonance frequency shift of 3.1 kHz in Lame mode structure. In this experiment quality factor drop was observed because of continues film layer of gold metal, with a thickness of 100 nm.