Laterally vibrating MEMS resonant vacuum sensor based on cavity-SOI process for evaluation of wide range of sealed cavity pressure

Abstract

This paper reports a laterally vibrating MEMS resonant vacuum sensor which senses ambient pressure based on the squeeze-film damping effect. The single-anchored double-ended tuning fork structure is proposed to minimize anchor loss and thermoelastic dissipation. The squeeze-film damping gap width is designed to be changeable for the purpose of adjusting the squeeze-film damping effect at different gas pressure. By making the squeeze-film damping dominant and suppressing other energy loss mechanisms, the low pressure end of detectable range is enlarged and as the result a wider detectable pressure range can be achieved. The resonator was fabricated by cavity silicon-on-insulator technique for the purpose of design and fabrication flexibility, and was characterized in a vacuum chamber. The proposed sensor can sense the air pressure at relatively high quality factor from around 60 to 30,000 in the range of 1000–1 Pa. The structure design and fabrication is compatible with standard MEMS processes and provides a path towards the application for the evaluation of the vacuum level of sealed micro-size cavities for wafer level integration.