Post-processing gap reduction in a micromachined resonator for vacuum pressure measurement

This paper describes the application of a micromachined resonator to verify the vacuum pressure and sealing of cavities in micromechanical components. We use an electrostatic driven and capacitively sensed bulk silicon resonator fabricated by Bonding and Deep Reactive Ion Etching (BDRIE) technology. The resonator operates at the first fundamental frequency. The damping is used as a degree of the pressure. Transversal comb structures act as squeeze film damping sources. Post-processing gap reduction substructures are used to increase the damping in the vacuum pressure range. This method makes it possible to observe the pressure over the time of smallest gas volumes by monitoring the damping of integrated micro mechanical resonant structures. Therewith it is possible to estimate the hermetic sealing quality of the closed sensor package. A transfer curve with a logarithmic characteristic is measured.