Ultra-High Sensitivity Pull-In Time Mems Accelerometer for Satellite Gravimetry

Satellite gravimetry applications require sub-ng acceleration resolution at frequencies below 100 mHz, demanding low-noise (mechanical-thermal, 1/f and electronic) and high-sensitivity MEMS sensors. The electrostatic pull-in time-based transduction enables very high sensitivities (75 μs/(μm/s
²
) demonstrated) compared to direct capacitive transduction. The high-resolution requirement calls for large masses and compliant springs (at the limit of manufacturability), resulting in microstructures that require special encapsulation mechanisms. Hence, novel stoppers were designed to limit in- and out-of-plane displacements and improve robustness. Squeeze-film damping was tuned/maximized with dummy parallel-plates (to decrease the device quality factor) since the sensitivity of pull-in time-based operation strongly depends on it.