Small Size And Highly Sensitive Differential MEMS Accelerometer Based On Double-Ended Tuning Fork Resonators

Here, a frequency modulated MEMS accelerometer encapsulated in vacuum is presented. The small size (0.25 mm²) and the capability of encapsulation at low pressures (≈ 150 Pa) are the main advantages reported. A high sensitivity (85 Hz/g) for a single double-ended tuning fork (DETF) resonator is achieved due to the addition of a force amplification mechanism, fully optimized through finite-element method analysis (FEM). Since a differential approach, composed by two DETF resonators, is implemented, the sensitivity is doubled to approximately 170 Hz/g. The structures have been fabricated using a commercial process (19 μm thickness active layer) and later characterized to validate the design. Device sensitivity, its temperature dependence (2 Hz/°C) and dynamic behavior have been experimentally measured.