A Dual-Axis Resonant Accelerometer Based on Electrostatic Stiffness Modulation in Epi-Seal Process

We report on the implementation of a novel vacuum-encapsulated dual-axis resonant accelerometer utilizing electrostatic stiffness modulation. Novel flexure designs are used to enable fully-decoupled in-plane dual-axis translational motions of the proof-mass to achieve low cross-axis sensitivity with the translational mode frequencies above 20 kHz for high bandwidth applications. Differential frequency readout scheme mitigates the temperature effects on frequency stability of resonators and reduces off-axis sensitivity. The fabricated device measures a scale factor of 22Hz/g (119ppm/g) with low cross-axis sensitivity. The accelerometer demonstrates high performance with 18 mu g/root Hz VRW and 27 mu g BI in ambient environment. Optimization of the oscillator circuits and implementation of chip-level ovenization can further improve the performance of the design, with potentials to reach sub-mu g performance for emerging high-bandwidth application.