Frequency-Modulated MEMS Accelerometer with Dual-Layer Process for Minimum Area Occupation of Anchor Points

A dual-layer process for inertial sensors is used to design frequency-modulated (FM) MEMS accelerometers where the positioning of anchor points takes up a minimum area, so to guarantee robustness against substrate bending. The device relies on a continuous mode-reversal principle to ensure at the same time zero-g-offset (ZGO) stability and wide full-scale range (FSR). As the scale-factor (SF) goes with the fourth power inverse of the gap between the proof mass and tuning plates, substrate deformations may significantly affect stability. However, the dual-layer process enables positioning the anchors to the substrate within (150 x 18) μm2, yielding not only 7-μg/°C uncalibrated ZGO stability, but also 0.2%/°C uncalibrated SF stability, overall overcoming the performance of state-of-the-art sensors designed for 64-g FSR.