A Three-Stack Silicon Wafer Direct Bonding MEMS Tilt Sensor With Less Than 0.005° Angle Repeatability

This paper presented an ultra-high angle resolution MEMS tilt accelerometer with a new sandwich-like structure based on a three-stack silicon wafer direct bonding processes. The scheme is implemented using a system of micromachined single side cantilever spring beam and three-stack silicon structure as a large capacitive sensing mechanism. A proof of concept of a lateral-axis sandwich-like accelerometer with a mechanical sensitivity of 55.0 pF/g (initial capacitor of 160 pF）has been designed, simulated and fabricated, and results from its evaluation are presented in this paper. The electronics interface is based on a new integrated digital (Sigma-Delta Modulation) closed-loop ASIC chip without requiring multiple high-precision ADCs. Experimental results show that the presented sandwich-like MEMS accelerometer exhibits a mechanical sensitivity of 46.5 pF/g with a ±0.05 % FS non-linearity within the ±16° linear range , an average bonding strength of 33.7MPa, a noise floor of 1μg/√Hz , an angle resolution of 0.00057° and a tilt angle repeatability of less than 0.005 °.