Design of a MEMS Gyroscope with Glass-Silicon-Glass Sandwich Structure

Due to their small size, low energy consumption, low cost and long life-time, MEMS (Micro-electromechanical Systems) vibratory gyroscopes have attracted tremendous interest among researchers. In this paper, a novel bulk-micromachined electrostatic comb-driven, differential capacitance sensing MEMS vibratory gyroscope based on glass-silicon-glass sandwich-structure is proposed. The novel structure eliminates the parasitic capacitances of the gyroscope, which greatly eases the signal sensing. Furthermore, due to the device structure design, the sensing vibration is not coupled to the driving vibration, which improves the device stability. In the driving mode, the gyroscope is activated to vibrate along X axis by electrostatic comb driving. If there is angular velocity along Y axis, the central mass experiences Coriolis force along Z axis which activates the sensing vibration of the central mass along Z axis. The size of the driving beams and sensing beams are carefully chosen to reduce the frequency mismatch between driving and sensing modes, which increases the gyroscope sensitivity. The working principle and dynamic analysis of this gyroscope are given and a set of optimized design parameters are derived based on the analysis. ANSYS FEM simulation is used to find out the device frequency and verify the theoretical prediction. The fabrication flow of the MEMS gyroscope is also proposed. The proposed MEMS gyroscope can be used for inertial sensing in automobile, aerospace, and consumer products.