Initial frequency split reduction of MEMS ring gyroscope based on cascaded springs geometrical compensation

Abstract

Small initial frequency split is preferred to reduce the complexity of control circuits and enhance the device sensitivity for mode‐matching MEMS gyroscopes. A microring gyroscope with cascaded rectangular beams as supporting springs fabricated by (100) single crystal silicon (SCS) is presented. Frequency split due to the anisotropic of Young's modulus of (100) SCS is geometrically compensated by adjusting the width of cascaded springs and adding an extra mass. The rectangular beams are designed to be wide enough to improve the immunity to fabrication imperfections, obtaining good manufacturing repeatability. The proposed method can largely attenuate the frequency difference of the gyroscope by using (100) SCS, which can reduce the processing cost and be easily integrated with CMOS circuit compared with (111) SCS. The test results show that the average initial frequency split of 15 different devices is 5.1 Hz for the ∼10,430 Hz resonant frequency. The minimum and maximum splits are 2.3 Hz (0.022%) and 7.3 Hz (0.069%), respectively, with the standard deviation of 1.3 Hz.