Design and Fabrication of 2-axis Vibratory MEMS Gyroscope with In-plane Sensing

Abstract

Gyroscopes (gyro) are devices that measure angle or angular rate, based on the principle of conservation of angular momentum. Conventional gyros show very high performance, but they are expensive, large, and merely portable. Micromachined gyros are increasingly in demand as technology gets developed, because of their small, inexpensive, portable, low-power consuming characteristics. Moreover, multi-axis gyro has advantages over integrated 1-axis gyros

volume, cost, and system complexity can be reduced. Most of multi-axis gyro uses tilting of proof-mass to measure angular rate.In this research, novel 2-axis vibratory gyro based on Coriolis Effect with in-plane sensing is proposed. Its fabrication process combines both surface micromachining – p+ etch stop – and bulk micromachining – DRIE – to achieve required 3-DoF. First, key features of the gyro are proposed and studied. It has translational 3-DoF orthogonal to each other, one for driving and the other two for sensing. Driving z-axis DoF is realized by p+ etch stop beam, while sensing x-y in-plane DoF is realized by DRIE. It uses different beams for each vibration mode, so the mechanical coupling is minimized. Second, the fabrication process of the gyro is suggested. Associated MEMS processes are given. Third, its angular rate measuring experimental results are shown

scale factor of 1mV/[deg/s] has been resulted. Last, suggestion for performance enhancement is presented. It includes sensing electrode shape change and capacitance enhancing actuator.