Sub-degree angle detection using micromachined dome-shaped-diaphragm resonator with wine-glass mode vibration

Abstract

A sensitive, high quality factor (Q), 3-D piezoelectric microelectromechanical systems (MEMS) gyroscope based on wine-glass mode vibration has been designed and fabricated. Experimental results show the functionality of the device as hemispherical rate integrating gyroscope (HRG). The gyroscope utilizes a 1.5-mm-diameter spherical shell made of a LPCVD silicon nitride diaphragm. When the spherical shell is piezoelectrically actuated to vibrate as a four-node wine-glass mode at 126 kHz through a set of four piezoelectric drive elements, an applied angular rotation causes a change of the mode shape, which is piezoelectrically sensed through a set of four piezoelectric sense elements located at 45° off from the drive elements. A sputter-deposited piezoelectric zinc oxide (ZnO) thin film on the diaphragm is used to actuate and sense vibration at the rim of the fabricated dome. The vibration mode is measured to have a Q of about 10 million, and decays at a time constant of 23 seconds when the piezoelectric actuation is halted. With it, the minimum detectable angle of rotation is measured to be about 0.15°.