This paper describes a MEMS triaxial gyroscope utilizing three-dimensional piezoresistive elements. MEMS gyroscopes are widely used for robot motion control, drones, mobile phones and so on. Although a piezoresistive sensing element has the potential for high sensitivity to angular velocity via vibrations that occur due to the Coriolis force, a commonly used piezoresistor, which is formed on a device surface, is not suitable to measure in-plane deformations. Thus, it is difficult to realize a sensing element for a triaxial gyroscope with conventional piezoresistors, especially an element for the detection of vertical axis angular velocity. Here, we propose a triaxial gyroscope utilizing surface and sidewall doping piezoresistors as the sensing element. The surface and sidewall doping piezoresistors detect out-of-plane and in-plane vibrations due to the corresponding three-dimensional Coriolis forces, respectively. As a result, the triaxial angular velocity becomes measurable. The experimental results show that the fabricated gyroscope responds to three-dimensional angular velocities with low crosstalk. Therefore, the proposed gyroscope is suitable for practical angular velocity measurement applications.
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