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Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering)  2009, Vol. 10 Issue (10): 1413-1420    DOI: 10.1631/jzus.A0820757
Radio Electronics     
An in-plane low-noise accelerometer fabricated with an improved process flow
Xu-dong ZHENG, Zhong-he JIN, Yue-lin WANG, Wei-jun LIN, Xiao-qi ZHOU
Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
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Abstract  We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow, by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor. The improved flow greatly lowers the footing effect during deep reactive ion etching (DRIE), and increases the proof mass by 54% compared to the traditional way, resulting in both improved device quality and a higher yield rate. Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair, which eliminates the nonlinear behavior by fixing the parallel-plate gap. The damping coefficient of the sensing motion is low due to the slide-film damping. A large proof mass is made using DRIE, which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage. The theoretical Brownian noise floor is 0.47 μg/Hz1/2 at room temperature and atmospheric pressure. The tested frequency response of a prototype complies with the low damping design scheme. Output data for input acceleration from −1 g to 1 g are recorded by a digital multimeter and show very good linearity. The tested random bias of the prototype is 130 μg at an averaging time of around 6 s.

Key wordsMEMS accelerometer      Deep reactive ion etching (DRIE)      Footing effect      Capacitive sensing     
Received: 31 October 2008     
CLC:  TN304.12  
Cite this article:

Xu-dong ZHENG, Zhong-he JIN, Yue-lin WANG, Wei-jun LIN, Xiao-qi ZHOU. An in-plane low-noise accelerometer fabricated with an improved process flow. Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(10): 1413-1420.

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http://www.zjujournals.com/xueshu/zjus-a/10.1631/jzus.A0820757     OR     http://www.zjujournals.com/xueshu/zjus-a/Y2009/V10/I10/1413

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