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Sensors 2009, 9(12), 10158-10170; doi:10.3390/s91210158

Capacitive Micro Pressure Sensor Integrated with a Ring Oscillator Circuit on Chip

1,* , 1
1 Department of Mechanical Engineering, National Chung Hsing University, Taichung, 402, Taiwan 2 Corporate R&D Headquarter, Canon Inc., Tokyo 146-8501, Japan 3 Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu, 300, Taiwan
* Author to whom correspondence should be addressed.
Received: 30 October 2009 / Revised: 17 November 2009 / Accepted: 23 November 2009 / Published: 14 December 2009
(This article belongs to the Special Issue Advances in Transducers)
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The study investigates a capacitive micro pressure sensor integrated with a ring oscillator circuit on a chip. The integrated capacitive pressure sensor is fabricated using the commercial CMOS (complementary metal oxide semiconductor) process and a post-process. The ring oscillator is employed to convert the capacitance of the pressure sensor into the frequency output. The pressure sensor consists of 16 sensing cells in parallel. Each sensing cell contains a top electrode and a lower electrode, and the top electrode is a sandwich membrane. The pressure sensor needs a post-CMOS process to release the membranes after completion of the CMOS process. The post-process uses etchants to etch the sacrificial layers, and to release the membranes. The advantages of the post-process include easy execution and low cost. Experimental results reveal that the pressure sensor has a high sensitivity of 7 Hz/Pa in the pressure range of 0–300 kPa.
Keywords: micro pressure sensors; ring oscillators; CMOS-MEMS micro pressure sensors; ring oscillators; CMOS-MEMS
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Dai, C.-L.; Lu, P.-W.; Chang, C.; Liu, C.-Y. Capacitive Micro Pressure Sensor Integrated with a Ring Oscillator Circuit on Chip. Sensors 2009, 9, 10158-10170.

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