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Sensors 2014, 14(7), 12735-12747; doi:10.3390/s140712735

An Acetone Microsensor with a Ring Oscillator Circuit Fabricated Using the Commercial 0.18 μm CMOS Process

1,*  and 2
1 Department of Mechanical Engineering, National Chung Hsing University, Taichung 402, Taiwan 2 Department of Civil and Environmental Engineering, National University of Kaohsiung, Kaohsiung 811, Taiwan 320, Taiwan
* Author to whom correspondence should be addressed.
Received: 27 May 2014 / Revised: 12 July 2014 / Accepted: 15 July 2014 / Published: 17 July 2014
(This article belongs to the Section Physical Sensors)


This study investigates the fabrication and characterization of an acetone microsensor with a ring oscillator circuit using the commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process. The acetone microsensor contains a sensitive material, interdigitated electrodes and a polysilicon heater. The sensitive material is α-Fe2O3 synthesized by the hydrothermal method. The sensor requires a post-process to remove the sacrificial oxide layer between the interdigitated electrodes and to coat the α-Fe2O3 on the electrodes. When the sensitive material adsorbs acetone vapor, the sensor produces a change in capacitance. The ring oscillator circuit converts the capacitance of the sensor into the oscillation frequency output. The experimental results show that the output frequency of the acetone sensor changes from 128 to 100 MHz as the acetone concentration increases 1 to 70 ppm.
Keywords: acetone microsensor; α-Fe2O3; ring oscillator circuit acetone microsensor; α-Fe2O3; ring oscillator circuit
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Yang, M.-Z.; Dai, C.-L.; Shih, P.-J. An Acetone Microsensor with a Ring Oscillator Circuit Fabricated Using the Commercial 0.18 μm CMOS Process. Sensors 2014, 14, 12735-12747.

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