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Open AccessArticle

Optimization of a VOC Sensor with a Bilayered Diaphragm Using FBAR as Strain Sensing Elements

1
School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
2
Xizang Agriculture and Animal Husbandry College, Linzhi 860000, China
3
Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621919, China
*
Author to whom correspondence should be addressed.
Sensors 2017, 17(8), 1764; https://doi.org/10.3390/s17081764
Received: 5 July 2017 / Revised: 29 July 2017 / Accepted: 1 August 2017 / Published: 1 August 2017
(This article belongs to the Section Chemical Sensors)
Film bulk acoustic resonators (FBARs) are widely applied in mass bio-sensing and pressure sensors, owing to their extreme sensitivity and integration ability, and ability to miniaturize circuits. A volatile organic compound (VOC) sensor with a polymer-coated diaphragm, using FBARs as a strain sensing element is proposed and optimized. This vapor sensor is based on organic vapor-induced changes of mechanical deformation of the micro-diaphragm. The four FBARs are located at the edge of the bi-layer diaphragm comprising silicon nitride and silicon oxide for strain extraction. In this work, the strain distribution of the FBAR area under vapor loads is obtained using the finite element analysis (FEA) and the response frequency changes of the FBARs under vapor loads are obtained based on both the first-principle methods to deduce the elastic coefficient variation of aluminum nitride film in FBARs under the bending stresses and the Mason equivalent circuit model of the sensor using ADS software. Finally, optimizations are performed on both the bilayered diaphragm structure and sensing film. The diaphragm with a 0.7 μm silicon nitride layer and a 0.5 μm silicon oxide layer are considered to be the optimized design. The optimal coverage area of the sensing film for the diaphragm is around 0.8. View Full-Text
Keywords: VOC sensor; FBAR; FEA; bilayered diaphragm VOC sensor; FBAR; FEA; bilayered diaphragm
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MDPI and ACS Style

Guo, H.; Guo, A.; Gao, Y.; Liu, T. Optimization of a VOC Sensor with a Bilayered Diaphragm Using FBAR as Strain Sensing Elements. Sensors 2017, 17, 1764.

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