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Review
. 2018 Oct 29;9(11):557.
doi: 10.3390/mi9110557.

Microhotplates for Metal Oxide Semiconductor Gas Sensor Applications-Towards the CMOS-MEMS Monolithic Approach

Haotian Liu  1 , Li Zhang  2 , King Ho Holden Li  3   4 , Ooi Kiang Tan  5
Affiliations
Review

Microhotplates for Metal Oxide Semiconductor Gas Sensor Applications-Towards the CMOS-MEMS Monolithic Approach

Haotian Liu et al. Micromachines (Basel). .

Abstract

The recent development of the Internet of Things (IoT) in healthcare and indoor air quality monitoring expands the market for miniaturized gas sensors. Metal oxide gas sensors based on microhotplates fabricated with micro-electro-mechanical system (MEMS) technology dominate the market due to their balance in performance and cost. Integrating sensors with signal conditioning circuits on a single chip can significantly reduce the noise and package size. However, the fabrication process of MEMS sensors must be compatible with the complementary metal oxide semiconductor (CMOS) circuits, which imposes restrictions on the materials and design. In this paper, the sensing mechanism, design and operation of these sensors are reviewed, with focuses on the approaches towards performance improvement and CMOS compatibility.

Keywords: gas sensor; metal oxide (MOX) sensor; micro-electro-mechanical system (MEMS); microhotplate.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Comparison of the size and power consumption of the four types of gas sensors.
Figure 2
Figure 2
(a) The response of a laboratory WO3 based gas sensor and commercial MOX sensor with respect to NO2 in dry and humid air (b) response of the laboratory sensor as a function of NO2 concentration (from [33]).
Figure 3
Figure 3
Schematics of (a) a traditional metal oxide gas sensor and (b) a microhotplate metal oxide gas sensor.
Figure 4
Figure 4
Top view of microhotplates with different configurations: (a) closed membrane; (b) suspended membrane; (c) bridge.
Figure 5
Figure 5
The suspended membrane microhotplate structure formed by (a) front-side etching and (b) back-side etching.
Figure 6
Figure 6
Temperature distribution of a suspended membrane microhotplate without gas sensitive layer (from [54]).
Figure 7
Figure 7
Silicon island and metal heat spreader application on a microhotplate.
Figure 8
Figure 8
Heater geometries (a) meander, (b) double spiral, (c) drive wheel.
Figure 9
Figure 9
Coplanar geometry where heating and sensing electrodes lie on the same plane: (a) Au-loaded In2O3 nanofiber gas sensor by Xu et al. (from [89]) and (b) SnO2 nanowire gas sensor by Hwang et al. (from [90]).
Figure 10
Figure 10
Fabrication processes of a suspended membrane microhotplate with backside etching.
Figure 11
Figure 11
Monolithic gas sensor fabricated with silicon on insulator (SOI) CMOS technology (from [50]).
Figure 12
Figure 12
Monolithic CMOS-micro-electro-mechanical systems (MEMS) gas sensors: (a) microhotplate array for carbon monoxide detection (from [108]) (b) microhotplate gas sensor with proportional-integral-derivative (PID) controllers (from [125]), (c) microhotplate gas sensor with mixed-signal architecture (from [125]), (d) microhotplate gas sensor using biased current measurement (from [126]).
See this image and copyright information in PMC

References

    1. Mitzner K.D., Sternhagen J., Galipeau D.W. Development of a micromachined hazardous gas sensor array. Sens. Actuators B Chem. 2003;93:92–99. doi: 10.1016/S0925-4005(03)00244-2. - DOI
    1. Yamazoe N. Toward innovations of gas sensor technology. Sens. Actuators B Chem. 2005;108:2–14. doi: 10.1016/j.snb.2004.12.075. - DOI
    1. Bhattacharya S., Sridevi S., Pitchiah R. Indoor Air Quality Monitoring using Wireless Sensor Network; Proceedings of the 2013 International Conference on Electrical, Electronics and System Engineering (ICEESE); Kuala Lumpur, Malaysia. 4–5 December 2013; pp. 60–64.
    1. Fine G.F., Cavanagh L.M., Afonja A., Binions R. Metal oxide semi-conductor gas sensors in environmental monitoring. Sensors. 2010;10:5469–5502. doi: 10.3390/s100605469. - DOI - PMC - PubMed
    1. Wetchakun K., Samerjai T., Tamaekong N., Liewhiran C., Siriwong C., Kruefu V., Wisitsoraat A., Tuantranont A., Phanichphant S. Semiconducting metal oxides as sensors for environmentally hazardous gases. Sens. Actuators B Chem. 2011;160:580–591. doi: 10.1016/j.snb.2011.08.032. - DOI

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