A Miniaturized CMOS-MEMS Amperometric Gas Sensor for Rapid Ethanol Detection

• Published in: IEEE sensors journal Vol. 23; no. 8; p. 1
• Main Authors: Thu, Do Thi, Liu, Zong-Han, Lee, Ya-Chu, Kuo, Tzu-Wen, Sung, Wei-Lun, Chu, Yen-Chang, Chueh, Yu-Lun, Fang, Weileun
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.04.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: amperometric gas sensors; Amperometric sensors; CMOS; CMOS-MEMS; Diffusion layers; Electrical measurement; electrochemical gas sensors; Electrodes; Electrolytes; Ethanol; ethanol detection; Gas sensors; Gaseous diffusion; Metals; Microelectromechanical systems; Microholes; Micromachining; Nickel; Response time; Room temperature; Sensitivity; Sensors
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2023.3254881

This study presents the design and implementation of a chip-scale amperometric ethanol sensor using the standard commercially available CMOS (complementary metal oxide semiconductor) process together with the post-CMOS micromachining processes. The presented amperometric sensor consists of a suspended plate with a micro-hole structure as the working electrode, a fully-anchored plate with a micro-hole structure as the counter electrode, and a micro cavity as the electrolyte reservoir. The metal and dielectric layers inherent in the standard CMOS process are exploited to realize these structures. The electrode with a micro-hole structure could enhance its surface area to improve the sensitivity of the sensor. The suspended working electrode covered a thinner Nafion R layer could facilitate gas diffusion to shorten the response time of the sensor. To characterize the ethanol sensing, a Ni film is deposited on the working electrode. Measurements indicate the presented sensor has a sensing range of ppm (20 ~ 1000 ppm) at room temperature. Moreover, its sensitivity and response time are respectively 0.01 nA/ppm, and 6 seconds. The presented design shows the CMOS-MEMS is a promising approach to realize the amperometric ethanol sensor.