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

This study presents the design and implementation of a chip-scale amperometric ethanol sensor using the standard commercially available complementary metal oxide semiconductor (CMOS) process together with the post-CMOS micromachining processes. The presented amperometric sensor consists of a suspended plate with a microhole structure as the working electrode, a fully anchored plate with a microhole structure as the counter electrode, and a microcavity 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 microhole structure could enhance its surface area to improve the sensitivity of the sensor. The suspended working electrode covered a thinner NafionR 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 s. The presented design shows the CMOS-MEMS is a promising approach to realize the amperometric ethanol sensor.

Automated summary

This study designs and implements a chip-scale amperometric ethanol sensor using the standard commercially available CMOS process and post-CMOS micromachining processes. The sensor consists of a suspended plate with a microhole structure as the working electrode, a fully anchored plate with a microhole structure as the counter electrode, and a microcavity as the electrolyte reservoir. By exploiting the metal and dielectric layers in the CMOS process, the sensor achieves enhanced sensitivity and response time. Measurements show that the sensor has a sensing range of ppm (20-1000 ppm) at room temperature, with a sensitivity of 0.01 nA/ppm and a response time of 6 s. The presented design demonstrates the potential of CMOS-MEMS for amperometric ethanol sensing.