摘要
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.