High-Performance CMOS-MEMS No2 Gas Sensors with Inkjet Printed ZnO on Pillar Electrodes

This study presents a high-performance CMOSMEMS$\text{NO}_{2}$gas sensor integrating inkjet-printed ZnO nanoparticle thin films on pillar array electrodes. The sensing chip was fabricated using the standard TSMC$0.18 \mu \mathrm{m}$CMOS platform, which leverages its multilayer stack structure to define the pillar array electrodes. The sensor operates under UV activation, enabling room-temperature detection by enhancing the reaction between ZnO and oxidizing$\text{NO}_{2}$molecules through photogenerated carriers. Material analyses confirm the high quality and uniformity of the inkjet-printed ZnO films. Experimental results show that the pillar array electrodes markedly improve sensitivity compared with conventional interdigitated electrodes (IDEs), achieving responses over 3500 % at 50 ppm and 1400 % at$5 \text{ppm} \text{NO}_{2}$, about one order of magnitude higher than IDEs. Overall, this work demonstrates that the heterogeneous integration of CMOSMEMS pillar array electrodes with inkjet-printed nanomaterial films provides a compact, CMOS-compatible platform for high-sensitivity gas sensing.