Ultra-low-power chemiresistive microsensor array in a back-end CMOS process towards selective volatile compounds detection and IoT applications

We describe an ultra-low-power volatile compounds microsensor array towards increased selectivity and sensitivity. The chemiresistive transducers are 100 nm-thick interdigitated gold microelectrodes coated with polypyrrole-based polymer. Two sensors arrays were implemented with respectively 3 × 3 and 2 × 2 pixels², showing a surface per pixel down to 400 × 200 μm². The fabrication is fully CMOS-compatible and the polymer coating is performed at wafer level by electropolymerization, using a differential pulse method from 1.1 to 1.5 V. The polymer film thickness varies from 1.2 to 1.5 μm. Looking at ammonia detection, a sensitivity up to 80 % at 5 ppm in nitrogen is achieved, while consuming below 20 μW continuously. Finally, temperature and humidity effects are analyzed at 25 and 45 °C, from 45 to 95 % RH. Such devices are very promising for remote environmental monitoring applications requiring low-cost low-power sensors associated with dedicated electronics.