MEMS-based NO2 gas sensor using ZnO nano-rods for low-power IoT application

A micro-electro-mechanical-system (MEMS)-based NO2 gas sensor was fabricated and characterized by using ZnO nano-rods for the Internet of Things (IoT) monitoring system. The implementation process was fully compatible with the standard 6-inch 0.8-μm complementary metal oxide semiconductor (CMOS) process for mass-production, resulting in the simple 5-photomask process. In addition, for high sensitivity applications, semiconducting ZnO nano-rods were chosen and synthesized using the hydrothermal method at temperatures below 100 °C. Based on the ZnO nano-rods and the fast response time of a MEMS-based heater, the NO2 gas sensor had a sensitivity of 0.36 at 0.5 ppm. Furthermore, a power consumption of 15 mW in the normal operation mode was achieved with a MEMS-based micro-heater, showing that the preliminary result can be applied for IoT applications operating at low power.