CMOS-Compatible Mid-Infrared MEMS Thermopile Integrated With an RTD For Flame Sensing In IoT Application

Mid-infrared (MIR) detectors compatible to CMOS process are critical devices for efficient cost, compact MIR flame sensing systems in internet of things (IoT) application. In this work, we report a RTD-integrated CMOS-MEMS MIR detector with a metamaterial for effectively filtering the 4.26 mu m wavelength. CMOS-compatible MEMS process (ETRI 6 inch 0.8 um CMOS-MEMS) was applied to a thermopile, leading to the simple 7-photolithograpy process and the area of 1.6 mm by 1.6 mm. The detectivity (D*) and the photosensitivity were 1.1 x 10(8) cm-Hz(0.5)/W and 54 V/W at 1 atm, respectively. In addition, the RTD formed of P-type polysilicon was implemented as a reference resistor for flame detection, where the measured resistivity and TCR were 0.078 ohm-mu m and 0.0038 1/K, respectively. The detector equipped with the metamaterial absorber shows a relatively enhanced absorptivity of 0.34, compared to 0.09 for the only absorber at the 4.26 mu m wavelength. Furthermore, the sensor module with a two-stage amplifier with more than 60 dB gain was linked to the Bluetooth 4.1-based Arduino UNO sensor node. After sensing at 20 msec intervals, the signal was transmitted every 2 sec. The MIR MEMS thermopile shows to be applicable to the field of multifunctional low-cost IR flame detection in IoT application.