Improved Performance of FET-Type Humidity Sensor With Low-Power Embedded Micro-Heater

This study investigates the performance improvement in sensing characteristics using a poly-Si micro-heater embedded in a Si FET-type humidity sensor. The heater operates with low power due to its small size and heat isolation structure. Adsorption of water vapor on an indium oxide (In2O3) humidity-sensing layer causes an increase in the threshold voltage and a decrease in drain current of the ${p}$ -type Si FET sensor. The heating properties of the heater are investigated. The heater consumes only 0.99 mW at 1.7 V to increase its temperature up to 204.6°C. Utilizing the heater, the sensor has a 3 times higher sensitivity and 4/20 times faster response/recovery speeds at 54.9% RH.