Resistive humidity microsensor with circuit manufactured by the CMOS process

Fabrication of a resistive humidity microsensor integrated with sensing circuit on-a-chip using the complementary metal oxide semiconductor (CMOS) process was investigated. The sensor generates a change in resistance as the sensitive film absorbs or desorbs vapor, and the sensing circuit converts the resistance of the sensor into the voltage output. Area of the humidity sensor chip is about 2 mm2. The sensitive film of the humidity sensor is polyaniline doped polyvinyl alcohol (PVA), which is prepared by the sol-gel method. The humidity sensor requires a post-CMOS process to coat the sensitive film. The post-CMOS process utilizes wet etching to remove the sacrificial oxide layer for obtaining the interdigitated electrodes of the sensor, and then the sensitive film is deposited on the interdigitated electrodes. Experimental results show that the integrated humidity sensor has a sensitivity of about 12.9 kΩ/%RH at 25 °C.