A Performance Enhancement Method for MEMS Thermopile Pirani Sensors Through In-Situ Integration of Nanoforests

In this letter, we report a performance enhancement approach for MEMS thermopile Pirani sensors through in-situ integration of nanoforests. The nanoforests not only increase the light absorption of the thermopile, resulting in an improved output voltage, but also increase the contact area and heat exchange sites for gas molecules due to their high porosity and large surface area to volume ratio, subsequently improve the gas heat conduction, extend pressure detection range and increase sensitivity of the Pirani sensor. With integration of the nanoforests, the lower detection limit of the sensor is widened by one order of magnitude compared with the pristine sensor, and the maximum increment in sensitivity reached 56.7%. Moreover, such a sensor can be easily fabricated with a CMOS-compatible process, thus is suitable for mass production. This work provides a new route to enhance performance of current MEMS thermopile Pirani sensors.