Ultrahigh-resolution MEMS Humidity Sensing Elements Based On Film Bulk Acoustic Wave Resonators

A high-resolution humidity sensor based on MEMS FBAR with spin-coated PVA thin film is reported. The sensors exhibit very high sensitivity to water vapor and are able to detect down to 0.08 % change in relative humidity by monitoring the shift in series resonant frequency of the FBARs. The integration of these devices with CMOS oscillating circuits and RF front-end chips will create great potential of FBAR based mass sensors in a wide variety of applications in chemical and biological sensing.