Humidity measurement using resonating CMOS microcantilever structures

Changes in relative humidity can be detected by the modification in resonance frequency of an oscillating microcantilever. Mass changes due to the absorption of water vapour by an applied hygroscopic porous thin film create these frequency shifts. We have designed and tested a CMOS micromachined cantilever microstructure sensitive to relative humidity values ranging from 5-90%. Two thin films (1 and 1.5 /spl mu/m) of MgF/sub 2/ applied to the microstructure using the GLAD/sup TM/ deposition technique, were investigated with resonant frequency shifts of approximately 100 Hz observed over the stated humidity range.