Microcantilever humidity sensor based on embedded nMOSFET with ≪100≫-crystal-orientation channel

This paper reports a novel silicon microcantilever sensor with an embedded n-type metal-oxide semiconductor field-effect transistor (nMOSFET) for the detection of relative humidity (RH) based on the surface stress sensing principle. The nMOSFET has a channel along <100> crystal orientation of (100) silicon, which is parallel to the microcantilever. The RH detection is realized by coating a thin gold film on the bottom surfaces of the microcantilevers and then a self-assembled monolayer of 4-mercaptobenzoic acid on the film. The output voltage of the sensor as a function of RH is linear, and the sensitivity is up to 4.38 mV/1% RH at room temperature.