A single-sided micromachined piezoresistive SiO2 cantilever sensor for ultra-sensitive detection of gaseous chemicals

Abstract

This paper presents a novel SiO2 microcantilever sensor for high-sensitive gaseous chemical detection. A thin single-crystalline silicon piezoresistor is integrated in the SiO2 cantilever for low-noise and high-resoluble signal readout. The paper relates the MEMS formation, modeling and detecting experiments of the sensor. The micro-fabrication of the cantilever sensor is processed at a single side (front side) of the silicon wafer, combined with functionalization of a self-assembled monolayer (SAM) on the sensing cantilever for specific molecular capturing. The model of the piezoresistive SiO2 cantilever sensor is given by using both analysis and simulation, resulting in good agreement with the measuremental data. With the cantilever modified by the specific SAM, the detecting performance of the sensor is experimentally obtained. Attributed to the high sensitivity and the low electric noise of the piezoresistive SiO2 cantilever, ammonia gas of 0.1 ppm level concentration and dimethyl methylphosphonate vapor of 10 ppb concentration have been well detected. The integrated cantilevers are promising for inexpensive, highly resoluble and portable chemical/biological detection.