Microbalance chemical sensor based on thin-film bulk acoustic wave resonators

An electroacoustic chemical sensor based on thin-film bulk acoustic wave resonators TFBAR is presented. It operates on the same principle of the well-known quartz crystal micro-balance, at an operation frequency extended up to several GHz. The larger output signal, associated to the higher operation frequency, is a condition to improve the device sensitivity. TFBARs have been implemented on 001 Si wafers, using Si3N4 /AlN membranes, obtained by anisotropic etching of Si. Time response and calibration curves have been tested on TFBAR sensors exploiting two different chemically interactive membranes: Pd and Co-tetra-phenyl-porphyrin, both deposited in the form of thin-films by thermal evaporation. Measurements performed upon exposure to H2, CO, and ethanol have shown the ability of the device to detect low concentrations of the analyte with a fast and repeatable response