A novel electro-acoustic chemical sensor based on thin film bulk acoustic resonators (TFBAR) is presented. The principle of operation is the same of the well known quartz crystal micro-balance (QCM), where the frequency of operation is extended from the limit of a few tens of MHz to several GHz. The larger output sensor signals, associated to higher frequency operation, is a condition to develop devices with improved sensitivity. TFBARs have been implemented on (001) Si wafers, using Si3N4/AlN membranes, obtained by anisotropic chemical etching from the back side of the Si substrate. The performances of the TFBAR sensor have been tested using a thin Pd chemical interactive membrane (CIM) deposited on the etched side of the membrane and exposed to different concentrations of hydrogen in nitrogen. Time response upon different cycles of H2 adsorption and desorption are reported together with the sensor calibration curve. The operation frequency of the device, in the GHz range, allows to obtain large responses. The device itself results robust in construction and miniaturized in size. Time stability, repeatability and sensitivity have been tested and reported.
Thin film bulk acoustic wave resonator (TFBAR) gas sensor
M Benetti;V Foglietti;F Di Pietrantonio;E Verona
2004
Abstract
A novel electro-acoustic chemical sensor based on thin film bulk acoustic resonators (TFBAR) is presented. The principle of operation is the same of the well known quartz crystal micro-balance (QCM), where the frequency of operation is extended from the limit of a few tens of MHz to several GHz. The larger output sensor signals, associated to higher frequency operation, is a condition to develop devices with improved sensitivity. TFBARs have been implemented on (001) Si wafers, using Si3N4/AlN membranes, obtained by anisotropic chemical etching from the back side of the Si substrate. The performances of the TFBAR sensor have been tested using a thin Pd chemical interactive membrane (CIM) deposited on the etched side of the membrane and exposed to different concentrations of hydrogen in nitrogen. Time response upon different cycles of H2 adsorption and desorption are reported together with the sensor calibration curve. The operation frequency of the device, in the GHz range, allows to obtain large responses. The device itself results robust in construction and miniaturized in size. Time stability, repeatability and sensitivity have been tested and reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
