Modelling and Simulation of a Thin-Film Bulk Acoustic Resonator (FBAR) Based Gas Sensor

This work presents the modeling and simulation of a thin film bulk acoustic wave resonator (FBAR) based gas sensor. The Present FBAR device uses the Al/ZnO/Al stack for the detection of volatile organic gas. Polyisobutylene (PIB) is used as a sensitive layer. Design and simulations are carried out by finite element modeling (FEM) software COMSOL Multiphysics 5.4. The mass loading principle is used to sense various volatile organic gases. The proposed FBAR structure shows a good coupling coefficient of 4.178%, high resonance frequency (1.046 GHz), and high-quality factor. The simulated FBAR based gas sensor is tested against various gases such as Trichloroethelene (TCE), Chloromehane (CM), Trichloromethane (TCM), and Dichloromethane (DCM) with PIB as a sensing layer. The shift in resonance frequency is observed by exposing the sensor to various gas concentrations ranging from 50 to 500 ppm. This sensor is sensitive to all mentioned gases and the highest sensitivity was observed in the case of TCM (2.619 MHz/ppm) for 100 ppm. On the other hand, DCM exhibited excellent linearity for a broader range however, the sensitivity (0.354 MHz/ppm) was lower compared to that of TCE and TCM. A comprehensive analysis of various parameters related to gas sensing and FBAR devices is presented in this work.