A Study Of The Effects Of Electrode Layer On The Performances Of Thin Film Bulk Acoustic Resonator Mass Sensor And Viscosity Sensor

Due to its small size,simple structure,high sensitivity,and easily integrated with compatible and semiconductor technology,thin film bulk acoustic resonator(FBAR)has been widely used in industrial production or experimental research including biology,chemistry,physics.Compared with typical QCM,the electrode thickness of FBAR sensor is comparable to the resonator thickness and cannot be ignorable,moreover,it may affect the performances of FBAR sensor,but the study is not systematical.In this study,we systematically investigate the effects of electrode layers on the sensitivity and quality factor of FBAR mass sensor and viscosity sensor application by the two modes that only the undetected side electrode is ignored or double-side electrodes are considered.Firstly,according to the Mason model and one-dimensional transmission-line model,models are built for the FBAR mass sensor and the FBAR viscosity sensor,respectively,and the electric impedance equation,sensitivity equation and quality factor equation are derived;then we simulate the effects of the characteristic feature of single-side detective electrode layer on the performances of FBAR mass sensor and viscosity sensor.Results show that the thickness,characteristic acoustic impedance and quality factor of the electrode have a great effects on the sensitivity and quality factor of FBAR mass sensor and viscosity sensor;the low characteristic acoustic impedance electrode is helpful to sensitivity amplified while on the contrary for the high characteristic acoustic impedance electrode.Moreover,sensitivity and quality factor can be simultaneously improved by choosing appropriate high quality factor low characteristic acoustic impedance electrode.Secondly,based on the single side electrode FBAR mass sensor and FBAR viscosity sensor model,we built the model of double side electrode FBAR mass sensor and FBAR viscosity sensor,and the electric impedance equation,sensitivity equation and quality factor equation are also derived.The results point that the sensitivity can be improved by adding appropriate thickness of low characteristic acoustic impedance electrode and decreases with the thickness of high characteristic acoustic impedance electrode in detection side.Moreover,sensitivity decreases while Q increases with the thickness of undetected side.Finally,according to the theoretical simulation results,the study can be used for the design of high performance FBAR mass sensor and FBAR viscosity sensor.