Study On Stress Loading Effect Of FBAR

Recent years,with the development of thin film bulk acoustic wave resonator(FBAR),it is not only shows great values in RF devices application,but also shows great application potential wihch has been digged out gradually in the field of sensors,such as mass sensor,micro-accelerometer,ambient pressure sensor and so on.The FBAR micro-accelerometer and ambient pressure sensor belong to FBAR mechanical sensor.And there is a common problem in the research of this kind of FBAR sensor-the sensitive mechanism of FBAR is unknown.That is,the reason of stress loading effect of FBAR is not know.This thesis focuses on the problem.On the one hand,intensive study on the stress loading effect of FBAR;on the other hand,find a sensitivity calculation method of FBAR mechanical sensor.The stress loading effect of FBAR is studied.The impedance expression of FBAR under the initial sress is deduced wihch based on the linear electroelastic theory.The relationship between the resonat frequency and the initial stress of FBAR is studied.And the resonat frequency of FBAR under concentrated force is simulated by ANSYS finite element software.In these two cases,the resonat frequency drifts in the opposite direction.The material properties of Al N crystal under different pressures are studied by the first principles calculations.The frequency shift of FBAR under different stress conditions is roughly analyzed by means of the resonance frequency calculation method of ideal FBAR.It is found that the resonace frequency drifts trend the same direction.The sensitivity calculation model or method of FBAR mechanical sensor is put forward.A multiscale model based on Mason model is propsed.The “bridge” wihch is the relationship between pressure and elastic calculated by first principle calculations,connect the Mason model and finite element model of structural mechanics of FBAR.The Calculus-like analysis method is used to calculation the sensitivity of FBAR mechanic sensors.And this method is improved.The enginfrequency solution method is used to solve the resonate frequency,and energy-weighted average method is used to solve the average strain in the thickness direction and the internal pressure,which are usefull for modified the material parameter and geometer of FBAR.Then,the sensitivity of FBAR mechanics can be calculated.The perturbation method which is based on the nonlinear electroelastic theory is discussed.The frequency shift calculation method of FBAR under pure elastic perturbation is introduced.Considering the pure elastic perturbation method is insufficient which is not considered the piezoelectric and dielectric perturbation,therefore,the complete perturbation integral equation is given which includes all perturbation.