Research On Simulation Design And Fabrication Of AlN Film Bulk Acoustic Resonator

The selection and control of frequencies in the 5G communication era has become one of the key issues in the RF front-end.The filters and duplexers in the RF front-end modules are important components for the selection and filtering of communication frequency bands.In 5G mobile communication equipment,RF filters are required to have high frequencies,multiple frequency bands,low insertion loss,and wide frequency bands to support 5G new frequency bands.The thin film bulk acoustic resonator(FBAR)device has the advantages of high frequency,low insertion loss,high quality factor(Q value),small size,and integration with IC technology.It has broad application prospects in the field of new generation wireless communication systems and sensors,but this device The core technology is in the hands of a few developed countries,so the research on high-performance FBAR devices is of great significance to the development of my country’s 5G communications.In view of the domestic wireless communication requirements for high-frequency,large-bandwidth,and small-volume FBAR filters,as well as the current problems of low electromechanical coupling coefficients and spurious modes affecting the performance of this device,this paper conducts research on FBAR.Firstly,COMSOL Multiphysics software is used to build a two-dimensional model of FBAR resonator,analyze the relationship between the thickness of the piezoelectric layer and the passivation layer and the resonance frequency,and obtain the optimal pressure that meets the design specifications.The thickness of the electrical layer and the thickness of the passivation layer.The basic three-dimensional model of composite structure FBAR is established,and the stress distribution,potential distribution and frequency response curve of FBAR are analyzed.The working range of FBAR was 2 606～2 684 MHz,the electromechanical coupling coefficient was 7.2%,and the Q_sand Q_pare 2 444.3 and 2 820.8,respectively.But the resonator has many spurious modes.Aiming at the disadvantage of too much spurious resonance of compound structure FBAR,a FBAR with frame structure is simulated and designed,which can effectively suppress the spurious mode.Secondly,AlN films with high c-axis orientation were fabricated on the basis of simulation design parameters.Five FBARs with different effective resonant areas were successfully prepared,and the electromechanical coupling coefficients were all around6%～7%.It is found that as the resonance area increases,the bandwidth gradually increases from 65.6 MHz to 76.5 MHz.Finally,in order to solve the problem of low electromechanical coupling coefficient and small bandwidth of AlN film bulk acoustic wave resonator,FBAR based on Al Sc N piezoelectric film was prepared.The test results show that the Q value of the doped resonator is reduced to a certain extent,but the electromechanical coupling coefficient from 6.3%to11%,and the bandwidth from 67.1 MHz to 113.7 MHz.Then,according to the simulation results of FBAR with frame structure,Al Sc N FBAR with frame structure is prepared.Compared with FBAR without frame structure,this structure can suppress the spurious modes in the passband and improve the Q_pvalue of the resonator by 16.7%.