Research On AlN Piezoelectric Thin Film Preparation And Application

With the development of mobile communication technology,the communication frequency band continues to increase,and the working bandwidth will be further increased,which puts forward new requirements for the performance of existing filters.Traditional surface acoustic filters are limited by the lithography process,and their working frequency band is low,which cannot meet the development needs of high frequency in the communication frequency band.So the filter based on the thin film body acoustic resonator（FBAR）has entered people’s field of vision with it is strong performance,small size,high power and high working frequency band.However,the requirements of FBAR filter for equipment,process and materials are very demanding,so the preparation and the large-scale productization of FBAR filter are extremely difficult.Because of above problem,the research on the preparation process of FBAR filter has become the top priority.Starting from the working principle and structure of the FBAR,this thesis expounded the influence exerted on the FBAR depended on the performance of each layer of film.Through the comparison,the materials used in each layer of film were determined,which further led to the principle and structure of FBAR filter and determined the structure of the resonator and filter respectively.Then,the preparation process of the most critical piezoelectric film and electrode film in the resonator was systematically studied.The influence of sputtering power,sputtering air pressure and gas flow ratio on film selection orientation and crystallization quality was explored,and the optimization of coating process was completed.After optimizing the coating process,the Mason equivalent circuit model of the FBAR was established and simulated in the simulation software.Then the resonators were cascaded and designed in the software to form an FBAR filter.According to the design scheme,the FBAR filter was prepared and it’s performance was measured.Compared with the simulation results,the center frequency and bandwidth of the FBAR filter were optimized.At last the FBAR filter which could be applied to3400 MHz-3500 MHz had been manufactured successfully.