Deposition Of High Frequency SAW Filter Device Cell Based On BN Multilayer Structure

In recent years,the portable informational communications equipment were widely applied to the real life,which makes electronic products to develop in the direction of miniaturization and SAW device is the key device.In addition,with low frequency of communication become congestion gradually,now the high frequency is the trend of the development of communication technology,which makes the high frequency and high power of SAW devices are more and more popular with the designers.In this paper,a series of experiments were designed to optimize the technology of BN film.For example: the growth power,pulse bias,annealing temperature and so on.The obvious change laws were obtained and the cubic content of BN films up to 95% was prepared successfully.Then the deposition technology of AlN films was optimized,including sputtering pressue and distances between the target and the substrate,Al N films with(002)preferred orientation was obtained.Then ZnO/BN and AlN/BN multilayer structures were prepared based on the optimized deposition technology.Multilayer structures with sa me total thickness and different number of layers were prepared and the piezoelectric performance of two layers structure of ZnO/BN films was confirmed to be strongest by PFM.The regularities of propagation velocity V and electromechanical coupling coefficient K2 changed with the thickness of BN films and the thickness of ZnO films were simulated by stiffness matrix based on 2 layers structure.According to the simulation results the thickness of BN films and ZnO films was selected as 0.1 lambda and 0.17 lambda,respectively.Then the S parameters of the SAW devices were calculated by the admittance matrix and the influence of IDT parameters on return Loss and propagation Loss were simulated by Matlab.This simulation provided a reference for the going design of IDT.Finally,SAW filters of ZnO/BN multilayer structure on silicon and diamond substrates were fabricated based on the experiment results and the simulation results.The test outcome of ZnO/BN/Si multilayer structure SAW filter verified the simula tion results and ZnO/BN/Diamond multilayer structure SAW filter reliazed high frequency as 1.23 GHz.The focus of this paper is the design and fabrication of multilayer structure((ZnO/BN and AlN/BN)based on BN films.SAW filter by experiment method combined with simulation method,the simulations guide the experiments and the experiments verified the simulations.In this thesis,the cubic content of BN films was improved to 94.8%,(002)preferred orientated AlN films were prepared,the piezoelectric properties of mutilayer structures were consistent and homogeneous,In addition,the thickness of BN films and ZnO films were optimized by simulation.the experiment results and the simulation results are identical with each other.Through the relevant experimental in this study,this thesis will contribute to the application of BN films to improve the frequency and stability of SAW devices,development of high frequency SAW devices with stable performance and provide relevant experience of the simulation of combined with experiments.