Design,Fabrication And Characterization Of SMR Fully Insulated Bragg Reflector

The fixed-film bulk acoustic wave resonator is a kind of bulk acoustic wave resonator.Because it adopts a Bragg reflection grating with alternating high and low acoustic impedance layers as a reflection structure of sound waves,the mechanical stability is good,and the Bragg reflection grating structure blocks sound waves.The propagation,so that the energy is retained in the piezoelectric oscillator stack to the maximum extent,has become a hot spot in the research of bulk acoustic wave resonators.Among them,the low impedance layer material of the reflector grating is widely used in the industry.Silicon dioxide(Si O2)is widely used in the industry.The selection of high impedance material,such as tungsten(W)and heavy metal as high impedance material,will lead to strong capacitance coupling between the conductor and dielectric structure,which will affect the device performance.Therefore,the bulk acoustic resonator with the fully insulated Prague reflector structure has become a hot topic in the industry.Acoustic impedance is directly related to material density and elastic modulus.To ensure the performance of the device,it is necessary to choose a structure composed of high modulus non conductor material and low modulus material to form a fully insulated reflective grating.In view of these problems,the following work has been carried out:A mathematical model of a bulk acoustic wave resonator with a fully insulated Bragg reflector is constructed.The working principle and characteristics of the piezoelectric stack are analyzed,and the mathematical model of the piezoelectric film is constructed.The expression of the piezoelectric stack impedance is solved,and the impedance of the FBAR under ideal conditions is calculated.The result clearly shows the impedance characteristics of the FBAR at the resonance point.The resonance characteristics of the electrode FBAR are further analyzed.The loss determines the quality factor Q,and the increase of the sound path will cause the resonance frequency to decrease.The Bragg reflection grating is simulated and designed by transmission line theory.The equivalent circuit diagram of the fixed-film bulk acoustic wave resonator is obtained.The influence of Bragg reflection grating composed of different high acoustic impedance materials on the thermal performance of the device is calculated by simulation analysis.The equivalent circuit is simulated,and the influence of the variation of the Bragg reflection grating on the FBAR is analyzed.The optimization scheme of the preparation model required by the experiment is obtained.The process methods for preparing Bragg reflection grating film materials and the methods for studying film properties are introduced.The influence of Bragg reflection grating structure on the materials used in Bragg reflection gratings is studied,and the preparation process of different materials is analyzed.influences.The film material required for a fully insulated Bragg reflector is prepared and characterized.Considering the simulation and experimental results,the influence of quality factor Q,FBAR internal temperature and maximum thermal stress on the number of Bragg reflection grid layers is analyzed.The internal temperature and maximum thermal stress of FBAR increase with the increase of the number of reflective grid layers.The quality factor Q increases as the number of reflective gate layers increases.The reflection grid temperature is inversely proportional to the thermal conductivity of the material of the reflective grid.The higher the thermal conductivity,the lower the temperature.When the number of Bragg reflection grating layers is n>6,the material has little effect on the reflection efficiency,so the most suitable layer of high and low acoustic impedance materials is 6 layers.Due to its high Young's modulus and good surface roughness at high temperatures,nano-diamond film is a good candidate for a high-impedance layer of fully insulated Bragg reflector.