固贴式薄膜体声波传感器的仿真分析

Simulation and Analysis of Fixed Film Bulk Acoustic Wave Resonator

针对布拉格反射栅的特点,选用ta-C作为高声阻抗材料,Al N作为低声阻抗材料。利用COMSOL Multiphysics对布拉格反射栅薄膜体声波传感器(BAW-SMR)建模并对建立的模型进行固体力学和静电学的有限元仿真分析,得到了传感器的谐振频率、不同布拉格反射栅对数下传感器的导纳特性曲线、阻抗特性曲线以及形变位移图。通过对比分析得出当前条件下布拉格反射栅对数为4对时,传感器的阻抗特性曲线平滑,谐振频率为3. 258 GHz;当布拉格反射栅对数为3对或5对时,阻抗特性曲线存在寄生谐振。针对存在寄生谐振的传感器,选取具有3对布拉格反射栅的传感器进行优化,通过改变传感器上电极的尺寸和厚度来消除寄生谐振,实现了对寄生谐振峰的有效抑制,为进一步的研究提供了理论依据。

According to the characteristics of Bragg reflectors,ta-C was chosen as the high-acoustic impedance material and AlN as the low-acoustic impedance material.Solidly Mounted Bulk Acoustic Wave Resonator(BAW-SMR)was modeled by COMSOL Multiphysics and the finite element simulation of solid mechanics and electrics was carried out on the established model,resonant frequency of the device,admittance characteristic curve,impedance characteristic curve and deformation displacement diagram of the devices under different Bragg reflection grating pairs were obtained.Through comparative analysis,the results show that the impedance characteristic curve of the resonator is smooth with the resonant frequency of 3.258 GHz when the Bragg reflectance logarithm is four pairs;When the Bragg reflectance logarithm is 3 pairs or 5 pairs,there is parasitic resonance in the impedance characteristic curve.For devices with parasitic resonances,a device with 3 pairs of Bragg reflectors for optimization was chosen,eliminating parasitic resonances by changing the size and thickness of the upper electrode of the device,whicn enables effective suppression of parasitic resonance peaks and provides a theoretical basis for further research.