新型掺碳二氧化硅-薄膜体声波谐振器结构及其仿真验证

一定厚度的低声阻抗支撑层可以在薄膜体声波谐振器(FBAR)与衬底之间形成声学隔离层，防止声波泄漏到衬底当中。掺碳二氧化硅(CDO)是一种低声阻抗材料，对FBAR具有较好的温度补偿效果，可以作为FBAR与衬底之间的声学隔离层，从而构成一种新型的CDO-FBAR。为了分析CDO-FBAR与通孔型FBAR相比性能是否退化，以及CDO声学隔离层所需厚度，采用多物理场耦合仿真软件分析了CDO-FBAR和通孔型FBAR的谐振频率、Q值、有效机电耦合系数和S参数，并提取了CDO-FBAR纵向振动位移。分析结果表明:CDO-FBAR的谐振频率整体向下漂移；CDO声学隔离层导致S参数的寄生干扰；由于声学损耗增加，Q值略有降低，其中并联谐振点处的Q值降幅更大；有效机电耦合系数略有降低；声波传播到声学隔离层中9 m处就完全衰减，即只需要9 m厚的CDO声学隔离层就能在FBAR与衬底之间形成有效的声学隔离。由此，仿真验证了这种新颖的CDO-FBAR结构的可行性。

Novel carbon-doped oxide-FBAR structure and its simulation verification

Low acoustic impedance support layer with a certain thickness between film bulik acoustic resonator (FBAR) and the substrate can form an acoustic isolation layer to prevent sound leakage to the substrate. Carbon-doped oxide(CDO) is a kind of low acoustic impedance material with good temperature compensation for FBAR, and it can be used as acoustic isolation layer between FBAR and the substrate which results in a novel FBAR structure named as CDO-FBAR. In order to analyze whether the properties of CDO-FBAR is degenerated compared with via-hole type FBAR and the required thickness of CDO as acoustic isolation layer, we used multi-physics coupled simulation software to analyze the resonant frequency, the Q (quality factor) value, the effective electromechanical coupling coefficient and S -parameter of the two kinds of FBARs, and to extract longitudinal vibration displacement of CDO-FBAR. The results indicate: the overall resonant frequency of CDO-FBAR is downshift; CDO isolation layer induced parasitic disturbance in S -parameter; because of the increasing acoustic loss, the Q value decreased slightly, and more reduction happened at parallel resonant frequency; and the effective electromechanical coupling coefficient has also reduced slightly; acoustic wave did not completely attenuate until sound wave propagating in the acoustic isolation layer for 9 m, i.e. it needs only 9 m thick CDO material to form an effective acoustic isolation layer between FBAR and the substrate. Thus, the feasibility of the novel CDO-FBAR structure is verified by simulation.