自顶向下贯穿腐蚀制备空腔型FBAR的方法

Top-down Through-via Wet Etching Method to Fabricate Cavity Type FBAR

牺牲层释放是空腔型薄膜体声波谐振器(FBAR)工艺中形成空腔结构的关键步骤,牺牲层释放的效果直接决定了空腔型FBAR的谐振特性。根据空腔型FBAR中气隙的功能和结构特点,提出了自顶向下贯穿腐蚀牺牲层制备镂空空腔型FBAR的创新工艺方法。为验证该方法的可行性,采用MATLAB对牺牲层腐蚀的恒扩散系数(CDC)模型进行数值迭代,采用Silvaco软件对其腐蚀过程进行仿真,根据仿真结果提出释放窗口的优化设计;采用ANSYS软件对镂空FBAR的谐振特性进行有限元仿真分析,对比常规FBAR发现,镂空FBAR具有较好的谐振特性,且其阻抗零点、阻抗极点频率向高频段漂移,有效机电耦合系数和品质因数降低。

The sacrifice layer release is the crucial process step to form the cavity structure of the cavity type film bulk acoustic resonator （FBAR）,and the sacrifice layer release result directly determines the resonance charac teristics of the cavity type FBAR. Based on the insight of the functional and structural characteristics of the air gap in the cavity type FBAR,a novel process method named as the top-down through via wet etching to fabricate the apertured cavity type FBAR is proposed. To validate feasibility of the novel fabrication method, the constant diffusion coefficient （CDC） model numerical iteration of sacrificial layers corrosion process was simulated by MATLAB, and the corrosion process was also simulated by Silvaco software. According to the simulation results, the optimum de sign of release window is proposed. The resonance simulation of FBAR without release window and with release window have been analyzed with FEA software ANSYS. Comparing the simulation results,it shows that the aper tured FBAR still has quite good resonant characteristics, hut the frequency of impedance zero point and impedance pole of the apertured FBAR are drifted to a higher frequency band,and the effective electromechanical coupling coefficient and the quality factor of FBAR are reduced.