空腔型FBAR功率容量的影响因素分析与优化

Analysis and optimization of power-handling capability influence factors of the cavity-type FBAR

机械应力和自热效应是影响空腔型薄膜体声波谐振器(FBAR)功率容量的主要因素。采用ANSYS对声波纵向振荡产生的机械应力进行了结构仿真,发现应力主要集中在空气腔结构附近;对压电薄膜逆压电效应功率损耗产生的自热效应进行了热仿真,发现空气腔和支撑层阻碍了热量向衬底传导。提出了提高器件功率容量的优化设计:为了减小应力集中,可以减小空气腔的深度以限制声波振荡产生的纵向位移;为了提高散热能力,可以将空气腔的深度减小并选取导热系数大的支撑层。优化设计的仿真验证结果表明:空气腔附近的应力集中面积明显减小,最大应力值由16.6 GPa下降到12.8 GPa;同样施加6 mW的功率,器件内部最高温度由113°C下降到56°C;优化设计的空腔型FBAR,功率容量得到了显著提高。

Mechanical stress and self-heating effect of cavity-type Film Bulk Acoustic Resonator (FBAR) are main influential factors for power-handling capability. Structure simulation of mechanical stress produced by longitudinal oscillation acoustic is performed by finite element analysis software ANSYS. The simulation results show that stress concentration is mainly near the cavity. Thermal simulation of self-heating effect produced by power loss of inverse piezoelectric effect in thin film is also performed by finite element analysis software ANSYS, and the simulation results show that air cavity and the support layer stop the heat transfer to the substrate. Optimization design is put forward to increase power-handling capability of the device: in order to reduce the stress concentration, air cavity depth is decreased to limit longitudinal displacement caused by acoustic oscillation; in order to increase the cooling capacity, air cavity depth can be decreased and the support layer with good thermal conductivity should be chosen. Verification simulation of optimization design shows:the stress concentration areas near the air cavity are decreased , and the maximum stress concentration value is from 16.6 GPa to 12.8 GPa;the highest temperature in device decreases from 113 °C to 56 °C under the equal power of 6 W; the power-handling capability of optimized cavity-type FBAR is significantly improved.