无线无源单晶FBAR传感器关键技术研究

Wireless and passive sensor has an extensive market in todays industry application. However, the passive sensor based on Surface Acoustic Wave(SAW) devices is not enough for the demand of sensing application that requires small dimension, long distance and high resolution. Therefore, we propose the passive sensor based on Film Bulk Acoustic Resonator (FBAR) device. Traditional FBAR device is based on polycrystalline piezoelectric film, ZnO or AlN， which always have high acoustic loss because of the lattice defects, high innternal stress. Therefore, traditional FBAR device has low effective electromechanical coupling coefficient and Q value， which is not suitable for the wireless and passive sensing application. Compare with polycrystalline piezoelectric thin film, the single crystal possesses a high crystal quality, low lattice defects, acoustic loss and high effective electromechanical coupling coefficient. It is feasible to fabricate high performance FBAR device using single crystal piezoelectric film. Above all, this project proposes the wireless passive sensing using single crystal FBAR. The project is composed of theoretical analysis and experimental characterization. We will carry out the theoretical simulation of single crystal FBAR fabrication, measurement, optimization, and wireless passive temperature sensing. Through this program, fundamental work will be done on the single crystal FBAR design, fabrication, characterization and passive sensing.

无线无源传感有着广泛的工业应用场景，目前广泛研究的无线无源声表面波传感尺寸偏大，难以满足微小空间的远距离高精度传感应用的技术需求，本课题提出基于薄膜体声波谐振器（Film Bulk Acoustic Resonator，FBAR）的无线无源技术。但是目前的FBAR器件中采用的压电薄膜基本为压电多晶AlN和ZnO薄膜，由于多晶薄膜内部的晶格缺陷和内应力等使得多晶薄膜声损耗较大，制备的FBAR器件通常机电耦合系数较低、Q值不高，不适合于无线无源应用。单晶压电材料则具有晶体质量好、晶格缺陷少、声损耗低、机电耦合系数高等优点，有望用于制备高性能FBAR器件，因此，本项目提出研究基于单晶FBAR的无线无源传感器。课题拟从理论和实验两方面出发，完成单晶FBAR器件建模与仿真分析、单晶FBAR的制备、性能表征及优化、无线无源温度传感等工作。

单晶薄膜体声波谐振器在射频电路，传感器中有着广泛应用，其具有工作频率高，品质因子高的特点。本项目围绕单晶薄膜体声波谐振器及其无线无源应用展开，基于单晶LiNbO3薄膜，理论分析了其各个切向的体声波特性，振动模式及阻抗特性，并对Z切的单晶LiNbO3薄膜进行了FBAR的制备，获得了工作频率为5GHz的体声波谐振器，Q值达到900多。针对无线无源传感应用，项目组设计了具有自封装结构的FBAR压力传感器，基于网络分析仪，进行了无线无源压力传感器的应用研究。在此项目的基础上，项目组拓展了基于单晶AlN薄膜的体声波器件开发与研究，并已突破一系列工艺难题。对于推动单晶薄膜体声波器件在高频高Q值方面的应用具有重要意义，包括高频滤波器，高灵敏度传感器，微型无线无源传感器等。