基于耦合效应的高性能PMUTs工作机理与测试技术研究

Due to the advantages of Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) in small volume, low power consumption and good impedance matching ability with the acoustic field medium, it now has been widely applied in medical facilities, consumer electronics, industrial on-line monitoring system etc. It also becomes a research hotspot in the fields of ultrasonic transducers. According to the PMUTs’ common problems of low ultrasonic emission sensitivity, narrow bandwidth and heavy cross-talk between array elements, the project presents the methods based on parametric excitation and fluid-structure interaction to amplify the vibration amplitude of PMUTs and reduce cross-talk effect between each array element. Then, PMUTs element vibration property and array ultrasonic emission characteristics will be improved. The research is aiming to illustrate the following three key scientific working mechanisms of PMUTs, which are the influence from the structural parameters to parametric amplification factor, the coupling mechanism between the vibration mode and fluid medium, and the cross-talk mechanism between each array element. Also PMUTs chip will be designed and fabricated. The theoretical model and designing method for the PMUTs element and array will be verified by the calibration and corresponding application research. By this means, a solid foundation will be set for the development of high-performance PMUTs and widen its application field.

压电式微加工超声换能器（Piezoelectric Micromachined Ultrasonic Transducers，PMUTs）以其体积小、功耗低、与声场介质阻抗匹配性好等优点，广泛应用于医疗设备、便携式电子产品、工业在线监测系统等领域，是超声换能器的研究热点。针对目前PMUTs发射灵敏度较低、分数带宽窄、阵列单元间串扰严重等共性技术问题，本项目提出基于参数化激励的振动耦合与单元内部耦合强化的流固耦合方法，实现PMUTs单元振动增幅，降低PMUTs阵列单元间串扰，提高PMUTs单元振动特性与阵列超声发射特性。主要围绕PMUTs单元结构对参数化激励下振动增幅的影响规律、单元振型与声场流体耦合作用机制和阵列单元间相互耦合机理等关键科学问题展开研究，实现PMUTs芯片的设计与制备，通过标定与应用研究对PMUTs单元及阵列设计理论进行验证，为高性能PMUTs的研制与拓展应用奠定技术基础。

针对现有压电式微加工超声换能器（Piezoelectric Micromachined Ultrasonic Transducers，PMUTs）存在超声发射灵敏度不足、分数带宽小导致成像分辨率低以及相邻单元的串扰抑制整个PMUTs阵列超声发射性能等难题，开展低功耗、高性能PMUTs的机电耦合理论、结构设计与优化、关键制备工艺研究及性能测试研究，以获得具有高超声发射灵敏度、大分数带宽以及高阵列超声发射特性的高性能PMUTs。首先，构建了PMUTs单元以及阵列的电-机-声耦合力学模型，通过耦合力学模型对结构参数以及激励方法作用于单元结构振动特性的影响进行研究，研究了薄膜变形、谐振频率、超声发射和接收灵敏度等主要性能参数与结构参数、激励之间的变化关系，探索了机电耦合系数和高精度等效电路模型理论分析方法。其次，开展了高性能PMUTs结构设计与优化研究，探明了主要结构及材料参数对主要性能的影响规律，提出单元结构设计方法，提高了PMUTs单元的发射灵敏度、分数带宽等性能指标，并通过耦合力学模型研究阵列参数对PMUTs阵列超声发射特性的影响规律，提出了阵列结构设计方法。最终，基于MEMS技术制定了高性能PMUTs芯片制备工艺流程，突破了关键工艺，确定了相关工艺参数，完成了PMUTs芯片流片。最后，完成了PMUTs芯片性能标定测试研究以及典型的应用研究，通过实验验证了所提出的耦合力学模型、设计理论与方法的正确性。因此，本项目研究按照申请书研究内容执行，达到了预期的研究目标。