Piezoelectric Micromachined Ultrasonic Transducers With Superior Frequency Control
Piezoelectric Micromachined Ultrasonic Transducers With Superior Frequency Control
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DOI：
10.1109/jmems.2023.3305461
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发表时间：
2023-12
影响因子：
2.7
通讯作者：
Yi Gong;Menglun Zhang;Sheng Sun;Wenlan Guo;Chen Sun;W. Pang
中科院分区：
文献类型：
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作者：
Yi Gong;Menglun Zhang;Sheng Sun;Wenlan Guo;Chen Sun;W. Pang
压电微机械超声换能器（PMUT）的工艺变化（如残余应力和不良的尺寸定义）恶化谐振频率控制是一个长期存在的问题。这封信提出了一个锥形悬臂集群PMUT与严格的频率控制。PMUT可以通过悬臂梁的变形释放残余应力，其前腔可以精确地限定悬臂梁的边界。理论分析和试验结果表明，该方法消除了残余应力对谐振频率的影响。频率精度和准确度跨芯片，晶圆和批次进行评估。所提出的设计的跨晶片频率均匀性和相对偏差分别为0.8%和1%，这是约一个数量级优于传统的设计。所提出的PMUT在迄今为止报告的PMUT中表现出上级的频率控制，首次满足1%的频率控制要求。在距离为5 mm处测得的发射和接收灵敏度分别为1.15Pa/V/mm ~ 2和0.15mV/Pa。该设计简单且成本有效地实现，而无需严格的制造工艺要求，例如修整或蚀刻优化。它在空气耦合应用中具有竞争力，其中必须对频率匹配进行严格的频率控制，例如超声波气体流量计和波束形成阵列。[2023-0139] 2023 -0139 [2023-0139][2023-0139]
It is a long-lasting issue that process variations, such as residual stress and poor dimension definition, deteriorate resonant frequency control of a piezoelectric micromachined ultrasonic transducer (PMUT). This letter presents a tapered cantilever cluster PMUT with tight frequency control. The PMUT could release residual stress via cantilever deformation and its front cavity could precisely define cantilever boundary. Theoretical analysis and test results show that the impact of residual stress on resonant frequency has been eliminated. Frequency precision and accuracy are evaluated across die, wafer and lot. Across wafer frequency uniformity and relative deviation of the proposed design are 0.8% and 1%, respectively, which are approximately an order of magnitude better than those of conventional design. The proposed PMUT demonstrates superior frequency control among reported PMUTs till date, meeting the 1% frequency control requirement for the first time. The measured transmitting and receiving sensitivities are 1.15 Pa/V/mm2 at a distance of 5 mm and 0.15 mV/Pa, respectively. The design is simple and cost effective to implement without stringent fabrication process requirements such as trimming or etch optimization. It is competitive in air-coupled applications where tight frequency control for frequency matching is a must, such as ultrasonic gas flowmeter and beam-forming array. [2023-0139]