During the last decade, piezoelectric micromachined ultrasonic transducer (pMUT) have raised a great interest for various applications. In particular, AlN material has been used to build bimorph structures made of two AlN layers sandwiched between metallic electrodes. This kind of pMUT offer good performances for both sensing and actuating because of the multi-electrodes scheme of the design. Yet, this pMUT architecture is expected to be particularly sensitive to residual stress within the AlN layers. At the wafer level, stress dispersion is likely to cause important performance variations. In this paper, we characterize bimorph pMUT working in the 50–250 kHz range to investigate how much stress variations at the wafer level (8'') impact critical pMUT features such as resonant frequency, sensitivity and quality factor. Drive sensitivity up to 216 nm/V are obtained with a single electrode scheme. Two approaches are combined, respectively based on pMUT simulation and curvature meas...

中文翻译：

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AlN基双压电晶片压电微加工超声换能器中残余应力的晶圆级实验研究

在过去的十年中，压电微机械超声换能器（pMUT）对各种应用引起了极大的兴趣。特别地，AlN材料已被用于构建由夹在金属电极之间的两个AlN层制成的双压电晶片结构。由于设计的多电极方案，这种pMUT在传感和激励方面均提供了良好的性能。但是，预计该pMUT架构对AlN层内的残余应力特别敏感。在晶圆级别，应力分散可能会导致重要的性能差异。在本文中，我们对工作在50–250 kHz范围内的双压电晶片pMUT进行了表征，以研究晶片级（8''）上的应力变化如何影响pMUT的关键特性，例如谐振频率，灵敏度和品质因数。使用单电极方案可获得高达216 nm / V的驱动灵敏度。两种方法分别基于pMUT仿真和曲率测量进行组合...