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A dual-frequency piezoelectric micromachined ultrasound transducer array with low inter-element coupling effects
Journal of Micromechanics and Microengineering ( IF 2.3 ) Pub Date : 2021-02-11 , DOI: 10.1088/1361-6439/abde8f
Lifang Liu 1, 2 , Weiliang Ji 1, 2 , Zhanqiang Xing 1, 2 , Xiangyu Sun 1, 2 , Yu Chen 1, 2 , Yijia Du 1, 2 , Feng Qin 1, 2
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This paper presents a dual-frequency piezoelectric micromachined ultrasonic transducer (PMUT) line array with low crosstalk level, which was fabricated on silicon-on-insulator (SOI) wafers with sputtered piezoelectric thin film (PZT) and Si diaphragm structure. The obtained array consists of 120 of 0.77 MHz and 192 of 2.30 MHz PMUT units in total with minimum interspace of 50 μm. Due to the high piezoelectric coefficient of PZT, the PMUT shows high transmitting sensitivity in air and good effective electromechanical coupling factor. The displacement sensitivities are assessed to be 595 nm V−1 and 112 nm V−1 at the resonant frequencies of 0.77 MHz and 2.30 MHz respectively in air. To reduce the vibration coupling, rectangular grooves in the bottom silicon are designed between the adjacent line elements, and the PMUT units in the array are arranged in a mis-aligned style. Modal analysis for the 0.77 MHz units indicates neighbouring coupling-vibration decreases greatly from 44.5% to 14.8% of the excited vibration when the excited line is driven at 4Vpp, which proves both the grooves and the mis-aligned ranking are effective for coupling effect reduction. Moreover, results indicate the coupling effect between different frequencies can be ignored due to their inherent resonance characteristics. The sound pressures for a single 0.77 MHz line element and 2.30 MHz line element are evaluated to be 53 kPa and 73 kPa at a distance of 1 cm in water. This high performance dual-frequency PMUT line array makes some high resolution imaging methods possible based on PMUT technology, such as those of dual-frequency, total focus.



中文翻译:

元件间耦合效应低的双频压电微加工超声换能器阵列

本文提出了一种具有低串扰水平的双频压电微加工超声换能器(PMUT)线阵列,该阵列是在具有溅射压电薄膜(PZT)和硅膜片结构的绝缘体上硅(SOI)晶片上制造的。将所得到的阵列由0.77兆赫和2.30兆赫192 PMUT单元与50的最小间隙总共120 μ米。由于PZT的压电系数高,PMUT在空气中显示出高的传输灵敏度和良好的有效机电耦合系数。位移灵敏度估计为595 nm V -1和112 nm V -1在空气中的共振频率分别为0.77 MHz和2.30 MHz。为了减少振动耦合,在相邻的线元素之间设计了底部硅片中的矩形凹槽,并且阵列中的PMUT单元以未对准的方式排列。对0.77 MHz单元的模态分析表明,当以4 V驱动激励线时,相邻耦合振动从激励振动的44.5%大大降低到14.8%。pp,这证明凹槽和未对齐的排列对于降低耦合效果都是有效的。此外,结果表明,不同频率之间的耦合效应由于其固有的共振特性而可以忽略。在水中1厘米处,单个0.77 MHz线路元素和2.30 MHz线路元素的声压评估为53 kPa和73 kPa。这种高性能的双频PMUT线阵列使一些基于PMUT技术的高分辨率成像方法成为可能,例如双频全聚焦技术。

更新日期:2021-02-11
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