Li Xiaobao, Lyu Haochen, Safari Ahmad, Zhang Songsong
School of Microelectronics, Shanghai University, Shanghai 200444, China.
Shanghai Melon Technology Company Ltd., Shanghai 201899, China.
Micromachines (Basel). 2023 Dec 29;15(1):72. doi: 10.3390/mi15010072.
This paper presents a novel piezoelectric micromachined ultrasonic transducer (PMUT) with theoretical simulation, fabrication, and testing. Conventional methods using a PCB or an external horn to adjust the PMUT acoustic field angle are limited by the need for transducer size. To address this limitation, the stepped-tube (expanded tube) backside cavity PMUT has been proposed. The stepped-tube PMUT and the tube PMUT devices have the same membrane structure, and the acoustic impedance matching of the PMUT is optimized by modifying the boundary conditions of the back cavity structure. The acoustic comparison experiments show that the average output sound pressure of the stepped-tube backside cavity PMUT has increased by 17%, the half-power-beam-width (θ) has been reduced from 55° to 30° with a reduction of 45%, and the side lobe level signal is reduced from 147 mV to 66 mV. In addition, this work is fabricated on an eight-inch wafer. The process is compatible with standard complementary metal oxide semiconductor (CMOS), conditions are stable, and the cost is controllable, plus it facilitates the batch process. These conclusions suggest that the stepped-tube backside cavity PMUT will bring new, effective, and reliable solutions to ranging applications.
本文介绍了一种新型的压电微机械超声换能器（PMUT），并进行了理论模拟、制作和测试。使用印刷电路板（PCB）或外部变幅杆来调整PMUT声场角度的传统方法受到换能器尺寸要求的限制。为了解决这一限制，提出了阶梯管（扩径管）背腔式PMUT。阶梯管PMUT和管PMUT器件具有相同的膜结构，通过修改背腔结构的边界条件来优化PMUT的声阻抗匹配。声学对比实验表明，阶梯管背腔式PMUT的平均输出声压提高了17%，半功率波束宽度（θ）从55°减小到30°，减小了45%，旁瓣电平信号从147 mV降低到66 mV。此外，这项工作是在八英寸晶圆上制作的。该工艺与标准互补金属氧化物半导体（CMOS）兼容，条件稳定，成本可控，并且便于批量生产。这些结论表明，阶梯管背腔式PMUT将为测距应用带来新的、有效且可靠的解决方案。
