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Chen W, Ma S, Lai X, Wang Z, Zhao H, Zha Q, Chiu Y, Jin Y. Design, Fabrication, Characterization, and Simulation of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer for Sonar Imaging Applications. MICROMACHINES 2024; 15:781. [PMID: 38930750 PMCID: PMC11205683 DOI: 10.3390/mi15060781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 06/07/2024] [Accepted: 06/09/2024] [Indexed: 06/28/2024]
Abstract
To address the requirements of sonar imaging, such as high receiving sensitivity, a wide bandwidth, and a wide receiving angle, an AlN PMUT with an optimized ratio of 0.6 for the piezoelectric layer diameter to backside cavity diameter is proposed in this paper. A sample AlN PMUT is designed and fabricated with the SOI substrate-based bulk MEMS process. The characterization test result of the sample demonstrates a -6 dB bandwidth of approximately 500 kHz and a measured receiving sensitivity per unit area of 1.37 V/μPa/mm2, which significantly surpasses the performance of previously reported PMUTs. The -6 dB horizontal angles of the AlN PMUT at 300 kHz and 500 kHz are measured as 68.30° and 54.24°, respectively. To achieve an accurate prediction of its characteristics when being packaged and assembled in a receive array, numerical simulations with the consideration of film stress are conducted. The numerical result shows a maximum deviation of ±7% in the underwater receiving sensitivity across the frequency range of 200 kHz to 1000 kHz and a deviation of about 0.33% in the peak of underwater receiving sensitivity compared to the experimental data. By such good agreement, the simulation method reveals its capability of providing theoretical foundation for enhancing the uniformity of AlN PMUTs in future studies.
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Affiliation(s)
- Wenxing Chen
- Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
| | - Shenglin Ma
- Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
| | - Xiaoyi Lai
- Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
| | - Zhizhen Wang
- Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen 361005, China
| | - Hui Zhao
- The Fifth Research Laboratory, Shanghai Marine Electronic Equipment Research Institute, Shanghai 201108, China
| | - Qiang Zha
- Nanofabrication Facility, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Yihsiang Chiu
- School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Yufeng Jin
- School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, Shenzhen 518055, China
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Wong SJZ, Roy K, Lee C, Zhu Y. Thin-Film Piezoelectric Micromachined Ultrasound Transducers in Biomedical Applications: A Review. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2024; 71:622-637. [PMID: 38635378 DOI: 10.1109/tuffc.2024.3390807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Thin-film piezoelectric micromachined ultrasound transducers (PMUTs) are an increasingly relevant and well-researched field, and their biomedical importance has been growing as the technology continues to mature. This review article briefly discusses their history in biomedical use, provides a simple explanation of their principles for newer readers, and sheds light on the materials selection for these devices. Primarily, it discusses the significant applications of PMUTs in the biomedical industry and showcases recent progress that has been made in each application. The biomedical applications covered include common historical uses of ultrasound such as ultrasound imaging, ultrasound therapy, and fluid sensing, but additionally new and upcoming applications such as drug delivery, photoacoustic imaging, thermoacoustic imaging, biometrics, and intrabody communication. By including a device comparison chart for different applications, this review aims to assist microelectromechanical systems (MEMS) designers that work with PMUTs by providing a benchmark for recent research works. Furthermore, it puts forth a discussion on the current challenges being faced by PMUTs in the biomedical field, current and likely future research trends, and opportunities for PMUT development areas, as well as sharing the opinions and predictions of the authors on the state of this technology as a whole. The review aims to be a comprehensive introduction to these topics without diving excessively deep into existing literature.
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Wang Y, Wu S, Wang W, Wu T, Li X. Piezoelectric Micromachined Ultrasonic Transducers with Micro-Hole Inter-Etch and Sealing Process on (111) Silicon Wafer. MICROMACHINES 2024; 15:482. [PMID: 38675293 PMCID: PMC11051749 DOI: 10.3390/mi15040482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/25/2024] [Accepted: 03/28/2024] [Indexed: 04/28/2024]
Abstract
Piezoelectric micromachined ultrasound transducers (PMUTs) have gained significant popularity in the field of ultrasound ranging and medical imaging owing to their small size, low power consumption, and affordability. The scar-free "MIS" (micro-hole inter-etch and sealing) process, a novel bulk-silicon manufacturing technique, has been successfully developed for the fabrication of pressure sensors, flow sensors, and accelerometers. In this study, we utilize the MIS process to fabricate cavity diaphragm structures for PMUTs, resulting in the formation of a flat cavity diaphragm structure through anisotropic etching of (111) wafers in a 70 °C tetramethylammonium hydroxide (TMAH) solution. This study investigates the corrosion characteristics of the MIS technology on (111) silicon wafers, arranges micro-pores etched on bulk silicon around the desired cavity structure in a regular pattern, and takes into consideration the distance compensation for lateral corrosion, resulting in a fully connected cavity structure closely approximating an ortho-hexagonal shape. By utilizing a sputtering process to deposit metallic molybdenum as upper and lower electrodes, as well as piezoelectric materials above the cavity structure, we have successfully fabricated aluminum nitride (AlN) piezoelectric ultrasonic transducer arrays of various sizes and structures. The final hexagonal PMUT cells of various sizes that were fabricated achieved a maximum quality factor (Q) of 251 and a displacement sensitivity of 18.49 nm/V across a range of resonant frequencies from 6.28 MHz to 11.99 MHz. This fabrication design facilitates the achievement of IC-compatible and cost-effective mass production of PMUT array devices with high resonance frequencies.
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Affiliation(s)
- Yunhao Wang
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Sheng Wu
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenjing Wang
- East China Institute of Photo-Electron IC, Bengbu 233030, China
| | - Tao Wu
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
- Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, Shanghai 201210, China
| | - Xinxin Li
- State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
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Jiang D, Zhu L, Tong S, Shen Y, Gao F, Gao F. Photoacoustic imaging plus X: a review. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:S11513. [PMID: 38156064 PMCID: PMC10753847 DOI: 10.1117/1.jbo.29.s1.s11513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 11/14/2023] [Accepted: 12/11/2023] [Indexed: 12/30/2023]
Abstract
Significance Photoacoustic (PA) imaging (PAI) represents an emerging modality within the realm of biomedical imaging technology. It seamlessly blends the wealth of optical contrast with the remarkable depth of penetration offered by ultrasound. These distinctive features of PAI hold tremendous potential for various applications, including early cancer detection, functional imaging, hybrid imaging, monitoring ablation therapy, and providing guidance during surgical procedures. The synergy between PAI and other cutting-edge technologies not only enhances its capabilities but also propels it toward broader clinical applicability. Aim The integration of PAI with advanced technology for PA signal detection, signal processing, image reconstruction, hybrid imaging, and clinical applications has significantly bolstered the capabilities of PAI. This review endeavor contributes to a deeper comprehension of how the synergy between PAI and other advanced technologies can lead to improved applications. Approach An examination of the evolving research frontiers in PAI, integrated with other advanced technologies, reveals six key categories named "PAI plus X." These categories encompass a range of topics, including but not limited to PAI plus treatment, PAI plus circuits design, PAI plus accurate positioning system, PAI plus fast scanning systems, PAI plus ultrasound sensors, PAI plus advanced laser sources, PAI plus deep learning, and PAI plus other imaging modalities. Results After conducting a comprehensive review of the existing literature and research on PAI integrated with other technologies, various proposals have emerged to advance the development of PAI plus X. These proposals aim to enhance system hardware, improve imaging quality, and address clinical challenges effectively. Conclusions The progression of innovative and sophisticated approaches within each category of PAI plus X is positioned to drive significant advancements in both the development of PAI technology and its clinical applications. Furthermore, PAI not only has the potential to integrate with the above-mentioned technologies but also to broaden its applications even further.
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Affiliation(s)
- Daohuai Jiang
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
- Fujian Normal University, College of Photonic and Electronic Engineering, Fuzhou, China
| | - Luyao Zhu
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
| | - Shangqing Tong
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
| | - Yuting Shen
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
| | - Feng Gao
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
| | - Fei Gao
- ShanghaiTech University, School of Information Science and Technology, Shanghai, China
- Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, Shanghai, China
- Shanghai Clinical Research and Trial Center, Shanghai, China
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Park JS, Jung SY, Kim DH, Park JH, Jang HW, Kim TG, Baek SH, Lee BC. Dual-frequency piezoelectric micromachined ultrasound transducer based on polarization switching in ferroelectric thin films. MICROSYSTEMS & NANOENGINEERING 2023; 9:122. [PMID: 37794984 PMCID: PMC10545730 DOI: 10.1038/s41378-023-00595-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 07/05/2023] [Accepted: 07/23/2023] [Indexed: 10/06/2023]
Abstract
Due to its additional frequency response, dual-frequency ultrasound has advantages over conventional ultrasound, which operates at a specific frequency band. Moreover, a tunable frequency from a single transducer enables sonographers to achieve ultrasound images with a large detection area and high resolution. This facilitates the availability of more advanced techniques that simultaneously require low- and high-frequency ultrasounds, such as harmonic imaging and image-guided therapy. In this study, we present a novel method for dual-frequency ultrasound generation from a ferroelectric piezoelectric micromachined ultrasound transducer (PMUT). Uniformly designed transducer arrays can be used for both deep low-resolution imaging and shallow high-resolution imaging. To switch the ultrasound frequency, the only requirement is to tune a DC bias to control the polarization state of the ferroelectric film. Flextensional vibration of the PMUT membrane strongly depends on the polarization state, producing low- and high-frequency ultrasounds from a single excitation frequency. This strategy for dual-frequency ultrasounds meets the requirement for either multielectrode configurations or heterodesigned elements, which are integrated into an array. Consequently, this technique significantly reduces the design complexity of transducer arrays and their associated driving circuits.
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Affiliation(s)
- Jin Soo Park
- Bionics Research Center, Korea Institute of Science and Technology, Seoul, 02792 Republic of Korea
- Department of Electrical Engineering, Korea University, Seoul, 02841 Republic of Korea
| | - Soo Young Jung
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 02792 Republic of Korea
- Department of Material Science and Engineering, Seoul National University, Seoul, 08826 Republic of Korea
| | - Dong Hun Kim
- Bionics Research Center, Korea Institute of Science and Technology, Seoul, 02792 Republic of Korea
| | - Jung Ho Park
- Department of Electrical Engineering, Korea University, Seoul, 02841 Republic of Korea
| | - Ho Won Jang
- Department of Material Science and Engineering, Seoul National University, Seoul, 08826 Republic of Korea
| | - Tae Geun Kim
- Department of Electrical Engineering, Korea University, Seoul, 02841 Republic of Korea
| | - Seung-Hyub Baek
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 02792 Republic of Korea
| | - Byung Chul Lee
- Bionics Research Center, Korea Institute of Science and Technology, Seoul, 02792 Republic of Korea
- Division of Bio-Medical Science and Technology, KIST School, University of Science and Technology (UST), Seoul, 02792 Republic of Korea
- KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, 02447 Republic of Korea
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Roy K, Lee JEY, Lee C. Thin-film PMUTs: a review of over 40 years of research. MICROSYSTEMS & NANOENGINEERING 2023; 9:95. [PMID: 37484500 PMCID: PMC10359338 DOI: 10.1038/s41378-023-00555-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 04/19/2023] [Accepted: 05/10/2023] [Indexed: 07/25/2023]
Abstract
Thin-film PMUTs have been important research topics among microultrasound experts, and a concise review on their research progress is reported herein. Through rigorous surveying, scrutinization, and perception, it has been determined that the work in this field began nearly 44 years ago with the primitive development of functional piezoelectric thin-film materials. To date, there are three major companies commercializing thin-film PMUTs on a bulk scale. This commercialization illustrates the extensive contributions made by more than 70 different centers, research institutes, and agencies across 4 different continents regarding the vast development of these devices' design, manufacturing, and function. This review covers these important contributions in a short yet comprehensive manner; in particular, this paper educates readers about the global PMUT outlook, their governing design principles, their manufacturing methods, nonconventional yet useful PMUT designs, and category-wise applications. Crucial comparison charts of thin-film piezoelectric material used in PMUTs, and their categorically targeted applications are depicted and discussed to enlighten any MEMS designer who plans to work with PMUTs. Moreover, each relevant section features clear future predictions based on the author's past knowledge and expertise in this field of research and on the findings of a careful literature survey. In short, this review is a one-stop time-efficient guide for anyone interested in learning about these small devices.
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Affiliation(s)
- Kaustav Roy
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117583 Singapore
- Center for Intelligent Sensor and MEMS (CISM), National University of Singapore, Singapore, 117608 Singapore
| | | | - Chengkuo Lee
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117583 Singapore
- Center for Intelligent Sensor and MEMS (CISM), National University of Singapore, Singapore, 117608 Singapore
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Joshi SV, Sadeghpour S, Kraft M. Polyimide-On-Silicon 2D Piezoelectric Micromachined Ultrasound Transducer (PMUT) Array. SENSORS (BASEL, SWITZERLAND) 2023; 23:4826. [PMID: 37430741 DOI: 10.3390/s23104826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 07/12/2023]
Abstract
This paper presents a fully addressable 8 × 8 two-dimensional (2D) rigid piezoelectric micromachined ultrasonic transducer (PMUT) array. The PMUTs were fabricated on a standard silicon wafer, resulting in a low-cost solution for ultrasound imaging. A polyimide layer is used as the passive layer in the PMUT membranes on top of the active piezoelectric layer. The PMUT membranes are realized by backside deep reactive ion etching (DRIE) with an oxide etch stop. The polyimide passive layer enables high resonance frequencies that can be easily tuned by controlling the thickness of the polyimide. The fabricated PMUT with 6 µm polyimide thickness showed a 3.2 MHz in-air frequency with a 3 nm/V sensitivity. The PMUT has shown an effective coupling coefficient of 14% as calculated from the impedance analysis. An approximately 1% interelement crosstalk between the PMUT elements in one array is observed, which is at least a five-fold reduction compared to the state of the art. A pressure response of 40 Pa/V at 5 mm was measured underwater using a hydrophone while exciting a single PMUT element. A single-pulse response captured using the hydrophone suggested a 70% -6 dB fractional bandwidth for the 1.7 MHz center frequency. The demonstrated results have the potential to enable imaging and sensing applications in shallow-depth regions, subject to some optimization.
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Affiliation(s)
- Sanjog Vilas Joshi
- Department of Electrical Engineering (ESAT-MNS), KU Leuven, 3000 Leuven, Belgium
| | - Sina Sadeghpour
- Department of Electrical Engineering (ESAT-MNS), KU Leuven, 3000 Leuven, Belgium
| | - Michael Kraft
- Department of Electrical Engineering (ESAT-MNS), KU Leuven, 3000 Leuven, Belgium
- Leuven Institute for Micro- and Nanoscale Integration (LIMNI), KU Leuven, 3000 Leuven, Belgium
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Pan J, Bai C, Zheng Q, Xie H. Review of Piezoelectric Micromachined Ultrasonic Transducers for Rangefinders. MICROMACHINES 2023; 14:374. [PMID: 36838074 PMCID: PMC9961946 DOI: 10.3390/mi14020374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/21/2023] [Accepted: 01/30/2023] [Indexed: 06/18/2023]
Abstract
Piezoelectric micromachined ultrasonic transducer (pMUT) rangefinders have been rapidly developed in the last decade. With high output pressure to enable long-range detection and low power consumption (16 μW for over 1 m range detection has been reported), pMUT rangefinders have drawn extensive attention to mobile range-finding. pMUT rangefinders with different strategies to enhance range-finding performance have been developed, including the utilization of pMUT arrays, advanced device structures, and novel piezoelectric materials, and the improvements of range-finding methods. This work briefly introduces the working principle of pMUT rangefinders and then provides an extensive overview of recent advancements that improve the performance of pMUT rangefinders, including advanced pMUT devices and range-finding methods used in pMUT rangefinder systems. Finally, several derivative systems of pMUT rangefinders enabling pMUT rangefinders for broader applications are presented.
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Affiliation(s)
- Jiong Pan
- School of Integrated Circuits and Electronics, Beijing Institute of Technology (BIT), Beijing 100081, China
| | - Chenyu Bai
- School of Integrated Circuits and Electronics, Beijing Institute of Technology (BIT), Beijing 100081, China
| | - Qincheng Zheng
- School of Integrated Circuits and Electronics, Beijing Institute of Technology (BIT), Beijing 100081, China
| | - Huikai Xie
- School of Integrated Circuits and Electronics, Beijing Institute of Technology (BIT), Beijing 100081, China
- BIT Chongqing Center for Microelectronics and Microsystems, Chongqing 400030, China
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