A Piezoelectric Micromachined Ultrasonic Transducer Using Thin-Film Lithium Niobate

Lu, Ruochen; Breen, Michael; Hassanien, Ahmed E.; Yang, Yansong; Gong, Songbin

doi:10.1109/jmems.2020.3026547

Cited by 17 publications

(11 citation statements)

References 23 publications

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“…Hence, piezoelectric materials play a primary role in the performance of PMUT devices. Among the most studied piezoelectric materials, such as PZT [ 6 , 15 ], AlN [ 5 ], AlScN [ 4 ], ZnO [ 16 ], PVDF [ 17 ], and LiNbO3 [ 9 , 18 ], AlN is a competitive candidate due to the excellent compatibility between CMOS and MEMS micromachining. To further improve the performance of the transmit and receive sensitivity of a PMUT, the structure of the PMUT must be optimized.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Zhang

Geng

et al. 2023

Micromachines

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Due to their excellent capabilities to generate and sense ultrasound signals in an efficient and well-controlled way at the microscale, piezoelectric micromechanical ultrasonic transducers (PMUTs) are being widely used in specific systems, such as medical imaging, biometric identification, and acoustic wireless communication systems. The ongoing demand for high-performance and adjustable PMUTs has inspired the idea of manipulating PMUTs by voltage. Here, PMUTs based on AlN thin films protected by a SiO2 layer of 200 nm were fabricated using a standard MEMS process with a resonant frequency of 505.94 kHz, a −6 dB bandwidth (BW) of 6.59 kHz, and an electromechanical coupling coefficient of 0.97%. A modification of 4.08 kHz for the resonant frequency and a bandwidth enlargement of 60.2% could be obtained when a DC bias voltage of −30 to 30 V was applied, corresponding to a maximum resonant frequency sensitivity of 83 Hz/V, which was attributed to the stress on the surface of the piezoelectric film induced by the external DC bias. These findings provide the possibility of receiving ultrasonic signals within a wider frequency range, which will play an important role in underwater three-dimensional imaging and nondestructive testing.

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Section: Introductionmentioning

confidence: 99%

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Zhang

Geng

et al. 2023

Micromachines

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“…In contrast, flexural vibration mode pMUTs are easier to be fabricated into large arrays. Typical piezoelectric thin films, such as PZT, AlN, and transferred LiNbO 3 thin films, have been applied to fabricate flexural vibration mode pMUTs 32 – 34 . However, their applications in endoscopic PAI are still in an early stage, facing the challenges of limited film thickness and insufficient piezoelectric response.…”

Section: Introductionmentioning

confidence: 99%

Thin ceramic PZT dual- and multi-frequency pMUT arrays for photoacoustic imaging

et al. 2022

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Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging (PAI) systems to achieve high spatial resolution and large imaging depth for biomedical applications. In this article, we report on the development of ceramic thin-film PZT-based dual- and multi-frequency piezoelectric micromachined ultrasonic transducer (pMUT) arrays and the demonstration of their PAI applications. With chips sized 3.5 mm in length or 10 mm in diameter, square and ring-shaped pMUT arrays incorporating as many as 2520 pMUT elements and multiple frequencies ranging from 1 MHz to 8 MHz were developed for endoscopic PAI applications. Thin ceramic PZT with a thickness of 9 μm was obtained by wafer bonding and chemical mechanical polishing (CMP) techniques and employed as the piezoelectric layer of the pMUT arrays, whose piezoelectric constant d31 was measured to be as high as 140 pm/V. Benefiting from this high piezoelectric constant, the fabricated pMUT arrays exhibited high electromechanical coupling coefficients and large vibration displacements. In addition to electrical, mechanical, and acoustic characterization, PAI experiments with pencil leads embedded into an agar phantom were conducted with the fabricated dual- and multi-frequency pMUT arrays. Photoacoustic signals were successfully detected by pMUT elements with different frequencies and used to reconstruct single and fused photoacoustic images, which clearly demonstrated the advantages of using dual- and multi-frequency pMUT arrays to provide comprehensive photoacoustic images with high spatial resolution and large signal-to-noise ratio simultaneously.

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“…The method is based on discretizing partial differential equations (PDEs) into a system of linear algebraic equations, which solve complicated multi-physics-coupled models while complying with the original constitutive laws and governing equations. By setting up a 2-D axisymmetric or 3-D model, one can calculate electro-mechanical-acoustical properties of pMUT accurately [ 15 , 16 ]. The studies on pMUT are making progress on proposing new structures and doing structure optimization.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity—Bandwidth Optimization of PMUT with Acoustical Matching Using Finite Element Method

Xü

Wang

et al. 2022

Sensors

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A new model in finite element method to study round-trip performance of piezoelectric micromachined ultrasonic transducers (pMUTs) is established. Most studies on the performance of pMUT are based only on the transmission sensibility, but the reception capacity is as much important as the transmission one, and is quite different from this latter. In this work, the round-trip sensitivity of pMUT is defined as the product of the frequency response of transmitted far field pressure to source voltage excitation and that of reception output to return wave pressure. Based on this sensitivity characteristic, firstly, a multi-parameter optimization for a cavity pMUT is performed using the sensitivity-bandwidth product parameter SBW as criterion. The radii of the electrode and the piezoelectric layer, the thicknesses of the piezoelectric layer and the vibration diaphragm are adjusted to maximize the performance. Secondly, an acoustic matching method is proposed and applied to pMUTs for the first time. As a result, the round-trip sensitivity can be evaluated and the pulse-echo response of wide-band excitation can be simulated, giving the most quantitative and intuitive feedback for pMUT design. The optimization enhances the sensitivity-bandwidth product by 52% when the top electrode and piezoelectric layer are both etched to 75% radius of the cavity beneath; the introduction of an acoustic matching layer shows significant bandwidth expansion in both the transmitting and receiving process.

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A Piezoelectric Micromachined Ultrasonic Transducer Using Thin-Film Lithium Niobate

Cited by 17 publications

References 23 publications

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Fabrication and DC-Bias Manipulation Frequency Characteristics of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer

Thin ceramic PZT dual- and multi-frequency pMUT arrays for photoacoustic imaging

Sensitivity—Bandwidth Optimization of PMUT with Acoustical Matching Using Finite Element Method

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