Silicon-On-Nothing ScAlN pMUTs

Choong, David Sze Wai; Chen, Ssu-Han; Goh, Duan Jian; Liu, Jihang; Ghosh, Sagnik; Koh, Youngil; Sharma, Jaibir; Merugu, Srinivas; Quaglia, Fabio; Ferrera, Marco; Savoia, Alessandro Stuart; Ng, Eldwin J.

doi:10.1109/ius52206.2021.9593461

Cited by 15 publications

(3 citation statements)

References 7 publications

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“…AlScN is an interesting material with outstanding piezoelectric, ferroelectric, pyroelectric, and optomechanical properties. Besides the RF communication and memory applications which are discussed extensively in this article, AlScN for sensors, 102 actuators, 103 photonics, 104 and power electronics 105 applications is also undergoing active research. Coupling multiple physics in one platform could uncover new device functions and applications in the future.…”

Section: Discussionmentioning

confidence: 99%

Scandium-Doped Aluminum Nitride for Acoustic Wave Resonators, Filters, and Ferroelectric Memory Applications

Chen

Liu

et al. 2022

ACS Appl. Electron. Mater.

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Scandium-doped aluminum nitride (AlScN) has generated great research interest owing to its unique properties. The wurtzite-structure AlScN is compatible with the complementary metal oxide semiconductor (CMOS) process and has improved piezoelectricity compared with undoped aluminum nitride (AlN), making it a promising candidate to be used for next-generation radio frequency (RF) microelectromechanical system (MEMS) building blocks. Additionally, the ferroelectricity observed in AlScN can be potentially applied to ferroelectric memory devices. In this spotlight article, we provide a brief introduction of AlScN and summarize the recent progress of AlScN-based applications, including RF acoustic wave resonators, filters, and ferroelectric memory devices. Finally, the current challenges as well as the future opportunities of AlScN materials and related applications are discussed.

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Section: Discussionmentioning

confidence: 99%

Scandium-Doped Aluminum Nitride for Acoustic Wave Resonators, Filters, and Ferroelectric Memory Applications

Chen

Liu

et al. 2022

ACS Appl. Electron. Mater.

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“…However, the devices are not robust in operating in a fluidic environment as both sides of the membranes are immersed. Additionally, the PMUT-prepared silicon-on-nothing (SON) process [19] has been proposed, which leverages the high-temperature migration of trenches to form a monocrystalline silicon film on buried cavities.…”

Section: Introductionmentioning

confidence: 99%

Piezoelectric Micromachined Ultrasonic Transducers with Micro-Hole Inter-Etch and Sealing Process on (111) Silicon Wafer

Wang,

Wu,

Wang

et al. 2024

Micromachines

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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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“…In the field of materials and processes, recently published articles [7][8][9][10][11] provide an exhaustive review of all the technological developments to date. The most widely used piezoelectric materials are the following: ZnO [4,12,13]; AlN, for which scandium doping [14,15] has enabled the electroacoustic performances to be three times higher; and PZT material, the first works on which were published by [6,[16][17][18] and, more recently, by Savoia et al [19]. Thin-film PZT is usually deposited either by a sol-gel process [20] or a sputtering technique [20].…”

Section: Introductionmentioning

confidence: 99%

Modeling a Fluid-Coupled Single Piezoelectric Micromachined Ultrasonic Transducer Using the Finite Difference Method

Goepfert,

Boulmé,

Levassort

et al. 2023

Micromachines

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A complete model was developed to simulate the behavior of a circular clamped axisymmetric fluid-coupled Piezoelectric Micromachined Ultrasonic Transducer (PMUT). Combining Finite Difference and Boundary Element Matrix (FD-BEM), this model is based on the discretization of the partial differential equation used to translate the mechanical behavior of a PMUT. In the model, both the axial and the transverse displacements are preserved in the equation of motion and used to properly define the neutral line position. To introduce fluid coupling, a Green’s function dedicated to axisymmetric circular radiating sources is employed. The resolution of the behavioral equations is used to establish the equivalent electroacoustic circuit of a PMUT that preserves the average particular velocity, the mechanical power, and the acoustic power. Particular consideration is given to verifying the validity of certain assumptions that are usually made across various steps of previously reported analytical models. In this framework, the advantages of the membrane discretization performed in the FD-BEM model are highlighted through accurate simulations of the first vibration mode and especially the cutoff frequency that many other models do not predict. This high cutoff frequency corresponds to cases where the spatial average velocity of the plate is null and is of great importance for PMUT design because it defines the upper limit above which the device is considered to be mechanically blocked. These modeling results are compared with electrical and dynamic membrane displacement measurements of AlN-based (500 nm thick) PMUTs in air and fluid. The first resonance frequency confrontation showed a maximum relative error of 1.13% between the FD model and Finite Element Method (FEM). Moreover, the model perfectly predicts displacement amplitudes when PMUT vibrates in a fluid, with less than 5% relative error. Displacement amplitudes of 16 nm and 20 nm were measured for PMUT with 340 µm and 275 µm diameters, respectively. This complete PMUT model using the FD-BEM approach is shown to be very efficient in terms of computation time and accuracy.

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Silicon-On-Nothing ScAlN pMUTs

Cited by 15 publications

References 7 publications

Scandium-Doped Aluminum Nitride for Acoustic Wave Resonators, Filters, and Ferroelectric Memory Applications

Scandium-Doped Aluminum Nitride for Acoustic Wave Resonators, Filters, and Ferroelectric Memory Applications

Piezoelectric Micromachined Ultrasonic Transducers with Micro-Hole Inter-Etch and Sealing Process on (111) Silicon Wafer

Modeling a Fluid-Coupled Single Piezoelectric Micromachined Ultrasonic Transducer Using the Finite Difference Method

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