Design and Fabrication of Aluminum Nitride Piezoelectric Micromachined Ultrasonic Transducers for Air Flow Measurements

Karuthedath, Cyril Baby; Abhilash, T. S.; Saarilahti, Jaakko; Sillanpää, Teuvo; Pensala, Tuomas

doi:10.1109/ultsym.2019.8925544

Cited by 14 publications

(6 citation statements)

References 2 publications

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“…In the structures under study, Al 1−x Sc x N (x = 0.2) was sandwiched between top electrode (TE) and bottom electrode (BE) layers. The thicknesses and sequence of the layers replicated a design used for the fabrication of piezoelectric micromachined ultrasonic transducers (pMUTs) in [19]. Al, AlSi (1%), Mo/Al, and Mo were utilized as the top electrode (TE) layers in the structures to examine the AlScN interaction with these metallization materials.…”

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confidence: 99%

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

Bespalova

Österlund

Ross

et al. 2021

J. Microelectromech. Syst.

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Scandium-alloyed aluminum nitride (AlScN) is a potential material for micro-electromechanical systems because of its unique advantages, such as strong piezoelectric effect and high thermal stability. However, issues related to its stability and interaction with other materials in multilayer systems require investigation. The formation of new phases at the interface between piezomaterial and electrode material can lead to the device failure. In this study, multilayer structures Si substrate/AlN/Ti-Mo/Al 0.8 Sc 0.2 N/top electrode (TE) were studied after annealing at a wide range of temperatures and durations. Four different TE materials (i.e. Al, AlSi (1%), Mo/Al, and Mo) were examined to determine the most reliable electrode material for the structure. The phase stability, interfacial quality, and piezoelectric response of the multilayer systems after thermal annealing were investigated. The structure with Mo TE layer was stable after annealing at 800 • C for 300 h and at 1000 • C for 100 h. None of the structures formed any new phases at the interface between the electrode layer and AlScN. The transverse piezoelectric coefficient (e 31,f) was determined for Al 0.8 Sc 0.2 N before and after annealing. The absolute value of the e 31,f was −1.39 C/m 2 for as-deposited structure and −1.67 C/m 2 for the same structure annealed for 300 h at 800 • C.

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confidence: 99%

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

Bespalova

Österlund

Ross

et al. 2021

J. Microelectromech. Syst.

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“…First, patterning the piezoelectric layer reduces the stiffness of the etched area of the membrane, increasing the displacement sensitivity and improving the transmit and receive performance of the PMUT. The dominant factors determining wafer-level uniformity in PMUTs are the membrane diameter variation, thickness variation, and stress variation of the sputtered films [17], [18]. In Cavity Silicon on Insulator (CSOI) based PMUTs, dimensional variation across the wafer is expected to be minimal, so the stress variation of the sputtered ScAlN, which is in the range of a few hundred MPa, and the Si thickness variation are the dominant factors.…”

Section: Design a Pmut Cellmentioning

confidence: 99%

Development of ScAlN PMUTs for Medical Applications

Karuthedath

Abhilash

Helistö

et al. 2023

J. Microelectromech. Syst.

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In this paper, the design, fabrication and characterization of PMUTs for medical applications are discussed. Scandium (20% Sc/(Sc+Al)) doped AlN is used as the piezoelectric material. The fabrication process for PMUTs with a patterned piezoelectric layer is developed. Single-cell and linear arrays of PMUT are fabricated and electrical, mechanical and acoustic characterization is carried out. The piezo-patterning improved the performance of PMUTs. The fabricated PMUT showed excellent chip-wafer level uniformity and yield. At resonance (5.7 MHz), the ScAlN PMUT array showed transmit sensitivity of 13 kPa/V and receive sensitivity of 1.1 V/MPa. The good transmit-receive properties and the ability to operate without bias voltage make the ScAlN PMUTs best for voltage-limited medical applications.[

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“…AlN films are already used in MEMS devices, such as thin-film bulk acoustic resonators (FBAR) [6,7], microphones [8], and piezoelectric MUTs [9,10,11]. AlN is also a promising material for inertial sensors where the higher electromechanical coupling would increase the accuracy and sensitivity of sensors.…”

Section: Abbreviationsmentioning

confidence: 99%

“…Understanding the residual stresses in thin films is important because they can affect the operation and reliability of MEMS. For example, residual stresses change the resonance frequency of pMUTs [11] and in the worst case, high stresses can result in fractures or delamination. Understanding of how stresses are generated and what are their sources can help in designing devices with improved reliability [89].…”

Section: The Mechanical Properties Of Thin Films 51 Residual Stressmentioning

confidence: 99%

Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

Österlund

Suihkonen

Ross

et al. 2020

Journal of Crystal Growth

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Preface I am also thankful to Prof. Christoph Genzel for XSA measurements and discussions on thin film mechanics, Dr. Ulla Vainio and Dr. Ville Liljeström for their help and interesting discussions on XRD. Especially, I would like to thank my fellow doctoral students and other people working in and around the Micronova cleanroom, including Ms. Heli Seppänen, Mr. Jori Lemettinen, and Ms. Elli Leppänen, to name a few.

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Design and Fabrication of Aluminum Nitride Piezoelectric Micromachined Ultrasonic Transducers for Air Flow Measurements

Cited by 14 publications

References 2 publications

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

Development of ScAlN PMUTs for Medical Applications

Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

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