Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration

Kristina Bespalova; Glenn Ross; Mervi Paulasto-Kröckel; T.S. Abhilash; Cyril Karuthedath; Stefan Mertin; Tuomas Pensala

doi:10.1109/IUS46767.2020.9251496

Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration

Kristina Bespalova, Glenn Ross, Mervi Paulasto-Kröckel, T.S. Abhilash, Cyril Karuthedath, Stefan Mertin, Tuomas Pensala

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific

Abstract

In this study, Al 0.8 Sc 0.2 N multilayer structures phase stability, interfacial quality, and piezoelectric response were tested before and after annealing in wide range of temperatures and times. The thicknesses and sequence of the layers in the structures are a replica of the design used for the fabrication of piezoelectric micromachined ultrasonic transducers (pMUTs). Al, AlSi (1%), Al/Mo, and Mo have been assessed to choose the most reliable top electrode (TE) material for the structures. The piezoresponse of the structure was estimated by measuring the deflection of piezocantilevers as a function of voltage applied over the film. Membrane deflection at resonance frequency for AlScN- and AlN-based pMUTs was simulated in COMSOL Multiphysics. It is found that the structure with Mo TE layer is stable after annealing at 800°C for 300 h and at 1000 °C for 100 h. None of the structures formed any phases at the interface between the electrode layer and AlScN. Membrane deflection for structures with AlScN as piezolayer is almost three times higher as compared to structures with AlN as piezolayer. Moreover, the pMUT membrane deflection increases after annealing of the structure.

Original language	English
Title of host publication	IUS 2020 - International Ultrasonics Symposium, Proceedings
Publisher	IEEE Institute of Electrical and Electronic Engineers
Number of pages	4
ISBN (Electronic)	978-1-7281-5448-0
ISBN (Print)	978-1-7281-5449-7
DOIs	https://doi.org/10.1109/IUS46767.2020.9251496
Publication status	Published - 7 Sep 2020
MoE publication type	B3 Non-refereed article in conference proceedings
Event	IEEE International Ultrasonics Symposium, IUS - Las Vegas, United States Duration: 7 Sep 2020 → 11 Sep 2020

Conference

Conference	IEEE International Ultrasonics Symposium, IUS
Country	United States
City	Las Vegas
Period	7/09/20 → 11/09/20

Keywords

Aluminium Scandium Nitride
pMUT
thin-film deposition
annealing

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10.1109/IUS46767.2020.9251496

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@inproceedings{3e7f4008adc84999aee062d3d90a8792,

title = "Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration",

abstract = "In this study, Al 0.8 Sc 0.2 N multilayer structures phase stability, interfacial quality, and piezoelectric response were tested before and after annealing in wide range of temperatures and times. The thicknesses and sequence of the layers in the structures are a replica of the design used for the fabrication of piezoelectric micromachined ultrasonic transducers (pMUTs). Al, AlSi (1%), Al/Mo, and Mo have been assessed to choose the most reliable top electrode (TE) material for the structures. The piezoresponse of the structure was estimated by measuring the deflection of piezocantilevers as a function of voltage applied over the film. Membrane deflection at resonance frequency for AlScN- and AlN-based pMUTs was simulated in COMSOL Multiphysics. It is found that the structure with Mo TE layer is stable after annealing at 800°C for 300 h and at 1000 °C for 100 h. None of the structures formed any phases at the interface between the electrode layer and AlScN. Membrane deflection for structures with AlScN as piezolayer is almost three times higher as compared to structures with AlN as piezolayer. Moreover, the pMUT membrane deflection increases after annealing of the structure.",

keywords = "Aluminium Scandium Nitride, pMUT, thin-film deposition, annealing",

author = "Kristina Bespalova and Glenn Ross and Mervi Paulasto-Kr{\"o}ckel and T.S. Abhilash and Cyril Karuthedath and Stefan Mertin and Tuomas Pensala",

note = "Funding Information: ACKNOWLEDGMENT This work is part of the POSITION-II project funded by the ECSEL Joint Undertaking under grant number Ecsel-783132-Position-II-2017-IA (www.position-2.eu). Funding Information: Ms. Bespalova appreciates the funding from Aalto ELEC Doctoral School. M.Sc. Elmeri {\"O}sterlund is acknowledged for his help with piezocantilever fabrication and XRD measurements. Publisher Copyright: {\textcopyright} 2020 IEEE. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.; IEEE International Ultrasonics Symposium, IUS ; Conference date: 07-09-2020 Through 11-09-2020",

year = "2020",

month = sep,

day = "7",

doi = "10.1109/IUS46767.2020.9251496",

language = "English",

isbn = "978-1-7281-5449-7",

booktitle = "IUS 2020 - International Ultrasonics Symposium, Proceedings",

publisher = "IEEE Institute of Electrical and Electronic Engineers",

address = "United States",

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Bespalova, K, Ross, G, Paulasto-Kröckel, M, Abhilash, TS , Karuthedath, C, Mertin, S & Pensala, T 2020, Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration. in IUS 2020 - International Ultrasonics Symposium, Proceedings. IEEE Institute of Electrical and Electronic Engineers, IEEE International Ultrasonics Symposium, IUS, Las Vegas, United States, 7/09/20. https://doi.org/10.1109/IUS46767.2020.9251496

Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration. / Bespalova, Kristina; Ross, Glenn; Paulasto-Kröckel, Mervi; Abhilash, T.S.; Karuthedath, Cyril; Mertin, Stefan; Pensala, Tuomas.

IUS 2020 - International Ultrasonics Symposium, Proceedings. IEEE Institute of Electrical and Electronic Engineers, 2020.

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific

TY - GEN

T1 - Temperature Stability of Electrode/AlScN Multilayer Systems for pMUT Process Integration

AU - Bespalova, Kristina

AU - Ross, Glenn

AU - Paulasto-Kröckel, Mervi

AU - Abhilash, T.S.

AU - Karuthedath, Cyril

AU - Mertin, Stefan

AU - Pensala, Tuomas

N1 - Funding Information: ACKNOWLEDGMENT This work is part of the POSITION-II project funded by the ECSEL Joint Undertaking under grant number Ecsel-783132-Position-II-2017-IA (www.position-2.eu). Funding Information: Ms. Bespalova appreciates the funding from Aalto ELEC Doctoral School. M.Sc. Elmeri Österlund is acknowledged for his help with piezocantilever fabrication and XRD measurements. Publisher Copyright: © 2020 IEEE. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/9/7

Y1 - 2020/9/7

N2 - In this study, Al 0.8 Sc 0.2 N multilayer structures phase stability, interfacial quality, and piezoelectric response were tested before and after annealing in wide range of temperatures and times. The thicknesses and sequence of the layers in the structures are a replica of the design used for the fabrication of piezoelectric micromachined ultrasonic transducers (pMUTs). Al, AlSi (1%), Al/Mo, and Mo have been assessed to choose the most reliable top electrode (TE) material for the structures. The piezoresponse of the structure was estimated by measuring the deflection of piezocantilevers as a function of voltage applied over the film. Membrane deflection at resonance frequency for AlScN- and AlN-based pMUTs was simulated in COMSOL Multiphysics. It is found that the structure with Mo TE layer is stable after annealing at 800°C for 300 h and at 1000 °C for 100 h. None of the structures formed any phases at the interface between the electrode layer and AlScN. Membrane deflection for structures with AlScN as piezolayer is almost three times higher as compared to structures with AlN as piezolayer. Moreover, the pMUT membrane deflection increases after annealing of the structure.

AB - In this study, Al 0.8 Sc 0.2 N multilayer structures phase stability, interfacial quality, and piezoelectric response were tested before and after annealing in wide range of temperatures and times. The thicknesses and sequence of the layers in the structures are a replica of the design used for the fabrication of piezoelectric micromachined ultrasonic transducers (pMUTs). Al, AlSi (1%), Al/Mo, and Mo have been assessed to choose the most reliable top electrode (TE) material for the structures. The piezoresponse of the structure was estimated by measuring the deflection of piezocantilevers as a function of voltage applied over the film. Membrane deflection at resonance frequency for AlScN- and AlN-based pMUTs was simulated in COMSOL Multiphysics. It is found that the structure with Mo TE layer is stable after annealing at 800°C for 300 h and at 1000 °C for 100 h. None of the structures formed any phases at the interface between the electrode layer and AlScN. Membrane deflection for structures with AlScN as piezolayer is almost three times higher as compared to structures with AlN as piezolayer. Moreover, the pMUT membrane deflection increases after annealing of the structure.

KW - Aluminium Scandium Nitride

KW - pMUT

KW - thin-film deposition

KW - annealing

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U2 - 10.1109/IUS46767.2020.9251496

DO - 10.1109/IUS46767.2020.9251496

M3 - Conference article in proceedings

SN - 978-1-7281-5449-7

BT - IUS 2020 - International Ultrasonics Symposium, Proceedings

PB - IEEE Institute of Electrical and Electronic Engineers

T2 - IEEE International Ultrasonics Symposium, IUS

Y2 - 7 September 2020 through 11 September 2020

ER -