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

Kristina Bespalova, Glenn Ross, Mervi Paulasto-Kröckel, Abhilash Sebastian Thanniyil, Cyril Karuthedath, Stefan Mertin, Tuomas Pensala

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


In this study, Al0.8Sc0.2N 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 languageEnglish
Title of host publicationProceedings of the IEEE International Ultrasonics Symposium, IUS 2020
Number of pages4
ISBN (Electronic)9781728154480
Publication statusPublished - 7 Sep 2020
MoE publication typeA4 Article in a conference publication
EventIEEE International Ultrasonics Symposium - Las Vegas, United States
Duration: 7 Sep 202011 Sep 2020

Publication series

NameIEEE International Ultrasonics Symposium
ISSN (Print)1948-5719
ISSN (Electronic)1948-5727


ConferenceIEEE International Ultrasonics Symposium
Abbreviated titleIUS
Country/TerritoryUnited States
CityLas Vegas
OtherVirtual conference


  • Aluminium Scandium Nitride
  • Annealing
  • PMUT
  • Thin-film deposition


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