Characterization of AlScN-based multilayer systems for piezoelectric micromachined ultrasound transducer (pMUT) fabrication

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

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)


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/Al0.8 Sc0.2N/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 (e31,f) was determined for Al0.8Sc0.2N before and after annealing. The absolute value of the e31,f was-1.39 C/m² for as-deposited structure and-1.67 C/m2 for the same structure annealed for 300 h at 800 °C. [2020-0361].
Original languageEnglish
Pages (from-to)290-298
JournalJournal of Microelectromechanical Systems
Issue number2
Publication statusPublished - 16 Mar 2021
MoE publication typeA1 Journal article-refereed


This work is part of the POSITION-II project funded by the ECSEL Joint Undertaking under grant number Ecsel-783132-Position-II-2017-IA ( The work of Kristina Bespalova was supported in part by funding from Aalto ELEC Doctoral School.


  • AlScN
  • materials reliability
  • piezoelectricity
  • sputtered thin films


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