Stability and residual stresses of sputtered wurtzite AlScN thin films

Elmeri Österlund (Corresponding Author), Glenn Ross, Miguel A. Caro, Mervi Paulasto-Kröckel, Andreas Hollmann, Manuela Klaus, Matthias Meixner, Christoph Genzel, Panu Koppinen, Tuomas Pensala, Agnė Žukauskaitė, Michal Trebala

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Scandium-alloying of aluminum nitride (AlScN) enhances the piezoelectric properties of the material and increases the performance of piezoelectric microelectromechanical systems (MEMS). However, this enhancement is caused by the destabilization of the wurtzite phase and so far the stability of AlScN thin films has not been sufficiently studied. Stability is especially important for piezoelectric devices because changes to the film microstructure or residual stress can lead to drastic changes in the device behavior. The stability of AlScN is investigated by annealing sputtered films and characterizing the resulting changes. It is found that the wurtzite phase of Al0.7Sc0.3N is stable at least up to 1000°C and annealing increases the crystal quality, reaching a maximum at 800°C. When annealed for more than 100 h at 1000°C, argon used in sputtering segregates into the grain boundaries and causes compressive strains and formation of rock-salt phase. Additionally, annealing at 1000∘C for 5 h reduces the average tensile stress by approximately 1 GPa.
Original languageEnglish
Article number035001
JournalPhysical Review Materials
Volume5
Issue number3
DOIs
Publication statusPublished - Mar 2021
MoE publication typeA1 Journal article-refereed

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