Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-02-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
Series
Journal of Crystal Growth, Volume 531
Abstract
Metalorganic chemical vapor deposited (MOCVD) aluminum nitride (AlN) on vertical sidewalls can be used to implement piezoelectric in-plane actuation and sensing in microelectromechanical system (MEMS) sensors. The AlN films should optimally cover conformally the sidewalls and have good crystal quality with c-axis oriented microstructure for optimal piezoelectric properties. Previous MOCVD AlN research has focused on using AlN as a buffer layer for other III-nitrides and so far, AlN growth has not been studied on large vertical surfaces. In this study, AlN thin films were grown using MOCVD on vertical sidewalls of fabricated templates and the conformality and crystal quality was characterized. The growth template fabrication was optimized with respect to surface roughness, the conformal coverage was analyzed by measuring the thickness profiles of the films, and the crystal quality was investigated using in-plane XRD and TEM. The AlN films have good crystal quality (FWHM 1.70°–3.44°) and c-axis orientation on vertical Si(1 1 1) sidewalls. However, the thicknesses of the films reduce approximately at a rate of 0.8–1.2 nm/μm down the sidewall. Lowering the reactor pressure improved the conformal coverage while changing the growth mode from columnar to step-flow, which also improved the film morphology.
Description
Keywords
Metalorganic chemical vapor deposition, Aluminum nitride, Nitrides, Piezoelectric materials
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Citation
Österlund , E , Suihkonen , S , Ross , G , Torkkeli , A , Kuisma , H & Paulasto-Kröckel , M 2020 , ' Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces ' , Journal of Crystal Growth , vol. 531 , 125345 . https://doi.org/10.1016/j.jcrysgro.2019.125345