Micromachines (May 2022)

Growth of Highly c-Axis Oriented AlScN Films on Commercial Substrates

  • Jingxiang Su,
  • Simon Fichtner,
  • Muhammad Zubair Ghori,
  • Niklas Wolff,
  • Md. Redwanul Islam,
  • Andriy Lotnyk,
  • Dirk Kaden,
  • Florian Niekiel,
  • Lorenz Kienle,
  • Bernhard Wagner,
  • Fabian Lofink

DOI
https://doi.org/10.3390/mi13050783
Journal volume & issue
Vol. 13, no. 5
p. 783

Abstract

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In this work, we present a method for growing highly c-axis oriented aluminum scandium nitride (AlScN) thin films on (100) silicon (Si), silicon dioxide (SiO2) and epitaxial polysilicon (poly-Si) substrates using a substrate independent approach. The presented method offers great advantages in applications such as piezoelectric thin-film-based surface acoustic wave devices where a metallic seed layer cannot be used. The approach relies on a thin AlN layer to establish a wurtzite nucleation layer for the growth of w-AlScN films. Both AlScN thin film and seed layer AlN are prepared by DC reactive magnetron sputtering process where a Sc concentration of 27% is used throughout this study. The crystal quality of (0002) orientation of Al0.73Sc0.27N films on all three substrates is significantly improved by introducing a 20 nm AlN seed layer. Although AlN has a smaller capacitance than AlScN, limiting the charge stored on the electrode plates, the combined piezoelectric coefficient d33,f with 500 nm AlScN is only slightly reduced by about 4.5% in the presence of the seed layer.

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