[Back]

M. Gillinger, K. Shaposhnikov, T. Knobloch, M. Schneider, M. Kaltenbacher, U. Schmid:
"Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire";
Applied Physics Letters, 108 (2016), 231601-1 - 231601-4.

This paper investigates the performance of surface acoustic wave (SAW) devices consisting of
reactively sputter deposited scandium doped aluminum nitride (ScxAl1-xN) thin films as piezoelectric
layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the
influence of piezoelectric film thickness on the device properties, samples with thickness ranging
from 500 nm up to 3000 nm are fabricated. S21 measurements and simulations demonstrate that the
phase velocity is predominantly influenced by the mass density of the electrode material rather than
by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by
rotating the interdigital transducer structures with respect to the crystal orientation of the substrate.
The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate,
which is in excellent agreement with the difference in the anisotropic Young´s modulus of the
substrate corresponding to these directions.

This paper investigates the performance of surface acoustic wave (SAW) devices consisting of
reactively sputter deposited scandium doped aluminum nitride (ScxAl1-xN) thin films as piezoelectric
layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the
influence of piezoelectric film thickness on the device properties, samples with thickness ranging
from 500 nm up to 3000 nm are fabricated. S21 measurements and simulations demonstrate that the
phase velocity is predominantly influenced by the mass density of the electrode material rather than
by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by
rotating the interdigital transducer structures with respect to the crystal orientation of the substrate.
The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate,
which is in excellent agreement with the difference in the anisotropic Young´s modulus of the
substrate corresponding to these directions.

http://dx.doi.org/10.1063/1.4953259