Validity evaluation of ScxAl1−xN material constants based on SAW characteristics

This paper is aimed at examining the validity of material constants reported for the use in surface acoustic wave (SAW) device simulations. At first, based on the full set of material constants calculated by the first principle, bulk acoustic wave (BAW) velocities are calculated for Sc
x
Al
1−x
N and compared with published experimental results. Then, the effects of Sc
x
Al
1−x
N material constants with different Sc contents on acoustic characteristics are calculated and the influences of shear vibrations on SAW characteristics are recognized. Then series of SAW devices are fabricated on Sc
x
Al
1−x
N film/Si substrate structure with various Cu and ScAlN thicknesses h
Cu
and h
ScAlN
, respectively, and measured variations of phase velocity V and effective electromechanical coupling factor K
e
²
with these parameters are compared with the calculation. The fairly well agreed results indicate a reliable set of Sc
x
Al
1−x
N material constants for SAW device simulations.