Deposition and Evaluation of Highly Crystallized Ta2O5 Piezoelectric Thin Film on Pt Crystal Film

Tantalum pentoxide (Ta
2
O
5
) thin films were deposited on Pt(100)/Si(100) and SrRuO
3
(SRO)/Pt(100)/Si(100) substrates using an RF magnetron sputtering system at a low deposition rate
$(\sim 0.4\mu \mathrm{m}/\mathrm{h})$
. From the evaluated orientation and piezoelectricity of the deposited thin films, it was clarified that the Ta
2
O
5
thin films were crystallized to
$\beta$
-Ta
2
O
5
with piezoelectricity on both substrates. Furthermore, the crystallinity improved with increasing film thickness. The electromechanical coupling factor
$k_{\mathrm{t}^{2}}$
values of the Ta
2
O
5
/Pt/Si and Ta
2
O
5
/SRO/Pt/Si samples were measured to be 0.96 and 1.44%, respectively, from the response of a high-overtone bulk acoustic resonator. The larger
$k_{\mathrm{t}^{2}}$
with improved crystallinity suggests the deposition of a film mainly composed of
$\beta$
-Ta
2
O
5
.