Deposition and evaluation of Ta2O5 piezoelectric thin film on Pt crystal film

Abstract

Tantalum pentoxide (Ta2O5) thin films were deposited on Pt(100)/Si(100) and SrRuO3(SRO)/Pt(100)/Si(100) substrates using an RF magnetron sputtering system. From the evaluated orientation and piezoelectricity of the deposited thin films, it was clarified that the Ta2O5 thin films were crystallized to λ-Ta2O5 without piezoelectricity on the Pt/Si substrates and to β-Ta2O5 with piezoelectricity on the SRO/Pt/Si substrates. The electromechanical coupling factor k t 2 of the deposited film containing β-Ta2O5 was measured to be 0.36% from the response of a high-overtone bulk acoustic resonator, whereas that of the deposited film containing λ-Ta2O5 was measured to be 0.03%. Furthermore, the enhancement of the electromechanical coupling factor of surface acoustic waves (SAWs) by adding a high-density Pt intermediate layer was clarified from the resonance property simulated by the finite element method. This enhancement was due to the distributed particle displacement of the SAWs throughout the Ta2O5 thin film.