Accurate characterization of SiO2 thin films using surface acoustic waves

We have investigated the acoustic properties of silicon dioxide thin films. Therefore, we determined the phase velocity dispersion of LiNbO₃ substrate covered with SiO₂ deposited by a plasma enhanced chemical vapor deposition and a physical vapor deposition (PVD) process using differential delay lines and laser ultrasonic method. The density p and the elastic constants (c₁₁ and c₄₄) can be extracted by fitting corresponding finite element simulations to the phase velocities within an accuracy of at least ±4%. Additionally, we propose two methods to improve the accuracy of the phase velocity determination by dealing with film thickness variation of the PVD process.