Theoretical study of lamb wave mode S0 of AlN membrane bridges SiO2

The propagation of the S0 Lamb mode in AlN membrane combined with continuous and structured SiO2 thin films is theoretically studied with respect of the materials geometrical parameters and electrical boundaries conditions. A comparison is made in terms of the phase velocity, electromechanical coupling coefficient and temperature coefficients of frequency (TCF) between the studied structures. The results show that an optimal choose of the geometrical parameters of the structure based on SiO2 ribbons can provide a better compromise between low TCF value and resonator performances. The structure also enables an optimal configuration where the SiO2 bridges can be used as a passivation layer for IDTs which consequently is very suitable for sensors applications in harsh environments.