Single electrode periodic buried IDT analysis using an original FEM/BEM numerical model

The use of buried electrodes in SAW designs on quartz has important advantages when compared with unburied metal electrodes on the surface. One important property is the suppression of waveguide modes in transducers. A second advantage is the ability to use thicker metal thereby reducing the resistive losses. A numerical model for the buried electrodes is a useful tool for optimizing the buried electrode geometry. The numerical model can be extended to include the case of raised electrodes where a given depth of non-metalized substrate has been removed by reactive ion etch (RIE). This paper describes a new numerical model that is used to simulate the electro-acoustical behavior of a single periodic buried (or partially buried) IDT. In order to take into account the buried part of the electrode, it is necessary to include in the FEM domain the buried electrode along with part of the piezoelectric substrate, and of the dielectric domain above the electrode. The dielectric and the piezoelectric semi-spaces are taken into account with boundary integral formulations while Bloch Floquet´s conditions are expressed on the lateral boundaries using an original and efficient method. P matrix parameters for a single periodic buried IDT will be shown, as well as comparisons with buried IDT experimental data.