Anchor loss dependence on electrode materials in contour mode resonators

Abstract

This paper presents a numerical study on the impact of metal electrodes on anchor losses in contour mode resonators (CMRs) operating around 220 MHz. Finite element method (FEM) using perfectly matched layer (PML) technique is used to predict devices responses. Our simulation results show that the FEM model without electrodes gives orders of magnitude higher quality factor than its more complex counterpart that includes metals. Besides, the materials composing the resonator stack change the maximum value of Q as well as the optimal anchor dimensions at which the maximum is found. Consequently, the anchor width and length are proven to be the most influential geometrical parameters and this important finding could directly affect the resonator's design rules. On top of that, the electrode material is the key to evaluate acoustic losses and cannot be excluded from the FEM models. Based on our study, FEM numerical tools greatly benefit the prediction of the quality factor dependence achieved via geometrical design and acoustic matching between the electrodes and the active piezoelectric layer.