Investigation of modified Lamé mode resonator with high coupling coefficient

Abstract

This paper presents a modified Lamé-mode resonator (MLMR) with a high, effective electromechanical coupling coefficient (Keff2). With trapezoidal grooves introduced by etching the superficial piezoelectric material between interdigitated electrodes (IDTs), the MLMR can remarkably improve Keff2, eliminate spurious modes, and reduce the internal stress of piezoelectric material. The Lamé mode resonator (LMR) with four different electrode configurations is investigated by using finite element method simulation first; then, the impact of the groove's vertical (h) and horizontal (θ) size on Keff2 and spurious modes of MLMRs is theoretically analyzed and optimized. It is noted that all the modified structures can improve Keff2 except the IDT-Ground structure. This work demonstrates a simulated Keff2 as high as 10.47% in the modified IDT-Floating structure, and 10.73% in the modified IDT-IDT structure, which is the highest ever reported in S0 mode AlN LMR. The MLMR shows great prospect for fabricating broad bandwidth filters.

Effective electromechanical coupling coefficient ( keff2 ) enhancement of a Lamb wave resonator with trapezoid grooves configuration

“…24) In addition, our group has investigated the relationship between the k , eff 2 spurious modes and the shape of the grooves by finite element method (FEM) simulations. 25) It has been estimated that the grooves can improve the k eff 2 in the S 0 mode LWR. In this paper, we take a further step to investigate the effect of the trapezoid grooves on the k eff 2 and the spurious modes in S 1 mode LWRs.…”