Cross-sectional dilation mode resonator with very high electromechanical coupling up to 10% using AlN

For the first time in the development of piezoelectric micromechanical resonators, this paper presents a new class of cross-sectional dilation mode resonators (XDMR) that achieve unprecedentedly high electromechanical coupling constant: k_t² up to 10% for aluminum nitride (AlN) based resonators and 19% for zinc oxide (ZnO) based resonators. Detailed discussions on the geometry design, FEM simulation, and process challenge are provided in this paper to give insight on this novel high-k_t² piezoelectric resonator technology and, more importantly, guide the future development of mechanical resonators with coherent 2D/3D mode shapes.