Eradication of asymmetric spurious modes in AlN MEMS resonators using mode conversion

This papers reports on a spurious mode suppression technique that converts the asymmetrical (A0) mode to the intended symmetrical (S0) mode vibrations by installing a notch in aluminum nitride (AlN) laterally vibrating resonators. The technique has been experimentally validated to simultaneously eradicate the A0 spurious mode and enhance the S0 mode electromechanical coupling (k
_t
²
) for the monolithically integrated resonators over a wide frequency range (100~600 MHz). The method described herein has overcome a major bottleneck obstructing the deployment of single-chip multi-frequency AlN resonators as a commercially viable solution for RF front-end filtering. It is also the first demonstration of complete A0 mode suppression in lamb-wave resonators with enhancement of k
_t
²
.