ScAlN BAW resonator technology with coupling coefficients up to 21% for high performance filter design

Acoustic resonators working at high frequencies with wide bandwidths are at the center of products using the new 5G bands, therefore requiring piezoelectric materials with higher electromechanical coupling coefficients than AlN. In this work we have designed and fabricated FBAR resonators using highly doped ScAlN capable of reaching high effective coupling coefficients (up to 21%), while also demonstrating high quality factors. We are reporting the first FBAR resonators with effective coupling coefficients above 20% with a high figure of merit (FOM I > 80). Acoustic filters have also been fabricated and show bandwidths up to 1 GHz.