A 56 GHz Trilayer AlN/ScAlN/AlN Periodically Poled FBAR

Emerging wireless communication standards call for higher carrier frequencies, presenting challenges to frontend filter design for 5G and beyond. Bulk acoustic wave (BAW) resonators have been widely employed in sub-6 GHz filters. A periodically poled multilayer piezoelectric structure is employed in a higher order mode BAW resonator operating at mm-waves. Such resonators are capable of achieving high Qs while maintaining the electromechanical coupling factors at mm-waves. An MBE grown trilayer AIN/ScAIN/AIN thin film bulk acoustic resonator (FBAR) is designed and fabricated. It can be polarization switched electronically to reverse the piezoelectric orientation in ScAIN in order to operate at mm-waves. In this work, a new MBE grown trilayer design has been fabricated. This periodically poled FBAR operates at 56 GHz with a coupling factor of 4.2% and a quality factor of 60.