Integration of electrostrictive Ba0.7Sr0.3TiO3 thin films into Bulk Acoustic Wave resonator for RF-frequency tuning under DC bias

This paper deals with the development of newly reported Bulk Acoustic Wave (BAW) resonators using electrostrictive Barium Strontium Titanate (BST) oxide thin films for GHz applications. Electrostriction enables tuning acoustic parameters according to a large DC bias which is superimposed over a small RF signal. As a result, such a BAW resonator behaves like conventional piezoelectric BAW but RF electrical responses can be switched OFF or tuned once turned ON. One of the major challenges is to achieve electromechanical coupling and quality factors as good as AlN-based BAW. This study gives preliminary results in terms of modeling for electromechanical coupling optimization and experimental investigations particularly focused on integration of Ba_0.7Sr_0.3TiO₃ in BAW resonators.