Design of BST-on-Si composite FBARs for switchable BAW filter application

Abstract

This paper presents optimal design of switchable BST-on-Si composite film bulk acoustic resonators (FBARs) for bulk acoustic wave (BAW) filter applications. To design BAW filters with lower insertion losses and wider bandwidth, resonators' Q×K, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is maximized. Furthermore, lateral wave spurious resonances that can significantly degrade the composite FBARs performance, are eliminated by designing a frame at the border of ferroelectric-on-Si FBARs. Using COMSOL simulations, a raised frame is designed at the border of BST-on-Si composite FBAR, which is dispersion type I resonator. Designed structure has been validated by fabrication and measurement and it is compared to typical composite FBAR structures without frame.