Lateral-wave spurious-modes elimination in switchable ferroelectric BST-on-Si composite FBARs

Abstract

This paper provides experimental results for elimination of lateral-wave spurious modes observed in switchable ferroelectric BST-on-Si composite FBARs using a frame design technique. This approach is used in piezoelectric FBAR design, however here it is applied for the first time to design intrinsically switchable ferroelectric BST acoustic resonators. The BST-on-Si composite FBAR presented here is a structure with the dispersion type-I characteristic, which requires a raised frame to eliminate any higher-order lateral-wave spurious modes. Based on 2-D Multiphysics simulations, FBARs with and without a frame are designed, verifying the utility of using a frame to improve device performance. Both FBARs are fabricated and measured, and then their performance is compared. Measurement results validate the effectiveness of a frame in the design of switchable BST FBARs, allowing for device performance improvement.