Fabrication of high-Q film bulk acoustic resonator (FBAR) filters with carbon nanotube (CNT) electrodes

FBAR devices with carbon nanotube (CNT) electrodes have been developed with the aim of taking advantage of the low density and high acoustic impedance of the CNTs compared to other known materials. The influence of the CNTs on the frequency response of the FBAR devices was studied by comparing two identical sets of devices, one set comprised FBARs fabricated with chromium/gold bilayer electrodes, and the second set comprised FBARs fabricated with CNT electrodes. It was found that the CNTs had a significant effect on attenuating travelling waves at the surface of the FBARs membranes due to their high elastic stiffness. Finite element analysis of the devices fabricated was carried out using COMSOL Multiphysics, and the numerical results confirmed the experimental results obtained.