4D-4 Fabrication of FBAR for GHz Band Pass Filter with AlN Film Grown Using MOCVD

Abstract

Film bulk acoustic resonator (FBAR) using AlN film was fabricated. Metal-organic chemical vapor deposition (MOCVD) was used to obtain high oriented AlN (0002) film. The unloaded Q factor (Qscrr) of fabricated FBAR was improved by reduction of Mo electrode resistance and optimization of cavity etching process. Since Mo nitridation degraded Mo resistance, reaction time between Mo and NH3 became shorter than conventional process to suppress the nitridation during AlN deposition. As a result, Mo resistance was improved to be 12.3 muOmegacm from 26.4 muOmegacm. In conventional process using Bosch process to fabricate cavities, insufficient etching selection ratio between Si/SiO2 of 200 brought incomplete structure of cavities. The etching selection ratio between Si/SiO2 was improved to be 650 by change of the etching process. The evaluated Qscrr of the fabricated FBAR was as high as 1557 at 3.698 GHz. We achieved the high Qscrr value FBAR using high oriented AlN (0002) film by the MOCVD method