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

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 (Qscr_r) 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 Qscr_r of the fabricated FBAR was as high as 1557 at 3.698 GHz. We achieved the high Qscr_r value FBAR using high oriented AlN (0002) film by the MOCVD method