P1H-4 FBAR Characteristics with AlN Film Using MOCVD Method and Ru/Ta Electrode

Film bulk acoustic resonator (FBAR) was fabricated using high oriented AlN(0002) film obtained through the metal-organic chemical vapor deposition (MOCVD) method. We used the Ru/Ta bottom electrode to improve the FBAR resonant characteristics because Ru has a high acoustic impedance and a hexagonal crystalline that is effective to obtaine the high oriented AlN(0002) film. The Ru/Ta electrode had good characteristics under 1100degC in points of the full width at half maximum (FWHM) of Ru(0002), the surface roughness and the electrode resistivity. The evaluated FWHM of AlN(0002) on Ru/Ta at 1050degC was exellent value of 1.2deg. The resonant frequency and anti-resonant frequency of the fabricated FBAR using the Ru/Ta bottom electrode were 5.217 GHz and 5.479 GHz, respectively. The resistance of the FBAR electrodes and of the series-resonance part in modified Butterworth Van Dyke (MBVD) equivalent circuit were improved to 4.3 Omega from 7.0 Omega and to 0.5 Omega from 3.0 Omega compared to the results of previous Mo bottom electrode, respectively. The effective electro-mechanical coupling coefficient (k_eff ²) of the fabricated FBAR was exellent value of 7.0 % and the evaluated Q_r was 329. We successfully fabricated the FBAR with the small insertion loss and the large k_eff ² using the Ru/Ta bottom electrode and high oriented AlN(0002) film.