6.9 GHz Film Bulk Acoustic Resonator based on Pulsed Laser Deposited LiNbO3 Film

In this work, 200 nm-thick LiNbO
3
layers have been grown on Ru/Si and Pt/Si substrates using an industrialized Pulsed Laser Deposition (PLD) system. Film’s properties have been investigated by means of X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Secondary Ions Mass Spectrometry (SIMS). In both cases, XRD analysis highlights the coexistence of LiNbO
3
phase and a Li-deficient secondary phase (LiNb
3
O
8
). A c-axis preferential growth orientation have been obtained for LiNbO
3
film deposited on Pt/Si substrate. The formation of the Li-deficient secondary phase is related to Li diffusion, as highlighted by SIMS measurements. Finally, the fabricated Film Bulk Acoustic Resonator (FBAR) testifies to the piezoelectric activity of the as-deposited LiNbO
3
film. The FBAR based on pulsed laser deposited LiNbO
3
film displays an electromechanical coupling coefficient close to 6.7% at 6.9 GHz. Process optimizations (electrodes, piezoelectric films) are in progress in order to improve the microstructural properties of the as-deposited LiNbO
3
layer and thus the quality factor.