Influence of AlN-Interlayer and Growth Parameters of Mo Electrode on AlN Piezoelectric Thin Films for FBAR

This study investigates the deposition of AlN piezoelectric thin films on Si, Si/Mo, and Si/AlN-interlayer/Mo substrates, exploring the impact of different substrates on the quality of AlN thin films and confirming the effectiveness of the AlN interlayer in alleviating the lattice mismatch between Mo and Si. High-quality AlN piezoelectric layer was successfully obtained by optimizing the Mo sputtering conditions under different growth temperature, power, and gas flow. The research found that the orientation and quality of the AlN piezoelectric layer are significantly influenced by the orientation and quality of the Mo substrate. By comparing the morphology and the results of X-ray diffraction (XRD) tests of films on different substrates, the epitaxial growth process of AlN films was revealed. Simulation results further confirmed the role of the AlN-interlayer in improving the quality factor ($Q$ factor) of film bulk acoustic resonator (FBAR). This research provides crucial experimental data and simulation validation for the application of AlN piezoelectric thin films in MEMS packaging technology.