Impact of deposition parameters on the characterizations of highly orientated aluminum nitride for film bulk acoustic wave resonator device

AlN thin films were grown on Si(100) and Al/Si(100) substrates by pulsed dc sputtering system using 99.999% purity aluminum as target, and Ar+N₂ gas mixture as precursor. The impact of deposition parameters, including dc power, deposition pressure and substrate temperature, on material properties has been investigated. A good correlation between film crystallinity and dc power, as well as gas pressure, was addressed by X-ray diffraction, and verified by scanning electron microscope (SEM) and ellipsometry. It is found that highly c-axis oriented h-AlN can be obtained at low gas pressure and low deposition rate. For AlN on Al/Si(100) substrate, micro-crack was observed, which was assigned to the large thermal stress between AlN film and Al layer. Crack-free surface has been achieved by reducing the deposition temperature. The deposition mechanism of AlN deposition is discussed. This work provides a material foundation for film bulk wave resonator (FBAR) devices fabrication.