Structural, morphological and acoustic properties of AlN thick films sputtered on Si(001) and Si(111) substrates at low temperature

Polycrystalline AlN thick films were deposited on Si(100) and Si(111) substrates by reactive radio frequency sputtering technique at low temperature. The structure and the morphology of the films were investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. These measurements showed that the AlN films were highly c-axis oriented, with low surface roughness. The surface acoustic wave (SAW) properties of the films were investigated: a mean value of 3.8×10-12 C/N was estimated for the piezoelectric strain constant d33; the phase velocities of SAW’s propagating in polycrystalline AlN/Si structures, for different film thicknesses, were calculated and found to be in good agreement with the theoretical velocities evaluated for SAW’s propagating in single crystal AlN/Si structures.