Aluminium nitride films deposition by reactive triode sputtering for surface acoustic wave device applications

AlN thin films have been deposited by reactive triode sputtering. The effect of the nitrogen contents in the discharge on films stoichiometry and crystal orientation has been investigated. AlN films have been studied by means of Fourier-transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. Dense AlN layers with very high electrical resistivity, high index of refraction and large optical band gap were obtained at high deposition rates. Finally, the optimized films were applied for the synthesis of surface acoustic waves filters. Acoustic velocities up to 5130 m s−1 for AlN/Si structure, 5548 m s−1 for AlN/sapphire structure, and 9900 m s−1 for AlN/diamond structure were obtained.