The elastic constants of sputtered aluminum nitride films

Brillouin light scattering has been used for determining the five independent elastic constants of polycrystalline AlN films grown by DC magnetron sputtering on Si₃N₄ coated (100)-Si substrates. The elastic constants c₆₆ and c₁₁ have been selectively determined from detection of the shear horizontal mode and of the longitudinal mode travelling parallel to the film surface, respectively. The three remaining elastic constants, namely c₁₃ , c₃₃ and c₄₄, have been obtained from detection of the Rayleigh surface mode and of the longitudinal bulk wave propagating at different angles from the surface normal. The values of the elastic constants of these sputtered AlN films exhibit an appreciable dependence on the microstructural properties of the films, which are strongly affected by the deposition conditions. However, they are rather close to those previously determined in epitaxial AlN films grown at high temperature by MOCVD