COMPARATIVE-STUDY OF THE ELASTIC PROPERTIES OF POLYCRYSTALLINE ALUMINUM NITRIDE FILMS ON SILICON BY BRILLOUIN LIGHT-SCATTERING

Brillouin light scattering (BLS) has been used to investigate the elas tic properties of polycrystalline AlN films, about 1 mu m thick, grown by DC-reactive magnetron sputtering on Si3N2 coated (100)-Si substrat es. Taking advantage from the detection of a number of different acous tic modes. a complete elastic characterization of the films has been a chieved. The elastic constants c(11) and c(66) have been selectively d etermined from detection of the longitudinal and of the shear horizont al bulk modes, respectively, travelling parallel to the film surface. The three remaining elastic constants, namely c(44), c(33) and c(13), have been obtained from detection of the Rayleigh surface wave and of the longitudinal bulk wave propagating at different angles from the su rface normal. The values of the elastic constants of these sputtered A lN films depend on the deposition conditions and on the microstructura l properties of the films, especially oxygen contamination and quality of texture. In the case of the films with the best degree of texture and the lowest oxygen content, the values of the elastic constants an rather close to those previously determined in epitaxial AlN films gro wn at high temperature by MOCVD. This demonstrates that sputter deposi tion at relatively low temperature can be used to grow high quality Al N films on Si and is of great importance in view of the integration of these films in the technology of IC semiconductors. (C) 1997 Elsevier Science S.A.