Structural and elastic characterization of Cu-implanted SiO2 films on Si„100... substrates

Cu-implanted SiO2 films on Si 100 have been studied and compared to unimplanted SiO2 on Si 100 using x-ray methods, transmission electron microscopy, Rutherford backscattering, and Brillouin spectroscopy. The x-ray results indicate the preferred orientation of Cu 111 planes parallel to the Si substrate surface without any directional orientation for Cu-implanted SiO2/Si 100 and for Cu-implanted and annealed SiO2/Si 100 . In the latter case, transmission electron microscopy reveals the presence of spherical nanocrystallites with an average size of 2.5 nm. Rutherford backscattering shows that these crystallites and the Cu in the as-implanted film are largely confined to depths of 0.4−1.2 m below the film surface. Brillouin spectra contain peaks due to surface, film-guided and bulk acoustic modes. Surface longitudinal acoustic wave velocities for the implanted films were 7% lower 2% higher than for unimplanted SiO2/Si 100 . Elastic constants were estimated from the acoustic wave velocities and film densities. C11 C44 for the implanted films was 10% higher lower than that for the unimplanted film. The differences in acoustic velocities and elastic moduli are ascribed to implantation-induced compaction and/or the presence of Cu in the SiO2 film. © 2007 American Institute of Physics. DOI: 10.1063/1.2437690