ION-BEAM-ASSISTED DEPOSITION OF AL FILMS ON SI

Ion beam assisted deposition (IBAD) was used to grow thin Al films (si milar to 100 nm thick) onto Si substrates at room temperature. Al was deposited by electron gun evaporation, while an Ar+ ion beam bombarded the film during the growth. Ion beam energies of 300, 500, and 650 eV were used, with current densities ranging between 4 and 20 mu A/cm(2) . Polycrystalline Al films have been obtained, whose structural proper ties were strictly related to the IBAD parameters (ion current and ene rgy). Samples were analyzed by transmission electron microscopy and Ru therford backscattering spectrometry, pointing out the following effec ts: (1) IBAD produces smaller polycrystalline Al grains with respect t o a film evaporated in standard high vacuum conditions; (2) the Al gra in size decreases by increasing the ion current or decreasing the ion energy; (3) sputtering yields during IBAD are higher with respect to a postdeposition bombardment process, and show an inverse trend with th e ion beam energy. Results have been explained in terms of modificatio n of kinetics of growth induced by IBAD. A simple model is also propos ed to take into account the unexpected result about the sputtering yie ld. Finally, the IBAD capability to modify the microstructure of the A l films was used to improve the coverage of artificially stepped subst rates. (C) 1995 American Vacuum Society.