AVS 46th International Symposium
    Thin Films Division Friday Sessions
       Session TF-FrM

Paper TF-FrM8
Morphology and Growth of Metal Thin Films on Si Probed by In Situ Spectroscopic Ellipsometry@footnote 1@

Friday, October 29, 1999, 10:40 am, Room 615

Session: In-situ Characterization and Material Process Imaging
Presenter: C. Liu, Argonne National Laboratory
Authors: C. Liu, Argonne National Laboratory
J. Erdmann, Argonne National Laboratory
A. Macrander, Argonne National Laboratory
Correspondent: Click to Email
Here we present results of in situ spectroscopic ellipsometry studies of sputtered thin films of Au, Pt, Pd, Rh, Cr, Cu grown on Si wafers. This study was carried out systematically on incrementally grown metal thin films. Multiple data sets obtained for each film material with incremental thicknesses were analyzed using both flat-film and rough-film models. We found that the initial growth of these metal films on Si is correlated with their chemical bond strength with oxygen in the native oxide of Si. Metals with higher bond strength (such as Cr) grow smoother at the early stage of growth and have a better adhesion to the Si wafer. In metal/Si systems, a Cr thin film is thus commonly added as a "glue" layer between the metal and Si for better adhesion. The Cr film however, becomes rougher as its thickness increases. A glue layer of Cr should not exceed 10 nm to keep the film smooth. Rh films grow smoothly on a thin (6-nm) Cr-covered Si wafer. But on a thick (100-nm) Cr/Si film, they were initially as rough as the thick Cr film. The roughness decreases as the Rh film thickness increases. A relaxation effect was also observed on Rh/Si films. An increase of ~10% in measured Rh thickness was observed two hours after the growth when a flat-film model was used. This puzzle was solved when a rough-film model was applied. The Rh film simply became rougher in vacuum at room temperature and the total mass of Rh did not change. The same Rh film stored in air shrunk to small individual droplets 6 months later. These findings are important in our x-ray mirror applications. @FootnoteText@ This work is supported by the U.S. Department of Energy, BES, under contract no. W-31-109-ENG-38