Directed sputter deposition of AlCu: Film microstructure and microchemistry

Abstract

The microstructure and microchemistry of AlCu films deposited onto unheated oxidized Si(001) substrates by two recently developed directional sputtering techniques, collimated magnetron sputter deposition (CMSD) and ionized magnetron sputter deposition (IMSD), have been investigated using Rutherford backscattering spectroscopy, x-ray diffraction (XRD), plan-view transmission electron microscopy (TEM), cross-sectional TEM (XTEM), and scanning TEM (STEM). Both sets of films had essentially the same average compositions as the alloy targets while exhibiting dense columnar microstructures with (111) preferred orientation, relatively abrupt film/substrate interfaces, and no indication of surface faceting. Microstructure evolution pathways, however, were quite different. IMSD layers exhibited competitive column growth resulting in a degree of (111) orientation which was more than an order of magnitude larger than that found in corresponding CMSD films and, for thicker layers (≥1 μm), larger average column sizes. The IMSD films also had a much smaller spread in the azimuthal distribution of (lll)-oriented columns. XRD line broadening analyses and TEM/XTEM examinations revealed that IMSD layers contained inhomogeneous strain due to residual ion-irradiation-induced defects and, in the upper near-surface region, Al 2 Cu precipitates while CMSD layers appeared defect-free in TEM/XTEM images. The IMSD films were slightly tensile (+0.13±0.01 GPa) and the CMSD films were slightly compressive (—0.18±0.06 GPa). © 1994, American Vacuum Society. All rights reserved.