Growth and oxidation of thin film Al sub 2 Cu

Al sub 2 Cu thin films (approx =382 nm) are fabricated by melting and resolidifying Al/Cu bilayers on a SiO sub 2 on Si(100) substrate in the presence of a approx =3 nm Al sub 2 O sub 3 passivating layer. X-ray photoelectron spectroscopy (XPS) measures a 1.0 eV shift of the Cu 2p sub 3/2 peak and a 1.6 eV shift of the valance band relative to metallic Cu upon Al sub 2 Cu formation. Scanning electron microscopy and electron back-scattered diffraction show that the Al sub 2 Cu film is composed of 30-70 mu m wide and 10-25 mm long cellular grains with (110) orientation. The atomic composition of the film as estimated by energy dispersive spectroscopy is 67 plus/minus 2% Al and 33 plus/minus 2% Cu. XPS scans of Al sub 2 O sub 3 /Al sub 2 Cu taken before and after air exposure indicate that the upper Al sub 2 Cu layers undergo further oxidation to Al sub 2 O sub 3 even in the presence of approx =5 nm Al sub 2 O sub 3 . The majority of Cu produced from oxidation is believed to be excluded from the Al sub 2 O sub 3 layers, based upon the lack of evidence for metallic Cu in the XPS scans. In contrast to Al/Cu passivated with Al sub 2 O sub 3 , melting/resolidifying the Al/Cu bilayer without Al sub 2 O sub 3 results in phase-segregated dendritic film growth.