Behavior of Cu Al films at the SiO interface

The interaction of a sputter-deposited Cu0.6Al0.4 film with SiO2 Cu0.6Al0.4rSiO2.is investigated using X-ray photoelectron spectroscopy XPS.and ex-situ scanning electron microscope SEM.equipped with energy dispersive X-ray analysis EDX.capability. The data indicate that aluminum segregates to the SiO2 interface and becomes oxidized. The formation of the aluminum oxide at the interface results in stronger chemical interaction of copper with the substrate. For copper coverages less than ;0.31 ML based on a CurO atomic ratio., only Cu I. formation is observed. At higher coverages, Cu 0. is observed. The change in slope is coincident with the change in copper oxidation state. The adhesion behavior of copper in the Cu0.6Al0.4rSiO2 case is similar to that of copper metal sputter-deposited onto a-Al2O3 0001.. These data are in contrast with the observed behavior of copper metal deposited onto SiO2 CurSiO2.. The data for CurSiO2show that copper does not wet SiO2and forms 3-D nuclei. Furthermore, post-annealing experiments performed on Cu0.6Al0.4rSiO2 show that neither de-wetting nor diffusion of copper occurs for temperatures up to 800 K. The data indicate that aluminum alloyed with copper at the SiO2 interface serves as an effective adhesion promoter and thermal diffusion barrier. q2000 Elsevier Science B.V. All rights reserved.