Behaviour of copper atoms in annealed Cu/SiOx/Si systems

Copper thin films of thickness 1000 Angstrom are evaporated on (100) and (1 11) single crystal Si wafers in the presence of interfacial native silicon oxide (SiOx). The behavior of copper and the mechanism of compound formatio n at the Cu/Si interface are studied at different temperatures using scanni ng electron microscopy (SEM), X-ray diffraction (XRD) and Rutherford backsc attering (RBS). Annealing in the 600-750 degrees C temperature range leads to the formation of islands of two copper-rich silicides Cu3Si and Cu4Si. O n the Si(100), after annealing at 750 degrees C, we observe epitaxially gro wn Cu3Si crystallites with square and rectangular shapes. However, on Si(11 1) annealing at the same temperature yields Cu3Si and Cu4Si crystallites wi th droplet-like shapes and no sign of epitaxy. The presence of oxygen, afte r heat treatment under vacuum, is closely related to the formation of coppe r silicide crystallites. (C) 2000 Elsevier Science B.V. All rights reserved .