Exafs study of the initial interface region formed by thin zirconium and titanium films on silicon(111)

While titanium has long been of interest for use in creating low resistivity metal contacts on silicon, the commonly resulting epitaxial silicide (TiSi2) is often of C49 phase and is, unfortunately, metastable - transforming to the stable C54 phase at higher temperatures. Zirconium, however, only exhibits a C49 phase disilicide and, being in the same periodic group, is chemically similar to Ti, affording the possibility of alloying small quantities of Zr with Ti in order to stabilize the epitaxial C49 structure. Both Ti and Zr have been reported to show a strongly disordered interface region at low temperatures, but little quantitative structural work has been performed on the Zr:Si system. To this end, an initial structural study of the Zr on Si (111) system has been undertaken. Thin films (100Å) of Zr were deposited in UHV conditions onto atomically clean Si(111) wafers and annealed in situ at fine temperature intervals between 300 and 425°C, over which range Auger spectroscopy indicated Si diffusion to the surface. A comparison will be made with the Ti:Si system for samples of 100Å Ti prepared under the same conditions.