IDENTIFICATION OF THE 1ST NUCLEATED PHASE IN THE INTERFACIAL REACTIONS OF ULTRAHIGH-VACUUM DEPOSITED TITANIUM THIN-FILMS ON SILICON

The first nucleated phase in ultrahigh vacuum deposited Ti thin films on silicon has been unambiguously identified utilizing high-resolution transmission electron microscopy (HREM) in conjunction with optical diffractometry. Ti5Si3 was found to form first at the interface of the Ti overlayer and the amorphous interlayer. For plan-view specimens of the samples annealed at 450-degrees-C for 30 min, 1 and 2 h, all 15 silicide diffraction rings corresponding to interplanar spacings longer than 0.098 nm could be attributed to Ti5Si3. Ti5Si3 was also the only silicide phase that could match the symmetry and lattice spacings of the HREM images. The observation is consistent with a kinetic model which predicts that the crystalline phase with composition and structure nearest to that of the amorphous interlayer will be first nucleated.