EFFECTS OF THE PRESENCE OF NATIVE SILICON-OXIDE AT THE FE/SI INTERFACE ON THE FORMATION OF SILICIDES STUDIED BY AUGER-SPECTROSCOPY

Auger lineshape analysis on Si LW and Fe LMM transitions was used to investigate the mechanisms of iron mono- and disilicide formation at the Fe/Si interface in the absence and in the presence of a native oxide layer (SiO(x)) approximately 0.5 nm thick on the silicon surface. Fe films, 0.3 to 2 nm thick, were evaporated on Si(111) and on SiO(x)/Si(111) surfaces in UHV environment. Thereafter thermal treatments up to 580-degrees-C were performed in situ. Besides the well known mechanism of silicide formation via silicon diffusion at the Fe/Si interface, it was demonstrated that silicide formation in the presence of native oxide is inhibited at room temperature while, at T greater-than-or-equal-to 450-degrees-C, it occurs at the SiO(x)/Si interface via Fe diffusion through the oxide layer. This ends in a Fe/SiO(x)/FeSi/Si or Fe/SiO(x)/FeSi2/Si type of structure. The kinetics of silicide formation in the presence of an oxide layer are therefore dominated by the diffusion of the metal through the oxide.