Silicidation of Co/Ti, Co/Nb, and Co Hf bilayers on the Si (100) substrate

The formation mechanism of epitaxial cobalt silicide from Co/Ti, Co/Hf, and Co/ Nb/(100) Si structures has been investigated. The crystallographic ori entations of the silicide films formed after annealing these bilayer metals on (100)Si at 800 degrees C are found to strongly depend upon the thin met al layer used as an epitaxy promoter. Epitaxial cobalt silicide was grown f rom Co/Ti/(100)Si. Epitaxial and non-epitaxial CoSi2 formed simultaneously in Co/Hf/(100)Si, while only non-epitaxial CoSi2 formed in Co/Nb/(100)Si sy stem. The reason why the crystallographic orientation of CoSi2 differs for these systems seems to be related to the formation and decomposition of sta ble reaction barriers at high temperatures. Stable reaction barriers formed at high temperatures make the uniform diffusion of Co atoms possible, resu lting in the growth of epitaxial CoSi2.