Interface Reaction and Atomic Transport During COSi2 Film Formation

Abstract

ABSTRACTThe formation process of COSi2 films grown from Co deposited on a Si single crystal was investigated as a function of very short annealing times by transmission electron microscopy and x-ray diffraction. Information on the interfacial reactions and atomic transport phenomena was obtained from a microstructural analysis of the CoxSiy layers formed. It was demonstrated that Co is the dominant diffusion species during COSi2 formation. Co atoms are generated at the COSi2/COSi2 interface via the reaction 2CoSi=CoSi2+Co and diffuse to the COSi2/Si interface, where they react with Si by Co+2Si=CoSi2. Direct microscopic evidence indicates that diffusivity of Co atoms along a COSi2 grain boundary greatly exceeds that through the COSi2 lattice. The grain boundary diffusion coefficient is estimated to be up to 100 times larger than the lattice diffusion coefficient. On this basis the influence of grain size on COSi2 film formation is discussed.