Phase formations in Co-Silicon system

Interactions between thin cobalt, 40 nm, and a thick - 250 nm -silicon film were investigated by in situ sheet resistance measurements. Poly and amorphous silicon films, both deposited by CVD, were used. MeV He-4(+) Rutherford Backscattering and X-ray diffraction techniques were used to infer the kinds and thicknesses of the compounds formed. Co2Si and CoSi form, on both silicon substrates, in the same way and in substantial consistency with the data reported in literature. The formation of CoSi2 seems to be nucleation controlled on polysilicon, while on amorphous the formation is controlled by diffusion and no nucleation barrier has been detected. The amorphous silicon remains amorphous during the CoSi2 formation, thus suggesting that the model which attributes the absence of a nucleation barrier to silicon crystallization does not hold. (C) 2004 Elsevier B.V. All rights reserved.