Formation and oxidation of implanted cobalt silicides on polycrystalline-silicon

An alternative method of silicide formation by direct implantation of high doses of metal ions into polycrystalline silicon is discussed. The doses used were in the region of 5×10¹⁷ cm^-2 at energies in excess of 150 keV. Low sheet resistance (<1 Ω/sq.) cobalt disilicide (polycide) layers were formed by this technique and subsequently oxidized to assess process compatibility. The method overcomes the problems associated with metal on poly-Si interdiffusion reactions, such as retarded diffusion due to surface barriers or uneven diffusion due to the presence of grain boundaries in the poly-Si. Hence, the technique can provide a high degree of control over silicide distribution