Formation of epitaxial CoSi2 by a Cr or Mo interlayer:: Comparison with a Ti interlayer

The influence of Cr and Mo on phase formation and preferential orientation of CoSi2 is reported. Three different regimes are distinguished, depending on the thickness of the interlayer. For a thin interlayer or a capping layer, CoSi forms first, as in the standard Co/Si reaction. The remaining Cr or Mo can be considered as a contaminant that is present in the CoSi layer, causing a delay in CoSi2 nucleation and inducing preferential (220) and (400) nucleation. For interlayers with intermediate thickness, epitaxially (400) oriented CoSi2 is formed. For a thick interlayer, a polycrystalline layer of CrSi2 (or MoSi2) is formed first, followed by CoSi formation on top of the CrSi2. At higher temperatures, the CoSi layer is transformed into a polycrystalline, continuous layer of CoSi2 on top of the CrSi2 or MoSi2 layer, while some grains of CoSi2 are formed underneath the CrSi2. A similar behavior for Ti interlayers is observed, although a much thicker Ti layer is needed before the third regime is reached. (C) 2001 American Institute of Physics.