CoSi₂ formation in the presence of Ti, Ta or W

Abstract

CoSi2 formation was studied in the presence of Ti, Ta and W, both for bilayers and as-deposited alloys. Phase formation and preferential orientation of the CoSi2 phase are strongly dependent on the interlayer thickness. For thin interlayers and dilute Co alloys, CoSi 2 nucleation is delayed to higher temperature and CoSi 2(220)//Si(400) nuclei are formed preferentially. The presence of Ti, Ta or W in the grain boundaries of the CoSi layer influences CoSi2 nucleation by enhancing the CoSi grain boundary cohesion and/or reducing grain boundary diffusion. For thicker interlayers (typically >1 nm), the interlayer acts as a diffusion mediating medium, slowing down Co diffusion and thus promoting the formation of a CoSi2 layer that is epitaxially aligned with the Si substrate. © 2004 Elsevier B.V. All rights reserved.