Diffusing species and growth interfaces during cobalt disilicide formation

Abstract

The diffusing species and growth interface during CoSi 2 formation has been investigated using a thin Ta layer as well as implanted Xe atoms as markers. Analysis of the position of the markers before and following CoSi 2 formation was carried out using Rutherford backscattering spectrometry. The results showed that when Ta alone was used as a marker it moved deeper into the sample during disilicide formation, thereby suggesting that CoSi 2 growth was by-in-large the result of silicon diffusion to the CoSi 2 CoSi interface. On the other hand, when implanted Xe atoms were used as a marker the results indicated that CoSi 2 growth took place by Co diffusion to the Si〈〉 CoSi 2 interface. In an attempt to try and reconcile these conflicting results a combination of metal marker and implanted Xe atoms was used. On CoSi 2 formation the Ta marker was once again observed to move deeper into the sample while the Xe marker again moved towards the sample's surface. It is argued that the most likely explanation of the cause for the conflicting results is that the implanted Xe atoms agglomerated into bubbles, and that these bubbles were then dragged by the moving phase boundary during silicide growth.