Evolution of microstructure in Ti-Ta bilayer thin films on polycrystalline-Si and Si(001)

Abstract

We have studied the formation of titanium silicides in the presence of an ultra-thin layer of Ta, interposed between Ti and Si, using in situ X-ray diffraction (XRD), resistance measurements, elastic light scattering and exsitu transmission electron microscopy. On both poly-Si and Si(001) substrates the Ta thickness was varied from 0 to 1.5 nm while the Ti thickness was held constant at ∼ 27 nm. The time-resolved XRD shows that the volume fraction of the C40 and metal-rich silicide phases grows with increasing Ta layer thickness. Among the Ta thicknesses we examined, 0.3 nm is the most effective in lowering the C49-C54 transformation temperature. Ex situ texture analysis shows that the C54 disilicide film is predominantly (010) textured for the Ti/0.3 nm Ta sample on both poly-Si and Si(001). The final C54 texture is significantly different for Ta layers thinner or thicker than the optimal 0.3 nm. This suggests that the most effective thickness for lowering the C54 formation temperature could be related to the development of a strong (010) texture. © 2004 Elsevier B.V. All rights reserved.