Effects of Ti interlayer on Ni/Si reaction systems

The effects of Ti interlayer on the formation of Ni silicides on Si(100) substrate was investigated. The phase and microstructure of Ni silicides during isochronal annealing treatment are monitored in situ by curvature measurement and characterized ex situ by other measurements. The addition of a thin Ti layer which formed an amorphous layer with the Si substrate acted as a diffusion barrier for the Ni atom in the early phase transformation process. The transformation temperature for the NiSi is significantly increased in an isochronal annealing process. When the NiSi phase is formed, the Ti-related layer moves to the surface of the silicide film. The temperature for the transformation of NiSi to NiSi2 is relatively irrelevant to the presence of the Ti interlayer. A preferential orientation of (200) and (002) was found in the NiSi phase formed via the Ti interlayer, which significantly improved the epitaxial quality of NiSi2 on Si(100) substrate with a stepwise interface bounded by (111) and (100) planes. The top continuous Ti-related layer causes the incomplete accommodation of the thermal stress for the system. Upon disintegration of the Ti-related layer, the thermal stress of the system could be completely accommodated by relaxation of the NiSi layer.