Microstructural and compositional characterization of TiW/Al(0.8%Si)/TiW/PtSi/(100)Si

Abstract

The microstructure and composition of a contact composed of an outer layer of (30nm) Ti 0.1W 0.9, an intermediate layer made of (550 nm) Al(0.8 wt% Si), a diffusion barrier layer of (90 nm) Ti 0.1W 0.9 and platinum silicide layer (about 50 nm thick) as an interconnection to the (100)Si substrate was studied after heat treatments at temperatures between 400 and 550°C. The contact microstructure was characterized by X-ray diffraction, Auger electron spectroscopy and electron microscopy. It was established that the contact loses its stability at 400°C, due to a diffusion of Ti and W into the Al layer, and the formation of new phases such as Al 3Ti and Al 12W at the Al/TiW interfaces. At 475°C, Al already penetrates the inner diffusion barrier, but not the outer TiW layer. In addition, it was found that the diffusion barrier failure at 475°C was followed by formation of bulges on the inner TiW layer surface, due to the increase in the volume resulting from the growth of Al 2Pt at the interface between the TiW and PtSi layers.