Interdiffusion and compound formation in the cSi/PtSi/(TiW)/Al system

Scanning electron microscopy, microphobe measurements, Auger electron spectroscopy and X-ray diffraction were used to investigate interdiffusion phenomena occurring in the cSi/PtSi/(TiW)/Al system (where cSi denotes for crystalline silicon) widely used in silicon integrated circuits. The formation of intermetallic compounds begins with the diffusion of aluminum through the barrier layer of the Ti0.1W0.9 pseudoalloy and the consequent growth of the Al2Pt phase which causes the PtSi layer to decompose. At the same time Al12W forms at the Al(TiW) interface. As a result of the volume increase because of the formation of the Al2Pt, the TiW layer breaks, allowing the dissolution of silicon and the growth of WSi2 and TixW1−xSi2 compounds. A few monolayers of oxygen at the Al(TiW) interface substantially delay the interdiffusion process