TiSi2/TiN–A Stable Multilayered Contact Structure for Shallow Implanted Junctions in VLSI Technology

A low resistive, electrically and mechanically stable three level metallization scheme has been developed TiSi2 was adopted as a low contact resistance material to silicon, and TiN was selected as a diffusion barrier between the silicide and the A1 interconnect layer. The Ti/TiN bilayer was deposited by magnetron sputtering. It is shown, using RBS and X-ray diffraction that the deposited Ti reacts to form TiSi2, and the upper titanium nitride layer transforms to a stoichiometric compound TiN. Furthermore, it is demonstrated that TiN acts as a diffusion barrier between TiSi2 and aluminium up to 550°C and that the onset for interdiffusion occurs at 600°C. Finally, the interposition of a third sacrificial Ti layer between the nitride film and the aluminium top layer is shown to prevent intermixing between the A1 layer and Si even after a prolonged heat treatment at 600°C.