Self-aligned TiNxOy/TiSi2 contact formation

Abstract Bilayers of TiN x O y /TiSi 2 have been formed successfully on silicon as low resistive contacts as well as diffusion barriers during self-aligned silicide processing by direct rapid thermal nitridation of TiSi in an NH 3 ambient. The formation of TiN x O y is due to the reaction among titanium atoms in the silicide layer, nitrogen atoms which decompose from NH 3 , and oxygen atoms. The oxygen in the TiN x O y layer has been identified in the form of a TiO phase which can suppress aluminium diffusion during sintering of the Al/TiN x O y /TiSi 2 structure, making the bilayer an effective diffusion barrier between aluminium and the silicon substrate. The growth of the TiN x O y layer can be controlled by the annealing temperature and/or time through the nitridation of TiSi 2 . This bilayer can have a low sheet resistance of 1.25–2.5 Ω/□ with a controlled thickness ratio of TiN x O y /TiSi 2 . The Al/TiN x O y /TiSi 2 /Si contact structure is thermally stable up to 500°C for 30 min sintering in forming gas. In addition, this bilayer has a good chemical stability in dilute HF for at least 60 s. Since TiN x O y /TiSi 2 is formed on source, drain and gate areas in a self-aligned fashion by two-step rapid thermal processing, this technique can easily be applied to submicron device fabrication.