Evaluation of LPCVD MeSiN (MeTa, Ti, W, Re) diffusion barriers for Cu metallizations

Abstract

LPCVD MeSiN (MeRe, W, Ti, Ta) thin films were investigated for use as diffusion barriers between Cu overlayer and oxidized silicon substrates. Gaseous precursors were silane, in situ fabricated metal chloride, ammonia, hydrogen and argon. Thermodynamic simulations of the MeSiN and the CVD MeSiNClHAr systems were combined with the experimental study. It was shown that the existence (titanium and tantalum) or non-existence (rhenium and tungsten) of stable metal nitrides could explain the differences observed in the morphology of the four systems. Amorphous or nanocrystallized ReSiN and WSiN whereas crystallized TiSiN and TaSiN films were deposited. The ReSiN an WSiN layers crystallization temperature was found to be around 1173 K. Their morphology, thermal stability, resistivity and the performances of the four copper metallized MeSiN systems were evaluated. WSiN material appeared as the most promising diffusion barrier thanks to its morphology, resistivity around 1 mΩ cm and performances in blocking copper diffusion.