Sputtered Ta-Si-N diffusion barriers in Cu metallizations for Si

Electrical measurements on shallow Si n⁺-p junction diodes with a 30-nm TiSi₂ contacting layer demonstrate that an 80-nm-thick amorphous Ta₃₆Si₁₄N₅₀ film prepared by reactive RF sputtering of a Ta₅Si₃ target in an Ar N₂ plasma very effectively prevents the interaction between the Si substrate with the TiSi₂ contacting layer and a 500-nm Cu overlayer. The Ta₃₆Si₁₄N₅₀ diffusion barrier maintains the integrity of the I-V characteristics up to 900 C for 30-min annealing in vacuum. It is concluded that the amorphous Ta ₃₆Si₁₄N₅₀ alloy is not only a material with a very low reactivity for copper, titanium, and silicon, but must have a small diffusivity for copper as well