Diffusion barrier performance of nano-structured and amorphous Ru–Ge diffusion barriers for copper metallization

In the experiment, nano-structured and amorphous ultrathin Ru–Ge interlayers (∼15 nm in thickness) were deposited between Cu(Ru) alloy film and Si substrate via co-sputtering functioning as preventive diffusion barrier layers. After annealing at different temperatures, X-ray diffraction and four-point probe method revealed that the amorphous Ru–Ge layer effectively suppressed the Cu diffusion into Si substrate up to a temperature of at least 873 K; however, it is less than 773 K for the nano-structured Ru–Ge layer. A self-formed amorphous multilayer of Ru(RuOx)/RuGexCuy could be attained by annealing Cu/Cu(Ru)/Ru–Ge(amorphous)/Si system at a very low temperature (even 473 K). The results proved that the amorphous Ru–Ge system could self-form the multilayer diffusion barrier before the diffusion reaction between Cu and Si and improved the thermal stability of the Cu interconnection significantly.

► Amorphous Ru–Ge layer as Cu diffusion barrier layer.
► Amorphous Ru–Ge layer improved the thermal stability of Cu/Si.
► A multilayer barrier is self-formed in amorphous Ru–Ge system by annealing at a low temperature.
► The self-formed diffusion barrier depends on the diffusion and bond of Cu to Ru–Ge layer.