4-nm thick multilayer structure of multi-component (AlCrRuTaTiZr)Nx as robust diffusion barrier for Cu interconnects

This work develops a multilayer structure of alternating (AlCrRuTaTiZr)N0.5 senary nitride and AlCrRuTaTiZr senary alloy with a total thickness of only 4 nm as a diffusion barrier layer for application to Cu interconnects. Under annealing at a high temperature of 800 °C, the interdiffusion of Cu and Si through the multilayer structure was effectively retarded without the formation of any Cu silicides. Interdiffusion occurred only at 900 °C, and compounds that included Cu3Si were thus formed. This finding suggests that the high endurance temperature of the diffusion barrier is probably attributable to the stable amorphous solid-solution structure, the high packing factor, the severe lattice distortions that are caused by the incorporation of multiple components and the elongated diffusion path through the multilayer stacking structure.