Barrier performance of ultrathin amorphous Nb–Ni film between copper and silicon

• 5-nm-thick Nb–Ni is used first as a diffusion barrier layer between Cu and Si.
• The ultrathin Nb–Ni film has a very good barrier performance up to 750 °C.
• Dewetting of Cu originates from the void nucleation at the Cu/Nb–Ni interface.
• The cheap and simply ultra-thin Nb–Ni can be an ideal diffusion barrier layer.

We have fabricated the Cu (50 nm)/Nb–Ni (5 nm)/Si heterostructures, annealed at various temperatures up to 800 °C in a high vacuum system, to investigate the barrier performance of the ultrathin amorphous Nb–Ni film between Cu and Si. No impurity peaks are observed from the X-ray diffraction patterns of the Cu/Nb–Ni/Si heterostructures annealed up to 800 °C. The island-like surface is observed for the 800 °C annealed sample, indicating the failure of the Nb–Ni barrier layer, which is attributed to agglomeration of Cu film resulting from the dewetting of Cu with the underlying Nb–Ni layer during high temperature annealing. The activation energy for Cu dewetting with Nb–Ni layer is estimated to be 0.86 eV. Our result demonstrates that ultra-thin amorphous Nb–Ni film can be an ideal diffusion barrier layer for Cu interconnection.