Barrier properties of ultrathin VN films of low resistivity and high density for Cu interconnects

Abstract

We have examined vanadium nitride (VN) films as a candidate material for the low-resistivity diffusion barrier of Cu interconnects in Si-LSI technology, aimed at reducing the interconnect resistance. We successfully prepared a continuous and uniform VN film as thin as 5 nm with a nanocrystalline texture with grains 2–5 nm in size. The VN barrier applied to the model system of Cu/VN/SiO2/Si and Cu/VN/SiOC/Si shows excellent barrier properties; the ultrathin barrier shows a negligible structural change and the absence of Cu penetration and/or interfacial reaction in the systems after annealing at 500 °C. The properties of an ultrathin VN barrier, such as low resistivity (50 µΩ cm) and high density (5.8 g/cm3), are attributed to the formation of a stable δ-VN phase in a nanocrystalline texture with grains of size smaller than or equal to the barrier thickness that stands high in a structurally stable and chemically inert barrier.