Narrow interconnects: The most conductive metals

In situ transport measurements on epitaxial metal layers (Cu, Co, Ru, Rh, Ir) in combination with first-principles simulations are used to evaluate the resistivity scaling and determine the most conductive metals in the limit of narrow interconnect lines. Rh and Ir are promising because their product of the bulk resistivity times the bulk electron mean free path ρ
_o
×λ is the smallest. However, their grain boundary reflection probability is approximately two times higher than for Cu, negating some of the benefit of the small λ. Ru is also promising, because its ρ
_o
×λ value is slightly (24%) below that of Cu but more importantly because of the smaller liner thickness which provides a larger cross-sectional area for narrow Ru interconnect lines.