Electrical resistivity of sputtered Cu/Cr multilayered thin films

Parallel (in-plane) electrical resistivities of single-layered Cu and Cr films, and Cu/Cr multilayered thin films sputter deposited on Si substrates were evaluated as a function of layer thicknesses ranging from 2.5 to 150 nm in the temperature range of 4–325 K. The resistivity of the multilayers at a given temperature increased and residual resistivity ratio decreased with decreasing layer thicknesses. At 300 K, the resistivity of a 1 μm thick Cu film was approximately equal to the bulk value, but the resistivity of the Cr film was an order of magnitude higher than that of bulk Cr. The microstructures of the multilayers and the single-layered Cu and Cr thin films were characterized by transmission electron microscopy. For layer thicknesses ranging from 2.5 to 150 nm, the multilayers exhibited sharp, planar interfaces between the two phases. The individual Cu and Cr layers were nanocrystalline with near-equiaxed grains in Cu and columnar grains in Cr. The dependence of electrical resistivity on the layer thickness of multilayers is explained using a model that accounts for interface scattering and thin-film resistivities of polycrystalline Cu and Cr.