Residual stresses in polycrystalline Cu/Cr multilayered thin films

Residual stresses in sputter-deposited Cu/Cr multilayers and Cu and Cr sing le-layered polycrystalline thin films were evaluated by the substrate curva ture method. The stresses in the multilayers were found to be tensile and t o increase in magnitude with increasing layer thickness (h) to a peak value of similar to 1 GPa for h = 50 nm. For h > 50 nm, the residual stress decr eased with increasing h but remained tensile. The same trends were observed in single-layered Cu and Cr thin films, except that the maximum stress in Cu films is 1 order of magnitude lower than that in Cr. Transmission electr on microscopy was used to study the rnicrostructural evolution as a functio n of layer thickness. The evolution of tensile growth stresses in Cr films is explained by island coalescence and subsequent growth with increasing th ickness. Estimates of the Cr Film yield strength indicated that, for h grea ter than or equal to 50 nm, the residual stress may be limited by the yield strength. Substrate curvature measurements on bilayer films of different t hicknesses were used to demonstrate that a non-negligible contribution to t he total stress in the multilayers arises from the interface stress.