Residual stresses in polycrystalline Cu/Cr multilayered thin films A. Misra; H. Kung Residual stresses in polycrystalline Cu/Cr multilayered thin films

摘要

Residual stresses in sputter-deposited Cu/Crmultilayers and Cu and Cr single-layered polycrystalline thinfilms were evaluated by the substrate curvature method. Thestresses in the multilayers were found to be tensile and toincrease in magnitude with increasing layer thickness (h) to apeak value of -1 GPa for h = 50 nm. For h> 50 nm, the residualstress decreased with increasing h but remained tensile. Thesame trends were observed in single-layered Cu and Cr thinfilms, except that the maximum stress in Cu films is 1 order ofmagnitude lower than that in Cr. Transmission electronmicroscopy was used to study the microstructural evolution as afunction of layer thickness. The evolution of tensile growthstresses in Cr films is explained by island coalescence andsubsequent growth with increasing thickness. Estimates of theCr film yield strength indicated that, for h > 50 nm, the residualstress may be limited by the yield strength. Substrate curvaturemeasurements on bilayer films of different thicknesses wereused to demonstrate that a non-negligible contribution to thetotal stress in the multilayers arises from the interface stress.