Dependence of Strain and Plasticity During Thermal Cycling of Different Aluminum Metallization on Alloy Composition, Passivation Material and Passivation Geometry

Abstract

ABSTRACTStress-induced voiding and shear plasticity of passivated metal lines during thermal cycling should be dependent on various properties of both, metallization and passivation, such as geometry and elastic constants and on the flow stress of the metal lines. Therefore we performed strain measurements on passivated lines of various aluminum-alloys with different passivation materials by x-ray diffraction during thermal cycling between RT and 420°C.As samples we used an array of 1μm wide and 0.8μm thick parallel lines, 1μm apart. As metallization sputter deposited Al, AlCu(0.5wt%), AlCu(1.0wt%), and AlSi(1.0wt%)Cu(0.5wt%) on a Ti/TiN diffusion barrier were used and passivated with different combinations of silicon-oxide/silicon-nitride and different geometries. To account for the interaction metal-passivation FEM calculations have been performed and the formalism of “eigenstrains” has been used to evaluate the voiding and shear plasticity separately.First results show a significant dependence of the strain on the passivating temperature (higher passivating temperature induces higher strain at RT) as well as on the passivation material and geometry. Plastic shear deformation is mostly influenced by the passivation geometry. Passivation composition shows smaller but also visible effects for plasticity whereas alloy composition seems to have no influence on any measured elastic and calculated plastic behavior of the metal lines within the errors.