Strain Analysis in Fine Al Interconnections by X-Ray Diffraction Spectrometry Using Micro X-Ray Beam

Abstract
An energy dispersive diffraction X-ray spectrometer with a sub-micron X-ray beam is developed to analyze crystalline structures in micro-regions of ULSIs. It is used to analyze strain in fine Al interconnections. The strain (ε) in lines with Al single-layer structures showed a dependence on the line width (W)=ε -0.8 at W below 1.5 µ m. The origin of these strains is mainly intrinsic stress in Al films and thermal stress caused by differences in the coefficients of thermal expansion between Al and Si. Introducing barrier metals reduces the dependence of strain in an Al layer on the line width.

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