Local Strains Measured in Al Lines During Thermal Cycling and Electromigration Using Convergent-beam Electron Diffraction

Abstract

In situ local measurement of sub-threshold strains generated during the electromigration of a 0.3-μm-wide Al interconnect was performed for the first time using convergent-beam electron diffraction (CBED) in a transmission electron microscope (TEM). Thermal strains were also analyzed and provided verification for the electromigration analysis. Spatially averaged strains resulting from thermal cycling and electromigration quantitatively agree with models and data from previous studies. However, the local strains exhibited variations as large as 2 × 10−3. After eliminating other possible mechanisms, the strain inhomogeneity is attributed to local plasticity through source-limited dislocation activity.