A comprehensive study of electromigration in pure Sn: Effects on crystallinity, microstructure, and electrical property

The literature has accumulated plenty of interesting findings of electromigration-induced phenomena in pure Sn. Most of the researches revealed the thermodynamically steady states of materials under electromigration. We presented a comprehensive study of electromigration in pure Sn at 5.5-7.5 × 103 A/cm2 for 5.5 h revealing the effects on crystallinity, microstructure, and electrical property. The present work provided a divergent explanation about the electrical property variation under electromigration by introducing the crystallinity change aspect, as evidenced by the in situ synchrotron X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) investigations. The in situ XRD analysis showed an integrated intensity decline of diffraction peaks (up to a 90% reduction rate) and the buildup of lattice strain (up to 0.68% beyond the yield point) within the Sn matrix, revealing a crystallinity degradation phenomenon under electromigration. The atomic-scale lattice appearance showed direct evidence of dislocation production under electromigration as a result of the plastic deformation. The introduction of dislocations formed sub-lattices with various crystal orientations that were responsible for the integrated intensity decline. The increase in electrical resistance after the electromigration experiment corresponded to the consequences of the observed lattice disruption and lattice strain accumulation phenomena. The thermal benchmark experiments evidenced the predominant athermal electromigration effect, rather than the thermal one, on the crystallinity and electrical resistance responses to electromigration.