Electromigration-induced microstructure evolution in tin studied by synchrotron x-ray microdiffraction

Under constant current electromigration, white tin exhibited a resistance drop of up to 10%. It has a body-centered-tetragonal structure, and the resistivity along the a and b axes is 35% smaller than along the c axis. Microstructure evolution under electromigration could be responsible for the resistance drop. Synchrotron radiation white beam x-ray microdiffraction was used to study this evolution. Grain-by-grain analysis was obtained from the diffracted Laue patterns about the changes of grain orientation before and after electromigration. We observed that high-resistance grains reorient with respect to the neighboring low-resistance grains, most likely by grain growth of the latter. A different mechanism of grain growth under electromigration from the normal grain growth is proposed and discussed.