It was noted that electromigration in thin metal films produced internal stresses. Elastic anisotropy could produce a distinct gradient of these stresses across the grain boundary if adjacent grains had differing orientations relative to the grain boundary and to the substrate. The stress gradient then gave rise to a driving force for grain boundary migration. The driving force was proportional to the crystal anisotropy parameter and to the dilatation that was caused by electromigration. At typical values of the parameters, the driving force was comparable to the driving force which was caused by the curvature when the radius of curvature was equal to about 10. The anisotropy driving force could cause low-temperature recrystallization; especially in regions where the internal stresses were near to the threshold value or exceeded it. This could lead to an increase in the number of symmetrical grain boundaries, during electromigration, in the near-anode zone of interconnect lines.

A.Katsman, L.Klinger, L.Levin: Scripta Materialia, 1997, 36[4], 489-93