Wei-Hsun Chen¹, Congying Wang², John Blendell², Carol Handweker²; ¹ASML, ²Purdue University

Recrystallization has been reported as one of the whiskers nucleation mechanisms in Sn films. This talk focuses on the evolution of the orientation, dislocation densities, and subsurface microstructure in the defect regions via combined analysis of X-ray synchrotron microdiffraction, FIB, and EBSD before and after thermal cycling. We prepared large-grain Sn-alloy films to simplify the local stress states and observed: (1)whiskers grew from recrystallized grains at one GB, and (2)grain boundary sliding at the other GB. The elastic strain energy density and the geometrically necessary dislocation (GND) densities decreased at both GBs, indicating a dislocation-related stress relaxation mechanism. One low-angle GB formed near the sliding region with shallow grain microstructure. This work provides direct evidence of recrystallization as the mechanism for whisker formation by nucleating shallow surface grains. The local deformation showed a strong dependence on initial orientation, dislocations, and subsurface microstructure.