Local textures and grain boundaries in voided copper interconnects

Abstract

We have characterized grain boundary structures and local textures in stress voided copper lines. Grain boundary misorientations as well as the tilt and twist character of boundaries were measured using electron backscatter diffraction in the scanning electron microscope in conjunction with focused ion beam images. We have summarized data for a number of boundaries immediately adjacent to voids and made comparisons to boundaries from regions that remained intact. These data were acquired from the same lines, and so represent measurements from material with identical histories. Significant local variations in microstructure were observed. Local textures of grains near voids were of lower strength than those away from voids. Grain boundaries intersecting voids were of higher angle character and had significant twist components. These results suggest that local regions associated with more favorable kinetics are more susceptible to void formation and growth.