Grain boundary misorientation angles and stress-induced voiding in oxide passivated copper interconnects

Grain boundary misorientations were determined by electron backscattering diffraction for tantalum-encapsulated, copper interconnects which contained thermal-stress-induced voids. The misorientation angles at voided and unvoided line segments were analyzed for two differently heat treated sample types, which were not equally susceptibile to stress voiding. Unvoided line segments contained a larger percentage of low misorientation angle, lower diffusivity boundaries than regions adjacent to voids. In addition, the more void resistant sample type also contained an overall higher proportion of low misorientation angle boundaries than the sample type which exhibited more voiding. The data provide further support for the importance of local variations in microstructure, which control the kinetics of stress void formation and growth.