Electromigration performance of multilevel interconnect vias is investigated using a three-dimensional computer model. The model uses the finite-element method to obtain self-consistently the temperature and current density distributions in order to calculate electromigration fluxes. The model includes the polycrystalline grain structure of the tracks as well as stress-migration and concentration gradient backfluxes. While in single level systems, failure can be analyzed with two-dimensional models because the fluxes are homogeneous, the inclusion of the third dimension along the track thickness is necessary for multilevel systems. In addition to the effects of hot spots, current crowding, and microstructure, it is found that the anisotropy of the grain boundary diffusion plays an important role in determining the locations of void formation. The microstructural details of the track at the interface with the via, including grain boundary geometry, are very important for electromigration studies. ©1997 American Institute of Physics.