Comparison of electromigration failure rates and grain boundary kinetics in aluminum lines and films

Electromigration failure times for aluminum-1% silicon interconnects, (0.8 μm thick and linewidths of 3–4 μm) were used to develop a self-consistent thermodynamic treatment of the kinetic process controlling the failure rate. The results imply a power law relationship exists between the driving force and the failure rate, rather than the linear relationship predicted by basic electromigration flux theory. Additionally, the rate controlling process is predicted to require the coordinated motion of multiple atoms, rather than that of individual vacancy diffusion.; Evolution of the grain structure during electromigration testing was evaluated for interconnects with-and without an impressed current. The grain structure and the behavior of individual grain boundaries for these aluminum films were evaluated by generating images that revealed the individual grains within the aluminum. These images were obtained using a dual beam FEI 620 Focused Ion Beam scanning electron microscope (FIB), which relies on differences in ion channeling between grain orientations to develop contrast in the secondary electron signal due to ion bombardment.; Significant microstructural evolution was observed in regions exhibiting typical electromigration induced damage of void nucleation and growth. No significant changes to the basic microstructure of the interconnects was observed in regions away from the damage sites nor in the interconnects without an impressed current. These observations suggest the microstructural evolution was not solely driven by thermal activation, but possessed a contribution from the impressed current or electric field. In each case, the microstructural development resulted in void nucleation and growth. It was concluded, interactions between the applied field and the aluminum's microstructure contributed to localized microstructural evolution that resulted in void nucleation and growth.