Etectromigration reliability of damascene copper interconnects

Basic electromigration characteristics have been investigated in passivated single-damascene Cu lines. The results indicated that there was a significant incubation time for resistance change, as measured by extrapolated change in resistance. The observed critical product was about 5900A/cm. The activation energy of diffusion was found to be 0.89+/-0.07eV The results indicate that the activation energy of the Cu/SiNx interface diffusion is similar to unpassivated Cu surface diffusion. However, the SiNx passivation interface significantly decrease drift velocity compared to reported values of unpassivated samples. The diffusion path and critical product are not influenced under pulsed current stress. Cu/SiN interface diffusion is dominant even tinder 1 MHz pulsed current stress.