Copper interconnect reliability on integrated circuits

As multilevel interconnection technology is recently adopted in semiconductor industry, copper interconnect reliability becomes one of the most important concerns. In this dissertation, copper interconnects electromigration and time-dependent dielectric breakdown (TDDB) of copper metallization have been studied.; Barrier layer is used in copper metallization because of copper's high diffusion. The barrier layer effect on copper electromigration lifetime has been evaluated by solving continuity equation. Besides preventing the diffusion of copper into dielectric and giving a good adhesion between copper and dielectric, from calculation, the barrier layer can also improve interconnect failure lifetime in some extent.; Thermal effects are becoming more and more important in electromigration reliability as the continuing scaling down of integrated circuits. An analytical model is developed to account for electromigration lifetimes affected by Joule heating under pulsed DC operation. Another analytical model for determining the interconnect temperature under DC stress is also obtained to evaluate thermal effects on electromigration performance for Al/SiO₂, Cu/SiO ₂ and Cu/low-k interconnect systems. The analytical models fit the experimental data very well and can be integrated into the available electromigration simulation tools easily.; As current crowding electromagnetic phenomenon in metal conductor under high frequency, skin effect of on-chip copper interconnects on electromigration is simulated and the results give us the range of frequency in which skin effect on electromigration need to be taken into consideration.; A physical model of TDDB in copper metallization is derived for the first time and this model gives us a clear physical picture of TDDB. The analytical TDDB lifetime solution of Cu ion drift and diffusion in dielectric is obtained which can fit the experimental data very well at different electric fields and temperatures with only a few physical parameters. The diffusion activation energy is independent on electric field and the electric field acceleration factor depends only on the structure characteristic of dielectric.