Finite element analysis of electromigration reliability in copper chip interconnect

To discuss the electromigration reliability of the copper chip interconnect, a transient non-linear dynamic and electrical finite element framework was developed. The simulation includes two major areas: one is the impact of the electromigration caused by current density and another one is the stress-migration relate to thermal-stress distribution in Cu interconnects. It was found that compared with Al interconnects, the electromigration is much slower and the thermal stress is higher in Cu interconnects. Among the 2-via-blech-structure, the first main stress reaches the maximum value inside the via, and reaches the minimum value above and underneath the via right inside the wire metal. The simulation results indicate that the first main stress increases as the via angle increasing and the first main stress reaches its peak value when the via diameter is 350 nm.