The scaling of electromigration lifetimes

The reduction of electromigration failure times with scaling presents a critical challenge for continued technology development. Electromigration failure is determined by void morphology and Cu drift velocity. Using observations of changes in these parameters, particularly the increase in drift velocity due to the increasingly polycrystalline Cu grain structure, we are able to accurately model trends in failure times between the 65 and 20 nm nodes. Below 20 nm failure times will continue to decrease, but at a faster rate at the low percentiles associated with circuit reliability. Metal capping to reduce interfacial diffusion of Cu has no impact on the drift velocity at the most advanced technology nodes. Control of Cu grain structure and development of electromigration resistant Cu alloys provide the most effective means of improving electromigration performance.