ELECTROMIGRATION CHARACTERISTICS OF COPPER INTERCONNECTS

The electromigration characteristics of electroless plated copper inte rconnects have been investigated under dc and time-varying current str essing. A novel scheme was reported for selective electroless Cu plati ng by using 150-angstrom Co as the seeding layer. The Cu dc and pulse- dc lifetimes are found to be one and two orders of magnitude longer th an that of Al-4%Cu/TiW and Al-2%Si interconnects at 275-degrees-C, and the extracted Cu lifetime at 75-degrees-C is about three and five ord ers of magnitude longer than that of Al-4%Cu/TiW and Al-2%Si, respecti vely. As previously reported for Al metallization, the Cu bipolar life times were found to be orders of magnitude longer than their dc lifeti mes under the same peak stressing current density because of the parti al recovery of electromigration damage during the opposing phases of b ipolar stressing.