Electromigration performance of multi-level damascene copper interconnects

Electromigration in 0.28-micron (um) wide and 0.3um thick multi-level damas cene copper (Cu) interconnects with tungsten (W) studs via's have been inve stigated. Void growth at the cathode end of the lower line has been found a s a result of electromigration. The dominant void for electromigration life time grows from the Cu/Via interface and grows along the Cu/SiNx interface. The activation energy of electromigration lifetime has been found to be 0. 94 +/-0.11 eV, and the current density exponent 'n' has been found to be 2. 03 +/-0.21. The structures in this study exhibit an incubation period of vo id nucleation. This was observed using the scanning transmission electron m icroscope (S -TEM) technique. From the investigation, influences of process fluctuation (e.g. lithography misalignment) on this growth have been found. The results suggest a guide of process controls specific to damascene Cu interconnects. (C) 2001 Elsevi er Science Ltd. All rights reserved.