Impact of interfacial chemistry on adhesion and electromigration in Cu interconnects

The impact of etch-stop (ES)/Cu interfacial chemistry on adhesion and electromigration (EM) has been systematically investigated by varying Cu surface chemistry, etch-stop film chemistry, metal capping layers, and thermal annealing conditions. Adhesion and EM improvement directly correlate with reducing interfacial oxygen for all the systems studied. While the adhesion of freshly deposited ES films strongly depends on the Cu surface chemistry and ES deposition conditions, the hermeticity of the ES film significantly impacts the film and interface chemistry during subsequent processing and thermal cycles, consequently affecting the long term stability of adhesion and electromigration performance. The mechanism for the correlation and material properties governing the interfacial chemistry will be discussed.