Electromigration Characteristics and Morphological Evolution of Cu Interconnects on CVD Co and Ru Liners for 10-nm Class VLSI Technology

Ruthenium (Ru) and cobalt (Co) are new candidates for the replacement of physical vapor deposition tantalum (Ta) in liner materials because Ru and Co have excellent Cu-filling properties when deposited using chemical vapor deposition (CVD). Under accelerated current stressing conditions, Cu interconnects on a TaN/Co barrier showed an abrupt increase in resistance. The Cu resistance on a TaN/Ru barrier increased gradually and saturated with low deviation because voids generated randomly, and the Cu that remained on the Ru in the voids acted as shunt layers, preventing a sudden increase in resistance. Cu evolution tests on a Ru liner indicated that Cu had a strong bond with CVD Ru liner, even at high temperatures. These results suggest that Cu deposited on a TaN/Ru barrier can endure electromigration failure.