Effects of N doping in Ru-Ta alloy barrier on film property and reliability for Cu interconnects

RuTa(N) film has been prepared by doping N in Ru-Ta alloy and investigated its use as a barrier layer against Cu diffusion in Cu interconnects. It was found that RuTa(N) has a poor barrier property against Cu in the BEOL process, since N in Ru-Ta alloy is desorbed and RuTa(N) is recrystallized by heat treatment. It was also shown that RuTa(N) has inferior reliability due to its poor wettability with Cu compared to RuTa. On the other hand, RuTa has both good barrier property and superior reliability performance. It is possible to apply RuTa single film as a barrier layer for Cu interconnects.