Cu surface treatment influence on Si adsorption properties of CuSiN self-aligned barriers for sub-65 nm technology node

Self-aligned barriers are widely investigated either in replacement of dielectric liners to decrease the total interconnect k value or as a treatment prior standard dielectric barrier deposition to improve reliability performances. In this paper, a technique based on the modification of the Cu surface is proposed. It consists first in removing native Cu oxide, then, enriching Cu surface with Si atoms followed by a nitridation step to complete the so called CuSiN self-aligned barrier. The dependency of Cu surface silicidation on Cu crystallographic orientation is described, evidencing two silicidation mechanisms: Si interstitial incorporation into Cu and Cu atoms substitution by Si atoms. He diluted in H 2 cleaning plasma prior to silicidation is demonstrated both to decrease Cu grain surface ability to silicidation compared H 2 plasma and to limit Si incorporation into Cu at grain boundaries. Compared to a standard SiCN barrier, CuSiN self-aligned barriers integrated as a treatment prior to SiCN evidenced at least four times longer lifetime under electromigration tests.