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 H2 cleaning plasma prior to silicidation is demonstrated both to decrease Cu grain surface ability to silicidation compared H2 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.