Thermal stability of RuZr alloy thin films as the diffusion barrier in Cu metallization

Thin films of RuZr/Cu stacking were deposited on Si substrates by magnetron sputtering technology. The as-deposited RuZr thin films were amorphous, while Cu thin films were polycrystalline with (1 1 1) preferred orientation. The films were then annealed at given temperatures to evaluate the thermal stability. It was demonstrated that the amorphous state could be maintained up to 450 C and, the inter-diffusion between Cu and Si atoms was effectively suppressed. However, the atom diffusion became significant at higher temperatures and resulted in the formation of high-resistance Cu₃Si phase. So RuZr amorphous alloy thin films can be readily used for Cu metallization, but the working temperature should be not higher than 450 C.