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

•The crystallization of Ru thin films can be suppressed by Zr doping.•Amorphous RuZr thin films were fabricated by magnetron sputtering.•It could be used to effectively suppress the diffusion between Cu and Si.

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.