Ultrathin ZrB_xO_y films as diffusion barriers in Cu interconnects

Ultra-thin ZrB_xO_y films 5 nm in thickness were prepared by radio-frequency (rf) magnetron sputtering. The thermal stability and the barrier performance against the inter-diffusion between Cu and Si were studied via thermal annealing at different temperatures. The as-deposited amorphous ZrB_xO_y thin films could effectively block the inter-diffusion of Cu and Si atoms. However, the thin films became invalid at temperatures higher than 600 °C and significant atomic diffusion occurred, resulting in high-resistivity Cu₃Si compound. Hence, ZrB_xO_y thin films can be exploited as diffusion barriers in Cu interconnects at temperatures lower than 600 °C.