Thermal stability of ultra thin Zr-B-N films as diffusion barrier between Cu and Si

Amorphous Zr-B-N thin films were prepared on Si substrates by DC reactive magnetron sputtering as diffusion barriers for advanced Cu interconnection. To evaluate its thermal stability and barrier performance, Cu/Zr-B-N/Si stacked structures were annealed in high vacuum at temperatures varying from 500 °C to 700 °C for 30 min. The Zr-B-N films remained amorphous after annealing at 600 °C and crystalized at 650 °C, effectively block the intermixing of Cu and Si atoms. However, the thin films became invalid after annealing at 700 °C and high-resistivity Cu₃Si compounds formed, revealing the significant atomic diffusion between Cu and Si. The excellent barrier performance and high thermal stability of Zr-B-N is attributed to the stable amorphous structure. Therefore, the amorphous Zr-B-N thin film can be exploited as a promising diffusion barrier for Cu interconnect technology.