Diffusion barriers performance of amorphous Ta-Zr films in Cu metallization

An amorphous Ta-Zr binary alloy diffusion barrier was studied in the Cu metallization. A Cu/Ta₅₀Zr₅₀/SiO₂/Si stack with 50 nm thick amorphous film was prepared by co-sputtering can effectively suppress the penetration of Cu atoms into substrate upon annealing up to 650 °C. Examining the thermal stability of the barrier revealed that the crystallization of these amorphous Ta₅₀Zr₅₀ films occurred at 800 °C, higher than its failure temperature. The results show that the existence of Cu layer first induced the formation of TaSi₂ and ZrSi₂ crystalline phases at 650 °C, followed by the formation of Cu₃Si. A failure mechanism of the diffusion barrier is proposed based on the relation between thermal stress and the activation energy of barrier/substrate interface reaction.