Study on the amorphous Ta-Zr films as diffusion barrier in Cu metallization

An amorphous Ta-Zr binary alloy diffusion barrier was studied in the Cu metallization. A Cu Ta50 Zr50 Si stack with 50 nm thick amorphous film was prepared by cosputtering 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 Ta50 Zr50 films occurred at 800 °C, higher than its failure temperature. The results show that the existence of Cu layer first induced the formation of Ta Si2 and Zr Si2 crystalline phases at 650 °C, followed by the formation of Cu3 Si. A failure mechanism of the diffusion barrier is proposed based on the relation between the thermal stress and the activation energy of barrier/substrate interface reaction.