Improvement of Ta barrier film properties in Cu interconnection by using a non-mass separated ion beam deposition method

Ta/si ( 100) and Cu/Ta/Si ( 100) film structures were fabricated by using ion beam deposition with a modified RF sputter-type ion source, in which a strong RF discharge was introduced in order to enhance the plasma density. For Ta/Si structures, Ta films were deposited at various bias voltages, When the substrate bias voltage was not applied, the Ta film showed a columnar structure and had a high resistivity of 2600 nOmegam. On the other hand, when the substrate bias voltage of -50- - 200 V was applied, the cross-sectional observation did not show columnar structure at all. In this case. film deposition was considered to be sufficient migration energy by the accelerated Ta+ ions. In particular, Ta films deposited at a bias voltage of - 125 V had a very small resistivity of 360 nOmegam. Thermal stability of Cu(100 nm)/Ta(50 nm)/Si films, where Ta plays a role of diffusion barrier, was evaluated after annealing in H-2 atmosphere for 60 min at various temperatures. Non-columnar structure Ta films deposited at substrate bias voltages of -50 V and - 125 V were found to be stable up to 600degreesC, while columnar structure Ta films deposited at zero bias voltage degraded at 300degreesC. This result indicates that the thermal stability of the Ta films is mainly governed by the film microstructure of the deposited layer.