Self-Assembled Nano-Stuffing Structure in CVD and ALD Co(W) Films as a Single-Layered Barrier/Liner for Future Cu-Interconnects

摘要

Cobalt film with tungsten [Co(W)] has the potential to be an effective single-layered barrier/liner in interconnects, due to its good adhesion with Cu, low resistivity compared with TaN, and comparable barrier properties to TaN. To reduce the resistivity of Co(W), oxygen-free Co(W) was fabricated from oxygen-free precursors, bis(N-tert-butyl-N'-ethylpropionamidinato) cobalt and bis(tert-butylimino)bis(dimethylamino) tungsten, by chemical vapor deposition (CVD) and atomic layer deposition (ALD). Our results showed that W addition improved the barrier properties of both CVD-Co(W) and ALD-Co(W) against Cu diffusion. The diffusion coefficient of Cu in Co(W) was reduced by W addition. The activation energy of Cu in CVD-Co(W) and ALD-Co(W) was 1.5 eV and 1.7-1.8 eV, respectively; whereas that in CVD-Co was 1.0 eV. Improvement in the barrier properties of Co(W) was attributed to the amorphous-like structure created by W. High-resolution transmission electron microscopy and multivariate spectral analysis of the nanoscale properties of Co(W) revealed that the improvement in the barrier properties was due to the self-assembled segregation of W atoms at the grain boundary. The segregated W atoms in both CVD-Co(W) and ALD-Co(W) films may act as a stuffing material. These results suggest Co(W), especially ALD-Co(W), as a promising material for Cu-interconnects in future ultra-large-scale integrated circuits.