Interfaces in copper nanoconnections

Abstract

Experimental characterization and modeling of the reliability of three-terminal dual-damascene Cu interconnect treesDecreasing linewidth in electronics packages leads to structures that have to be described atomistically. Currently copper is among the most interesting materials in electronics due to its electrical and thermal properties. We have developed interatomic potentials to model interfaces in copper metallization. Currently an embedded-atom method potential for a Cu-Ta system and a modified embedded-atom method potential for a Ta-Si system are available. We have used the molecular dynamics method with these potentials to study the energy and microstructure of several low-index Cu-Ta and Ta-Si interfaces. Yield stress of the Cu-Ta system is correlated with the energy of the interface. In addition, more realistic Cu-Ta interfaces are generated by depositing copper atoms on a tantalum surface and tantalum atoms on copper surfaces. Tantalum atoms are seen to mix on copper surfaces, while copper atoms stay on tantalum surfaces. We discuss this with bonding energy arguments.

Surface diffusion of copper on tantalum substrates by Ostwald ripening

“…13). The tantalum substrate is still covered by copper because the Ta-Cu interaction is stronger than Cu-Cu: E TaCu < E CuCu < 0 [24]. The relevance of the diffusion mechanism b is corroborated by the fact that surface diffusion coefficients are substrate dependant, which points to the involvement of the tantalum surface.…”

The influence of liners with Ti, Ta or Ru finish on thin Cu films

“…In [32], the interface energy between different faces of Ta, probably a-Ta, and Cu has been calculated. On all Ta faces, Cu(1 1 1) is energetically favored over the other orientations.…”

Molecular Dynamics Study on Enhanced Cu Coverage of Trench Filling with Low-Index Ta Surfaces

“…5(b) and 7(b). After the Cu film is formed, as the binding energy of Cu-Ta is much higher than that of Cu-Cu, 22) the uniform single-layer Cu film can be maintained. Consequently, the Cu adatoms are easily bonded onto the Cu film with a less uniform configuration because the surface diffusion coefficient of Cu/Ta is higher (by nearly six orders of magnitude) than that of Cu/Cu self-diffusion.…”