A study on the electrodeposition of Cu and Cu-Ag alloy films for device interconnect - Engineering Information Institute

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A study on the electrodeposition of Cu and Cu-Ag alloy films for device interconnect [CET 2015]
Author(s)
Kang O Kim
ABSTRACT
Adopting Cu interconnect instead of Al interconnect was one of the most significant changes in Si-based microelectronic device manufacturing industry. The merits of Cu interconnect are superior electrical and thermal properties and large resistance to electromigration in comparison with Al interconnect. Hydrometallurgical Cu metallization by electrodeposition in an aqueous electrolyte has become a primary technique in fabricating Cu interconnect. In the present study, we deal with the electrodeposition of Cu and Cu-Ag alloy thin films on dc-sputter-deposited W and atomic-layer-deposited (ALD) WNx as diffusion barrier layer. Cu-Ag alloy interconnect has been recently developed from the dimensional limitation of pure Cu interconnect. Although Cu seed layer has been widely used in the current industry, we carried out seedless electrodeposition to avoid poor step coverage in high-aspect-ratio or sub-45-nm interconnect features. We initially investigated morphological characteristics of Cu-based films according to potential, pH, and electrolyte compo-sition. The electrolyte contains complexing agent and additives to control the nucleation, surface morphology, and thickness uniformity of the Cu-based films formed on the W and WNx surface. Finally, optimized electrodeposition parameters for thin, uniform Cu and Cu-Ag alloy films were used to form sub-30-nm wide Cu (and Cu-Ag alloy) interconnect lines by filling sub-30-nm trenches.
KEYWORDS
electrodeposition, Cu and Cu-Ag alloy films, device interconnect
References

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