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Atomic layer deposition of transition metals

Nature Materials volume 2, pages 749–754 (2003)Cite this article

Abstract

Atomic layer deposition (ALD) is a process for depositing highly uniform and conformal thin films by alternating exposures of a surface to vapours of two chemical reactants. ALD processes have been successfully demonstrated for many metal compounds, but for only very few pure metals. Here we demonstrate processes for the ALD of transition metals including copper, cobalt, iron and nickel. Homoleptic N,N′-dialkylacetamidinato metal compounds and molecular hydrogen gas were used as the reactants. Their surface reactions were found to be complementary and self-limiting, thus providing highly uniform thicknesses and conformal coating of long, narrow holes. We propose that these ALD layers grow by a hydrogenation mechanism that should also operate during the ALD of many other metals. The use of water vapour in place of hydrogen gas gives highly uniform, conformal films of metal oxides, including lanthanum oxide. These processes should permit the improved production of many devices for which the ALD process has previously not been applicable.

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Figure 1
Figure 2: Data showing that the thicknesses of cobalt films approach a constant (that is, saturated) value as the doses of the precursors are increased.
Figure 3: Data showing that the thicknesses of copper films approach a saturated value as the doses of the precursors are increased.
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Acknowledgements

We thank Jill S. Becker and Philippe P. de Rouffignac for providing WN-coated substrates and for helpful assistance in the film deposition; Damon Farmer for help with the AFM measurements; Ming Mao (Veeco) and Douwe Monsma for making magnetic measurements of the films; and Martin Gutsche (Infineon Technologies) for supplying a wafer with holes with a 40:1 aspect ratio. This work was supported in part by the National Science Foundation (grant no. ECS 9975504).

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  1. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, 02138, Massachusetts, USA

    Booyong S. Lim, Antti Rahtu & Roy G. Gordon

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  1. Booyong S. Lim
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Correspondence to Roy G. Gordon.

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Lim, B., Rahtu, A. & Gordon, R. Atomic layer deposition of transition metals. Nature Mater 2, 749–754 (2003). https://doi.org/10.1038/nmat1000

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