Mechanism for the atomic layer deposition of copper using diethylzinc as the reducing agent – a density functional theory study using gas phase molecules as a model

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Dey, Gangotri
Elliott, Simon D.
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We present theoretical studies based on first-principles density functional theory calculations for the possible gas-phase mechanism of the atomic layer deposition (ALD) of copper by transmetalation from common precursors such as Cu(acac)(2), Cu(hfac)(2), Cu(PyrIm(R))(2) with R = (i)Pr and Et, Cu(dmap)(2), and CuCl(2) where diethylzinc acts as the reducing agent. An effect on the geometry and reactivity of the precursors due to differences in electronegativity, steric hindrance, and conjugation present in the ligands was observed. Three reaction types, namely, disproportionation, ligand exchange, and reductive elimination, were considered that together comprise the mechanism for the formation of copper in its metallic state starting from the precursors. A parallel pathway for the formation of zinc in its metallic form was also considered. The model Cu(I) molecule Cu(2)L(2) was studied, as Cu(I) intermediates at the surface play an important role in copper deposition. Through our study, we found that accumulation of an LZnEt intermediate results in zinc contamination by the formation of either Zn(2)L(2) or metallic zinc. Ligand exchange between Cu(II) and Zn(II) should proceed through a Cu(I) intermediate, as otherwise, it would lead to a stable copper molecule rather than copper metal. Volatile ZnL(2) favors the ALD reaction, as it carries the reaction forward.
Copper atomic layer deposition , Diethylzinc , Reducing agent , Density functional theory
Dey, G and Elliott, S. D. (2012). Mechanism for the atomic layer deposition of copper using diethylzinc as the reducing agent – a Density Functional Theory study using gas phase molecules as a model. Journal of Physical Chemistry A, 116 (35), pp 8893–8901. DOI: 10.1021/jp304460z
© 2012, American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of Physical Chemistry A, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see