Kinetics and coverage dependent reaction mechanisms of the copper atomic layer deposition from copper dimethylamino-2-propoxide and diethylzinc
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Accepted Version
Date
2016-08-11
Authors
Maimaiti, Yasheng
Elliott, Simon D.
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Published Version
Abstract
Atomic layer deposition (ALD) has been recognized as a promising method to deposit conformal and uniform thin film of copper for future electronic devices. However, many aspects of the reaction mechanism and the surface chemistry of copper ALD remain unclear. In this paper, we employ plane wave density functional theory (DFT) to study the transmetalation ALD reaction of copper dimethylamino-2-propoxide [Cu(dmap)2] and diethylzinc [Et2Zn] that was realized experimentally by Lee et al. [ Angew. Chem., Int. Ed. 2009, 48, 4536−4539]. We find that the Cu(dmap)2 molecule adsorbs and dissociates through the scission of one or two Cu–O bonds into surface-bound dmap and Cu(dmap) fragments during the copper pulse. As Et2Zn adsorbs on the surface covered with Cu(dmap) and dmap fragments, butane formation and desorption was found to be facilitated by the surrounding ligands, which leads to one reaction mechanism, while the migration of ethyl groups to the surface leads to another reaction mechanism. During both reaction mechanisms, ligand diffusion and reordering are generally endothermic processes, which may result in residual ligands blocking the surface sites at the end of the Et2Zn pulse, and in residual Zn being reduced and incorporated as an impurity. We also find that the nearby ligands play a cooperative role in lowering the activation energy for formation and desorption of byproducts, which explains the advantage of using organometallic precursors and reducing agents in Cu ALD. The ALD growth rate estimated for the mechanism is consistent with the experimental value of 0.2 Å/cycle. The proposed reaction mechanisms provide insight into ALD processes for copper and other transition metals.
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Keywords
Density-functional theory , Minimum energy paths , Elastic band method , Amidinate precursor , Molecular-dynamics , Surface-chemistry , Hydrogen plasma , Reducing agent , 1st principles , Saddle-points
Citation
Maimaiti, Yasheng; Elliott, Simon D. (2016) 'Kinetics and coverage dependent reaction mechanisms of the copper atomic layer deposition from copper dimethylamino-2-propoxide and diethylzinc'. Chemistry Materials, 28 (17) :6282-6295. doi: 10.1021/acs.chemmater.6b02522
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Copyright
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.6b02522