Effect of reaction mechanism on precursor exposure time in atomic layer deposition of silicon oxide and silicon nitride

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Murray, Ciarán A.
Elliott, Simon D.
Hausmann, Dennis
Henri, Jon
LaVoie, Adrian
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American Chemical Society
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Atomic layer deposition (ALD) of highly conformal, silicon-based dielectric thin films has become necessary because of the continuing decrease in feature size in microelectronic devices. The ALD of oxides and nitrides is usually thought to be mechanistically similar, but plasma-enhanced ALD of silicon nitride is found to be problematic, while that of silicon oxide is straightforward. To find why, the ALD of silicon nitride and silicon oxide dielectric films was studied by applying ab initio methods to theoretical models for proposed surface reaction mechanisms. The thermodynamic energies for the elimination of functional groups from different silicon precursors reacting with simple model molecules were calculated using density functional theory (DFT), explaining the lower reactivity of precursors toward the deposition of silicon nitride relative to silicon oxide seen in experiments, but not explaining the trends between precursors. Using more realistic cluster models of amine and hydroxyl covered surfaces, the structures and energies were calculated of reaction pathways for chemisorption of different silicon precursors via functional group elimination, with more success. DFT calculations identified the initial physisorption step as crucial toward deposition and this step was thus used to predict the ALD reactivity of a range of amino-silane precursors, yielding good agreement with experiment. The retention of hydrogen within silicon nitride films but not in silicon oxide observed in FTIR spectra was accounted for by the theoretical calculations and helped verify the application of the model.
Silicon nitride , Silicon oxide , Atomic layer deposition , Mechanisms , DFT , Density functional theory , Deposition , Dielectric films , Fourier transform infrared spectroscopy , Functional groups , Dielectric thin films , Micro-electronic devices; , Silicon precursors , Surface reaction mechanism , Theoretical calculations , Thermodynamic energy
MURRAY, C. A., ELLIOTT, S. D., HAUSMANN, D., HENRI, J. & LAVOIE, A. 2014. Effect of Reaction Mechanism on Precursor Exposure Time in Atomic Layer Deposition of Silicon Oxide and Silicon Nitride. ACS Applied Materials & Interfaces, 6, 10534-10541. http://dx.doi.org/10.1021/am5021167
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© 2014 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, 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/am5021167