Modelling the chemical mechanism of the thermal atomic layer etch of aluminium oxide: a density functional theory study of reactions during HF exposure

Show simple item record Kondati Natarajan, Suresh Elliott, Simon D. 2018-08-10T13:53:29Z 2018-08-10T13:53:29Z 2018-08-09
dc.identifier.citation Kondati Natarajan, S. and Elliott, S. D. (2018) 'Modelling the Chemical Mechanism of the Thermal Atomic Layer Etch of Aluminium Oxide: A Density Functional Theory Study of Reactions During HF Exposure', Chemistry of Materials, In Press, doi: 10.1021/acs.chemmater.8b01930 en
dc.identifier.startpage 1 en
dc.identifier.endpage 40 en
dc.identifier.issn 0897-4756
dc.identifier.doi 10.1021/acs.chemmater.8b01930
dc.description.abstract Thermal atomic layer etch, the reverse of atomic layer deposition, uses a cyclic sequence of plasma-free and solvent-free gas-surface reactions to remove ultra thin layers of material with a high degree of control. A theoretical investigation of the hydrogen fluoride pulse in the thermal atomic layer etch of monoclinic alumina has been performed using density functional theory calculations. From experiments, it has been speculated that the HF pulse forms a stable and non-volatile layer of AlF3 on alumina surface. Consistent with this, the desorption of an AlF3 molecule from an HF saturated surface was computed to be energetically unfavourable. HF molecules adsorbed on the alumina surface by forming hydrogen bonds, and either remained intact or dissociated to form Al-F and O-H species. At higher coverages, a mixture of molecularly and dissociatively adsorbed HF molecules in a hydrogen-bonded network was observed. Binding energies converged as the coverage of dissociated F became saturated, consistent with a self-limiting reaction. The formation of H2O molecules in the HF pulse was found to be endothermic with an energy barrier of at least +0.9 eV, but their subsequent desorption was computed to cost as little as +0.2 eV. Based on a model of the saturated Al-F surface, the theoretical maximum of the etch rate was estimated to be -0.57±0.02~Å/cycle (-20.0±0.8 ng/(cm2 cycle)), which matches the range of maximum experimental values. The actual etch rate will, however, be dependent on the specific reagent used in the subsequent step of the atomic layer etch cycle. en
dc.description.sponsorship Lam Research Corporation (Gift funding); Science Foundation Ireland (SFI funded computing cluster at Tyndall national Institute) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher American Chemical Society (ACS) en
dc.rights © 2018 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see en
dc.subject Atomic layer deposition (ALD) en
dc.subject Semiconductor devices en
dc.subject Atomic scale en
dc.subject Atomic layer etch (ALE) en
dc.title Modelling the chemical mechanism of the thermal atomic layer etch of aluminium oxide: a density functional theory study of reactions during HF exposure en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Suresh Kondati Natarajan, Tyndall Micronano Electronics, University College Cork, Cork, Ireland. +353-21-490-3000 Email: en
dc.internal.availability Full text available en Access to this article is restricted until 12 months after publication by request of the publisher. en 2019-08-09 2018-08-10T13:40:32Z
dc.description.version Accepted Version en
dc.internal.rssid 449007629
dc.contributor.funder Lam Research Corporation en
dc.contributor.funder Science Foundation Ireland en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Chemistry of Materials en
dc.internal.copyrightchecked No !!CORA!! en
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress en

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