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

dc.check.infoAccess to this article is restricted until 12 months after publication by request of the publisher.en
dc.contributor.authorKondati Natarajan, Suresh
dc.contributor.authorElliott, Simon D.
dc.contributor.funderLam Research Corporationen
dc.contributor.funderScience Foundation Irelanden
dc.description.abstractThermal 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.sponsorshipLam Research Corporation (Gift funding); Science Foundation Ireland (SFI funded computing cluster at Tyndall national Institute)en
dc.description.statusPeer revieweden
dc.description.versionAccepted Versionen
dc.identifier.citationKondati 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.8b01930en
dc.identifier.journaltitleChemistry of Materialsen
dc.publisherAmerican 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
dc.subjectAtomic layer deposition (ALD)en
dc.subjectSemiconductor devicesen
dc.subjectAtomic scaleen
dc.subjectAtomic layer etch (ALE)en
dc.titleModelling the chemical mechanism of the thermal atomic layer etch of aluminium oxide: a density functional theory study of reactions during HF exposureen
dc.typeArticle (peer-reviewed)en
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
3.9 MB
Adobe Portable Document Format
Accepted version
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
2.71 KB
Item-specific license agreed upon to submission