Multiple proton diffusion and film densification in atomic layer deposition modeled by density functional theory

Simple item page
dc.contributor.authorShirazi, Mahdi
dc.contributor.authorElliott, Simon D.
dc.contributor.funderHigher Education Authorityen
dc.contributor.funderScience Foundation Irelanden
dc.date.accessioned2016-03-08T17:27:26Z
dc.date.available2016-03-08T17:27:26Z
dc.date.issued2013-02-28
dc.date.updated2015-04-13T16:00:02Z
dc.description.abstractTo investigate the atomic layer deposition (ALD) reactions for growth of HfO2 from Hf(NMe2)4 (TDMAHf) andH2O, a density functional theory (DFT) slab model was employed. We inspected all energy steps, from the early stage of adsorption of each ALD precursor to the densification of multiple atoms into bulk-like HfO2 layers. The activation energy calculations show that repeated proton diffusion from the surface to amide ligands and rotation of the protonated amine is more energetically accessible than the simple elimination of the amine in the initial stage. We therefore propose that multiple protons diffuse to the amide ligands of the Hf precursor before desorption of protonated ligands takes place. Loss of a proton from surface oxygen frees it up for bonding to Hf of the precursor. Protonation of ligands, and especially desorption of ligands, frees up Hf for bonding to surface oxygen. These effects are termed “densification”, as they bring Hf−O packing closer to the bulk scenario. Densification is associated with substantial release of energy. During the metal pulse, saturation of the surface by remaining fragments HfX causes adsorption of further metal precursor to stop. The presence of these fragments prevents further chemisorption of HfX4, since this requires the creation of a strong dative bond between Hf and O. Next, during the H2O pulse, Hf exchanges its remaining ligands with OH groups. The exchange occurs due to the decomposition of adsorbed H2O molecules in clusters of HfX. Decomposition of H2O when adsorbed onto a (Hf(NMe2))x (x ≥ 2) cluster (e.g., dimers) also increases the coordination of Hf and O. Simultaneously, low-coordinated oxygen atoms appear at the surface, which are reactive sites for the next metal pulse. With saturation of the surface by OH groups, H2O molecules begin to appear. This detailed description of ALD chemistry allows us to make qualitative predictions about how the process depends on temperature. The data can also be inputted into kinetic simulations for a quantitative view of the complex film growth process.en
dc.description.sponsorshipScience Foundation Ireland (SFI strategic research cluster “Functional Oxides and Related Materials for Electronics” (FORME)); Higher Education Authority (SFI/HEA Irish Centre for High-End Computing (ICHEC))en
dc.description.statusPeer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationSHIRAZI, M. & ELLIOTT, S. D. 2013. Multiple Proton Diffusion and Film Densification in Atomic Layer Deposition Modeled by Density Functional Theory. Chemistry of Materials, 25, 878-889. http://dx.doi.org/10.1021/cm303630een
dc.identifier.doi10.1021/cm303630e
dc.identifier.endpage889en
dc.identifier.issn0897-4756
dc.identifier.issued6en
dc.identifier.journaltitleChemistry of Materialsen
dc.identifier.startpage878en
dc.identifier.urihttps://hdl.handle.net/10468/2422
dc.identifier.volume25en
dc.language.isoenen
dc.publisherAmerican Chemical Societyen
dc.rights© 2013 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 http://dx.doi.org/10.1021/cm303630een
dc.subjectDFTen
dc.subjectDensity functional theoryen
dc.subjectALDen
dc.subjectAtomic layer depositionen
dc.subjectKMCen
dc.subjectKinetic Monte Carloen
dc.subjectMetal oxideen
dc.subjectMetal alkylamide precursoren
dc.subjectMultiple proton diffusionen
dc.subjectDensificationen
dc.subjectActivation energyen
dc.subjectDissociationen
dc.subjectAdsorptionen
dc.titleMultiple proton diffusion and film densification in atomic layer deposition modeled by density functional theoryen
dc.typeArticle (peer-reviewed)en
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Shirazi_Elliott_ChemMater_25_878_2013_submitted.pdf
Size:
7.63 MB
Format:
Adobe Portable Document Format
Description:
Accepted Version
Download
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
license.txt
Size:
2.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Tyndall National Institute - Journal Articles