Self-limiting temperature window for thermal atomic layer etching of HfO2 and ZrO2 based on the atomic-scale mechanism

Show simple item record Mullins, Rita Kondati Natarajan, Suresh Elliott, Simon D. Nolan, Michael 2021-05-11T13:17:33Z 2021-05-11T13:17:33Z 2020-04-02
dc.identifier.citation Mullins, R., Kondati Natarajan, S., Elliott, S. D. and Nolan, M. (2020) 'Self-limiting temperature window for thermal atomic layer etching of HfO2 and ZrO2 based on the atomic-scale mechanism', Chemistry of Materials, 32(8), pp. 3414-3426. doi: 10.1021/acs.chemmater.9b05021 en
dc.identifier.volume 32 en
dc.identifier.issued 8 en
dc.identifier.startpage 3414 en
dc.identifier.endpage 3426 en
dc.identifier.issn 0897-4756
dc.identifier.doi 10.1021/acs.chemmater.9b05021 en
dc.description.abstract HfO2 and ZrO2 are two high-k materials that are important in the downscaling of semiconductor devices. Atomic-level control of material processing is required for the fabrication of thin films of these materials at nanoscale device sizes. Thermal atomic layer etching (ALE) of metal oxides, in which up to one monolayer of the material can be removed, can be achieved by sequential self-limiting (SL) fluorination and ligand-exchange reactions at elevated temperatures. However, to date, a detailed atomistic understanding of the mechanism of thermal ALE of these technologically important oxides is lacking. In this paper, we investigate the hydrogen fluoride (HF) pulse in the first step in the thermal ALE process of HfO2 and ZrO2 using first-principles simulations. We introduce Natarajan–Elliott analysis, a thermodynamic methodology, to compare reaction models representing the self-limiting (SL) and continuous spontaneous etching (SE) processes taking place during an ALE pulse. Applying this method to the first HF pulse on HfO2 and ZrO2, we found that thermodynamic barriers impeding continuous etching are present at ALE-relevant temperatures. We performed explicit HF adsorption calculations on the oxide surfaces to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively on both oxides by forming metal–F and O–H bonds. HF coverages ranging from 1.0 ± 0.3 to 17.0 ± 0.3 HF/nm2 are investigated, and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. Theoretical etch rates of −0.61 ± 0.02 Å/cycle for HfO2 and −0.57 ± 0.02 Å/cycle for ZrO2 were calculated using maximum coverages of 7.0 ± 0.3 and 6.5 ± 0.3 M–F bonds/nm2, respectively (M = Hf, Zr) en
dc.description.sponsorship Science Foundation Ireland - National Natural Science Foundation of China Partnership Program (NITRALD Grant number: 17/NSFC/5279) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher ACS Publications en
dc.rights © 2020, American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials after technical editing by the publisher. To access the final edited and published work see en
dc.subject Semiconductor devices en
dc.title Self-limiting temperature window for thermal atomic layer etching of HfO2 and ZrO2 based on the atomic-scale mechanism en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Michael Nolan, Tyndall Theory Modelling & Design Centre, University College Cork, Cork, Ireland. +353-21-490-3000 Email: en
dc.internal.availability Full text available en 2021-05-07T11:16:25Z
dc.description.version Accepted Version en
dc.internal.rssid 565254770
dc.contributor.funder Lam Research en
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder National Natural Science Foundation of China en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Chemistry of Materials en
dc.internal.copyrightchecked Yes
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress en
dc.identifier.eissn 1520-5002

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