Ru passivated and Ru doped e-TaN surfaces as combined barrier and liner material for copper interconnects: a first principles study

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dc.contributor.author Kondati Natarajan, Suresh
dc.contributor.author Nies, Cara-Lena
dc.contributor.author Nolan, Michael
dc.date.accessioned 2019-07-22T11:04:53Z
dc.date.available 2019-07-22T11:04:53Z
dc.date.issued 2019-05-21
dc.identifier.citation Kondati Natarajan, S., Nies, C.-L. and Nolan, M. (2019) 'Ru passivated and Ru doped e-TaN surfaces as combined barrier and liner material for copper interconnects: a first principles study', Journal of Materials Chemistry C, 7(26), pp. 7959-7973. doi: 10.1039/C8TC06118A en
dc.identifier.volume 7 en
dc.identifier.issued 26 en
dc.identifier.startpage 7959 en
dc.identifier.endpage 7973 en
dc.identifier.issn 2050-7526
dc.identifier.uri http://hdl.handle.net/10468/8212
dc.identifier.doi 10.1039/C8TC06118A en
dc.description.abstract The reduction of critical dimensions in transistor scaling means that a severe bottleneck arises from the lowest levels of device interconnects. Copper is currently used as an interconnect metal, but requires separate barrier, to prevent Cu diffusion, and liner, to promote Cu deposition, materials. Advanced interconnect technology will require coating of very high aspect ratio trench structures which means that the copper barrier + liner stack should take up only a very small volume of the trench to maintain the low copper resistivity. The current industry standard for Cu diffusion barriers is TaN and Ru is a widely used liner. In this paper we use first principles density functional theory (DFT) computations to explore in detail the interaction of Cu atoms at models of TaN, Ru and combined TaN/Ru barrier/liner materials. This model allows us to explore the role of these materials in Cu adsorption and diffusion (over the surface and into the bulk) at the very early stage of Cu film growth. As a benchmark we studied the behaviour of Cu and Ru adatoms at the low index surfaces of ε-TaN, and the interaction of Cu adatoms with the (0 0 1) surface of hexagonal Ru. These results confirm the barrier and liner properties of TaN and Ru, respectively, while also highlighting the weaknesses of both materials. We then investigate the adsorption and diffusion of Cu adatoms at Ru-passivated and Ru-doped ε-TaN(1 1 0) surfaces. Ru passivated TaN enhances the binding of Cu adatoms compared to the bare TaN and Ru surfaces. On the other hand, the activation energy for Cu diffusion at the Ru passivated TaN surface is lower than that on the bare TaN surface which may promote Cu agglomeration. For Ru-doped TaN we find a decrease in Cu binding energy. In addition, we find favourable migration of the Cu adatoms toward the doped Ru atom, compared with unfavourable migration of Cu away from the Ru site, into the bulk. This suggests that Ru doping sites on the TaN surface can act as nucleation points for Cu growth with high activation energies for agglomeration and can promote electroplating of Cu. Therefore we propose Ru-doped TaN as a candidate for a combined barrier/liner material which will have reduced thickness compared to individual barrier/liner material stacks. en
dc.description.sponsorship Science Foundation Ireland - National Natural Science Foundation of China Partnership (NITRALD 17/NSFC/5279) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Royal Society of Chemistry en
dc.rights © 2019, the Authors. Published by the Royal Society of Chemistry. All rights reserved. en
dc.subject Ru-doped TaN en
dc.subject Barrier/liner material en
dc.subject Nucleation en
dc.subject Cu growth en
dc.subject Agglomeration en
dc.subject Electroplating of Cu en
dc.title Ru passivated and Ru doped e-TaN surfaces as combined barrier and liner material for copper interconnects: a first principles study 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: michael.nolan@tyndall.ie en
dc.internal.availability Full text available en
dc.check.info Access to this article is restricted until 12 months after publication by request of the publisher. en
dc.check.date 2020-05-21
dc.date.updated 2019-07-22T10:39:58Z
dc.description.version Accepted Version en
dc.internal.rssid 493777478
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 Journal of Materials Chemistry C en
dc.internal.copyrightchecked Yes
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress michael.nolan@tyndall.ie en


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