Low-temperature chemical vapor deposition and scaling limit of ultrathin Ru films

Wang, Q.; Ekerdt, John G.; Gay, D.; Sun, Yongchao; White, J. M.

doi:10.1063/1.1650044

Cited by 51 publications

(41 citation statements)

References 7 publications

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“…For instance, a Ru layer requires a minimum optimized thickness <5 nm for a barrier/seed bilayer in copper interconnects and <2.5 nm for a capping layer in EUVL optics. 20,21,22 To study the growth of such an ultrathin Ru film, a technique that allows an accurate control of the initial growth stages is needed, including an accurate determination of the thickness where the layer closes. The limited availability of techniques for in situ monitoring thin film growth in the sub-and nanometre scales has turned out to be a problem.…”

Section: Introductionmentioning

confidence: 99%

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Ribera

Kruijs

Sturm

et al. 2016

Journal of Applied Physics

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In vacuo high-sensitivity low energy ion scattering (HS-LEIS) has been used to investigate the initial growth stages of DC sputtered Ru on top of Si, SiN and SiO2. The high surface sensitivity of this technique allowed an accurate determination of surface coverages and thicknesses required for closing the Ru layer on all three substrates. The Ru layer closes (100% Ru surface signal) at about 2.0, 3.2 and 4.7 nm on top of SiO2, SiN and Si, respectively. In-depth Ru concentration profiles can be reconstructed from the Ru surface coverages when considering an error function like model. The large intermixing (4.7 nm) for the Ru-on-Si system is compared to the reverse system (Si-on-Ru), where only 0.9 nm intermixing occurs. The difference is predominantly explained by the strong Si surface segregation that is observed for Ru-on-Si. This surface segregation effect is also observed for Ru-on-SiN, but is absent for Ruon-SiO2. For this last system, in vacuo HS-LEIS analysis revealed surface oxygen directly after deposition, which suggests an oxygen surface segregation effect for Ru-on-SiO2. In vacuo XPS measurements confirmed this hypothesis based on the reaction of Ru with oxygen from the SiO2, followed by oxygen surface segregation.

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Section: Introductionmentioning

confidence: 99%

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Ribera

Kruijs

Sturm

et al. 2016

Journal of Applied Physics

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“…. Furthermore, the surface conditions of the underlayer are determined by the precursor ligands, and may also affect N. Although Ru is reported to be sufficiently noble to prevent contamination at the interface with the CVD-Cu film, 26,41 by-products from β-diketonato, including O and F, may temporarily exist on the Ru surface during nucleation, thereby reducing N when β-diketonato was used. For this reason, we may expect amidinato to exhibit a larger N per unit P Cu-pre.…”

Section: Resultsmentioning

confidence: 99%

“…This is consistent with a previous report that the Cu/Ru interface is free from O and F inclusions, even when using β-diketonato as the precursor. 26,41 To evaluate the adhesion strength between the deposited Cu layer and the Ru underlayer, we have previously reported θ for micron-scale Cu grains formed via agglomeration of a continuous Cu film following thermal annealing; we found θ = 42…”

Section: Resultsmentioning

confidence: 99%

Comparative Study on Cu-CVD Nucleation Using β-diketonato and Amidinato Precursors for Sub-10-nm-Thick Continuous Film Growth

Shima

Shimizu

Momose

et al. 2015

ECS J. Solid State Sci. Technol.

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We demonstrate the growth of sub-10-nm-thick continuous Cu films using chemical vapor deposition (CVD) for next-generation Cu interconnects for ultra-large-scale integration (ULSI). The thickness of such films is equivalent to that of Cu during coalescence, and optimized operating conditions and substrate materials are required to form high-density nucleates. Ru was used as an underlayer, and the time evolution of nucleation and grain growth were studied with systematically varied conditions using two Cu precursors: conventional β-diketonato and newly developed amidinato precursor compounds. The revealed geometry of the initial nano-scale Cu grains prior to coalescence suggests the required nucleate density for 7-nm-thick continuous film growth, and which was 2.4 × 10 11 /cm 2 . The maximum nucleate density was achieved with the lowest deposition temperature and highest precursor concentration for both precursors; i.e., 6.9 × 10 11 /cm 2 for β-diketonato at 100 • C, and 4.6 × 10 11 /cm 2 for amidinato at 150 • C. A 10-nm-thick continuous Cu film was formed using amidinato under the optimized conditions. Furthermore, the framework used in this study to enable a high nucleate density suggests that it is possible to form thinner (4 nm∼) Cu films using amidinato. Because of the inherent good step coverage of CVD, this process is a promising candidate for next-generation ULSI Cu interconnects. Cu interconnects for ultra-large-scale integration (ULSI) are currently fabricated using the so-called 'damascene process,' which consists of: (i) the formation of three-dimensional features (i.e., trenches and via-holes) in the inter-layer dielectric using etching; (ii) sputtering of TaN x onto the inter-layer dielectric to form a Cu diffusion barrier; (iii) sputtering of Ta as an adhesion layer; (iv) sputtering of Cu as a seed layer for subsequent electro-plating; and (v) electro-plating of Cu to fill the remaining gaps. As the dimensions of complementary metal-oxide-semiconductor (CMOS) transistors in ULSI have reduced, the feature size of the Cu interconnects has also reduced. 1After 2016, the Cu line width will become smaller than 22 nm, so the Cu seed layer must be thinner than 7 nm.2 With such small dimensions, conventional physical vapor deposition (PVD) processes (including sputtering) face difficulties in forming conformal Cu films on narrow and high aspect-ratio (AR) features. Hence, it is essential to develop alternative deposition processes that are capable of highly conformal film growth. The current leading candidates are atomic layer deposition (ALD), 3,4 chemical vapor deposition (CVD), 5-9 and supercritical fluid deposition (SCFD).10 ALD-grown films exhibit the required properties for this purpose, but the growth rate of 0.1-1.9 Å/cycle 11 is too slow for mass production. SCFD is an emerging technology, but it requires a high-pressure environment, which is not compatible with current vacuum processes and now under investigation. 12,13 CVD is the most widely studied method, due to its fast growth rate of 2.0-14...

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“…[1][2][3][4] The interconnect applications will require ultrathin (< 5nm) continuous films, which may be deposited directly onto a dielectric or onto a refractory material, such as Ta or TiN that functions as the barrier.…”

Section: Introductionmentioning

confidence: 99%

Growth And Characterization of Ultrathin Metal Films For ULSI Interconnects

Shin

Sun

White

et al. 2005

AIP Conference Proceedings

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Low-temperature chemical vapor deposition and scaling limit of ultrathin Ru films

Cited by 51 publications

References 7 publications

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Comparative Study on Cu-CVD Nucleation Using β-diketonato and Amidinato Precursors for Sub-10-nm-Thick Continuous Film Growth

Growth And Characterization of Ultrathin Metal Films For ULSI Interconnects

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