Chemical mechanism of oxidative etching of ruthenium: Insights into continuous versus self-limiting conditions

Yu, Neung-Kyung; Lee, Jeong‐Min; Kim, Woo‐Hee; Shong, Bonggeun

doi:10.1016/j.apsusc.2023.157864

Cited by 2 publications

(1 citation statement)

References 76 publications

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“…However, in both cases, a steady decrease in thickness is observed for the Ru substrates as the O 3 injection time is increased. Assuming that RuO 4 is the volatile species responsible for RuO 2 loss in our TiO 2 ALD experiments, this data is consistent with the fact that it is not chemically favorable for RuO 2 to oxidize into RuO 4 in the currently used temperature range. − It has been reported previously that RuO 4 is formed via the more direct reaction path of Ru → RuO 4 rather than through a Ru → RuO 2 → RuO 4 route …”

Section: Resultsmentioning

confidence: 99%

High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance

Jeon,

Kim,

Jang

et al. 2024

Chem. Mater.

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Capacitor structures utilized in modern dynamic random access memory (DRAM) cells require the conformal growth of high-k films on electrode materials. In this context, the atomic layer deposition (ALD) of rutile-phase TiO2 on nearly lattice-matched substrates such as RuO2 has been extensively explored. It is typically desired to grow such insulating films at high temperatures to ensure low defect concentrations and high crystallinity. However, with increasing growth temperature, it is also crucial to consider the aggravated effect of interface reactions that could potentially hinder final device performance. Here, we report the high-temperature ALD growth of TiO2 on RuO2 substrates using the heteroleptic precursor trimethoxy(pentamethylcyclopentadienyl)titanium ((CpMe5)Ti(OMe)3) and O3. High-quality, rutile-phase TiO2 films with large dielectric constants of ∼100 could be grown at temperatures exceeding 300 °C. When the growth temperature reaches 330 °C, we find that an anomalous RuO2 reduction reaction occurs due to interactions between the substrate and Ti precursor. The reduced Ru is transformed into volatile RuO4 during the subsequent O3 injection steps, resulting in partial etching of the substrate. Simple RuO2/TiO2/RuO2 capacitor devices fabricated from optimized films demonstrate excellent dielectric performance with an equivalent oxide thickness (EOT) of 0.5 nm at leakage current densities of less than 10–7 A/cm2. A further reduction of EOT to 0.4 nm could be achieved by implementing a single cycle of Al doping to the TiO2 films, surpassing the benchmark values proposed for next-generation DRAM capacitors by a safe margin. Our findings clearly showcase the benefits of high-temperature ALD in the semiconductor technology, as well as providing guidelines for the interpretation of the convoluted interface reactions tied to its implementation.

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Section: Resultsmentioning

confidence: 99%

High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance

Jeon,

Kim,

Jang

et al. 2024

Chem. Mater.

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Desorption model of volatile Ru species induced by partial chlorination on Ru(0001) under an O2/Cl2-based plasma process

Imai,

Matsui,

Sugano

et al. 2024

Journal of Vacuum Science &Amp; Technology B

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Ruthenium (Ru) is known to be effectively etched by O2-based plasma with a 10%–20% amount of Cl2, while it is less etched by pure O2-based or Cl2-rich plasma. In this work, reaction paths and energy profiles on a metallic Ru surface were calculated in density functional theory (DFT) simulations to reveal the chemical role of the small amount of Cl2 in the O2-based plasma for Ru etching. We prepared three Ru(0001) surfaces with (1 × 1) adatoms in which chemisorption sites were occupied by O and Cl adatoms. Subsequently, we assumed that convex Ru moieties, which are precursors to form volatile Ru species, were formed on the surface and that they were oxidized by the irradiation of O2-rich plasma. In each Ru(0001) surface, we calculated the production and activation energies of each elementary reaction path to desorb the volatile Ru products. Compared with the surface where all chemisorption sites were covered with O, both energies decreased in locations where some chemisorption sites were replaced by Cl. Our DFT-based research showed that a small amount of Cl2 in the O2/Cl2 plasma contributes to decreasing the production and activation energy to form volatile Ru products on the Ru surface, resulting in the etching rate being increased.

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Chemical mechanism of oxidative etching of ruthenium: Insights into continuous versus self-limiting conditions

Cited by 2 publications

References 76 publications

High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance

High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance

Desorption model of volatile Ru species induced by partial chlorination on Ru(0001) under an O2/Cl2-based plasma process

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Chemical mechanism of oxidative etching of ruthenium: Insights into continuous versus self-limiting conditions

Cited by 2 publications

References 76 publications

High-Temperature Atomic Layer Deposition of Rutile TiO2 Films on RuO2 Substrates: Interfacial Reactions and Dielectric Performance

High-Temperature Atomic Layer Deposition of Rutile TiO2 Films on RuO2 Substrates: Interfacial Reactions and Dielectric Performance

Desorption model of volatile Ru species induced by partial chlorination on Ru(0001) under an O2/Cl2-based plasma process

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Product

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High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance

High-Temperature Atomic Layer Deposition of Rutile TiO₂ Films on RuO₂ Substrates: Interfacial Reactions and Dielectric Performance