Diffusion Studies of Copper on Ruthenium Thin Film

Chan, Raymond; Arunagiri, Tiruchirapalli; Zhang, Y.; Chyan, Oliver; Wallace, Robert M.; Kim, M. J.; Hurd, Trace

doi:10.1149/1.1757113

Cited by 175 publications

(126 citation statements)

References 11 publications

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“…Electronic mail: r.colomaribera@utwente.nl which allows Cu or O diffusion through grain boundaries. 17,18,19 For this reason an ultrathin amorphous Ru layer is necessary as an effective diffusion barrier. 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.…”

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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“…These include an inability to conformally deposit a thin barrier film in the high aspect ratio trenches which inevitably leads to void formation in the subsequently deposited copper seed layer. To surmount such challenges, Ruthenium (Ru) and several of its alloys have been proposed as alternative barrier liners.5-10 These have the added advantage of direct electroplating of Cu, eliminating the need for a Cu seed layer.However, Ru is not an ideal barrier as it forms columnar structures and, hence, provides diffusion paths for Cu at the grain boundaries 11,12 and also has poor adherence to the underlying dielectrics which may result in the peeling of these films during polishing.13,14 Therefore, a thin (∼1 nm) TaN or TiN layer is deposited between Ru and the dielectric interface which helps in both negating the columnar growth of Ru and improving the adherence between Ru and the dielectric. 13,14 Of these, Ru/TiN structures were chosen for the analysis here since Amanapu et al 15 have shown that these films are polished faster compared to those on TaN.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…However, Ru is not an ideal barrier as it forms columnar structures and, hence, provides diffusion paths for Cu at the grain boundaries 11,12 and also has poor adherence to the underlying dielectrics which may result in the peeling of these films during polishing. 13,14 Therefore, a thin (∼1 nm) TaN or TiN layer is deposited between Ru and the dielectric interface which helps in both negating the columnar growth of Ru and improving the adherence between Ru and the dielectric.…”

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confidence: 99%

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Investigation of Guanidine Carbonate-Based Slurries for Chemical Mechanical Polishing of Ru/TiN Barrier Films with Minimal Corrosion

Sagi

Amanapu

Teugels

et al. 2014

ECS J. Solid State Sci. Technol.

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This work describes the response of Ru/TiN barrier films to solutions of H 2 O 2, guanidine carbonate (GC) and other additives in terms of open circuit potential measurements and potentiodynamic polarization data. It was found that an aqueous solution containing 1 wt% H 2 O 2 , 0.25 wt% GC and 5 mM BTA is effective in maintaining a low corrosion potential gap of Ru and Cu at ∼15 mV at pH 9. The slurry prepared by adding 5 wt% silica to this mixture yields a Ru removal rate (RR) of 10 nm/min and a Cu RR of 12 nm/min at 2 psi polishing pressure. The effect of carbonate and guanidinium ions as well as BTA on the corrosion behavior of Ru and Cu is discussed. Dodecyl-benzene-sulfonic acid (DBSA) was also found to be an effective corrosion inhibitor of Ru in the presence of H 2 O 2 and GC based solutions at pH 9 with a good post-polished surface finish but reduced the Ru RRs to ∼ 2 nm/min. As the scaling of interconnect structures continues beyond the 22 nm technology node, the width of copper lines continues to diminish. At such lower line widths, the effect of electron scattering on conductivity increases resulting in higher resistivity and reduced current carrying capacity. One way of mitigating this effect is to reduce the barrier liner thickness to less than ∼3 nm to accommodate a thicker copper line within a given trench. In such situations, the Ta/TaN bilayer, commonly used as barrier liner in the earlier copper interconnects, 1-4 faces several challenges. These include an inability to conformally deposit a thin barrier film in the high aspect ratio trenches which inevitably leads to void formation in the subsequently deposited copper seed layer. To surmount such challenges, Ruthenium (Ru) and several of its alloys have been proposed as alternative barrier liners.5-10 These have the added advantage of direct electroplating of Cu, eliminating the need for a Cu seed layer.However, Ru is not an ideal barrier as it forms columnar structures and, hence, provides diffusion paths for Cu at the grain boundaries 11,12 and also has poor adherence to the underlying dielectrics which may result in the peeling of these films during polishing.13,14 Therefore, a thin (∼1 nm) TaN or TiN layer is deposited between Ru and the dielectric interface which helps in both negating the columnar growth of Ru and improving the adherence between Ru and the dielectric. 13,14 Of these, Ru/TiN structures were chosen for the analysis here since Amanapu et al. 15 have shown that these films are polished faster compared to those on TaN. They attributed this to the difference in the crystalline orientation of the Ru films deposited on TiN and TaN layers.It is very difficult to obtain adequate removal rates (RR) of Ru during planarization since it is a noble and hard material, making it a challenge to achieve the desired RR selectivity to Cu at the barrier interface. Moreover, Ru is more cathodic to Cu since its standard reduction potential (0.21 V vs. SCE) is greater than that of Cu (0.1 V vs. SCE). Hence, there is a high possibility of Cu corro...

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“…Like most metals, Ru forms a polycrystalline structure after a few nanometers which allows Cu or O diffusion through grain boundaries. 325,333,334 For this reason an ultrathin amorphous Ru layer is necessary as an effective diffusion barrier. 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.…”

Section: Introductionmentioning

confidence: 99%

Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers

Ribera¹

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Diffusion Studies of Copper on Ruthenium Thin Film

Cited by 175 publications

References 11 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

Investigation of Guanidine Carbonate-Based Slurries for Chemical Mechanical Polishing of Ru/TiN Barrier Films with Minimal Corrosion

Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers

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