Interconnect metals beyond copper: reliability challenges and opportunities

Croes, Kristof; Adelmann, Christoph; Wilson, Chris; Zahedmanesh, Houman; Pedreira, O. Varela; Wu, Chen; Leśniewska, A.; Oprins, Herman; Beyne, Sofie; Ciofi, Ivan; Kocaay, D.; Stucchi, M.; Tőkei, Zs.

doi:10.1109/iedm.2018.8614695

Cited by 62 publications

(45 citation statements)

References 14 publications

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“…In addition, in Co lines, self-heating is significant [14], and therefore, the actual EM activation energy may also be lower than what has previously been reported [5], [7].…”

Section: E Influence Of Joule Heating On the Em Activation Energymentioning

confidence: 62%

“…Therefore, alternative metals, such as cobalt [5]- [7] and ruthenium [7]- [9], are being investigated as replacements for Cu. The resistivity of Co and Ru versus Cu has already been studied extensively [10], [11], but studies of their EM performance remain limited [7], [12]- [14]. It was generally expected that Ru and Co would have very high EM activation energies because of their high melting temperature [15].…”

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confidence: 99%

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Electromigration Activation Energies in Alternative Metal Interconnects

Beyne

Pedreira

Oprins

et al. 2019

IEEE Trans. Electron Devices

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The electromigration (EM) activation energy (E A ) of alternative metals, such as Ru and Co, was obtained using low-frequency noise (LFN) measurements. High activation energies were expected, but values of ≈1 eV are found, most likely related to diffusion along with the metaldielectric interface. Wafer-level accelerated EM tests were carried out to compare the LFN E A to the EM E A in the Ru wires. The calculation of the EM E A is found to be strongly dependent on the assumed temperature profile in the wire due to Joule heating (JH). The temperature profile was calculated analytically, assuming the contacts are at ambient temperature. For a void forming in direct proximity of the contact, the EM E A then matches the LFN E A . For a void at average wire temperature (ambient + JH), E A ≈ 2 eV. In addition to demonstrating the application of LFN to study EM in alternative metals, this article also cautions for the impact of JH on the calculation of E A in interconnects.

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“…In addition, in Co lines, self-heating is significant [14], and therefore, the actual EM activation energy may also be lower than what has previously been reported [5], [7].…”

Section: E Influence Of Joule Heating On the Em Activation Energymentioning

confidence: 62%

mentioning

confidence: 99%

Electromigration Activation Energies in Alternative Metal Interconnects

Beyne

Pedreira

Oprins

et al. 2019

IEEE Trans. Electron Devices

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“…With continued pitch reduction, however, the use of Cu may not be sustainable not only due to the size effect [2][3][4][5], whereby metal resistivity dramatically increases as cross-sectional area decreases, but also because of electromigration concerns and the reduction of via and line volume occupied by the diffusion and wetting liners necessary for integration of Cu in the BEOL [6]. To overcome these challenges posed by the continued use of Cu, research has focused on identifying and evaluating alternative conductors for use in advanced interconnect nodes [7][8][9][10][11]. Among the many identified options, Ru has emerged as a promising candidate due not only to reduced impact of the size effect compared to Cu [12,13] but also because of its resilience to electromigration [11,14].…”

Section: Introductionmentioning

confidence: 99%

“…To overcome these challenges posed by the continued use of Cu, research has focused on identifying and evaluating alternative conductors for use in advanced interconnect nodes [7][8][9][10][11]. Among the many identified options, Ru has emerged as a promising candidate due not only to reduced impact of the size effect compared to Cu [12,13] but also because of its resilience to electromigration [11,14].…”

Section: Introductionmentioning

confidence: 99%

First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

Philip¹,

Lanzillo²,

Gunst

et al. 2020

Phys. Rev. Applied

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As the semiconductor industry turns to alternate conductors to replace Cu for future interconnect nodes, much attention has been focused on evaluating the electrical performance of Ru. The typical hexagonal close-packed (hcp) phase has been extensively studied, but relatively little attention has been paid to the face-centered cubic (fcc) phase, which has been shown to nucleate in confined structures and may be present in tight-pitch interconnects. Using ab initio techniques, we benchmark the performance of fcc Ru. We find that the phonon-limited bulk resistivity of the fcc Ru is less than half of that of hcp Ru, a feature we trace back to the stronger electron-phonon coupling elements in hcp Ru that are geometrically inherited from the modified Fermi surface shape of the fcc crystal. Despite this benefit of the fcc phase, high grain boundary scattering results in increased resistivity compared to Cu-based interconnects with similar average grain size. We find, however, that the line resistance of fcc Ru is lower than that of Cu below 21 nm line width due to the conductor volume lost to adhesion and wetting liners. In addition to studying bulk transport properties, we evaluate the performance of adhesion liners for fcc Ru. We find that it is energetically more favorable for fcc Ru to bind directly to silicon dioxide than through conventional adhesion liners such as TaN and TiN. In the case that a thin liner is necessary for the Ru deposition technique, we find that the vertical resistance penalty of a liner for fcc Ru can be up to eight times lower than that calculated for conventional liners used for Cu interconnects. Our calculations, therefore, suggest that the formation of the fcc phase of Ru may be a beneficial for advanced, low-resistance interconnects. arXiv:2001.02216v3 [cond-mat.mtrl-sci] a) fcc b) hcp

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“…Potential candidates are cobalt and ruthenium. Studying their EM properties using the standard accelerated test method is particularly difficult in this case because they exhibit very long EM lifetimes [10]. As such, very high stress conditions have to be applied in order to observe failures within a reasonable time-frame.…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Noise Measurements for Electromigration Characterization in BEOL Interconnects

Beyne

Croes

Pedreira

et al. 2019

2019 IEEE International Integrated Reliability Workshop (IIRW)

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In this paper we discuss a new EM test methodology, based on low-frequency noise (LFN) measurements. The main advantages of LFN over the standard accelerated EM tests are that they are non-destructive, much faster, closer to operation conditions and provide more fundamental understanding. Using the LFN technique, we study the EM properties in sub-30 nm line-width Cu interconnects with various metallization schemes. Furthermore, the EM activation energies of alternative metal interconnects (Ru, Co, W) are studied by means of LFN measurements.

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Interconnect metals beyond copper: reliability challenges and opportunities

Cited by 62 publications

References 14 publications

Electromigration Activation Energies in Alternative Metal Interconnects

Electromigration Activation Energies in Alternative Metal Interconnects

First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

Low-Frequency Noise Measurements for Electromigration Characterization in BEOL Interconnects

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