Failure mechanism of Ta diffusion barrier between Cu and Si

Tomi Laurila, Kejun Zeng, Jorma Kivilahti, Jyrki Molarius, Ilkka Suni

Research output: Contribution to journalArticleScientificpeer-review

81 Citations (Scopus)

Abstract

The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si–Ta–Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50–100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (∼650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si–Ta–Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.
Original languageEnglish
Pages (from-to)3377 - 3384
Number of pages8
JournalJournal of Applied Physics
Volume88
Issue number6
DOIs
Publication statusPublished - 2000
MoE publication typeA1 Journal article-refereed

Fingerprint

barrier layers
electron microscopes
phase diagrams
nodules
precipitates
backscattering
x ray diffraction
thermal stability
microstructure
scanning
temperature
oxygen
thin films
spectroscopy

Cite this

Laurila, T., Zeng, K., Kivilahti, J., Molarius, J., & Suni, I. (2000). Failure mechanism of Ta diffusion barrier between Cu and Si. Journal of Applied Physics, 88(6), 3377 - 3384. https://doi.org/10.1063/1.1288692
Laurila, Tomi ; Zeng, Kejun ; Kivilahti, Jorma ; Molarius, Jyrki ; Suni, Ilkka. / Failure mechanism of Ta diffusion barrier between Cu and Si. In: Journal of Applied Physics. 2000 ; Vol. 88, No. 6. pp. 3377 - 3384.
@article{67f783eb8d1a4dd4bd71bbba75b601e8,
title = "Failure mechanism of Ta diffusion barrier between Cu and Si",
abstract = "The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si–Ta–Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50–100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (∼650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si–Ta–Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.",
author = "Tomi Laurila and Kejun Zeng and Jorma Kivilahti and Jyrki Molarius and Ilkka Suni",
year = "2000",
doi = "10.1063/1.1288692",
language = "English",
volume = "88",
pages = "3377 -- 3384",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics AIP",
number = "6",

}

Laurila, T, Zeng, K, Kivilahti, J, Molarius, J & Suni, I 2000, 'Failure mechanism of Ta diffusion barrier between Cu and Si', Journal of Applied Physics, vol. 88, no. 6, pp. 3377 - 3384. https://doi.org/10.1063/1.1288692

Failure mechanism of Ta diffusion barrier between Cu and Si. / Laurila, Tomi; Zeng, Kejun; Kivilahti, Jorma; Molarius, Jyrki; Suni, Ilkka.

In: Journal of Applied Physics, Vol. 88, No. 6, 2000, p. 3377 - 3384.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Failure mechanism of Ta diffusion barrier between Cu and Si

AU - Laurila, Tomi

AU - Zeng, Kejun

AU - Kivilahti, Jorma

AU - Molarius, Jyrki

AU - Suni, Ilkka

PY - 2000

Y1 - 2000

N2 - The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si–Ta–Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50–100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (∼650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si–Ta–Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.

AB - The reaction mechanisms in the Si/Ta/Cu metallization system and their relation to the microstructure of thin films are discussed on the basis of experimental results and the assessment of the ternary Si–Ta–Cu phase diagram at 700 °C. With the help of sheet resistance measurements, Rutherford backscattering spectroscopy, x-ray diffraction, a scanning electron microscope, and a transmission electron microscope, the Ta barrier layer was observed to fail at temperatures above 650 °C due to the formation of TaSi2, the diffusion of Cu through the silicide layer, and the resulting formation of Cu3Si precipitates. However, in order for the TaSi2 phase to form first, the Ta diffusion barrier layer must be thick enough (e.g., 50–100 nm) to prevent Cu diffusion into the Si substrate up to the temperature of TaSi2 formation (∼650 °C). Independent of the Ta layer thickness, Cu3Si was present as large nodules, whereas the TaSi2 existed as a uniform layer. The resulting reaction structure was found to be in local equilibrium on the basis of the assessed Si–Ta–Cu phase diagram at 700 °C, and therefore no further reactions were expected. The role of oxygen was also found to be important in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.

U2 - 10.1063/1.1288692

DO - 10.1063/1.1288692

M3 - Article

VL - 88

SP - 3377

EP - 3384

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 6

ER -

Laurila T, Zeng K, Kivilahti J, Molarius J, Suni I. Failure mechanism of Ta diffusion barrier between Cu and Si. Journal of Applied Physics. 2000;88(6):3377 - 3384. https://doi.org/10.1063/1.1288692