TaC as a diffusion barrier between Si and Cu

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

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Abstract

The reaction mechanisms and related microstructures in the Si/TaC/Cu metallization system have been studied experimentally and theoretically by utilizing ternary Si-Ta-C and Ta-C-Cu phase diagrams as well as activity diagrams calculated at 800 °C. With the help of sheet resistance measurements, Rutherford backscattering spectrometry, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the metallization structure with the 70 nm thick TaC barrier layer was observed to fail completely at temperatures above 725 °C because of the formation of large Cu3Si protrusions. However, the formation of amorphous Ta layer containing significant amounts of carbon and oxygen was already observed at the TaC/Cu interface at 600 °C. This layer also constituted an additional barrier layer for Cu diffusion, which occurred only after the crystallization of the amorphous layer. The formation of Ta2O5 was observed at 725 °C with x-ray diffraction, indicating that the oxygen rich amorphous layer had started to crystallize. The formation of SiC and TaSi2 occurred almost simultaneously at 800 °C. The observed reaction structure was consistent with the thermodynamics of the ternary system. The metallization structures with 7 nm and 35 nm TaC barrier layers failed above 550 °C and 650 °C, respectively, similarly because of the formation of Cu3Si. The high formation temperature of TaSi2 and SiC implies high stability of Si/TaC interface, thus making TaC layer a potential candidate to be used as a diffusion barrier for Cu metallization.
Original languageEnglish
Pages (from-to)5391-5399
JournalJournal of Applied Physics
Volume91
Issue number8
DOIs
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed

Fingerprint

barrier layers
x ray diffraction
oxygen
ternary systems
backscattering
diagrams
phase diagrams
crystallization
thermodynamics
transmission electron microscopy
microstructure
scanning electron microscopy
temperature
carbon
spectroscopy

Keywords

  • tantalum
  • tantalum carbide
  • tantalum pentoxide
  • metallization
  • silicon
  • copper
  • semiconductor device metallisation
  • diffusion barriers
  • annealing
  • phase diagrams
  • thermodynamic properties
  • rutherford backscattering
  • x-ray diffraction
  • transmission electron microscopy
  • scanning electron microscopy
  • failure analysis

Cite this

Laurila, T., Zeng, K., Kivilahti, J. K., Molarius, J., & Suni, I. (2002). TaC as a diffusion barrier between Si and Cu. Journal of Applied Physics, 91(8), 5391-5399. https://doi.org/10.1063/1.1464652
Laurila, Tomi ; Zeng, Kejun ; Kivilahti, Jorma K. ; Molarius, Jyrki ; Suni, Ilkka. / TaC as a diffusion barrier between Si and Cu. In: Journal of Applied Physics. 2002 ; Vol. 91, No. 8. pp. 5391-5399.
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abstract = "The reaction mechanisms and related microstructures in the Si/TaC/Cu metallization system have been studied experimentally and theoretically by utilizing ternary Si-Ta-C and Ta-C-Cu phase diagrams as well as activity diagrams calculated at 800 °C. With the help of sheet resistance measurements, Rutherford backscattering spectrometry, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the metallization structure with the 70 nm thick TaC barrier layer was observed to fail completely at temperatures above 725 °C because of the formation of large Cu3Si protrusions. However, the formation of amorphous Ta layer containing significant amounts of carbon and oxygen was already observed at the TaC/Cu interface at 600 °C. This layer also constituted an additional barrier layer for Cu diffusion, which occurred only after the crystallization of the amorphous layer. The formation of Ta2O5 was observed at 725 °C with x-ray diffraction, indicating that the oxygen rich amorphous layer had started to crystallize. The formation of SiC and TaSi2 occurred almost simultaneously at 800 °C. The observed reaction structure was consistent with the thermodynamics of the ternary system. The metallization structures with 7 nm and 35 nm TaC barrier layers failed above 550 °C and 650 °C, respectively, similarly because of the formation of Cu3Si. The high formation temperature of TaSi2 and SiC implies high stability of Si/TaC interface, thus making TaC layer a potential candidate to be used as a diffusion barrier for Cu metallization.",
keywords = "tantalum, tantalum carbide, tantalum pentoxide, metallization, silicon, copper, semiconductor device metallisation, diffusion barriers, annealing, phase diagrams, thermodynamic properties, rutherford backscattering, x-ray diffraction, transmission electron microscopy, scanning electron microscopy, failure analysis",
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Laurila, T, Zeng, K, Kivilahti, JK, Molarius, J & Suni, I 2002, 'TaC as a diffusion barrier between Si and Cu', Journal of Applied Physics, vol. 91, no. 8, pp. 5391-5399. https://doi.org/10.1063/1.1464652

TaC as a diffusion barrier between Si and Cu. / Laurila, Tomi; Zeng, Kejun; Kivilahti, Jorma K.; Molarius, Jyrki; Suni, Ilkka.

In: Journal of Applied Physics, Vol. 91, No. 8, 2002, p. 5391-5399.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - TaC as a diffusion barrier between Si and Cu

AU - Laurila, Tomi

AU - Zeng, Kejun

AU - Kivilahti, Jorma K.

AU - Molarius, Jyrki

AU - Suni, Ilkka

N1 - Project code: Z1SU00150

PY - 2002

Y1 - 2002

N2 - The reaction mechanisms and related microstructures in the Si/TaC/Cu metallization system have been studied experimentally and theoretically by utilizing ternary Si-Ta-C and Ta-C-Cu phase diagrams as well as activity diagrams calculated at 800 °C. With the help of sheet resistance measurements, Rutherford backscattering spectrometry, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the metallization structure with the 70 nm thick TaC barrier layer was observed to fail completely at temperatures above 725 °C because of the formation of large Cu3Si protrusions. However, the formation of amorphous Ta layer containing significant amounts of carbon and oxygen was already observed at the TaC/Cu interface at 600 °C. This layer also constituted an additional barrier layer for Cu diffusion, which occurred only after the crystallization of the amorphous layer. The formation of Ta2O5 was observed at 725 °C with x-ray diffraction, indicating that the oxygen rich amorphous layer had started to crystallize. The formation of SiC and TaSi2 occurred almost simultaneously at 800 °C. The observed reaction structure was consistent with the thermodynamics of the ternary system. The metallization structures with 7 nm and 35 nm TaC barrier layers failed above 550 °C and 650 °C, respectively, similarly because of the formation of Cu3Si. The high formation temperature of TaSi2 and SiC implies high stability of Si/TaC interface, thus making TaC layer a potential candidate to be used as a diffusion barrier for Cu metallization.

AB - The reaction mechanisms and related microstructures in the Si/TaC/Cu metallization system have been studied experimentally and theoretically by utilizing ternary Si-Ta-C and Ta-C-Cu phase diagrams as well as activity diagrams calculated at 800 °C. With the help of sheet resistance measurements, Rutherford backscattering spectrometry, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the metallization structure with the 70 nm thick TaC barrier layer was observed to fail completely at temperatures above 725 °C because of the formation of large Cu3Si protrusions. However, the formation of amorphous Ta layer containing significant amounts of carbon and oxygen was already observed at the TaC/Cu interface at 600 °C. This layer also constituted an additional barrier layer for Cu diffusion, which occurred only after the crystallization of the amorphous layer. The formation of Ta2O5 was observed at 725 °C with x-ray diffraction, indicating that the oxygen rich amorphous layer had started to crystallize. The formation of SiC and TaSi2 occurred almost simultaneously at 800 °C. The observed reaction structure was consistent with the thermodynamics of the ternary system. The metallization structures with 7 nm and 35 nm TaC barrier layers failed above 550 °C and 650 °C, respectively, similarly because of the formation of Cu3Si. The high formation temperature of TaSi2 and SiC implies high stability of Si/TaC interface, thus making TaC layer a potential candidate to be used as a diffusion barrier for Cu metallization.

KW - tantalum

KW - tantalum carbide

KW - tantalum pentoxide

KW - metallization

KW - silicon

KW - copper

KW - semiconductor device metallisation

KW - diffusion barriers

KW - annealing

KW - phase diagrams

KW - thermodynamic properties

KW - rutherford backscattering

KW - x-ray diffraction

KW - transmission electron microscopy

KW - scanning electron microscopy

KW - failure analysis

U2 - 10.1063/1.1464652

DO - 10.1063/1.1464652

M3 - Article

VL - 91

SP - 5391

EP - 5399

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 8

ER -

Laurila T, Zeng K, Kivilahti JK, Molarius J, Suni I. TaC as a diffusion barrier between Si and Cu. Journal of Applied Physics. 2002;91(8):5391-5399. https://doi.org/10.1063/1.1464652