TaC as a diffusion barrier between Si and Cu

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

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42 Citations (Scopus)

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

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, 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