TaC as a diffusion barrier between Si and Cu

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

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    44 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 Cu 3Si 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 Ta 2O 5 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 TaSi 2 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 Cu 3Si. The high formation temperature of TaSi 2 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
    Number of pages9
    JournalJournal of Applied Physics
    Volume91
    Issue number8
    DOIs
    Publication statusPublished - 15 Apr 2002
    MoE publication typeA1 Journal article-refereed

    Keywords

    • diffusion barrier
    • diffusion kinetics
    • thermodynamics

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