Hot-wire assisted ALD of tungsten films: In-situ study of the interplay between CVD, etching, and ALD modes

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    Abstract

    In this work, we investigated an approach of hot-wire assisted ALD (HWALD), utilizing a hot (up to 2000 8C) tungsten (W) wire. Tungsten films were deposited by this method using alternating pulses of WF6 gas and atomic hydrogen (at-H). The latter was generated by catalytic dissociation of molecular hydrogen (H2) upon the hot-wire. The W films were grown on a 100-nm thick thermal SiO2. The growth process was monitored in real time by an in-situ spectroscopic ellipsometer (SE). The real-time SE monitoring revealed the coexistence of three processes: CVD, etching, and ALD of the W film. WF6 could back-stream diffuse to the hot-wire, resulting in WF6 decomposition and generation of a flux of fluorine (F). The latter caused etching of the grown W film and the filament, and provided extra tungsten supply, which might cause CVD. Higher pressure and higher carrier gas flow rate were found to largely suppress the back-stream diffusion of WF6, which efficiently limited CVD. By controlling the dose of WF6 and process pressure, the etching had also been minimized. X-ray photoelectron spectroscopy of optimized HWALD grown W revealed 99 at% of W; concentrations of oxygen and fluorine were lower than 1%, below the detection limit.
    Original languageUndefined
    Pages (from-to)1607-1614
    Number of pages8
    JournalPhysica status solidi A
    Volume212
    Issue number7
    DOIs
    Publication statusPublished - 25 May 2015

    Keywords

    • METIS-312664
    • Tungsten
    • Thin Films
    • in-situ spectroscopic ellipsometer
    • Etching
    • IR-96409
    • atomic layer depositionetchinghot wirein-situ spectroscopic ellipsometerthin filmstungsten
    • Atomic Layer Deposition
    • hot wire
    • EWI-26132

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