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Low resistivity HfNx grown by plasma-assisted ALD with external rf substrate biasing


Plasma-assisted atomic layer deposition (ALD) of HfNx thin films using tris(dimethylamino)cyclopentadienylhafnium [CpHf(NMe2)3] as the Hf precursor and H2 plasma as reducing co-reactant is reported. We previously concluded that the HfNx films prepared for a grounded substrate (0V substrate potential) exhibited a rather high electrical resistivity of 9.0·10-1 Ωcm. In the present work, we show a steady decrease in electrical resistivity by two orders of magnitude to 3.3·10-3 Ωcm upon increasing the time-averaged substrate potential up to -130V by externally biasing the substrate. A further increase in potential up to -187V led to an increase in electrical resistivity to 1.0·10-2 Ωcm. The variations in electrical resistivity with the potential were found to correlate with the extent of grain boundary scattering in the films, which significantly decreased upon increasing the potential up to -130V, primarily due to major changes in film chemical composition. The latter consisted in a decrease in O content from 20.1 at.% under no bias to ≤2 at.% for a potential of -130V and an associated increase in Hf3+ fraction from 0.65 to 0.82. The latter is key to the development of low resistivity δ-HfN. A further increase in potential to -187V led to an increase in grain boundary scattering as a consequence of a major decrease in grain size as well as in-grain crystallinity. In view of advanced nanoelectronic devices, the HfNx layers were also deposited on 3D trench nanostructures at a potential of -130V. A low oxygen content in the HfNx film measured on both the planar and vertical topographies of the trenches. Overall, the time-averaged substrate potential has been shown to highly affect the chemical composition, microstructure and the associated electrical properties of the HfNx layers and can be used to tailor the HfNx film properties.

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Publication details

The article was received on 28 Dec 2017, accepted on 12 Mar 2018 and first published on 12 Mar 2018

Article type: Paper
DOI: 10.1039/C7TC05961B
Citation: J. Mater. Chem. C, 2018, Accepted Manuscript
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    Low resistivity HfNx grown by plasma-assisted ALD with external rf substrate biasing

    S. Karwal, M. A. Verheijen, B. Williams, T. Faraz, W. Kessels and M. Creatore, J. Mater. Chem. C, 2018, Accepted Manuscript , DOI: 10.1039/C7TC05961B

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