Abstract
This study reports the good thermal stability of a sputtered Cu(MoN x ) seed layer on a barrierless Si substrate. A Cu film with a small amount of MoN x was deposited by reactive co-sputtering of Cu and Mo in an Ar/N2 gas mixture. After annealing at 560°C for 1 h, no copper silicide formation was observed at the interface of Cu and Si. Leakage current and resistivity evaluations reveal the good thermal reliability of Cu with a dilute amount of MoN x at temperatures up to 560°C, suggesting its potential application in advanced barrierless metallization. The thermal performance of Cu(MoN x ) as a seed layer was evaluated when pure Cu is deposited on top. X-ray diffraction, focused ion beam microscopy, and transmission electron microscopy results confirm the presence of an ∼10-nm-thick reaction layer formed at the seed layer/Si interface after annealing at 630°C for 1 h. Although the exact composition and structure of this reaction layer could not be unambiguously identified due to trace amounts of Mo and N, this reaction layer protects Cu from a detrimental reaction with Si. The Cu(MoN x ) seed layer is thus considered to act as a diffusion buffer with stability up to 630°C for the barrierless Si scheme. An electrical resistivity of 2.5 μΩ cm was obtained for the Cu/Cu(MoN x ) scheme after annealing at 630°C.
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Acknowledgements
This work is supported by National Science Council of the Republic of China in Taiwan (NSC 95-2221-E-243-001, 96-2622-E-243-001-CC3). One of authors (C.H. Lin) thanks National Taiwan University of Science and Technology for financial support during the course of this study.
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Chu, J., Lin, C., Leau, W. et al. Thermal Stability Study of Cu(MoN x ) Seed Layer on Barrierless Si. J. Electron. Mater. 38, 100–107 (2009). https://doi.org/10.1007/s11664-008-0523-3
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DOI: https://doi.org/10.1007/s11664-008-0523-3