Abstract
Previous studies showed that cobalt silicide can form ohmic contacts to p-type 6H-SiC by directly reacting cobalt with 6H-SiC. Similar results can be achieved on 4H-SiC, given the similarities between the different silicon carbide polytypes. However, previous studies using multilayer deposition of silicon/cobalt on 4H-SiC gave ohmic contacts to n-type. In this study, we investigated the cobalt silicide/4H-SiC system to answer two research questions. Can cobalt contacts be self-aligned to contact holes to 4H-SiC? Are the self-aligned contacts ohmic to n-type, p-type, both or neither? Using x-ray diffraction, it was found that a mixture of silicides (\(\hbox {Co}_2\hbox {Si}\) and CoSi) was reliably formed at 800\(^\circ \)C using rapid thermal processing. The cobalt silicide mixture becomes ohmic to epitaxially grown n-type (\(1\times 10^{19} \hbox {cm}^{-3}\)) if annealed at 1000\(^\circ \)C, while it shows rectifying properties to epitaxially grown p-type (\(1\times 10^{19} \hbox {cm}^{-3}\)) for all tested anneal temperatures in the range 800–1000\(^\circ \)C. The specific contact resistivity (\(\rho _\mathrm{C}\)) to n-type was \(4.3 \times 10^{-4}\) \(\mathrm {\Omega }\)\(\,\hbox {cm}^{2}\). This work opens the possibility to investigate other self-aligned contacts to silicon carbide.
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Acknowledgments
Thanks goes to Tomas Kubart for assisting in the cobalt deposition. Thanks goes to Gunnar Malm, who provided much appreciated feedback on the manuscript. The authors thank the Knut and Alice Wallenberg Foundation for funding this research as a part of the Working on Venus project.
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Ekström, M., Ferrario, A. & Zetterling, CM. Investigation of a Self-Aligned Cobalt Silicide Process for Ohmic Contacts to Silicon Carbide. J. Electron. Mater. 48, 2509–2516 (2019). https://doi.org/10.1007/s11664-019-07020-0
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DOI: https://doi.org/10.1007/s11664-019-07020-0