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Improved nanofabrication through guided transient liquefaction

An Erratum to this article was published on 01 June 2008

Abstract

A challenge in nanofabrication is to overcome the limitations of various fabrication methods, including defects, line-edge roughness and the minimum size for the feature linewidth. Here we demonstrate a new approach that can remove fabrication defects and improve nanostructures post-fabrication. This method, which we call self-perfection by liquefaction, can significantly reduce the line-edge roughness and, by using a flat plate to guide the process, increase the sidewall slope, flatten the top surface and narrow the width while increasing the height. The technique involves selectively melting nanostructures for a short period of time (hundreds of nanoseconds) while applying a set of boundary conditions to guide the flow of the molten material into the desired geometry before solidification. Using this method we reduced the 3σ line-edge roughness of 70-nm-wide chromium grating lines from 8.4 nm to less than 1.5 nm, which is well below the ‘red-zone limit’ of 3 nm discussed in the International Technology Roadmap for Semiconductors. We also reduced the width of a silicon line from 285 nm to 175 nm, while increasing its height from 50 nm to 90 nm. Self-perfection by liquefaction can also be extended to other metals and semiconductors, dielectrics and large-area wafers.

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Figure 1: Working principle of three forms of self-perfection by liquefaction (SPEL).
Figure 2: SEM images of various nanostructures before (left panels) and after (right panels) treatment with open-SPEL with a single excimer laser pulse.
Figure 3: The edge profiles of some of the silicon and chromium lines from Fig. 2 before (left panels) and after (right panels) treatment with open-SPEL as measured in SEM images.
Figure 4: SEM images of silicon and chromium lines before (left panels) and after (right) treatment with capped-SPEL.
Figure 5: SEM images of chromium and silicon lines on SiO2 substrates before (left panels) and after (right panels) treatment with SPEL with a single quartz plate guiding the process.
Figure 6: SEM images of various nanostructures before and after open- and guided-SPEL.

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Acknowledgements

The authors thank K. Morton and Zhaoning Yu for master imprint moulds, Xiaogan Liang for providing the LER fitting programs and assistance, and P. Murphy for proofreading the manuscript. S.Y.C. thanks L. Cooper, formerly of the U.S. Office of Naval Research (ONR), for his understanding and encouragement, and for providing the earliest financial support to the work. We acknowledge the financial support from ONR and the Defense Advanced Research Projects Agency (DARPA).

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S.Y.C. conceived the SPEL method. Both authors contributed to the experiments and data analysis and to writing the manuscript.

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Correspondence to Stephen Y. Chou.

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Authors have filed patent applications and have assigned rights to Princeton University.

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Chou, S., Xia, Q. Improved nanofabrication through guided transient liquefaction. Nature Nanotech 3, 295–300 (2008). https://doi.org/10.1038/nnano.2008.95

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