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Ultrafast and direct imprint of nanostructures in silicon

Abstract

The fabrication of micrometre- and nanometre-scale devices in silicon typically involves lithography and etching. These processes are costly and tend to be either limited in their resolution or slow in their throughput1. Recent work has demonstrated the possibility of patterning substrates on the nanometre scale by ‘imprinting’2,3 or directed self-assembly4, although an etching step is still required to generate the final structures. We have devised and here demonstrate a rapid technique for patterning nanostructures in silicon that does not require etching. In our technique—which we call ‘laser-assisted direct imprint’ (LADI)—a single excimer laser pulse melts a thin surface layer of silicon, and a mould is embossed into the resulting liquid layer. A variety of structures with resolution better than 10 nm have been imprinted into silicon using LADI, and the embossing time is less than 250 ns. The high resolution and speed of LADI, which we attribute to molten silicon's low viscosity (one-third that of water), could open up a variety of applications and be extended to other materials and processing techniques.

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Figure 1: Schematic of laser-assisted direct imprint (LADI) of nanostructures in silicon.
Figure 2: Scanning electron microscope (SEM) images.
Figure 3: SEM image of the cross-section of samples patterned using LADI.
Figure 4: Atomic force micrographs (AFM) of isolated mesas patterned by LADI.

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Acknowledgements

We thank Y. Zhan for his contributions in the initial phase of the work, Z. Suo for help with the discussion of the Reynolds number, and the US Defense Advanced Research Program Agency (DARPA), the Office of Naval Research (ONR) and the Army Research Office (ARO, through an equipment grant) for their partial financial support of the project.

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Correspondence to Stephen Y. Chou.

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Chou, S., Keimel, C. & Gu, J. Ultrafast and direct imprint of nanostructures in silicon. Nature 417, 835–837 (2002). https://doi.org/10.1038/nature00792

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