Abstract
The current nanofabrication techniques including electron beam lithography provide fabrication resolution in the nanometre range. The major limitation of these techniques is their incapability of arbitrary three-dimensional nanofabrication. This has stimulated the rapid development of far-field three-dimensional optical beam lithography where a laser beam is focused for maskless direct writing. However, the diffraction nature of light is a barrier for achieving nanometre feature and resolution in optical beam lithography. Here we report on three-dimensional optical beam lithography with 9 nm feature size and 52 nm two-line resolution in a newly developed two-photon absorption resin with high mechanical strength. The revealed dependence of the feature size and the two-line resolution confirms that they can reach deep sub-diffraction scale but are limited by the mechanical strength of the new resin. Our result has paved the way towards portable three-dimensional maskless laser direct writing with resolution fully comparable to electron beam lithography.
Highlights
The current nanofabrication techniques including electron beam lithography provide fabrication resolution in the nanometre range
Though the use of near-field nano-focusing has recently enabled low-cost plasmonic lithography with sub-100 nm resolution and 22 nm feature size[2], this approach inherently cannot facilitate the nanofabrication of three-dimensional (3D) structures that are highly required in next-generation nanophotonic devices[3,4]
Even for two-beam Optical beam lithography (OBL) based on the polymerization and photoinhibition strategy[6,7,8,9,10], it has been impossible to realize the fabrication with feature size and resolution comparable to that achievable by electron beam lithography (EBL) due to the lack of photoresins with large two-photon absorption cross-section, high mechanical strength and sufficient photoinhibition function
Summary
The current nanofabrication techniques including electron beam lithography provide fabrication resolution in the nanometre range. The major limitation of these techniques is their incapability of arbitrary three-dimensional nanofabrication This has stimulated the rapid development of far-field three-dimensional optical beam lithography where a laser beam is focused for maskless direct writing. Our result has paved the way towards portable three-dimensional maskless laser direct writing with resolution fully comparable to electron beam lithography While it is not a cost-effective solution, electron beam lithography (EBL) facilitates nanometre resolution[1] because of the diffraction nature of an electron beam that exhibits an extremely short De Broglie wavelength (Fig. 1a). The smallest feature size and the highest resolution are limited by the mechanical strength of the solidified material, which can be far beyond the diffraction limit provided that an appropriate photoresin with high mechanical strength can be developed This breakthrough has not yet been achieved. We demonstrate 3D deep sub-diffraction OBL with 9 nm (l/42 for the wavelength of the inhibition beam) feature size and 52 nm (l/7) two-line resolution in a resin that can efficiently harness two-photon polymerization (2PP) and single-photon inhibition
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