Nature Commun. 4, 2061 (2013)

The top-down fabrication of nanoscale electronic devices relies on electron-beam lithography, which has a resolution of a few nanometres and is limited by the electron-sensitive resins used. This method is not suitable for creating three-dimensional features, and as a result alternative techniques based on optical lithography have been developed, which exploit a focused laser beam for direct writing. However, the feature size that can be achieved with optical lithography is limited by diffraction to hundreds of nanometres. Min Gu and colleagues at Swinburne University of Technology and CSIRO Materials Science and Engineering have now developed three-dimensional optical beam lithography that is capable of producing features of 9 nm and achieving a two-line resolution (the minimum distance between two features) of 52 nm.

The improved resolution is attained through the use of a photoresin with high mechanical strength and a two-beam configuration. The photoresin has activation channels for both photopolymerization and photoinhibition, and one optical beam (with a wavelength of 800 nm) acts as the writing beam and the other as the inhibition beam, which spatially confines the photopolymerization induced by the writing beam. This approach allows feature sizes and resolutions to be achieved well below the diffraction limit (around 250 nm) of the writing beam.