The fabrication of three-dimensional nano-structures by defocused electron beam energy

We demonstrate a novel method to fabricate three-dimensional structure with various shapes using defocused electron beam lithography (DEBL) for optical elements. In this study, we experimentally analyzed the relationship between the shape profiles of exposed patterns and defocusing length by varying parameters for e-beam lithography.Through these experiments, we found out that the shape profiles of exposed patterns depended on the defocusing length at the specific conditions in the e-beam lithography. This is due to the fact that the distribution and intensity of electron beam energy are changed by the defocusing length degree in the DEBL. These results allow the fabrication of three-dimensional (3D) structures with various shapes for optical elements by varying the defocusing length under the proper conditions of e-beam lithography. Based on these results, we can fabricate the 3D patterns with hemispherical shape for nano lens array and nano cone shape for SERS (surface enhanced Raman spectroscopy) and optical diffraction grating patterns with nano scale depth and width.