Efficient fabrication of complex nano-optical structures by E-beam lithography based on character projection

The fabrication of complex nano-optical structures for plasmonics, photonic-crystals, or meta-materials on application relevant areas by electron-beam lithography requires a highly parallel writing strategy. In case of periodic pattern as they are found in most of the mentioned optical elements this can be achieved by a so called character projection writing principle where complex exposure pattern are coded in a stencil mask and exposed with a single shot. Resulting shotcount and writing time reductions compared to standard Variable-Shaped-Beam exposures can be in the order of 100...10000. The limitation in flexibility by using hard-coded exposure shapes can be overcome by implementing the character projection principle with a highly precise motorized aperture stage capable of carrying several 1000 different apertures. Examples of nano-optical elements fabricated with the new character projection principle are presented.