Shadow Overlap Ion-beam Lithography for Nanoarchitectures

Precisely constructed nanoscale devices and nanoarchitectures with high spatial resolution are critically needed for applications in highspeed electronics, high-density memory, efficient solar cells, optoelectronics, plasmonics, optical antennas, chemical sensors, biological sensors, and nanospectroscopic imaging. Current methods of classical optical lithography are limited by the diffraction effect of light for nanolithography, and the state of art of e-beam or focused ion beam lithography limit the throughput and further reduction less than few nanometers for large-area batch fabrication. However, these limits can be surpassed surprisingly by utilizing the overlap of two shadow images. Here we present shadow overlap of ion-beam lithography (SOIL), which can combine the advantages of parallel processing, tunable capability of geometries, cost-effective method, and high spatial resolution nanofabrication technique. The SOIL method relies on the overlap of shadows created by the directional metal deposition and etching angles on prepatterned structures. Consequently, highly tunable patterns can be obtained. As examples, unprecedented nanoarchitectures for optical antennas are demonstrated by SOIL. We expect that SOIL can have a significant impact not only on nanoscale devices, but also large-scale (i.e., micro and macro) three-dimensional innovative lithography.