Dual layer direct laser writing lithography for nanoscale patterning

We report a novel patterning technique termed dual-layer direct laser writing (DL-DLW), which utilizes laser direct-write lithography on a dual-layer photoresist stack to generate contoured features with linewidths below the original pattern specifications. The method exploits the differential development kinetics between positive-tone and negative-tone photoresist layers during development to generate contour-type nanostructures with linewidths substantially reduced from the original design specifications. Precise control over exposure dosage and development conditions enables straightforward adjustment of critical dimensions (CDs) in these contoured structures. Using DL-DLW, we successfully fabricated contoured metallic wires/trenches with CDs ranging from 200 nm to 600 nm, achieving minimum feature sizes approaching 200 nm under optimized conditions. Furthermore, we demonstrated the technique's patterning versatility through contoured letters, numerals, and symbols. We also fabricated metalenses structures as a demonstration of the patterning capability of DL-DLW, suggesting its potential relevance to nanophotonic applications and fundamental nanoscience research.