Large area 50nm period grating by multiple nanoimprint lithography and spatial frequency doubling

The authors have developed an approach to fabricate large area 50nm period gratings (22nm linewidth) with low cost. The method used a fabrication cycle twice, each combining nanoimprint lithography with a spatial frequency doubling based on electroless plating, lift-off, and reactive ion etching. Hence by frequency doubling twice, we started with a 200nm period grating mold and finished with a 50nm period grating with a uniform area of 3cm2—the largest achieved today. This method is scalable for the fabrication of even smaller period gratings over a large area, and is a viable low-cost technique for making nanoimprint lithography molds for high-throughput fabrication of 50nm period grating or grid devices.