Soft nanoimprint lithography

We developed a UV assisted soft nanoimprint lithography (UV-SNIL) that can be applied for the reproduction of nanometer features over large areas. Based on a simple argument deduced from the Navier-Stokes equation, we suggest several solutions to enhance the imprinting process ability. One of the solutions is to use tri-layer soft stamps, which consists of a rigid carrier, a low Young's module buffer and a top layer supporting nanostructure patterns to be replicated. Typically, the buffer and the top layer are made of polydimethylsiloxane (PDMS) of 5 mm thickness and polymethylmetacrylate (PMMA) of 10-50 μm thickness respectively. Patterning of the stamp top layer can be done in three different ways, i.e., spin coating, nano-compression and direct writing, all resulting in 100 nm features over a large wafer area. Another solution is to use a bilayer resist system for which imprinting is performed on the top layer while the final pattern is obtained by transferring the top layer image into the bottom layer by reactive ion etching. Comparing to other imprint techniques, UV-SNIL works at room temperature and low pressure, which is applicable for a wafer-scale replication at high throughput. For the research purpose, we also demonstrate nanostructure fabrication by lift-off techniques.