Influences of process parameters and mold geometry on direct nanoimprint

Nanoimprint lithography (NIL) has been recognized as a high-throughput and low cost fabrication process for manufacturing sub-wavelength nanostructures. We use direct imprint process to transfer nanoscale patterns on metallic films coated on silicon wafers. This work is dedicated to investigate the effects of the factors, which include mold geometry, film thickness and imprinting process parameters, on the quality of pattern transfer in a direct nanoimprint process. An atomic force microscopy (AFM), a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM) are utilized to confirm the formation height and the surface topography of the transferred patterns after the imprinting process. The formation height ratio is utilized as an index for analyzing the quality of formation. The experimental results illustrate that those factors obviously effect the formation. In addition, the relationships between linewidth-to-pitch ratio (LPR), film thickness, working temperature and holding time are determined. The formability of the metallic thin films can be improved through suitable control of these parameters.