The ultrasonic nanoimprint lithography (U-NIL) was proposed to overcome the drawbacks of long process time comparing with conventional NIL methods. However, the impacts of mold material and pattern size have not been systematically investigated for U-NIL Therefore, it is necessary to study on the optimum process parameters to get good replicated structures during imprinting process. In this paper, we fabricated three types of the mold with different materials and line widths, then demonstrated the replicated sub-micrometer and micrometer scales structures on poly(ethylene terephthalate) (PET) in heating-assisted ultrasonic nanoimprint. Using the filling ratio as imprinting quality, the results of Taguchi's orthogonal array experimental layout could determine the optimum process parameters as the best setting. From experiments, temperature is the most effective factor of different line width molds, and imprinting force is the most significant factor between different materials. These would provide to advance U-NIL to set imprinting conditions, and to achieve good replication with high throughput and low cost. (C) 2012 Elsevier B.V. All rights reserved.
