Sub-100 nm features seamless roller mold using anodization and atomic layer deposition, for roll-to-roll nanoimprint lithography

Abstract

The authors demonstrate an approach using direct anodization and atomic layer deposition (ALD) to prepare a sub-100 nm seamless roller mold for roll-to-roll nanoimprinting. In this approach, the roller mold is prepared by direct anodization of a cylindrical Al roller and the mold's pore size is further reduced by ALD process. This direct anodization of the Al rod as a roller mold creates a hard and durable seamless roller mold for nanoimprinting process. The pores were found to be uniformly anodized on the cylindrical Al rod and ordered pores can be obtained after multisteps anodization. The sub-100 nm pores are hexagonally packed with a diameter of 43.8 ± 3 nm (before pore-widening process) and interpore spacing of 87.0 ± 8 nm, estimated using an image processing software (imagej). The size, interpore spacing, and depth of the pores depend on the anodization conditions such as type of electrolyte solution, anodization voltage, and duration. The pores' size can be further reduced by ALD of TiO2 film which can coat conformally and precisely onto the cylindrical Al roller mold. The Al roller mold was nanoimprinted onto polycarbonate (PC) and creates PC nanopillars of desired dimensions depending on the anodization condition and the number of ALD cycles. Thus, sub-100 nm pattern resolution can be produced directly on a cylindrical object, achieving a high resolution and seamless roller mold for continuous nanoimprint processing.