Study on porous silicon template for nanoimprint lithography

Abstract

The template for naoimprint lithography having a nano-sized structure was usually fabricated by traditional lithography such as extreme ultraviolet (EUV) lithography, focused ion beam (FIB) lithography, electron beam (EB) lithography. However, these approaches are always time-consuming and inefficiency which limits the potential application in nanoimprint lithography. To find a simple and low-cost method to fabricate the mold for nanoimprint lithography, and to improve the application in nanoimprint lithography have become the research focus. Instead of being formed by traditional lithography, the anodic aluminum oxide (AAO), with highly regular structures and high pore density, is the mold to achieve periodic structures for nanoimprint lithography. In this work, we successfully transfer a 2D nanoporous array structure to the Si surface via the nanoimprint lithography and AAO. The pore diameter and the interpore distance of the porous silicon (PS) are well consistent with that of AAO template. The interval, the diameter, and the height of the hexagonal array structure are 350–560 nm, 170–480 nm, and 200 nm, respectively. We have tested the Raman spectrum under the excitation by lasers of wavelength 514 nm. According to the results, two samples each exhibits a peak at 520 cm-1 and no frequency shift is observed with the Si characteristic Raman peak, indicating that the PS was not extensively damaged by the ICP etching process. Raman intensity in the structured Si is almost enhanced by a factor of 12 as compared with the case on polished Si, which will greatly benefit the application of Si-based optical devices. Thus, we have realized the replica of the PS template and obtained a nanopillar soft template via the hot embossing lithography.