, Austin, TX, USA), loaded into the SRNIL equipment, and leveled against a patterned quartz template/mould. For each target imprint area, nanoliter droplets of UV-curable, low-viscosity acrylate resist (MonoMat from Molecular Imprints, Inc.) were dispensed onto it and the quartz mould was brought into close proximity with the substrate, thus displacing the resist. This induced the resist to spread across the imprint field and fill up the mould relief via capillary action. A short exposure to UV light caused the polymerization of the monomers in the resist, after which the mould was separated from the substrate, leaving behind an inverse replica
of the mould pattern. This UV nanoimprint process was optimized for full pattern transfer while minimizing the residual material at the base of the recessed features and maintaining its uniformity across selleck chemical the field. The optimized nanoimprint process was step-and-repeated over the surface of the wafer Foretinib purchase to achieve wafer-scale
nanopatterning. The residual layer and underlying planarization layer were then removed by an oxygen reactive ion etching (RIE) process, thus exposing the underlying Si in these regions. Figure 1 Schematic diagram illustrating steps involved in step-and-repeat nanoimprint lithography (SRNIL) to produce pillar- or pore-patterned nanoimprinted wafers. In this work, three different pore-patterned quartz moulds were employed, allowing the corresponding inverse LY2874455 research buy patterns to be defined. The replicated patterns consist of (a) 300-nm period hexagonal array of 180-nm (facet-to-facet dimension) hexagonal pillars/studs, (b) 300-nm period square array of 200 nm × 100-nm rectangular pillars, and (c) 150-nm period hexagonal array of 50-nm diameter circular studs. By incorporating some degree of lateral etching in RIE after NIL to remove the residual material in the recessed regions, NIL pillars/studs can be narrowed, thereby providing some
tunability in the dimensions of the NIL features. The patterns are shown in Figure 2a,b,c. Figure 2 SEM images of the nanoimprinted samples after RIE. Inset shows the respective second cross-sections. (a) 300-nm period hexagonal array of 180-nm (facet-to-facet) hexagonal pillars/studs, (b) 300-nm period square array of 200-nm × 100-nm rectangular pillars, and (c) 150-nm period hexagonal array of 50-nm diameter circular studs. The patterned area in each 300-nm period mould is 10 mm × 10 mm, while that for the 150-nm period mould is 5 mm × 5 mm, enabling equal-sized imprints to be replicated over a wafer surface. An instance of wafer-level nanoimprinting by SRNIL is shown in Figure 3. In this case, 32 nanoimprinted fields were generated over the surface of a 4″ Si wafer.