Processing dependent behavior of soft imprint lithography on the 1-10-nm scale

This paper examines aspects of a soft nanoimprint lithography technique for operation at resolutions that approach the 1-nm regime. Systematic studies using polymer molds made with single walled carbon nanotubes (diameters between 0.5 and 5 nm) and high-resolution electron beam patterned layers of hydrogen silsesquioxane (line widths and heights ∼10 and 20 nm, respectively) as templates reveal a dependence of the resolution limits on the polymer processing conditions. In particular, using a single choice of polymers for the molds and the molded materials, imprint results show that the conditions for spin casting and curing the polymers determine, to a large degree, the resolution and replication fidelity that can be achieved. Optimized procedures enable imprinted polymer surfaces that have a root mean squared surface roughness of ∼ 0.26 nm or lower and a resolution as high as ∼1 nm. These characteristics are significantly better than previous results obtained using these same polymers with unoptimized conditions. A diversity of molded polymers, including Bisphenol-F epoxy resin, polyacrylic acid, and polyurethane, show similar high-fidelity imprinting capabilities. Different procedures enable accurate relief replication for features with modest aspect ratios and dimensions of ∼10 nm. The results indicate that choice of processing conditions is, in addition to materials selections, extremely important in achieving high-fidelity soft nanoimprint lithography in the 1-10-nm regime.