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-mn 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 similar to 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 similar to 0.26 nm or lower and a resolution as high as similar to 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 similar to 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.