Reproducibility and homogeneity in step and repeat UV-nanoimprint lithography

A new approach to step and repeat UV-based nanoimprint lithography (UV-NIL) using sequential imprints on a large-area spin-coated surface is presented. A detailed study has been performed in order to assess the reproducibility and homogeneity of the process. The imprint tool features a movable wafer stage for 4 in. wafers, allowing the high precision vertical and lateral positioning necessary for a step and repeat imprint technique. More than 1000 imprints with a single mold were performed without any cleaning of the mold. This demonstrates the high asymmetry between the detachment from tile mold and the adhesion to the substrate achieved, an essential issue for reproducibility. Furthermore, the uniformity of the residual resist thickness was analyzed. The measured thicknesses, 57 ± 12.5 nm and 118 ± 12.5 nm for initial film thicknesses of 210 and 275 nm, respectively, revealed the uniformity to be sufficient for accurate pattern transfer.