Simple fabrication process for UV nanoimprint mold with embedded metal alignment marks for in-liquid alignment

In-liquid alignment is expected to be applied to UV nanoimprint lithography (UV-NIL) for the fabrication of integrated circuits that requires high-precision multilayer processes. It is not very easy to perform in-liquid alignment using quartz molds commonly used in UV-NIL, since alignment marks on the molds become invisible owing to the refractive index matching of quartz and UV-curable resin when alignment marks of a mold are filled with UV-curable resin. In this paper, we developed a simple fabrication process for quartz molds without the mentioned problem. We successfully fabricated Ti patterns, which served as high-contrast alignment marks, exclusively in the recess part of the mold mark. We also performed in-liquid alignment process using a mold with the marks and demonstrated less than sub-100-nm alignment accuracy.