Adhesion force measurement between the stamp and the resin in ultraviolet nanoimprint lithography--an investigative approach.

In the ultraviolet nanoimprint lithography (UV-NIL) process, the surface interaction between the mold and the resist is essential along with molecularly clean separation of the mold from the surface of the cured resist for repeated use of the mold. In our present study, various mold-resin combinations have been examined by a tensile strength method to determine the adhesion force between a mold with a relief pattern and a photocurable resin. The adhesion force of polymer molds of the fluorine-containing polymers perfluoropolyether dimethacrylate (PFPE) and polydimethylsiloxane (PDMS) were compared to those of hard molds such as Si and quartz against several commercial UV-NIL resins. Eventually, PFPE with higher molecular weight-AMONIL-was found to be an excellent UV-NIL mold-resin combination with the lowest adhesion force per unit area (20 kPa). In particular, the 36-fold repeated imprinting with a high molecular weight PFPE mold showed only a slight increase of adhesion force by 36 kPa with molecularly clean release from the AMONIL resin, whereas a surface-modified PDMS mold revealed highly increased adhesion from an initial 20 kPa to 120 kPa after repeated use.