Stamp-and-repeat UV-imprinting of spin-coated films: Pre-exposure and imprint defects

Defects to due resist pre-exposure as well as the relevance of the initial film thickness during stamp-and-repeat UV-assisted nanoimprint lithography are reported. The demolding force was found to be an indirect measure for the development of the photoinitiator concentration and for the curing behavior of the resist. Multiple imprints into pre-exposed resist are possible due to oxygen cure inhibition. The first curing defects due to significantly reduced photoinitiator concentrations in UVCur21SF resist occurred at accumulated doses of about three times the imprint dose. Molds having only a small fraction of patterned area require very thin initial films with an thickness being optimized for the low mold cavity volume. Helium is essential for the complete mold filling from such thin spin coated films.