Investigation of capillary bridges growth in NIL process

Many defects may appear during a NanoImprint process. Some of them are clearly related to the stamp or polymer surface properties, or the stamp pattern symmetry breakdown. The so-called capillary bridges appear in non printed areas and are related to capillary forces between the stamp surface and the polymer. One important issue is the understanding of their growth with respect to mold-polymer distance. A specific stamp, with cavity depths ranging from 12 to 224 nm, has been designed to control the capillary bridge growth. The resulting capillary bridges were characterized as a function of the cavity depth, printing temperature, resist thickness and printing time. Results show that capillary bridge number is strongly influenced by cavity depth and in a less extent by temperature. It appeared that no defects were induced for polymer-stamp gaps higher than 80 nm. Printing time effect has been also characterized and induced a change in the capillary bridge shape.