Influence of mold depth on capillary bridges in nanoimprint lithography

Nanoimprint lithography (NIL) processes are often plagued by different kinds of defects. The so-called capillary bridge is related to capillary forces between the stamp surface and the polymer during the pressing process. These defects affect both the printed and unprinted areas of the polymer film. Implementation of NIL as an industrial process requires that these defects be understood and minimized. As such, establishing a relationship between capillary bridge growing and pressing conditions, specifically the mold to polymer distance, is a key step. Two NIL stamps with various feature depths (12 - 224 nm) were studied in this work to establish a link between bridge formation and mold filling. Printing processes were performed using small forces to guarantee contact between the mold and resist without totally filling stamp cavities. The resulting capillary bridges were characterized as a function of cavity depth and printing temperature. Results indicate that the number of defects is strongly influenced by the cavity size for depths < 80 nm as well as printing temperature. (c) 2006 American Vacuum Society.