Hot Embossing Lithography: Release Layer Characterization by Chemical Force Microscopy

Hot embossing lithography is a powerful method of replicating three-dimensional micro-and nano-structures (see Figure 1) using a stamp that is pressed into a heat-softened polymer resin. Cooling below the glass-transition temperature (Tg) of the polymer cures the motifs and the stamp and substrate are then separated. Successful replication is therefore contingent on interfacial interactions during the embossing phase and most importantly during the separation or release phase. Various organo- and perfluoro-silane release layers have been proposed and studied.We have employed variable temperature chemical force microscopy (VT-CFM) using tips silanized with four different SAMs interacting with a thin-film of poly(cyclic olefin), (PCO). The silanized-tip/polymer interaction was studied over a temperature range spanning the Tg of the PCO (∼373 K). Adhesion between a saturated hydrocarbon-decorated tip (OTS) and PCO was comparatively strong (170 nN) 30 K above the Tg of the polymer. Adhesion among the perfluorinated tips was 20 to 50 nN lower at 373 K with a relative increase in perfluoromethyl groups (w/w).