Hot Embossing Lithography: Release Layer Characterization by Chemical Force Microscopy

Abstract

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).

Fully automated hot embossing processes utilizing high resolution working stamps

“…It enables the creation of two-dimensional and three-dimensional structures by applying elevated temperatures and high contact forces. 6 Another important aspect is the use of compliant layers that ensure imprint uniformity over large areas. Hot embossing processes are generally used to address different applications ranging from polymer-based lab-on-chip systems, where imprinting is performed on thick polymer sheets, to the fabrication of sub-100-nm features for biosensing or data recording applications, which require imprinting into thin ͑less than 200 nm͒ spin-on layers.…”

Fully automated hot embossing processes utilizing high resolution working stamps

“…The use of the soft working stamps materials allow a reliable and residual free separation of stamp and imprinted substrate after imprinting, which is a key issue for a fully-automated process runs. Usually an anti-adhesive mono layer deposited on the stamp surface [6] ensures a residual free separation from stamp to imprint substrate. Soft working stamps imply these self releasing properties in the bulk polymer which makes an additional deposition step prior imprinting dispensable.…”