Hot Embossing Lithography: Release Layer Characterization by Chemical Force Microscopy
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J12.2.1
Hot Embossing Lithography: Release Layer Characterization by Chemical Force Microscopy Neil S. Cameron1*, Arnaud Ott1,2, Hélène Roberge1, and Teodor Veres1 1
IMI: National Research Council Canada, 75 blvd de Mortagne, Boucherville, QC, J4B 6Y4, Canada 2 ESIREM, Aile des Sciences de l’Ingénieur 9, avenue Alain Savary, BP 47870, 21078 Dijon cedex, France ABSTRACT Hot embossing lithography is a powerful method of replicating three-dimensional microand 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). INTRODUCTION High cost, slow serial throughput and resolution issues often handicap traditional micro and nanofabrication techniques. To meet the challenges of the microelectronics, optics, MEMS,
Figure 1: Samples of structures embossed on our EVG 520 HE. 500 nm lines (PMMA, upper-left);10, 20 µm posts (PCO, upper middle); micro-structures embossed in PCO (lower left and middle); 100 nm posts in PCO (right).
J12.2.2
BioMEMS, and other industries, researchers look to next generation lithography techniques. Among the technologies being re-invented to this end is hot-embossing lithography (HEL), an example of NanoImprint Lithography (NIL).1 HEL facilitates the fabrication of miniaturized devices with several advantages: virtually limitless resolution, low long-term cost, flexibility, production of copies which are the near-perfect replication of the pattern, and minimum dimensions in the sub-10 nm range. HEL is promising for optical, biological and data-storage devices as well as semiconductor integrated circuits.2 We have initiated a systematic study of rheological and interfacial effects for nanoimprint lithography. In its crudest form, a textured, but raw wafer is pressed into a thermoplastic polymer heated above its Tg. As the stamp progresses into the material, the displaced polymer is pushed into the ‘bulk’ reservoir for relatively thick thin-films. However as the stamp motifs reach the end of the stroke, the film remaining between the stamp and the substrate approaches the tribological regime where surface effects from both the stamp and the
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