Investigation of Template Releasing Energy in Nanoimprint Lithography
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Investigation of Template Releasing Energy in Nanoimprint Lithography Tomoki Nishino1,2, Norihiro Fujikawa1,2, Hiroaki Kawata1,2 and Yoshihiko Hirai1,2 1 Physics and Electronics Engineering, Osaka. Prefecture University, Sakai, Japan 2 Core Res. for Evolutional Sci. and Technol. (CREST), JST, Kawaguchi, Saitama, Japan ABSTRACT To investigate template releasing process in nanoimprint lithography, template releasing energy (i.e. surface energy between the template and the resist polymer) in various releasing conditions is evaluated using multi-axial controlled releasing system. The releasing energy is in proportion to the surface free energy of the template, but does not depend on the velocity of releasing. Also, a peeling mode where the template is released from a single side and a lift-off mode where the template is removed in the perpendicular direction to the resist are examined. The result shows that the releasing energy by peeling mode is lower than that by lift-off modes. INTRODUCTION Nanoimprint lithography[1] is cost effective method for fine pattern transfer by pressing a fine template into polymer materials. In nanoimprint lithography, adhesion and/or friction between template and resist are important issues in template releasing process, because fracture or peeling away of the resist causes significant defects and impact on process yield. Several reports had been published about evaluation of template releasing force[2-6]. However, quantitative measurement of the template releasing forces is difficult because the results strongly depend on the rigidly of system. On the other hand, several reports have been published to quantify template releasing energy based on fracture dynamics[7-11]. To investigate the template releasing conditions, we newly developed test rig with multi-axial controlled releasing system and evaluate the releasing energy (surface energy between the resists and templates) on releasing velocity, surface free energy of template, and releasing modes such as peeling or lift-off releasing. EXPERIMENT Experimental tool and process To examine various releasing modes, multi-axis controlled releasing system is used. Figure. 1(a) shows schematic diagram of the test rig. A template bonded on base unit and UV curable resist polymer is coated on it. Over the resist, quartz plate as a substrate is adhered and the resist is cured by UV exposure through the quartz plate. The quartz plate is pushed up by three releasing rods, which are placed in axial symmetrically. Each rod is driven by precious stepping mother and controlled individually to examine various releasing modes. The bending displacement of the quartz plate is measured by three optical sensors (Keyence Si-F01) in preciously, where the resolution is 1 nm. The releasing force is measured at each rod using load cell (Minebea CB17-3K-11). To eliminate the energy loss at the side wall of the template, the edge of the template is tapered by 45 degrees chamfering. In this paper, we examined two template releasing modes. One is a peeling mode, where
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