Molecular Dynamics Study on Resolution in Nanoimprint Lithography for Glass Material
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Molecular Dynamics Study on Resolution in Nanoimprint Lithography for Glass Material Kazuhiro Tada, Masaaki Yasuda*, Yoshihisa Kimoto, Hiroaki Kawata, and Yoshihiko Hirai Department of Physics and Electronics, Graduate school of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Japan
ABSTRACT A theoretical study of resolution in nanoimprint lithography (NIL) has been carried out using molecular dynamics (MD) simulation. We have performed a MD simulation for glass NIL, monitored the friction force during entire NIL process and evaluated the deformed shapes of glass patterns after the mold releasing. The resolution in NIL is governed by the maximum tensile stress acting on the glass, which is induced by the friction force during the mold releasing. Based on the distribution of average number density of atoms in the molded glass, the ultimate resolution in the glass NIL has been proved to be 0.4 nm.
INTRODUCTION Nanoimprint lithography (NIL) is a promising technology to realize cost-effective nanostructure production [1-8]. The resolution of NIL is one of the most important interests in both scientific and industrial points of views. Single-nanometre resolution has been demonstrated using polymer material [9,10]. Nevertheless, inorganic materials must achieve the advanced resolution due to fine units structure [11]. Experimental evaluation of the resolution is quite difficult in NIL because ultra fine mold could not be easily obtained in conventional technologies. On the other hand, molecular dynamics (MD) simulation could give a perspective of the resolution in NIL process in the atomic scale. The importance of MD analysis is increasing in recent high resolution NIL [12-15]. However, any theoretical study on the resolution in NIL has not been achieved. In this study, the resolution in NIL is investigated through a MD simulation for inorganic SiO2 glass material.
SIMULATION MODEL Figure 1 shows a schematic diagram of the numerical simulation system. The dashed element in Fig. 1(a) shows a unit cell in the simulation system. A single-crystal Si mold is pressed into a SiO2 glass as shown in Fig. 1(b). Melt-quench (MQ) method is used to form the initial structures of the SiO2 glass model by MD [16]. Born-Mayer-Huggins type potential, which includes three-body term [16], is adopted to describe the interactions between atoms in the SiO2 glass. Morse potential is used to simulate the interfacial behavior between the Si mold and *
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the SiO2 glass [17]. Morse potential is often applied to nano-tribological phenomena, such as sliding and nanoindentation [18-22]. The Si mold is treated as a rigid body. The bottom region of the SiO2 glass film of 1 nm thickness is also assumed to be rigid as a substrate. The thickness of the glass is 2.5 nm. The mold is pressed to and released from the glass under the constant speed of 5 m/s. The temperature of the glass is kept to be 1500 K during the mold pressing using the velocity-scaling method. Aft
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