• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.63-66
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• 2005

Nanoimprint lithography (NIL) process at room temperature has been newly proposed in recent years to overcome the shape accuracy and sticking problem induced in a conventional NIL process. Success of the room temperature NIL relies on the accurate understand of the mechanical behavior of the polymer. Since a conventional NIL process has to heat a polymer above the glass transition temperature to deform the physical shape of the polymer with a mold pattern, viscoelastic property of polymer have major effect on the NIL process. However, rate dependent behavior of polymer is important in the room temperature NIL process because a mold with engraved patterns is rapidly pressed onto a substrate coated with the polymer by the hydraulic equipment. In this paper, finite element analysis of the room temperature NIL process is performed with considering the strain rate dependent behavior of the polymer. The analyses with the variation of imprinting speed and imprinting pattern are carried out in order to investigate the effect of such process parameters on the room temperature NIL process. The analyses results show that the deformed shape and imprint force is quite different with the variation of punch speed because the dynamic behavior of the polymer is considered with the rate dependent plasticity model. The results provide a guideline for the determination of process conditions in the room temperature NIL process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제12권5호
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• pp.1-8
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• 2013

Roll-based, nanoimprint lithography (Roll-NIL) is one effective method to produce large-area nanopatterns continuously. Systems and processes for Roll-NIL have been developed and studied for more than 15 years. Since the shapes of the stamp and the substrate for Roll-NIL can be plates, films, and rolls, there exist many concepts to design and implement roll-NIL systems. Combinations and variations of contact-methods for variously shaped stamps and substrates are analyzed in this paper. The contact-area can be changed by using soft materials such as polydimethylsiloxane (PDMS) or silicone rubber. Ultraviolet (UV) sources appropriate for the roll-to-plate or roll-to-roll process are introduced. Finally, two roll-to-plate nanoimprint lithography systems are illustrated.

• Proceedings of the KSME Conference
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.332-336
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• 2007

Temperature is an essential process variable in nanoimprint lithography(NIL) where the temperature varies between room temperature and above the glass transition temperature. To simulate NIL process, we employ both the Nose-Poincare method for temperature controlled molecular dynamics(MD) and force field for polymer material i.e. polymethyl methacrylate(PMMA), which is most widely selected as NIL resist. Nose-Poincare method, which convinces the conservation of Hamiltonian structure and time-reversal symmetry, overcomes the drawbacks inherent in the conventional methods such as Nose thermostat and Nose-Hoover thermostat. Thus, this method exhibits enhanced numerical stability even when the temperature fluctuation is large. To describe PMMA, we adopt the force field which account for bond stretch, bending, torsion, inversion, partial charge, and van der Waals energy.

• Journal of the Semiconductor & Display Technology
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• 제12권4호
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• pp.15-20
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• 2013

Nanoimprint lithography (NIL) is the next generation photolithography process in which the photoresist is dispensed onto the substrate in its liquid form and then imprinted and cured into a desired pattern instead of using traditional optical system. There have been considerable attentions on NIL due to its potential abilities that enable cost-effective and high-throughput nanofabrication to the display device and semiconductor industry. In this paper, a pressure vessel type imprinting system was used to imprint patterns with two type pressure values (25 bar, 30 bar) and two type pressure keeping times (5 min, 10 min). The height of transferred pattern and the thickness of residual layer were measured and effects of pressurization conditions - pressure and pressure keeping time - on the pattern transfer in thermal NIL were investigated.

• Transactions of the Korean Society of Machine Tool Engineers
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• 제18권1호
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• pp.68-75
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• 2009

A major disadvantage of thermal nanoimprint lithography(NIL) is the thermal cycle, that is, heating over glass transition temperature and then cooling below it, which requires a significant amount of processing time and limits the throughput. One of the methods to overcome this disadvantage is to make the processing temperature lower Accordingly, it is necessary to determine the effects on the processing parameters for thermal NIL at reduced temperatures and to optimize the parameters. This starts with a clear understanding of polymer material behavior during the NIL process. In this work, the squeezing and filling of thin polymer films into nanocavities during the low temperature thermal NIL have been investigated based upon a two-dimensional viscoelastic finite element analysis in order to understand how the process conditions affect a pattern quality; Pressure and initial polymer resist thickness dependency of cavity filling behaviors has been investigated.

• Journal of the Korean Society for Precision Engineering
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• 제28권4호
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• pp.513-520
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• 2011

The NIL processes have been studied to implement low cost, high throughput and high resolution application. A RNIL(roller NIL) is an alternative approach to flat nanoimprint lithography. RNIL process is necessary to transfer patterns on flexible substrates. Compared with flat NIL, RNIL has the advantages of better uniformity, less pressing force, and the ability to repeat the patterning process continuously on a large substrate. This paper studies the design, construction and verification of a thermal RNIL system. The proposed RNIL system can easily adopt the flat shaped hot plate which is one of the most important technologies for NIL. The NIL system can be used to transfer patterns from a flexible stamp to a flexible substrate, from a flexible stamp to a Si substrate, and from a roller stamp to a flexible substrate, etc. Patterning on flexible substrates is one of the key technologies to produce bendable displays, solar cells and other applications.

• Journal of the Semiconductor & Display Technology
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• 제9권4호
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• pp.19-23
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• 2010

Nanoimprint lithography (NIL) is one of the most versatile and promising technology for micro/nano-patterning due to its simplicity, high throughput and low cost. Recently, one of the major trends of NIL is large-area patterning. Especially, the research of the application of NIL to TFT-LCD field has been increasing. Technical difficulties to keep the uniformity of the residual layer, however, become severer as the imprinting area increases. In this paper we performed a numerical study for a large area NIL (the $2^nd$ generation TFT-LCD glass substrate ($370{\times}470$ mm)) by using finite element method. First, a simple model considering the surrounding wall was established in order to simulate effectively and reduce the computing time. Then, the volume of fluid (VOF) and grid deformation method were utilized to calculate the free surfaces of the resist flow based on an Eulerian grid system. From the simulation, the velocity fields and the imprinting pressure during the filling process in the NIL were analyzed, and the effect of the surrounding wall and the uniformity of residual layer were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제29권9호
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• pp.1169-1174
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• 2005

Imprint lithography is a promising method for high-resolution and high-throughput lithography using low-cost equipment. In particular, ultraviolet-nanoimprint lithography (UV-NIL) is applicable to large area imprint easily. We have proposed a new UV-NIL process using an elementwise patterned stamp (EPS), which consists of a number of elements, each of which is separated by channel. Experiments on UV-NIL are performed on an EVG620-NIL using the EPS with 3mm channel width. The replication of uniform sub 70 nm lines using the EPS is demonstrated. We investigate the nonuniformity of residual layer caused by wafer deformation in experiment with varying wafer thickness. Severely deformed wafer works as an obstacle in spreading of dropped resin, which causes nonuniformity of thickness of residual layer. Numerical simulations are conducted to analyze aforementioned phenomenon. Wafer deformation in the process is simulated by using a simplified model, which is a good agreement with experiments.

• Transactions of the Korean Society of Machine Tool Engineers
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• 제17권5호
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• pp.76-81
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• 2008

Nanoimprint lithography(NIL) is an emerging technology enabling cost-effective and high-throughput nanofabrication. Among NILs, significant efforts from both academia and industry have been put in UV NIL research and development because of its ability to pattern at room temperature and at low pressure. In UV NIL, there may be in-line set-up error of the stamp and the substrate. To compensate this error, the dummy blocks are put on the stamp and pressurized uniformly. Contact problems between the stamp and the photoresist layer on the substrate are often happened, which results in the non-uniform residual layer In this paper, the pressurization method on the dummy block is investigated by the finite element method. A new method is recommended and evaluated far the uniform stamp deformation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.86-90
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• 2006

Nanoimprint lithography (NIL) is a novel method to fabricate nanometer scale patterns. It is a simple process with low cost, high throughput and high resolution. NIL process creates patterns by the mechanical deformation of imprint resist and physical contact process. This physical contact process causes the stiction between the resist and the stamp. Stiction becomes a key issue especially in the stamps including narrow pattern size and wide area during NIL process development. The antistiction layer coating using fluorocarbon is very effective to prevent this problem and ensure successful NIL. In this paper, the concept of antistiction coating is explained and different preparation methods for nanoimprinting are briefly discussed.