• Macromolecular Research
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• v.12 no.5
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• pp.437-442
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• 2004

We have fabricated a polymeric waveguide by using a hot embossing technique and have investigated its propagation loss. The replication of waveguide channels through the use of a hot embossing technique is of interest as a single-step process that could deliver surface roughnesses far smaller than the wavelength. We have evaluated experimentally that the sidewall roughness has a dominant effect on insertion losses of the multimode polymeric waveguide. The propagation loss of the waveguide decreased dramatically upon decreasing the sidewall roughness of the channel. We have confirmed that the preparation of waveguides having nanometer-scale sidewall roughness and 0.1 dB/cm propagation loss is possible when using the hot embossing technique.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.305-310
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• 2004

The Hot Embossing Lithography(HEL) as a method for the fabrication of nanostructure with polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this study, we investigated the characteristics of hot embossing lithography as a nanoreplication technique. To grasp characteristics of nano patterning rheology by process parameters(embossing temperature, pressure and time), we have carried out various experiments by using the DVD(400nm pattern width) and Blu-ray nickel stamps(150nm pattern width). During the hot embossing process, we have observed the characteristics of the size effect. The quality of products made by hot embossing is affected by its cooling shrinkage. The demolding process at the glass transition temperature results in low quality because of the shrinkage of the polymer. Therefore, the quantification of the temperature condition is essential for the replication of high quality.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.199-203
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• 2017

Hot embossing techniques are used to engrave patterns on plastic substrates. Roll based hot embossing uses a heated roll for a continuous process. A heated roll with relief patterns is impressed on a preheated plastic substrate. Then, the substrate is cooled down quickly to prevent thermal shrinkage. The roll speed is normally very slow to ensure substrate temperature increase up to the glass transition temperature. In this paper, we propose a noncontact preheating technique using focused infrared light. The infrared light is focused as a line beam on a plastic substrate using an elliptical mirror just before entering the hot embossing roll. The mid range infrared light efficiently raises the substrate temperature. For preliminary tests, substrate deformation and temperature changes were monitored according to substrate speed. The experiments show that the proposed technique is a good possibility for high speed hot embossing.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.64-70
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• 2007

A long-exposing technique (LET) has been conducted to create nanoscale patterns applicable to diverse micro-devices using two-photon polymerization (TPP). By the weakly-polymerized region via the LET, double-layered embossing patterns can be fabricated simply in a single step. The LET makes possible a voxel and its surrounding to be fully grown into more than 500 nm in lateral size and weakly-polymerized region (WPR), respectively. In the WPR. interconnecting ribs between voxels are generated, and they lead to the creation of double-layered dot patterns. Moreover, by controlling the distance between voxels, various shapes of interconnecting rib can be fabricated when the LET is applied. Various embossing patterns were fabricated to evaluate the usefulness of the proposed technique as a novel nanopatterning technique in TPP.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.223-227
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• 2002

Polymeric multi-mode optical waveguides were fabricated for parallel optical interconnection. Waveguide structures were molded by a Ni mold master using a hot embossing technique. The Ni mold master was manufactured by LIGA process. Multimode optical waveguides with a 48$\times$47 ${\mu}{\textrm}{m}$$^2$cross-section were produced by a simple two-step process. The propagation losses of the multimode waveguide measured at 0.85 ${\mu}{\textrm}{m}$ and 1.3 ${\mu}{\textrm}{m}$ wavelengths were 0.38 dB/cm and 0.66 dB/cm, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.191-194
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• 2007

In hot embossing lithography which has shown to be a good method to fabricate polymeric patterns for IT and bio components, it is very important to determine the proper process conditions of pressure, temperature, and time. It is also a key factor for predicting the optical properties of final product to calculate residual stress distribution after the embossing process. Therefore, to design the optimum process with right conditions, the ability to predict viscoelastic behavior of polymer during and after the hot embossing process is required. The objective of the present investigation is to establish simulation technique based on constitutive modeling of polymer with experiments. To analyze deformation behavior of viscoelastic polymer, the large strain material properties were obtained from quasi-static compression tests at different strain rates and temperatures and also stress relaxation tests were executed. With this viscoelastic material model, finite element simulation of hot embossing was executed and stress distribution is obtained. Proper process pressure is very important to predict the defect and incomplete filling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1168-1170
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• 2005

Nanoimprint Lithography(NIL) has increasingly been recognized as a key manufacturing technology for nanosized feature. One of the most important task for nanoimprint lithography is to provide the imprinting stamp with low price. The Stamp fabricated with Si based material by e-beam lithography, RIE is extremely expensive and its throughput is very limited and PDMS replica is too soft to hold high imprinting pressure.(>5atm) In this study, we present the imprinting stamp which can be easily replicated from original mold and is based on PVC film. Replication of original Si mold to PVC film was done by Hot embossing technique, ($120^{\circ}C$ of Temperature, 20 atm applied) As small as 100nm patterns were successfully transferred into PVC film. The size of stamp was up to 100mm in diameter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1106-1110
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• 2005

We fabricated (110) silicon hard master by using anisotropic wet etching for embossing. The etching chemical for the silicon wafer was a TMAH $25\%$ solution. The anisotropic wet etching produces a smooth sidewall surface and the surface roughness of the fabricated master is about 3 nm. After spin coating an organic-inorganic sol-gel hybrid material on a silicon substrate, we employed hot embossing technique operated at a low pressure and temperature to form patterns on the silicon substrate by using the fabricated master. We successfully fabricated the multi-mode planar optical waveguides showing low propagation loss of 0.4 dB/cm. The surface roughness of embossed patterns was uniform for more than 10 times of the embossing processes with a single hydrophobic surface treatment of the silicon hard master.

• Journal of the Korean Ceramic Society
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• v.42 no.10 s.281
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• pp.645-648
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• 2005

To fabricate a (100) silicon hard master, we used anisotropic wet etching for the embossing. The etching chemical for the sili­con wafer was a TMAH 25$\%$ solution. The anisotropic wet etching produces a smooth sidewall surface inclined at 54.7°, and the surface roughness of the fabricated master is about 1 nm. After spin coating an organic-inorganic sol-gel hybrid resin on a silicon substrate, we used the fabricated master to form patterns on the silicon substrate. Thus, we successfully obtained patterns via the hot embossing technique with the (100) silicon hard master. Moreover, by using a single hydrophobic surface treatment of the master, we succeeded in achieving uniform surface roughness of the embossed patterns for more than ten embossments.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.589-593
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• 2005

Nanoimprinting lithography (NIL) is known as a suitable technique for fabricating nano and micro structures of high definition. Hot embossing is one of NIL techniques and can imprint on thin films and bulk polymers. Key issues of hot embossing are time and expense needed to produce a stamp withstanding a high temperature and pressure. Fabrication of a metal stamp such as an electroplated nickel is cost intensive and time consuming. A ceramic stamp made by silicon is easy to break when the pressure is applied. In this paper, a plastic stamp using a high temperature epoxy was fabricated and tested. The plastic stamp was relatively inexpensive, rapid to produce and durable enough to withstanding multiple hot embossing cycles. The merits of low viscosity epoxy solutions were a fast degassing and a rapid filling the microstructures. The hot embossing process with plastic stamp was performed on PMMA substrates. The hot embossing was conducted at 12.6 bar, $120^{\circ}C$ and 10 minutes. An imprinted PMMA wafer was almost same value of the plastic stamp after 10 times embossing. Entire fabrication process from silicon master to plastic stamp was completed within 12 hours.