• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.259-264
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• 2004

The hot embossing process as a method for the fabrication of polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this paper, we carried out experimental studies and numerical simulations in order to understand the viscous flow of polymer film during hot embossing process. As the initial step of quantitating the hot embossing process, simple parametric studies for the embossing conditions have been carried out using high resolution masters which patterned by DRIE process. Under different embossing times and pressures, the viscous flow of PMMA films into micro/nano cavities has been investigated. Also, the viscous flow during the hot embossing process has been simulated by the continuum based FDM analysis considering micro/nano effect, such as surface tension and contact angle.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.159-164
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• 2005

The Hot Embossing Lithography(HEL) as a method fur the fabrication of the nanostructure with polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this paper, we carried out experimental studies and numerical simulations in order to understand the viscous flow of the polymer (PMMA) film during the hot embossing process. To grasp the characteristics of the micro patterning rheology by process parameters (embossing temperature, pressure and time), we have carried out various experiments by using the nickel-coated master fabricated by the deep RIE process and the plasma sputtering. During the hot embossing process, we have observed the characteristics of the viscoelastic behavior of polymer. Also, the viscous flow during the hot embossing process has been simulated by the continuum based FDM(Finite Difference Method) analysis considering the micro effect, such as a surface tension and a contact angle.

• 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.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1025-1029
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• 2003

We studied the cross-sectional profiles of deformed thermoplastics in hot embossing process and compared with melt flow index for various embossing conditions such as embossing temperature, embossing pressure and initial thickness of the thermoplastics. The fastest embossing times for complete penetration of the cavities were obtained at temperature greater than $60^{\circ}C$ above glass transition temperature (Tg). When the melt flow index of polymer is low, the penetration ratio does not become large even if the embossing pressure increases. The complete occupation of the cavities was easier obtained with high melt flow index polymer than low melt flow index polymer at the same process condition. We believe these results can be very useful for optimizing nanostructured hot embossing also known nanoimprinting process conditions.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.71-71
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• 2003

Hot embossing has been widely accepted as an alternative to photolithography in generating patterns on polymeric substrates. The optimization of embossing process should be accomplished based on polymer substrate materials. In this paper, the effect of polymer substrates on nano scale hot embossing process was studied. Silicon molds with nano size patterns were fabricated by e-beam direct writing. Molds were coated with self-assembled monolayer (SAM) of (1, 1, 2.2H -perfluorooctyl)-trichlorosilane to reduce the stiction between mold and substrates. For an embossing, pressure of 55, 75 bur, embossing time of 5 min and temperature of above transition temperature were peformed. Polymethylmethacrylates (PMMA) with different molecular weights of 450,000 and 950,000, MR-I 8010 polymer (Micro Resist Technology) and polyaliphatic imide copolymer were applied for hot embossing process development in nano size. These polymers were spun coated on the Si wafer with the thickness between 150 and 200 nm. The nano size patterns obtained after hot embossing were observed and compared based on the polymer properties by scanning electron microscopy (SEM). The imprinting uniformity dependent on the Pattern density and size was investigated. Four polymers have been evaluated for the nanoimprint By optimizing the process parameters, the four polymers lead to uniform imprint and good pattern profiles. A reduction in the friction for smooth surfaces during demoulding is possible by polymer selection.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.228-232
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• 2003

Mircolens and microlens arrays are realized using a novel fabrication technology based on the exposure of a resist, usually PMMA, to deep X-rays and subsequent thermal treatment. Hot embossing process is also studied for mass production. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness of several nm. The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses were produced through the effects of volume change, surface tension. and reflow during thermal treatment of irradiated PMMA. A hot embossing machine is designed and manufactured with a servo motor transfer system. The hot embossing process follows the steps of heating mold to the desired temperature, embossing a mold insert on substrate. cooling mold to the de-embossing temperature. and de-embossing. Microlenses were produced with diameters ranging from 30 to 1500 ${\mu}{\textrm}{m}$. The surface X-ray mask is also fabricated to realize microlens arrays on PMMA sheet with a large area.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.499-500
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.911-912
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.627-628
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• 2008

• 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.