• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.153-153
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• 2012

자연계에는 다양한 생물체들의 표면 구조가 특수한 기능을 갖는 형태로 되어 있다. 이와 같이 특수한 기능을 갖는 생물체들의 표면 구조는 일반적으로 화학적 조성과 표면의 더불어 나노와 마이크로 구조가 혼합되어 있는, 이른바 hierarchical 구조를 보인다. 그 중에서도 표면 초소수성 특성을 보이는 연잎의 표면과 같은 hierarchical 구조는 self-cleaning effect 등의 기능성 표면 제작에 활용이 가능하여 이를 모사하기 위한 연구가 활발히 진행중에 있다. 이에 본 연구에서는 연잎과 같은 초소수성을 띄는 ZnO nano-in-micro hierarchical 구조를 저온 공정을 통하여 다양한 기판에 제작하였다. 이를 위하여 ZnO 나노 입자 분산 레진을 제작하였고 UV imprinting 과 수열합성법을 통하여 마이크로 패턴 상부에 ZnO 나노 입자가 형성된 ZnO nano-in-micro hierarchical 구조를 형성하였다. 제작된 ZnO hierarchical 구조의 젖음 특성은 표면 접촉각이 $160^{\circ}C$이상인 초소수성을 보였으며, 제작 공정에는 고온의 열처리가 수반되지 않아 PET film 등 다양한 기판에 ZnO hierarchical 구조를 제작할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1849-1856
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• 2010

Glass/resin/glass laminate structures are used in the automobile, biological, and display industries. The sandwich structures are used in the micro/nanoimprint process to fabricate a variety of functional components and devices in fields such as display, optics, MEMS, and bioindustry. In the process, micrometer- or nanometer-scale patterns are transferred onto the substrate using UV curing resins. The demodling process has an important impact on productivity. In this study, we investigated the fracture behavior of glass/resin/glass laminates fabricated via UV curing. We performed measurements of the adhesion force and the interfacial energy between the mold and resin materials using the four-point flexural test. The bending-test measurements and the load-displacement curves of the laminates indicate that the fracture behavior is influenced by the interfacial energy between the mold and resin and the resin thickness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.63-67
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• 2017

In bioscience and biotechnology, the research of fundamental life mechanisms and their diseases caused by insufficiency is important. The study of a whole organism is difficult and sometimes impossible because of DNA, RNA, proteins, cellular organelles, various cells, and organs. Cell cultures can provide a simple method for researching cellular mechanisms and conditions, both in terms of physiological performance, and in response to chemical stimulation. According to conventional cell culture methodology, the flat surface is used with surface treatments for cell adhesion on the surface. Micro- and nanoscale patterns have been developed with chemical and biochemical modifications for cell immobilization. In this study, HeLa cell culture on nanostructures patterns was studied, including the 300 nm line and 150 nm pillar structures, using nanoimprint lithography and pyrrole as a biocompatible conducting polymer.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.225-230
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• 2006

Nanoimprint lithography (NIL) is a novel method of fabricating nanometer scale patterns. It is a simple process with low cost, high throughput and resolution. NIL creates patterns by mechanical deformation of an imprint resist and physical contact process. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting process. Stiction between the resist and the stamp is resulted from this physical contact process. Stiction issue is more important in the stamps including narrow pattern size and wide area. Therefore, the antistiction layer coating is very effective to prevent this problem and ensure successful NIL. In this paper, an antistiction layer was deposited and characterized by PECVD (plasma enhanced chemical vapor deposition) method for metal stamps. Deposition rates of an antistiction layer on Si and Ni substrates were in proportion to deposited time and 3.4 nm/min and 2.5 nm/min, respectively. A 50 nm thick antistiction layer showed 90% relative transmittance at 365 nm wavelength. Contact angle result showed good hydrophobicity over 105 degree. $CF_2$ and $CF_3$ peaks were founded in ATR-FTIR analysis. The thicknesses and the contact angle of a 50 nm thick antistiction film were slightly changed during chemical resistance test using acetone and sulfuric acid. To evaluate the deposited antistiction layer, a 50 nm thick film was coated on a stainless steel stamp made by wet etching process. A PMMA substrate was successfully imprinting without pattern degradations by the stainless steel stamp with an antistiction layer. The test result shows that antistiction layer coating is very effective for NIL.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.384-391
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• 2005

A polymer optical microring resonator, which is laterally coupled to a straight bus waveguide, has been proposed and demonstrated using a nanoimprint technique. The propagation loss of the ring waveguide and the optical power coupling between the ring and bus waveguides was calculated by using a beam propagation method, then the dependence of the device performance on them was investigated using a transfer matrix method. We have especially introduced an imprint stamp incorporating a smoothing buffer layer made of a silicon nitride thin film. This layer played an efficient role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing the scattering loss. As a result the overall Q factor of the resonator was greatly increased. Also it reduced the gap between the ring and bus waveguides effectively to enhance the coupling between them, without relying on the direct writing method based on an e-beam writer. As for the achieved device performance at the wavelength of 1550 nm, the quality factor, the extinction ratio, and the free spectral range were ~103800, ~11 dB, and 1.16 m, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.91-96
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• 2016

In this study, effects of demolding temperature (DT) on the formability and optical properties were evaluated in order to optimize thermal nanoimprint lithography for anti-reflective film. Characterization on optical property showed that optical performance was gradually enhanced as the DT increased up to $70^{\circ}C$ while the transmittance and the reflectance was degraded as the DT increased further to $100^{\circ}C$. In addition, similar behavior was observed from formability analysis. It was contributed to the formation of free volume and viscose flow. Therefore, it was concluded that the formability and optical property are highly influenced by the formation of free volume and viscous flow of polymer depending on the DT.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.41-46
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• 2017

In this study, rapid cooling method was proposed to improve the anti-scratch performance of anti-reflection film fabricated by nanoimprint lithography. Effects of cooling time on the mechanical properties and optical properties were evaluated. Pencil hardness measurements showed that anti-scratch performance enhanced as the cooling time increased while characterization on the optical property showed that reflectance on scratch increased as the cooling time increased. Therefore, it was concluded that the anti-scratch performance and optical properties are highly influenced by the cooling time. The observed results explained in terms of residual stress and free volume in polymeric materials.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.333-338
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• 2003

Nano-imprint lithography(NIL) is a polymer embossing technique, capable of transferring nano-scale patterns onto a thin film of thermoplastics such as polymethyl methacrylate(PMMA) using this parallel process. Feature size down 10 nm have been demonstrated. In NIL, the pattern is formed by displacing polymer material, which can be squeeze flow of a viscous liquid. Due to the size of the pattern, a thorough understood of the process through experiments may be very different. Therefore we nead to resort to numerical simulation on the embossing process. Generally, there are two ways of numerical simulation on nano-scale flow, namely top-down and bottom-up approach. Top-down approach is a way to simulate the flow assuming that polymer is a continuum. On the contrary, in the bottom-up approach, simulation is peformed using molecular dynamics(MD). However, as latter method is not feasible yet. we chose the top-down approach. For the numerical analysis, two dimensional moving grid was used since the moving grid can predict the flow front. Effects of surface tension as well as the slip at the boundary were also considered.

• Journal of the Semiconductor & Display Technology
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• v.14 no.3
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• pp.61-66
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• 2015

Recently, the major trends of NIL are high throughput and large area patterning. For UV NIL, if it can be proceeded in the non-vacuum environment, which greatly simplifies tool construction and greatly shorten process times. However, one key issue in non-vacuum environment is air bubble formation problem. In this paper, numerical analysis of bubble defect of UV NIL is performed. Fluent, flow analysis focused program was utilized and VOF (Volume of Fluid) skill was applied. For various resist-substrate and resist-mold angles, effects of velocity inlet and residual layer thickness of resist on bubble defect formation were investigated. The numerical analyses show that the increases of velocity inlet and residual layer thickness can cause the bubble defect formation, however the decreases of velocity inlet and residual layer thickness take no difference in the bubble defect formation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.21.2-21.2
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• 2009

발광다이오드는 에너지 변환 효율이 높고 친환경적인 장점으로 인하여 차세대 조명용 광원으로 각광받고 있다. 하지만 현재 발광다이오드는 낮은 광추출효율로 인하여 미래의 수요를 충족시킬 수 있을 만큼 충분한 성능의 효율을 나타내지 못하고 있다. 발광다이오드의 낮은 광추출효율은 반도체소재와 외부 공기와의 큰 굴절률 차이로 인하여 발생하는 전반사 현상에 기인한 것으로 이 문제를 해결하기 위하여 발광다이오드 소자의 발광면 및 기판을 텍스처링하는 방법이 중요하게 인식되고 있다. 하지만 현재까지 패턴의 구조에 따른 광추출 특성을 분석한 연구는 미진한 상황이다. 본 연구에서는 임프린팅 및 건식식각 공정을 이용하여 다양한 구조의 나노 및 micron 급 패턴을 발광다이오드의 p-GaN층에 형성하였다. 발광다이오드 기판 위에 하드마스크로 사용하기 위한 SiO2를 50nm 증착한 후 그 위에 UV 임프린팅 공정을 진행하여 폴리머 패턴을 형성시켰다. 임프린팅 공정으로 형성된 폴리머 패턴을 CF4CHF3 플라즈마를 이용하여 SiO2를 건식식각하였고, 이후에 SiCl4와 Ar 플라즈마를 이용한 ICP 식각 공정을 진행하여 p-GaN층을 100nm 식각하였다. 마지막으로 BOE를 이용한 습식식각 공정으로 p-GaN층에 남아있는 SiO2층을 제거하여 p-GaN층에 sub-micron에서 micron급의 홀 패턴을 형성하였다. Photoluminescence(PL) 측정을 통해서 발광다이오드 소자에 형성된 패턴의 구조에 따른 광추출 특성을 분석하였다.