• 반도체디스플레이기술학회지
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• 제10권4호
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• pp.53-59
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• 2011

Recently there have been considerable attentions on nanoimprint lithography (NIL) by the display device and semiconductor industry due to its potential abilities that enable cost-effective and high-throughput nanofabrication. Although one of the current major research trends of NIL is large-area patterning, the technical difficulties to keep the uniformity of the residual layer become severer as the imprinting area increases more and more. In this paper we focused on the deformation of the $2^{nd}$ generation TFT-LCD sized ($370{\times}470mm^2$) large-area soft mold in the UV imprinting process. A mold was fabricated with PDMS(Poly-dimethyl Siloxane) layered glass back plate(t0.5). Besides, the mold includes large surrounding wall type protrusions of 1.9 mm width and the via-hole(7 ${\mu}m$ diameter) patterend area. The large surrounding wall type protrusions cause the proximity effect which severely degrades the uniformity of residual layer in the via-hole patterend area. Therefore the deformation of the mold was calculated by finite element analysis to assess the effect of large surrounding wall type protrusions and the flexiblity of the mold. The deformation of soft mold was verified by the measurements qualitatively.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.349-352
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• 2014

Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i.e., meshed pore, was produced.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.698-701
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• 2005

We have investigated experimentally a nano patterning using electron beam lithography for the nickel stamper fabrication. Recently, DVD and Blu-ray disk(BD) have nano-scale patterns in order to increase the storage density. Specially, BD has 100nm-scale patterns which are generally fabricated by electron beam lithography. In this paper, we found optimum condition of electron-beam lithography for 100nm-scale patterning. We controlled various conditions of EHP(acceleration voltage), beam current, dose and aperture size in order to obtain optimum conditions. We used 100nm-thick PMMA layer on a silicon wafer as photoresist. We found that EHP was the most dominant factor in electron-beam lithography.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.91-96
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• 2010

In recent years there have been considerable attentions on nanoimprint lithography (NIL) by the display device and semiconductor industry due to its potential abilities that enable cost-effective and high-throughput nanofabrication. Although one of the current major research trends of NIL is large-area patterning, the technical difficulties to keep the uniformity of the residual layer become severer as the imprinting area increases more and more. In this paper we consider the roll-to-plate type imprinting process. In the process a glass mold, which is placed upon the 2nd generation TFT-LCD glass sized substrate(370${\yen}$470 mm), is rolled by a rubber roller to achieve a uniform residual layer. The pressure distribution on the glass mold by rolling of the rubber roller is crucial information to analyze mold deformation, transferred pattern quality, uniformity of residual layer and so forth. In this paper the quantitative pressure distribution induced by rolling of the rubber roller was calculated with finite element analysis under the assumption of Neo-Hookean hyperelastic constitutive relation. Additionally the numerical results were verified by the experiments.

• 한국전기전자재료학회논문지
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• 제34권4호
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• pp.262-268
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• 2021

For the past several decades, various next-generation patterning methods have been developed to obtain well-designed nano-to-micro structures, such as imprint lithography, nanotransfer printing (nTP), directed self-assembly (DSA), E-beam lithography, and so on. Especially, nTP process has much attention due to its low processing cost, short processing time, and good compatibility with other patterning techniques in achieving the formation of high-resolution functional patterns. To transfer functional patterns onto desirable substrates, the use of soft materials is required for precise replication of master mold. Here, we introduce a simple and practical nTP method to create highly ordered structures using various polymeric replica materials. We found that polymethyl methacrylate (PMMA), polystyrene (PS), and polyvinylpyridine (PVP) are possible candidates for replica materials for reliable duplication of Si master mold based on systematic analysis of pattern visualization. Furthermore, we successfully obtained well-defined metal and oxide nanostructures with functionality on target substrates by using replica patterns, through deposition and transfer process. We expect that the several candidates of replica materials can be exploited for effective nanofabrication of complex electronic devices.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.411-411
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• 2012

Over the recent years, surface enhanced Raman spectroscopy (SERS) has dramatically grown as a label-free detecting technique with the high level of selectivity and sensitivity. Conventional SERS-active nanostructured layers have been deposited or patterned on rigid substrates such as silicon wafers and glass slides. Such devices fabricated on a flexible platform may offer additional functionalities and potential applications. For example, flexible SERS-active substrates can be integrated into microfluidic diagnostic devices with round-shaped micro-channel, which has large surface area compared to the area of flat SERS-active substrates so that we may anticipate high sensitivity in a conformable device form. We demonstrate fabrication of flexible SERS-active nanostructured substrates based on soft-lithography for simple, low-cost processing. The SERS-active nanostructured substrates are fabricated using conventional Si fabrication process and inkjet printing methods. A Si mold is patterned by photolithography with an average height of 700 nm and an average pitch of 200 nm. Polydimethylsiloxane (PDMS), a mixture of Sylgard 184 elastomer and curing agnet (wt/wt = 10:1), is poured onto the mold that is coated with trichlorosilane for separating the PDMS easily from the mold. Then, the nano-pattern is transferred to the thin PDMS substrates. The soft lithographic methods enable the SERS-active nanostructured substrates to be repeatedly replicated. Silver layer is physically deposited on the PDMS. Then, gold nanoparticle (AuNP) inks are applied on the nanostructured PDMS using inkjet printer (Dimatix DMP 2831) to deposit AuNPs on the substrates. The characteristics of SERS-active substrates are measured; topology is provided by atomic force microscope (AFM, Park Systems XE-100) and Raman spectra are collected by Raman spectroscopy (Horiba LabRAM ARAMIS Spectrometer). We anticipate that the results may open up various possibilities of applying flexible platform to highly sensitive Raman detection.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.596-602
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• 2018

최근 나노임프린트 리소그래피 공정이 마이크로/나노 스케일의 소자 개발에 있어서 경제적으로 대량 생산할 수 있는 기술로 주목 받고 있다. 자외선경화 방식의 나노임프린트의 경우 상온 및 저압의 장점과 함께 비진공 환경에서 공정을 통하여 설비 비용의 저감과 생산공정의 고속화를 달성할 수 있다. 그러나 이 경우 비진공 환경에서 발생하는 기포결함의 문제를 해결해야만 한다. 본 연구에서는 비진공 환경에서의 자외선경화 방식의 나노임프린트 공정에서 몰드 중공부 단면의 형상과 기포결함 발생 관계를 연구하였다. 일반적으로 많이 사용되는 사각형 단면과 타원형 단면 그리고 삼각형 단면에 대하여 2차원 유동해석 및 VOF 방법을 통하여 기포결함을 시뮬레이션 하였고 단면의 형상과 다양한 접촉각에 따른 유동선단의 특성을 분석하였다. 해석결과 몰드 중공부 형상은 기포결함 발생에 매우 중요한 영향을 미치며, 고려된 형상 모두 몰드와의 접촉각이 작을수록, 기판과의 접촉각이 클수록 기포결함 발생 가능성이 작아짐을 알 수 있었다. 또한 타원형 형상이 기포결함 발생방지 측면에서 가장 효과적임을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.3.2-3.2
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• 2011

In recent years, inkjet printing technology has received significant attention as a micro/nanofabrication technique for flexible printing of electronic circuits and solar cells, as well for biomaterial patterning. It eliminates the need for physical masks, causes fewer environment problems, lowers fabrication costs, and offers good layer-to-layer registration. To fulfill the requirements for use in the above applications, however, the inkjet system must meet certain criteria such as high frequency jetting, uniform droplet size, high density nozzle array, etc. Existing inkjet devices are either based on thermal bubbles or piezoelectric pumping; they have several drawbacks for flexible printing. For instance, thermal bubble jetting has limitations in terms of size and density of the nozzle array as well as the ejection frequency. Piezoelectric based devices suffer from poor pumping energy in addition to inadequate ejection frequency. Recently, an electrohydrodynamic (EHD) printing technique has been suggested and proposed as an alternative to thermal bubble or piezoelectric devices. In EHD jetting, a liquid (ink) is pumped through a nozzle and a strong electric field is applied between the nozzle and an extractor plate, which induce charges at the surfaces of the liquid meniscus. This electric field creates an electric stress that stretches the meniscus in the direction of the electric field. Once the electric field force is larger than the surface tension force, a liquid droplet is formed. An EHD inkjet head can produce droplets smaller than the size of the nozzle that produce them. Furthermore, the EHD nano-inkjet can eject high viscosity liquid through the nozzle forming tiny structures. These unique features distinguish EHD printing from conventional methods for sub-micron resolution printing. In this presentation, I will introduce the recent research results regarding the EHD nano-inkjet and the printing system, which has been applied to solar cell or thin film transistor applications.

• 공업화학
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• 제20권6호
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• pp.586-592
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• 2009

나노 크기의 배향성을 갖는 구조물의 제작은 자연에 존재하는 여러 가지 형상의 모방을 가능하게 한다. 고분자는 가격이 매우 저렴하며 합성과 가공 그리고 그 구조가 잘 알려져 있는 장점을 갖고 있어 필름(film)의 표면에 이러한 나노 구조물을 제작하고 나노 구조의 특성을 발현하는데 손쉽게 활용할 수 있는 재료이다. 나노 구조물을 제작하는 방법 중 양극산화를 통하여 제작한 다공성 알루미나 템플레이트(porous alumina template)는 매우 규칙적으로 정렬되어 있고 제어하는 공정이 비교적 쉽고 경제적이기 때문에 이를 이용한 연구가 매우 활발하게 진행되고 있다. 본 총설에서는 양극산화 알루미나 템플레이트의 제작과 이를 이용한 나노 구조 고분자 필름의 제작을 설명하고 이러한 나노 구조 필름의 응용범위 및 응용에 필요한 특성에 대하여 기술하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.549-549
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• 2012

Early detection of cancer biomarkers in the blood is of vital importance for reducing the mortality and morbidity in a number of cancers. From this point of view, immunosensors based on nanowire (NW) and carbon nanotube (CNT) field-effect transistors (FETs) that allow the ultra-sensitive, highly specific, and label-free electrical detection of biomarkers received much attention. Nevertheless 1D nano-FET biosensors showed high performance, several challenges remain to be resolved for the uncomplicated, reproducible, low-cost and high-throughput nanofabrication. Recently, two-dimensional (2D) graphene and reduced GO (RGO) nanosheets or films find widespread applications such as clean energy storage and conversion devices, optical detector, field-effect transistors, electromechanical resonators, and chemical & biological sensors. In particular, the graphene- and RGO-FETs devices are very promising for sensing applications because of advantages including large detection area, low noise level in solution, ease of fabrication, and the high sensitivity to ions and biomolecules comparable to 1D nano-FETs. Even though a limited number of biosensor applications including chemical vapor deposition (CVD) grown graphene film for DNA detection, single-layer graphene for protein detection and single-layer graphene or solution-processed RGO film for cell monitoring have been reported, development of facile fabrication methods and full understanding of sensing mechanism are still lacking. Furthermore, there have been no reports on demonstration of ultrasensitive electrical detection of a cancer biomarker using the graphene- or RGO-FET. Here we describe scalable and facile fabrication of reduced graphene oxide FET (RGO-FET) with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}$ 1-antichymotrypsin (PSA-ACT) complex, in which the ultrathin RGO channel was formed by a uniform self-assembly of two-dimensional RGO nanosheets, and also we will discuss about the immunosensing mechanism.