Earticle

Nanoimprint is an emerging lithographic technology that promises high-throughput patterning of nanostructures. Here, we attempt to give an overview of the trend of the Nanoimprint lithography (NIL) technology in Korea and China. First NIL fundamentals including thermal NIL and UV-NIL are introduced. And technical issues around stamp fabrication are discussed. To illustrate the potentials of the techniques, some applications of NIL are described. Next, nanotechnology and NIL technology of Korea and China are discussed in the view of the investment budget, technology strategy, driving system and academic conferences.

Using UV nanoimprint lithography(UV-NIL), 1-dimensional(1-D) pattern structures were fabricated on a hybrid mixture thin film of lanthanum oxide and a UV-curable resin. 1-D pattern on a wafer fabricated by the laser interference lithography was transferred to polydimethylsiloxane and this is used as a mold of UV-NIL process. Conducting an X-ray photoelectron spectroscopy, C 1s and La 3d spectra were analyzed, and it was confirmed that hybrid thin film was successfully deposited on glass substrate. Also, transferred pattern structure was observed by using an atomic force microscopy. Through this, it was revealed that agglomerations between 1-D pattern were increased as UV irradiation time increased and this phenomenon disrupted the quality of NIL process. Additionally, liquid crystal(LC) cells with patterned hybrid thin films were fabricated and LC alignment performances were investigated. Using the polarizing optical microscopy and the crystal rotation method, LC alignment state and pretilt angles were observed. Consequently, the uniform homogeneous LC alignment was achieved at UV irradiation time of 1min and 3min where high resolution pattern transfer was observed.

Recently, we can find that a successful results of solid devices and biochips in the development of nanosclae lithographic technique. Nanoimprint lithography(NIL) is most effective to make nanospatterns because of its merits. Especially ultraviolet-nanoimprint lithography (UV-NIL) is widely used among nanoimprint lithography method because of efficiency in view of cost and time. By using this technique, we get successfully fabricated 100nm wide silicon nanowires on the Silicon on insulator (SOI) wafer. We identify that the nanowire patterns were distinguished by FE-SEM and the characteristic of nanowire conductance were measured by semiconductor parameter analyzer. And we get graphs of electric change that are used for the detection of dopamine. Consequently, these nanopatterned SOI substrates would be able to use as bioplatform for nanoscale biochips. Acknowledgments: This research was supported by National Nuclear R&D Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (No. 2010-0018194) and by the Ministry of Knowledge Economy (MKE) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Strategic Technology. And This research was supported by the Original Technology Research Program for Brain Science through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2009-0093907) References : 1. W. Lee, B. -K. Oh, Y. -W. Kim, and J. -W. Choi ,Journal of Nanoscience and Nanotechnology, 6, 3521(2006) 2. Ho-Gil Choi, Ajay K. Yagati, Ki-Seok Kim, Gun-Young Jung, Sang Baek Lee, Jeong-Woo Choi, and Byung-Keun Oh, J. Nanosci. Nanotechol, 8, 4945-4950(2008)

Recently, a successful outcome of solid device such as high integrated memory, optoelectronic device and biochip is in the development of nanosclae lithographic technique. In other words, nanoscale controlling is key point to improve these devices. Compare with electrical beam lithography, optics lithography, and NIL, Nanoimprint lithography (NIL) is most effective to make nanostructure because of its merits. NIL can provide inexpensive and easier method to generate large area of nanoscale patterns. Especially ultraviolet-nanoimprint lithography (UV-NIL) is extensively used among nanoimprint lithography method because of efficiency in view of cost and time. By using this UV-NIL technique, we have successfully fabricated 100nm wide silicon nanowire patterns on the Silicon on insulator (SOI) wafer. The fabricated nanowire patterns were distinguished by FE-SEM and the characteristic of nanowire conductance were measured by semiconductor parameter analyzer. Consequently, these nanopatterned SOI substrates would be able to use as bioplatform for nanoscale biochips. Acknowledgments: This research was supported by Nuclear R&D program through the Korea Science and Engineering Foundation (KOSEF) funded by the Ministry of Education, Science and Technology (MEST) of Korea (Grant No. M20706010003-08M0601-00310), and by the Ministry of Knowledge Economy (MKE) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Strategic Technology and by The Korea Science and Engineering Foundation (KOSEF) grant funded by the Korean government (MEST) (2006-05374)

Nanoimprint lithography (NIL) is one of the most promising technologies to fabricate nanopattern on solid substrate because of its several advantages such as resolution, reliability, and process speed, compared to conventional lithography. By using NIL, nano-scale to micro-scale nanostructures was fabricated on large scale silicon on insulator (SOI) plate at mild condition. The fabricated nanowire patterns were characterized by FE-SEM. An antibody was immobilized on the fabricated nanowire pattern, which has affinity for target molecule of interest. And then target molecules were detected by analyzing the change of nanowire conductance using semiconductor parameter analyzer. In this study, the proposed NIL technique can be useful as a method for the fabrication of nanoscale biosensor. Acknowledgments: This research was supported by the Core Environmental Technology Development Project for Next Generation funded by the Ministry of Environment of Korea, and by Nuclear R&D program through the Korea Science and Engineering Foundation (KOSEF) funded by the Ministry of Education, Science and Technology (MEST) of Korea (Grant No. M20706010003-08M0601-00310)

본 연구에서는 나노임프린트 리소그래피를 이용하여 500 nm line, 600 nm pore, 1 μm pore, 2.5 μm pore의 마이크로 수준에서 나노 수준에 이르는 다양한 크기와 모양의 nanopore 형태 패턴을 제작하였다. Thermal imprint 방식과 달리 상온, 저압에서 임프린팅이 가능하며 사용되는 스탬프의 수명을 늘리고 보다 미세하고 복잡한 형태의 패턴을 제작할 수 있는 UV-assisted imprint 방식을 사용하였다. E-beam lithography로 패턴을 각인한 quartz소재의 스탬프를 사용하였으며 스탬프의 재질이 투명하여 UV 조사시 UV curable resin이 경화될 수 있도록 하였다. 또한 스탬프의 표면을 (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trichlorosilane의 monolayer 층으로 미리 코팅하여 임프린트 후 스탬프와 기판과의 releasing을 쉽게함과 동시에 패턴의 일부가 스탬프에 묻어 나와 전사된 패턴에 defect가 없도록 하였다. 또한, gold를 미리 증착하여 임프린팅함으로써 lift-off 시에 필요한 bi-layer 층이 필요 없게 되어 산소 플라즈마를 이용한 에칭이 더욱 쉽고 lift-off 공정이 생략될 수 있도록 하였다. 나노임프린트 공정에 있어 가장 큰 문제점은 잔여층의 생성이며 이러한 잔여층을 제거하고자 산소 플라즈마 에칭을 하였다. 에칭공정을 통해 gold의 표면이 완전히 드러났으며 산소 플라즈마를 통해 gold의 표면이 친수성으로 바뀌어 추후 단백질 고정화를 더욱 쉽게 하였다. 그리하여 나노임프린트 기술을 이용해 나노크기의 바이오소자 제작을 가능하게 하였다.

A constant desire has been to fabricate nanopatterns for biochip and the Ultraviolet-nano imprint lithography (UV-NIL) is promising technology especially compared with thermal type in view of cost effectiveness. By using this method, nano-scale to micro-scale structures also called nanopore structures can be fabricated on large scale gold plate at normal conditions such as room temperature or low pressure which is not possible in thermal type lithography. One of the most important methods in fabricating biochips, immobilizing, was processed successfully by using this technology. That means immobilizing proteins only on the nanopore structures based on gold, not on hardened resin by UV is now possible by utilizing this method. So this selective nano-patterning process of protein can be useful method fabricating nanoscale protein chip.

고분자 몰드를 이용한 nanoimprint lithography (NIL)는 고분자소재의 유연성과 투명성으로 인하여, 유기전자소자나 유연한 디스플레이소자 등 다양한 응용이 가능하다. 하지만, 고분자소재는 일반적으로 열저항성과 내구성이 낮아서, 고분자 몰드를 이용한 패턴형성 시, 자외선 경화방식이 주로 사용된다. 만약 복제가 쉽고, 가격이 저렴하며, 열저항성과 내구성이 강한 고분자 몰드를 제작한다면, thermoplastic-NIL 기술에 적용할 수가 있기 때문에, 고온을 요구하는 소자의 패턴형성 공정에 사용 가능하다. 본 연구에서는 이러한 고분자 몰드 제작을 위하여, 열저항성과 내구성이 강한 polyimide 필름과 polyurethane acrylate (PUA)를 기반으로 제작된 resin을 이용하였다. 먼저 Polyimide 필름 위에 자외선 노광을 사용하여, PUA resin 을 경화시킴으로써 패턴을 형성하였다. 이렇게 만들어진 몰드를 thermoplastic-NIL기술에 적용함으로써, Si 기판 위에 sub-마이크로 급 패턴을 형성하였다. 또한, 제작된 고분자 몰드를 사용하여 반복적인 NIL 공정을 수행함으로써 몰드의 내구성을 확인하였으며, 곡면 기판 위에 NIL을 함으로써 몰드의 유연성을 확인 할 수 있었다.

In the paper, residual-layer-free nanoimprint lithography for large-area fabrication is reviewed. In order to remove the residual layer during the imprint process, polymer resists and mold materials should be designed with the aspects of surface chemistry and mold geometries in mind. Various approaches for residual-layer-free nanoimprint lithography are discussed including incomplete filling by polymer mass, reverse imprint methods, self-removal techniques, and the employment of elastomeric mold deformation. In addition, issues that must be overcome to enable large-area roll-to-roll nanoimprinting without a residual layer are presented.

Nanoimprint lithography (NIL) is a next generation technology for fabrication of micrometer and nanometer scale patterns. 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. Up to now there have been a lot of researches on thermal NIL, but most of them have been focused on polymer deformation in the molding process and there are very few studies on the cooling and demolding process. In this paper a cooling process of the polymer resist in thermal NIL is analyzed with finite element method. The modeling of cooling process for mold, polymer resist and substrate is developed. And the cooling process is numerically investigated with the effects of imprinting temperature and residual layer thickness of polymer resist on stress distribution of the polymer resist. The results show that the lower imprinting temperature, the higher the maximum von Mises stress and that the thicker the residual layer, the greater maximum von Mises stress.

Nanoimprint lithography (NIL) is a nanofabrication method known to be a low cost method of fabricating nanoscale patterns as small as 6 m. This study is focused on understanding physical phenomena in the embossing of nano/micro scale structures with 100 nm minimum feature size. We present the effects of capillary force and width of stamp groove on flow behavior at the embossing stage through numerical experimentation. We also compare our numerical results with previous experimental results and discuss our results.

Nanoimprint lithography (NIL) is an emerging technology enabling cost effective and high throughput nanofabrication. To successfully imprint a nanometer scale patterns, the understanding of the mechanism in nanoimprint forming is essential. In this paper, a numerical analysis of polymer flow in thermal NIL was performed. First, a finite element model of the periodic mold structure with prescribed boundary conditions was established. Then, the volume of fluid (VOF) and grid deformation method were utilized to calculate the free surfaces of the polymer flow based on an Eulerian grid system. From the simulation, the velocity fields and the imprinting pressure for constant imprinting velocity in thermal NIL were obtained. The velocity field is significant because it can directly describe the mode of the polymer deformation, which is the key role to determine the mechanism of nanoimprint forming. Effects of different mold shapes and various thicknesses of polymer resist were also investigated.

The replica of highly ordered nano-sphere array patterns were fabricated using hot embossing method. The polymer replica was coated with silcon dioxide layer and self-assembled monolayer. Using UV nanoimprint lithography with the template, highly ordered nano-sphere array patterns were clearly fabricated on curved substrate.

Nano-sized metal patterns were successfully fabricated on flexible PET substrate using nanoimprint lithography. 70nm line and space PMMA resist pattern was formed on PET substrate without residual layer by 'artial filling effect' and 20nm thin Cr metal layer was deposited by e-beam evaporation. Then, PMMA resist was selectively removed by acetone and 70nm narrow Cr pattern was formed.

Nano-sized metal patterns were successfully fabricated on flexible PET substrate using nanoimprint lithography. 70nm line and space PMMA resist pattern was formed on PET substrate without residual layer by "partial filling effect' and 20nm thin Cr metal layer was deposited by e-beam evaporation. Then, PMMA resist was selectively removed by acetone and 70nm narrow Cr pattern was formed.