Fabrication of flexible UV nanoimprint mold with fluorinated polymer-coated PET film
© Shin et al; licensee Springer. 2011
Received: 14 April 2011
Accepted: 18 July 2011
Published: 18 July 2011
UV curing nanoimprint lithography is one of the most promising techniques for the fabrication of micro- to nano-sized patterns on various substrates with high throughput and a low production cost. The UV nanoimprint process requires a transparent template with micro- to nano-sized surface protrusions, having a low surface energy and good flexibility. Therefore, the development of low-cost, transparent, and flexible templates is essential. In this study, a flexible polyethylene terephthalate (PET) film coated with a fluorinated polymer material was used as an imprinting mold. Micro- and nano-sized surface protrusion patterns were formed on the fluorinated polymer layer by the hot embossing process from a Si master template. Then, the replicated pattern of the fluorinated polymer, coated on the flexible PET film, was used as a template for the UV nanoimprint process without any anti-stiction coating process. In this way, the micro- to nano-sized patterns of the original master Si template were replicated on various substrates, including a flat Si substrate and curved acryl substrate, with high fidelity using UV nanoimprint lithography.
In order to form micro- to nano-sized patterns, various lithographic technologies have been used, such as DUV photolithography , e-beam lithography [2, 3], X-ray lithography [4, 5], laser holographic lithography , nanosphere lithography , scanning probe microscopy lithography , and so on. Except for DUV photolithography, these conventional lithography technologies require either a complicated patterning system with a high process cost or offer limited throughput and, thus, are not suitable for mass production. None of these technologies allow micro- to nano-sized patterns to be formed on a non-flat surface. Recently, nanoimprint lithography [9–11] has emerged as one of the most effective technologies to fabricate micro- to nano-sized patterns. Due to its low process cost and high throughput, nanoimprint technology can be used for the mass production of nano-sized patterns [12, 13].
UV nanoimprint templates need to have high stiffness in order for the nano-sized protrusion patterns to be transferred to the substrate and sufficient flexibility for conformal contact to be achieved over a large-sized substrate. Flexible templates can be applied to non-planar substrates. In addition, high transparency to UV is required for the template to be used for UV nanoimprint lithography. A sufficiently low surface energy is also necessary to avoid the need for an anti-sticking coating on the template, which would require the extra deposition of a Si oxide layer [14, 15],
In this study, a fluorinated polymer layer was coated on a flexible polyethylene terephthalate (PET) film, since micro- to nano-sized patterns can easily be formed on a fluorinated polymer layer by the hot embossing process [16, 17], and fluorinated polymers have a very low surface energy [18, 19]. With this fluorinated polymer-coated flexible PET mold, micro- to nano-sized patterns were fabricated on a flat Si substrate and curved acryl substrate with high fidelity using UV nanoimprint lithography.
Fabrication of flexible UV nanoimprint mold
Imprinting process using replicated flexible UV nanoimprint mold
Results and discussion
The micro- and nano-sized surface protrusion patterns of the master template were transferred with high fidelity to the flexible PET film, coated with the fluorinated polymer material, by the hot embossing process.
Since the surface energy of fluorinated polymers is as high as 105° for DI water, a flexible PET film with a patterned fluorinated polymer can be used as a stamp for the UV nanoimprint process without the need for an anti-stiction coating.
Due to the uniform pressing of the flexible PET film mold over either the flat Si wafer or curved acryl substrate, the micro- and nano-sized patterns of the embossed PET film were successfully imprinted onto the substrates using the UV nanoimprint process.
1This work was supported by the Nano Research and Development program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology (2010-0019152) and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2011- 0004819).
- Mimura Y, Ohkubo T, Takeuchi T, Sekikawa K: Deep-UV photolithography. Jpn J Appl Phys 1978, 17: 541–550. 10.1143/JJAP.17.541View Article
- Kise K, Watanabe H, Itoga K, Sumitani H, Amemiya M: Improvement of resolution in X-ray lithography by reducing secondary electron blur. J Vac Sci & Technol B 2004, 22: 126–130. 10.1116/1.1635847View Article
- Liu K, Avouris P, Bucchignano J, Martel R, Sun S: Simple fabrication scheme for sub-10 nm electrode gaps using electron-beam lithography. Appl Phys Lett 2002, 80: 865–867. 10.1063/1.1436275View Article
- Murray A, Scheinfen M, Isaacson M, Adesida I: Radiolysis and resolution Limits of inorganic halide resists. J Vac Sci & Technol B 1985, 3: 367–372.View Article
- Feiertag G, Ehrfeld W, Freimuth H, Kolle H, Lehr H, Schmidt M, Sigalas MM, Soukoulis CM, Kiriakidis G, Pedersen T, Kuhl J, Koenig W: Fabrication of photonic crystals by deep X-ray lithography. Appl Phys Lett 1997, 71: 1441–1443. 10.1063/1.120431View Article
- Campbell M, Sharp DN, Harrison MT, Denning RG, Turberfield AJ: Fabrication of photonic crystals for the visible spectrum by holographic lithography. Nature 2000, 404: 53–56. 10.1038/35003523View Article
- Su YK, Chen JJ, Lin CL, Chen SM, Li WL, Kao CC: GaN-based light-emitting diodes grown on photonic crystal-patterned sapphire substrates by nanosphere lithography. Jpn J Appl Phys 2008, 47: 6706–6708. 10.1143/JJAP.47.6706View Article
- Ogino T, Nishimura S, Shirakashi J: Scratch nanolithography on Si surface using scanning probe microscopy: influence of scanning parameters on groove size. Jpn J Appl Phys 2008, 47: 712–714. 10.1143/JJAP.47.712View Article
- Chou SY, Krauss PR, Renstrom PJ: Imprint of sub-25 nm vias and trenches in polymers. Appl Phys Lett 1995, 67: 3114–3116. 10.1063/1.114851View Article
- Chou SY, Krauss PR, Zhang W, Guo L, Zhang L: Imprint lithography with 25-nanometer resolution. J Vac Sci Technol B 1997, 15: 2897–2904. 10.1116/1.589752View Article
- Lee H, Jung KY: UV curing nanoimprint lithography for uniform layers and minimized residual layers. Jpn J Appl Phys 2004, 43: 8369–8373. 10.1143/JJAP.43.8369View Article
- Colburn M, Johnson S, Stewart M, Damle S, Vailey T, Choi B, Wedlake M, Michaelson T, Sreenivasan SV, Ekerdt J, Willson CG: Step and flash imprint lithography: a new approach to high-resolution patterning. Proc SPIE 1999, 3676: 379.View Article
- Chou SY, Krauss PR, Renstrom PJ: Imprint lithography with 25-nanometer resolution. Science 1996, 272: 85–87. 10.1126/science.272.5258.85View Article
- Kawaguchi Y, Nonaka F, Sanada Y: Fluorinated materials for UV nanoimprint lithography. Microelectron Eng 2007, 84: 973–976. 10.1016/j.mee.2007.01.135View Article
- Tsunozaki K, Kawaguchi Y: Preparation methods and characteristics of fluorinated polymers for mold replication. Microelectron Eng 2009, 86: 694–696. 10.1016/j.mee.2008.11.002View Article
- Becker H, Heim U: Hot embossing as a method for the fabrication of polymer high aspect ratio structures. Sensor Actuat A-Phys 2000, 83: 130–135. 10.1016/S0924-4247(00)00296-XView Article
- Heckele M, Bacher W, Muller KD: Hot embossing - the molding technique for plastic microstructures. Microsyst Technol 1998, 4: 122–124. 10.1007/s005420050112View Article
- Hirai Y, Yoshida S, Okamoto A, Tanaka Y, Endo M, Irie S, Nakagawa H, Sasago M: Mold surface treatment for imprint lithography. J Photopolym Sci Technol 2001, 14: 457–462. 10.2494/photopolymer.14.457View Article
- Bailey T, Choi BJ, Colbum M, Meissl M, Shaya S, Ekerdt JG, Sreenivasan SV, Willson CG: Step and flash imprint lithography: Template surface treatment and defect analysis. J Vac Sci Technol B 2000, 18: 3572–3577. 10.1116/1.1324618View Article
- Hong SH, Han KS, Byeon KJ, Lee H, Choi KW: Fabrication of sub-100 nm sized patterns on curved acryl substrate using a flexible stamp. Jpn J Appl Phys 2008, 47: 3699–3701. 10.1143/JJAP.47.3699View Article
- Hong SH, Bae BJ, Han KS, Hong EJ, Lee H, Choi KW: Imprinted moth-eye antireflection patterns on glass substrate. Electron Mater Lett 2009, 5: 39–42. 10.3365/eml.2009.03.039View Article
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.