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In the field of micro- and nanotechnology, most lithography and fabrication tools coming from the microelectronic industry are expensive, time-consuming and may need some masks that have to be subcontracted. Such approach is not suitable for other fields that require rapid prototyping such as chemistry, life science or energy and may hinder research creativity. In this work, we present two table-top equipments dedicated to the fabrication of deterministic colloidal particles assemblies onto micro-structured substrates. We show that, with a limited modification of the optics of a standard videoprojector, it is possible to quickly obtain substrates with thousands of micrometric features. Then, we combine these substrates with thermodynamic colloidal assembly and generate arrays of particles without defects. This work opens the way to a simple and table-top fabrication of devices based on colloidal particles. [ABSTRACT FROM AUTHOR]

Abstract: We report on the fabrication and characterization of photonic band-gaps structures by nanoimprint lithography in a dye-doped polymer. Photonic band calculations show that photonic crystal slabs composed of a triangular array of polymer pillars could exhibit photonic band-gaps for the magnetic-like modes. The resulting structures show that the nanoimprint lithography process is well-suited to fabricate in a single-step process, these challenging photonic structures opening perspectives to realize integrated photonic band-gap circuits. [Copyright &y& Elsevier]

Abstract: In nanoimprint lithography, the most common approach to prevent resist to adhere to the mold is to graft a fluorinated anti-sticking layer on the mold’s surface. But it is known that these layers suffer from degradation after a certain number of imprints. In this work, we study the influence of the presence, type and quantity of fluorinated surfactant additives in the resist formulation on the degradation of the mold’s treatment. It is found that the presence of a fluorinated surfactant drastically increases the possible maximal number of imprints before retreatment. Also, we observed that fluorinated surfactants with a silane end-group are able to be adsorbed at the surface of the mold after repeated imprints to progressively replace the initial mold’s treatment. Nevertheless, a balance has still to be found between quantity, reactivity and type of surfactant to maintain a smooth and extremely thin fluorinated layer at the surface of the mold. [Copyright &y& Elsevier]

In this work, the authors evaluate a new type of perfluoropolyether molecule (FLUOROLINK® S10) to be used as an antisticking mold treatment in UV nanoimprint lithography. Unlike currently used ones, this molecule has two anchoring ends groups allowing two covalent grafting sites of the molecule to the mold surface. Obtained results on this molecule are compared to Optool DSX’s ones. Using contact angle measurement, x-ray photoelectron spectroscopy, and electron spin resonance, the authors carried out chemical analysis of the evolution of antisticking treatments as a function of the number of imprints. It is found that both molecules have a roughly equivalent behavior. FLUOROLINK® S10 has shown less chemical resistance, attributed to its larger number of C–O bonds in the molecule, but an improved mechanical resistance, attributed to the double grafting mechanism. [ABSTRACT FROM AUTHOR]

In this article, the authors compare a polymer resist to a thermally curable monomer resist in a full 8 in. wafer thermal nanoimprint lithography process. Using exactly the same imprinting conditions, the authors compare the printing quality and investigate the resist distribution through large area gratings (6×6 mm2) with various densities. It is shown that a liquid monomer solution greatly enhance the printing uniformity because of a much wider resist redistribution and flow during the process. Redistribution of the monomer resist is observed over an entire grating, while it is observed only over a few periods of a grating for the polymer in the same conditions. Furthermore, a low molecular weight resist allows reducing the imprinting force as well as the total cycle time. [ABSTRACT FROM AUTHOR]

This article reports on the properties of ultraviolet nanoimprint lithography dedicated imprinting materials. Studied solutions are composed of a diacrylate-based monomer and a variable amount (1%, 2%, and 4% in weight) of three different photoinitiators from Ciba Specialty Chemicals (Irgacure 819, Irgacure OXE02, and Irgacure 379). Photopolymerization kinetic studies were conducted on these solutions. Quantity and type of photoinitiator could be optimized in order to obtain a polymerization rate higher than 95% with an exposure dose as low as 20 mJ/cm2. The etch resistance of this home-developed imprinting resist was characterized under standard plasma etching conditions. We observed that the polymerization rate has a large influence on the plasma etch resistance, and we show that the etch rates of our best material is comparable to the one measured for 193 nm photolithography resists and makes it a very good candidate as a masking layer for direct pattern transfer. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a new resist material, named NILTM105, for the purpose of ultraviolet curing nanoimprint lithography. Its capability for micro- and nano-scale features patterning has been experimentally analyzed and compared to two other commercially available UV-NIL resists (AMONIL-MMS4 proposed by AMO GmbH, Germany and PAK-01 from Toyo Gosei, Japan). Using 3D-atomic force microscopy, cross section scanning electron microscopy, CD-SEM and ellipsometric measurements, the suitability of this resist for a reliable replication of the mold features was confirmed. Besides, detailed study of the residual thickness and features height variation as a function of pattern size and density has proven that the three investigated resists can flow over distances on the millimeter range. Finally, the etch resistance of the home-developed material was characterized under several plasmas conditions. It was found out that the etch rates values are compatible with the use of this resist as a masking layer during transfer steps. [Copyright &y& Elsevier]

The fabrication of a three-dimensional multilayered nanostructure is demonstrated with a newly developed nanofabrication technique, namely, reverse contact ultraviolet nanoimprint lithography. This technique is a combination of reverse nanoimprint lithography and contact ultraviolet lithography. In this process, a UV cross-linkable polymer and a thermoplastic polymer are spin coated onto a patterned hybrid metal-quartz stamp. These thin polymer films are then transferred from the stamp to the substrate by contact at a suitable temperature and pressure. The whole assembly is then exposed to UV light. After separation of the stamp and the substrate, the unexposed polymer areas are rinsed away with acetone leaving behind the negative features of the original stamp with no residual layer. [ABSTRACT FROM AUTHOR]

In general, fluorinated antisticking layers (F-ASL) are deposited on the imprint stamps to ease their separation from the imprinted resist in UV nanoimprint lithography. However, these layers are found to degrade with repeated imprint operations. A drastic decrease in fluorinated species is observed on the mold surface. Yet, there is still a debate on the nature of the exact mechanisms involved in this degradation. In this paper, electron spin resonance (ESR) is used to investigate the chemical reaction occurring between the fluorinated molecules and the UV curable resist. Free radicals of the resist, generated under UV illumination, have been observed by ESR. The decrease in their corresponding signal in the presence of fluorinated ASL species shows evidence of the chemical reactivity of the resist toward the F-ASL. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of two-dimensional polymer photonic crystal band-edge lasers operating in the visible range. The components have been fabricated in a dye chromophore-loaded polymer matrix by nanoimprint lithography. High-symmetry band-edge modes are used to generate laser emission. The experimental lasing frequencies are in good agreement with those calculated using a two-dimensional plane wave algorithm. These results demonstrate the potential of nanoimprint lithography for the fabrication of two-dimensional planar photonic crystal structures in an active medium in a one-step process. [ABSTRACT FROM AUTHOR]

In this work, the authors evaluate the impact of chemical and mechanical properties of UV nanoimprint lithography resists on the durability of antisticking treatments applied on the quartz mold surface. To do this, three acrylate-based resists were formulated and characterized. Fourier transform infrared spectroscopy was used to investigate the degree of conversion of each formulation as a function of the exposure dose and electron spin resonance was used to investigate the chemical reactivity of each formulation with respect to a fluorinated antisticking layer (Optool DSX from Daikin Chemicals). The impact of resist mechanical properties on the mold surface treatment degradation was also studied. Elastic modulus and hardness were measured by nanoindentation as a function of the polymerization degree. Then, these resists were imprinted with a dummy quartz template treated beforehand with the antisticking layer. The release properties of the molds were monitored by measuring their free surface energy as a function of the chemical and mechanical properties of the imprinted resists. A detailed comparative study has shown that release properties degradation is more governed by a mechanical than by a chemical interaction. [ABSTRACT FROM AUTHOR]

Abstract: In this work, atomic force microscopy (AFM) investigations of lamellar PS-b-PMMA block copolymer layers are performed during the self-assembly process. These in-situ experiments are made on both un-patterned planar substrates and topographical substrates (graphoepitaxy experiments) at different temperatures and for different durations. Image processing software is used to produce AFM movies of the same location on the sample and to measure polymer micro-phase domain lengths versus annealing time. We observed that micro-domain formation starts after only a few minutes of heating. On planar substrates, the micro-domain length evolution with time (t) is in accordance with the literature, following a power law~ t 0.29. On the other hand, in substrate channels and in conditions used, we show that the domain length dependence follows a two-step process. Initially, the system adopts a similar kinetic dependence as that of the planar substrate, but at longer times, drastically reduced time dependence is observed due to the topographical confinement of the domains. [Copyright &y& Elsevier]

Abstract: In this paper, we present results on the fabrication of porous alumina membranes on silicon substrates with a long-range order induced by nanoimprint lithography. Fabricated porous alumina matrices present a perfect triangular array of vertical cylindrical pores on areas of 500×500μm2 corresponding to the imprinted surfaces. Also, we demonstrate that it is possible to have a directed density multiplication during the pore formation, compared to the nanoimprint mold, by the initial indentation of only one third of the expected alumina pores. The gold catalyst, needed for nanowires growth, is deposited at the bottom of each pore by electrochemistry. The proposed process is scalable to wafer-scale areas, compatible with microelectronics fabrication standards and is not limited to non-fragile substrates like direct bulk aluminum nanoindentation. [Copyright &y& Elsevier]

Abstract: In this paper, we have been using polymer and thermally curable monomer resists in a full 8in. wafer thermal nanoimprint lithography process. Using exactly the same imprinting conditions, we observed that a monomer solution provides a much larger resist redistribution than a polymer resist. Imprinting Fresnel zone plates, composed of micro- and nano-meter features, was possible only with the monomer resist. In order to reduce the shrinkage ratio of the monomer resists, acrylate–silsesquioxane materials were synthesised. With a simple diffusion-like model, we could extract a mean free path of 1.1mm for the monomer resist, while a polymer flows only on distances below 10μm in the same conditions. [Copyright &y& Elsevier]

Abstract: Fluorinated anti-sticking layers (F-ASLs) are generally used to prevent adhesion between molds and resists in nanoimprint lithography (NIL). Nevertheless, these layers are degraded after a certain number of imprints and the mold needs to be cleaned and re-treated. We have observed that the cleaning procedures before re-treatment impacts on the grafting of the fluorinated molecules and on the longevity of the ASL. We propose an efficient cleaning procedure of the damaged anti-sticking layers on both silicon and fused silica molds allowing a reproducible re-deposition. Surface chemistry analyses were conducted using a specific procedure based on X-ray photoelectron spectroscopy (XPS) experiments. This procedure was proven to be suitable for ultra thin organic layer composition analysis. [Copyright &y& Elsevier]

Abstract: In this work, a novel nanofabrication technique is presented, namely “Reverse contact Ultraviolet Nanoimprint Lithography” (RUVNIL). It is based on reverse nanoimprint lithography and ultraviolet contact lithography. It provides flexibility in building complex three-dimensional structures allowing selective imprint over pre-patterned surfaces with or without residual layer in opposition to what is often encountered in the normal NIL process. We have investigated and optimized the imprinting parameters that are required for three-dimensional nanofabrication and applied it to the fabrication of nano-fluidic channels. This lithography technique is a very promising process for three-dimensional nanofabrication. [Copyright &y& Elsevier]