Search

In this manuscript, we demonstrate the potential of replacing the standard bottom anti-reflective coating (BARC) with a polymethylglutarimide (PMGI) layer for wafer-scale nanofabrication by means of deep-UV displacement talbot lithography (DTL). PMGI is functioning as a developable non-UV sensitive bottom anti-reflective coating (DBARC). After introducing the fabrication process using a standard BARC-based coating and the novel PMGI-based one, the DTL nanopatterning capabilities for both coatings are compared by means of the fabrication of etched nanoholes in a dielectric layer and metal nanodots made by lift-off. Improvement of DTL capabilities are attributed to a reduction of process complexity by avoiding the use of O2 plasma etching of the BARC layer. We show the capacity of this approach to produce nanoholes or nanodots with diameters ranging from 95 to 200 nm at a wafer-scale using only one mask and a proper exposing dose. The minimum diameter of the nanoholes is reduced from 118 to 95 nm when using the PMGI-based coating instead of the BARC-based one. The possibilities opened by the PMGI-based coating are illustrated by the successful fabrication of an array of nanoholes with sub-100 nm diameter for GaAs nanowire growth on a 2″ GaAs wafer, a 2″ nanoimprint lithography (NIL) master stamp, and an array of Au nanodots made by lift-off on a 4″ silica wafer. Therefore, DTL possess the potential for wafer-scale manufacturing of nano-engineered materials.

International audience; Single-digit nanometer patterning by nanoimprint lithography is a challenging task, which requires optimum stamp fabrication technique. In the current work, we present different strategies for technology of hard master stamps to make intermediate working stamps with sub-10 nm features. Methods of both negative and positive master stamps fabrication, based on EBL, RIE and ALD are described and compared. A single-step copying of negative master stamps using a polymer material is a preferred strategy to reach the ultra high-resolution. Lines as small as 5.6 nm are demonstrated in a resist using a combined thermal and UV-imprint with OrmoStamp material as a working stamp.

Devices based on molecular motor-driven cytoskeletal filaments, e.g., actin filaments, have been developed both for biosensing and biocomputational applications. Commonly, these devices require nanoscaled tracks for guidance of the actin filaments which has limited the patterning technique to electron beam lithography. Thus, large scale systems become intractable to fabricate at a high throughput within a reasonable time-frame. We have studied the possibility to fabricate molecular motor-based devices using the high throughput, high resolution technique of nanoimprint lithography. Molecular motor-based devices require wide open regions (loading zones) to allow filaments to land for later propulsion into the nanoscale tracks. Such open zones are challenging to fabricate using nanoimprint lithography due to the large amount of material displaced in the process. We found that this challenge can be overcome by introducing nanoscaled pillars inside the loading zones, into which material can be displaced during imprint. By optimising the resist thickness, we were able to decrease the amount of material displaced without suffering from insufficient filling of the stamp. Furthermore, simulations suggest that the shape and positioning of the pillars can be used to tailor the overall cytoskeletal filament transportation direction and behaviour. This is a potentially promising design feature for future applications that however, requires further optimisations before experimental realisation.

Position controlled nanowire growth is important for nanowire-based optoelectronic components which rely on light emission or light absorption. For solar energy harvesting applications, dense arrays of nanowires are needed; however, a major obstacle to obtaining dense nanowire arrays is seed particle displacement and coalescing during the annealing stage prior to nanowire growth. Here, we explore three different strategies to improve pattern preservation of large-area catalyst particle arrays defined by nanoimprint lithography for nanowire growth. First, we see that heat treating the growth substrate prior to nanoimprint lithography improves pattern preservation. Second, we explore the possibility of improving pattern preservation by fixing the seed particles in place prior to annealing by modifying the growth procedure. And third, we show that a SiNx growth mask can fully prevent seed particle displacement. We show how these strategies allow us to greatly improve the pattern fidelity of grown InP nanowire arrays with dimensions suitable for solar cell applications, ultimately achieving 100% pattern preservation over the sampled area. The generic nature of these strategies is supported through the synthesis of GaAs and GaP nanowires. [Figure not available: see fulltext.] (Less)

We report on the realization of a novel interdigitated cantilever array with electrostatic control of the shape of the interdigitated array. It consists of an array of SiO2/metal double-finger cantilevers in a grating configuration together with an electrical connection part. The complete grating structure is fabricated with nanoimprint lithography, UV lithography and reactive ion etching. The patterns of the cantilever arrays are defined by nanoimprint lithography. The electrical contact pads are defined and aligned with the imprinted grating pattern by UV lithography. The two steps of reactive ion etching are optimized to get vertical sidewalls of the SiO2 cantilevers and finally to release them from the Si substrate. By applying a bias, the shape of the cantilever array can be altered due to the electrostatic force. The dimensions of the cantilevers and the spacing between them are optimized to achieve the desired functional operating characteristics of the structures. Since the fabrication scheme is based on nanoimprint lithography, such electrostatically controlled periodic structures may be relatively easily and non-expensively realized in various configurations, allowing them to function as optical switching elements, electrical filters, mass sensors, etc.

We report a novel a lift-off method for nanoimprint lithography. This is a bi-layer method, using a polymethyl methacrylate (PMMA) on lift-off layer (LOL) resist scheme. For the imprint step, direct evidence for good pattern transfer down to 20 nm is shown. Oxygen plasma ashing is required to remove residual PMMA. A liquid solvent, MF 319, is used to transfer the pattern down to the silicon. The LOL is dissolved isotropically while the PMMA is unaffected. Ashing time can kept to a minimum through the wet etch method. This reduces the line widening effect. After metal evaporation a two-step lift-off process prevents metal flakes from adhering to the surface electrostatically. At first warm acetone breakes apart the metal layer and dissolves the PMMA, then warm Remover S-1165 removes the LOL and remaining metal. Structures of lines down to 50 mn and dots with a diameter of sub 20 nm are presented.

We present processing technology based on nanoimprint lithography (NIL) and wet etching for fabrication of GaInAs/InP three-terminal ballistic junction (TBJ) devices. To transfer sub-100 nm features into a high-mobility InP-based 2DEG material, we used SiO2/Si stamps made with electron beam lithography and reactive ion etching. After the NIL, the resist residues are removed in oxygen plasma followed by wet etching of GaInAs/InP to define the TBJ-structures. Fabricated TBJ-devices are characterized using scanning electron microscopy and electron transport measurements. Highly non-linear electrical characteristics of the TBJ structures are demonstrated and compared with E-beam defined devices.

Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved. (Less)

The smaller the features on the stamp the more important are the interactions between stamp and polymer layer. A stamp rich in small structures will effectively show a surface area enlargement, which generally leads to adhesion of the polymer to the stamp. This makes a subsequent imprint impossible without troublesome and time-consuming cleaning. The anti-adhesion properties of Si- or SiO2-based stamps can be improved by binding fluorinated silanes covalently to the surface. In this paper, we demonstrate that the deposition procedure as well as the environment during deposition are important with respect to the quality and performance of the molecular layer. (C) 2002 Published by Elsevier Science B.V.

Semiconductor nanowires are great candidates for building novel electronic devices. Considering the cost of fabricating such devices, substrate reuse and gold consumption are the main concerns. Here we report on implementation of high throughput gold electrodeposition for selective deposition of metal seed particles in arrays defined by lithography for nanowire synthesis. By use of this method, a reduction in gold consumption by a factor of at least 300 was achieved, as compared to conventional thermal evaporation for the same pattern. Because this method also facilitates substrate reuse, a significantly reduced cost of the final device is expected. We investigate the morphology, crystallography, and optical properties of InP and GaAs nanowires grown from electrodeposited gold seed particles and compare them with the properties of nanowires grown from seed particles defined by thermal evaporation of gold. We find that nanowire synthesis, as well as the material properties of the grown nanowires are comparable and quite independent of the gold deposition technique. On the basis of these results, electrodeposition is proposed as a key technology for large-scale fabrication of nanowire-based devices.

A complete nanobiosensor structure consisting of a 200 @mm x 200 @mm area containing 100 nm sized interdigitated nanoelectrodes with varied interelectrode distances has been fabricated using nanoimprint lithography (NIL) in combination with UV-lithography. The complete structure has been characterized with admittance spectroscopy. In the paper are discussed the needs and key issues for nanosensors and the capability offered by using NIL for fabrication of such sensors.

The unit of y axis in Fig. 2 in the original version of this article was unfortunately wrongly written on page 2856, instead of m−2. (Figure Presented.).

Stamp fabrication for nanoimprinting can be significantly simplified, when specialized crosslinking polymers are applied to pattern definition. The polymer patterns can be used as stamps themselves. Two possibilities are reported: (1) An e-beam sensitive resist was developed, which enables the fabrication of polymer-on-silicon stamps. Patterns with a feature size of 70 nm could be created. (2) Full plastic stamps were obtained by a casting-moulding technique, which enable pattern transfer from any conventional mould. The quality of the two stamp variants were proved by imprinting experiments.

Nanoimprint lithography over 2 inch wafers with a patterned area of 40,000 micrometer squared consisting of interdigitated lines of 100 nm width with varying distance between the lines has been performed. By performing metal lift-off and subsequent UV-lithography for definition of contact regions and pads, complete metal arrays have been fabricated. The structure is electrically characterized by admittance spectroscopy. In this paper we describe the design and realization of a compact nanoimprint lithography system. Furthermore, various aspects of nanoimprint lithography are discussed, and nanoimprint lithography is compared with other nanostructuring technologies.

In this study we will report on the development of a process to establish antisticking layers on nickel-based stamps, which are used in several industrial applications of nanoimprint lithography or related methods. The fluorinated alkyl silane films have been deposited onto different Ni-based stamp surfaces in order to minimize the adhesion tendency at the stamp/polymer interface. Film thickness, chemical composition, purity, and binding mechanisms of the silane groups to different stamp surface materials have been determined by photoelectron spectroscopy (XPS). In the case of electroplated nickel stamps—where low imprint qualities are observed—multilayer thick films cover the stamp surfaces, consisting of polymerized, cross-linked alkyl silanes, which are poorly bound to the surface. In order to overcome these restrictions a 100 A thick polycrystalline titanium layer has been established in a sandwich position between the nickel substrate and the silane film. Here, silane film thicknesses in the monomolecular region together with evidences for strong covalent linkage between the silane groups and the oxidized Ti surface can be concluded from the XPS results, leading to film properties and imprint qualities, which are comparable to those formerly observed for silicon stamps.