Wurenlingen, Switzerland
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Dais C.,Eulitha Inc. | Clube F.,Eulitha Inc. | Wang L.,Eulitha Inc. | Solak H.H.,Eulitha Inc.
Microelectronic Engineering | Year: 2017

Quasi-periodic structures with a high degree of rotational symmetry are desired for photonic applications because of their nearly isotropic optical response, in contrast to the highly directional behavior of periodic lattices. Here we introduce a method based on the superposition of periodic structures obtained by multiple exposure of a photomask with Displacement Talbot Lithography in which the photomask is rotated by a certain angle between exposures. The resulting structure can be considered as a Moiré pattern. High-quality patterns with 10 and 12-fold rotation symmetries and resolutions in the sub-micron to micron range are uniformly and reproducibly printed. The technique is suitable for the mass fabrication of wafer-scale quasi-periodic photonic patterns. © 2017 Elsevier B.V.


Mojarad N.,Paul Scherrer Institute | Mojarad N.,ETH Zurich | Hojeij M.,Paul Scherrer Institute | Hojeij M.,Hoffmann-La Roche | And 4 more authors.
Nanoscale | Year: 2015

All nanofabrication methods come with an intrinsic resolution limit, set by their governing physical principles and instrumentation. In the case of extreme ultraviolet (EUV) lithography at 13.5 nm wavelength, this limit is set by light diffraction and is ≈3.5 nm. In the semiconductor industry, the feasibility of reaching this limit is not only a key factor for the current developments in lithography technologies, but also is an important factor in deciding whether photon-based lithography will be used for future high-volume manufacturing. Using EUV-interference lithography we show patterning with 7 nm resolution in making dense periodic line-space structures with 14 nm periodicity. Achieving such a cutting-edge resolution has been possible by integrating a high-quality synchrotron beam, precise nanofabrication of masks, very stable exposures instrumentation, and utilizing effective photoresists. We have carried out exposure on silicon- and hafnium-based photoresists and we demonstrated the extraordinary capability of the latter resist to be used as a hard mask for pattern transfer into Si. Our results confirm the capability of EUV lithography in the reproducible fabrication of dense patterns with single-digit resolution. Moreover, it shows the capability of interference lithography, using transmission gratings, in evaluating the resolution limits of photoresists. This journal is © The Royal Society of Chemistry.


Wang L.,Paul Scherrer Institute | Solak H.H.,Eulitha Inc. | Ekinci Y.,Paul Scherrer Institute | Ekinci Y.,ETH Zurich
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Metallic wire-grid polarizers (WGP) transmit TM-polarized light (transverse magnetic) and reflect TE polarization (transverse electric) efficiently. They are compact, planar and compatible with integrated circuit (IC) fabrication, which simplifies their use as optical components in nanophotonic, fiber optic, display, and detector devices. In this work, Al bi-layer WGPs were designed and numerically simulated using finite element methods. Optical properties of the polarizers were analyzed in the deep-ultraviolet (DUV) to infrared (IR) regions. It was observed that Al bi-layer WGPs show broadband and high TM transmission and extinction ratio. A comparison of the performances of single and bi-layer WGPs show that the latter is highly advantageous over the former one. An extensive study of the dependence of the optical properties of single and bi-layer WGPs on structural parameters, such as period, metal thickness, and, duty cycle (DC), is provided. Optimal structural parameters are obtained within the feasible parameters in terms of nanofabrication. An Al bi-layer polarizer with a period of 80 nm and a metal layer thickness of 40 nm showed transmission up to 80% and extinction of 40 dB (10 4) and broadband polarizing behavior down to a wavelength of 250 nm. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Wang L.,Paul Scherrer Institute | Solak H.H.,Eulitha Inc. | Ekinci Y.,Paul Scherrer Institute | Ekinci Y.,ETH Zurich
Nanotechnology | Year: 2012

Limited beam spot size is a major limitation of interference lithography. This limits the area of patterning and reduces the pattern homogeneity. We describe a scanning exposure technique to circumvent this problem. We show the generation of uniform and seamless gratings with half-pitches down to 35nm over an area of several mm 2 using EUV interference lithography. The presented technique offers a fast and cost-effective method of fabricating one-and two-dimensional periodic nanostructures with improved uniformity and increased patterning area. © 2012 IOP Publishing Ltd.


Siegfried T.,Paul Scherrer Institute | Ekinci Y.,Paul Scherrer Institute | Ekinci Y.,ETH Zurich | Solak H.H.,Eulitha Inc. | And 2 more authors.
Applied Physics Letters | Year: 2011

We report a high-throughput method for the fabrication of metallic nanogap arrays with high-accuracy over large areas. This method, based on shadow evaporation and interference lithography, achieves sub-10 nm gap sizes with a high accuracy of ±1.5 nm. Controlled fabrication is demonstrated over mm 2 areas and for periods of 250 nm. Experiments complemented with numerical simulations indicate that the formation of nanogaps is a robust, self-limiting process that can be applied to wafer-scale substrates. Surface-enhanced Raman scattering (SERS) experiments illustrate the potential for plasmonic sensing with an exceptionally low standard-deviation of the SERS signal below 3 and average enhancement factors exceeding 1 × 10 6. © 2011 American Institute of Physics.


Siegfried T.,Paul Scherrer Institute | Wang L.,Eulitha Inc. | Ekinci Y.,Paul Scherrer Institute | Martin O.J.F.,Ecole Polytechnique Federale de Lausanne | Sigg H.,Paul Scherrer Institute
ACS Nano | Year: 2014

Double-layer plasmonic nanostructures are fabricated by depositing metal at normal incidence onto various resist masks, forming an antenna layer on top of the resist post and a hole layer on the substrate. Antenna plasmon resonances are found to couple to the hole layer, inducing image charges which enhance the near-field for small layer spacings. For continued evaporation above the resist height, a sub-10 nm gap channel develops due to a self-aligned process and a minimal undercut of the resist sidewall. For such double layers with nanogap channels, the average surface-enhanced Raman scattering intensity is improved by a factor in excess of 60 in comparison to a single-layer antenna with the same dimensions. The proposed design principle is compatible with low-cost fabrication, straightforward to implement, and applicable over large areas. Moreover, it can be applied for any particular antenna shape to improve the signals in surface-enhanced spectroscopy applications. © 2014 American Chemical Society.


Solak H.H.,Eulitha Inc. | Dais C.,Eulitha Inc. | Clube F.,Eulitha Inc.
Optics Express | Year: 2011

Periodic micro and nano-structures can be lithographically produced using the Talbot effect. However, the limited depth-of-field of the self-images has effectively prevented its practical use, especially for high-resolution structures with periods less than 1 micrometer. In this article we show that by integrating the diffraction field transmitted by a grating mask over a distance of one Talbot period, one can obtain an effective image that is independent of the absolute distance from the mask. In this way high resolution periodic patterns can be printed without the depth-of-field limitation of Talbot self-images. For one-dimensional patterns the image obtained is shown to be related to the convolution of the mask transmission function with itself. This technique, which we call Displacement Talbot Lithography (DTL), enables high-resolution photolithography without the need for complex and expensive projection optics for the production of periodic structures like diffraction gratings or photonic crystals. Experimental results showing the printing of linear gratings and an array of holes on a hexagonal lattice are presented. © 2011 Optical Society of America.


Sarkar S.S.,Paul Scherrer Institute | Sarkar S.S.,Intel Corporation | Solak H.H.,Paul Scherrer Institute | Solak H.H.,Eulitha Inc. | And 2 more authors.
Optics Express | Year: 2014

Fresnel zone plates (FZPs) play an essential role in high spatial resolution x-ray imaging and analysis of materials in many fields. These diffractive lenses are commonly made by serial writing techniques such as electron beam or focused ion beam lithography. Here we show that pinhole diffraction holography has potential to generate FZP patterns that are free from aberrations and imperfections that may be present in alternative fabrication techniques. In this presented method, FZPs are fabricated by recording interference pattern of a spherical wave generated by diffraction through a pinhole, illuminated with coherent plane wave at extreme ultraviolet (EUV) wavelength. Fundamental and practical issues involved in formation and recording of the interference pattern are considered. It is found that resolution of the produced FZP is directly related to the diameter of the pinhole used and the pinhole size cannot be made arbitrarily small as the transmission of EUV or x-ray light through small pinholes diminishes due to poor refractive index contrast found between materials in these spectral ranges. We also find that the practical restrictions on exposure time due to the light intensity available from current sources directly imposes a limit on the number of zones that can be printed with this method. Therefore a trade-off between the resolution and the FZP diameter exists. Overall, we find that this method can be used to fabricate aberration free FZPs down to a resolution of about 10 nm. © 2014 Optical Society of America.


A method for printing a desired periodic or quasi-periodic pattern of dot features into a photosensitive layer disposed on a substrate including the steps of designing a mask pattern having a periodic or quasi-periodic array of unit cells each having a ring feature, forming a mask with said mask pattern, arranging the mask substantially parallel to the photosensitive layer, arranging the distance of the photosensitive layer from the mask and illuminating the mask according to one of the methods of achromatic Talbot lithography and displacement Talbot lithography, whereby the illumination transmitted by the mask exposes the photosensitive layer to an integrated intensity distribution that prints the desired pattern.


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