Dr. Bernhard Lüttgenau Profile

Dr. Bernhard Lüttgenau

at RWTH Aachen Univ

SPIE Involvement:

Author

Publications (12)

SPIE Journal Paper | 18 December 2024 Open Access

Achromatic Talbot lithography with partially coherent extreme ultraviolet radiation: mask and illumination parameter optimization

Bernhard Lüttgenau, Sascha Brose, Serhiy Danylyuk, Jochen Stollenwerk, Carlo Holly

JM3, Vol. 23, Issue 04, 043002, (December 2024) https://doi.org/10.1117/12.10.1117/1.JMM.23.4.043002

KEYWORDS: Lithography, Extreme ultraviolet lithography, Semiconducting wafers, Photoresist materials, Simulations, Spatial coherence, Extreme ultraviolet, Phase shifts, Image transmission, Design

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BackgroundCompact extreme ultraviolet (EUV) exposure tools utilizing partially coherent radiation are ideally suited for industrial EUV resist qualification regarding sensitivity, contrast, and resolution. For the broad applicability of the technology, the achievable resolution is crucial and requires thorough investigation.AimThe investigation of limiting factors for the achievable resolution for achromatic Talbot lithography is an important step in creating compact EUV exposure tools for industrial resist qualification and high-resolution patterning, accelerating the research and development of high-resolution EUV photoresists for next-generation microchips and processes.ApproachTo maximize the contrast of the resulting intensity distribution in the wafer plane for high-resolution patterns, both the illumination parameters and the utilized transmission masks are investigated by rigorous coupled-wave analysis simulations. The main influencing factors on the achievable resolution are identified and presented. In addition to the simulative optimization of the phase-shifting masks, the fabrication of the dense periodic nanopatterns becomes increasingly challenging for smaller periods. The mask fabrication process is therefore optimized to create stable and high-resolution periodic mask patterns.ResultsRigorous simulation of the achievable aerial image contrast in the wafer plane demonstrates the influence of partial coherence as well as the geometry and material selection of the mask. For the current mask design, the theoretical resolution is limited to a 14-nm half-pitch (wafer scale). The mask fabrication process is optimized leading to an experimental record resolution of 32.5-nm half-pitch for lines and spaces as well as 28-nm half-pitch for pinhole patterns with the presented demonstrator setup. Metal-based masks with optimized geometry will allow for the fabrication of 6.5-nm half-pitch patterns (wafer scale).ConclusionsAchromatic Talbot lithography can be used in compact EUV exposure tools with a theoretical resolution below 10-nm half-pitch (wafer scale). The main influencing factors on the achievable resolution are the mask material used and the degree of coherence of the utilized radiation.

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Proceedings Article | 12 November 2024 Presentation + Paper

Time-dependent characterization of total electron yield and outgassing in model EUV resist materials

Bernhard Lüttgenau, Meng Zhang, Qi Zhang, Cheng Wang, Ricardo Ruiz, Michael Connolly, Oleg Kostko

Proceedings Volume 13215, 132150H (2024) https://doi.org/10.1117/12.3034401

KEYWORDS: Outgassing, Extreme ultraviolet lithography, Extreme ultraviolet, Photoacid generators, Quenching, Photoresist materials, Chemical reactions, Ions, Thin films, Polymers

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Proceedings Article | 21 November 2023 Poster + Paper

Development of an ultra-compact inline transmission grating spectrograph for extreme ultraviolet wavelengths

Sascha Brose, Serhiy Danylyuk, Bernhard Lüttgenau, Ismael Gisch, Lars Lohmann, Jochen Stollenwerk, Carlo Holly

Proceedings Volume 12750, 127500Q (2023) https://doi.org/10.1117/12.2683682

KEYWORDS: Spectrographs, Extreme ultraviolet, Spectral resolution, Photodiodes, Optical filters, Optical design, Design and modelling, Tunable filters, Thin films, Thin film coatings

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Proceedings Article | 5 October 2023 Paper

Investigation of the resolution limit of Talbot lithography with compact EUV exposure tools

Bernhard Lüttgenau, Sascha Brose, Serhiy Danylyuk, Jochen Stollenwerk, Carlo Holly

Proceedings Volume 12802, 1280203 (2023) https://doi.org/10.1117/12.2675605

KEYWORDS: Photomasks, Extreme ultraviolet lithography, Lithography, Photoresist materials, Nanostructures, Simulations, Phase shifts, Extreme ultraviolet, Signal intensity, Semiconducting wafers

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Proceedings Article | 1 December 2022 Presentation + Paper

Toward the resolution limit of Talbot lithography with compact EUV exposure tools

Bernhard Lüttgenau, Sascha Brose, Serhiy Danylyuk, Jochen Stollenwerk, Carlo Holly

Proceedings Volume 12292, 1229208 (2022) https://doi.org/10.1117/12.2641693

KEYWORDS: Photomasks, Lithography, Extreme ultraviolet lithography, Phase shifts, Nanostructures, Extreme ultraviolet, Photoresist materials

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SPIE Journal Paper | 20 April 2022 Open Access

Latent image characterization by spectroscopic reflectometry in the extreme ultraviolet

Sophia Schröder, Lukas Bahrenberg, Bernhard Lüttgenau, Sven Glabisch, Sascha Brose, Serhiy Danylyuk, Jochen Stollenwerk, Peter Loosen, Carlo Holly

JM3, Vol. 21, Issue 02, 021208, (April 2022) https://doi.org/10.1117/12.10.1117/1.JMM.21.2.021208

KEYWORDS: Extreme ultraviolet, Reflectance spectroscopy, Reflectivity, Extreme ultraviolet lithography, Spectroscopy, Reflectometry, Photoresist materials, Imaging spectroscopy, Grazing incidence, Image processing

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Proceedings Article | 13 October 2021 Poster + Presentation + Paper

Design and realization of an in-lab EUV dual beamline for industrial and scientific applications

B. Lüttgenau, S. Brose, S. Danylyuk, J. Stollenwerk, P. Loosen, C. Holly

Proceedings Volume 11854, 1185419 (2021) https://doi.org/10.1117/12.2600935

KEYWORDS: Photomasks, Semiconducting wafers, Extreme ultraviolet, Extreme ultraviolet lithography, Lithography, Photoresist materials, Electron beam lithography, Nanostructures, Phase shifts

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Applications that require high resolution patterns are numerous, leading to an increasing demand for compact patterning tools and alternative lithographic concepts. For many scientific applications like biosensing or fabrication of metamaterials, or artificial crystals, the achievable resolution and the patterned area of the fabrication process are of main importance. In the field of high-volume manufacturing, there is a need for high-resolution patterning at the industrial exposure wavelength of 13.5 nm. The main industrial application for compact exposure tools is EUV photoresist development and its related process optimization. The overall patterned area is of minor interest. Instead, the focus is placed on the achievable resolution and quality of the intensity distribution used for the patterning tests. The realized EUV dual beamline allows to address both application fields in a single in-lab setup. By operating the source with an argon/xenon (Ar/Xe) gas mixture, a narrowband spectrum with a main wavelength of 10.9 nm is created without the need of spectral filtering. The resulting intensity of up to 2 mW/cm² in wafer plane allows large area patterning with highest throughput of several mm²/min. Single exposure fields of 2 x 2 mm² can be stitched together to achieve an overall patterned area of up to several cm² with minimal stitching borders of ~ 1 μm. By inserting a customized multilayer mirror into the beamline, the emission spectrum of the DPP source (operated with pure Xe gas) is in-band filtered to 13.5 nm, thus allowing qualification of industrial photoresists regarding sensitivity, contrast and resolution. The mask-wafer positioning system for the 13.5 nm beamline is designed for maximum rigidity to minimize relative movements between the mask and wafer that would lower the achievable resolution. Multi-field resolution test masks are created in-house and are exposed in a parallel manner to determine the achievable resist resolution in an efficient manner. Transmission mask designs are optimized by a rigorous simulation model. By tuning the pattern geometry on mask, different patterns like contact holes or nanopillars can be created on the wafer, tailored to the required application.

SPIE Journal Paper | 8 June 2021

EUV scattering from carbon nanotube pellicles: measurement and control

Ivan Pollentier, Marina Timmermans, Cedric Huyghebaert, Steven Brems, Emily Gallagher, Bernhard Lüttgenau, Sascha Brose

JM3, Vol. 20, Issue 02, 021007, (June 2021) https://doi.org/10.1117/12.10.1117/1.JMM.20.2.021007

KEYWORDS: Pellicles, Extreme ultraviolet, Scattering, Extreme ultraviolet lithography, Scanners, Carbon nanotubes, Sensors, Printing, Distance measurement, Scatter measurement

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Proceedings Article | 12 March 2021 Presentation + Paper

EUV scattering from CNT pellicles: measurement and control

Ivan Pollentier, Marina Timmermans, Cedric Huyghebaert, Steven Brems, Emily Gallagher, Bernhard Luettgenau, Sascha Brose

Proceedings Volume 11609, 1160911 (2021) https://doi.org/10.1117/12.2584718

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Proceedings Article | 22 February 2021 Presentation + Paper

Latent image characterization by spectroscopic reflectometry in the extreme ultraviolet

Sophia Schröder, Lukas Bahrenberg, Bernhard Lüttgenau, Sven Glabisch, Serhiy Danylyuk, Sascha Brose, Jochen Stollenwerk, Peter Loosen

Proceedings Volume 11611, 116111M (2021) https://doi.org/10.1117/12.2583830

KEYWORDS: Reflectance spectroscopy, Extreme ultraviolet, Photoresist materials, Reflectometry, Reflectivity, Spectroscopy, Imaging spectroscopy, Statistical modeling, Extreme ultraviolet lithography, Photoresist developing

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Proceedings Article | 13 October 2020 Poster + Paper

Design and realization of an industrial stand-alone EUV resist qualification setup

B. Lüttgenau, S. Brose, S. Choi, D. Panitzek, S. Danylyuk, R. Lebert, J. Stollenwerk, P. Loosen

Proceedings Volume 11517, 115171F (2020) https://doi.org/10.1117/12.2572803

KEYWORDS: Photomasks, Extreme ultraviolet, Lithography, Lithographic illumination, Phase shifts, Semiconducting wafers, Image resolution, Diffraction, Extreme ultraviolet lithography, Optical lithography

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The EUV laboratory exposure tool (EUV-LET) is a compact nanostructuring setup used for large-area patterning of arbitrary to periodic structures as well as industrial photoresist characterization in terms of sensitivity, contrast and resolution. The setup utilizes partially coherent radiation of a compact discharge-produced plasma (DPP) EUV source, spectrally filtered by a multilayer mirror to a wavelength of 13.5 nm with 4 % bandwidth (full width at half maximum, FWHM). The system is equipped with a precise positioning system for mask and wafer, which allows resist exposures at defined distances. For the generation of large area nanopatterns, the achromatic Talbot lithography is applied which is well suited for high-resolution patterning of periodic structures with partially coherent radiation from plasma-based EUV sources. Optimized transmission masks enable the generation of contrast rich intensity modulations leading to structure sizes below 40 nm. The theoretical resolution limit is in the sub-10 nm range by taking advantage of a two times mask pattern demagnification. The achievable practical resolution is mainly limited by the fabrication of the required transmission masks and the optical properties of the mask illumination. In this contribution, the EUV-LET serves as a basis to identify design rules for core building blocks of a future industrial EUV resist qualification setup (EUV-REQS). These core building blocks try to overcome the main limitations to resist testing at highest resolution as stated above. For the optimization of the illumination properties, the design of highly efficient illumination optics is investigated and presented. Aims of the illumination optics are the generation of high throughput, homogeneous illumination of the patterned mask area and the optimization of the EUV radiation properties to fulfill the requirements for Talbot lithography. For the generation of high-resolution intensity patterns in wafer plane, the design of resolution test masks is analyzed and evaluated by means of the achievable resolution and patterning uniformity. The fabrication of a resolution test mask and selected exposure results are shown as well.

Proceedings Article | 23 March 2020 Paper

Novel high-contrast phase-shifting masks for EUV interference lithography

B. Lüttgenau, S. Brose, S. Danylyuk, J. Stollenwerk, P. Loosen

Proceedings Volume 11323, 113231Q (2020) https://doi.org/10.1117/12.2551856

KEYWORDS: Photomasks, Diffractive optical elements, Lithography, Diffraction, Phase shifts, Diffraction gratings, Extreme ultraviolet, Modulation transfer functions, Modulation

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When it comes to the patterning of periodic structures like lines and spaces or contact hole arrays interference lithography can be effectively applied. By the use of ultrashort wavelengths in extreme ultraviolet (EUV) range, structure sizes can be pushed into the sub-100 nm region. Using advanced interference schemes, such as achromatic Talbot imaging, high-quality large-area patterning can be realized, e.g. for resist stochastics tests as well as for advanced fabrication processes in research and also small-batch production. Since the Talbot lithography only requires medium spatial coherence and accepts broadband emission, the approach can be used not only with coherent radiation as provided by synchrotron facilities but also with compact plasma-based EUV sources. In this contribution the theoretical resolution limit for the achromatic Talbot lithography is determined by simulations for the use of optimized phase-shifting transmission mask concepts illuminated by compact discharge-produced plasma EUV source operating at a main wavelength of 13.5 nm. The further effects that reduce a practical resolution limit, such as mask imperfections, positioner instabilities and resist contrast are also considered. With the realized EUV laboratory exposure tool and polymer-based contact hole phase-shifting masks 28 nm resolution has been demonstrated so far. Main limitations are found in the mask fabrication process that cannot be further down-scaled due to increasing aspect ratios and pattern degradation of the mask structures. To extend the developed nanopatterning technology to the sub-30 nm region, optimized phase-shifting transmission masks have to be designed and fabricated, enabling a contrast-rich intensity modulation in wafer plane. As size of the mask openings is approaching the exposure wavelength, mask geometry has to be optimized for every node. In this paper rigorous simulations of new mask designs optimized for the achromatic Talbot lithography are presented. For selected phase-shifting transmission masks, the influence of the mask material and geometry on the resulting aerial image is evaluated along with an analysis of the theoretical resolution limit.

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