Free-standing spectral purity filters for extreme ultraviolet lithography

Чхало, Н. И.; Дроздов, М. Н.; Kluenkov, E. B.; Lopatin, A. Ya.; Luchin, V. I.; Salashchenko, N. N.; Tsybin, N. N.; Sjmaenok, Leonid A.; Banine, VY Vadim; Yakunin, A. M.

doi:10.1117/1.jmm.11.2.021115

Cited by 42 publications

(24 citation statements)

References 20 publications

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“…Besides absorptive filters that block wider spectral ranges, XUV monitoring and metrology is making use mainly of periodic multilayer mirrors for selective reflection [5][6][7][8][9][10][11] of a desired, narrowband wavelength interval. However, with periodic layers, the shape of the spectral transmission peak is fixed due to the periodicity of the layer stack.…”

Section: Introductionmentioning

confidence: 99%

Reflective aperiodic multilayer filters for metrology at XUV sources

et al. 2020

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We present a general method for designing XUV aperiodic multilayer mirrors that can mimic a given target spectrum, specifically, the spectral transmission of an XUV optical system. The method is based on minimizing a merit function and using fidelity parameters that quantify the matching of the multilayer reflectivity spectrum with that of the target spectrum. To assess the feasibility of fabricating such a system, we show how to reduce the layer-to-layer thickness variations throughout the aperiodic layer stack. We demonstrate the design method using an example of an EUV optical system composed of 12 identical Mo/Si multilayer mirrors having a reflectivity peak at 13.5 nm. We found that the target spectrum can be mimicked with high fidelity either with a single reflection at an aperiodic multilayer mirror combined with standard absorbing filters or, if required, with two subsequent reflections at a mimic mirror. These examples demonstrate the applicability for metrology at XUV sources, including spectrally proper source imaging. Because our approach is of general applicability, the process can be used to mimic any other narrowband, single-peaked target spectrum in the XUV region.

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Section: Introductionmentioning

confidence: 99%

Reflective aperiodic multilayer filters for metrology at XUV sources

et al. 2020

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“…Different methods have been developed to suppress the out-of-band UV radiation in the reflected spectrum, including multilayer gratings [12,13], antireflection layers [14,15], and freestanding membranes/ filters [16,17]. However, these methods either cannot suppress the whole band of UV light, or a large amount of EUV power is lost due to the added structures.…”

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confidence: 99%

“…The peak reflectance of the uncoated standard ML is 68.3% while the Si pyramids-on-the ML sample shows a reflectance of 56.2%. The EUV "transmittance" at 13.5 nm of this system is defined as R pyra: ∕R ML 82.2%, significantly higher than the free- standing membranes [16]. As the pyramids are made of Si, which is almost nonreflective for EUV radiation, the diffraction and scattering of EUV light can be neglected.…”

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confidence: 99%

UV spectral filtering by surface structured multilayer mirrors

et al. 2014

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A surface structured extreme ultraviolet multilayer mirror was developed showing full band suppression of UV (λ=100-400 nm) and simultaneously a high reflectance of EUV light (λ=13.5 nm). The surface structure consists of Si pyramids, which are substantially transparent for EUV but reflective for UV light. The reflected UV is filtered out by blazed diffraction, interference, and absorption. A first demonstration pyramid structure was fabricated on a multilayer by using a straightforward deposition technique. It shows an average suppression of 14 times over the whole UV range and an EUV reflectance of 56.2% at 13.5 nm. This robust scheme can be used as a spectral purity solution for all XUV sources that emit longer wavelength radiation as well.

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“…This IR light will be highly reflected by the metal in the multilayer mirror and propagated into the optical system causing heat load problems. 90 Several methods have been proposed to block the IR transmission including a foil filter, 82 a grid filter, 91 or a gaseous filter. 92 Grating based EUV reflectors can also be used to separate the IR and EUV light [93][94][95] which will be further discussed in Section III.…”

Section: Ir Antireflectionmentioning

confidence: 99%

“…77,78 The spectral purity of EUV plasma sources, and the mitigation of UV and IR have actually become two of the challenges in the development of EUV photo-lithography. 79 A multilayer mirror combined with different filters can be used to improve the spectral purity, [80][81][82] but it usually has a poor EUV transmission and a free-standing filter might be prone to damage. Recently, several new schemes of spectral purity filters (SPF) integrated with multilayer structures have been developed which show a high suppression factor at the unwanted wavelengths at much higher EUV efficiency.…”

Section: High Spectral Purity ML Mirrorsmentioning

confidence: 99%

Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

Huang

Медведев

Kruijs

et al. 2017

Applied Physics Reviews

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Extreme ultraviolet and soft X-ray (XUV) multilayer optics have experienced significant development over the past few years, particularly on controlling the spectral characteristics of light for advanced applications like EUV photolithography, space observation, and accelerator- or lab-based XUV experiments. Both planar and three dimensional multilayer structures have been developed to tailor the spectral response in a wide wavelength range. For the planar multilayer optics, different layered schemes are explored. Stacks of periodic multilayers and capping layers are demonstrated to achieve multi-channel reflection or suppression of the reflective properties. Aperiodic multilayer structures enable broadband reflection both in angles and wavelengths, with the possibility of polarization control. The broad wavelength band multilayer is also used to shape attosecond pulses for the study of ultrafast phenomena. Narrowband multilayer monochromators are delivered to bridge the resolution gap between crystals and regular multilayers. High spectral purity multilayers with innovated anti-reflection structures are shown to select spectrally clean XUV radiation from broadband X-ray sources, especially the plasma sources for EUV lithography. Significant progress is also made in the three dimensional multilayer optics, i.e., combining micro- and nanostructures with multilayers, in order to provide new freedom to tune the spectral response. Several kinds of multilayer gratings, including multilayer coated gratings, sliced multilayer gratings, and lamellar multilayer gratings are being pursued for high resolution and high efficiency XUV spectrometers/monochromators, with their advantages and disadvantages, respectively. Multilayer diffraction optics are also developed for spectral purity enhancement. New structures like gratings, zone plates, and pyramids that obtain full suppression of the unwanted radiation and high XUV reflectance are reviewed. Based on the present achievement of the spectral tailoring multilayer optics, the remaining challenges and opportunities for future researches are discussed.

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Free-standing spectral purity filters for extreme ultraviolet lithography

Cited by 42 publications

References 20 publications

Reflective aperiodic multilayer filters for metrology at XUV sources

Reflective aperiodic multilayer filters for metrology at XUV sources

UV spectral filtering by surface structured multilayer mirrors

Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

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