Structural properties of subnanometer thick Y layers in extreme ultraviolet multilayer mirrors

Bosgra, J.; Zoethout, E.; Eerden, Ad M. J. van der; Verhoeven, J.; Kruijs, R. W. E. van de; Yakshin, Andrey; Bijkerk, F.

doi:10.1364/ao.51.008541

Cited by 10 publications

(7 citation statements)

References 19 publications

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“…6(b) it is seen that above 9.2 nm wavelength the optimal B thickness is within 0.7-1.2 nm range. Note that the state-of-art deposition technologies allow to use ≈0.3 nm thick interlayers [18,19], hence the calculated optimal B thickness values are feasible for real applications. In Fig.…”

Section: Results Of Calculationsmentioning

confidence: 99%

Phosphorus-based compounds for EUV multilayer optics materials

Медведев¹,

Yakshin²,

Kruijs³

et al. 2015

Opt. Mater. Express

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Abstract:We have evaluated the prospects of phosphorus-based compounds in extreme ultraviolet multilayer optics. Boron phosphide (BP) is suggested to be used as a spacer material in reflective multilayer optics operating just above the L-photoabsorption edge of P (λ ≈9.2 nm). Mo, Ag, Ru, Rh, and Pd were considered for applications as reflector materials. Our calculations for multilayer structures with perfect interfaces show that the Pd/BP material combination suggests the highest reflectivity values, exceeding 70% within the 9.2 -10.0 nm spectral range. We also discuss the potential of fabrication of BP-based multilayer structures for optical applications in the extreme ultraviolet range. References and links1. E. Spiller, Soft X-ray Optics (SPIE, Bellingham, 1994). 2. J. Larruquert, "Optical properties of thin film materials at short wavelengths," in Optical Thin Films and Coatings, A. Piegari, and F. Flory, eds. (Woodhead Publishing Limited, 2013). 415-417 (2013). 11. The direct application of the solid allotropes of sulphur (S) in multilayer structures is unlikely because of its high reactivity. For that reason instead of pure S some stable S-based compounds were considered for applications in multilayer structures. This is in spite of the fact that in this situation the increased chemical stability is achieved at the expense of the optical performance. Compounds of S with any material have higher absorbance for EUV radiation than that of pure S in the wavelength range where the application of S is favorable. Hence the elements to form compounds with S should be chosen using the two following criteria: 1) high chemical stability of the resulting compound; 2) optical constants of the resulting compound close to those of pure S. The analysis of the CXRO database of the optical constants indicates that the most promising candidates are boron (B), yttrium (Y), zirconium (Zr) and strontium (Sr). Obviously phosphorus-reach compounds are still the most attractive -these are B 2 S 3 , Y 2 S 3 , ZrS 2 and SrS. However B 2 S 3 , Y 2 S 3 and SrS are decomposed by water with the release of toxic H 2 S gas. Hence they do not meet the criterion of stability, and we focused on ZrS 2 . Our calculations for multilayers with ZrS 2 spacer indicate that ZrS 2 -based multilayer structures could only add to the B-based multilayer structures within a narrow 0.3 nm range above the L absorption edge of S.

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Section: Results Of Calculationsmentioning

confidence: 99%

Phosphorus-based compounds for EUV multilayer optics materials

Медведев¹,

Yakshin²,

Kruijs³

et al. 2015

Opt. Mater. Express

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“…To enhance the reflectivity of La/B-based multilayers, it might be beneficial to use the technology of contrast enhancement of the interface diffusion barriers similar to that applied in existing 13.5 nm deposition technologies. 10 Currently the measured normal incidence reflectance from real La/B-based multilayers is significantly lower than the theoretically predicted value. One of the factors limiting the reflectance is intermixing at the interfaces between La and B.…”

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confidence: 76%

Wavelength selection for multilayer coatings for lithography generation beyond extreme ultraviolet

Makhotkin

Zoethout

Louis

et al. 2012

J. Micro/Nanolith. MEMS MOEMS

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Abstract. The spectral properties of LaN/B and LaN∕B 4 C multilayer mirrors have been investigated in the 6.5 to 6.9 nm wavelength range, based on measured B and B 4 C optical constants. We show that the wavelength of optimal reflectance for boron-based optics is between 6.63 and 6.65 nm, depending on the boron chemical state. The wavelength of the maximum reflectance of the LaN∕B 4 C multilayer system is confirmed experimentally. Calculations of the wavelength-integrated reflectance for perfect ten-multilayer-mirror stacks show that a B-based optical column can be optimized for a wavelength larger than 6.65 nm.

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“…The multilayers were deposited by DC magnetron sputtering at MS1600 coater designed by Roth and Rau, which has UHV base pressure (10 −8 mbar). The coatings were done on superpolished 25 × 25 mm 2 Si substrates with native oxide and 0 15 ±0 05 nm surface roughness. The multilayers had an accurately controlled period thickness gradient along the surface of the samples to cover a certain range of wavelengths (at a fixed angle of incidence), or a range of angles of incidence (at a fixed wavelength) at which the multilayers would have the highest reflection.…”

Section: Methodsmentioning

confidence: 99%

“…These mirrors have a theoretical reflectance of more than 73% (Si-capped) at near normal incidence, with the best experimentally produced interface engineered multilayers reaching a reflectance of 70.3%. 2 Since the optical systems may consist of up to 11 mirrors, the total throughput is essentially reduced. This emphasizes the importance of maximizing the mirror reflectivity and, at the same time, the yield of the respective EUV light source.…”

Section: Introductionmentioning

confidence: 99%

Angular and Spectral Bandwidth of Extreme UV Multilayers Near Spacer Material Absorption Edges

Zameshin

Yakshin

Chandrasekaran

et al. 2019

j nanosci nanotechnol

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High resolution imaging systems for EUV range are based on multilayer optics. Current generation of EUV lithography uses broadband Sn LPP sources, which requires broadband mirrors to fully utilize the source power. On the other hand, there always remains a possibility to use FEL or synchrotron as EUV source. FEL can produce very bright narrowband EUV light of a tunable wavelength, and the spectral bandwidth of the mirror is no longer a restriction. In this paper we look at the consequences of switching to different wavelengths if FEL source is used. For instance, it is known that the reflectance of Mo/Si multilayers increases when approaching Si Ledge , and the spectral bandwidth drops. But the behavior of an angular bandwidth (and its relation with the spectral bandwidth) is usually left out. It is also sometimes assumed that these bandwidths are correlated. For a large aperture EUV optical system with diffraction-limited resolution angular acceptance of a mirror is also a very important parameter. We show that the angular bandwidth of several multilayer systems (Mo/Si, Mo/Be, Ru/Si, Ru/B, La/B) actually increases close to spacer absorption edges, opposite to what occurs with the spectral bandwidth. We study this effect and show that it is caused by an interplay of changing optical constants of respective materials used in these multilayer combinations. We also provide an experimental check of the angular bandwidth of Mo/Si multilayers at 13.5 and 12.6 nm, which confirms our calculations.

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Structural properties of subnanometer thick Y layers in extreme ultraviolet multilayer mirrors

Cited by 10 publications

References 19 publications

Phosphorus-based compounds for EUV multilayer optics materials

Phosphorus-based compounds for EUV multilayer optics materials

Wavelength selection for multilayer coatings for lithography generation beyond extreme ultraviolet

Angular and Spectral Bandwidth of Extreme UV Multilayers Near Spacer Material Absorption Edges

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