First results of EUV-scanner compatibility tests performed on novel 'high-NA' reticle absorber materials

Stortelder, Jetske; Ebeling, Robert; Rijnsent, Corné; Putten, Michel van; Rooij-Lohmann, Veronique de; Smit, Maximilian; Storm, A.J.; Koster, N.B.; Lensen, Henk A.; Philipsen, Vicky; Opsomer, Karl; Thakare, Devesh; Feigl, Torsten; Naujok, Philipp

doi:10.1117/12.2600928

Cited by 4 publications

(7 citation statements)

References 9 publications

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“…There were no visible blisters on the surfaces of these samples, indicating that no damage had occurred. This finding is consistent with the conclusions of Stortelder et al [8], who found that TaCo alloy was resistant to hydrogen plasma.…”

Section: (B) Figure 8 (A) Cross Section Tem Of Ta-co Alloys (B) Eds-s...supporting

confidence: 93%

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Evaluation of Ta-Co alloys as novel high-k EUV mask absorber

Thakare¹,

Wu²,

Opsomer

et al. 2022

Optical and EUV Nanolithography XXXV

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An alternate mask absorber is a generally applicable approach as a mitigation strategy for Mask 3-D effects (M3D) observed in EUV lithography. It is also an efficient solution in a production-worthy environment compared to multilayer modification or Source Mask Optimization (SMO) techniques. Absorbers with a high EUV extinction coefficient k allow for lower Best Focus Variation (BFV) through pitch and reduced Telecentricity Errors (TCE). This study evaluates Ta-Co alloys as potential high-k mask absorbers. It includes an experimental study of film morphology, surface composition, and stability of Ta-Co alloys as well as a theoretical investigation of the imaging performance. The optical constants were determined from EUV angle-dependent reflectivity measurements for three selected compositions, viz. TaCo, Ta2Co, and TaCo3. The Ta-Co alloys exhibit a higher EUV extinction coefficient k compared to the currently used TaBN absorber. TaCo and Ta2Co demonstrated smooth surfaces, were stable in a hydrogen environment, and in mask cleaning solutions. These qualified compositions of Ta-Co alloys were selected for aerial image simulations and compared with a TaBN absorber. The optimized absorber thickness for Ta-Co alloy absorbers is based upon NILS enhancement, Threshold to Size (TtS) and balancing of diffraction order amplitudes. A 10 nm alternate line-space pattern with a pitch of 20 nm and 14 nm square contact holes with a pitch of 28 nm were considered for the simulation study using High NA 0.55 EUV lithography process settings. The through pitch imaging performance was evaluated using NILS, TCE and BFV as metrics. Ta-Co alloys allow for a reduction in M3D effects at smaller absorber thickness compared to a 60 nm TaBN absorber.

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Section: (B) Figure 8 (A) Cross Section Tem Of Ta-co Alloys (B) Eds-s...supporting

confidence: 93%

“…Alloying Ta with Co is expected to overcome this barrier. Stortelder et al recently reported the compatibility of TaCo in EUV scanner conditions in the presence of hydrogen radicals [8]. A thermodynamic assessment of the Co-Ta system was reported by Wang P. et al [9].…”

Section: Introductionmentioning

confidence: 95%

Evaluation of Ta-Co alloys as novel high-k EUV mask absorber

Thakare¹,

Wu²,

Opsomer

et al. 2022

Optical and EUV Nanolithography XXXV

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“…There were no visible blisters on the surfaces of these samples, indicating that no damage had occurred. This finding is consistent with the conclusions of Stortelder et al, 9 who found that TaCo alloy was resistant to hydrogen plasma. Although the growth appears to be slowing down with time, it is still significant.…”

Section: Stability In H-environmentsupporting

confidence: 93%

“…Stortelder et al recently reported the compatibility of TaCo in EUV scanner conditions in the presence of hydrogen radicals. 9 A thermodynamic assessment of the Co-Ta system was reported by Wang et al 10 Nevertheless, so far, the structure and optical properties of Ta-Co alloy thin films and their dependence on the alloy's composition have not yet been extensively addressed in the literature for EUV lithography.…”

Section: Introductionmentioning

confidence: 99%

“…In general, most of the studies that have proposed novel EUV mask absorbers belong to the noble materials category, which are difficult to pattern. 3,9 Also, it is challenging to pattern ferromagnetic materials like Co because they do not produce easily-removable volatile byproducts. 12 Although dry etch techniques that include Reactive Ion Etch (RIE), such as Cl 2 ∕Ar plasma etch, have been developed, the halogen reaction with Co to form metal chlorides is not volatile enough below the temperature of 200°C for practical applications.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Ta-Co alloys as novel high-k extreme ultraviolet mask absorber

Thakare

Opsomer

et al. 2023

J. Micro/Nanopattern. Mats. Metro.

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Background: A plausible approach for mitigating the mask 3-D (M3D) effects observed in extreme ultraviolet (EUV) lithography is to replace the existing mask absorber with alternative materials. Absorbers with a high EUV extinction coefficient k allow for lower best focus variation (BFV) through pitch and reduced telecentricity errors (TCEs).Aim: We aim to evaluate Ta-Co alloys as potential high-k mask absorbers from material suitability and imaging standpoints.Approach: We study the film morphology, surface composition, and stability of Ta-Co alloys in mask cleaning solutions and a hydrogen environment as present in the EUV scanner to assess the material suitability from an experimental aspect. Optical constants for three selected compositions, viz., TaCo, Ta 2 Co, and TaCo 3 , were determined from EUV angle-dependent reflectivity measurements. Next, utilizing rigorous simulation software, the imaging performance of Ta-Co alloys is evaluated and compared with the reference absorber. The recommended absorber thickness for Ta-Co alloy absorbers is based upon normalized image log slope (NILS) enhancement, threshold to size, and balancing of diffraction order amplitudes. A 10 nm line and space pattern with a pitch of 20 nm and 14 nm square contact holes with a pitch of 28 nm are used for the simulation study using high numerical aperture 0.55 EUV lithography process settings. The primary imaging metrics for through pitch evaluation include NILS, TCE, and BFV. Results:The Ta-Co alloys exhibit a higher EUV extinction coefficient k compared with the currently used Ta-based absorber. TaCo and Ta 2 Co demonstrate smooth surfaces and are stable in a hydrogen environment and in mask-cleaning solutions. Conclusion:Ta-Co alloys allow for a reduction in M3D effects at a lower absorber thickness compared with a 60 nm Ta-based reference absorber.

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Novel low-temperature and high-flux hydrogen plasma source for extreme-ultraviolet lithography applications

Stodolna,

Mechielsen,

van der Walle

et al. 2024

Journal of Vacuum Science &Amp; Technology B

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Inside extreme-ultraviolet (EUV) lithography machines, a hydrogen plasma is generated by ionization of the background gas by EUV photons. This plasma is essential for preventing carbon build-up on the optics, but it might affect functional performance and the lifetime of other elements inside the machine. The interaction of scanner materials and components with hydrogen plasma is investigated in controlled experiments using laboratory (off-line) setups, where the properties of EUV-generated plasmas are mimicked. Here, we present a novel experimental setup at TNO, where a low-temperature hydrogen plasma is generated by means of electron-impact ionization using a high-current, high-pressure electron beam (e-beam) gun. We show that the produced ion flux, peak ion energies, and radical-to-ion ratio are similar to that of the EUV-generated plasma. Since the e-gun has the option of operating the e-gun in the pulsed mode, it is possible to reproduce the time-dependent behavior of the scanner plasma as well. Moreover, as shown by Luo et al. [RSC Adv. 10, 8385 (2020)], electrons that impinge on surfaces mimic EUV photons in the generation of secondary electrons, which often drive radiation-induced processes (e.g., surface oxidation, reduction, and growth of carbon). We conclude that e-beam generated hydrogen plasma is a very promising technology for cost-effective lifetime testing of materials and optics, as compared to setups with EUV sources.

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First results of EUV-scanner compatibility tests performed on novel 'high-NA' reticle absorber materials

Cited by 4 publications

References 9 publications

Evaluation of Ta-Co alloys as novel high-k EUV mask absorber

Evaluation of Ta-Co alloys as novel high-k EUV mask absorber

Evaluation of Ta-Co alloys as novel high-k extreme ultraviolet mask absorber

Novel low-temperature and high-flux hydrogen plasma source for extreme-ultraviolet lithography applications

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