Evaluating the Optical Index of Ta and Ta-Based Absorbers for an Extreme Ultraviolet Mask Using Extreme Ultraviolet Reflectometry

Hosoya, Morio; Sakaya, Noriyuki; Nozawa, Osamu; Shiota, Yuki; Hamamoto, Kazuo; Nagarekawa, Osamu; Shimojima, Shoji; Shoki, Tsutomu; Watanabe, Takeo; Kinoshita, Hiroo

doi:10.1143/jjap.47.4898

Cited by 7 publications

(8 citation statements)

References 28 publications

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“…When comparing our data at 91.85 eV to the existing literature of direct measurements of the optical constants [30,31,32,33,34,35,36], we find the differences in values, that are summarized in figure 4 alongside those, calculated from atomic scattering factors [10,37,38]. Of those references, the data of Windt et al on Mo, Pt, Ru, and Ta [30], as well as the data of Rodríguez-de Marcos et al on Te [36], Hosoya et al on Ta [35] were obtained from reflection type measurements and are therefore very comparable to ours with respect to methodology and outcome. An exception is the value of Diel et al on Ni [32], which is far off our value and the one from CXRO [10].…”

Section: Resultsmentioning

confidence: 94%

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Determination of optical constants of thin films in the EUV

Ciesielski

Saadeh

Philipsen³

et al. 2022

Appl. Opt.

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The determination of fundamental optical parameters is essential for the development of new optical elements such as mirrors, gratings, or photomasks. Especially in the extreme ultraviolet (EUV) and soft x-ray spectral range, the existing databases for the refractive indices of many materials and compositions are insufficient or are a mixture of experimentally measured and calculated values from atomic scattering factors. Since the physical properties of bulk materials and thin films with thicknesses in the nanometer range are not identical, measurements need to be performed on thin layers. In this study we demonstrate how optical constants of various thin film samples on a bulk substrate can be determined from reflection measurements in the EUV photon energy range from 62 eV to 124 eV. Thin films with thickness of 20 nm to 50 nm of pure Mo, Ni, Pt, Ru, Ta, and Te and different compositions of N i x A l x , PtTe, P t x M o , R u x T a x , R u 3 R e , R u 2 W , and TaTeN were prepared by DC magnetron sputtering and measured using EUV reflectometry. The determination optical constants of the different materials are discussed and compared to existing tabulated values.

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Section: Resultsmentioning

confidence: 94%

“…From atomic scattering factors: black triangles[10], green triangles[37,38], from reflectance measurements: blue rectangles[30]. From various other studies: magenta diamonds, Mo[31], Ni[32], Pt[33], Ru[34], Ta[35], Te[36].…”

mentioning

confidence: 99%

Determination of optical constants of thin films in the EUV

Ciesielski

Saadeh

Philipsen³

et al. 2022

Appl. Opt.

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“…In-situ XRD (IS-XRD) to inspect crystallization across temperature range [20,26] The absorber film morphology is preferably nano-crystalline or amorphous, which is challenging to achieve for most single metals. Crystallinity however, is very likely to impair surface roughness and etch bias.…”

Section: Film Morphologymentioning

confidence: 99%

“…Surface chemical state X-ray photoelectron spectroscopy (XPS) [26] Bulk elemental composition Sputter-assisted XPS for composition depth profile TEM with energy dispersive X-ray analysis (TEM-EDS) Density for optical constant estimation X-ray reflectometry (XRR)…”

Section: Characterization Metrologymentioning

confidence: 99%

Ni-Al Alloys as Alternative EUV Mask Absorber

et al. 2018

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Extreme ultraviolet (EUV) lithography is being industrialized as the next candidate printing technique for high-volume manufacturing of scaled down integrated circuits. At mask level, the combination of EUV light at oblique incidence, absorber thickness, and non-uniform mirror reflectance through incidence angle, creates photomask-induced imaging aberrations, known as mask 3D (M3D) effects. A possible mitigation for the M3D effects in the EUV binary intensity mask (BIM), is to use mask absorber materials with high extinction coefficient κ and refractive coefficient n close to unity. We propose nickel aluminide alloys as a candidate BIM absorber material, and characterize them versus a set of specifications that a novel EUV mask absorber must meet. The nickel aluminide samples have reduced crystallinity as compared to metallic nickel, and form a passivating surface oxide layer in neutral solutions. Composition and density profile are investigated to estimate the optical constants, which are then validated with EUV reflectometry. An oxidation-induced Al L2 absorption edge shift is observed, which significantly impacts the value of n at 13.5 nm wavelength and moves it closer to unity. The measured optical constants are incorporated in an accurate mask model for rigorous simulations. The M3D imaging impact of the nickel aluminide alloy mask absorbers, which predict significant M3D reduction in comparison to reference absorber materials. In this paper, we present an extensive experimental methodology flow to evaluate candidate mask absorber materials.

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“…In this study, the EUV mask reflectometer [11] was used for the EUV transmittance measurement, which was located at the BL-10 beamline of NewSUBARU synchrotron light facility. Figure 3 shows the photograph of the EUV mask reflectometer installed at the BL10.…”

Section: Transmittance Measurement Methodsmentioning

confidence: 99%

Development of the Transmittance Measurement for EUV Resist by Direct-Resist Coating on a Photodiode

Mamezaki

Watanabe

Harada

et al. 2016

J. Photopol. Sci. Technol.

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To increase the sensitivity of extreme-ultraviolet (EUV) resist, the method of adding high absorption material in base resin of the resist such as hafnium or zirconium metal has been developed. Since the EUV absorption of the base resin increases, the secondary electron emissions would increase to have a highresist-exposure sensitivity. Thus to achieve the high sensitive EUV resist, it is important to evaluate EUV absorption of the EUV resist precisely. We have developed a novel transmittance measurement method to evaluate EUV resist absorption with high precision at BL10 beamline of NewSUBARU synchrotron light facility. In this novel method, a sample resist was coated on an EUV photodiode directly. The EUV transmittance of the resist was measured with photodiode signals before and after the coating. The resist thickness uniformity coating on a photodiode has much smaller value compared to that coating on a freestanding membrane. By novel method, the measurement precisions of the resist thickness and the EUV transmittance were significantly improved. As the result, the high measurement precision of absorption coefficient of 1% was achieved. This novel method will help the development of high sensitive EUV resist with the high-absorption material.

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Evaluating the Optical Index of Ta and Ta-Based Absorbers for an Extreme Ultraviolet Mask Using Extreme Ultraviolet Reflectometry

Cited by 7 publications

References 28 publications

Determination of optical constants of thin films in the EUV

Determination of optical constants of thin films in the EUV

Ni-Al Alloys as Alternative EUV Mask Absorber

Development of the Transmittance Measurement for EUV Resist by Direct-Resist Coating on a Photodiode

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