Mitigation of image contrast loss due to mask-side non-telecentricity in an EUV scanner

Shih, Chun‐Hsing; Yu, Shinn-Sheng; Lu, Yi; Chung, Chia-Chun; Chen, Jack J. H.; Yen, Anthony

doi:10.1117/12.2085092

Cited by 8 publications

(7 citation statements)

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“…Thinner absorbers are preferable as they reduce the contribution of absorber shadowing to pattern shift through focus, as it causes an imbalance in the diffraction orders intensity [5]. Furthermore, with n is close to unity due to Al, there is less phase imbalance between illumination poles under off-axis illumination [6]. Imaging simulations predict all modeled Ni x Al y absorbers to surpass TaBN and Ni in mitigating pattern shift through focus.…”

Section: Euv Imaging Simulationsmentioning

confidence: 98%

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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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Section: Euv Imaging Simulationsmentioning

confidence: 98%

“…These effects are experimentally observable, as feature orientation-dependent shadowing effects [3], best focus variation through pitch [4], feature size-dependent pattern shift through focus [5,6], and pattern asymmetry and contrast loss [7]. Selecting the correct mask absorber material and thickness helps in reducing M3D effects [2,8,9].…”

Section: Figurementioning

confidence: 99%

Ni-Al Alloys as Alternative EUV Mask Absorber

et al. 2018

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“…The complex interaction among incident electric fields, three-dimensional absorbers, and multi-layer topography makes the required corrections depend not only on pattern positions but also on pattern sizes, pitches, and types. Figure 5 shows the image contrast loss due to maskside non-telecentricity [32]. It can be observed that horizontal 1-D equal L/S patterns of 30 nm pitch (P30H) suffer from rather high contrast loss compared to P60H.…”

Section: Shadowing Effectmentioning

confidence: 96%

“…Image contrast loss due to non-telecentricity at the mask side is more serious in dense patterns (from the presentation slides of[32]). …”

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confidence: 98%

EUV and e-beam manufacturability

Chang

Liu

Fang

2015

Proceedings of the 52nd Annual Design Automation Conference

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As process nodes continue to shrink, the semiconductor industry faces severe manufacturing challenges. Two most expected technologies may push the limits of next-generation lithography: extreme ultraviolet lithography (EUVL) and electron beam lithography (EBL). EUVL works by emitting intense beams of ultraviolet light that are reflected from a reflective mask into a resist for nanofabrication, while EBL scans focused beams of electrons to directly draw high-resolution feature patterns on a resist without employing any mask. Each of the two technologies encounters unique design challenges and requires solutions for a breakthrough. In this paper, we focus on the design-for-manufacturability issues for EUVL and EBL. We investigate the most critical design challenges of the two technologies, flare and shadowing effects for EUVL, and heating, stitching, fogging, and proximity effects for EBL. Preliminary solutions for these effects are explored, which can contribute to the continuing scaling of the CMOS technology. Finally, we provide future research directions for these key effects.Extreme ultraviolet lithography, electron beam lithography, physical design, design for manufacturability, flare effect, shadowing effect, heating effect, stitching effect, proximity effect, fogging effect *

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“…8 Variation of the incidence direction of the light on the mask versus the position in the illumination source causes image blur and deteriorates the contrast of the obtained images. 9,10 Deformation of the phase of the propagating light by the thick absorber causes pitch-dependent shifts of the best focus position, asymmetric process windows, and other aberration such as effects with adverse impact on the image quality. [11][12][13] The diffraction scheme in Fig.…”

Section: D Mask Effects In Euv Lithographymentioning

confidence: 99%

Perspectives and tradeoffs of absorber materials for high NA EUV lithography

Erdmann

Mesilhy

Evanschitzky

et al. 2020

J. Micro/Nanolith. MEMS MOEMS

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Next-generation extreme ultraviolet (EUV) systems with numerical apertures of 0.55 have the potential to provide sub-8-nm half-pitch resolution. The increased importance of stochastic effects at smaller feature sizes places further demands on scanner and mask to provide high contrast images. We use rigorous mask diffraction and imaging simulation to understand the impact of the EUV mask absorber and to identify the most appropriate optical parameters for high NA EUV imaging. Simulations of various use cases and material options indicate two main types of solutions: high extinction materials, especially for lines spaces, and low refractive index materials that can provide phase shift mask solutions. EUV phase masks behave very different from phase shift masks for DUV. Carefully designed low refractive index materials and masks can open up a new path toward high contrast edge printing. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Mitigation of image contrast loss due to mask-side non-telecentricity in an EUV scanner

Cited by 8 publications

References 1 publication

Ni-Al Alloys as Alternative EUV Mask Absorber

Ni-Al Alloys as Alternative EUV Mask Absorber

EUV and e-beam manufacturability

Perspectives and tradeoffs of absorber materials for high NA EUV lithography

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