High NA EUV scanner: obscuration and wavefront description

Winter, Laurens de; Tudorovskiy, Timur; Schoot, Jan van; Troost, Kars; Stinstra, Erwin; Hsu, Stephen; Gruner, Toralf; Mueller, Juergen; Mack, Ruediger; Bilski, Bartosz; Zimmermann, J.; Graeupner, Paul

doi:10.1117/12.2572878

Cited by 7 publications

(8 citation statements)

References 15 publications

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“…In the optical design of 0.55NA imaging system, a physical pupil obscuration with a approximated radius of σ=0.21 is used, which means 0.55NA optical system allows to increase image contrast by partial dark-field imaging. 13,14 To study the obscuration impact on lithographic imaging performance, we re-run the SMO jobs of binary mask at metal pitch 20nm with a minimum σ=0.21, to avoid putting source points inside the pupil obscuration during source optimization. The impact on the NILS of LS at pitch 20nm is shown in Fig.…”

Section: Appendix a Pupil Obscuration Impact Discussionmentioning

confidence: 99%

Feasibility of logic metal scaling with 0.55NA EUV single patterning

Xu¹,

Tan

Philipsen³

et al. 2023

Optical and EUV Nanolithography XXXVI

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By adopting the new design of the optics within the scanner, high-NA (0.55NA) EUV lithography enables higher resolution, which will push the EUV single patterning down to pitch 16nm (k1=0.34, the same k1 value as pitch 28nm for 0.33NA EUV single patterning). Therefore, 0.55NA EUVL is projected to print the most critical features of 2nm node (and beyond) logic chips with less patterning steps than 0.33NA EUVL, and is highly expected by the industry. Besides, novel low-n low-k absorber attenuated phase shift masks (low-n attPSMs) are commercially available recently, which have shown substantial imaging, as well as patterning performance improvements both in simulations and experiments. Thus, in this paper, we evaluate the feasibility and limits of logic metal scaling with 0.55NA EUV single pattering using source mask optimization tool, both binary and low-n attPSMs are used to pattern an imec N3 (pitch 28nm, foundry N2 equivalent) random logic metal design and the linear scaled versions (down to pitch 18nm). The impact of design orientations (horizontal vs. vertical) and mask tones (dark field vs. bright field) on patterning fidelity and overall process window is evaluated.

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Section: Appendix a Pupil Obscuration Impact Discussionmentioning

confidence: 99%

Feasibility of logic metal scaling with 0.55NA EUV single patterning

Xu¹,

Tan

Philipsen³

et al. 2023

Optical and EUV Nanolithography XXXVI

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“…10 A central obscuration accounting 20% of the radius (inner radius ε ¼ 0.2) in an anamorphic projection mirror was employed. 11 Our simulations make use of the Mo/Si multi-layer (ML) mirror mask model described by Makhotkin et al 12 The absorber stack is defined using the experimentally determined optical constants n and k of Ta-Co alloys. 9 Ru capping layer recession of 0.5 nm in the mask trench region is considered to account for an over-etch that may happen during the patterning of the absorber.…”

Section: Simulation Setupmentioning

confidence: 99%

Optimizing extreme ultraviolet lithography imaging metrics as a function of absorber thickness and illumination source: a simulation case study of Ta-Co alloy

Thakare,

Delabie,

Philipsen

2023

J. Micro/Nanopattern. Mats. Metro.

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Background: The optical properties of the absorber material and its thickness, along with the choice of illumination, govern the imaging performance of an EUV photomask. Consequently, the imaging metrics, viz., normalized image log slope (NILS), telecentricity error (TCE), and best focus variation (BFV) through pitch, exhibit a trade-off. Previous studies have focused on either reflectivity or phase shift induced by the absorber to determine the optimum absorber thickness, which ignores the structure of the patterns on the mask.Aim: This simulation study intends to facilitate the optimum absorber thickness selection with an emphasis on diffraction order analysis of the line and space (LnS) pattern and investigates the impact of illumination source shapes for a Ta-Co alloy absorber mask.Approach: We investigate the behavior of imaging metrics as a function of the absorber thickness using literature-recommended illumination source shapes. NILS, TCE, throughput criterion, diffraction order's amplitude ratio, and phase difference are the critical parameters when selecting the optimum absorber thickness. A through-pitch imaging performance of the Ta-Co alloy absorber with recommended thicknesses is compared with the reference 60 nm Ta-based absorber using leaf dipole (LDP), inner half leaf dipole (IHLDP), and outer half leaf dipole (OHLDP) for LnS patterns with a target trench of 10 nm and pitch ranging from 20 to 40 nm. Results:The proposed absorber thickness optimization methodology validates the reference Ta-based absorber thickness and recommends 52 nm of Ta-Co alloy absorber thickness. IHLDP and OHLDP demonstrate enhanced NILS for the smallest pitch. However, this behavior is inconsistent throughout the pitch. IHLDP exhibits low TCE. However, because of higher BFV, the advantages are not exceptionally beneficial.Conclusions: A holistic approach makes the proposed absorber thickness optimization methodology reliable and generally applicable. The through-pitch simulation outcomes at selected absorber thickness favor a conventional full-leaf dipole for the studied imaging metrics.

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“…In this section, we investigate the sensitivity of aberrations in high NA EUV on the M0 layer with a pitch of 20-24nm. Our approach is simple: (1) we vary each aberration term (Titian 5-36) [12] by multiple values ranging from -0.2nm to +0.2nm, one at a time. (2) We use high NA EUV to image the M0 layouts with each of these aberrations.…”

Section: Simulations Of Aberration Sensitivity On M0 Layer In High Na...mentioning

confidence: 99%

Computational evaluation of critical logical metal layers of pitch 20-24nm and the aberration sensitivity in high NA EUV single patterning

Gao

Chen

Zimmermann

2023

DTCO and Computational Patterning II

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As chip manufacturers seek to reduce the pitch of metal layers, there is growing interest in replacing the multiple patterning process of 0.33NA EUV with a single patterning of high NA (0.55NA) EUV. However, to resolve a logic metal layout with a minimum pitch of 20-24nm, careful use of resolution enhancement techniques (RETs) and SMO (source mask optimization) is required in high NA EUV. Logic metal patterns are complex and have various feature designs, making it essential to ensure sufficient patterning performance across all pitches and for variations of tip-to-tip (T2T) structures with a tight size. In this study, we simulated and evaluated patterning on a typical logic metal layout representing 1.4nm to 1nm technology nodes. Our study demonstrates that compromised criteria are necessary to ensure the NILS (normalized image log-slope) level of the minimum pitch and the overlap critical dimension (CD) process window (PW). In optical proximity correction (OPC), sub-resolution assistant features (SRAF) help to improve the process window of isolated and semi-iso line-and-space (L/S) patterns. However, we found that the limiting patterns are the tight T2T structures. Aberration sensitivity showed a linear response that is more pronounced to pattern placement errors (PPE) than to CDs. The coma series aberration showed the highest sensitivity to PPE and CD. Overall, our study demonstrates that RETs, rigorous SMO solutions, and a minimum T2T size are required to achieve the replacement of 0.33NA EUV multi-patterning with a 0.55NA EUV single patterning (SP) for logic metal layers with minimum pitches of 20-24nm.

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High NA EUV scanner: obscuration and wavefront description

Cited by 7 publications

References 15 publications

Feasibility of logic metal scaling with 0.55NA EUV single patterning

Feasibility of logic metal scaling with 0.55NA EUV single patterning

Optimizing extreme ultraviolet lithography imaging metrics as a function of absorber thickness and illumination source: a simulation case study of Ta-Co alloy

Computational evaluation of critical logical metal layers of pitch 20-24nm and the aberration sensitivity in high NA EUV single patterning

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