Improving exposure latitudes and aligning best focus through pitch by curing M3D phase effects with controlled aberrations

Franke, Joern-Holger; Bekaert, Joost; Blanco, Víctor Francisco Sampedro; Look, Lieve Van; Wahlisch, Felix; Lyakhova, Kateryna; Adrichem, Paul van; Maslow, Mark John; Schiffelers, Guido; Hendrickx, Eric

doi:10.1117/12.2537104

Cited by 16 publications

(36 citation statements)

References 26 publications

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“…To simplify this step, a Telecentric Sigma Point Source (TS-PS) is used as an illumination source. For a TS-PS, NILS remains constant as a function of focus [23]. This eliminates the necessity of an extra variable (focus), resulting in faster simulations.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…The evaluation metrics NILS, TCE, BFV and TtS have a strong dependence on the choice of illumination. Franke et al [23] suggests using either an inner half leaf or an outer half leaf shaped dipole to observe an increment in NILS for Ta-based absorbers. Similarly, a two-dimensional incision resulting in quarter poles for quasar illumination is also recommended for contact holes.…”

Section: 𝑇ℎ𝑟𝑜𝑢𝑔ℎ𝑝𝑢𝑡 𝐶𝑟𝑖𝑡𝑒𝑟𝑖𝑜𝑛 (𝑇𝑝𝑇) = 𝑁𝐼𝐿𝑆 √𝑇𝑡𝑆 Equationmentioning

confidence: 99%

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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: Simulation Methodsmentioning

confidence: 99%

Section: 𝑇ℎ𝑟𝑜𝑢𝑔ℎ𝑝𝑢𝑡 𝐶𝑟𝑖𝑡𝑒𝑟𝑖𝑜𝑛 (𝑇𝑝𝑇) = 𝑁𝐼𝐿𝑆 √𝑇𝑡𝑆 Equationmentioning

confidence: 99%

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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show abstract

“…M3D induced phase deformation has been regarded as one of the most significant issues in EUV [11][12][13][14][15] . Phase shift happens when the light travels between media with a difference in refractive index and depends on the angle of incidence.…”

Section: Absorber Materials For Mitigation Of Mask 3d Effectmentioning

confidence: 99%

Hyper-NA EUV lithography: an imaging perspective

Lee¹,

Franke

Philipsen³

et al. 2023

Optical and EUV Nanolithography XXXVI

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To print ever smaller features at high contrast projection lithography technology has evolved to shorter wavelength light and larger NA. After enabling the EUV wavelength, the industry is looking into increasing the NA. This study aims to identify EUV specific challenges regarding NA scaling beyond 0.55. We study if EUV imaging can still work at this higher NA and whether specific changes to the mask stack are required. At NA's much higher than 0.55, new effects like polarization will play a role, and larger impact of ultimate mask resolution and material interactions is expected. Already at NA 0.55, a small contrast loss is predicted due to the use of unpolarized light in the scanner. Further increasing the NA will enhance the contrast loss. We study these polarization effects in detail and assess their impact quantitatively for a set of generic building blocks. In addition, the larger incidence angles on mask when the NA increases above 0.55, will further enhance the M3D effects forcing additional mask changes. To enable proper imaging at high incidence angles, new mask architectures, that include changes in the EUV mask absorber and multilayer, will have to be tested using rigorous simulations.

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“…They can have a significant impact on telecentricity error, best focus (BF) shift, and through slit printability issues at wafer level. [4][5][6][7] To mitigate M3D effects, various alternative masks were studied and proposed. [8][9][10][11][12][13][14][15][16] Available today, low-n masks are expected to have different imaging performance with respect to traditional Ta-based absorber (ABS) mask: higher normalized image log slope (NILS), M3D effects reduction for carefully selected biases, and reduction in dose to size due to larger mask biasing.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Lines and Spaces printing and general understanding of imaging with dark field low-n mask

Kovalevich

Look

Franke

et al. 2023

J. Micro/Nanopattern. Mats. Metro.

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Background: One of the ways to push down resolution limits in extreme ultraviolet (EUV) lithography is to use alternative masks. New types of absorbers are being broadly investigated for current 0.33 NA as well as for high NA of 0.55. Aim:We study the imaging performance of a low-n/low-k absorber (ABS) dark field (DF) mask for lines and spaces (LS) printing at 0.33 NA.Approach: Experimentally and via simulations, we investigate the use of low-n DF masks for a metal direct print application and compare low-n mask performance with Ta-based ABS masks.Results: Compared to a Ta-based ABS mask used nowadays, the low-n DF mask brings contrast gain for dense LS. Also, for low-n masks, we observe large best focus (BF) shifts for isolated features with respect to dense features and change of bias. Hence, strong mask critical dimensions (CD) control is needed. We demonstrate how adding assist features can align BF through pitch. In addition, placing subresolution assist features (SRAFs) significantly enhances exposure latitude for semi/iso and iso-LS and improves the overlapping process window for selected cases.Conclusions: These investigations show that low-n DF masks can enhance the imaging of LS through pitch if SRAFs are used and a good mask CD control is achieved. Our work further adds fundamental understanding to advantages observed for a metal direct print application of alternative ABS masks for the current and future EUV tools.

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Improving exposure latitudes and aligning best focus through pitch by curing M3D phase effects with controlled aberrations

Cited by 16 publications

References 26 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

Hyper-NA EUV lithography: an imaging perspective

Evaluation of Lines and Spaces printing and general understanding of imaging with dark field low-n mask

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