Mask absorber for next generation EUV lithography

Wu, Meiyi; Thakare, Devesh; Marneffe, Jean‐François de; Jaenen, Patrick; Souriau, Laurent; Opsomer, Karl; Soulié, Jean-Philippe; Erdmann, Andreas; Mesilhy, Hazem; Naujok, Philipp; Foltin, Markus; Soltwisch, Victor; Saadeh, Qais; Philipsen, Vicky

doi:10.1117/12.2572114

Cited by 4 publications

(6 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other authors, e.g., [2,5], have described opportunities to use new EUV mask absorbers. These new absorbers can be thinner than current absorbers and therefore reduce undesired mask shadowing and topography effects.…”

Section: Mask Film Stack Effects In High-na Euvmentioning

confidence: 99%

“…Some key new process differences expected for high-NA EUV are shown in Figure 1. These include: a) Anamorphic optics and flare b) Central obscuration of the projection lens c) New (generally thinner) low-n and high-K mask absorber stacks, e.g., [2] d) Differences in mask rule (MRC) limits between horizontal and vertical directions during OPC/ILT e) Potential need for field to field pattern stitching to achieve chip sizes larger than 26x16mm or to achieve optimal scanner field utilization for certain chip dimensions f) Tatian aberration basis used for describing lens aberrations…”

Section: Introductionmentioning

confidence: 99%

“…The reference mask absorber was a production proven TaN absorber. New absorbers tested were Pt2Mo, TaTeN and Ru3Re [2]. The assumed n,k and thickness of these new absorbers are shown in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Process optimization for next generation high-NA EUV patterning by computational lithography techniques

Levinson

Dam

Kareem³

et al. 2023

Optical and EUV Nanolithography XXXVI

View full text Add to dashboard Cite

The lithography industry has historically striven to improve resolution by reducing wavelength and increasing the lens’ numerical aperture (NA). The introduction of 0.33 NA extreme ultraviolet (EUV) lithography into high-volume manufacturing (HVM) represents the largest jump in resolution ever achieved by the industry. However, even this resolution is not sufficient for the patterns required for beyond the 2 nm logic technology node. This is due to low contrast and the diffraction limit of current EUVL scanners for the mask patterns required for these nodes. Instead, the resolution must be improved by increasing the NA. This will also increase the contrast of patterns which had insufficient contrast at 0.33 NA, which will in turn improve LCDU and defectivity. This change is not without its challenges though. Increasing the NA from 0.33 to 0.55 will cause a significant reduction in depth of focus. In addition, stronger mask 3D effects can cause pattern dependent shifts in best focus. As a result, the common overlapping process window of several critical patterns can become strongly diminished. The use of anamorphic optics will require two separate half-field exposures to obtain the equivalent of a single full-field exposure on current EUV and DUV scanners. For some chip sizes, this will require stitching two half-fields together to pattern the full chip area. In previous technology nodes, the process window could be improved using SMO and SRAFs. In addition, over the last five years, the industry has put significant effort into studying alternative absorbing materials. These materials can significantly reduce the mask 3D effects by reducing the thickness of the absorber. The use of alternative absorbers alone will not be sufficient for improving the overlapping process window. Instead, several techniques must be simultaneously utilized in order to ensure sufficient overall process window. Optimization of overlapping process windows is critical for successful insertion of high-NA EUVL into HVM. In this paper we analyze how the process window of critical patterns can be optimized by using different optimizations. We will show for realistic mask designs how process window can be improved in different process steps. Double exposure from half-field stitching will also be included in the process evaluation. We use both rigorous and compact modeling in a complimentary fashion for overall process optimization analysis. All techniques presented in this paper accurately model the anamorphic, centrally obscured optics of the upcoming next-generation high-NA scanners.

show abstract

Section: Mask Film Stack Effects In High-na Euvmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Process optimization for next generation high-NA EUV patterning by computational lithography techniques

Levinson

Dam

Kareem³

et al. 2023

Optical and EUV Nanolithography XXXVI

View full text Add to dashboard Cite

show abstract

“…3,6 Alloying enables modification of the optical properties, as well as the morphology, crystallinity, and stability, to meet the desired specifications of novel EUVabsorbers. 3,7 Ta's familiarity with the mask ecosystem makes it appealing to investigate Ta alloys. Single-layer Co has been previously investigated as a prospective EUV mask absorber.…”

Section: Introductionmentioning

confidence: 99%

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

Thakare

Opsomer

et al. 2023

J. Micro/Nanopattern. Mats. Metro.

View full text Add to dashboard Cite

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.

show abstract

“…Alloying enables to modify the optical properties viz. n and k, as well as the morphology crystallinity and stability to meet the desired specifications of novel EUV absorbers [3], [6]. Ta's familiarity with the mask eco-system makes it appealing to investigate Ta alloys.…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

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.

show abstract

Mask absorber for next generation EUV lithography

Cited by 4 publications

References 14 publications

Process optimization for next generation high-NA EUV patterning by computational lithography techniques

Process optimization for next generation high-NA EUV patterning by computational lithography techniques

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

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

Contact Info

Product

Resources

About