EUV mask cleans comparison of frontside and dual-sided concurrent cleaning

Cheong, Lin Lee; Kindt, Louis; Turley, Christina; Leonhard, Dusty; Boyle, John M.; Robinson, Chris; Rankin, Jed; Corliss, Daniel

doi:10.1117/12.2085913

Cited by 4 publications

(3 citation statements)

References 2 publications

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“…Another important aspect of a prospective absorber is to withstand the cleaning conditions. EUV masks are expected to withstand more than 100 cleaning cycles with little to no influence on lithographic performance 27 . To assess the durability of Ta-Co alloys, sample coupons of 2 cm×2 cm of each composition were submerged separately for 24 hrs in the beakers containing the solution.…”

Section: Methodsmentioning

confidence: 99%

“…EUV masks are expected to withstand more than 100 cleaning cycles with little to no influence on lithographic performance. 27 To assess the durability of Ta-Co alloys, sample coupons of 2 cm × 2 cm of each composition were submerged separately for 24 hrs in the beakers containing the solution. The stability of these materials was studied in mask cleaning solutions with a wide range of pH, viz., DIW (de-ionized water, pH 5.7), 1% NH 4 OH (ammonium hydroxide, pH 11.4), and 0.2% to 0.5% TMAH (tetramethylammonium hydroxide, pH 12.8).…”

Section: Cleaning and Durability Testmentioning

confidence: 99%

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

Thakare

Opsomer

et al. 2023

J. Micro/Nanopattern. Mats. Metro.

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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.

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Section: Methodsmentioning

confidence: 99%

Section: Cleaning and Durability Testmentioning

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

show abstract

“…Wet clean and cryogenic clean processes can efficiently remove numerous particle contaminants which are loosely bound to the mask surface; however, individual strongly bonded particles can be missed. 2 In the initial mask writing, pattern shifting can compensate for most of these contaminants, but this method is of no use in the longer-term use and maintenance of these masks. It has been observed by the authors that the higher energy levels seen in the steppers has resulted in more contaminants as adherent to the mask surfaces as the absorber stack.…”

Section: Introductionmentioning

confidence: 99%