Low-voltage aberration-corrected SEM metrology of thin resist for high-NA EUVL

Zidan, Mohamed; Fischer, Daniel; Lorusso, Gian; Severi, Joren; Simone, Danilo De; Moussa, Alain; Muellender, Angelika; Mack, Chris A.; Charley, Anne-Laure; Leray, Philippe; Gendt, Stefan De

doi:10.1117/12.2613990

Cited by 3 publications

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“…Joren Severi received funding from Fonds Wetenschappelijk Onderzoek (FWO; 1SA8919N). This manuscript has been previously published in the SPIE Conference Proceedings Volume 12053, Metrology, Inspection, and Process Control XXXVI; 120530P (2022) https://doi.org/10.1117/12.2613990 11 …”

Section: Acknowledgmentsmentioning

confidence: 99%

Role of landing energy in e-beam metrology of thin photoresist for high-numerical aperture extreme ultraviolet lithography

Zidan

Fischer

Severi

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Background: Lithography advancements require to resist layer thickness reduction, essential to cope with the low depth of focus (DOF) characteristic of high numerical aperture extreme ultraviolet lithography (HNA EUVL). However, such a requirement poses serious challenges in terms of resist process metrology and characterization, as patterns in thin resist suffer from low contrast, which may affect the performance of the edge detection algorithms used for image analysis, ultimately impacting metrology.Aim: Investigate e-beam imaging using low landing energy (LE) settings as a possible way to address the thin resist film metrology issues.Approach: A low-voltage aberration-corrected SEM developed at Carl Zeiss is to image three thin resist thicknesses and two different underlayers, at various LE and number of frames. All images are analyzed using MetroLER software, to extract the parameters of interest [mean critical dimension (CD), line width roughness (LWR), and linescan signal-to-noise ratio (SNR)] in a consistent way. Results:The results indicate that mean CD and LWR are affected by the measurement conditions, as expected. Imaging through LE unravels two opposing regimes in the mean CD estimate, the first in which the mean CD increases due to charging and the second in which the mean CD decreases due to shrinkage. Additionally, the trend between LE and linescan SNR varies depending on the stack. Conclusion:We demonstrated the ability of low-voltage aberration-corrected SEM to perform thin-resist metrology with good flexibility and acceptable performance. The LE proved to be an important knob for metrology of thin resist.

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Section: Acknowledgmentsmentioning

confidence: 99%

Role of landing energy in e-beam metrology of thin photoresist for high-numerical aperture extreme ultraviolet lithography

Zidan

Fischer

Severi

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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“…[6][7][8][9][10] In high NA EUVL, where process time reduction is strongly beneficial due to equipment costs and energy consumption and thinner resist films are advantageous to overcome the limitations imposed by the tight depth of focus (DOF), resist materials with excellent sensitivity and sufficient etch resistance are urgently required. 11,12 Responding to these demands, attempts are being made to adopt tin-oxo nanoclusters as a photoresist material, which exhibit excellent physical and chemical durability while also serving as highly-absorbing elements for EUV. 13 In addition to EUV absorption, it is desirable to devise effective reaction pathways and incorporate them into the chemical mechanisms of the resist under EUV radiation.…”

Section: Introductionmentioning

confidence: 99%

Approach for enhancing sensitivity of tin-oxo cluster resist for high NA extreme UV lithography

Ku,

Kim,

Kim

et al. 2024

Advances in Patterning Materials and Processes XLI

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High numerical aperture (NA) EUV lithography is considered as the most-promising candidate for next generation lithography protocol that will play a crucial role in meeting the demand on the enhanced semiconductor performance and productivity. While this technology enables the fabrication of sub-10 nm patterns, the increased NA has posed challenges, such as reduced depth of focus and narrower process margins. To overcome these hurdles, it is essential to apply thinner resist films while ensuring that the resulting small patterns maintain sufficient physical and chemical durability. Moreover, considering that thinner films absorb fewer photons, the resist molecular structure should be designed to compensate sensitivity burdens.Here, an approach has been proposed to enhance sensitivity by accelerating the solubility change of a well-known tinbased nanocluster resist. To accomplish this goal, it is important to increase not only the number of secondary electrons but also reaction sites and promote radical-based chemical reactions. We aimed at experimentally validating this concept by utilizing elements with high EUV absorbance and highly reactive functional groups with tin radicals. As a model resist, we chose a tin-oxo cage material consisting of a divalent cation containing 12 tin atoms and two counter anions. Our findings indicate that the introduction of unsaturated groups capable of building bridging bonds with radicals leads to fast solubility change at a lower exposure dose, thus enhancing sensitivity. This research offers a promising direction for the development of resists tailored for High NA EUV lithography.

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e-beam metrology of thin resist for high NA EUVL

Lorusso

Simone

zidan

et al. 2023

Jpn. J. Appl. Phys.

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One of the many constrains of High Numerical Aperture Extreme Ultraviolet Lithography (High NA EUVL) is related to resist thickness. In fact, a critical consequence of moving from current 0.33NA to 0.55NA (High NA) is Depth of Focus (DOF) reduction. The question we seek to answer in the present work is how the resist thickness reduction impacts the e-beam metrology needed to characterize the process. The impact of film thickness on e-beam metrology was first investigated by Critical Dimension Scanning Electron Microscope (CD SEM) using our current Best-Known Methods (BKM’s). Optimized settings minimizing such an impact were then investigated using CD SEM as well as Low Voltage SEM (LV SEM). Atomic Force Microscopy (AFM) was used to accurately characterize the samples thickness. Our results indicates that alternative operating conditions and BKM’s are sometimes needed to meet the metrology requirements. However, even in the case of materials showing a large sensitivity to resist thinning, we were able to identify e-beam imaging conditions able to meet metrology specifications.

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Low-voltage aberration-corrected SEM metrology of thin resist for high-NA EUVL

Cited by 3 publications

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Role of landing energy in e-beam metrology of thin photoresist for high-numerical aperture extreme ultraviolet lithography

Role of landing energy in e-beam metrology of thin photoresist for high-numerical aperture extreme ultraviolet lithography

Approach for enhancing sensitivity of tin-oxo cluster resist for high NA extreme UV lithography

e-beam metrology of thin resist for high NA EUVL

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