Aberration budget analysis of EUV lithography from the imaging performance of a contact layer in a 5  nm technology node

In EUVL, aberrations play a crucial role in critical dimension (CD) and pattern shift (PS) errors. It is significant to decide aberration compensation and optimization strategies for compensating exposure errors. The modeling process of aberration is time-consuming, mainly because of the need to consider numerous aberrations. In order to save the runtime for aberration modeling, this paper proposes a methodology for identifying the key aberrations that have significant impacts on imaging results. Three different techniques are employed and compared, including single parameter sensitivity analysis, definitive screening design (DSD) method, and SOBOL method that consider the coupling effects of different orders. By comparing the deviations between the imaging results considering only key aberrations and all aberrations, it is found that the identified aberrations achieve extremely high accuracy for various patterns and illumination conditions. Even though the proportion of key aberrations among all aberrations is only a small fraction. All the three methods can achieve that the average CD and PS deviations do not surpass 1%, using 40% of the total 37 aberration items. Thereby, the feasibility of using identified key aberrations for aberration modeling is validated. In addition, we also compare the accuracies of three techniques under the same conditions and found that the SOBOL method is the most suitable technique for identifying key aberrations. Consequently, for specific illumination conditions and corresponding layout patterns, the use of key aberrations is an effective way to characterize the impacts of all 37 aberrations, accelerating the aberration compensation and optimization without sacrificing accuracy.

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The impact of aberrations in extreme ultraviolet lithography systems on exposure results

Wang,

Li,

et al. 2024

International Conference on Extreme Ultraviolet Lithography 2024

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Extreme ultraviolet (EUV) lithography is one of the essential technologies for the 5nm and below technology nodes. However, the presence of aberrations in the system severely affects the exposure results, which can lead to wafer rework and increase costs. In order to investigate the impact of aberrations in EUV lithography systems on exposure results, this paper conducts research on the impact of aberrations on exposure results of patterns that commonly used in EUV singleexposure for the 5nm technology node. A large number of aberration experiments are performed, and the distribution of critical dimension (CD), normalized image log-slope (NILS), Pattern Shift (PS), and process variation band (PVB) of exposure results in relation to all Zernike terms variation within ±50mλ is statistically analyzed. We find that aberrations lead to worse exposure results generally, and the distribution of results does not strictly follow a Gaussian distribution but exhibits significant "tail" phenomena. And the impact of aberrations varies for different patterns. Furthermore, the relationship between the distribution of exposure results and the magnitude of aberrations are investigated. It is observed that as the aberration RMS increases, the probability of deteriorated exposure results also increases. Spherical aberration has a significant impact on CD and PVB, while x-direction coma has a significant impact on the PS of vertical line-space patterns, and y-direction coma has a significant impact on the PS of vertical tip to tip patterns. X-direction astigmatism has a higher probability of causing positive PS, while y-direction astigmatism has a higher probability of causing negative PS. Relatively speaking, the effects of 3-foil, 4-foil, and 5-foil aberrations are smaller. This paper provides a clear reference for the influence of various aberrations on exposure results and can contribute to the future development and aberration control of lithography systems.

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Aberration budget analysis of EUV lithography from the imaging performance of a contact layer in a 5 nm technology node

Cited by 4 publications

References 26 publications

Surface asymmetry measurements by single-shot cyclic azimuthal shearing interferometry

Surface asymmetry measurements by single-shot cyclic azimuthal shearing interferometry

Identification of key aberrations that affect pattern imaging in EUVL

The impact of aberrations in extreme ultraviolet lithography systems on exposure results

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