Improving aberration control with application specific optimization using computational lithography

Zhou, Jianming; Zhang, Youping; Engblom, Peter; Hyatt, Mike; Wu, Eric; Snajdr, Martin; Devilliers, Anton; He, Yuan; Hickman, Craig R.; Liu, Peng; Lang, Dennis de; Geh, Bernd; Byers, Erik; Light, Scott

doi:10.1117/12.846697

Cited by 4 publications

(5 citation statements)

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“…Sustaining of the DCO mode throughput when potential WIP impact is negligible, 2. Preparing countermeasures (Image-Tuner sub-recipe [2], DCO lot operation planning) in advance in case of WIP impact exceeding control margin, and 3. Regular monitoring of potential WIP impact.…”

Section: Discussionmentioning

confidence: 99%

Wafer in process impact simulation caused by lens calibration

Yoo¹,

Song²,

Lee³

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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As overlay requirement is getting tighter, a litho user needs to dedicate a specific scanner to print the critical layers for recent DRAM node to prevent Matched Machine Overlay (MMO) penalty. But periodic scanner maintenance is unavoidable in scanner operation over long period, and it can cause “Dedication Break”. Although lens calibration, one of the most important scanner maintenance processes, is necessary to minimize lens aberration which has drifted over time, the resulting aberration change can cause an overlay impact on the wafers in the process. This impact can be greater than normal MMO penalty. In the worst case, the user should block the wafers in process due to serious overlay impact which comes from aberration change. In order to prevent the case, users gradually reduce the flow of wafers in the dedicated mode to reach the zero dedication right before lens calibration. Then, new dedication mode can start insert after lens calibration to avoid “Wafer in Process (WIP) Impact” for all dedicated scanners. Such a manipulation can take several months resulting in loss of cost and throughput. Here, we introduce an WIP impact simulation method before lens calibration based on physical theory, ASML lens emulator and process information; pattern design, illumination pupil, dose and metrology layout. If user can define the pattern shift result for each bottom layer (before lens calibration) and top layer (after lens calibration), potential overlay WIP impact is predictable and user can selectively decide wafer and lot operation plan to minimize cost and throughput loss per scanner. In addition, user can monitor and prepare countermeasures for potential WIP impact in advance.

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Section: Discussionmentioning

confidence: 99%

Wafer in process impact simulation caused by lens calibration

Yoo¹,

Song²,

Lee³

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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“…The transmitted laser energy, though as low as a few watts, will cause unwanted thermal aberrations [1][2][3], and the nonuniform distribution of energy, for example, under dipole illumination conditions, makes it worse and more complicated [4,5]. Previous studies attributed thermal aberrations to three temperature effects: thermal deformation of lens surface, change of refractive index, and stress-birefringence [6].…”

Section: Introductionmentioning

confidence: 96%

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Chen

Yang

et al. 2013

Appl. Opt.

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Precision optical systems that utilize laser beams as working media usually suffer from thermal aberrations caused by absorbed energy. Based on a specially designed three-lens system, the causes and contributions of mechanical structures to the system's thermal aberrations are studied. The contribution of three thermal effects, surface deformation, change of refractive index, and stress birefringence on the system's thermal aberrations, is analyzed respectively through an integrated optomechanical simulation method. The impact of the structure's thermal dissipating capability and structure configuration on the system's thermal aberrations is analyzed, too. Experiments have been carried out to validate the correctness and accuracy of the simulation method. Both the simulated and tested results can provide a reference for structure design and thermal aberration analysis of the similar optical systems.

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“…However, as the reduction of wavelength and the limitation of manufacturing, the root mean square (RMS) aberration levels of EUV lithography tools are ten times higher (when normalized by wavelength) compared to those of ArF lithography tools 2 . Consequently, it is increasingly crucial to have accurate control of aberrations to ensure pattern precision in the exposure field [3][4][5] .…”

Section: Introductionmentioning

confidence: 99%

“…At present, aberration compensation and optimization are also important approaches for aberration control 3,[6][7][8][9][10] . For optical systems with circular pupil, orthogonal Zernike polynomials are commonly used to represent the influence of aberration on wavefront 11 , as shown in equation (1): 1 ( , ) ( , ),…”

Section: Introductionmentioning

confidence: 99%

“…The goal of aberration compensation, especially for thermal aberrations, is to minimize the coefficient of each Zernike term 10 . While the process of aberration optimization entails modifying the proportions of different aberrations to reduce their impact on pattern imaging 3 . The aberration compensation and optimization require a modeling process that is time-consuming 5 , mainly because of the need to account for multiple aberrations.…”

Section: Introductionmentioning

confidence: 99%

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Identification of key aberrations that affect pattern imaging in EUVL

Wang,

Su,

Wei

2024

DTCO and Computational Patterning III

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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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Improving aberration control with application specific optimization using computational lithography

Cited by 4 publications

References 0 publications

Wafer in process impact simulation caused by lens calibration

Wafer in process impact simulation caused by lens calibration

Simulated and experimental study of laser-beam-induced thermal aberrations in precision optical systems

Identification of key aberrations that affect pattern imaging in EUVL

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