Contribution of mask roughness in stochasticity of high-NA EUV imaging

Jonckheere, R.; Melvin, Lawrence S.

doi:10.1117/12.2601897

Cited by 9 publications

(23 citation statements)

References 8 publications

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“…This section summarizes the findings of this mask roughness impact simulation study. The study extends MLR impact from 1D patterns used in the earlier studies 5 to an emulated metal layer 2D pattern in the present one. It was previously shown that an alternative mask deficiency analysis technique based on pupilgram light amplitude distribution allows for analysis of tolerable mask roughness, without using time consuming stochastic simulations, for the 1D case.…”

Section: Discussionsupporting

confidence: 70%

“…The first two rows are adopted from previous work. 5 In the second row of Fig. 14 the MLR L c is fixed at 20 nm and rms is varied.…”

Section: Multilayer Ripple Stochastic Wafer Defectivity Impactmentioning

confidence: 99%

“…The T R calculation is a substantial runtime reduction versus the brute force stochastic analysis of a mask deficiency. 5 To use T R , a threshold for mask deficiencies must be calculated. For the 1D case, the T R threshold was calculated at 0.015, which corresponds to a level below which the 1D CD variation is < AE 5%.…”

Section: Roughness Threshold Developmentmentioning

confidence: 99%

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Wafer level response to mask deficiencies in 0.55-numerical aperture extreme ultraviolet photolithography

Melvin

Jonckheere

2022

J. Micro/Nanopattern. Mats. Metro.

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Background: This study investigates the impact of 0.55-numerical aperture (NA) imaging on wafer defectivity when multilayer ripple is present in the extreme ultraviolet (EUV) mask.Aim: We investigate the impact of 0.55-NA anamorphic imaging on one-dimensional (1D) and two-dimensional (2D) horizontal and vertical mask feature deficiencies on wafer defectivity. The information in the study is intended to guide experimentation to aid in setting standards for EUV mask blanks in 0.55-NA lithography.Approach: This study stochastically simulated 1D and 2D horizontal and vertical features using an extreme ultraviolet mask with varied random multilayer ripple configurations. The photoresist critical dimension (CD) was measured from the simulated wafer and used to generate statistical analysis of the simulation.Results: Horizontal 1D features show an ∼2.5× improvement in failure ratio versus vertical 1D features. Vertical 2D features appear to have a lower failure ratio compared with 2D horizontal features, but the difference is not as clear as found in the 1D case. The light scattered from the leaf shaped illuminator into the pupil background region due to multilayer ripple from 2D features appears smaller than in the 1D case. Potentially mask deficient structures may benefit from orientating the CD vertically on an anamorphic system to reduce wafer level defectivity.Conclusions: There appears to be a multilayer ripple saturation level for 1D and 2D features at which defectivity and CD variation become constant. Horizontal imaging appears to be preferable for all CDs. The roughness threshold computational shortcut to mask deficiency characterization may not be sufficient for 2D features. The 2D analysis in this study does not change previous mask standard suggestions.

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Section: Discussionsupporting

confidence: 70%

“…The first two rows are adopted from previous work. 5 In the second row of Fig. 14 the MLR L c is fixed at 20 nm and rms is varied.…”

Section: Multilayer Ripple Stochastic Wafer Defectivity Impactmentioning

confidence: 99%

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Wafer level response to mask deficiencies in 0.55-numerical aperture extreme ultraviolet photolithography

Melvin

Jonckheere

2022

J. Micro/Nanopattern. Mats. Metro.

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“…This incurs a spread in printed CD among multiple stochastic simulations, representing multiple dice on a given wafer. Both CD variability, expressed as a 3-sigma, and failure probability, in case failures already do occur in a given set of repeated stochastic simulations, scale with the local printed CD, as shown in a first specific analysis of roughness type NLMDs 4 .…”

Section: Introduction: Intent Earlier Work and Applied Methodologymentioning

confidence: 88%

“…Interestingly, the CD variability (and failure probability) could be related to the impact of MLR in the pupil of the projection optics 4 . Apart from the overlapping zero and first diffraction orders for the lines-and-spaces pattern images with a leaf shape dipole source, background intensity could be ascribed to MLR of the mask.…”

Section: Summary Of Earlier Resultsmentioning

confidence: 99%

Does high-NA EUV require tighter mask roughness specifications: a simulation study

Jonckheere

Melvin²

2022

International Conference on Extreme Ultraviolet Lithography 2022

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In follow-up of related contributions at the past three symposium editions, our simulation study arrived at this question. As shown before, (local) mask defects and non-local mask deficiencies (NLMDs) act as triggers for increased stochastic failure probability on the EUV imaged resist pattern on wafer. Mask roughness is such an NLMD. The three types studied comprise multilayer (ML) ripple, which relates to a non-fully planar coating of the ML mask stack, mask absorber lineedge roughness and roughening of the ML. For the latter the study was restricted to roughening of the ruthenium capping layer only, which may already happen during the patterning step of the absorber during mask making. Each of the 3 roughness types is studied standalone and in combination. An alternative technique is presented that allows to define tolerance limits for mask roughness, without requiring massive, time-consuming stochastic simulations. It is based on studying how roughness-induced background light is passing through the projection optics. Our results, for anamorphic imaging at 0.55 NA, suggest the importance of limiting mask roughness beyond state-of-the-art.

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Elucidating the role of imaging metrics for variability and after etch defectivity

Franke

Frommhold

Dauendorffer

et al. 2022

J. Micro/Nanopattern. Mats. Metro.

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Contribution of mask roughness in stochasticity of high-NA EUV imaging

Cited by 9 publications

References 8 publications

Wafer level response to mask deficiencies in 0.55-numerical aperture extreme ultraviolet photolithography

Wafer level response to mask deficiencies in 0.55-numerical aperture extreme ultraviolet photolithography

Does high-NA EUV require tighter mask roughness specifications: a simulation study

Elucidating the role of imaging metrics for variability and after etch defectivity

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