EUV reticle inspection using phase retrieval algorithms: a performance comparison

Nebling, Ricarda; Mochi, Iacopo; Kazazis, Dimitrios; Locans, Uldis; Dejkameh, Atoosa; Ekinci, Yasin

doi:10.1117/12.2536936

Cited by 8 publications

(5 citation statements)

References 14 publications

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“…Fly-scan mode Unlike the conventional defect detecting step by step via die-to-die or die-to-database difference mapping based on scattering contrast microscopy method [14], in which little scanning lateral drifts may cause increased uncertainty of scattering signal, the fly-scan defect detecting tactic shows high robustness against lateral drifting. Furthermore, the principle of FDDM involves self-correlation of measured integral diffraction intensities from a fly-scan field of the sample and with no need of a priori diffraction information of defect-free die (die to die) or priori calculated diffraction of the design layout (die to database).…”

Section: Fddm Operationmentioning

confidence: 99%

High throughput defect inspection and ptychographic review for EUV mask

Chen

Zhou

et al. 2023

AOPC 2022: Optical Sensing, Imaging, and Display Technology

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We have recently developed an actinic full-field EUV patterned mask inspection and review system on a tabletop by using a coherent high-harmonic generation (HHG) Extreme Ultra-violet (EUV) source. By adopting a combination of reflective-mode fly-scan scattering detecting and scanning coherent diffraction imaging methods, the actinic defects can be sensitively detected with high throughput and precisely reviewed with a finer resolution. In this work, we propose a model of a two-step EUV mask cross-scale inspection (EMCI) tactic for fast identification of actinic defects and highresolution review of the EUV mask, which is based on difference analysis of diffracted intensities and precise ptychographic reconstruction of the EUV mask. The proposed EMCI model consists of two steps. In the first step, a flyscan diffraction difference mapping (FDDM) method is applied to recognize and localize the defects from the EUV mask with full field of view. Thus, a sub-micron resolution defect location map is generated by array to array comparison of the diffracted intensities from the line integral of scanning regions with programmed defects, to regions of defect-free. This FDDM method works particularly in Fourier domain with no need to any form of imaging system, meanwhile, scattering information takes the advantage of high sensitivity to nanoscale defects, so that defects can be recognized and localized with high throughput and robustness. In the second step, with the location information of defects by FDDM, an EUV Ptychography (EUVP) method is applied to do the local review of EUV mask by retrieving the image of both the EUV mask and illumination based on ptychography. In this manuscript, utilizing the proposed EMCI model, we have performed a numerical simulation for EUV patterned mask defect inspection and review. The results reveal the performance of the proposed model in EUV mask metrology. The proposed method is particularly expected to have a remarkable implication for the EUV lithography.

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Section: Fddm Operationmentioning

confidence: 99%

High throughput defect inspection and ptychographic review for EUV mask

Chen

Zhou

et al. 2023

AOPC 2022: Optical Sensing, Imaging, and Display Technology

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“…where 𝐼𝐼 is the intensity of the measured diffraction pattern on the detector, 𝜓𝜓 is the exit-wave and F is the Fourier transform operator. The Fourier error is summed over all pixels (𝑢𝑢, 𝑗𝑗) and averaged over the scan positions 𝑞𝑞 [7]. Using this metric, it is found that the error is reduced as a function of the exposure times.…”

Section: Reconstruction Comparisonmentioning

confidence: 99%

Resolution limit and photon flux dependency in EUV ptychography

Kim

Nebling

Dejkameh

et al. 2021

Photomask Technology 2021

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With the transition of EUV lithography to high-volume manufacturing, EUV mask metrology has become a critical requirement, and for future technology nodes, the challenges will increase. RESCAN, a lensless actinic microscope dedicated to EUV mask inspection under development, is based on coherent diffraction imaging (CDI) where the complexamplitude image of the sample is obtained through its diffraction spectra measured with a pixel detector. While this approach can overcome the disadvantages and limitations of conventional optical imaging systems, in CDI, the quality of the recorded diffraction data is crucial for the reliable reconstruction of a high-resolution image. Ultimately, the signal-tonoise ratio of the recorded diffraction data depends on several parameters, such as the reflectance of the sample, the quantum efficiency of the detector, its full well capacity, and the intensity of the illumination. This paper investigates the optimal photon flux for RESCAN and analyzes the relation between the image quality and the EUV illumination intensity for a CDI-based imaging tool dedicated to EUV mask inspection and review.

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“…In the present study, we use the difference map (DM), which is a phase retrieval algorithm frequently used in ptychography [13]. Compared to the other algorithms, the DM method is a relatively robust reconstruction method against image noise and probe positions errors [12]. In this paper, we keep the parameters the same in the DM algorithm for an exact comparison and see the impact of the newly added correction algorithm explained in the following Section.…”

Section: Difference Map (Dm) Reconstructionmentioning

confidence: 99%

“…Accordingly, RESCAN uses a diffraction recording detector and reconstruction algorithm instead of lenses to obtain the aerial image of the EUV mask. We also implement and develop the algorithm by considering various ptychography approaches to optimize the reconstruction speed and accuracy [12]. Ptychography is a scanning CDI technique that allows for the reconstruction of large field objects.…”

Section: Introductionmentioning

confidence: 99%