Lensless metrology for semiconductor lithography at EUV

Mochi, Iacopo; Kazazis, Dimitrios; Tseng, Li‐Ting; Fernandez, Sylvie; Rajeev, Rajendran; Locans, Uldis; Dejkameh, Atoosa; Nebling, Ricarda; Ekinci, Yasin

doi:10.1117/12.2534350

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…Accurate imaging of the extreme ultraviolet (EUV) mask is essential in EUV lithography. At Paul Scherrer Institute (PSI), we are developing RESCAN (Reflection-mode EUV SCANning microscope), a ptychography-based microscope dedicated to actinic patterned mask inspection (APMI) [1][2][3][4]. It is a synchrotron-based platform installed at the XIL-II beamline of the Swiss Light Source (SLS).…”

Section: Introduction and Methodsmentioning

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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Section: Introduction and Methodsmentioning

confidence: 99%

Resolution limit and photon flux dependency in EUV ptychography

Kim

Nebling

Dejkameh

et al. 2021

Photomask Technology 2021

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“…The sample used for this experiment is a programmed defect mask used to test RESCAN's resolution limit. 12 We reconstructed the a low-resolution image of the mask from each dataset as shown in the examples in Figure 6 and we used Fourier ptychography to synthsize the high resolution image in Figure 7.…”

Section: Fourier Synthesis Image Reconstructionmentioning

confidence: 99%

Resolution enhancement for lensless mask metrology with RESCAN

Mochi

Locans

Dejkameh

et al. 2019

International Conference on Extreme Ultraviolet Lithography 2019

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The EUV photomask is a key component of the lithography process for semiconductor manufacturing. A critical defect on the mask could be replicated on several wafers, causing a significant production yield reduction. For this reason, actinic patterned mask inspection is an important metrology component for EUV lithography. The RESCAN microscope is a lensless imaging platform dedicated to EUV mask defect inspection and metrology. The resolution of the tool is about 35 nm, which is similar to that of state-of-the-art EUV microscopes. To improve the resolution of RESCAN, we designed an upgraded optical layout for the illumination system and we developed a coherent diffraction imaging-compatible method to synthesize a custom pupil structure. This new scheme will enable a lensless EUV microscope with a resolution down to 20 nm and thereby allow mask review capabilities for future technology nodes with EUV lithography.

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“…RESCAN can inspect EUV photomask samples with an effective resolution of 50 nm (on the mask) and with a defect sensitivity down to 20 nm. 8,9 While the commercial inspection tools can detect and locate the mask defects with high resolution, they are not able to distinguish the defect material. Therefore, we explore the possibility of using RESCAN to distinguish the defect material by comparing the image contrast in both amplitude and phase images.…”

Section: Introductionmentioning

confidence: 99%

EUV mask defect material characterization through actinic lensless imaging

Shen

Kazazis

Kim

et al. 2022

Metrology, Inspection, and Process Control XXXVI

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The reflective-mode EUV mask scanning lensless imaging microscope (RESCAN) is a synchrotron-based platform dedicated to EUV mask inspection and review at the Swiss Light Source. It is based on coherent diffraction imaging (CDI), which allows retrieving both the phase and the amplitude information of the mask surface. RESCAN has been successfully tested on masks with programmed phase and amplitude defects. A metrology method that can not only detect defects and contamination, but can also determine the material of the defects, can be a powerful tool to help identify the root cause of the defects. Here, we explore the possibility of leveraging the ability of RESCAN to detect the complex amplitude of the sample to distinguish surface defects of different materials. We fabricated a sample with random logic-like absorber patterns and pillar defects on top of a Mo/Si multilayer. We show our experimental results that show the defects of different materials exhibit specific contrast and phase values. This method can be used not only to detect the masks defects but also to identify the defect materials to a limited extent.

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Lensless metrology for semiconductor lithography at EUV

Cited by 5 publications

References 18 publications

Resolution limit and photon flux dependency in EUV ptychography

Resolution limit and photon flux dependency in EUV ptychography

Resolution enhancement for lensless mask metrology with RESCAN

EUV mask defect material characterization through actinic lensless imaging

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