Enhancing defect detection with Zernike phase contrast in EUV multilayer blank inspection

Wang, Yow-Gwo; Miyakawa, Ryan; Chao, Weilun; Benk, Markus P.; Wojdyla, Antoine; Donoghue, Alex; Johnson, David G.; Goldberg, Kenneth A.; Neureuther, A. R.; Liang, Ted; Naulleau, Patrick

doi:10.1117/12.2087532

Cited by 9 publications

(6 citation statements)

References 6 publications

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“…The consideration of various demagnifications and pupil aspect ratios, and illumination patterns can be used to guide progress in this area without extensive modifications that all-reflective actinic mask-imaging microscopes could require. 8 Figures Fig. 1 Visual comparison of a large defect, 13 imaged with (a) mask-SEM, (b) SHARP EUV mask microscope, and (c) wafer-SEM.…”

Section: Discussionmentioning

confidence: 99%

“…SHARP is a synchrotron-based, actinic, EUV mask microscope, located at a bending-magnet beamline at the Advanced Light Source at Lawrence Berkeley National Laboratory. Since its commissioning in 2013, SHARP has contributed to many aspects of EUV mask technology, including defects, 7 their detection 8 and printability, 9 repairs, 10 substrate roughness, 10 impact of non-telecentricity 11 and multilayer properties. 12 An overview of SHARP can be found in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Emulation of anamorphic imaging on the SHARP extreme ultraviolet mask microscope

Benk

Wojdyla

Chao

et al. 2016

J. Micro/Nanolith. MEMS MOEMS

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Abstract. The SHARP High numerical aperture Actinic Reticle review Project is a synchrotron-based, extreme ultraviolet (EUV) microscope dedicated to photomask research. SHARP emulates the illumination and imaging conditions of current EUV lithography scanners and several generations into the future. An anamorphic imaging optic with increased mask-side numerical aperture (NA) in the horizontal and increased demagnification in the vertical direction has been proposed to overcome limitations of current multilayer coatings and extend EUV lithography beyond 0.33 NA. Zoneplate lenses with an anamorphic 4x/8x NA of 0.55 are fabricated and installed in the SHARP microscope to emulate anamorphic imaging. SHARP's Fourier synthesis illuminator with a range of angles exceeding the collected solid angle of the newly designed elliptical zoneplates can produce arbitrary angular source spectra, matched to anamorphic imaging. A target with anamorphic dense features down to 50-nm critical dimension is fabricated using 40-nm of nickel as the absorber. In a demonstration experiment anamorphic imaging at 0.55 4x/8x NA and 6º central ray angle (CRA) is compared to conventional imaging at 0.5 4x NA and 8º CRA. A significant contrast loss in horizontal features is observed in the conventional images. The anamorphic images show the same image quality in the horizontal and vertical directions.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Emulation of anamorphic imaging on the SHARP extreme ultraviolet mask microscope

Benk

Wojdyla

Chao

et al. 2016

J. Micro/Nanolith. MEMS MOEMS

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“…These programmed defects have previously been studied using various techniques. [7][8][9] They consist of squares of fixed height and varied width patterned onto the substrate before multilayer deposition. We imaged the defects using σ = 0.25 monopole illumination, an NA of 0.0825, and wavelength of 13.5 nm.…”

Section: Amplitude and Phase Defectsmentioning

confidence: 99%

Phase measurements of EUV mask defects

et al. 2015

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“…To identify phase-dominated multilayer defects on EUV mask blanks, ZPC and DF inspection tools have both been studied and demonstrated [2,3]. Results show the capability to have high defect sensitivity on critical defects for advanced technology nodes.…”

Section: Introductionmentioning

confidence: 99%

Enhancing native defect sensitivity for EUV actinic blank inspection: optimized pupil engineering and photon noise study

2016

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In this paper, we discuss the impact of optimized pupil engineering and photon noise on native defect sensitivity in EUV actinic blank inspection. Native defects include phase-dominated defects, absorber defects, and defects with a combination of phase and absorption behavior. First, we extend the idea of the Zernike phase contrast (ZPC) method and study the impact of optimum phase shift in the pupil plane on native defect sensitivity, showing a 23% signal-to-noise ratio (SNR) enhancement compare to bright field (BF) for a phase defect with 20% absorption. We also describe the possibility to increase target defect SNR on target defect sizes at the price of losing the sensitivity on smaller (noncritical) defects. Moreover, we show the advantage of the optimized phase contrast (OZPC) method over BF EUV actinic blank inspection. A single focus scan from OZPC has better inspection efficiency over BF. Second, we make a detailed comparison between the phase contrast with apodization (AZPC) method and dark field (DF) method based on defect sensitivity in the presence of both photon shot noise and camera noise. Performance is compared for a variety of photon levels, mask roughness conditions, and combinations of defect phase and absorption.

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Enhancing defect detection with Zernike phase contrast in EUV multilayer blank inspection

Cited by 9 publications

References 6 publications

Emulation of anamorphic imaging on the SHARP extreme ultraviolet mask microscope

Emulation of anamorphic imaging on the SHARP extreme ultraviolet mask microscope

Phase measurements of EUV mask defects

Enhancing native defect sensitivity for EUV actinic blank inspection: optimized pupil engineering and photon noise study

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