Performance in practical use of actinic EUVL mask blank inspection

Yamane, Takeshi; Kim, Yong‐Dae; Takagi, Noriaki; Terasawa, Tsuneo; Ino, Tomohisa; Suzuki, Tomohiro; Miyai, Hiroki; Takehisa, Kiwamu; Kusunose, Haruhiko

doi:10.1117/12.2067566

Cited by 5 publications

(2 citation statements)

References 11 publications

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“…A summing up of 2 × 2 pixel (924 × 924 nm at the EUV blank plane) intensities that included the phase defects were defined as DSI values. Yamane et al 29 reported that the 924 × 924-nm area seemed to be too large to calculate the DSI because the multilayer itself has its own roughness, and the EUV light scattered by the roughness is also captured by the Schwarzschild optics. Then to reduce the influence of the surface roughness of the multilayer on the DSI analysis, the images of each phase defect were acquired by using the 1200× review optics with an exposure time of 2 s. The DSI values were calculated by integrating the pixel intensities above the back-ground level of the acquired images.…”

Section: Influence Of the Defect Volume On The Defect Signal Intensitymentioning

confidence: 99%

Phase defect detection signal analysis: dependence of defect size variation

Amano¹,

Watanabe²,

Abe

2015

J. Micro/Nanolith. MEMS MOEMS

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Abstract. The influence of the size or volume of the phase defect embedded in the extreme ultraviolet mask on wafer printability by scanning probe microscope (SPM) is well studied. However, only a few experimental results on the measurement accuracy of the phase defect size have been reported. Therefore, in this study, the measurement repeatability of the phase defect volume using SPM and the influence of the defect volume distribution on defect detection signal intensity (DSI) using an at-wavelength dark-field defect inspection tool were examined. A programmed phase defect mask was prepared, and a defect size measurement repeatability test was conducted using an SPM. As a result, the variation of the measured volume due to the measurement repeatability was much smaller than that of the defect-to-defect variation. This result indicates that measuring the volume of each phase defect is necessary in order to evaluate the defect detection yield using a phase defect inspection tool and wafer printability. In addition, the images of phase defects were captured using an at-wavelength dark-field inspection tool from which the defect DSIs were calculated. The DSI showed a direct correlation with the defect volume. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Influence Of the Defect Volume On The Defect Signal Intensitymentioning

confidence: 99%

Phase defect detection signal analysis: dependence of defect size variation

Amano¹,

Watanabe²,

Abe

2015

J. Micro/Nanolith. MEMS MOEMS

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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: 98%

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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Variation in phase defect size on extreme ultraviolet mask before and after reflective multilayer coating

Amano¹,

Abe

2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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It is very difficult to predict how multilayer defects known as “phase defects” impact on wafer printed image when embedded in an extreme ultraviolet (EUV) mask. Therefore, researchers have reported many techniques to analyze and characterize phase defects using scanning probe microscopes (SPMs) and phase defect inspection tools that employ deep ultraviolet or EUV optics. To characterize the phase defects using SPM or other inspection tools, preparing and employing a programmed phase defect mask is a practical way to address the task because the locations, sizes, and quantity of phase defects can be defined to fit experiments. For this study, a programmed phase defect mask was prepared to investigate the size uniformity of the programmed phase defects. The designed phase defects were holes 40-, 50-, 70-, or 80-nm-wide and 4.5-nm-deep. Using a SPM, the phase defects were measured for their depths and widths before and after coating with the multilayer. As a result, variations in the measured depths and widths were much smaller than the defect-to-defect variations, reflecting measurement repeatability. In addition, the variations in the depths and widths of the phase defects after multilayer coating were larger than before coating. It was also found that a given group of phase defects exhibited significant variations in depth and width after multilayer coating, even if they were the same prior to coating. This result indicated that it is difficult to estimate precoating phase defect sizes based on measurements after the multilayer is coated.

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Performance in practical use of actinic EUVL mask blank inspection

Cited by 5 publications

References 11 publications

Phase defect detection signal analysis: dependence of defect size variation

Phase defect detection signal analysis: dependence of defect size variation

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

Variation in phase defect size on extreme ultraviolet mask before and after reflective multilayer coating

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