Pattern Displacement Induced by Lens Aberrations

Hendrickx, Eric; Vandenberghe, Geert; Ronse, Kurt G.; Colina, Albert; Hoff, Alex van der; Dusa, Mircea V.; Finders, Jo

doi:10.1117/12.467912

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…In Fig. 1(c), the third-order xcoma-induced IPE is well linearly related with third-order x-coma Z 7 when the aberration level is low enough [12]. The slope of the line indicates the Alt-PSM mark's sensitivity to Z 7 .…”

Section: Introductionmentioning

confidence: 76%

Coma measurement by use of an alternating phase-shifting mask mark with a specific phase width

et al. 2009

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The correlation between the coma sensitivity of the alternating phase-shifting mask (Alt-PSM) mark and the mark's structure is studied based on the Hopkins theory of partially coherent imaging and positive resist optical lithography (PROLITH) simulation. It is found that an optimized Alt-PSM mark with its phase width being two-thirds its pitch has a higher sensitivity to coma than Alt-PSM marks with the same pitch and the different phase widths. The pitch of the Alt-PSM mark is also optimized by PROLITH simulation, and the structure of p ¼ 1:92λ=NA and pw ¼ 2p=3 proves to be with the highest sensitivity. The optimized Alt-PSM mark is used as a measurement mark to retrieve coma aberration from the projection optics in lithographic tools. In comparison with an ordinary Alt-PSM mark with its phase width being a half its pitch, the measurement accuracies of Z 7 and Z 14 apparently increase.

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Section: Introductionmentioning

confidence: 76%

Coma measurement by use of an alternating phase-shifting mask mark with a specific phase width

et al. 2009

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“…5,6 Moreover, since the aberrations vary through the scanner slit, a given pattern will show different image placement errors in different slit positions. Limited experimental studies on image placement error, using an optical overlay tool 7 and critical dimension-scanning electron microscopy ͑CD-SEM͒ for metrology, 8,9 have been reported. Image placement error can be used as a metric for tool-to-tool matching in a process environment to minimize the intrafield overlay of different product layers.…”

Section: Introductionmentioning

confidence: 99%

Image placement error: closing the gap between overlay and imaging

Hendrickx

Colina

Hoff

et al. 2005

J. Micro/Nanolith. MEMS MOEMS

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We perform experimental and theoretical studies of image placement error induced by aberrations of the projection lens. The goal is to experimentally determine the magnitude of the image placement errors, to compare experiments and simulations, and to screen possible correction strategies. The calculations and experiments are done for ArF lithography. Theoretically, we simulate image placement error using the projection lens aberration data and simulators such as Prolith or Solid-C. Features with low and high sensitivities to lens aberrations are identified, together with a reference feature that has low sensitivity for image placement error. Dedicated reticles are fabricated to print various features at different illumination conditions on the same substrate. The resulting patterns could be analyzed using top-down scanning electron microscopy ͑SEM͒, but also optically with the standard optical overlay tool KLA5200. For both techniques, the experimentally found image placement errors are in excellent agreement with simulations. In simulations, we calculate the dependency of the image placement error on pattern density, pattern orientation, and illumination conditions. These tendencies are experimentally reproduced. We conclude with a case study that demonstrates a possible correction strategy for image placement error.

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“…First, it can cause Image Placement Error (IPE), which leads to overlay errors. Second, it can cause line-width asymmetry, which degrades the Critical Dimension (CD) uniformity (1)(2)(3)(4)(5)(6). In order to correct coma effectively, it is necessary to establish a fast and accurate in situ measurement technique for retrieving coma of projection optics.…”

Section: Introductionmentioning

confidence: 99%

High-Accuracy Measurement of Coma with the Optimized Alternating Phase-shifting Mask with a Specific Phase Width

et al. 2009

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The correlation between the coma sensitivity of the Alternating Phase-Shifting Mask (Alt-PSM) and the Alt-PSM's structure is studied. It is found that an optimized Alt-PSM whose phase width is two thirds of its pitch has a higher sensitivity to coma than Alt-PSMs with the same pitch and the different phase widths, when the pitch of the Alt-PSM makes only 1 ± and 3 ± orders diffraction light enter the lens pupil. The optimized Alt-PSM is used as a measurement mark to retrieve coma aberration from the projection optics in lithographic tools. In comparison with an ordinary Alt-PSM mark whose phase width is one half of its pitch, the measurement accuracies of 7 Z and 14 Z have increased by 15% and 31% respectively. IntroductionThe projection lens system is one of the most important systems in a lithography tool. The coma aberration of the projection lens can lead to two kinds of image quality degradations. First, it can cause Image Placement Error (IPE), which leads to overlay errors. Second, it can cause line-width asymmetry, which degrades the Critical Dimension (CD) uniformity (1-6). In order to correct coma effectively, it is necessary to establish a fast and accurate in situ measurement technique for retrieving coma of projection optics. As the CD decreases, especially with the use of resolution enhancement techniques, coma measurement techniques with higher accuracy are needed. In the lowk 1 lithography process, for the high NA projection optics, its residual wavefront aberrations, including coma, have decreased to 10 mλ or less, and it is necessary to measure wavefront aberration on the exposure tool with an accuracy of 2mλ (5).TAMIS (TIS at Multiple Illumination Settings) technique has been developed to measure wavefront aberrations (6). To determine the wavefront aberration, the aerial image of a binary mark is directly measured in this technique. Its measurement accuracy of coma reaches 2nm for ArF lithography tools. The measurement accuracy is determined by the measurement mark's sensitivity to coma. We have used an Alt-PSM as the measurement ECS Transactions, 18 (1) 381-390 (2009) 10.1149/1.3096475 © The Electrochemical Society 381 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.112.180.26 Downloaded on 2015-07-20 to IPmark instead of the binary mark to improve the measurement mark's sensitivity to aberrations and the accuracy of the TAMIS method (1). However, the correlation between the sensitivity to coma and the structure of the measurement mark has been ignored by us. The ordinary Alt-PSM whose phase width (pw) is one half of its pitch (p) has been used as the measurement mark. The pitch and phase width of the mark have not been optimized to attain the highest sensitivity. In this paper, using the lithographic simulator PROLITH, we study the influence of the Alt-PSM's structure on its sensitivity to coma, and optimize the structure to get the highest sensitivity. Then the simulation results are discussed analytically. A...

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Pattern Displacement Induced by Lens Aberrations

Cited by 3 publications

References 2 publications

Coma measurement by use of an alternating phase-shifting mask mark with a specific phase width

Coma measurement by use of an alternating phase-shifting mask mark with a specific phase width

Image placement error: closing the gap between overlay and imaging

High-Accuracy Measurement of Coma with the Optimized Alternating Phase-shifting Mask with a Specific Phase Width

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