Phase measurements of EUV mask defects

Claus, Rene A.; Wang, Yow-Gwo; Wojdyla, Antoine; Benk, Markus P.; Goldberg, Kenneth A.; Neureuther, Andrew R.; Naulleau, Patrick; Waller, Laura

doi:10.1117/12.2087195

Cited by 3 publications

(5 citation statements)

References 9 publications

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“…Although for convenience we often separately consider phase and absorber defects, in reality true defects are almost always a combination of the two types under inspection [4,5]. To address this fact, we consider the effectiveness of the Zernike phase contrast method in the presence of such real world "blended" defects.…”

Section: Defect Characteristics: Pure Phase To Attenuated Phase Defectmentioning

confidence: 98%

“…For this test we consider a native defect found on the mask with an effective size of 1.23 nm × 120 nm. The effective size was extracted using the phase retrieval method [4] and is shown in Figure 10. We examined five different apodization intensity transmission values: 100%, 69%, 41%, 20%, and 8% for the 90 º Zernike phase shift case.…”

Section: The Relationship Between Signal and Noise Under Apodizationmentioning

confidence: 99%

“…The electric field was extracted from through-focus intensity images using a new phase retrieval algorithm described in Ref. [4]. From the complex field of the defect we can readily recover the effective defect height.…”

Section: Experiments Parametersmentioning

confidence: 99%

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

et al. 2015

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In this paper, we present an experimental verification of Zernike phase contrast enhanced EUV multilayer (ML) blank defect detection using the SHARP EUV microscope. A programmed defect as small as 0.35 nm in height is detected at focus with signal to noise ratio (SNR) up to 8. Also, a direct comparison of the through-focus image behavior between bright field and Zernike phase contrast for ML defects ranging from 40 nm to 75 nm in width on the substrate is presented. Results show the advantages of using the Zernike phase contrast method even for defects with both phase and absorption components including a native defect. The impact of pupil apodization combined with Zernike phase contrast is also demonstrated, showing improved SNR is due to the stronger reduction of roughness dependent noise than defect signal, confirming our previous simulation results. Finally we directly compare Zernike phase contrast, dark field and bright field microscopes.

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Section: Defect Characteristics: Pure Phase To Attenuated Phase Defectmentioning

confidence: 98%

Section: The Relationship Between Signal and Noise Under Apodizationmentioning

confidence: 99%

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

et al. 2015

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“…A more detailed explanation of the algorithm is being prepared. 4,7 The limitation of this algorithm is that the object needs to be weakly scattering (have a strong DC component). Phase roughness resulting from replicated multilayer roughness on EUV masks is an excellent test object-it is readily available on masks and satisfies the algorithm requirement well.…”

Section: Algorithmmentioning

confidence: 99%

Aberration estimation using EUV mask roughness

et al. 2015

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We present a method to extract aberrations from through-focus aerial images of mask roughness on an Extreme Ultraviolet (EUV) lithography mask. The algorithm uses a phase recovery algorithm based on the Weak Object Transfer Function to recover the phase and amplitude of the roughness, while considering aberrations and partially coherent illumination. Using the self-consistency of the recovered object, aberrations, and measured images as a metric, we optimize over the space of aberrations to estimate aberrations. Partially coherent illumination is needed to allow the effects of the object field and aberrations to be separated. We apply the algorithm to the EUV aerial image microscope, SHARP, using a parameterized ray tracing model to calculate the aberrations from a lower dimensional parameter space.

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“…We have previously applied our algorithm to EUV photomasks to study multilayer defects [28,29]. In this paper we describe the algorithm in depth, providing a description of convergence and validity.…”

Section: Introductionmentioning

confidence: 99%

Quantitative phase retrieval with arbitrary pupil and illumination

et al. 2015

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We present a general algorithm for combining measurements taken under various illumination and imaging conditions to quantitatively extract the amplitude and phase of an object wave. The algorithm uses the weak object transfer function, which incorporates arbitrary pupil functions and partially coherent illumination. The approach is extended beyond the weak object regime using an iterative algorithm. We demonstrate the method on measurements of Extreme Ultraviolet Lithography (EUV) multilayer mask defects taken in an EUV zone plate microscope with both a standard zone plate lens and a zone plate implementing Zernike phase contrast. Am. 73, 1434Am. 73, (1983. 5. J. R. Fienup, "Phase retrieval algorithms: a comparison," Appl. Opt. 21, 2758Opt. 21, -2769Opt. 21, (1982. 217, 408-432 (1953). 32. C. Chang, A. Sakdinawat, P. Fischer, E. Anderson, and D. Attwood, "Single-element objective lens for soft x-ray differential interference contrast microscopy," Opt. Lett. 31, 1564Lett. 31, -1566Lett. 31, (2006. 33. F. Zernike, "Phase contrast, a new method for the microscopic observation of transparent objects," Physica 9, 686-698 (1942

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Phase measurements of EUV mask defects

Cited by 3 publications

References 9 publications

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

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

Aberration estimation using EUV mask roughness

Quantitative phase retrieval with arbitrary pupil and illumination

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