YieldStar: a new metrology platform for advanced lithography control

Maas, J.H. van der; Ebert, Martin; Bhattacharyya, Kaustuve; Cramer, Hugo; Becht, Arthur; Keij, Stefan; Plug, Reinder; Fuchs, Andreas; Kubis, Michael; Hoogenboom, Tom; Vaenkatesan, Vidya

doi:10.1117/12.896902

Cited by 20 publications

(5 citation statements)

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“…One concluded that they were very comparable but angular scatterometry was easier to implement [65] and another study concluded that spectroscopic scatterometry was superior [66]. It is interesting to observe that today's commercial state-ofart scatterometers on the market use both angular and/ or spectroscopic techniques [67][68][69].…”

Section: Spectroscopic Scatterometersmentioning

confidence: 99%

Scatterometry—fast and robust measurements of nano-textured surfaces

Madsen

Hansen

2016

Surf. Topogr.: Metrol. Prop.

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Scatterometry is a fast, precise and low cost way to determine the mean pitch and dimensional parameters of periodic structures with lateral resolution of a few nanometer. It is robust enough for inline process control and precise and accurate enough for metrology measurements. Furthermore, scatterometry is a non-destructive technique capable of measuring buried structures, for example a grating covered by a thick oxide layer. As scatterometry is a non-imaging technique, mathematical modeling is needed to retrieve structural parameters that describe a surface. In this review, the three main steps of scatterometry are discussed: the data acquisition, the simulation of diffraction efficiencies and the comparison of data and simulations. First, the intensity of the diffracted light is measured with a scatterometer as a function of incoming angle, diffraction angle and/or wavelength. We discuss the evolution of the scatterometers from the earliest angular scatterometers to the new imaging scatterometers. The basic principle of measuring diffraction efficiencies in scatterometry has remained the same since the beginning, but the instrumental improvements have made scatterometry a state-of-the-art solution for fast and accurate measurements of nano-textured surfaces. The improvements include extending the wavelength range from the visible to the extreme ultra-violet range, development of Fourier optics to measure all diffraction orders simultaneously, and an imaging scatterometer to measure area of interests smaller than the spot size. Secondly, computer simulations of the diffraction efficiencies are discussed with emphasis on the rigorous coupled-wave analysis (RCWA) method. RCWA has, since the mid-1990s, been the preferred method for grating simulations due to the speed of the algorithms. In the beginning the RCWA method suffered from a very slow convergence rate, and we discuss the historical improvements to overcome this challenge, e.g. by the introduction of Li's factorization rules and the introduction of the normal vector method. The third step is the comparison, where the simulated diffraction efficiencies are compared to the experimental data using an inverse modeling approach. We discuss both a direct optimization scheme using a differential evolution algorithm and a library search strategy where diffraction efficiences of expected structures are collected in a database. For metrology measurements two methods are described for estimating the uncertainty of the fitting parameters. The first method is based on estimating the confidence limits using constant chi square boundaries, which can easily be computed when using the library search strategy. The other method is based on calculating the covariances of all the free parameters using a least square optimization. Scatterometry is already utilized in the semiconductor industry for in-line characterization. However, it also has a large potential for other industrial sectors, including sectors making use of injection molding or roll-2-roll fabrication. Using the...

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Section: Spectroscopic Scatterometersmentioning

confidence: 99%

Scatterometry—fast and robust measurements of nano-textured surfaces

Madsen

Hansen

2016

Surf. Topogr.: Metrol. Prop.

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“…Therefore, in most cases, only the spectral diffraction efficiencies in the zero diffraction order (that is, in the direction of specular reflection) is determined at high speeds with a spectrometer. [30][31][32] The above techniques have been used very widely in today's commercial state-of-art scatterometers, [33][34][35] and a very high in situ measurement accuracy is guaranteed. However, considering that the zero order diffraction efficiency is normally not as sensitive as the nonzero orders when changing grating parameters, 35 more details of the grating can therefore be computed (or a certain parameter can be fitted with increasing robustness) if the diffraction efficiencies at many wavelengths (not in the zero diffraction order) can be simultaneously measured in a short time.…”

Section:  mentioning

confidence: 99%

Motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a grating

Wang

Liu

Shao

et al. 2018

Review of Scientific Instruments

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The measurement of the spectral diffraction efficiencies of a diffraction grating is essential for improving the manufacturing technique and for assessing the grating's function in practical applications. The drawback of the currently popular measurement technique is its slow speed due to the hundreds of repetitions of two kinds of time-consuming mechanical movements during the measuring process (i.e., the rotation of the mechanical arm to capture the light beam and the mechanical variation of the output wavelength of the grating monochromator). This limitation greatly restricts the usage of this technique in dynamic measurement. In this manuscript, we present a motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a plane grating, effectively eliminating the aforementioned two kinds of mechanical movements. Herein, the proposed solution for removing the first kind of mechanical movement is tested, and the experimental result shows that the proposed method can be successfully used to measure the plane transmission grating's spectral diffraction efficiencies in the wavelength range of 550-750 nm. The method for eliminating the second kind of mechanical movement is not verified in this manuscript; however, we think that it is very straightforward and commercially available. We estimate that the spectral measurement can be achieved on a millisecond time scale by combining the two solutions. Our motionless and fast measuring technique will find broad applications in dynamic measurement environments and mass industrial testing.

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“…Among various OCD measurement methods, micro-ellipsometry is a promising OCD technique as it enables massive angular measurements and small-spot illumination. Various micro-ellipsometry techniques have been studied by global research centers 7,8 and global metrology and inspection companies including KLA, ASML, and Onto Innovation [9][10][11][12][13][14][15][16] . We also have recently proposed interferometric micro-ellipsometry, named self-interference pupil ellipsometry (SIPE) 17,18 .…”

Section: Introductionmentioning

confidence: 99%

Improving the accuracy and precision of OCD measurement by systematic error correction in self-interference pupil ellipsometry

Lee

Park

Lee

et al. 2023

Optical Measurement Systems for Industrial Inspection XIII

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To achieve high accuracy and precision in optical metrology for advanced semiconductors, it is crucial to identify and compensate for errors from optical components and environmental perturbations. In this study, we investigated the sources of the errors in the interferometric ellipsometer developed for next-generation OCD. The objective lens and beam splitters, the critical optical components of the system, are intensively investigated. The system errors induced by temperature fluctuation, wavelength inaccuracy, and defocus were quantitatively examined. We also proposed methods for compensating individual errors and analyzed the effect of the compensation. As a result of error compensation, the accuracy and precision of the system is improved by 6.9 times and 2.3 times, respectively. Although the investigation was conducted based on our interferometric ellipsometry system, the finding is not limited to this system, as these errors are commonly found in most optical metrology systems. The proposed method for error compensation will be essential strategies for various ellipsometry systems suffering from a low level of accuracy and precision.

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YieldStar: a new metrology platform for advanced lithography control

Cited by 20 publications

References 0 publications

Scatterometry—fast and robust measurements of nano-textured surfaces

Scatterometry—fast and robust measurements of nano-textured surfaces

Motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a grating

Improving the accuracy and precision of OCD measurement by systematic error correction in self-interference pupil ellipsometry

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