Scatterometry reference standards to improve tool matching and traceability in lithographical nanomanufacturing

Agócs, Emil; Bodermann, Bernd; Burger, Sven; Dai, Gaoliang; Endres, Johannes; Hansen, Poul Erik; Nielson, Lars; Madsen, Morten Hannibal; Heidenreich, Sebastian; Krumrey, Michael; Loechel, B.; Probst, J.; Scholze, Frank; Soltwisch, Victor; Wurm, Matthias

doi:10.1117/12.2190409

Cited by 6 publications

(2 citation statements)

References 21 publications

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“…The first steps towards a reference standard for scatterometry were described in 2012 [136] with focus on improving the tool-to-tool matching between scatterometers, CD-AFMs and CD-SEMs. The first data for such a reference standard was presented in 2015 [137] where a comparison of SEM, AFM, EUV scatterometry and Mueller polarimetry was made. These high quality samples should eventually be commercially available and pave the way for traceable scatterometry measurements.…”

Section: Discussionmentioning

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: Discussionmentioning

confidence: 99%

Scatterometry—fast and robust measurements of nano-textured surfaces

Madsen

Hansen

2016

Surf. Topogr.: Metrol. Prop.

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“…Recently, at PTB we have demonstrated the performance of DUV goniometric scatterometry for the measurements of deep sub-wavelength silicon line structures for grating periods down to 50 nm and CDs down to about 25 nm [29,30]. For these measurements we applied a set of different polarisations and measurement geometries to enhance the degree of structure information in the measured scatterograms.…”

Section: Introductionmentioning

confidence: 99%

Optical dimensional metrology at Physikalisch-Technische Bundesanstalt (PTB) on deep sub-wavelength nanostructured surfaces

Bodermann

Ehret

Endres

et al. 2016

Surf. Topogr.: Metrol. Prop.

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The dark-field microscopy method with alternating grazing incidence UV illumination (UV-AGID) developed at Physikalisch-Technische Bundesanstalt offers the possibility of measuring individual isolated line structures with linewidths down to the sub-wavelength regime. In contrast, scatterometry is able and already widely used to measure average dimensional parameters of periodic structures down to the deep sub-wavelength regime. Both methods can be used for dimensional measurements of micro-and nanostructures, in particular the critical dimensions (CDs) on wafers or photomasks in the semiconductor industry, complementing each other favourably. Based on numerical simulations, we have investigated the ultimate limits of these two methods in the deep sub-wavelength regime. It has been shown that AGID microscopy in the DUV spectral range is in principle capable of measuring line structures with CDs down to a few 10 nm, depending on the structure material. For scatterometry, no fundamental limit has been observed. In practice, a technical limit due to the limited signal-tonoise ratio is expected for CDs of a few nm in width. RECEIVED

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Solar Cells with Photonic and Plasmonic Structures

Petrik

2018

Spectroscopic Ellipsometry for Photovoltaics

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Scatterometry reference standards to improve tool matching and traceability in lithographical nanomanufacturing

Cited by 6 publications

References 21 publications

Scatterometry—fast and robust measurements of nano-textured surfaces

Scatterometry—fast and robust measurements of nano-textured surfaces

Optical dimensional metrology at Physikalisch-Technische Bundesanstalt (PTB) on deep sub-wavelength nanostructured surfaces

Solar Cells with Photonic and Plasmonic Structures

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