Closed-Loop Autofocus Scheme for Scanning Electron Microscope

Cui, Le; Marturi, Naresh; Marchand, Éric; Dembélé, Sounkalo; Piat, Nadine

doi:10.1051/matecconf/20153205003

Cited by 5 publications

(5 citation statements)

References 13 publications

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“…It is obvious that the focus of the electron beam has an influence on the measurement of the diameter of a NP. Nevertheless, the adjustment of such a parameter can depend on the operator in some cases [27,28]. In this section we consider a situation in which the focus is not properly adjusted, in order to investigate its effect on the measurement result.…”

Section: Influence Of Scan Speed and Noise Reduction Param-mentioning

confidence: 99%

Methodology to evaluate the uncertainty associated with nanoparticle dimensional measurements by SEM

Crouzier

Delvallée

Allard

et al. 2019

Meas. Sci. Technol.

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The scanning electron microscopy (SEM) technique is widely used for the characterizing of nanoparticle (NP) size, but very few papers deal with NP dimensional metrology. This article reports on a methodology with which to evaluate the uncertainty budget associated with the measurement of the mean diameter of a standard silica NP population by SEM. In this context, the effects of potential error sources have been evaluated though a metrological qualification of the instrument. The measuring method, consisting of determining the area equivalent diameter taken at middle height (D eq-FWHM ), has been tested on a reference silica NP with an indicative certification value given by SEM/TEM (number-based modal diameter). Because agglomeration phenomena can cause measurements errors, semi-automatic homemade software has been employed to build the diameter distribution histogram, selecting only isolated particles. Finally, an uncertainty budget, including the main experimental components, has been established for the mean diameter measurement of this silica NP population. The main contributors to this uncertainty budget are the resolution linked to the dimension of the electron beam diameter at the focal plane, the calibration uncertainty on reference NPs, and the measurement repeatability.

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Section: Influence Of Scan Speed and Noise Reduction Param-mentioning

confidence: 99%

Methodology to evaluate the uncertainty associated with nanoparticle dimensional measurements by SEM

Crouzier

Delvallée

Allard

et al. 2019

Meas. Sci. Technol.

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“…Numerical modeling performed by us demonstrated that the sensitivity of the microscope with one probe was much worse. This can be explained by lacking of the additional interference energy flux formed in the counterpropagating evanescent fields of two probes [8] and providing deeper penetration into the examined medium as well as by the increased sensitivity in comparison with conventional technologies of measurements [10,11].…”

Section: Resultsmentioning

confidence: 99%

Numerical Modeling and Experimental Investigation of the Breadboard Model of a Near-Field Interference Microscope

2016

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Abstract.A circuit design for technology of near-field interference microwave microscopy using evanescent fields of several active radiators (probes) is suggested and substantiated. The feasibility of providing the spatial overlap of the evanescent fields of two probes representing expanding coaxial conical horns is demonstrated. It is shown that the structure of the electromagnetic field in the region of overlap can effectively be controlled by changing the phase difference of oscillations arriving at inputs of the probes. This technology can be used for diagnostics of liquid media comprising dielectric inhomogeneities, flaw detection, and hygroscopy.

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“…The precision of focus measure f ε ∼ is calculated from pseudo images under each condition of SNR and pattern frequency Q by using equations (7). To assure consistency with the simulation results in section 4.1 [2], precision is normalized by the height of the curve.…”

Section: Relationship Between Precision Of Focus Measure ε F Andmentioning

confidence: 99%

“…To find the maximum position of the focus measure, it uses a gradient ascent of the focus measures. The dynamic approach may reduce the number of images acquired for auto-focus [7]. However, it needs an almost-perfect focus-measure shape, which is often not the case in regard to SEM.…”

Section: Introductionmentioning

confidence: 99%

A robust SEM auto-focus algorithm using multiple band-pass filters

Harada

Obara

Nakamae

2016

Meas. Sci. Technol.

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An auto-focus algorithm using multiple band-pass filters for a scanning electron microscope (SEM) is proposed. To acquire sharp images of various kinds of defects by SEM defect observation in semiconductor manufacturing, the auto-focus process must be robust. A method for designing a band-pass filter for calculating the ‘focus measure’ (a key parameter of the auto-focus process) is proposed. To achieve an optimal specific frequency response for various images, multiple band-pass filters are introduced. As for the proposed method, two series of focus measures are calculated by using multiple band-pass filters independently, and it is selected according to reliability of the series of focus measures. The signal-to-noise ratio of an image for acceptable auto-focus precision is determined by simulation using pseudo images. In an experiment using the proposed method with real images, the success rate of auto focus is improved from 79.4% to 95.6%.

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Closed-Loop Autofocus Scheme for Scanning Electron Microscope

Cited by 5 publications

References 13 publications

Methodology to evaluate the uncertainty associated with nanoparticle dimensional measurements by SEM

Methodology to evaluate the uncertainty associated with nanoparticle dimensional measurements by SEM

Numerical Modeling and Experimental Investigation of the Breadboard Model of a Near-Field Interference Microscope

A robust SEM auto-focus algorithm using multiple band-pass filters

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