Extreme High‐Resolution (XHR) SEM Using a Beam Monochromator

Young, Richard; Veen, G. N. A. van; Henstra, Alexander; Tuma, L.

doi:10.1002/9781118498514.ch3

Cited by 3 publications

(4 citation statements)

References 21 publications

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“…This sets a limitation on the shortest WD. In the experimental condition used here, the WD had a relatively large value of 3 mm, which is less optimal compared with a previous study (Young et al, 2012), where a WD of 1 mm or less was adopted for evaluation of an MC-SEM. In the latest SEMs, advanced OLs have been developed in which the aberration is minimized by using a magnetic immersion lens, beam-retarding via sample bias, and a beam booster.…”

Section: Further Studies Of the Mc-semmentioning

confidence: 99%

“…Barth et al (2000) have suggested improving LV-SEM performance by an ideal MC based on theoretical estimation of the dependencies of the probe size and current of the SEM on the energy spread reduced by the MC. An MC with a segmented gun lens successfully achieved a spatial resolution of 0.9 nm as a result of 25-75% edge resolution analysis at 1 kV acceleration voltage and 1 mm working distance (WD) for an SEM with a magnetic immersion lens (Young et al, 2009) and is now available as a commercial product (Young et al, 2012). The authors reported an energy resolution of the MC as 150 meV, but no experimental data in the form of energy spectra was shown.…”

Section: Introductionmentioning

confidence: 99%

“…The Wien filter monochromators (Mook & Kruit, 2000; Mukai et al, 2015) also require high precision fabrication due to the multipole configurations, in which electrodes and magnetic poles are precisely divided into eight pieces in the azimuth direction, aligned, and assembled with high accuracy. In the opposite case, the segmented gun lens MC (Young et al, 2012) for an SEM is a relatively simpler experimental setup. However, the energy resolution is limited to 150 meV and no experimental data such as energy spectra is shown in the reference.…”

Section: Introductionmentioning

confidence: 99%

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A Novel Monochromator with Offset Cylindrical Lenses and Its Application to a Low-Voltage Scanning Electron Microscope

et al. 2022

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Low-voltage scanning electron microscopes (LV-SEMs) are widely used in nanoscience. However, image resolution for SEMs is restricted by chromatic aberration due to energy spread of the electron beam at low acceleration voltage. This study introduces a new monochromator (MC) with offset cylindrical lenses (CLs) as one solution for LV-SEMs. The MC optics, with highly excited CLs in offset layouts, has advantageous high performance and simple experimental setup, making it suitable for field emission LV-SEMs. In a preliminary evaluation, our MC reduced the energy spread from 770 to 67 meV. The MC was integrated into a commercial SEM equipped with an out-lens (a conventional objective lens without immersion magnetic or retarding electric fields) and an Everhart–Thornley detector. Comparing SEM images under two conditions with the MC turned on or off, the spatial resolution was improved by 58% at 0.5 and 1 keV. The filtering effect of the MC decreased the probe current with a ratio (i.e., transmittance) of 5.7%, which was consistent with estimations based on measured energy spreads. To the best of our knowledge, this is the first report on an effective MC with higher-energy resolution than 100 meV and the results offer encouraging prospects for LV-SEM technology.

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Section: Further Studies Of the Mc-semmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Novel Monochromator with Offset Cylindrical Lenses and Its Application to a Low-Voltage Scanning Electron Microscope

et al. 2022

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“…The various arrangements like energy selective backscatter detector, distributed backscatter detector, low angle backscatter electron detector, etc. (Young & van Veen, 2013) for directing the electrons into a separate compartment for detection also use additional high voltages for acceleration of the electrons. The performance of such systems is very good, but they all are relatively complex.…”

Section: Introductionmentioning

confidence: 99%

First-Surface Scintillator for Low Accelerating Voltage Scanning Electron Microscopy (SEM) Imaging

Tzolov

Barbi²,

Bowser

et al. 2018

Microsc Microanal

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Highly luminescent thin films of zinc tungstate (ZT) have been deposited on top of conventional scintillators (Yttrium Aluminum Perovskite, Yttrium Aluminum Garnet) for electron detection in order to replace the need for a top conducting layer, such as indium tin oxide (ITO) or aluminum, which is non-scintillating and electron absorbing. Such conventional conducting layers serve the single purpose of eliminating electrical charge build-up on the scintillator. The ZT film also eliminates charging, which has been verified by measuring the Duane–Hunt limit and electron emission versus accelerating voltage. The luminescent nature of the ZT film ensures effective detection of low energy electrons from the very top surface of the structure ZT/scintillator, which we call “first-surfacescintillator”. The cathodoluminescence has been measured directly with a photodetector and spectrally resolved at different accelerating voltages. All results demonstrate the extended range of operation of the first-surface scintillator, while the conventional scintillators with a top ITO layer decline below 5 kV and have practically no output below 2 kV. Scintillators of different types were integrated in a detection system for backscattered electrons (BSE). The quality of the image at high accelerating voltages is comparable with the conventional scintillator and commercial BSE detector, while the image quality at 1 kV from the first-surface scintillator is superior.

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Low-energy scanning electron microscope using a monochromator with double-offset cylindrical lenses

Ogawa

Cho

Ahn

2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The nanoelectronics industry demands continuous improvement in the performance of scanning electron microscopes (SEMs). Extremely low energies of less than 1 keV are required for SEM observations to allow the subsurface and nanoscale information of target specimens to be measured with minimized charge-up and beam damage depths because of the reduced interaction volumes. In this article, the authors propose a new monochromator (MC) structure and investigate its applicability to SEMs operating at such extra-low energies. The proposed MC, which uses double-offset cylindrical lenses, can perform energy filtering in its midsection and form a stigmatic and nonenergy dispersive image at the exit. The energy resolution is expected to be better than 10 meV for a pass energy of 4 keV. The MC has the additional advantage of a simple but robust structure, which is essential for industrial applications. Assuming the use of ideal and high-performance SEM optics, for which the spherical aberration coefficient and the chromatic aberration coefficient are both 1 mm, beam diameters measured in terms of the full width that contains 50% of the beam current (FW50) are calculated at the specimen position. Use of the MC improves the beam diameter dramatically to 4.4 nm, as compared to the diameter of 19.7 nm for the SEM without the MC, at a landing energy of 100 eV. The chromatic aberration contribution also becomes negligible because of the MC. The beneficial effects of the MC with regard to the beam diameter become increasingly prominent at lower landing energies ranging down to 10 eV. A SEM using this MC can generate highly monochromatic (10 meV) electron probe beams with small size (5 nm) and low energy (100 eV), which indicates the additional possibility of a new surface electron microscope that uses phonon signals. Based on this theoretical investigation, the authors conclude that this MC can effectively improve the SEM's performance capabilities in the extra-low-energy region.

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Extreme High‐Resolution (XHR) SEM Using a Beam Monochromator

Cited by 3 publications

References 21 publications

A Novel Monochromator with Offset Cylindrical Lenses and Its Application to a Low-Voltage Scanning Electron Microscope

A Novel Monochromator with Offset Cylindrical Lenses and Its Application to a Low-Voltage Scanning Electron Microscope

First-Surface Scintillator for Low Accelerating Voltage Scanning Electron Microscopy (SEM) Imaging

Low-energy scanning electron microscope using a monochromator with double-offset cylindrical lenses

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