Simulation Study on Image Contrast and Spatial Resolution in Helium Ion Microscope

Inai, K.; Ohya, Kaoru; Ishitani, Tohru

doi:10.1093/jmicro/dfm024

Cited by 47 publications

(35 citation statements)

References 22 publications

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“…For future devices having ultra-shallow junctions and high doping concentrations, we need to know how the number of dopants changes within a few nanometres, therefore a suitably fine probe size may be beneficial for resolution as changes in electric potentials are confined within nanometre length-scales across the junction space charges. As dopant mapping relies on a relative change in the SE intensity between different doped regions, using the SHIM is expected to be advantageous because the SE yield is more sensitive to the material when induced by He + ions than by electron beam irradiation (Ward et al, 2006;Inai et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Dopant profiling based on scanning electron and helium ion microscopy

Chee

Boden

2016

Ultramicroscopy

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Highlights• Strong doping contrast from n-type regions in the SHIM without energy-filtering.• Sensitivity limits are established of the SHIM and SEM techniques.• We discuss the impact of SHIM imaging conditions on quantitative dopant profiling.• Doping contrast stems from different surface layer thicknesses in the SHIM and SEM.In this paper, we evaluate and compare doping contrast generated inside the scanning electron microscope (SEM) and scanning helium ion microscope (SHIM). Specialised energy-filtering techniques are often required to produce strong doping contrast to map donor distributions using the secondary electron (SE) signal in the SEM. However, strong doping contrast can be obtained from n-type regions in the SHIM, even without energy-filtering. This SHIM technique is more sensitive than the SEM to donor density changes above its sensitivity threshold, i.e. 10 16 or 10 17 donors cm -3 respectively on specimens with or without a p-n junction; its sensitivity limit is well above 2 × 10 17 acceptors cm -3 on specimens with or without a p-n junction. Good correlation is found between the widths and slopes of experimentally measured doping contrast profiles of thin p-layers and the calculated widths and slopes of the potential energy distributions across these layers, at a depth of 1 -3 nm and 5 -10 nm below the surface in the SHIM and the SEM respectively. This is consistent with the mean escape depth of SEs in Si being about 1.8 nm and 7 nm in the SHIM and SEM respectively, and we conclude that short escape depth, low energy SE signals are most suitable for donor profiling. Keywords: Doping contrast; Secondary electron energy filtering; Sensitivity limit; Electric potentials; Escape depth; p-n junction I. INTRODUCTIONThe future of the semiconductor industry depends critically on the ability to map dopants rapidly at high spatial resolution, and with high sensitivity. New spectroscopic techniques are in considerable demand to cope with the advent of next generation semiconductor devices having ultra-shallow junctions. Hence, dopant profiling at a resolution of sub-10 nm and detection sensitivity over a range of ~10 16 -10 20 dopants cm -3 are important requisites. Using an SEM, it is possible to provide a rapid and contactless technique for the two-dimensional mapping of electrically active dopant profiles based on SE doping contrast (Perovic et al., 1995;Turan et al., 1996;Castell et al., 1999;Elliott et al., 2002). Under standard imaging conditions, the p-type regions appear bright and the n-type regions appear dark, therefore doping contrast can be used to determine the position of electrical p-n junctions. The doping contrast mechanism is due to the built-in electric field across a p-n junction, modified by the effects of surface bandbending and external patch fields as the SEs are scattered by the surface electric potentials (Chee et al., 2011). Oatley et al. (1957) first studied SE doping contrast from p-n junctions where it was shown that reverse biasing enhances contrast by changing the electric ...

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Section: Introductionmentioning

confidence: 99%

Dopant profiling based on scanning electron and helium ion microscopy

Chee

Boden

2016

Ultramicroscopy

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“…As the surface is bombarded by He + ions instead of electrons, the penetration of the beam into the sample is smaller, improving the resolution (Chen et al, 2011). The secondary electron yield is much higher than that of electron microscopy, giving the images a better signal-to-noise ratio (Bell, 2009;Inai et al, 2007). In addition, there is no need to coat the samples with metal; this difference significantly improves the spatial resolution of the images.…”

Section: Introductionmentioning

confidence: 99%

Helium ion microscopy and ultra-high-resolution scanning electron microscopy analysis of membrane-extracted cells reveals novel characteristics of the cytoskeleton of Giardia intestinalis

Gadelha

Benchimol

Souza

2015

Journal of Structural Biology

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“…• the secondary electron yield from incident ions can be an order of magnitude higher than that from incident electrons, and should result in a good signal-to-noise ratio[3], [6], [7].…”

Section: Introductionmentioning

confidence: 99%

Helium Ion Beam Microscopy for Copper Grain Identification in BEOL Structures

Boom¹,

Parvaneh²,

Voci³

et al. 2009

AIP Conference Proceedings

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Abstract. Grain size determination in advanced metallization structures requires a technique with resolution ~2nm, with a high signal-to-noise ratio and high orientation-dependant contrast for unambiguous identification of grain boundaries. Ideally, such a technique would also be capable of high-throughput and rapid time-to-knowledge. The Helium Ion Microscope (HIM) offers one possibility for achieving these aims in a single platform. This article compares the performance of the HIM with Focused Ion Beam, Scanning Electron and Transmission Electron Microscopes, in terms of achievable image resolution and contrast, using plan-view and cross-sectional imaging of electroplated samples. Although the HIM is capable of sub-nanometer beam diameter, the low signal-to-noise ratio in the images necessitates signal averaging, which degrades the measured image resolution to 6-8nm. Strategies for improving S/N are discussed in light of the trade-off between beam current and probe size, accelerating voltage, and dwell time.

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Simulation Study on Image Contrast and Spatial Resolution in Helium Ion Microscope

Cited by 47 publications

References 22 publications

Dopant profiling based on scanning electron and helium ion microscopy

Dopant profiling based on scanning electron and helium ion microscopy

Helium ion microscopy and ultra-high-resolution scanning electron microscopy analysis of membrane-extracted cells reveals novel characteristics of the cytoskeleton of Giardia intestinalis

Helium Ion Beam Microscopy for Copper Grain Identification in BEOL Structures

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