Nanoscale holographic interferometry for strain measurements in electronic devices

Hÿtch, Martin; Houdellier, Florent; Hüe, Florian; Snoeck, E.

doi:10.1038/nature07049

Cited by 440 publications

(302 citation statements)

References 27 publications

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“…Conventionally, the reference wave in electron holography is the beam passing through the vacuum. However, in principle every wave with known or invariant phase distribution, for example, the electron beam penetrating the Al gate layer here, is also available to preserve the relative phase difference feature between the insulator layers and the Si substrate 20,21 , as discussed in Method. A lowmagnification cross-section image (Fig.…”

Section: Resultsmentioning

confidence: 99%

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Yao

Huo

et al. 2013

Nat Commun

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Charge-trapping memory with high-k insulator films is a candidate for future memory devices. Many efforts with different indirect methods have been made to confirm the trapping position of the charges, but the reported results in the literatures are contrary, from the bottom to the top of the trapping layers. Here we characterize the local charge distribution in the high-k dielectric stacks under different bias with in situ electron holography. The retrieved phase change induced by external bias strength is visualized with high spatial resolution and the negative charges aggregated on the interface between Al 2 O 3 block layer and HfO 2 trapping layer are confirmed. Moreover, the positive charges are discovered near the interface between HfO 2 and SiO 2 films, which may have an impact on the performance of the chargetrapping memory but were neglected in previous models and theory.

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Section: Resultsmentioning

confidence: 99%

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Yao

Huo

et al. 2013

Nat Commun

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“…However, giving the standard deviation among independent measurements that physically ought to yield identical results is regarded as the most reliable way by the authors, which is why we derived our value from an ensemble of 50 diffraction patterns. As to dark-field holographic techniques, this allows direct comparison only with the precision of 2{10 Ϫ3 determined from the standard deviation in the substrate region of the strain map Hÿtch et al, 2008! calculated the precision of 2{10 Ϫ4 by first deriving five strain profiles averaged over 65 nm wide regions and then giving the standard deviation among these profiles.…”

Section: Discussionmentioning

confidence: 99%

Strain Measurement in Semiconductor Heterostructures by Scanning Transmission Electron Microscopy

et al. 2012

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This article deals with the measurement of strain in semiconductor heterostructures from convergent beam electron diffraction patterns. In particular, three different algorithms in the field of~circular! pattern recognition are presented that are able to detect diffracted disc positions accurately, from which the strain in growth direction is calculated. Although the three approaches are very different as one is based on edge detection, one on rotational averages, and one on cross correlation with masks, it is found that identical strain profiles result for an In x Ga 1Ϫx N y As 1Ϫy /GaAs heterostructure consisting of five compressively and tensile strained layers. We achieve a precision of strain measurements of 7-9{10 Ϫ4 and a spatial resolution of 0.5-0.7 nm over the whole width of the layer stack which was 350 nm. Being already very applicable to strain measurements in contemporary nanostructures, we additionally suggest future hardware and software designs optimized for fast and direct acquisition of strain distributions, motivated by the present studies.

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“…7 Furthermore, strain has been investigated by convergent-beam electron diffraction (CBED) 8 and nanobeam electron diffraction (NBD), 9 as well as by nanoscale holographic interferometry. 10 The ability to separate the information into strain and composition on nanoscale proves to be challenging. As an example, GPA and PPA are based on evaluation of the crystal lattice spacing, which regretfully depends on both strain and composition.…”

Section: Introductionmentioning

confidence: 99%

Effect of strain on low-loss electron energy loss spectra of group-III nitrides

et al. 2011

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Thin films of AlN experiencing different strain states were investigated with a scanning transmission electron microscope (STEM) by low-loss electron energy loss spectroscopy (EELS). The results conclude that the low-loss properties and in particular, the plasmon peak position is shifted as a direct consequence of the inherent strain of the sample. The results reveal that strain, even minor levels, can be measured by STEM-EELS. These results were further corroborated by full potential calculations and expanded to include the similar III nitrides GaN and InN. It is found that a unit-cell volume change of 1% results in a bulk plasmon peak shift of 0.159, 0.168, and 0.079 eV for AlN, GaN, and InN, respectively, according to simulations. The AlN peak shift was experimentally corroborated with a corresponding peak shift of 0.156 eV. The unit-cell volume is used here since it is found that regardless of in-and out-of-plane lattice augmentation, the low-loss properties appear near identical for constant volume. These results have an impact on the interpretation of the plasmon energy and its applicability for determining and separating stress and composition. It is found that while the bulk plasmon energy can be used as a measure of the composition in a group-III nitride alloy for relaxed structures, the presence of strain significantly affects such a measurement. The strain is found to have a lower impact on the peak shift for Al 1-x In x N (∼3% compositional error per 1% volume change) and In 1-x Ga x N alloys compared to significant variations for Al 1-x Ga x N (16% compositional error for 1% volume change). Hence a key understanding in low-loss studies of III nitrides is that strain and composition are coupled and affect one another.

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Nanoscale holographic interferometry for strain measurements in electronic devices

Cited by 440 publications

References 27 publications

In situ electron holography study of charge distribution in high-κ charge-trapping memory

In situ electron holography study of charge distribution in high-κ charge-trapping memory

Strain Measurement in Semiconductor Heterostructures by Scanning Transmission Electron Microscopy

Effect of strain on low-loss electron energy loss spectra of group-III nitrides

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