Submicron imaging of buried integrated circuit structures using scanning confocal electron microscopy

Frigo, Sean P.; Levine, Zachary H.; Zaluzec, Nestor J.

doi:10.1063/1.1506010

Cited by 99 publications

(75 citation statements)

References 7 publications

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“…Scanning confocal electron microscopy (SCEM) was first demonstrated in uncorrected TEM by Frigo and coworkers [19] in an application to the specific problem of imaging thick samples. One of the key advantages of the confocal scanning optical microscope (CSOM), however, is the retrieval of threedimensional imaging through the process of optical sectioning.…”

Section: Confocal Imagingmentioning

confidence: 99%

Applications of the Oxford-JEOL aberration-corrected electron microscope

Nellist

Kirkland

2010

Philosophical Magazine

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Section: Confocal Imagingmentioning

confidence: 99%

Applications of the Oxford-JEOL aberration-corrected electron microscope

Nellist

Kirkland

2010

Philosophical Magazine

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“…Frigo et al. have demonstrated the first confocal images with electrons, or confocal scanning transmission electron microscopy (STEM) [1]. They produced images of microelectronic circuits with resolution of ~80 nm through a 5 µm-thick sample [1].…”

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“…have demonstrated the first confocal images with electrons, or confocal scanning transmission electron microscopy (STEM) [1]. They produced images of microelectronic circuits with resolution of ~80 nm through a 5 µm-thick sample [1]. In optical confocal microscopy, 3-D images are routinely obtained by optical sectioning, which is stacking 2-D images acquired with different positions of the focal plane [2].…”

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Confocal Scanning Transmission Electron Microscopy: Theoretical Analysis of Three-Dimensional Imaging

Einspahr

Voyles

2005

MAM

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Confocal microscopy is an imaging mode in which a pre-specimen lens focuses a fine probe on the specimen, then a post-specimen lens forms an image of the probe on an axial point detector. Frigo et al. have demonstrated the first confocal images with electrons, or confocal scanning transmission electron microscopy (STEM) [1]. They produced images of microelectronic circuits with resolution of ~80 nm through a 5 µm-thick sample [1]. In optical confocal microscopy, 3-D images are routinely obtained by optical sectioning, which is stacking 2-D images acquired with different positions of the focal plane [2]. Optical sectioning with confocal STEM has only recently become useful with the advent of spherical aberration (C 3 ) corrected electron optics, but it holds potential for nanometer-resolution, 3-D imaging of nanostructures and macromolecules. We have investigated the potential 3-D imaging performance of current and next-generation aberration correctors and begun to investigate the limitations imposed by dynamical electron scattering in the sample.We have calculated the optimum 3-D contrast transfer function (CTF) H(l,w), where l is the radial spatial frequency and w is the spatial frequency along the optic axis, for confocal STEM based on the scalar wave theory of confocal imaging developed by Gu [2]. We have considered the effect of C 3 , fifth-order spherical aberration C 5 , and beam convergence semi-angle α for 200 kV electrons with a point source and point detector. As in other imaging modes, it is possible to balance higherorder, un-adjustable aberrations (in this case C 5 ) with lower-order, adjustable aberrations (in this case C 3 ). Defocus is used to move the focal plane, so it has no effect on the 3-D CTF [2]. We define the optimum C 3 for a given α as resulting in a minimum in the integrated difference between the aberrated CTF and the unaberrated CTF with same α. Fig. 1 shows the optimum C 3 versus α for C 5 = 50 mm. C 3 scales as α 2 . As shown in Fig. 2(c), this C 3 is not the same as that which minimizes the integrated aberration function χ(k). The optimum α is defined as the largest α which does not introduce severe distortions such as zero-transfer bands in the CTF; in practice this limits the integrated deviation between the aberrated and unaberrated CTF to ~10%.For current-generation aberration correctors, we assumed C 5 = 50 mm [3]. The optimum conditions for a microscope equipped with two such correctors (one for the probe-forming lens and one for the image-forming lens) are C 3 = -25.2 µm and α = 32.5 mrad. The 3-D CTF for a microscope with no aberrations and α = 32.5 mrad is shown in Fig. 2(a); the optimum aberrated CTF with C 5 = 50 mm is shown in Fig. 2(b). The aberrated CTF shows a dip in transfer at low spatial frequencies and an overall decrease in transfer at high axial spatial frequencies. Fig. 2(c) shows this more clearly in a cut through the 3-D CTF as a function of w at l = 0.13 nm -1 . Based on the CTF, this confocal STEM should achieve 2.4 nm axial resolution.Our calculations...

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“…Recently, confocal scanning transmission electron microscopy (STEM), which is based on applying the principles of confocal imaging to transmission electron microscopy (TEM), has attracted considerable interest as a promising depth-sectioning and 3D imaging technique [1][2][3][4][5][6], along with computed tomography and aberration-corrected STEM. Confocal STEM imaging has been demonstrated by Zaluzec and his coworkers [1,2]. However, 3D imaging with confocal STEM has not yet been performed because of some practical difficulties.…”

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“…Hashimoto * , M. Shimojo **,*** , K. Mitsuishi **,**** and M. Takeguchi **,***** * International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan ** High Voltage Electron Microscopy Station, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan *** Advanced Science Research Laboratory, Saitama Institute of Technology, 1690 Fusaiji, Fukaya 369-0293, Japan **** Quantum Dot Research Center, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan ***** Advanced Nano-characterization Center, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan Three-dimensional (3D) imaging has been an indispensable technique in various industrial and scientific fields. Recently, confocal scanning transmission electron microscopy (STEM), which is based on applying the principles of confocal imaging to transmission electron microscopy (TEM), has attracted considerable interest as a promising depth-sectioning and 3D imaging technique [1][2][3][4][5][6], along with computed tomography and aberration-corrected STEM. Confocal STEM imaging has been demonstrated by Zaluzec and his coworkers [1,2].…”

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Three-dimensional Observation of Carbon Nanostructures with Confocal Scanning Tansmission Electron Microscopy

et al. 2009

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Three-dimensional (3D) imaging has been an indispensable technique in various industrial and scientific fields. Recently, confocal scanning transmission electron microscopy (STEM), which is based on applying the principles of confocal imaging to transmission electron microscopy (TEM), has attracted considerable interest as a promising depth-sectioning and 3D imaging technique [1][2][3][4][5][6], along with computed tomography and aberration-corrected STEM. Confocal STEM imaging has been demonstrated by Zaluzec and his coworkers [1,2]. However, 3D imaging with confocal STEM has not yet been performed because of some practical difficulties. We employed a stage-scanning system in order to overcome the difficulties [5,6]. By using the system, only a specimen is moved three-dimensionally under a fixed confocal lens configuration. However, obtained confocal STEM images did not demonstrate a significant improvement in the depth resolution. Further, theoretical studies have reported that the interpretation of confocal STEM images is not straightforward because of nonlinear phase contrast transfer [7,8]. In this work, we propose dark-field STEM imaging under the confocal condition by using an annular-dark-filed (ADF) aperture. Furthermore, we observed carbon nanostructures with confocal ADF-STEM to perform 3D imaging. Figure 1 shows a schematic diagram of the confocal ADF-STEM system. A conventional TEM equipped with a STEM module (JEOL Ltd.: JEM-2100F, Cs = 1.0 mm) and piezo-driven specimen holder were used for confocal STEM imaging. The specimen holder was modified and controlled by computer programming for stage scanning along the X, Y and Z axes. In the upper configuration, a condenser lens creates a well-focused probe in a specimen, and in the lower one, an imaging lens magnifies and projects an image of the probe on a STEM detector. Detected signals were synchronized with the specimen displacement and displayed on a computer screen as a stagescanning STEM image. The annular aperture was made from a Mo foil using a focused ion beam technique and arranged under the specimen to cut off the direct beam and select only scattered electrons. Depth sectioning was performed by rejecting electrons from the out-of-focal plane in the specimen with a pinhole aperture in front of the detector.Figures 2 (a) and (b) show X-Y and X-Z slice images of Au particles on an amorphous carbon film, respectively. In the X-Y scan image, Au particles with diameter of 5 nm were observed as well as a conventional dark-filed STEM image. The X-Z slice image of region indicated by arrows in the X-Y image showed the elongated Au particles along the Z axis. It was found that the particles were detected at the restricted Z position. This indicated that confocal ADF-STEM imaging drastically

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Submicron imaging of buried integrated circuit structures using scanning confocal electron microscopy

Abstract: Articles you may be interested inPattern matching between a scanning electron microscopy exposed pattern image of large-scale integrated fine structures and computer-aided design layout data by using the relaxation method

Cited by 99 publications

References 7 publications

Applications of the Oxford-JEOL aberration-corrected electron microscope

Applications of the Oxford-JEOL aberration-corrected electron microscope

Confocal Scanning Transmission Electron Microscopy: Theoretical Analysis of Three-Dimensional Imaging

Three-dimensional Observation of Carbon Nanostructures with Confocal Scanning Tansmission Electron Microscopy

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