JP5228463B2 - Electron beam apparatus, electron beam shape measuring method and image processing method - Google Patents

Description

  The present invention relates to an electron beam apparatus capable of measuring the shape of an electron beam irradiated on a sample, an electron beam shape measuring method in the electron beam apparatus, and image processing for removing a false image from a scanning transmission electron microscope image (STEM image) Regarding the method.

  HAADF (High Angle Annular Dark Field) -STEM, which is one of the high-resolution image observation methods using a scanning transmission electron microscope (STEM), increases the atomic arrangement. Since it can be observed with a resolution image, it is extremely useful for analyzing the crystal structure of a minute region. In the HAADF-STEM method, a finely focused electron beam probe is scanned along a sample surface, and transmitted electrons scattered at a large angle are detected by a ring-shaped detector to obtain an observation image (STEM image).

  However, in STEM image observation, it has been found that a false image appears in the observed image due to the spherical aberration of the electromagnetic lens and the change in the shape of the electron beam probe due to the electromagnetic lens condition and the focus condition. A false image is an image that appears as if there are atoms at positions where no atoms actually exist.

  It is known that a false image can be removed by performing a deconvolution process (a kind of image processing) on a STEM image. However, in order to remove the false image by the deconvolution process, it is necessary to accurately know the shape of the electron beam probe. The focus position in STEM image observation is different from that of a normal transmission electron microscope (TEM), and in STEM image observation, the intensity of the diffraction image is visualized as a real image, so the shape of the electron probe is directly observed. I can't do it. Therefore, conventionally, the electron beam probe shape is calculated by simulation based on conditions at the time of STEM image observation.

In the previous application (Patent Document 1) by the inventors of the present application, a STEM image is deconvolved using an electron beam probe shape simulation method and an electron beam probe shape simulation result, and a false image (virtual image) is removed. How to do is described.
JP 2003-249186 A

  As described above, the STEM electron beam probe shape is conventionally obtained by simulation calculation. However, from experiments and research conducted by the inventors of the present application, the actual electron beam probe shape and the electron probe shape calculated by the simulation are different, so that image processing by deconvolution is not performed properly, and accurate atom It turned out that the image could not be obtained. In other words, the actual electron beam probe shape of the STEM is considered to be different from the electron beam probe shape obtained by the simulation calculation due to the influence of some disturbance.

  From the above, an object of the present invention is to provide an electron beam apparatus and an electron beam shape measuring method capable of measuring the shape of an electron beam (electron beam probe) irradiated on a sample with high accuracy. Another object of the present invention is to provide an image processing method for appropriately removing a false image from a STEM image.

According to one aspect of the present invention, there is provided an electron beam apparatus capable of measuring the shape of an electron beam irradiated on a sample, an electron beam source that outputs an electron beam, and an electron beam output from the electron beam source. An objective lens that focuses on a sample position, a scanning coil that is disposed between the electron beam source and the objective lens and that can scan the electron beam along the surface of the sample disposed at the sample position ; An imaging lens for imaging an electron beam that has passed through the sample position on an imaging surface, a first electron beam detector disposed at the sample position during electron beam shape measurement, and the image formation during the electron beam shape measurement A second electron beam detector disposed at a position of the surface, an imaging unit that is disposed at or near the imaging surface and images the electron beam shape at the time of measuring the electron beam shape, the electron beam source, the objective Controlling the lens, the scanning coil and the imaging lens. The first electron beam detector, to obtain an electron microscope image the second electron beam detector, and a control unit for inputting a signal output from the imaging unit, to detect electrons transmitted through the sample An electron microscope image acquisition unit, and the control unit includes an electron beam shape measurement mode for measuring an electron beam shape, and an electron microscope image acquisition mode for acquiring the electron microscope image. In the electron beam shape measurement mode, The imaging lens is controlled to project the electron beam shape at the sample position onto the imaging unit, and in the electron microscope image acquisition mode, the first electron beam detector, the second electron beam detector, and the An electron beam apparatus is provided that controls the imaging lens so that the imaging unit is retracted from the electron beam passage region and a diffraction image of the sample is projected onto the electron microscope image acquisition unit .

  According to another aspect of the present invention, an objective lens that focuses the electron beam output from the electron beam source on the sample position, and an imaging lens that forms an image of the electron beam that has passed through the sample on the imaging surface; In the electron beam shape measuring method of the electron beam apparatus, the first electron beam detector is disposed at the focal position of the objective lens, and the first electron beam detector is moved so that the current density is maximized. The first electron beam detector is retracted from the electron beam passage area, the second electron beam detector is disposed on the imaging surface of the imaging lens, and the second electron beam Adjusting the lens condition of the imaging lens so that the current density of the electron beam detected by the detector is maximized, and retracting the second electron beam detector from the electron beam passage area to Measuring electron beam shape on an image plane of an image lens Measurement method is provided.

  In the present invention, the lens condition of the imaging lens disposed behind the sample position is adjusted, and the electron beam shape on the sample surface is projected onto the imaging surface of the imaging lens. Thereby, the electron beam shape in the sample surface can be measured with high accuracy. Further, according to the present invention, since the shape of the electron beam can be measured with high accuracy, the false image can be excluded from the STEM image with high accuracy by applying to the deconvolution processing of the STEM image.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a configuration of an electron beam apparatus according to an embodiment of the present invention. In the present embodiment, an example in which the present invention is applied to a scanning transmission electron microscope (STEM) is shown.

  As shown in FIG. 1, the scanning transmission electron microscope according to this embodiment includes a control unit 10, an electron gun (electron beam source) 11, converging lenses 12a and 12b, a converging lens diaphragm 13, and a deflection coil 14. A scanning coil 15, a spherical aberration / astigmatism correction unit 16, a secondary electron detector 17, objective lenses 18a and 18b, a sample mounting unit 19 on which a sample 20 is mounted, and an upper electron beam detector. (First electron beam detector) 21, imaging lenses (also called projection lenses) 22a, 22b and 22c, shutter 23, fluorescent plate 24, and lower electron beam detector (second electron beam detector). 25, a charge-coupled device (CCD) camera (imaging unit) 26, and a STEM detector (electron microscope image acquisition unit) 27.

  The electron gun 11 accelerates electrons with an acceleration voltage corresponding to a signal from the control unit 10 and outputs the electrons as an electron beam. Below the electron gun 11, multiple stages (two stages in FIG. 1) of converging lenses 12a and 12b are arranged. These converging lenses 12 a and 12 b converge the electron beam emitted from the electron gun 11 to a desired size in accordance with a signal from the control unit 10.

  A converging lens stop 13 is disposed below the converging lenses 12a and 12b. Since the electron beams converged by the converging lenses 12a and 12b have an unnecessary spread portion, the unnecessary spread portion is cut by the convergent lens stop 13.

  A deflection coil 14 and a scanning coil 15 are disposed below the convergent lens stop 13. The deflection coil 14 is composed of, for example, two sets of coils arranged in directions orthogonal to each other, and performs axis alignment of the electron beams converged by the converging lenses 12a and 12b in accordance with signals from the control unit 10.

  The scanning coil 15 refracts the electron beam according to the signal from the control unit 10 so that the electron beam probe scans the surface of the sample 20 mounted on the sample mounting unit 19.

  Below the scanning coil 15, a spherical aberration / astigmatism correction unit 16, a secondary electron detector 17, objective lenses 18 a and 18 b, a sample mounting unit 19, and an upper electron beam detector 21 are arranged.

  The sample 20 is mounted on the sample mounting portion 19 and is disposed at a substantially middle position (center position) between the objective lenses 18a and 18b separated in the vertical direction. The objective lenses 18a and 18b refract the electron beam so as to be focused on or near the surface of the sample 20 in accordance with a signal from the control unit 10. The spherical aberration / astigmatism correction unit 16 corrects the spherical aberration and astigmatism of the objective lenses 18a and 18b in accordance with a signal from the control unit 10. The secondary electron detector 17 detects secondary electrons emitted from the sample 20 by irradiation with an electron beam. Note that the spherical aberration / astigmatism correction unit 16 and the secondary electron detector 17 may be disposed as necessary, and are not essential components in the present invention.

  The sample mounting portion 19 is disposed so as to be movable in the lateral direction. As will be described later, when observing the STEM image, the sample 20 mounted on the sample mounting portion 19 is arranged in the electron beam passage area, and when measuring the electron beam probe shape, the sample mounting portion 19 moves in the lateral direction, and instead the upper electron The line detector 21 is disposed in the electron beam passage area. As the upper electron beam detector 21, for example, a Faraday gauge or the like can be used.

  A plurality of stages (three stages in FIG. 1) of imaging lenses 22a, 22b, and 22c are arranged below the sample mounting portion 19 and the objective lenses 18a and 18b. In the present embodiment, two modes are set for the imaging lenses 22a, 22b, and 22c. One is a diffraction image mode (electron microscope image acquisition mode) used during STEM image observation, and the other is a real image mode (electron beam shape measurement mode) used during electron beam probe shape measurement. The change from the diffraction image mode to the real image mode and the change from the real image mode to the diffraction image mode are performed by switching the lens conditions of the imaging lenses 22a, 22b, and 22c, that is, the current supplied to the imaging lenses 22a, 22b, and 22c. This is done by changing

  In the present embodiment, it is assumed that the imaging lenses 22a, 22b, and 22c have a function of varying in the range of 10,000 to 40,000 times as a real image and 2 cm to 100 cm as a diffraction image. The diffraction image mode and the real image mode will be described later.

  Below the imaging lenses 22a, 22b, and 22c, a shutter 23, a fluorescent plate 24, a lower electron beam detector 25, a CCD camera 26, a STEM detector 27, and the like are arranged. The shutter 23 is provided to prevent the electron dose from being saturated when the CCD camera 26 images the shape of the electron beam probe. The shutter 23 is retracted to the side when observing the STEM image, and is disposed in the electron beam passage area when measuring the shape of the electron beam probe. In this case, it is conceivable to use a beam blank type shutter, but in the beam blank type shutter, a blur appears in the shape of the electron beam probe taken. Therefore, as the shutter 23, it is preferable to use a mechanical shutter instead of a beam blank shutter.

  The fluorescent plate 24 generates fluorescence by electrons and is used for confirmation of an electron beam. The fluorescent plate 24 is disposed so as to be movable in the lateral direction. As will be described later, when the focus of the imaging lenses 22a, 22b, and 22c is adjusted, the lower electron beam detector 25 is disposed in the electron beam passage area instead of the fluorescent plate 24. As the lower electron beam detector 25, a Faraday gauge or the like can be used as in the upper electron beam detector 21.

  Under the fluorescent plate 24, a CCD camera 26 for photographing an electron beam probe shape is arranged. The CCD camera 26 moves to the side so as to be out of the electron beam passage area during STEM image observation. Instead of the CCD camera 26, an electron beam probe shape may be obtained using an imaging plate or a photosensitive film.

  The STEM detector 27 is used during STEM image observation. The STEM detector 27 has a ring shape and detects transmitted electrons scattered by the sample 20 at a large angle. The control unit 10 processes the signal output from the STEM detector 27 to create a STEM image. Then, a deconvolution process is performed on the STEM image to remove the false image.

  Hereinafter, before describing the electron beam shape measuring method according to the embodiment of the present invention, preliminary matters for facilitating understanding of the present invention will be described.

  FIG. 2 is a diagram showing a result of obtaining a HAADF-STEM high-resolution image using a Si (011) crystal as a sample and performing a deconvolution process. Here, FIG. 2A shows the intensity distribution of the electron beam probe before deconvolution and the intensity distribution of the electron beam probe after deconvolution, with the position on the horizontal axis and the intensity on the vertical axis. ing. FIG. 2B shows a simulation image before and after deconvolution, and FIG. 2C shows a HAADF-STEM image before and after deconvolution.

  In the deconvolution process, as shown in FIG. 2A, the influence of the finite electron beam probe shape superimposed on the electron microscope image is removed, and the electron beam probe shape is calculated as a delta function. 2B and 2C, a false image (a bright spot with low brightness) appears in a portion where no interatomic atoms exist before deconvolution, but the false image is removed by the deconvolution process. I understand that.

  Next, the operation mode of the imaging lens will be described. In the present invention, the shape of the electron probe is measured by changing the operation mode of the imaging lenses 22a, 22b, and 22c. FIG. 3 is a schematic diagram showing an imaging system of a TEM (transmission electron microscope), and FIG. 4 is a schematic diagram showing an imaging system of a STEM (scanning transmission electron microscope). 3, reference numerals 31a and 31b denote objective lenses (corresponding to the objective lenses 18a and 18b in FIGS. 1 and 4), and reference numerals 32a, 32b and 32c denote imaging lenses (the imaging lens 22a in FIGS. 1 and 4). , 22b and 22c), and 33 indicates a sample (corresponding to the sample 20 in FIGS. 1 and 4). 3 and 4, reference numeral 34 denotes an image plane.

  As shown in FIG. 3, in the TEM, an image is acquired by enlarging an image at the sample surface, that is, the center position of the objective lenses 31a and 31b, with the imaging lenses 32a, 32b, and 32c. On the other hand, in the STEM, as shown in FIG. 4, an image is acquired by irradiating the sample 20 with a very finely focused electron beam and imaging the diffraction intensity at each point of the sample 20. The imaging lenses 22a, 22b, and 22c of the STEM project a diffraction image on the imaging surface.

  In other words, since the STEM imaging system does not project a real image, the electron beam shape cannot be directly evaluated. Further, as shown in FIGS. 3 and 4, it has been found that the TEM sample position and the STEM sample position are not necessarily the same, and are almost always different. In the electron beam apparatus (STEM) according to the present embodiment, as shown in FIG. 4, an operation mode for setting lens conditions so that the imaging lenses 22 a, 22 b, and 22 c project a diffracted image onto the imaging surface 34, This is called diffraction image mode.

  FIG. 5 shows lens conditions of the imaging lenses 22a, 22b, and 22c in the real image mode of the electron beam apparatus (STEM) according to the present embodiment. As shown in FIG. 5, in the real image mode, the lens conditions of the imaging lenses 22a, 22b, and 22c are set so that the electron beam probe shape on the sample surface at the time of acquiring the STEM image can be directly observed on the imaging surface.

  In the diffraction image mode, the scanning probe 15 scans the electron beam probe. In the real image mode, the scanning coil 15 is fixed at the scanning center position while being excited. The magnification of the imaging lenses 22a, 22b, and 22c is, for example, 15,000 to 40,000 times. In addition, although it is necessary to calibrate the scale for measuring the electron beam probe shape, the scale is calibrated using a single crystal having a known lattice spacing such as gold or Si.

  In the present embodiment, as described above, the shape of the electron beam probe is measured by setting the STEM imaging lenses 22a, 22b, and 22c to the real image mode. In this case, if conditions other than the operation modes of the imaging lenses 22a, 22b, and 22c change, the conditions at the time of STEM image acquisition and those at the time of electron beam probe measurement differ, and a false image is generated even when the deconvolution processing is performed. It can no longer be removed. Therefore, it is important to match the conditions other than the imaging lens operation mode at the time of electron beam probe shape measurement and STEM image acquisition.

  FIG. 6A is a diagram showing an electron beam probe shape (intensity distribution) obtained by simulation calculation based on conditions at the time of STEM image observation. FIG. 6B is a diagram showing an electron beam probe shape (intensity distribution) directly measured by an experiment. In FIGS. 6A and 6B, the electron beam probe shape when the focus shift amount is from −30 nm to −80 nm is obtained. Note that the STEM image observation conditions are an acceleration voltage of 200 kV, an irradiation angle of 12 mrad, and a spherical aberration coefficient of 1 mm.

  The shape and strength of the electron beam probe vary depending on the amount of defocus due to the influence of spherical aberration of the electromagnetic lens. As shown in FIGS. 6A and 6B, the shape of the electron beam probe obtained by simulation calculation (FIG. 6A) and the shape of the electron beam probe obtained by actual measurement (FIG. 6B) Are very different. The amount of current of the electron beam probe depends on the amount of focus deviation. When the entire intensity is integrated, the amount of current becomes maximum when the amount of focus deviation is −65 nm, and the half-value width at the center of the probe (effectively effective probe region) ), The current amount becomes the maximum value when the focus shift amount is −50 nm (Shelzer focus). FIG. 7 collectively shows the relationship between the focus value (focus shift amount) and the integrated value of electron beam intensity (overall and half width). The focus dependency of the integrated value of the beam intensity has the same tendency between the calculation result and the actual measurement result.

  FIG. 8 is a schematic diagram showing the relationship between the focus position of the electron beam probe and the electron dose. As shown in FIG. 8, the current density is maximized when the focus is in the optimum state, and the current density is small in both underfocus and overfocus. As shown in FIG. 7, the relationship between the focus value and the amount of current is maximum when the focus value is −65 nm when integrated over the entire electron beam probe, and when the focus value is −50 nm when integrated over the half-value width. Maximum. That is, the current amount takes the maximum value when the focus value is −65 nm, but it is better to define the Scherzer focus that is the highest resolution. Therefore, in this embodiment, the position where the current amount becomes the maximum when the half-value width is integrated. Is the optimum focus position.

  FIG. 9 is a schematic diagram showing the concept of the electron beam probe shape measuring method in the present embodiment. First, the objective lenses 18a and 18b are driven under preset conditions to adjust the focus at the sample position. That is, the upper electron beam detector 21 is inserted into the sample position, and the focus is adjusted so that the amount of current detected by the upper electron beam detector 21 (the amount of current when integrated with the half width) is maximized. At this time, in normal TEM observation, the lens conditions of the objective lens are finely adjusted to achieve focusing. However, if the lens conditions of the objective lens are changed, the electron beam incident conditions change, and a false image is generated even after the deconvolution process. It cannot be removed. Therefore, without changing the electron beam incident condition, the position in the height direction of the upper electron beam detector 21 is adjusted and the position where the current amount is maximized when the half-value width is integrated is searched for as the focus position. At the time of STEM image observation, this focus position becomes the sample insertion position. After the focus position is determined, the upper electron beam detector 21 is retracted to the side.

  Next, the focus positions of the imaging lenses 22a, 22b, and 22c in the real image mode are adjusted. That is, the lower electron beam detector 25 is inserted at the position of the imaging plane, and the amount of current detected by the lower electron beam detector 25 (integrated with the half-value width is integrated without changing the lens conditions of the objective lenses 18a and 18b. The lens conditions of the imaging lenses 22a, 22b, and 22c are changed so that the current amount of the current is maximized. When the lens conditions (lens conditions in the real image mode) of the imaging lenses 22a, 22b, and 22c that maximize the amount of current detected by the lower electron beam detector 25 are determined, the lower electron beam detector 25 is retracted to the side. .

  After the focus adjustment of the objective lenses 18a, 18b and the imaging lenses 22a, 22b, 22c is completed in this way, an electron beam shape is photographed using the CCD camera 26 (or an imaging plate or film). At this time, as described above, the mechanical shutter 23 is used so that the electron dose is not saturated. FIG. 10A shows the shape of the electron beam probe actually photographed, and FIG. 10B shows the two-dimensional intensity profile of the electron beam shape (two-dimensional at the position indicated by the dashed arrow in FIG. 10A). (Measurement profile) is shown.

  Although FIG. 10B shows an example of measuring a two-dimensional intensity profile, a three-dimensional intensity profile may be measured. FIG. 11 shows an example of a three-dimensional intensity profile. In FIG. 11, when the acceleration voltage is 200 kV, the electron beam incident angle is 12 mrad, and the amount of focus deviation is −30 nm (FIG. 11A), −50 nm (FIG. 11B), and −70 nm. The three-dimensional intensity profile of the electron beam intensity of (FIG.11 (c)) is shown.

  Next, an image processing method according to an embodiment of the present invention will be described with reference to the flowchart shown in FIG. In FIG. 12, steps S11 to S20 are steps for measuring the shape of the electron beam probe, and overlap with the method for measuring the shape of the electron beam probe described above. Steps S21 to S26 are steps for obtaining a STEM image and removing the false image by deconvolution processing. In the following description, the configuration diagram of the electron beam apparatus of FIG. 1 is also referred to.

  First, in step S11, measurement conditions are set. For example, the acceleration voltage of the electron beam is 200 kV and the irradiation angle is 12 mrad. Further, the enlargement magnification is set to 15,000 to 40,000 times.

  Next, in step S12, the optical axis of the electron beam is adjusted and the incident condition of the electron beam is fixed. That is, the scanning coil 15 is fixed at the scanning center position while being excited. Further, the lens conditions of the objective lenses 18a and 18b are fixed. The electron beam incident conditions (experimental conditions) are stored in the control unit 10.

  Next, in step S13, the upper electron beam detector 21 is inserted at the sample position. In steps S14 and S15, the position of the upper electron beam detector 21 is moved in the vertical direction to search for a position where the maximum current can be obtained. When the position where the maximum current can be obtained is determined, the process proceeds from step S15 to step S16, and the position where the maximum current can be obtained is set as the sample insertion position during STEM image observation.

  Next, the process proceeds to step S17, and the lower electron beam detector 25 is inserted at the position of the imaging surface of the imaging lenses 22a, 22b, and 22c. In steps S18 and S19, the lens conditions of the imaging lenses 22a, 22b, and 22c are adjusted so that the current value detected by the lower electron beam detector 25 is maximized.

  When the adjustment of the imaging lenses 22a, 22b, and 22c is completed in this way, the process proceeds from step S19 to step S20. In step S <b> 20, the electron beam probe shape is photographed by the CCD camera 26, and this image data is input to the control unit 10. The control unit 10 performs image processing on the image data to measure the electron beam probe shape (see FIGS. 10 and 11).

  After the electron beam probe shape measurement is thus completed, the upper electron beam detector 21, the shutter 23, the lower electron beam detector 25, and the CCD camera 26 are retracted from the electron beam passage area.

  Next, the process proceeds to step S21. In step S21, the sample 20 is mounted on the sample mounting portion 19 and inserted into the sample insertion position determined in step S16. Thereafter, in step S22, the control unit 10 switches the imaging lenses 22a, 22b, and 22c to the diffraction image mode, and the electron gun 11, the converging lenses 12a and 12b, the deflection coil 14, the scanning lens 15, the objective lenses 18a and 18b, and the like. The STEM detector 27 acquires image data of the STEM image. The STEM image data acquired by the STEM detector 27 is input to the control unit 10.

  Next, in step S23, the control unit 10 performs deconvolution calculation. At this time, the control unit 10 reads out the measurement result of the electron beam probe shape measured in step S20 and the incident condition of the electron beam and uses them as parameters at the time of deconvolution calculation.

  Next, after the deconvolution process is completed, the analysis image (STEM image after the deconvolution process) is verified in step S24, and the presence or absence of a false image is determined in step S25. If there is a false image, the electron beam incident condition (for example, focus value) may be different from the actual condition. In this case, the process returns to step S23, and the deconvolution calculation is performed again by slightly changing the electron beam incident condition. If it is determined in step 25 that there is no false image, the process proceeds to step S26. In this way, a STEM image from which the false image is removed is obtained.

  In the present embodiment, the lens conditions of the imaging lenses 22a, 22b, and 22c are adjusted to actually measure the shape of the electron beam probe, and the STEM image acquired by the STEM detector 27 is deconvoluted using the result, and the STEM Remove false images from the image. Thereby, a false image can be removed appropriately and an accurate atomic image can be obtained.

  In the above-described embodiment, the example in which the present invention is applied to the STEM has been described. However, the present invention can also be applied to measurement of an electron beam probe shape of an electron beam processing apparatus that processes a sample with an electron beam. it can.

FIG. 1 is a schematic diagram showing a configuration of an electron beam apparatus according to an embodiment of the present invention. 2A shows the intensity distribution of the electron beam probe before deconvolution and the intensity distribution of the electron beam probe after deconvolution, and FIG. 2B shows the simulation images before and after deconvolution. FIG. 2C shows a HAADF-STEM image before deconvolution and after deconvolution. FIG. 3 is a schematic diagram showing a TEM imaging system. FIG. 4 is a schematic diagram showing the STEM imaging system (diffraction image mode). FIG. 5 is a schematic diagram showing the STEM imaging system (real image mode). 6A is a diagram showing an electron beam probe shape (intensity distribution) obtained by simulation calculation based on conditions at the time of STEM image observation, and FIG. 6B is an electron beam probe shape (intensity) directly measured by an experiment. It is a figure which shows distribution. FIG. 7 is a diagram collectively showing the relationship between the focus value and the integrated value of the electron beam intensity (overall and half width). FIG. 8 is a schematic diagram showing the relationship between the focus position of the electron beam probe and the electron dose. FIG. 9 is a schematic diagram showing the concept of the electron beam probe shape measuring method in the embodiment. FIG. 10A is a diagram showing the shape of an electron beam probe actually photographed, and FIG. 10B is a diagram showing a result of measuring a two-dimensional intensity profile of the electron beam shape. 11A, 11B, and 11C are diagrams showing electron beam-shaped three-dimensional intensity profiles. FIG. 12 is a flowchart showing an image processing method according to the embodiment of the present invention.

Explanation of symbols

10 ... control unit,
11 ... electron gun,
12a, 12b ... convergent lens,
13 ... Convergent lens aperture,
14: deflection coil,
15 ... scanning coil,
16: Spherical aberration / astigmatism correction unit,
17 ... Secondary electron detector,
18a, 18b, 31a, 31b ... objective lens,
19 ... Sample mounting part,
20, 33 ... sample,
21 ... Upper electron beam detector,
22a, 22b, 22c, 32a, 32b, 32c ... imaging lens,
23 ... Shutter,
24 ... fluorescent screen,
25. Lower electron beam detector,
26 ... CCD camera,
27 ... STEM detector,
34: Imaging plane.

Claims (5)

An electron beam apparatus capable of measuring the shape of an electron beam irradiated on a sample,
An electron beam source that outputs an electron beam;
An objective lens that focuses the electron beam output from the electron beam source on the sample position;
A scanning coil disposed between the electron beam source and the objective lens and capable of scanning the electron beam along the surface of the sample disposed at the sample position ;
An imaging lens for imaging an electron beam that has passed through the sample position on an imaging plane;
A first electron beam detector disposed at the sample position during electron beam shape measurement;
A second electron beam detector disposed at the position of the imaging plane during the electron beam shape measurement;
An imaging unit that is arranged at or near the imaging plane during the electron beam shape measurement and images the electron beam shape;
Controls the electron beam source, the objective lens, the scanning coil, and the imaging lens, and inputs signals output from the first electron beam detector, the second electron beam detector, and the imaging unit. A control unit ,
An electron microscope image acquisition unit that detects electrons transmitted through the sample and acquires an electron microscope image;
The control unit includes an electron beam shape measurement mode for measuring an electron beam shape, and an electron microscope image acquisition mode for acquiring the electron microscope image. In the electron beam shape measurement mode, the electron beam shape at the sample position is determined by the electron beam shape measurement mode. The imaging lens is controlled to project onto the imaging unit, and in the electron microscope image acquisition mode, the first electron beam detector, the second electron beam detector, and the imaging unit are moved from the electron beam passband. An electron beam apparatus characterized by controlling the imaging lens so as to retract and project a diffraction image of the sample onto the electron microscope image acquisition unit . The electron beam apparatus according to claim 1 , wherein the control unit performs a deconvolution process on the electron microscope image acquired by the electron microscope image acquisition unit according to the shape of the electron beam captured by the imaging unit. The control unit moves the first electron beam detector along the moving direction of the electron beam at the time of measuring the electron beam shape, and the current density detected by the first electron beam detector is maximized. 3. The electron beam apparatus according to claim 1 , wherein the position is searched. In an electron beam shape measuring method of an electron beam apparatus, comprising: an objective lens that focuses an electron beam output from an electron beam source on a sample position; and an imaging lens that forms an electron beam that has passed through the sample on an imaging surface ,
Disposing a first electron beam detector at a focal position of the objective lens and moving the first electron beam detector to search for a position where the current density is maximized;
The first electron beam detector is retracted from the electron beam passage area, a second electron beam detector is disposed on the imaging surface of the imaging lens, and is detected by the second electron beam detector. Adjusting the lens conditions of the imaging lens so that the current density of the electron beam is maximized;
And a step of retracting the second electron beam detector from an electron beam passage area and measuring an electron beam shape on an imaging surface of the imaging lens. An image processing method comprising: deconvolving an electron microscope image using the electron beam shape measured by the electron beam shape measuring method according to claim 4 and removing a false image from the electron beam microscope image.

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