JP4726048B2 - Observation method using phase recovery electron microscope - Google Patents

Description

  The present invention relates to an electron microscope apparatus that obtains an enlarged image by irradiating a sample with an electron beam and detecting electrons transmitted through the sample, and more particularly to an observation technique using a phase recovery type electron microscope.

  The main technologies for high resolution electron microscopes are a method of observing a high-resolution real image by removing the aberration of the objective lens, which is a factor limiting the resolution, by the electron optical system hardware technology, and an electron diffraction image of the sample. There are two methods of obtaining a high-resolution real image by performing arithmetic processing with a phase recovery algorithm using the condition of zero potential outside the sample. The former technique is shown, for example, in “Journal of Electron Microscopy, Vol. 48, p. 821-826 (1999)”. The latter technique is shown, for example, in “SCIENCE Vol. 300, p. 1419-1421 (2003)”.

  The latter technique is illustrated in FIG. For example, when the sample is a crystalline fine particle, an electron diffraction image (inverse space constraint condition) of the fine particle as shown in FIG. 1A is obtained by the electron diffraction image mode of the electron microscope. The shape of the fine particles is observed by some observation method, and data having zero potential on the outside of the fine particles as shown in FIG. 1B is obtained. FIG. 1B shows the potential distribution outside the fine particles (actual space constraint condition). In the figure, the white portion indicates the shape of the fine particle and the black portion indicates zero potential. Using these as input data, the computer calculates the phase-recovered reproduced image by a program using a phase-recovery algorithm. As a result, a high-resolution real image (phase recovery reproduction image) of the fine particles as shown in FIG. 1C is obtained, and the atomic arrangement becomes visible.

The phase recovery algorithm is shown in FIG. When the structure (potential distribution) of the sample in real space is ρ _t , the Fourier transform (FT) of it is
f = | f (K) | e ^{iφ (K)}
It can be expressed. Here, f (K) and φ (K) are the amplitude and phase in the K space (inverse space). If f is subjected to inverse Fourier transform, the original sample structure ρ _t is obtained.

When the sample is irradiated with an electron beam in an electron microscope, an electron diffraction image is formed on the back focal plane of the objective lens, which corresponds to | f (K) | ² . That is, only amplitude information of the periodic structure constituting the sample is included, and phase information is lost. However, the electron diffraction image includes high-frequency periodic structure information that exceeds the resolution of the real image of the electron microscope. On the other hand, the real image observed with the electron microscope is an image formed on the real image plane of the objective lens enlarged by the subsequent lens, and corresponds to the projected image of ρ _t . However, the resolution of a real image is limited by the aberration of the objective lens, the wavelength of transmission, the energy width, and the like. Furthermore, disturbance effects such as sample drift, vibration, and magnetic field during measurement are added, and the resolution of the recorded real image is determined. As a result, fine structure information beyond that resolution is lost. Therefore, if the phase information of the electron diffraction image can be recovered, it may be possible to reproduce a real image having a resolution higher than the resolution of the real image of the electron microscope or the resolution of the recorded image by performing inverse Fourier transform.

The procedure for obtaining a high-resolution real image by phase recovery using the electron diffraction image of the sample observed with an electron microscope and the sample outline obtained by some observation method and the data with the outside of the sample as zero potential is as follows. become. First, a random structure ρ ₀ is assumed as an initial value of the sample structure ρ _t , and f is obtained by Fourier transforming it. A value | f ′ (K) | obtained from the intensity distribution of the electron diffraction image is substituted as an inverse space constraint condition into the amplitude | f (K) | of f. With this, f
f '= | f' (K) | e ^{iφ (K)}
It becomes. This is subjected to inverse Fourier transform to obtain ρ ′ _t in which the phase of the sample structure has been recovered. Next, data with zero potential on the outside of the sample and the outside of the sample is substituted as a real space constraint condition. This speeds up the recovery of the phase information. In this way, a real image of the sample is reproduced. This as a new ρ _t repeat the above operation. The criterion for the end of the operation is that the value obtained by dividing the sum of the intensities of the regions where the sample does not exist in the reproduced real image divided by the total number of pixels constituting the real image converges.

  An electron diffraction image which is a constraint condition of the inverse space is measured as follows. First, when calculating a phase recovery reproduction image by a program using a phase recovery algorithm, there are conditions on the electron diffraction image that can be handled and the data size in which the outside of the sample is zero potential. Therefore, as shown in FIG. 3, it is necessary to make the diameter of the electron beam 1 irradiated to the electron beam irradiation area | region 2 of the sample 3 smaller than the case of normal observation. The maximum allowable electron beam diameter is obtained by dividing the product of the wavelength of the electron beam and the camera length of the electron diffraction image by the size of one pixel of the imaging device. When an imaging plate (number of pixels: 3200 × 4000, pixel size: 25 × 25 μm) is used as the imaging device, the acceleration voltage of the electron beam is 200 kV (wavelength: 0.0025 nm), and the camera length is 1 m, The maximum electron beam diameter is 100 nm. In order to observe a sharp electron diffraction image, a parallel electron beam must be irradiated. In order to satisfy these, in the prior art, the observation is performed by the electron optical path shown in FIG.

  Below, the measuring method of the electron diffraction image by a prior art is demonstrated using FIG.4 (b). In the prior art, a transmission electron microscope (TEM) is used among electron microscopes. The transmission electron microscope includes an electron gun 4, a condenser aperture 5, an irradiation lens 6, an objective lens (front magnetic field) 7, an objective lens (rear magnetic field) 8, an intermediate lens 9, a projection lens 10, and an image sensor 11. In normal observation, the electron beam 1 is expanded by the irradiation lens 6 in order to irradiate an electron beam parallel to a wide region (on the order of microns) of the sample. On the other hand, in the prior art, as shown in FIG. 4B, the electron beam 1 is converged by the irradiation lens 6 so as to have a small electron beam diameter. However, since the electron beam is not parallel at this stage, the converged electron beam is made parallel using the objective lens (front magnetic field) 7 in a strong excitation state, and the sample 3 (indicated by a black arrow in the figure) is used. An electron beam irradiation region (region of interest) 2 (indicated by a white arrow in the figure) is irradiated. The size of the electron beam irradiation region 2 is determined by the acceleration voltage of the electron gun 4, the electron emission method, the hole diameter of the condenser aperture 5, the excitation conditions of the irradiation lens 6 and the objective lens (front magnetic field) 7, and the like. The diameter can be several tens of nm. An electron beam transmitted after being scattered or diffracted inside the sample is imaged by an objective lens (rear magnetic field) 8, an intermediate lens 9, and a projection lens 10. In the electron diffraction image mode shown in FIG. 4B, the electron diffraction image 12 in the electron beam irradiation region is observed.

  Moreover, although not specified in the prior art, there is a real image mode shown in FIG. 4A as an observation mode of a normal transmission electron microscope. In this mode, the real image 13 of the electron beam irradiation region can be observed. In both modes, the excitation conditions of the intermediate lens 9 and the projection lens 10 are different. That is, (a) in the real image mode, the real image 13 of the electron beam irradiation area formed on the real image surface below the objective lens (rear magnetic field) 8 is enlarged by the intermediate lens 9 and the projection lens 10. (B) In the electron diffraction image mode, the electron diffraction image 12 of the electron beam irradiation region formed on the diffraction image surface (rear focal plane) below the objective lens (rear magnetic field) 8 is magnified by the intermediate lens 9 and the projection lens 10. (Camera length is variable).

Journal of Electron Microscopy, Vol. 48, p. 821-826 (1999) SCIENCE Vol. 300, p. 1419-1421 (2003)

  When observing a real image and an electron diffraction image, brightness and uniformity thereof are important in addition to the condition that the electron beam applied to the sample is a minute diameter and parallel. Brightness affects the exposure time when recording a real image or electron diffraction image with an imaging device and the operability when searching for the observation field of view of a sample. When the electron beam is dark and the exposure time is long, there is a problem that the damage to the sample due to the electron beam irradiation and the observation visual field shift due to the sample drift occur, and the reliability and accuracy of the data are lowered. In addition, the efficiency of searching for a field of view decreases with a dark electron beam. The uniformity affects the brightness unevenness of the observed real image, and gives a contrast independent of the sample structure. Therefore, there is a possibility that the accuracy of the sample structure that is phase-recovered by using the real image and the sample outline determined from the real image and data with the sample outside as the zero potential may be lowered.

  In the prior art electron optical path, the condenser aperture 5 having a small hole diameter of about 10 μm is used to reduce the electron beam diameter, so that the electron beam inevitably becomes dark. In addition, since the entire irradiation area with an electron beam narrowed to a diameter of several tens of nanometers is photographed, the intensity distribution (Gaussian distribution) of the electron beam is reflected in the real image, and the periphery of the irradiation area becomes dark, and the small pore diameter In other words, the periphery of the irradiated region may have an intensity distribution due to the influence of Fresnel fringes caused by electrons scattered or reflected by the condenser aperture.

  In view of the above-mentioned problems, an object of the present invention is to provide an observation technique using a phase recovery method electron microscope that makes a minute diameter and parallel electron beam when measuring a real image and an electron diffraction image bright and uniform intensity distribution. It is to provide.

In order to achieve the above object, the present invention is configured as follows.
(1) When observing a real image using an electron microscope having the function of a scanning transmission electron microscope (STEM) capable of scanning a focused electron beam on the sample, the focused electron beam is sampled. The region of interest is imaged by irradiating the region of interest (electron beam irradiation region) while scanning and displaying the intensity of the transmission electron beam detected by the electron beam detector on the monitor in synchronization with the scanning of the convergent electron beam, When observing an electron diffraction image, a limited field stop having a hole that matches the shape and area of the region of interest is inserted immediately above the sample, and a stationary parallel electron beam passes through the limited field stop and the region of interest of the sample. , And an electron diffraction image formed by a transmission electron beam is detected by an image sensor. Real images and electron diffraction images are recorded on a computer as digital data.
(2) When observing a real image and an electron diffraction image using a general-purpose transmission electron microscope (TEM), the hole diameter of the limited field stop to be inserted into the real image surface of the objective lens is changed to the real image of the objective lens. The product of the magnification on the surface, the wavelength of the electron beam and the camera length is made smaller than the value divided by the size of one pixel of the image sensor. The real image and the electron diffraction image are observed in the TEM real image mode and electron diffraction image mode, respectively, and recorded as digital data in a computer.

  According to the observation method (1) or (2) above, an electron beam irradiation region of several tens of nanometers can be uniformly irradiated with a higher electron dose than in the case of the prior art, so a bright and uniform real image and electron diffraction image Can be measured.

  By processing digital data of the real image and electron diffraction image measured by the method (1) or (2) using a phase recovery algorithm, a real image with higher resolution than the digitally recorded real image can be reproduced.

  Hereinafter, typical configuration examples of the observation method using the phase recovery type electron microscope of the present invention will be listed.

  (1) An electron beam irradiation system for irradiating a sample with an accelerated electron beam converged or parallel, and an imaging system for obtaining an intensity distribution of a real image and an electron diffraction image by detecting the electron beam transmitted through the sample with an imaging device When observing the real image, the focused electron beam is irradiated while scanning the region of interest of the sample, and the transmission electron beam detected by the image sensor is observed. When the region of interest is imaged by displaying the intensity on a monitor in synchronization with the scanning of the convergent electron beam, and the electron diffraction image is observed, a restriction having a hole that matches the shape and area of the region of interest A field stop is inserted immediately above the sample, a stationary parallel electron beam is irradiated to the region of interest of the sample through the limited field stop, and an electron diffraction image formed by the electron beam transmitted through the sample is detected by the imaging device. And wherein the door.

  (2) In the observation method using the phase recovery type electron microscope according to (1), when the real image is observed, a detection angle range of scattered electrons detected by the image sensor is inserted above the image sensor. It is characterized in that it is set using an angle limiting diaphragm.

  (3) An electron beam irradiation system that irradiates a sample with an accelerated electron beam via an objective lens, and an imaging system that detects an electron transmitted through the sample with an imaging device and obtains an intensity distribution of a real image and an electron diffraction image When observing the real image and the electron diffraction image, on the real image surface of the objective lens, the magnification on the real image surface of the objective lens, the wavelength of the electron beam, the camera length, The intensity distribution of the real image and the electron diffraction image is obtained by inserting a limited field stop having a hole diameter smaller than a value obtained by dividing the product of the above by the size of one pixel of the image sensor.

  (4) In the observation method using the phase recovery method electron microscope having the above-described configuration, the data obtained by digitally recording the intensity distribution of the real image and the electron diffraction image by the image sensor or the detection system is processed using a phase recovery algorithm. Thus, a real image having a higher resolution than that of the digitally recorded real image is reproduced.

  (5) In the observation method using the phase recovery method electron microscope having the above-described configuration, the limited field stop is formed of at least one of a focused ion beam, mechanical polishing, and chemical polishing on a metal plate having a thickness that does not transmit an electron beam used for observation. It has a hole processed by any one processing method, and the processed surface of the hole has a smoothness that does not give noise to the intensity distribution of the electron diffraction image.

  (6) In the observation method using the phase recovery method electron microscope of (4), the limited field stop is a first hole used for observation of a real image or an electron diffraction image for processing using the phase recovery algorithm. And the second hole used for normal limited visual field observation, or only the first hole.

  ADVANTAGE OF THE INVENTION According to this invention, the observation technique by the electron microscope of a phase recovery system which makes a minute diameter and parallel electron beam at the time of measuring a real image and an electron diffraction image bright and uniform intensity distribution is realizable.

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

Example 1
FIG. 5 shows an electron optical system and a detection system in the case of observation using a scanning transmission electron microscope (STEM) according to the first embodiment of the present invention. In this embodiment, the optical system of the transmission electron microscope (TEM) shown in FIG. 4 of the prior art is provided with a scanning coil 14, a minute limited field stop 15, a detection angle limit stop 16, and a monitor 17. The difference is that there is no intermediate lens that is an imaging lens and no projection lens. The imaging device 11 in the real image mode shown in FIG. 5A is a semiconductor detector for measuring the electron beam intensity, a detector composed of a scintillator and a photomultiplier, as shown in FIG. 5B. In the case of the electron diffraction mode, it is a detector such as a CCD camera or an imaging tube having two-dimensional pixels.

  In the real image mode shown in FIG. 5A, the electron beam 1 emitted from the electron gun 4 is converged by the irradiation lens 6 and then cut by the condenser aperture 5 only into a portion having a small irradiation angle, and further the objective. A lens (front magnetic field) 7 converges to an electron beam 1 having a sub-nm diameter. The electron beam is irradiated while scanning the electron beam irradiation region (attention region) 2 having a diameter of several tens of nm of the sample 3 by the scanning coil 14.

  FIG. 6A shows an example of the scanning shape of the electron beam in the real image mode. In this case, two-dimensional scanning is performed in the X and Y directions as in the television, but the scanning width in the X direction is controlled to change in the Y direction, and the shape of the focused electron beam scanning region is circular. It is. The electron beam 1 with a small sub-nm diameter has a current on the order of pA (picoampere), but since it is scanned over the sample, it is possible to achieve brighter electron beam irradiation over the entire scanning region than in the prior art. Moreover, since the electron beam having the same intensity is irradiated at any location in the electron beam irradiation region 2, uniform electron beam irradiation can also be achieved.

  The electron beam scattered and transmitted in the electron beam irradiation region 2 shown in FIG. 5A is detected by the image sensor 11 through the objective lens (rear magnetic field) 8. A detection angle limit stop 16 disposed above the image sensor 11 sets a detection angle range of scattered electrons detected by the image sensor 11. Normally, a bright field real image can be obtained by setting a few mrad. The intensity of the electron beam detected by the image sensor 11 is displayed on the monitor 17 in synchronization with the scanning of the scanning coil 14 and imaged. The image magnification is determined by the ratio between the electron beam irradiation region 2 and the display area of the monitor 17. The measured real image is recorded on a computer as digital data.

  In the case of the electron diffraction image mode shown in FIG. 5 (b), the electron beam 1 emitted from the electron gun 4 is spread by the irradiation lens 6, and then cut by the condenser aperture 5 only into a portion having uniform brightness. The In the conventional electron optical path, the condenser aperture 5 having a small hole diameter of about 10 μm is used to reduce the electron beam diameter, so that the electron beam is inevitably dark. However, in the present invention, since it is not necessary to make the electron beam itself thin, the hole diameter of the condenser aperture 5 can be several tens of μm or more, and the electron beam can be brightened. The electron beam that has passed through the condenser aperture 5 is collimated by an objective lens (front magnetic field) 7. The electron beam is not scanned by the scanning coil 14.

  A minute limited field stop 15 is arranged directly above the sample 3 without contacting the sample 3. This diaphragm can be taken in and out from the outside using a drive mechanism. As the material of the diaphragm, for example, a tantalum material having a small structure such as crystal grains is used. The aperture is provided with holes processed by at least one of a focused ion beam, mechanical polishing, and chemical polishing. When processing holes having a diameter of several tens of nm or less, a focused ion beam that can be reduced to the order of nm is effective. The processed surface of the hole is finished smoothly so that the electron beam is not scattered by the unevenness. The shape of the hole coincides with the shape of the electron beam scanning region, that is, the electron beam irradiation region. Therefore, as shown in FIG. 6B, the parallel, stationary, bright and uniform electron beam after being cut by the minute limited field stop 15 is irradiated to the same electron beam irradiation region 2 as in FIG. 6A. The

  The electron beam that is transmitted after being scattered and diffracted in the electron beam irradiation region 2 forms an electron diffraction image on the image sensor 11. The electron diffraction image is formed at a distance infinite with respect to the wavelength of the electron beam. For example, when the wavelength of the electron beam is 0.0025 nm (when the acceleration voltage is 200 kV), from the sample 3 to the imaging device 11. If the effective distance is several tens of centimeters, it can be said that the distance is sufficiently infinite. This distance (camera length) can be freely set because the position of the image sensor 11 is variable by the drive mechanism.

(Example 2)
FIG. 7 shows an electron optical system and a detection system for observation using a transmission electron microscope according to the second embodiment of the present invention. This embodiment has the same basic configuration as that of the optical system of the transmission electron microscope shown in FIG. 4, but a small diameter limited field stop 15 is installed on the real image plane below the objective lens (rear magnetic field) 8. Is different.

  In both the real image mode shown in FIG. 7A and the electron diffraction mode shown in FIG. 7B, the electron beam 1 emitted from the electron gun 4 is only a portion having uniform brightness by the condenser aperture 5. Is cut. In the above-described conventional electron optical path, the condenser aperture 5 having a small hole diameter of about 10 μm was used to reduce the electron beam diameter, so that the electron beam was inevitably dark. However, in the present invention, since it is not necessary to make the electron beam itself thin, the hole diameter of the condenser aperture 5 can be several tens μm or more, and the electron beam can be brightened. The electron beam that has passed through the condenser aperture 5 is spread by the irradiation lens 6, collimated by the objective lens (front magnetic field) 7, and then irradiated on the sample 3. The electron beam transmitted after being scattered and diffracted by the sample 3 is imaged by the objective lens (rear magnetic field) 8 as a real image 21 of the sample on the real image plane and an electron diffraction image on the rear focal plane.

  Here, when the minute diameter limited field stop 15 is installed on the real image plane, in the real image mode, only the field corresponding to the aperture of the diaphragm (real image 20 of the region of interest in the sample) of the sample real image 21 is the minute diameter limited field stop 15. It is magnified by the subsequent imaging lens. That is, when an electron beam passing through the aperture of the aperture is traced in the reverse direction, a region that intersects the sample 3 (region of interest 18 in the sample) is obtained, and an electron beam path equivalent to when only the region is irradiated with the electron beam. become. Similarly, in the electron diffraction image mode, an electron diffraction image 19 of the region of interest in the sample is formed by an electron beam path equivalent to that when the region of interest 18 in the sample is irradiated with an electron beam. Therefore, the irradiation area setting is the same as in the case of the prior art in which the irradiation area is set by making the electron beam thin and parallel, or in the case of the embodiment 1 in which the irradiation area is set by the scanning of the convergent electron beam or the diaphragm just above the sample. This is possible by selecting the hole diameter of the limited field stop 15. This can be equivalent to irradiating a minute region with the parallel, bright and uniform electron beam described above.

  This observation method is the same as the observation method of the real image and the electron diffraction image by the normal limited visual field observation, but in this embodiment, the hole diameter of the minute diameter limited visual field stop 15 is defined as follows.

  A normal limited field stop has a small hole diameter of about 50 μm. In this embodiment, the hole diameter of the minute diameter limited field stop 15 is set to a diameter smaller than a value obtained by dividing the product of the magnification on the real image plane of the objective lens, the wavelength of the electron beam, and the camera length by the size of one pixel of the image sensor. . The magnification of the objective lens is 50 times, the wavelength of the electron beam is 0.0025 nm (acceleration voltage 200 kV), the camera length is 1 m, and the size of one pixel of the image sensor is 25 × 25 μm (commercially available imaging plate with 3200 × 4000 pixels) ), The maximum hole diameter of the minute diameter limited field stop 15 is 5 μm. At this time, the electron beam irradiation region on the sample corresponds to a diameter of 100 nm. If the hole diameter is 5 μm or less, it is too small to be used for normal limited visual field observation. Therefore, as shown in FIG. 8, the holes of the small diameter limited field stop 15 are arranged to have a phase recovery observation hole 22 of 5 μm or less and about 50 μm. The general-purpose holes 23 are arranged.

  In addition, the limited field stop described above is provided with at least one of a focused ion beam, mechanical polishing, and chemical polishing on a metal plate having a thickness that does not transmit an electron beam used for observation, like the limited field stop in the first embodiment. The hole is processed by two processing methods, and the processed surface of the hole is finished to have a smoothness that does not give noise to the intensity distribution of the electron diffraction image.

  As described above in detail, according to the present invention, a minute diameter and parallel electron beam can be made bright and uniform intensity distribution when measuring a real image and an electron diffraction image, and an electron beam exposure time to a sample can be obtained. Shortening and improving the operability of the observation visual field search. Moreover, the uneven brightness of the real image could be reduced. Furthermore, by processing digital data of the real image and electron diffraction image measured by this method using a phase recovery algorithm, it was possible to reproduce a real image with higher resolution and higher accuracy than the measured real image.

The figure explaining the flow which acquires a high-resolution real image by phase recovery from the electron diffraction image of a sample, and the potential distribution outside a sample. The figure explaining the flow of the phase recovery algorithm in real space and reverse space. The figure explaining the electron beam at the time of measuring the electron microscope image used for a phase recovery process, and the electron beam irradiation area | region on a sample. The figure which shows the electron optical path | route for measuring the electron microscope image for phase recovery processes by a prior art. The figure which shows the electron optical path at the time of using the scanning transmission electron microscope which becomes the 1st Example of this invention. The figure explaining the electron beam irradiation method to the sample by the 1st Example shown in FIG. The figure which shows the electron optical path at the time of using the transmission electron microscope which becomes the 2nd Example of this invention. The figure explaining the structural example of the micro diameter limited field stop in the 2nd Example shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electron beam, 2 ... Electron beam irradiation area | region, 3 ... Sample, 4 ... Electron gun, 5 ... Condenser aperture, 6 ... Irradiation lens, 7 ... Objective lens (front magnetic field), 8 ... Objective lens (back magnetic field), 9 DESCRIPTION OF SYMBOLS ... Intermediate lens, 10 ... Projection lens, 11 ... Imaging device, 12 ... Electron diffraction image of electron beam irradiation area, 13 ... Real image of electron beam irradiation area, 14 ... Scanning coil, 15 ... Fine diameter limited field stop, 16 ... Detection Angle limiting diaphragm, 17 ... monitor, 18 ... region of interest in sample, 19 ... electron diffraction image of region of interest in sample, 20 ... real image of region of interest in sample, 21 ... real image of sample, 22 ... hole for phase recovery observation, 23 ... general purpose holes.

Claims (6)

  An electron beam irradiation system that irradiates a sample with an accelerated electron beam converged or parallel, and an imaging system that detects an electron beam transmitted through the sample with an imaging device and obtains an intensity distribution of a real image and an electron diffraction image When observing the real image, the focused electron beam is irradiated while scanning the region of interest of the sample, and the intensity of the transmission electron beam detected by the imaging device is measured. When the region of interest is imaged by displaying it on a monitor in synchronization with the scanning of the convergent electron beam and the electron diffraction image is observed, a limited field stop having a hole that matches the shape and area of the region of interest is provided. Inserting the stationary parallel electron beam directly above the sample, irradiating the region of interest of the sample through the limited field stop, and detecting an electron diffraction image formed by the electron beam transmitted through the sample by the imaging device; Observation method using an electron microscope of the phase retrieval method to symptoms.   2. The observation method using the phase recovery electron microscope according to claim 1, wherein when observing the real image, a detection angle range of scattered electrons detected by the image sensor is inserted above the image sensor. An observation method using an electron microscope of a phase recovery system, characterized in that the setting is made using a diaphragm.   An electron beam irradiation system that irradiates a sample with an accelerated electron beam through an objective lens, and an imaging system that detects an electron transmitted through the sample with an imaging device and obtains an intensity distribution of a real image and an electron diffraction image In the phase recovery type electron microscope, when observing the real image and the electron diffraction image, a product of the magnification of the real image surface of the objective lens, the wavelength of the electron beam, and the camera length is obtained on the real image surface of the objective lens. A phase-recovery type electron beam, wherein an intensity distribution of the real image and the electron diffraction image is obtained by inserting a limited field stop having a hole diameter smaller than a value divided by the size of one pixel of the image sensor. Observation method using a microscope.   The observation method using an electron microscope of the phase recovery method according to claim 1 or 3, wherein the data obtained by digitally recording the intensity distribution of the real image and the electron diffraction image by the imaging device or the detection system is calculated using a phase recovery algorithm. An observation method using an electron microscope of a phase recovery method, wherein a real image having a higher resolution than a digitally recorded real image is reproduced by processing.   The observation method using an electron microscope of the phase recovery method according to claim 1 or 3, wherein the limited field stop is formed on a metal plate having a thickness that does not transmit an electron beam used for observation, by focused ion beam, mechanical polishing, or chemical polishing. A phase recovery system characterized in that it has holes processed by at least one of the processing methods, and the processed surface of the holes has smoothness that does not give noise to the intensity distribution of the electron diffraction image Observation method using an electron microscope.   5. The observation method using an electron microscope of the phase recovery method according to claim 4, wherein the limited field stop includes a first hole used for observation of a real image or an electron diffraction image for calculation processing using the phase recovery algorithm, and a normal aperture. An observation method using an electron microscope of a phase recovery method, characterized by having both of the second holes used in the limited visual field observation or only the first hole.

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