WO2022202586A1

WO2022202586A1 - 3d image observation device and method

Info

Publication number: WO2022202586A1
Application number: PCT/JP2022/012153
Authority: WO
Inventors: 研原田; 茂生森; 宏中島
Original assignee: 国立研究開発法人理化学研究所; 公立大学法人大阪
Priority date: 2021-03-24
Filing date: 2022-03-17
Publication date: 2022-09-29

Abstract

The present invention provides a 3D image observation device and a method therefor that, with respect to a sample or other subject of observation, easily and with high precision determine mutual positional relationships in diffraction patterns or projected images from three directions substantially orthogonal to one other and determine the 3D structure of the sample or other subject of observation. With respect to a sample or other subject of observation, a 3D diffraction pattern matching respective points of maximum intensity for three diffraction patterns of the sample observed along three orientations substantially orthogonal to one another is constructed, and a 3D phase distribution and a 3D amplitude distribution are constructed for the sample or other subject of observation using a 3D Fourier transform phase retrieval iterative calculation method employing the points of maximum intensity as a starting point.

Description

THREE-DIMENSIONAL IMAGE OBSERVATION DEVICE AND METHOD

The present invention constructs a three-dimensional diffraction pattern of an observation sample, and uses the three-dimensional diffraction pattern to construct a three-dimensional image of the sample and three-dimensional information such as the electromagnetic field of the space including the sample and its surroundings for three-dimensional image observation. Regarding technology.

Charged particle beams such as electron beams and ion beams must be propagated in a vacuum, various optical elements in an optical system require an electromagnetic field, and the deflection angle is small. Since there is no beam splitter, it is difficult to prepare a large space for an observation object such as a sample and to construct an effective imaging optical system. Furthermore, there is no optical element in the first place for particle beams without charge such as neutron beams, molecular beams, and heavy particle beams. Therefore, a sample is arranged between the light source and the detector, and projection observation of the scattering/absorption image on the sample by path propagation or observation of the diffraction pattern based on the interference/diffraction effect is carried out. In other words, the particle beam apparatus uses only one path optical system, and the only way to observe the three-dimensional structure (three-dimensional structure) of the sample is to rotate the sample and observe it from multiple directions. The reality is that there is none.

For this reason, tomography, laminography, and other methods are used to measure the three-dimensional structure of an object to be observed, such as a sample. are recorded, and a three-dimensional structure is constructed based on the angular relationship between the images. In these three-dimensional structure measurement methods, as the number of measurement images increases, the amount of information about the sample increases, and a highly accurate three-dimensional constructed image can be obtained. Therefore, various mechanisms have been devised to compensate for changes in position due to rotation of the sample and changes in focus in the optical system.

Among the above particle beam devices, electron microscopes using electron beams are the most advanced in development, and various optical elements such as electron lenses, deflectors, and electron biprisms have been realized, and imaging optics have also been put to practical use. It is Therefore, in the present application, the configuration of an electron beam will be described as a representative of charged particle beams, but the principle of the present invention is common not only to particle beams, but also to wave fields such as electromagnetic waves, and the present application is limited to electron beams. not something to do. Related prior art documents include Patent Documents 1 and 2 and Non-Patent Documents 1-4.

International publication number WO2016/051588 JP 2016-162532 A

Three-dimensional image observation (stereoscopic image observation) of the observation target is performed by taking multiple images while gradually changing the angular relationship between the sample and the irradiation beam (light, X-ray, electron beam, etc.), such as tomography and laminography. are recorded and a three-dimensional structure is constructed based on the angular relationship between the images. In this method, the more images that can be used, the more information about the specimen can be obtained, and the more accurate the three-dimensional constructed image can be obtained. However, it takes a long time to acquire a large number of image data, and for example, biological samples, organic materials, and Li battery materials are exposed to high-energy radiation such as X-rays and electron beams. , there was a problem that the sample itself changed. Moreover, it goes without saying that not only the image data acquisition time but also the time required to perform arithmetic processing on a large number of images after acquisition depends on the number of processed images. Furthermore, in tomography and laminography, for example, information obtained from a rotation angle range of ±70° can be obtained no matter how finely divided the range of ±70° in which the information is obtained. The areas that were not cleared (called missing cones) are the cause of large artifacts. In view of the above problems, there is a prior application (see Patent Literature 1) that realizes acquisition of the maximum data amount (projected images in three mutually orthogonal directions) from the minimum dose amount and proposes a reproduction method thereof.

In the prior application, it was possible to obtain projected images in three directions that are nearly orthogonal, but there was no specific description of how to reconstruct a three-dimensional image from the three image data. . In particular, regarding the method of determining the spatial positions of the three images, it is described that a marker is used, but no specific example is disclosed.

As for the method of using markers, it is possible to track predetermined markers in sequence without difficulty for fine angle changes like conventional tomography. In a real image, the shape and relative positional relationship of an observation object change greatly, and in many cases it is impossible to use only markers, and even if it is possible, the accuracy is low.

Therefore, in the projection images of the sample from three orthogonal directions that can obtain the maximum amount of information with the minimum dose, or in the diffraction pattern, the mutual positional relationship can be determined with high accuracy and ease, and the observation object such as the sample can be determined. It is an object of the present invention to provide an apparatus and method for determining the three-dimensional structure and constructing the three-dimensional phase and amplitude distributions of an object such as the specimen.

In terms of current information processing, conventional methods such as tomography and laminography are deep learning for processing big data, whereas the method of the present invention extracts features from a small amount of data and uses them. It corresponds to sparse modeling that is effectively used. Experimental methods and equipment are practiced based on this concept.

In order to achieve the above object, in the present invention, a new three-dimensional diffraction pattern, that is, a space spanned by three coordinate axes (X, Y, Z) is defined as an XYZ space, and an observation target held in the XYZ space On the other hand, the diffraction pattern of the sample in the X-axis direction is defined as a YZ plane diffraction pattern, and the maximum intensity point of the YZ plane diffraction pattern is defined as the origin of the YZ plane diffraction pattern. The diffraction pattern of the sample is defined as the ZX plane diffraction pattern, the point of maximum intensity of the ZX plane diffraction pattern is defined as the origin of the ZX plane diffraction pattern, and the diffraction pattern of the sample in the Z axis direction is defined as the XY plane diffraction pattern. and a space spanned by three coordinate axes (X', Y', Z') different from the space in which the observation object exists, with the point of maximum intensity of the XY plane diffraction pattern as the origin of the XY plane diffraction pattern. is the X'Y'Z' space, the Y The Z'X' plane is arranged on the 'Z' plane, and the Z'X' plane diffraction pattern is arranged such that the coordinate origin of the Z'X' plane of the X'Y'Z' space coincides with the origin of the ZX plane diffraction pattern. and the XY plane diffraction pattern is arranged on the X'Y' plane such that the coordinate origin of the X'Y' plane of the X'Y'Z' space coincides with the origin of the XY plane diffraction pattern. For a three-dimensional diffraction pattern consisting of three diffraction patterns, the wave transmitted, reflected, or scattered through the observation object is obtained by the Fourier transform phase retrieval iterative calculation method based on the three-dimensional Fourier transform. A three-dimensional image observation apparatus and method characterized by constructing an amplitude distribution and a phase distribution are provided.

According to the present invention, it is possible to construct not only the amplitude term but also the phase term at the same time during the iterative calculation of the three-dimensional Fourier transform phase recovery. Therefore, not only the three-dimensional image of the observation target (the intensity distribution as the square of the amplitude image) but also the phase distribution can be obtained at the same time. This phase distribution is information that could not be observed with a conventional transmission electron microscope, and required special techniques such as electron beam holography. A three-dimensional phase distribution means that physical information carried by each projection phase can be obtained for each orientation and for any combined orientation. For example, when the irradiation beam is an electron beam, a three-dimensional distribution can be obtained from the projection distribution of the spatial electromagnetic field.

1 is a schematic diagram showing the effectiveness of trigonometric projection microscopy (trigonography); FIG. FIG. 4 is a schematic diagram showing the principle of two-dimensional Fourier transform phase retrieval iterative calculation; FIG. 4 is a schematic diagram showing the spatial relationship between three orthogonal directions and respective diffraction patterns according to an example. It is a schematic diagram which shows the three-dimensional diffraction pattern which concerns on an Example. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the electron microscope which is an example of the charged particle beam apparatus which concerns on an Example. FIG. 4 is a schematic diagram showing a method of obtaining a diffraction pattern according to an example; FIG. 4 is a schematic diagram showing a method of obtaining a reflection type diffraction pattern according to an example; FIG. 4 is a schematic diagram showing the principle of the three-dimensional Fourier transform phase retrieval iterative calculation according to the embodiment; FIG. 10 is a schematic diagram showing a three-dimensional Fourier transform phase retrieval iterative calculation method when using an irradiation region as a constraint condition according to an embodiment; FIG. 4 is a schematic diagram showing a three-dimensional Fourier transform phase retrieval iterative calculation method when using an irradiation region and a real space image as constraint conditions according to an embodiment;

Prior to describing the embodiments for carrying out the present invention, the techniques, methods and principles on which the present invention is based will be outlined below.

<Trigonography (triangular projection microscopy)>
It is a method of obtaining projected images from three orthogonal directions, and a method of obtaining a three-dimensional image (stereoscopic image) of an observation target from the three images. It is based on the same principle as the third angle method (Trigonometry) in cartography, and aims to reproduce the three-dimensional structure of an object based on projections from three orthogonal directions. Observations from three orthogonal directions form a data group with the largest amount of information in a three-dimensional space. So to speak, it is a small and effective data group obtained by practicing the concept of sparse modeling.

Figure 1 illustrates the importance of observation from these three orthogonal directions. With stereoscopic observation from two directions like the human eye, the structure of the object of observation in FIG. 1 (the blade shape of a chisel) cannot be known. At the machining site, if design drawings (front view, top view, side view) based on the third angle method are given, the worker can process a three-dimensional structure. This is an attempt to incorporate this idea into microscopy. There is a prior application for the configuration of this method (see Patent Document 1), but in charged particle beam devices such as electron microscopes, a method of obtaining images in three mutually orthogonal directions is technically under development. In addition, it is difficult to secure a common reference point in the three images obtained. The present invention provides a method of avoiding the reference point by using the median section theorem, which will be described later.

<Diffractive Imaging>
It is a method of obtaining a real image from a diffraction pattern. Figure 2 shows the principle of this method. An arbitrary phase distribution is added to the recorded diffraction pattern (only the intensity distribution) to obtain the initial image data F'(X', Y'). Y) (amplitude distribution and phase distribution in real space). After adding constraint conditions (f'(X,Y)) to this, Fourier transform is further performed to obtain a provisional diffraction pattern F(X',Y') (amplitude distribution in Fourier space (reciprocal space) and phase distribution). Constraint conditions in the Fourier space are imposed on this provisional diffraction pattern F(X',Y'), and the next image data F'(X',Y') is calculated again. In this way, the method of alternately performing the above iterative calculations and obtaining a real image (amplitude distribution, phase distribution) as a converged image is the Fourier transform phase recovery iterative calculation method. This was achieved by improving the accuracy of the camera system and increasing the speed of the computer. It is mainly used in the field of image measurement, such as X-ray, which does not have an imaging optical system. It is a technique that is not often used because electron microscopy allows direct observation of real images.

<Central section theorem>
It is the theorem that the Fourier transform of the projected image of a three-dimensional object is the same as a cross section through the origin in the Fourier space of the original object after the three-dimensional Fourier transform. Simply put, the origins of Fourier transform patterns of projected images in three orthogonal directions always coincide. Applying this central section theorem to the diffraction pattern, which is experimental data, the spot on the optical axis where the diffraction pattern is recorded, that is, the point of maximum intensity in the diffraction pattern, is used as the origin, and the Fourier transform phase retrieval iterative calculation method is used. The present invention realizes three-dimensional image observation.

In the following description of the specification and claims, the term "charged particle beam device" collectively refers to devices that use charged particle beams such as electron beams and ion beams. However, the diffraction pattern is widely formed as data in the optical field or used as an element, and is not limited to the charged particle beam. The idea of the present application can be implemented with beams that have coherence to the extent that Bragg diffraction is accompanied by wave motion, and particle beams such as neutron beams, molecular beams, and heavy particle beams, and X-rays, ultraviolet rays, gamma rays, etc. is also realizable in the electromagnetic waves of In addition, since wave propagation including particle beams can be used to form a diffraction pattern, there is no need to construct an imaging optical system in these devices, and the idea of the present application can handle both particle beams and waves. Any device can be implemented widely. Furthermore, the projection images or diffraction patterns from three directions orthogonal to each other mean "almost orthogonal", and in the actual apparatus system, there are restrictions on the accuracy of movement, etc., and the realistic range of "orthogonal" is about 90°±5°, and it should be noted that this degree of fluctuation is within the permissible range of the apparatus and method of the present invention.

A three-dimensional diffraction pattern in the present invention will be described in Example 1. FIG. 3 is a schematic diagram showing the diffraction patterns of a sample placed in space projected from three mutually orthogonal directions. Although a projection diagram is drawn as a diffraction pattern, it is not limited to projection, and a reflection type (see (C) in FIG. 6B) may be used as described later. In addition, as a method of obtaining a diffraction pattern from a projected image, a method using only the propagation of a particle beam or the wave field used ((A) in FIG. 6A: Fraunhofer diffraction) may be used, or an optical system such as an electron microscope may be used. The method ((B) in FIG. 6A) may also be used. Three diffraction patterns 71 obtained in a spatial relationship as shown in FIG. (C) of is the three-dimensional diffraction pattern 72 .

　Fig. 4 shows the relationship between the observed images from the three orthogonal directions and the three-dimensional diffraction pattern. A certain object to be observed is a sample ((A) in FIG. 4), and images observed from three orthogonal directions are shown in the upper part of (B) in FIG. Each observation image may be a transmission image or a reflection image. Diffraction patterns 71 of respective observed images in the upper part of FIG. 4B are shown in the lower part of FIG. 4B. These diffraction patterns, like images, may be transmissive or reflective. A three-dimensional diffraction pattern 72 is shown in FIG.

In this specification, three orthogonal directions are described in view of the efficiency of information acquisition in a three-dimensional space. It corresponds to the missing cone in tomography and laminography), but the basic handling does not change. That is, the diffraction pattern may be placed on a plane substantially perpendicular to the incident beam direction according to the observation direction (incident direction of the incident beam). The extent is estimated to be 90°±5°.

When arranging the three-dimensional diffraction patterns, not only the relative angles of the above arrangement but also the positional relationship must be matched. That is, when the positional relationship between the position of the incident beam and the obtained diffraction pattern is known, three diffraction patterns are arranged according to that information. That is, the points of intersection of the optical axes when each diffraction pattern is obtained are matched. When the positional relationship between the position of the incident ray and the obtained diffraction pattern is unknown or unclear, the diffraction pattern generally obtains the maximum intensity in the azimuth of the incident ray. A point (a minute area) of maximum intensity is found, and three diffraction patterns are arranged so as to use it as an origin.

As described above, the diffraction pattern obtained by matching the directions and positions of the three diffraction patterns is the three-dimensional diffraction pattern 72 ((C) in FIG. 4). In current image processing technology, it is assumed that data is mainly arranged in a virtual space on a computer, which is a computing machine.

FIG. 5 shows a schematic diagram of a configuration example of the entire system of the particle beam device according to this embodiment. The device in FIG. 5 is a charged particle beam device, and is assumed to be a general-purpose electron microscope with an acceleration voltage of about 100 kV to 300 kV. For this purpose, the entire system including an irradiation optical system above the sample, i.e., upstream in the direction of particle beam flow, and an imaging optical system below the sample, i.e., downstream in the direction of particle beam flow, is schematically illustrated. drawing. Furthermore, the tilting and azimuth rotation of the sample 3 are schematically drawn with the sample holding device for performing trigonography in mind.

The reason why the configuration of the transmission electron microscope as a particle beam device is mentioned in this example is that the transmission electron microscope is the most advanced system among the particle beam devices, and it is also widely used in the method of using the device. This is because they have both sexes. For example, if all the lenses of the irradiation optical system (41, 42) are turned off in the system of the charged particle beam device 4 shown in FIG. If the system 5 and the imaging optics (61, 62, 63, 64) are also turned off, the simplest electron diffraction device is obtained. In other words, the device can be constructed in a form that simulates a neutron beam device, a heavy particle beam device, or an X-ray device. However, the present application does not limit the application of this embodiment to the transmission electron microscope having the configuration of FIG.

In FIG. 5, the electron gun 1, which is the particle source, is positioned at the most upstream portion in the electron beam flow direction. After being accelerated to a predetermined speed by 40 , the sample 3 is irradiated with a predetermined intensity and irradiation area through

condenser lenses

41 and 42 of an irradiation optical system controlled by

control units

47 and 48 . Then, the sample is tilted at an arbitrary angle and azimuthally rotated about the optical axis 2 . At this time, trigonography is a technique in which the tilt angle is 35.3° and the azimuth rotation angle is 120° (see Patent Document 1). The electron beam transmitted through the sample 3 is imaged by the objective lens 5 controlled by the control unit 59 . This imaging action is taken over by imaging

lens systems

61, 62, 63, and 64 controlled by

control units

69, 68, 67, and 66 at the rear stage of the objective lens 5, and finally an observation record of the electron beam apparatus. An image of the sample is formed on the plane 75 . In addition, the diffraction pattern of the sample formed directly under the objective lens is taken over by the imaging lens system in the same way as the image of the sample, and finally the diffraction pattern 8 is imaged on the observation recording surface 75 of the electron beam apparatus. The diffraction pattern passes through an image detector 79 such as a CCD camera and an image data controller 78 and is observed on, for example, the screen of an image data monitor 76 or stored as image data in an image data recording device 77 . The image data recorded in the image data recording device 77 is used for processing such as the iterative Fourier transform phase recovery method for three-dimensional image observation. For this image data processing, a dedicated computer can be connected, or the system control computer 52 or the image data controller 78 can be used.

These devices are systematized as a whole, and the operator can confirm the control state of the devices on the screen of the monitor 53. Various programs are executed via the interface 54, and the system control computer 52 functions as a control unit. is used to control the control unit 39 of the sample 3, the control unit 47 of the second irradiation lens 42, the control unit 48 of the first irradiation lens 41, the control unit 49 of the acceleration tube 40, the control unit 59 of the objective lens 5, and the fourth lens. A control unit 66 for the imaging lens 64, a control unit 67 for the third imaging lens 63, a control unit 68 for the second imaging lens 62, a control unit 69 for the first imaging lens 61, a control unit 78 for the image detector 79, etc. By controlling the control unit of , the electron gun 1, the acceleration tube 40, each lens, the sample 3, the image detector 79, etc. can be controlled.

Although the above particle beam system has been described based on a transmission electron microscope, charged particle beam equipment such as ion microscopes, molecular beam equipment, heavy particle beam equipment, neutron beam equipment, and broadly X-rays, etc. You may use it for an electromagnetic wave apparatus. At that time, it goes without saying that the configuration of the optical system is changed based on the characteristics of each device. Many of the assumed particle beam devices are equipped with a particle beam deflection system and a vacuum exhaust system for evacuating the particle beam orbital part, etc., but they are not directly related to the present invention. Therefore, illustration and description are omitted.

As Example 2, creation of a three-dimensional diffraction pattern will be described. (A) of FIG. 6A is a method of observing a diffraction pattern of an object to be observed by propagating an irradiating beam. This is a method known as Fraunhofer diffraction. In general, when the wavelength of the irradiation beam (wave) is λ, the size of the object to be observed is d, and the propagation distance from the sample to the observation recording surface is L, the formula is It is configured to satisfy the condition satisfying 1.

L >> d2/2λ (Formula 1)

For X-ray diffraction, neutron diffraction, heavy particle beam diffraction, etc., it is difficult to configure an optical system using effective optical elements, so this diffraction method based on propagation is the mainstream.

Mathematically, the state in which this L is infinity is the Fourier transform, and a method similar to the present application is realized by performing the Fourier transform as information processing by a computer, which is a computing device, after recording the image of the sample. is possible (described later in Example 5). However, since the image of the sample has already lost the phase information of the particle beam or wave field, it is not a strictly matching method. A technique for experimentally Fourier transforming a sample image is a technique using an imaging optical system ((B) in FIG. 6A), which will be described below.

(B) of FIG. 6A shows a method of forming a diffraction pattern with an optical system located downstream of the irradiation beam from the sample. Strictly speaking, the object to be observed is the front focal position of the lens, and observation is performed at the rear focal position of the lens. is doing. That's enough accuracy.

(C) of FIG. 6B is an example of an electron beam apparatus that obtains a diffraction pattern by reflection (from Non-Patent Document 4). Diffraction pattern observation with reflection type has been put into practical use from early on, such as the back scattering Laue method and the LEED (Low Energy Electron Diffraction) observation method for surface analysis, but the introduction path of the irradiation beam and the irradiation beam source device are observed It was difficult to obtain a diffraction pattern with good symmetry, such as creating shadows in the diffraction pattern. Fig. 6B (C) is an example of solving this problem. By using a hemispherical electrode, a charged particle (in this case, an electron) draws an elliptical trajectory and is imaged at a point different from the scattering point (incident point). It is something to do. As a result, a diffraction pattern can be obtained that is not affected by the irradiation beam introduction path or the irradiation beam source device. An example of experimental results (7×7 superlattice pattern on Si111 surface) is shown in (D) of FIG. 6B (from Non-Patent Document 4).

These diffraction patterns can be recorded not only on the sample but also on any object that scatters and deflects the incident particle beam or wave field, such as the spatial electromagnetic field around the sample. For example, the small-angle electron diffraction pattern illustrated in FIG. 14A of Patent Document 2 obtains a diffraction pattern that reflects the magnetic structure of the sample. From these diffraction patterns it is possible to reconstruct magnetic information, and the present application also contemplates a three-dimensional observation of the spatial electromagnetic field associated around the sample piece.

Next, as Example 3, the procedure for the iterative computation method for Fourier transform phase recovery in three dimensions will be described. It is based on extending the two-dimensional Fourier transform phase recovery iterative calculation method described with reference to FIG. 2 to the three-dimensional diffraction pattern described in the first embodiment.

The method will be briefly explained based on Figure 7.

(1) A three-dimensional diffraction pattern 72 ((C) in FIG. 4 and (A) in FIG. 7) is constructed from three diffraction patterns recorded in three substantially orthogonal directions.

(2) Form a three-dimensional function with the above three-dimensional diffraction pattern (square root of) as the amplitude and an arbitrary phase term added. Let this be a three-dimensional Fourier space (diffraction space) function.

(3) 3D inverse Fourier transform of this 3D Fourier space function to obtain a 3D real space function.

(4) Imposing constraints in the real space on the obtained functions in the three-dimensional real space. As the constraint condition, zero outside the sample image (zero outside the diaphragm aperture) or a separately acquired sample image is used. (Set zero outside the frame of (B) in Fig. 7 (zero outside the sample image), or use the sample image in each direction shown in the upper part of (B) in Fig. 4.)
(5) Three-dimensional Fourier transform is performed on the three-dimensional real space function to which the real space constraint condition is imposed to obtain a three-dimensional Fourier space function.

(6) Impose a Fourier space constraint on the three-dimensional Fourier space function.
(Square root of) of each diffraction pattern is used as a constraint condition. (Do not change the phase term and use it as it is.)
(7) Inverse three-dimensional Fourier transform of the three-dimensional Fourier space function to which the Fourier space constraint condition is imposed.

(8) Repeat (4) to (7) until convergence. (Three-dimensional Fourier transform phase recovery iterative algorithm)
The real space image of the converged image obtained as described above is the real image of the observed sample, and the amplitude distribution and the phase distribution are reconstructed as three-dimensional distributions. As for the diffraction space, the amplitude distribution and phase distribution of the diffraction space are similarly reconstructed.

While performing the above steps (4) to (7), the three-dimensional space, both real space and Fourier space, is filled with data. By using it, the number of iterative calculations can be reduced, and the accuracy of the reconstructed amplitude distribution and phase distribution can be improved.

Next, based on FIG. 8, as a constraint condition in real space, the experimental procedure using the condition of "zero intensity outside the irradiation area", and based on FIG. In addition, the procedure of these methods will be explained from the point of obtaining the diffraction pattern with respect to the conditions for using the "real space image".

(1) Record three diffraction patterns (reciprocal spatial images) in three nearly orthogonal directions (see (B) in Fig. 4). Diffraction patterns can be created by a method using spatial propagation ((A) in FIG. 6A), a method using an optical system ((B) in FIG. 6A, (C) in FIG. 6B), and the like.

(2) The above-described three diffraction patterns in three nearly orthogonal directions are aligned in a three-dimensional reciprocal space (Fourier space) so that the surfaces of each pattern are aligned, the directions are aligned, and the origin is aligned (see FIG. 4). (C)).

(3) A three-dimensional function is formed by taking the (square root of) the above three diffraction patterns as the amplitude and adding an arbitrary phase term. Let this be a three-dimensional Fourier space (diffraction space) function.

(4) 3D inverse Fourier transform of this 3D Fourier space function to obtain a 3D real space function.

(5) Imposing constraints in the real space on the obtained functions in the three-dimensional real space.
As a constraint condition, zero outside the sample image (zero outside the diaphragm aperture) or separately obtained sample images (sample images in each direction shown in the upper part of FIG. 4B) are used.

(6) Perform a 3D Fourier transform on the 3D real space function with the above constraint conditions to obtain a 3D Fourier space function.

(7) Impose a Fourier space constraint on the three-dimensional Fourier space function.
(Square root of) of each diffraction pattern is used as a constraint condition. (Do not change the phase term and use it as it is.)
(8) Inverse three-dimensional Fourier transform of the three-dimensional Fourier space function to which the Fourier space constraint condition is imposed.

(9) Repeat (5) to (8) until convergence. (Three-dimensional Fourier transform phase recovery iterative algorithm)
The real space image of the converged image obtained as described above is the real image of the observed sample, and the amplitude distribution and the phase distribution are reconstructed as three-dimensional distributions. As for the diffraction space, the amplitude distribution and phase distribution of the diffraction space are similarly reconstructed.

As Example 5, a method of aligning the positions of the images in the three-dimensional space using the Fourier transform patterns of the three real images in the three directions described in Example 1 will be described. This is a method based on the central section theorem.

(1) Record three images (real space images) in three nearly orthogonal directions.

(2) Perform a two-dimensional Fourier transform on each of the three recorded images in the three orthogonal directions.

(3) Align the surfaces of the three patterns in the three-dimensional reciprocal space (Fourier space), align the directions, and align the origins (Fig. 4 (C)).

(4) Two-dimensional inverse Fourier transform of each Fourier transform pattern in its respective plane to restore a real image in its respective plane.
The respective real images obtained have appropriate correlations in their positional relationship according to the central section theorem.

(5) Build a three-dimensional real image.
The spatial density (image intensity) on the three-dimensional real space is obtained by arithmetic processing in the real space, such as integration or summation of projected images.

The present invention is not limited to the above-described examples, and includes various modifications. For example, the above embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described.

Furthermore, although the configuration, function, system control computer, etc. described above use a program that implements a part or all of them, a part or all of them can be implemented as hardware by designing them, for example, using an integrated circuit. Needless to say, it can be realized with wear. That is, all or part of the functions of the processing unit may be realized by integrated circuits such as ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array) instead of programs.

1 Electron gun or particle source 8 Diffraction pattern 18 Vacuum vessel 19 Particle source control unit 2 Optical axis 27 Electron beam or particle beam 3 Sample or sample holder 39 Control unit for sample holder 4 Charged particle beam device 40 Acceleration tube 41 Second 1 condenser lens 42 second condenser lens 47 second condenser lens control unit 48 first condenser lens control unit 49 acceleration tube control unit 5 objective lens 52 system control computer 53 system control computer monitor 54 system control computer interface 59 Objective lens control unit 61 First imaging lens 62 Second imaging lens 63 Third imaging lens 64 Fourth imaging lens 66 Fourth imaging lens control unit 67 Third imaging lens control unit 68 Second second Control unit 69 for imaging lens Control unit 71 for first imaging lens Diffraction pattern 72 Three-dimensional diffraction pattern 75 Image or pattern detection surface 76 Image data monitor 77 Image data recorder 78 Image data controller 79 Image detector 8 Sample image or diffraction pattern

Claims

Let the space spanned by the three coordinate axes (X, Y, Z) be the XYZ space,
For the sample to be observed held in the XYZ space,
Let the diffraction pattern of the sample in the X-axis direction be a YZ plane diffraction pattern,
Let the diffraction pattern of the sample in the Y-axis direction be the ZX plane diffraction pattern,
Let the diffraction pattern of the sample in the Z-axis direction be an XY plane diffraction pattern,
When the space spanned by three coordinate axes (X', Y', Z') different from the space in which the observation target exists is defined as an X'Y'Z' space,
the YZ plane diffraction pattern is arranged on the Y'Z' plane of the X'Y'Z'space;
the ZX plane diffraction pattern is arranged in the Z'X' plane of the X'Y'Z'space;
With respect to the three-dimensional diffraction pattern in which the XY plane diffraction pattern is arranged on the X'Y' plane of the X'Y'Z' space, the observation object is subjected to an iterative Fourier transform phase recovery method based on the three-dimensional Fourier transform. A three-dimensional image observation apparatus characterized by constructing an amplitude distribution and a phase distribution of transmitted, reflected, or scattered waves.
The three-dimensional image observation device according to claim 1,
The three-dimensional diffraction pattern is
The point of maximum intensity of the YZ plane diffraction pattern is the origin of the YZ plane diffraction pattern,
The point of maximum intensity of the ZX plane diffraction pattern is the origin of the ZX plane diffraction pattern,
The point of maximum intensity of the XY plane diffraction pattern is the origin of the XY plane diffraction pattern,
the coordinate origin of the Y'Z' plane of the X'Y'Z' space coincides with the origin of the YZ plane diffraction pattern arranged on the Y'Z' plane,
the coordinate origin of the Z'X' plane in the X'Y'Z' space coincides with the origin of the ZX plane diffraction pattern arranged on the Z'X'plane;
The coordinate origin of the X'Y' plane in the X'Y'Z' space coincides with the origin of the XY plane diffraction pattern arranged on the X'Y' plane.
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to claim 1 or claim 2,
The object to be observed is a substance consisting of a metal, a semiconductor, a dielectric, an inorganic substance, an organic substance, or a living body, or an electromagnetic field inherent in the metal, the semiconductor, the dielectric, the inorganic substance, the organic substance, or the living body, or an externally generated magnetic field. is
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to claim 3,
The YZ-plane diffraction pattern, the ZX-plane diffraction pattern, and the XY-plane diffraction pattern are produced by a charged particle beam transmitted or scattered through the observation target.
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to claim 3,
The YZ plane diffraction pattern, the ZX plane diffraction pattern, and the XY plane diffraction pattern are produced by a charged particle beam reflected or scattered by the observation target.
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to claim 3,
After the charged particle beam irradiates the observation target,
The YZ plane diffraction pattern is created by propagating in space in the X-axis direction,
The ZX plane diffraction pattern is created by propagating in space in the Y-axis direction,
The ZX plane diffraction pattern is produced by propagating in space in the Z-axis direction,
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to claim 3,
After the charged particle beam irradiates the observation target,
wherein the YZ plane diffraction pattern is produced by an optical system for the charged particle beam in the X-axis direction;
The ZX plane diffraction pattern is produced by the optical system of the charged particle beam in the Y-axis direction,
The ZX plane diffraction pattern is produced by an optical system of the charged particle beam in the Z-axis direction,
A three-dimensional image observing apparatus characterized by:
The three-dimensional image observation device according to any one of claims 1 to 7,
wherein said iterative Fourier transform phase retrieval method utilizes a processing algorithm based on sparse modeling;
A three-dimensional image observing apparatus characterized by:
Let the space spanned by the three coordinate axes (X, Y, Z) be the XYZ space,
For the sample to be observed held in the XYZ space,
The diffraction pattern of the sample in the X-axis direction is defined as a YZ plane diffraction pattern, and the point of maximum intensity of the YZ plane diffraction pattern is defined as the origin of the YZ plane diffraction pattern,
Let the diffraction pattern of the sample in the Y-axis direction be the ZX plane diffraction pattern, and let the point of maximum intensity of the ZX plane diffraction pattern be the origin of the ZX plane diffraction pattern,
The diffraction pattern of the sample in the Z-axis direction is defined as an XY plane diffraction pattern, and the point of maximum intensity of the XY plane diffraction pattern is defined as the origin of the XY plane diffraction pattern,
When the space spanned by three coordinate axes (X', Y', Z') different from the space in which the observation target exists is defined as an X'Y'Z' space,
The YZ plane diffraction pattern is arranged on the Y'Z' plane such that the coordinate origin of the Y'Z' plane in the X'Y'Z' space coincides with the origin of the YZ plane diffraction pattern,
The ZX plane diffraction pattern is arranged on the Z'X' plane such that the coordinate origin of the Z'X' plane in the X'Y'Z' space coincides with the origin of the ZX plane diffraction pattern,
3-dimensional, in which the XY plane diffraction pattern is arranged in the X'Y' plane such that the coordinate origin of the X'Y' plane of the X'Y'Z' space coincides with the origin of the XY plane diffraction pattern. for the diffraction pattern,
A three-dimensional image observation method, comprising constructing an amplitude distribution and a phase distribution of waves transmitted through, reflected from, or scattered by the observation object by an iterative Fourier transform phase retrieval method based on a three-dimensional Fourier transform.
The three-dimensional image observation method according to claim 9,
In the iterative Fourier transform phase retrieval method,
The constraints imposed on the three-dimensional function in real space are
an irradiation area of the wave on the real image of the sample projected in the X-axis direction with respect to the observation target;
an irradiation area of the wave on the real image of the sample projected in the Y-axis direction with respect to the observation target;
an image of the irradiation area of the wave on the actual sample projected in the Z-axis direction with respect to the observation target;
is one that uses
A three-dimensional image observation method characterized by:
The three-dimensional image observation method according to claim 9,
In the iterative Fourier transform phase retrieval method,
The constraints imposed on the three-dimensional function in real space are
a real image of the sample in the X-axis direction with respect to the sample;
a real image of the sample in the Y-axis direction with respect to the sample;
a real image of the sample in the Z-axis direction with respect to the sample;
is one that uses
A three-dimensional image observation method characterized by:
The three-dimensional image observation method according to any one of claims 9 to 11,
wherein said iterative Fourier transform phase retrieval method utilizes a processing algorithm based on sparse modeling;
A three-dimensional image observation method characterized by:
The three-dimensional image observation method according to any one of claims 9 to 12,
wherein said wave is a charged particle wave;
A three-dimensional image observation method characterized by: