WO2022202586A1 - 3d image observation device and method - Google Patents
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- WO2022202586A1 WO2022202586A1 PCT/JP2022/012153 JP2022012153W WO2022202586A1 WO 2022202586 A1 WO2022202586 A1 WO 2022202586A1 JP 2022012153 W JP2022012153 W JP 2022012153W WO 2022202586 A1 WO2022202586 A1 WO 2022202586A1
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- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
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Definitions
- 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.
- three-dimensional information such as the electromagnetic field of the space including the sample and its surroundings for three-dimensional image observation.
- 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.
- 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.
- a three-dimensional structure measurement method 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.
- 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.
- 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.
- 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.
- the method of using markers it is possible to track predetermined markers in sequence without difficulty for fine angle changes like conventional tomography.
- 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.
- 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
- the diffraction pattern of the sample in the X-axis direction is defined as a YZ plane diffraction pattern
- 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
- 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.
- the X'Y'Z' space is the X'Y'Z' space
- the Y The Z'X' plane is arranged on the 'Z' plane
- 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.
- 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.
- 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.
- 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.
- FIG. 1 is a schematic diagram showing the effectiveness of trigonometric projection microscopy (trigonography);
- 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;
- 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.
- the structure of the object of observation in FIG. 1 cannot be known.
- the worker can process a three-dimensional structure. This is an attempt to incorporate this idea into microscopy.
- a prior application for the configuration of this method see Patent Document 1
- a method of obtaining images in three mutually orthogonal directions is technically under development.
- 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.
- 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.
- 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.
- charged particle beam device collectively refers to devices that use charged particle beams such as electron beams and ion beams.
- 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.
- FIG. 3 is a schematic diagram showing the diffraction patterns of a sample placed in space projected from three mutually orthogonal directions.
- 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.
- 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.
- 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°.
- the diffraction pattern 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.
- 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).
- 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.
- 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.
- the tilting and azimuth rotation of the sample 3 are schematically drawn with the sample holding device for performing trigonography in mind.
- 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.
- the electron gun 1, which is the particle source, is positioned at the most upstream portion in the electron beam flow direction.
- 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 .
- the sample is tilted at an arbitrary angle and azimuthally rotated about the optical axis 2 .
- 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 .
- 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.
- a dedicated computer can be connected, or the system control computer 52 or the image data controller 78 can be used.
- 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.
- the electron gun 1, the acceleration tube 40, each lens, the sample 3, the image detector 79, etc. can be controlled.
- (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.
- the wavelength of the irradiation beam (wave) is ⁇
- the size of the object to be observed is d
- 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.
- the state in which this L is infinity is the Fourier transform
- 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).
- 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.
- FIG. 6A shows a method of forming a diffraction pattern with an optical system located downstream of the irradiation beam from the sample.
- 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.
- 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.
- a charged particle in this case, an electron
- 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.
- 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.
- 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.
- 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.
- the three-dimensional space both real space and Fourier space, is filled with data.
- the number of iterative calculations can be reduced, and the accuracy of the reconstructed amplitude distribution and phase distribution can be improved.
- 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.
- 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.
- the three-dimensional space both real space and Fourier space, is filled with data.
- the number of iterative calculations can be reduced, and the accuracy of the reconstructed amplitude distribution and phase distribution can be improved.
- 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.
- 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.
- 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.
- ASIC Application Specific Integrated Circuit
- FPGA Field Programmable Gate Array
- 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
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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
本発明は観察試料の3次元回折パターンを構築し、その3次元回折パターンを用いた試料の3次元像と試料とその周辺部を含む空間の電磁場等の情報を3次元構築する3次元像観察技術に関する。
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.
電子線やイオンビームなどの荷電粒子線は、真空中を伝搬させなければならないこと、光学系の各種光学素子には電磁場を必要とし、その偏向角度が小さいこと、光学におけるハーフミラーの様な有効なビームスプリッターがないことなどから、試料など観察対象のために大きな空間を用意することと有効な結像光学系を構成することは難しい。さらには、中性子線や分子線・重粒子線などの電荷を伴わない粒子線ではそもそも光学素子がない。そのため、光源から検出器までの間に試料を配し、経路伝搬による試料での散乱・吸収像の投影観察か、あるいは干渉・回折効果に基づく回折パターンの観察が実施されている。すなわち、上記粒子線装置においては、1経路の光学系が用いられるのみであり、試料の3次元構造(立体構造)観察のためには、試料を回転させて複数方位からの観察を実施するしかないのが実情である。
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.
そのため、試料など観察対象の3次元構造の計測には、トモグラフィー、ラミノグラフィーなど、試料と照射ビーム(光、X線、電子線など)との角度関係を徐々に変化させながら多数枚の画像を記録し、それぞれの画像間の角度関係を元に3次元構造を構築する手法が用いられている。これらの3次元構造の計測法では、計測画像の枚数を増やせれば増やせるだけ試料に関する情報量が増え、精度の高い3次元構築像が得られる。そのため、試料の回転に伴う位置の変化や光学系でのフォーカスの変化などについて、補償するための仕組みがさまざまに工夫されている。
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.
上記粒子線装置類の中では、電子線を用いた電子顕微鏡が最も開発が進んでおり、電子レンズ、偏向器、電子線バイプリズムなど様々な光学素子が実現され、結像光学系も実用化されている。そのため、本願では荷電粒子線の代表として電子線についての構成を記載するが、本発明の原理は粒子線においてだけでなく、さらには電磁波などの波動場において共通であり、本願は電子線に限定するものではない。関連する先行技術文献には特許文献1、2、非特許文献1~4がある。
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.
観察対象の3次元像観察(立体像観察)には、トモグラフィー、ラミノグラフィーなど、試料と照射ビーム(光、X線、電子線など)との角度関係を徐々に変化させながら多数枚の画像を記録し、それぞれの画像間の角度関係を元に3次元構造を構築する手法がある。この手法では、多数枚の画像を使えれば使えるだけ、試料に関する情報量が増え、精度の高い3次元構築像が得られる。しかし、多数枚の画像データを取得するには、それだけの時間が必要となるうえ、例えば生体試料や有機材料、およびLi電池材料などでは高いエネルギーの照射線であるX線や電子線の被曝により、試料自体が変化してしまう問題があった。また、画像データ取得時間だけでなく、取得後に多数枚の画像を演算処理するための時間も処理枚数に依存することは言を俟たない。さらに、トモグラフィー、ラミノグラフィーでは、例えば、±70°の回転角度範囲から得られた情報では、情報の得られる±70°の範囲内をいかに細かく区分して情報を得ても、情報が得られなかった領域(missing cone(ミッシングコーン)と言われる)が大きなアーティファクトを生む原因となっている。以上の課題に鑑み、最小ドーズ量から最大データ量(互いに直交する3方向からなる投影像)の取得を実現し、その再生方法について提案している先行出願(特許文献1参照)がある。
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.
先行出願では、ほぼ直交する3方向からなる投影像を得ることは可能であったが、その3枚の画像データから3次元像を再構築する方法については、具体的に述べられてはいなかった。とりわけ、3枚の画像の空間位置の決め方については、マーカーを用いることが述べられているが具体例の開示はなかった。
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.
また、マーカーを利用する方法についても、従来のトモグラフィーのごとく細かな角度変化について、所定のマーカーを順を追って追跡することには困難さはなく実現されているが、互いに直交する3方向からの実像では、観察対象の形状や相対位置関係は大きく変化し、マーカーを用いるだけでは不可能なことが多く、仮に可能であっても精度が低いのが実情であった。
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.
そこで、最小のドーズ量で最大の情報量が得られる直交する3方向からの試料の投影像において、あるいは、回折パターンにおいて、高精度かつ簡便に互いの位置関係を決定し該試料等観察対象の3次元構造を決定すること、さらに、該試料など観察対象の3次元位相分布および3次元振幅分布を構築することに関して、その装置と方法を提供することを本発明の目的とする。
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.
現在の情報処理の言葉で表すならば、トモグラフィーやラミノグラフィーなどの従来法はビッグデータの処理に対するディープラーニングであるのに対して、本発明の方法は、少ないデータから特徴を抽出しそれを有効利用するスパースモデリングに該当する。このような考え方で実践される実験手法・装置である。
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.
上記の目的を達成するため、本発明においては、新たな3次元回折パターン、すなわち、3つの座標軸(X、Y、Z)が張る空間をXYZ空間とし、前記XYZ空間に保持された観察対象に対して、前記X軸方向への前記試料の回折パターンをYZ面回折パターンとし、かつ、前記YZ面回折パターンの最大強度の点を前記YZ面回折パターンの原点とし、前記Y軸方向への前記試料の回折パターンをZX面回折パターンとし、かつ、前記ZX面回折パターンの最大強度の点を前記ZX面回折パターンの原点とし、前記Z軸方向への前記試料の回折パターンをXY面回折パターンとし、かつ、前記XY面回折パターンの最大強度の点を前記XY面回折パターンの原点とし、前記観察対象が在する空間とは別なる3つの座標軸(X’、Y’、Z’)が張る空間をX’Y’Z’空間とするとき、前記YZ面回折パターンが前記X’Y’Z’空間のY’Z’面の座標原点と前記YZ面回折パターンの原点とが一致するよう前記Y’Z’面に配置させられ、前記ZX面回折パターンが前記X’Y’Z’空間のZ’X’面の座標原点と前記ZX面回折パターンの原点とが一致するよう前記Z’X’面に配置させられ、前記XY面回折パターンが前記X’Y’Z’空間のX’Y’面の座標原点と前記XY面回折パターンの原点とが一致するよう前記X’Y’面に配置させられている3枚の回折パターンからなる3次元回折パターンに対して、3次元フーリエ変換に基づくフーリエ変換位相回復反復演算法により、前記観察対象を透過、もしくは反射、あるいは散乱を受けた波動の振幅分布と位相分布を構築することを特徴とする3次元像観察装置及び方法を提供する。
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.
本発明によれば、3次元フーリエ変換位相回復反復演算時に振幅項だけでなく位相項も同時に構築が可能である。そのため、観察対象の3次元像(振幅像の二乗としての強度分布)だけでなく位相分布も同時に得られる。この位相分布は従来の透過電子顕微鏡では観察できなかった情報であり、電子線ホログラフィーなど特殊技術を必要としていた。3次元の位相分布とは、各々の方位に対して、および、合成された任意の方位に対して、それぞれの投影位相が担う物理情報が得られることを意味している。例えば照射ビームが電子線の場合、空間電磁場の投影分布から3次元分布を得ることができる。
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.
以下、本発明を実施するための形態を説明するに先立ち、本発明がよって立つところの、技術・手法と原理を概説する。
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.
<トリゴノグラフィー(Trigonography(三角投影顕微鏡法))>
直交する3方向からの投影像を得る方法、及びその3枚の画像から観察対象の3次元像(立体像)を得る手法のことである。製図学における第3角法(トリゴノメトリー(Trigonometry))と同じ原理によるもので、直交する3方向からの投影図をもとに、対象の3次元構造の再現を目的とする。直交する3方向からの観測は、3次元空間では最も情報量の多いデータ群となる。いわばスパースモデリングの考え方を実践して得られた少数でかつ有効なデータ群である。 <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.
直交する3方向からの投影像を得る方法、及びその3枚の画像から観察対象の3次元像(立体像)を得る手法のことである。製図学における第3角法(トリゴノメトリー(Trigonometry))と同じ原理によるもので、直交する3方向からの投影図をもとに、対象の3次元構造の再現を目的とする。直交する3方向からの観測は、3次元空間では最も情報量の多いデータ群となる。いわばスパースモデリングの考え方を実践して得られた少数でかつ有効なデータ群である。 <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.
図1にこの直交する3方向からの観測の重要さを例示している。人間の肉眼のような2方向からのステレオ観測では、図1の観察対象の構造(鑿(のみ)の刃形)を知ることはできない。機械加工の現場では、第3角法に元づく設計図面(正面図、上面図、側面図)が与えられれば、工作者は3次元構造を加工できる。この考え方を、顕微鏡法に取り込む試みである。本手法の構成については先行出願がある(特許文献1参照)が、電子顕微鏡に代表される荷電粒子線の装置においては、互いに直交する3方向の画像を得る手法が技術的に開発途上にあることと、得られた3枚の画像において共通する基準点を確保することが困難なため、まだ実用化には至っていない。本発明は、上記基準点を後述する中央断面定理を用いることによって回避する手法を提供するものである。
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(回折顕微鏡法)>
回折パターンから実像を得る手法のことである。図2に本手法の原理を示す。記録された回折パターン(強度分布のみ)に任意の位相分布を付加して初期画像データF’(X’,Y’)とした後、フーリエ逆変換を行い、仮の実像として像f(X,Y)を得る(実空間での振幅分布と位相分布)。これに拘束条件を付加した後(f’(X,Y))、さらにフーリエ変換を実施し、仮の回折パターンF(X’,Y’)を得る(フーリエ空間(逆空間)での振幅分布と位相分布)。この仮の回折パターンF(X’,Y’)にフーリエ空間での拘束条件を課し、次の画像データF’(X’,Y’)として再度演算を実施する。このように、交互に上述の反復演算を行い、その収束像として実像(振幅分布、位相分布)を得る手法が、フーリエ変換位相回復反復演算法である。カメラシステムの高精度化と計算機の高速化により実現された。X線など結像光学系を持たない画像計測の分野で主に用いられている。電子顕微鏡では実像が直接観察可能であるため、あまり使用されていない手法である。 <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.
回折パターンから実像を得る手法のことである。図2に本手法の原理を示す。記録された回折パターン(強度分布のみ)に任意の位相分布を付加して初期画像データF’(X’,Y’)とした後、フーリエ逆変換を行い、仮の実像として像f(X,Y)を得る(実空間での振幅分布と位相分布)。これに拘束条件を付加した後(f’(X,Y))、さらにフーリエ変換を実施し、仮の回折パターンF(X’,Y’)を得る(フーリエ空間(逆空間)での振幅分布と位相分布)。この仮の回折パターンF(X’,Y’)にフーリエ空間での拘束条件を課し、次の画像データF’(X’,Y’)として再度演算を実施する。このように、交互に上述の反復演算を行い、その収束像として実像(振幅分布、位相分布)を得る手法が、フーリエ変換位相回復反復演算法である。カメラシステムの高精度化と計算機の高速化により実現された。X線など結像光学系を持たない画像計測の分野で主に用いられている。電子顕微鏡では実像が直接観察可能であるため、あまり使用されていない手法である。 <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.
<中央断面定理>
3次元物体の投影像のフーリエ変換は、元の物体の3次元フーリエ変換されたフーリエ空間において、原点を通る一断面と同じである、という定理のことである。簡単に言うと、直交3方向の投影像のフーリエ変換パターンの原点は、常に一致するということである。この中央断面定理を実験データである回折パターンに適用し、回折パターンが記録された光軸上のスポット、すなわち回折パターンの中での最大強度の点を原点として、フーリエ変換位相回復反復演算法により3次元像観察を実現するのが本願発明である。 <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.
3次元物体の投影像のフーリエ変換は、元の物体の3次元フーリエ変換されたフーリエ空間において、原点を通る一断面と同じである、という定理のことである。簡単に言うと、直交3方向の投影像のフーリエ変換パターンの原点は、常に一致するということである。この中央断面定理を実験データである回折パターンに適用し、回折パターンが記録された光軸上のスポット、すなわち回折パターンの中での最大強度の点を原点として、フーリエ変換位相回復反復演算法により3次元像観察を実現するのが本願発明である。 <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.
以下の本明細書の記載、及び特許請求の範囲の記載において、荷電粒子線装置とは、電子線やイオンビームなどの荷電粒子線を用いる装置を総称するものとする。ただし、回折パターンは広く光学分野ではデータとして形成される、あるいは素子として利用されているものであり、上記荷電粒子線に限るものではない。本願のアイデアは、波動を伴いブラッグ回折する程度の可干渉性を持つビームであれば実施可能であり、中性子線や分子線・重粒子線などの粒子線、および、X線や紫外線、ガンマ線などの電磁波においても実現可能なものである。そして、回折パターンの形成には、粒子線を含む波動の伝搬が利用可能であるため、これらの装置においては結像光学系を構成する必要はなく、本願のアイデアは、粒子線および波動を取り扱える装置であれば、広く実施可能である。さらに、互いに直交する3方向からの投影像、あるいは回折パターンとは、『ほぼ直交する』という意であり、現実の装置系においては可動精度の制約などがあり、現実的な『直交』の範囲は、90°±5°程度であり、この程度の揺らぎは本発明の装置、手法の許容範囲であることを明記しておく。
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.
実施例1にて、本願発明における3次元回折パターンを説明する。図3は空間に配置された試料を、互いに直交する3方向から投影し、その回折パターンを描いた模式図である。回折パターンとして投影図を描いているが、投影に限るわけではなく、後述するように反射型(図6Bの(C)参照)でもよい。また、投影図から回折パターンを得る方法としては、粒子線あるいは用いる波動場の伝搬のみによる方法(図6Aの(A):フラウンホーファー回折)でもよいし、電子顕微鏡などのように光学系を用いる方法(図6Aの(B))でもよい。図3のような空間関係にて得られた3枚の回折パターン71をそれぞれの投影方向に応じて、3次元空間(主に演算機であるコンピュータ上の空間)に貼り付けたもの(図4の(C))が3次元回折パターン72である。
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 .
図4に直交3方向からの観察像と3次元回折パターンとの関係を示す。ある観察対象を試料とし(図4の(A))、直交する3方向からの観察像を図4の(B)上段に示している。それぞれの観察像は、透過像でもよいし反射像でもよい。図4の(B)上段のそれぞれの観察像の回折パターン71が図4の(B)下段である。これらの回折パターンは像と同様に透過型でも反射型でもよい。これら3枚の回折パターンをそれぞれ観察方向に応じて組み合わせたものが図4の(C)であり、これが3次元回折パターン72である。
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.
本明細書では3次元空間での情報取得効率に鑑み、それぞれ直交する3方向について述べているが、この3方向が直交関係からずれた場合には、情報が減衰し精度の劣化が生じる(ちょうどトモグラフィーやラミノグラフィーでのミッシングコーンに該当する)が、基本的取り扱いは変わらない。すなわち、観察方向(入射ビームの入射方向)に応じて、入射ビーム方向のほぼ垂直な平面に回折パターンを配置すればよい。その程度は、90°±5°と見積もっている。
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°.
3次元回折パターンの配置に際して、上記配置の相対角度だけでなく位置関係も合わせねばならない。すなわち、入射線の位置と得られる回折パターンとの位置関係が既知の場合には、その情報に従って3枚の回折パターンを配置する。すなわち、各々の回折パターンを得た際の光軸の交点を一致させる。入射線の位置と得られる回折パターンとの位置関係が不明、あるいは不明確の場合には、一般的に回折パターンは入射線の方位に最大強度が得られることを利用して、それぞれの回折パターンのその最大強度の点(微小領域)を見出し、それを原点とするように3枚の回折パターンを配置する。
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.
以上のように、3枚の回折パターンの方向と位置とを合わせた回折パターンが3次元回折パターン72である(図4の(C))。現在の画像処理技術では、演算機であるコンピュータ上の仮想空間にデータとして配置されることが主であろうと想定される。
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.
図5に、本実施例に係る粒子線装置のシステム全体の構成例の模式図を示す。図5の装置は荷電粒子線装置であり、100kVから300kV程度の加速電圧を持つ汎用型の電子顕微鏡を想定している。そのため試料の上側、すなわち粒子線の流れる方向の上流側には照射光学系を、試料の下側、すなわち粒子線の流れる方向の下流側には結像光学系を備えたシステム全体を模式的に描いている。さらに、トリゴノグラフィーを実施するための試料保持装置を念頭に、試料3の傾斜+方位角回転を模式的に描いている。
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.
粒子線装置として透過型の電子顕微鏡構成を本実施例に挙げたのは、粒子線装置の中では透過型電子顕微鏡が最もシステムとして開発が進んでいるだけでなく、装置の利用手法においても汎用性を併せ持っているためである。例えば、図5の荷電粒子線装置4のシステムで照射光学系(41、42)のレンズをすべてオフすれば、粒子源1からの電子線27を直接試料に照射する形態となり、合わせて対物レンズ系5および結像光学系(61、62、63、64)もオフすれば、最もシンプルな電子回折装置となる。すなわち、中性子線装置や重粒子線装置、X線装置を模擬する形態として装置を構成することができる。ただし、本願は、本実施例の適用を図5の構成を持つ透過型電子顕微鏡に限定するものではない。
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.
図5において、粒子源である電子銃1が電子線の流れる方向の最上流部に位置し、粒子線の制御ユニット19と加速管の制御ユニット49の制御により、放出された電子線は加速管40にて所定の速度に加速された後、制御ユニット47、48に制御される照射光学系のコンデンサレンズ41、42を経て、所定の強度、照射領域に調整されて試料3に照射される。そして試料は任意の角度に傾斜させられるとともに、光軸2を軸として方位角回転する。この時、傾斜角度を35.3°、方位回転角を120°とした手法がトリゴノグラフィーである(特許文献1参照)。試料3を透過した電子線は、制御ユニット59に制御される対物レンズ5にて結像される。この結像作用は、対物レンズ5よりも後段の制御ユニット69、68、67、66に制御される結像レンズ系61、62、63、64に引き継がれ、最終的に電子線装置の観察記録面75に試料の像が結像される。また、対物レンズ直下に構成された試料の回折パターンも試料の像と同様に結像レンズ系に引き継がれ、最終的に電子線装置の観察記録面75に回折パターン8が結像される。その回折パターンはCCDカメラなど画像検出器79と画像データコントローラ78を経て、例えば画像データモニタ76の画面上で観察したり、画像データ記録装置77に画像データとして格納される。画像データ記録装置77に記録された画像データは、3次元像観察のための例えば反復フーリエ変換位相回復法などの処理に利用される。この画像データ処理のため、専用のコンピュータを接続したり、あるいはシステム制御コンピュータ52や画像データコントローラ78を利用することができる。
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.
これら装置は、全体としてシステム化されており、オペレータはモニタ53の画面上で装置の制御状態を確認するとともに、インターフェース54を介して、各種プログラムが実行され、制御部として機能するシステム制御コンピュータ52を用いて、試料3の制御ユニット39、第2照射レンズ42の制御ユニット47、第1照射レンズ41の制御ユニット48、加速管40の制御ユニット49、対物レンズ5の制御ユニット59、第4結像レンズ64の制御ユニット66、第3結像レンズ63の制御ユニット67、第2結像レンズ62の制御ユニット68、第1結像レンズ61の制御ユニット69、画像検出器79の制御ユニット78等の制御ユニットを制御することにより、電子銃1、加速管40、各レンズ、試料3、画像検出器79などを制御できる。
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.
なお、上記の粒子線装置システムは、透過型電子顕微鏡に基づいて説明したが、イオン顕微鏡などの荷電粒子線装置、および分子線装置、重粒子線装置、中性子線装置、そして広くはX線など電磁波装置に用いてもよい。その際に、それぞれの装置の特性に基づいて光学系の構成が変更されるのは言うまでもない。なお、想定される粒子線装置の多くのものは、粒子線の偏向系や粒子線の軌道部を真空に排気するための真空排気系などを備えているが、本発明と直接の関係が無いため、図示、および説明は省略した。
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.
実施例2として、3次元回折パターンの作成について説明する。図6Aの(A)は、照射するビームの伝搬により観察対象の回折パターンを観察する方法である。これはフラウンホーファー回折として知られた方法で、一般的には、照射ビーム(波動)の波長をλ、観察対象のサイズをd、試料から観察記録面までの伝搬距離をLとおくとき、式1を満たす条件を満足するように構成される。
L >> d2/2λ ・・・(式1)
X線回折、中性子回折、重粒子線回折などは、有効な光学素子を用いた光学系を構成することが困難なため、この伝搬による回折法が主流である。 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.
L >> d2/2λ ・・・(式1)
X線回折、中性子回折、重粒子線回折などは、有効な光学素子を用いた光学系を構成することが困難なため、この伝搬による回折法が主流である。 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.
このLを無限大にした状態が数学的にはフーリエ変換で、試料の像を記録した後に演算機であるコンピュータによるフーリエ変換を情報処理として実施することにより、本願と類似の方法を実現することが可能である(実施例5に後述)。しかしながら、試料の像はすでに粒子線あるいは波動場の位相情報を失っているため、厳密には一致する方法ではない。実験的に試料像のフーリエ変換を実施する手法が次に述べる結像光学系を用いた手法(図6Aの(B))である。
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.
図6Aの(B)は、試料よりも照射ビームの下流側に位置する光学系にて回折パターンを形成する方法を示したものである。厳密には、観察対象をレンズの前側焦点位置、観察をレンズの後側焦点位置にて実施するが、一般的にはレンズの後側焦点位置近傍に形成される照射光源の像の位置で代用している。それで十分な精度が得られている。
(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.
図6Bの(C)は、反射型で回折パターンを得る電子線装置の一例である(非特許文献4より)。反射型での回折パターン観察は背面散乱ラウエ法や表面解析でのLEED(Low Energy Electron Diffraction)観察法など早くから実用化されているが、照射ビームの導入路や照射ビーム源装置などが観察される回折パターンに影を作るなど、対称性の良い回折パターンを得ることが難しかった。図6Bの(C)はこの問題を解決した一例で、半球状の電極を用いることによって荷電粒子(この場合は電子)を楕円軌道を描いて散乱点(入射点)とは異なる点に結像するものである。これにより、照射ビームの導入路や照射ビーム源装置に影響されることのない、回折パターンを得ることができる。図6Bの(D)に実験結果の一例(Si111表面の7×7超格子パターン)を示す(非特許文献4より)。
(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).
これらの回折パターンは、試料だけでなく試料の周りの空間電磁場など、入射粒子線あるいは波動場を散乱・偏向させる対象であれば記録することが可能である。例えば、特許文献2の図14Aに例示されている小角電子回折パターンは試料の磁気構造を反映した回折パターンを得ている。これらの回折パターンからは、磁気情報を再構築することが可能で、本願では、試料片周りに付随した空間の電磁場の3次元観察も念頭に置いている。
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.
次に実施例3として、3次元でのフーリエ変換位相回復反復演算法についてその手順を説明する。実施例1で説明した3次元回折パターンに対して、図2で説明した2次元のフーリエ変換位相回復反復演算法を3次元に拡張して実施することを基本としている。
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.
図7をもとに、手法を簡単に説明する。
The method will be briefly explained based on Figure 7.
(1)記録されたほぼ直交する3方向の3枚の回折パターンから、3次元回折パターン72(図4の(C)および図7の(A))を構成する。
(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)上記、3次元回折パターン(の平方根)を振幅とし、任意の位相項を加えた3次元関数を形成する。これを3次元フーリエ空間(回折空間)関数とする。
(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)この3次元フーリエ空間関数を3次元フーリエ逆変換し、3次元実空間の関数を得る。
(3) 3D inverse Fourier transform of this 3D Fourier space function to obtain a 3D real space function.
(4)得られた3次元実空間の関数に実空間での拘束条件を課す。拘束条件は、試料像外ゼロ(絞り開口外ゼロ)、あるいは別途取得した試料像を用いる。(図7の(B)の枠外側をゼロにする(試料像外ゼロ)、あるいは、図4の(B)上段に示した各方向の試料像を用いる。)
(5)上記実空間拘束条件を課した3次元実空間関数を3次元フーリエ変換し、3次元フーリエ空間関数とする。 (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.
(5)上記実空間拘束条件を課した3次元実空間関数を3次元フーリエ変換し、3次元フーリエ空間関数とする。 (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)3次元フーリエ空間関数にフーリエ空間の拘束条件を課す。
拘束条件には、各々の回折パターン(の平方根)を用いる。(位相項は変更せず、そのまま利用する。)
(7)上記フーリエ空間拘束条件を課した3次元フーリエ空間関数を3次元フーリエ逆変換する。 (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.
拘束条件には、各々の回折パターン(の平方根)を用いる。(位相項は変更せず、そのまま利用する。)
(7)上記フーリエ空間拘束条件を課した3次元フーリエ空間関数を3次元フーリエ逆変換する。 (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)(4)~(7)を収束するまで繰り返す。(3次元フーリエ変換位相回復反復演算法)
以上により得られた収束像の実空間像が求める観察対象試料の実像であり、振幅分布、位相分布ともに3次元分布が再構築されている。回折空間についても同様に、回折空間の振幅分布と位相分布が再構築されている。 (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.
以上により得られた収束像の実空間像が求める観察対象試料の実像であり、振幅分布、位相分布ともに3次元分布が再構築されている。回折空間についても同様に、回折空間の振幅分布と位相分布が再構築されている。 (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.
なお、上記手順(4)~(7)を実施する間に、実空間、フーリエ空間ともに3次元空間がデータで満たされていくが、このときデータの特徴を見出し、スパースモデリングに基づくアルゴリズム等を利用することによって、反復演算の回数を減じたり、再構築される振幅分布、位相分布の精度を向上させることができる。
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.
次いで、図8にもとづき実空間での拘束条件として、『照射領域外ゼロ強度』の条件を用いた実験手順について、および、図9にもとづき実空間での『照射領域外ゼロ強度』の条件に加えて『実空間像』を用いる条件について、回折パターンを得るところから、それら手法の手順を説明する。
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)ほぼ直交する3方向の回折パターン(逆空間像)3枚をそれぞれ記録する(図4の(B)参照)。回折パターンの作り方は、空間伝播による方法(図6Aの(A))、光学系を用いる方法(図6Aの(B)、図6Bの(C))などがある。
(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)上記、記録されたほぼ直交する3方向の3枚の回折パターンを3次元逆空間(フーリエ空間)上で各パターンの面を合わせ、方向を合わせ、かつ、原点を合わせる(図4の(C))。
(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)上記、3枚の回折パターン(の平方根)を振幅とし、任意の位相項を加えた3次元関数を形成する。これを3次元フーリエ空間(回折空間)関数とする。
(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)この3次元フーリエ空間関数を3次元フーリエ逆変換し、3次元実空間の関数を得る。
(4) 3D inverse Fourier transform of this 3D Fourier space function to obtain a 3D real space function.
(5)得られた3次元実空間の関数に実空間での拘束条件を課す。
拘束条件は、試料像外ゼロ(絞り開口外ゼロ)、あるいは別途取得した試料像(図4の(B)上段に示した各方向の試料像)を用いる。 (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.
拘束条件は、試料像外ゼロ(絞り開口外ゼロ)、あるいは別途取得した試料像(図4の(B)上段に示した各方向の試料像)を用いる。 (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)上記拘束条件を課した3次元実空間関数を3次元フーリエ変換し、3次元フーリエ空間関数とする。
(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)3次元フーリエ空間関数にフーリエ空間の拘束条件を課す。
拘束条件には、各々の回折パターン(の平方根)を用いる。(位相項は変更せず、そのまま利用する。)
(8)上記フーリエ空間拘束条件を課した3次元フーリエ空間関数を3次元フーリエ逆変換する。 (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.
拘束条件には、各々の回折パターン(の平方根)を用いる。(位相項は変更せず、そのまま利用する。)
(8)上記フーリエ空間拘束条件を課した3次元フーリエ空間関数を3次元フーリエ逆変換する。 (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)(5)~(8)を収束するまで繰り返す。(3次元フーリエ変換位相回復反復演算法)
以上により得られた収束像の実空間像が求める観察対象試料の実像であり、振幅分布、位相分布ともに3次元分布が再構築されている。回折空間についても同様に、回折空間の振幅分布と位相分布が再構築されている。 (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.
以上により得られた収束像の実空間像が求める観察対象試料の実像であり、振幅分布、位相分布ともに3次元分布が再構築されている。回折空間についても同様に、回折空間の振幅分布と位相分布が再構築されている。 (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.
なお、上記手順(4)~(7)を実施する間に、実空間、フーリエ空間ともに3次元空間がデータで満たされていくが、このときデータの特徴を見出し、スパースモデリングに基づくアルゴリズム等を利用することによって、反復演算の回数を減じたり、再構築される振幅分布、位相分布の精度を向上させることができる。
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.
実施例5として、実施例1で説明した3方向の3枚の実像のフーリエ変換パターンを用いた3次元空間のそれぞれの像の位置を合わせる方法について説明する。これは中央断面定理に基づく方法である。
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)ほぼ直交する3方向の画像(実空間像)3枚をそれぞれ記録する。
(1) Record three images (real space images) in three nearly orthogonal directions.
(2)上記、記録された直交3方向の画像3枚をそれぞれ2次元フーリエ変換する。
(2) Perform a two-dimensional Fourier transform on each of the three recorded images in the three orthogonal directions.
(3)3次元逆空間(フーリエ空間)上で3枚のパターンの面を合わせ、方向を合わせ、かつ、原点を合わせる(図4の(C))。
(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)各々のフーリエ変換パターンをそれぞれの平面内で2次元フーリエ逆変換し、それぞれその平面内の実像に戻す。
得られたそれぞれの実像は、それぞれの位置関係が中央断面定理により、適切な相関を持つものになっている。 (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.
得られたそれぞれの実像は、それぞれの位置関係が中央断面定理により、適切な相関を持つものになっている。 (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)3次元実像を構築する。
3次元実空間上の空間密度(像強度)は、投影像の積算、あるいは和算など実空間内の演算処理によって求める。 (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.
3次元実空間上の空間密度(像強度)は、投影像の積算、あるいは和算など実空間内の演算処理によって求める。 (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.
本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明のより良い理解のために詳細に説明したのであり、必ずしも説明の全ての構成を備えるものに限定されるものではない。
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.
更に、上述した各構成、機能、システム制御コンピュータ等は、それらの一部又は全部を実現するプログラムを利用する場合を説明したが、それらの一部又は全部を例えば集積回路で設計する等によりハードウェアで実現しても良いことは言うまでもない。すなわち、処理部の全部または一部の機能は、プログラムに代え、例えば、ASIC(Application Specific Integrated Circuit)、FPGA(Field Programmable Gate Array)などの集積回路などにより実現してもよい。
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 電子銃もしくは粒子源
8 回折パターン
18 真空容器
19 粒子源の制御ユニット
2 光軸
27 電子線もしくは粒子線
3 試料もしくは試料保持装置
39 試料保持装置の制御ユニット
4 荷電粒子線装置
40 加速管
41 第1コンデンサレンズ
42 第2コンデンサレンズ
47 第2コンデンサレンズの制御ユニット
48 第1コンデンサレンズの制御ユニット
49 加速管の制御ユニット
5 対物レンズ
52 システム制御コンピュータ
53 システム制御コンピュータのモニタ
54 システム制御コンピュータのインターフェース
59 対物レンズの制御ユニット
61 第1結像レンズ
62 第2結像レンズ
63 第3結像レンズ
64 第4結像レンズ
66 第4結像レンズの制御ユニット
67 第3結像レンズの制御ユニット
68 第2結像レンズの制御ユニット
69 第1結像レンズの制御ユニット
71 回折パターン
72 3次元回折パターン
75 像もしくはパターン検出面
76 画像データモニタ
77 画像データ記録装置
78 画像データコントローラ
79 画像検出器
8 試料像もしくは回折パターン 1 Electron gun orparticle 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
8 回折パターン
18 真空容器
19 粒子源の制御ユニット
2 光軸
27 電子線もしくは粒子線
3 試料もしくは試料保持装置
39 試料保持装置の制御ユニット
4 荷電粒子線装置
40 加速管
41 第1コンデンサレンズ
42 第2コンデンサレンズ
47 第2コンデンサレンズの制御ユニット
48 第1コンデンサレンズの制御ユニット
49 加速管の制御ユニット
5 対物レンズ
52 システム制御コンピュータ
53 システム制御コンピュータのモニタ
54 システム制御コンピュータのインターフェース
59 対物レンズの制御ユニット
61 第1結像レンズ
62 第2結像レンズ
63 第3結像レンズ
64 第4結像レンズ
66 第4結像レンズの制御ユニット
67 第3結像レンズの制御ユニット
68 第2結像レンズの制御ユニット
69 第1結像レンズの制御ユニット
71 回折パターン
72 3次元回折パターン
75 像もしくはパターン検出面
76 画像データモニタ
77 画像データ記録装置
78 画像データコントローラ
79 画像検出器
8 試料像もしくは回折パターン 1 Electron gun or
Claims (13)
- 3つの座標軸(X、Y、Z)が張る空間をXYZ空間とし、
前記XYZ空間に保持された観察対象である試料に対して、
前記X軸方向への前記試料の回折パターンをYZ面回折パターンとし、
前記Y軸方向への前記試料の回折パターンをZX面回折パターンとし、
前記Z軸方向への前記試料の回折パターンをXY面回折パターンとし、
前記観察対象が存する空間とは別なる3つの座標軸(X’、Y’、Z’)が張る空間をX’Y’Z’空間とするとき、
前記YZ面回折パターンが前記X’Y’Z’空間のY’Z’面に配置し、
前記ZX面回折パターンが前記X’Y’Z’空間のZ’X’面に配置し、
前記XY面回折パターンが前記X’Y’Z’空間のX’Y’面に配置している3次元回折パターンに対し、3次元フーリエ変換に基づく反復フーリエ変換位相回復法により、前記観察対象を透過、もしくは反射、あるいは散乱を受けた波動の振幅分布と位相分布を構築する、ことを特徴とする3次元像観察装置。 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. - 請求項1に記載の3次元像観察装置であって、
前記3次元回折パターンが、
前記YZ面回折パターンの最大強度の点を前記YZ面回折パターンの原点とし、
前記ZX面回折パターンの最大強度の点を前記ZX面回折パターンの原点とし、
前記XY面回折パターンの最大強度の点を前記XY面回折パターンの原点とし、
前記X’Y’Z’空間のY’Z’面の座標原点と前記Y’Z’面に配置した前記YZ面回折パターンの原点とが一致し、
前記X’Y’Z’空間のZ’X’面の座標原点と前記Z’X’面に配置した前記ZX面回折パターンの原点とが一致し、
前記X’Y’Z’空間のX’Y’面の座標原点と前記X’Y’面に配置した前記XY面回折パターンの原点とが一致しているものである、
ことを特徴とする3次元像観察装置。 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: - 請求項1もしくは請求項2に記載の3次元像観察装置であって、
前記観察対象が金属、半導体、誘電体、無機物、有機物、生体からなる物質、もしくは前記金属、前記半導体、前記誘電体、前記無機物、前記有機物、前記生体が内在する電磁場、あるいは外部に発生させる磁場である、
ことを特徴とする3次元像観察装置。 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: - 請求項3に記載の3次元像観察装置であって、
前記YZ面回折パターンと前記ZX面回折パターンと前記XY面回折パターンとが、前記観察対象を透過もしくは散乱を受けた荷電粒子線によって作られるものである、
ことを特徴とする3次元像観察装置。 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: - 請求項3に記載の3次元像観察装置であって、
前記YZ面回折パターンと前記ZX面回折パターンと前記XY面回折パターンとが、前記観察対象を反射もしくは散乱を受けた荷電粒子線によって作られるものである、
ことを特徴とする3次元像観察装置。 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: - 請求項3に記載の3次元像観察装置であって、
荷電粒子線が前記観察対象を照射した後に、
前記YZ面回折パターンがX軸方向に空間を伝搬することにより作られるものであり、
前記ZX面回折パターンがY軸方向に空間を伝搬することにより作られるものであり、
前記ZX面回折パターンがZ軸方向に空間を伝搬することにより作られるものである、
ことを特徴とする3次元像観察装置。 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: - 請求項3に記載の3次元像観察装置であって、
荷電粒子線が前記観察対象を照射した後に、
前記YZ面回折パターンがX軸方向の前記荷電粒子線の光学系により作られるものであり、
前記ZX面回折パターンがY軸方向の前記荷電粒子線の光学系により作られるものであり、
前記ZX面回折パターンがZ軸方向の前記荷電粒子線の光学系により作られるものである、
ことを特徴とする3次元像観察装置。 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: - 請求項1乃至7のいずれか一項に記載の3次元像観察装置であって、
前記反復フーリエ変換位相回復法がスパースモデリングに基づく処理アルゴリズムを利用するものである、
ことを特徴とする3次元像観察装置。 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: - 3つの座標軸(X、Y、Z)が張る空間をXYZ空間とし、
前記XYZ空間に保持された観察対象である試料に対して、
前記X軸方向への前記試料の回折パターンをYZ面回折パターンとし、かつ、前記YZ面回折パターンの最大強度の点を前記YZ面回折パターンの原点とし、
前記Y軸方向への前記試料の回折パターンをZX面回折パターンとし、かつ、前記ZX面回折パターンの最大強度の点を前記ZX面回折パターンの原点とし、
前記Z軸方向への前記試料の回折パターンをXY面回折パターンとし、かつ、前記XY面回折パターンの最大強度の点を前記XY面回折パターンの原点とし、
前記観察対象が存する空間とは別なる3つの座標軸(X’、Y’、Z’)が張る空間をX’Y’Z’空間とするとき、
前記YZ面回折パターンが前記X’Y’Z’空間のY’Z’面の座標原点と前記YZ面回折パターンの原点とが一致するよう前記Y’Z’面に配置させられ、
前記ZX面回折パターンが前記X’Y’Z’空間のZ’X’面の座標原点と前記ZX面回折パターンの原点とが一致するよう前記Z’X’面に配置させられ、
前記XY面回折パターンが前記X’Y’Z’空間のX’Y’面の座標原点と前記XY面回折パターンの原点とが一致するよう前記X’Y’面に配置させられている3次元回折パターンに対し
て、
3次元フーリエ変換に基づく反復フーリエ変換位相回復法により、前記観察対象を透過、もしくは反射、あるいは散乱を受けた波動の振幅分布と位相分布を構築する、ことを特徴とする3次元像観察方法。 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. - 請求項9に記載の3次元像観察方法であって、
前記反復フーリエ変換位相回復法において、
実空間での3次元関数に課する拘束条件が、
前記観察対象に対して前記X軸方向へ投影された試料の実像上における前記波動の照射領域と、
前記観察対象に対して前記Y軸方向へ投影された試料の実像上における前記波動の照射領域と、
前記観察対象に対して前記Z軸方向へ投影された試料の実上における前記波動の照射領域像と、
を用いるものである、
ことを特徴とする3次元像観察方法。 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: - 請求項9に記載の3次元像観察方法であって、
前記反復フーリエ変換位相回復法において、
実空間での3次元関数に課する拘束条件が、
前記試料に対して前記X軸方向の試料の実像と、
前記試料に対して前記Y軸方向の試料の実像と、
前記試料に対して前記Z軸方向の試料の実像と、
を用いるものである、
ことを特徴とする3次元像観察方法。 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: - 請求項9乃至11のいずれか一項に記載の3次元像観察方法であって、
前記反復フーリエ変換位相回復法がスパースモデリングに基づく処理アルゴリズムを利用するものである、
ことを特徴とする3次元像観察方法。 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: - 請求項9乃至12のいずれか一項に記載の3次元像観察方法であって、
前記波動が荷電粒子波である、
ことを特徴とする3次元像観察方法。 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:
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