JP2004301852A - Sample preparation apparatus for three-dimensional structure observation, electron microscope, and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample manufacturing device for an electron microscope for observing the three-dimensional structure of a desired place in a finely processed semiconductor device, and to provide the electron microscope and its method. <P>SOLUTION: A dicer is used for processing a sample piece 10 and converged ion beam processing is used in processing for shaving off the part to be observed of the sample piece 10 into a projected shape. The sample piece 10 is fixed to an uniaxial ominidirectionally inclined sample holder so that the center axis of the projection 11 formed coincides with the inclined axis Z of the sample piece and a TEM image formed by electrons scattered at a high angle is used as a projection image to perform reconstitution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a three-dimensional structure observation sample preparation apparatus for three-dimensionally observing a structure at a desired location in a finely processed semiconductor device, and an observation means and method thereof.

  In semiconductor devices, as the sample structure becomes finer, the importance of observation with a transmission electron microscope (hereinafter abbreviated as TEM) having high spatial resolution is increasing. In addition, there is an increasing demand for three-dimensionally evaluating the structure of a semiconductor device manufactured by overlapping various pattern shapes.

  In response to these requirements, attempts have been made to observe the three-dimensional structure of a sample using a TEM. Hereinafter, the procedure of the conventional observation method will be described.

First, the sample is thinned in order to observe a TEM image of the observation target. The distance that the electron beam can pass through the sample is short, and when the incident voltage of the transmission electron microscope is 100 to 300 kV, the distance that the electron beam can pass is 100 nm or less. In order to reduce the thickness of the observation target to 100 nm or less, the sample is thinned to about 100 μm using an abrasive.
Further, the vicinity of the observation object is polished in a mortar shape to a thickness of several tens of micrometers, and then thinned to 100 nm or less by using, for example, a TEM sample preparation apparatus described in JP-A-5-312700.

  The thinned sample piece is fixed to a ring-shaped sample stage, and the periphery of the sample stage is fixed to a sample holder described in, for example, a method and apparatus for supporting a sample of an electron microscope described in Japanese Patent Application Laid-Open No. 6-139986. It is inserted into a room and a TEM image of the observation target is observed. To evaluate the three-dimensional structure, a TEM image obtained by observing a sample piece from a plurality of directions while tilting the sample piece in a sample chamber is used.

Further, in order to quantitatively evaluate the three-dimensional structure, three-dimensional reconstruction is performed using a TEM image as a projection image. In order to use a TEM image of a crystalline sample as a projection image, high-angle scattering formed by electrons scattered at high angles by atoms in the sample using a three-dimensional atomic arrangement observation apparatus described in Japanese Patent Application No. 3-110126 is disclosed. It is necessary to use an electronic image. This is because the contrast of the TEM image contains not only the scattering contrast that mainly reflects the electron scattering ability but also the diffraction contrast that mainly reflects the crystal structure. If the TEM image is used as a projection image, the diffraction contrast is reduced. It is necessary to make it. Using the high-angle scattering electron image, three-dimensional structure reconstruction is performed by the method described in Japanese Patent Application No. 3-110126.
First, each two-dimensional cross section is reconstructed using the projection cut plane theorem, and they are stacked to construct a three-dimensional structure.

JP-A-3-110126

  In the conventional TEM observation specimen, the observation target exists near the center of the mortar-shaped specimen. In such a shape, if the sample piece is greatly inclined, the thickness of the sample through which the electron beam passes increases, and the TEM image cannot be obtained because the electron beam cannot be transmitted. Further, in the conventional TEM observation sample holder, if the sample holder is greatly inclined, the ring-shaped sample stage or the sample holder blocks the electron beam path, so that a TEM image cannot be obtained. That is, as long as the conventional sample piece shape and sample holder are used, the range of the sample inclination angle is limited, and the observation target cannot be observed from any direction. The tilt angle range of a general-purpose TEM is about ± 60 degrees, and the higher the spatial resolution of the TEM, the narrower the gap of the electron lens is designed. Therefore, the width of the sample chamber into which the sample holder is inserted becomes narrower. It is getting smaller.

  Furthermore, the limitation of the sample tilt angle range is a very serious obstacle in three-dimensional reconstruction. The projection plane cutting theorem used in image reconstruction is that a one-dimensional Fourier transform of projection data p (r, θ) from a θ direction of a sample f (x, y) is a two-dimensional Fourier transform F (μ, μ) of the sample. ν) is the theorem that it matches the line profile of the cut surface in the θ direction (FIG. 17A). That is, if the projection data in all directions is obtained, all the information on the sample structure is obtained (FIG. 17B).

  However, when the projection angle range is limited, necessary information is lost as shown in FIG. 17C, and it is theoretically difficult to obtain an accurate reconstructed image. When reconstruction is performed under the limitation of the projection angle, severe artifacts occur on the reconstructed image, and the artifacts may not be able to analyze the sample structure. Methods for reducing the above-mentioned artifacts by image restoration processing have been studied. However, various assumptions regarding the sample structure are required, and the sample shape to which the restoration processing can be applied is limited. Attempts have also been made to prepare a plurality of samples having the same structure and obtain a projection image in all directions of the sample by thinning the sample from different directions. It could not be applied if there was only one.

  In the present invention, as the three-dimensional observation sample piece, a sample piece processed into a shape having a projection portion including the observation target is used. With the sample piece, the observation target can be observed from all directions around the central axis of the protrusion. A dicer, a focused ion beam processing device, or the like is used to process the sample into the above shape. The focused ion beam processing apparatus has an ion beam deflector and a blanker for producing a projection including an observation target. Further, a one-axis omnidirectional tilt sample holder is used as the sample holder. The one-axis omnidirectional tilt sample holder is constituted by a holding cylinder and a rod-shaped support supported by the holding cylinder, and the rod-shaped support is designed to be tiltable in all directions of one axis. If the sample piece is set at the tip of the rod-shaped support so that the central axis of the projection and the sample tilt axis are aligned, the observation object can be observed at an angle of 360 ° around the central axis of the projection. That is, TEM images of the observation target in all directions can be obtained.

  According to the present invention, a TEM image obtained by observing an observation object from an arbitrary direction around the center axis of the projection can be obtained, so that a three-dimensional sample structure can be directly evaluated. Further, observation of a projected image in all directions, which is a necessary condition for reconstructing the three-dimensional structure of the sample, is realized. Therefore, it is not necessary to use known information about the sample, and an arbitrary sample shape can be accurately reconstructed from one sample piece.

  According to the present invention, a sample structure of an arbitrary shape and an arbitrary position in a three-dimensionally constructed device structure is analyzed three-dimensionally, and important information on device process checking and optimization and device design is provided. be able to.

  FIG. 1 shows a basic configuration of a transmission electron microscope used in an embodiment of the present invention. Electron gun 1, condenser lens 2, electron beam deflection coil 3, objective lens 4, sample holder 5, sample tilting mechanism 6, in-column type 7 and post-column type 35 energy filter, image It comprises a recording device 8 and a computer 9 having control software and image processing software.

  FIG. 2 shows the shape of the sample piece 10 used in this embodiment. The sample piece 10 is processed into a chip having a projection 11 on a certain surface. The central axis of the projection 11 is defined as the z-axis. The protruding portion 11 includes the observation target 12. The diameter 2R of the protrusion in the above-mentioned region is set within a range in which an electron beam can pass. The diameter 2R depends on the acceleration voltage of the incident electron beam, and the higher the acceleration voltage, the longer the distance the electron beam transmits. 2R is 100 nm or less when the acceleration voltage is 100 to 300 kV, and 10 μm or less when the acceleration voltage is 3 MV.

  The sample piece 10 is fixed to a sample stage 13 shown in FIG. A table on which the sample piece 10 is placed is provided above the sample table 13, and a screw 16 for fixing the sample table 13 to the rod-shaped support 15 is provided below the sample table 13. There are a sample stage (FIG. 3A) for fixing the sample piece 10 with an adhesive and a sample stage (FIG. 3B) for fixing with a screw.

In the sample stage 13 of FIG. 3A, the upper portion of the sample stage 13 and the lower surface of the sample piece 10 are fixed with an adhesive. Since the device structure is simple, miniaturization is easy. The sample stage 13 shown in FIG. 3B has a concave portion on which the sample is placed above the sample stage 13, and the sample piece 10 is fixed with four screws 40 attached to the outer frame of the concave portion.
With this structure, fine adjustment of the sample position in the sample stage can be performed with four screws. Further, since the sample piece 10 can be easily attached and detached, it is possible to observe the same sample piece 10 after processing the sample piece 10 once observed by another apparatus. Further, since no adhesive is used, deterioration of the degree of vacuum in the sample chamber can be avoided.

  FIG. 4 shows a configuration diagram of the uniaxial omnidirectional tilt holder. The one-axis omnidirectional sample holder has a rod-shaped support 15 supported by a holding cylinder 14, and the rod-shaped support 15 can be tilted in all directions of one axis. The sample tilt axis direction is the Z axis, the electron beam incident direction is the Y axis, and the direction orthogonal to the two axes is the X axis. The parallel movement of the sample piece 10 is realized by moving the entire sample holder in the XYZ directions by a holder fine movement mechanism using a pulse motor and a lever, similarly to the conventional TEM sample holder. The sample table 13 to which the sample piece 10 is fixed is attached by inserting a screw 16 below the sample table 13 into a screw hole provided at the tip of the rod-shaped holder 15.

  A protective cover 34 as shown in FIG. 7 is attached to the sample stage 13 to prevent the projection 11 from being destroyed when the sample stage is fixed. The protective cover 34 has a cylindrical shape, and has a vertically long hole on a side surface. If the protective cover 34 is raised and fixed with the screws 41 as shown in FIG. 7A, it is possible to considerably prevent the projection 11 from being broken by mistake during the operation. When processing and observing the projection 11 from the side, the protective cover 34 is lowered as shown in FIG.

  Since the center axis of the screw 16 is aligned with the sample tilt axis Z, when the rod-shaped support 15 is tilted, the sample table 13 tilts around the center axis of the screw 16. Further, if the sample piece 10 is fixed to the sample table 13 with the central axis of the projection 11 and the central axis of the screw 16 aligned, the projection 11, that is, the observation target 12, can be observed obliquely in all directions along one axis.

  As a device for matching the center axis z of the projection 11 with the sample tilt axis Z, for example, there are the following two devices.

One is to use an optical microscope having a mark 17 attached to the sample table 13 as shown in FIG. 5A and a cross pattern 18 inserted on the optical axis. Two sets of the marks 17 are attached to the upper part of the sample table 13 so as to face each other. The straight lines connecting the marks intersect with each other on the Z axis when the sample table 13 is fixed to the rod-shaped support 15.
If the sample stage 13 is set such that the straight line connecting the marks 17 of the sample stage 13 and the cross pattern 18 coincide with each other, and the sample is fixed to the sample stage 13 so that the tip of the projection 11 coincides with the center of the cross pattern 18, The center axis z of the projection 11 and the sample tilt axis Z of the sample holder match.

  The other uses a sample stage rotating device (FIG. 5B) having a screw hole into which the sample stage 13 can be inserted, and an optical microscope. The rotating table 19 can rotate the sample table 13 around the center axis of the screw 16. The sample stage 13 on which the sample 10 is placed is rotated, and the movement of the projection 11 is observed with an optical microscope. When the center axis z of the projection 11 coincides with the sample stage and the rotation axis, the center position of the projection 11 does not rotate.

  When three-dimensionally observing a sample piece having a shape other than the shape shown in FIG. 2, for example, a sample having an observation object attached to the tip of a support rod or a biological sample having various shapes, the sample table 13 is set according to each sample shape. If a screw 16 common to the sample table 13 is provided below the processed sample table, it can be mounted on the common bar-shaped support 15. That is, only the sample stage needs to be processed according to the sample shape.

  When a sample piece is observed by another measuring device, the sample holder 13 can be commonly used by providing a screw hole corresponding to the screw for fixing the sample stage in the sample holder of the measuring device. For example, if a screw hole corresponding to the screw 16 is provided in a sample holder for a scanning electron microscope (hereinafter abbreviated as SEM) shown in FIG. 6, the processed shape of the sample piece can be observed by SEM with high resolution.

  Next, FIG. 8 shows a basic configuration of a focused ion beam processing apparatus which is a sample piece preparation apparatus for three-dimensional structure analysis. Liquid metal ion source 21, condenser lens 22, blanker 23, ion beam deflector 24, objective lens 25, sample holder 26, sample tilting mechanism 27, sample cooling mechanism 28, secondary ion detection and secondary ion mass analyzer 29, It comprises a computer 30 for image recording and control. As the sample holder 26, another sample holder including the sample holder 5 can be used. The deflector 24 can scan by an arbitrary scanning method under the control of the computer 30. The blanker 23 and the deflector 24 are controlled by the computer 30, and have a function of interrupting the irradiation of the sample piece 10 by the blanker 23 when the focused ion beam attempts to scan a designated area.

  Next, a method for preparing a three-dimensional analysis sample will be described. In this step, the sample piece 10 is processed into the shape shown in FIG.

  First, it is processed into a chip having a thick protrusion 11 using a dicer. In the processing accuracy of the dicer, the width of the projection 11 is several tens μm. As the above method, there are two methods: a method of forming the protrusion 11 and then cutting the chip, and a method of forming the protrusion 11 and then cutting the chip.

  First, the former procedure is shown in FIG. The wafer is set on a dicer, and portions other than the protrusions 11 are scraped off using a thicker dicer 31 (FIG. 9A). Thereafter, a chip having a size that can be fixed to the sample table 13 shown in FIG. 3 is cut out with a thin dicer 31 (FIG. 9B). This method is effective for a sample in which the same processing pattern is repeated in a wafer.

  Next, the latter procedure is shown in FIG. After the wafer is cut into chips by the dicer 31, portions other than the protrusions are cut or cut by the dicer 31. In the former method, only protrusions 11 perpendicular to the wafer surface, that is, protrusions 11 in the same direction as the crystal growth direction can be formed, whereas in the present method, protrusions 11 in any direction can be formed.

  Next, a step of fixing the sample piece 10 to the sample table 13 with the center axis of the thick protrusion 11 and the sample tilt axis aligned will be described. If the sample piece 10 deviates significantly from the center of the sample table 13, it will hinder the subsequent steps. For example, when processing the focused ion beam while rotating the sample piece 10, if the projection 11 moves due to the rotation of the sample piece 10, the processing accuracy of the projection 11 decreases. If the displacement is large, a device for correcting it is necessary. For example, a sample holder fine movement mechanism for correcting the position shift, a focused ion beam irradiation mechanism for following the position shift, and the like are required.

  In order to make the center axis of the projection 11 coincide with the specimen tilt axis, a method of setting the specimen table 13 so that the cross pattern 18 inserted into the optical microscope and the straight line connecting the mark 17 of the specimen table 13 coincide (FIG. 5 (a)) and while rotating the sample stage 13 as shown in FIG. 5 (b), observe the movement of the center of the projection 11 with an optical microscope, and adjust the sample position so that the center position of the projection 11 does not rotate. Use the method of fine adjustment.

  Next, FIGS. 11 and 12 show a process of using the focused ion beam to thin the projection 11 to a thickness that allows transmission of an electron beam. In the above-mentioned process, there is a method in which the focused ion beam is incident from a direction substantially parallel to the central axis z of the projection 11 and a method perpendicular to the direction.

  First, FIG. 11 shows a process in which the focused ion beam 33 is incident from a direction substantially parallel to the central axis z of the projection 11. The sample piece 10 is placed in a focused ion beam sample chamber such that the central axis z of the projection 11 and the incident direction of the focused ion beam 33 are parallel, and a secondary ion image is observed. This observation image is input to the computer and displayed on the image display device, and the projection area 111 is designated. The mark 32 is marked using the focused ion beam at the center of the projection region 111, that is, at the position to be the tip of the projection after processing. This is because it is generally difficult to specify the position of the analysis target 12 in the projection from the image obtained by observing the thinned projection 11 in the z-axis direction. Note that a sample that loses the position of the observation target when processed into the thick protrusion 11 needs to be marked 32 before processing into the thick protrusion 11. In addition, since the thickness of the projection 11 near the observation target is reduced to 100 nm or less by this step, the projection is very easily damaged. In order to prevent the breakage of the projection, it is desirable that the shape of the projection is conical rather than cylindrical.

In the conventional focused ion beam processing method, the focused ion beam 33 is scanned on the sample as shown in FIG. In this method, the focused ion beam 33 must be scanned while leaving the projection region 111. For example, when the projection region 111 is designated as shown in FIG. 11A, only the region other than the projection can be deleted by scanning the focused ion beam 33 in a circular shape as shown in FIG. 11B. c)). When it is desired to process the beam into a shape such as an ellipse or a square, the focused ion beam 33 may be scanned in an ellipse or a square. When the projection is formed in a conical shape, the focused ion beam scanning speed in the vicinity of the center is adjusted to be faster than that in the vicinity of the periphery so that the vicinity of the center of the projection remains.
This method can be realized by rewriting the control program of the focused ion beam deflector of the conventional focused ion beam processing apparatus.

  As another method, there is a method using a blanker 23 controlled by a computer as shown in FIG. The focused ion beam 33 scans in the same manner as in the related art (FIG. 12A). When the focused ion beam 33 scans the protruding region 111, the focused ion beam irradiation is interrupted by a computer-controlled blanker (FIG. 12B). )). When the projection is formed in a conical shape, the focused ion beam irradiation interruption region is concentrically enlarged or reduced so that the vicinity of the center is adjusted. In the processing method shown in FIG. 11, the focused ion beam scanning mode is different from the TV scanning mode, so that a secondary ion image of the sample cannot be obtained during the processing. Processing can be performed while constantly monitoring on the TV screen.

  Next, a step of injecting the focused ion beam 33 from a direction substantially orthogonal to the central axis z of the protrusion 11 will be described. The sample piece 10 is placed in a focused ion beam sample chamber such that the central axis z of the projection 11 is orthogonal to the incident direction of the focused ion beam 33, and a secondary ion image is observed. For example, as shown in FIG. 13A, a mark 32 is marked near the root of the projection. The projection region 111 is designated, and the other regions are deleted by irradiating the focused ion beam 33. When the deletion of the region is completed, the sample is tilted, and the above steps are repeated (FIG. 13B), and the sample is processed into a desired shape (FIG. 13C). In the method of processing by setting the incident direction of the focused ion beam 33 and the central axis z of the projection 11 in parallel, observation was possible only from directly above the projection 11 during sample processing. Since observation is possible, the position of the observation target can be specified while referring to the device pattern shape near the root of the protrusion 11.

  Alternatively, the focused ion beam 33 may be irradiated while rotating the sample piece 10. As shown in FIG. 14, the focused ion beam 33 is irradiated while rotating the sample piece 10 around the Z axis. At that time, the incident position of the focused ion beam 33 is designated by being shifted from the position of the central axis Z of the projection 11 by a desired radius R. The incident angle θ of the focused ion beam 33 to the sample surface is a steep angle (θ1) when the projection radius r is large, so that the sample damage is large but the processing speed is high (FIG. 15A). As the projection radius r becomes smaller, the sample incident angle becomes smaller (θ2), so that the processing speed becomes slower but the sample damage is reduced (FIG. 15B). When the projection radius r becomes smaller than the desired radius R, the focused ion beam irradiation automatically ends (FIG. 15C).

  If the position of the center axis z of the protrusion 11 is shifted from the position of the sample rotation axis Z, the position of the center axis of the protrusion 11 is shifted when the sample is rotated. Is measured and input to a computer, and the focused ion beam is scanned while synchronizing with the rotation of the sample so as to track the positional deviation. This method has a feature that a projection smaller than the beam diameter of the focused ion beam can be relatively easily formed. In addition, since sample damage is reduced as the processing proceeds, it is effective as a sample finishing step.

  The sample is processed using the above method. To determine whether the sample has been processed into a desired shape, shape observation using a secondary ion image, composition analysis using secondary ion mass spectrometry, high spatial resolution shape observation using a secondary electron image, or the like is used.

  In the process of processing into a projection, the analysis target may be determined after the sample is observed. In other words, there are a plurality of locations that may cause a defect in a certain device, and a region to be three-dimensionally analyzed may not be determined unless observed with a TEM image. For example, as shown in FIG. 16, when a part of the pattern shape is disconnected, first, the sample is processed into a plate shape as shown in FIG. After the identification, the projection is processed into a projection (FIG. 16 (b)) including the observation target 12, and the disconnection state is observed three-dimensionally.

  Observation of the sample piece 10 produced by the above-described process is performed in the same manner as conventional TEM observation. A sample table 13 on which the sample piece 10 is fixed is fixed to a rod-like support 15 in a holding cylinder 14, inserted into a TEM sample chamber, and irradiated with an accelerated electron beam to the observation object 12 to obtain a TEM image. The three-dimensional structure is observed while the observation target 12 is freely tilted around the z-axis.

  According to the present invention, for example, a three-dimensional distribution of a device pattern shape near a certain defective portion and a precipitate around the device pattern can be directly evaluated. Further, the present technology makes it possible to obtain a projected image in all directions, and the necessary conditions for three-dimensional reconstruction are satisfied for the first time. According to the present method, it is possible to reconstruct an arbitrary-shaped structure from only one sample piece.

When the region of the observation target 12 is wide, the diameter 2R of the projection including the observation target 12 is inevitably large. When the diameter 2R of the projection increases, the number of electrons scattered in the sample increases, and the spatial resolution of the observed image decreases.
When a normal TEM image is obtained at an acceleration voltage of 100 kV to 300 kV, the observation is performed with the sample thickness set to about several tens of nm. If the thickness is further increased, the observation image becomes unclear. For the observation of a thick film sample, removal of inelastic scattered electrons using an energy filter is effective. If non-scattered electrons are removed by setting the slit of the energy filter so that only elastic scattered electrons can pass among the electrons that have passed through the sample, a sample several times thicker than without a filter can be observed. Become.

1 is an overall configuration diagram of a transmission electron microscope used in an example of the present invention. The conceptual diagram which shows the shape of the sample piece for three-dimensional observation. The block diagram of the sample stand in which a sample piece is installed. FIG. 3 is a configuration diagram of a uniaxial omnidirectional sample holder. Explanatory drawing of adjustment of the processing position of a sample piece. Sectional drawing of the standard sample holder for SEM. The block diagram of the sample damage protection cover. FIG. 1 is a basic configuration diagram of a focused ion beam processing apparatus according to one embodiment of the present invention. Explanatory drawing which shows the process which cuts out a thick protrusion using a dicer. Explanatory drawing which shows the process which cuts out a thick protrusion using a dicer. Explanatory drawing of the process of processing a sample piece. Explanatory drawing of the process of processing a sample piece. Explanatory drawing of the process of processing a sample piece. Explanatory drawing of the process of processing a sample piece. FIG. 4 is an explanatory diagram illustrating a relationship between a radius of a protrusion formed on a sample piece and an ion beam processing position. Explanatory drawing of the observation target part on a sample piece. FIG. 4 is an explanatory diagram of the projection cut plane theorem.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Condenser lens, 3 ... Electron deflection coil, 4 ... Objective lens, 5 ... Sample holder, 6 ... Sample tilting mechanism, 7 ... In-column type energy filter, 8 ... Image recording device, 9 ... Control Computer with software for image processing and software for image processing, 10: sample piece, 11: protrusion, 12: observation target, 13: sample table, 14: holding cylinder, 15: rod-shaped support, 16: screw for fixing the sample table, 17: mark for adjusting the position of a sample piece, 18: cross pattern inserted on the optical axis of an optical microscope, 19: sample stage rotating device, 20: standard sample stage for SEM, 21: liquid metal ion source, 22: condenser Lens, 23 Blanker, 24 Ion beam deflector, 25 Objective lens, 26 Sample holder, 27 Sample tilting mechanism, 28 Sample cooling mechanism, 29 Mass analyzer, 30 Image recording device and control computer , 31 ... L'Yser, 32 ... mark used in the location reference of the observation object, 33 ... ion beam, 34 ... sample damage protective cover, 35 ... post-column type energy filter, 111 ... projection area.

Claims (23)

  A focused ion beam processing device consisting of an ion source, a condenser lens, an objective lens, a sample holder, a sample rotating / moving mechanism, a sample cooling mechanism, a mass analyzer, an image recording device, and a control computer. A sample preparation apparatus for three-dimensional structure observation, comprising: an ion beam deflector for processing a sample into a shape having a portion; an ion beam control mechanism; and a blanker.   3. A three-dimensional structure observation sample preparation apparatus according to claim 1, wherein the shape having the projection portion including the observation target has a value such that a diameter of the projection can be observed by a transmission electron microscope image.   The means for processing a sample according to claim 1 records a two-dimensional observation image of the sample, designates an area to be processed into a projection including an observation target in the two-dimensional observation image, and scans an area other than the area with an ion beam. And a means for controlling the ion beam deflector so as to perform the operation.   The means for processing a sample according to claim 1 records a two-dimensional observation image of the sample, designates a projection region including an observation target in the two-dimensional observation image, scans the sample with an ion beam, and scans the ion beam. An apparatus for preparing a three-dimensional structure observation sample, comprising means for interrupting ion irradiation by a computer-controlled blanker when the incident position scans the projection region.   The means for processing a sample according to claim 1 is a means for rotating the sample around a central axis of the projection, and an ion beam is incident from a direction perpendicular to the central axis of the projection, and the radius of the projection becomes a desired value. An apparatus for preparing a three-dimensional structure observation sample, comprising: means for removing a projection surface up to the projection.   An electron microscope consisting of an electron gun, an electron lens, an electron beam deflection coil, a sample holder, a sample rotation / movement mechanism, an energy filter, an image recording device, and a computer equipped with control software and image processing software. A sample holder capable of rotating a sample having a protruding portion by 360 ° around a rotation axis orthogonal to an incident electron beam in a sample chamber, and a means for observing a three-dimensional structure of the sample, comprising: microscope.   7. The sample holder according to claim 6, comprising a sample table, a rod-shaped support, and a holding cylinder, wherein said rod-shaped support can be rotated by 360 ° around the sample rotation axis in the holding cylinder, and the rotation axis of the rod-shaped support and the sample table. 3. An electron microscope for three-dimensional structure observation, comprising: means for making the rotation axes of the sample table coincide with each other and fixing the same, and means for making the rotation axis of the sample table coincide with the center axis of the projection.   An electron microscope for three-dimensional structure observation, wherein the sample stage according to claim 7 is provided with a protective cover for preventing breakage of the projection.   The means for fixing the rotation axis of the rod-shaped support and the rotation axis of the sample stage so as to coincide with each other is a screw and a screw hole provided at the lower part of the sample stage and at the tip of the rod-shaped support. Electron microscope for three-dimensional structure observation.   The means for fixing the rotation axis of the sample table and the central axis of the projections in accordance with claim 7 is a plurality of sets of marks provided on the sample table, and the intersection of a straight line connecting the marks of each set is the cross point of the sample table. An electron microscope for observing a three-dimensional structure, comprising means for adjusting the position of the sample with respect to the sample stage so that the center of the projection coincides with the intersection point on the rotation axis.   The means for fixing the rotation axis of the sample stage and the central axis of the projection according to claim 7 is a device for rotating the sample stage around the rotation axis of the sample stage. An electron microscope for observing a three-dimensional structure, comprising means for finely adjusting the position of the sample with respect to the sample stage so that the center axis of the projection of the sample mounted on the sample stage does not move when the sample stage is placed.   A step of processing the sample into a shape having a projection including the observation target, a step of fixing the sample of the above shape to a sample holder, and obtaining a plurality of transmission electron microscope images obtained by observing the sample from any direction around one axis A three-dimensional structure observation method, comprising: constructing a three-dimensional structure of an observation target from the plurality of transmission electron microscope images.   13. The three-dimensional structure observation method according to claim 12, wherein a diameter of the projection is 100 nm or less at an incident voltage of 100 kV to 300 kV of a transmission electron microscope.   The step of processing the sample into the shape according to claim 12 is such that a two-dimensional observation image of the sample is recorded and input to a computer to set a projection region, and the ion beam scans only the periphery of the region. A three-dimensional structure observation method including a step of deleting only a portion other than a protrusion by controlling an ion beam deflector by a computer.   The step of processing the sample into the shape according to claim 12 includes recording a two-dimensional observation image of the sample, inputting the image to a computer, setting a projection region, scanning the sample with an ion beam, and setting the ion beam incident position to A method for observing a three-dimensional structure, comprising the step of interrupting ion irradiation using a blanker when scanning the above-mentioned projection region to delete only a portion other than the projection.   13. The step of processing the sample into the shape according to claim 12, wherein the step of rotating the sample around the central axis of the projection, inputting an ion beam from a direction perpendicular to the central axis of the projection, and removing the surface of the projection. A three-dimensional structure observing method, comprising a step of processing a surface to a desired radius.   17. The projecting central axis due to a displacement of the sample tilt axis and the central axis of the projection according to claim 16, wherein the step of injecting the ion beam from a direction perpendicular to the central axis of the projection while rotating the sample around the central axis of the projection. A three-dimensional structure observation method, comprising a step of scanning an ion beam while tracking the rotation of the ion beam.   In the step of processing the projection to a desired radius according to claim 16, by setting the ion beam incident position to a position of a desired radius, when the projection radius is larger than the desired radius, the ion beam incident angle with respect to the projection surface becomes larger. A three-dimensional structure observing method, which includes a step of performing a roughing process because the size becomes large, and a finishing process because the size becomes small when the radius approaches a desired radius.   The step of fixing the sample according to claim 12 to the sample holder uses a plurality of sets of marks provided on the sample table, and the center axis of the rotation axis of the sample table and the central axis of the projection, which is the intersection of straight lines connecting the marks of each set, are used. A three-dimensional structure observation method, which comprises a step of finely adjusting a position of a sample with respect to a sample stage so as to be coincident, and fixing the sample so that a center axis of a projection and an inclination axis of the sample stage are aligned.   The step of fixing the sample to the sample holder according to claim 12 is such that, when the sample is set on an apparatus for rotating the sample stage around the rotation axis of the sample stage and the sample stage is rotated, the central axis of the projection does not move. 3. A three-dimensional structure observation method, comprising the steps of: finely adjusting the position of the sample with respect to the sample table, fixing the center axis of the projection and the tilt axis of the sample table so as to coincide with each other.   A plurality of transmission electron microscope images obtained by observing the sample according to claim 12 from an arbitrary direction around one axis are images formed by electrons of a specific energy by an energy filter among electron beams passing through the sample. A three-dimensional structure observation method characterized in that:   A plurality of transmission electron microscope images obtained by observing the sample according to claim 12 from an arbitrary direction about one axis are images formed by high-angle scattered electrons among electron beams passing through the sample, and electron scattering of the sample is performed. A three-dimensional structure observation method, wherein the function and the image contrast can be approximated to a linear relationship. The step of constructing a three-dimensional structure of an observation object from a plurality of transmission electron microscope images according to claim 12 includes a step of using the transmission electron microscope image as a projection image and reconstructing the projection image. 3D structure observation method.

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