JP4433092B2 - Three-dimensional structure observation method - Google Patents

Description

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

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-dimensional evaluation of the structure of a semiconductor device manufactured by overlaying various pattern shapes.

  In response to these requirements, attempts have been made to observe the three-dimensional structure of a sample using a TEM. Hereafter, the procedure of the conventional observation method is shown.

  First, in order to observe the TEM image to be observed, the sample is thinned. The distance through which the electron beam can pass through the sample is short. When the transmission voltage of the transmission electron microscope is 100 to 300 kV, the distance through which the electron beam can be transmitted is 100 nm or less. In order to make the thickness of the observation object 100 nm or less, the sample is thinned to about 100 μm using an abrasive. Further, the vicinity of the observation object is polished into a mortar shape to a thickness of several tens of μm, and then thinned to 100 nm or less 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 table, and the periphery of the sample table is fixed to a sample holder shown in, for example, the method and apparatus for supporting an electron microscope described in Japanese Patent Laid-Open No. 6-139986. Insert into the chamber and observe the TEM image to be observed. In order to evaluate the three-dimensional structure, a TEM image observed from a plurality of directions with the sample piece tilted in the sample chamber is used.

  Furthermore, in order to quantitatively evaluate the three-dimensional structure, a 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, a high-angle scattering image formed by electrons scattered at a high angle by atoms in the sample using a three-dimensional atomic array observation apparatus described in Japanese Patent Application No. 3-110126. It is necessary to use an electronic image. This is because the contrast of the TEM image includes not only the scattering contrast mainly reflecting the electron scattering ability but also the diffraction contrast mainly reflecting the crystal structure, and the diffraction contrast is reduced to use the TEM image as the projection image. It is necessary to make it. Using the above high angle scattered electron image, the three-dimensional structure is reconstructed by the method described in Japanese Patent Application No. 3-110126. First, each two-dimensional section is reconstructed using the projected cutting plane theorem, and these are stacked to construct a three-dimensional structure.

JP-A-3-110126

  In the conventional TEM observation sample piece, the observation target exists in the vicinity of the center of the sample piece processed into a mortar shape. In such a shape, when the sample piece is tilted greatly, the thickness of the sample through which the electron beam passes is increased, 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 tilted greatly, the ring-shaped sample stage and the sample holder block 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 sample tilt angle range is limited, and the observation target cannot be observed from any direction. In general-purpose TEM, the tilt angle range is about ± 60 degrees. The higher the spatial resolution TEM, the narrower the gap of the electron lens, the narrower the sample chamber into which the sample holder is inserted. It is narrower.

  Furthermore, the limitation of the sample tilt angle range is a very big obstacle in three-dimensional reconstruction. The projection plane cutting theorem used in image reconstruction is that the one-dimensional Fourier transform of the projection data p (r, θ) from the θ direction of the sample f (x, y) is the two-dimensional Fourier transform F (μ, This is the theorem that coincides with the line profile of the cut surface in the θ direction of ν) (FIG. 17A). In other words, if projection data in all directions is obtained, all information related to 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 projection angle limit, severe artifacts are generated on the reconstruction image, and the sample structure may not be analyzed due to the artifacts. Although methods for reducing the artifacts by image restoration processing have been studied, various assumptions regarding the sample structure are necessary, and sample shapes to which the restoration processing can be applied are limited. There have also been attempts to prepare multiple samples of the same structure and thin the sample from different directions to obtain a projected image of the sample in all directions. It was not applicable when there was only one.

  In the present invention, a sample piece processed into a shape having a protruding portion that encloses an observation target is used as the three-dimensional observation sample piece. In the sample piece, the observation object can be observed from all directions around the central axis of the protrusion. A dicer, a focused ion beam processing apparatus, or the like is used to process the sample piece into the above shape. The focused ion beam processing apparatus includes an ion beam deflector and a blanker for producing a protrusion that encloses an observation target. Furthermore, a uniaxial omnidirectional sample holder is used as the sample holder. The uniaxial omnidirectional 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 inclined in all directions of the uniaxial axis. If the sample piece is placed at the tip of the rod-shaped support so that the center axis of the protrusion and the sample tilt axis are aligned, the observation object can be observed inclined 360 ° around the center axis of the protrusion. That is, a TEM image in all directions of the observation target can be obtained.

  By using the present invention, it is possible to obtain a TEM image obtained by observing the observation target from an arbitrary direction around the central axis of the protrusion, so that a three-dimensional sample structure can be directly evaluated. In addition, observation of projection images in all directions, which are necessary conditions for reconstructing the three-dimensional structure of the sample, is realized. Therefore, it is not necessary to use known information about the sample, and any sample shape can be accurately reconstructed from one sample piece.

  According to the present invention, a sample structure at an arbitrary shape and an arbitrary position in a three-dimensionally constructed device structure is analyzed three-dimensionally to provide important information regarding device process check and optimization and device design. be able to.

The whole block diagram of the transmission electron microscope used in the Example of this invention. The conceptual diagram which shows the shape of the sample piece for three-dimensional observation. The block diagram of the sample stand which installs a sample piece. The block diagram of a uniaxial omnidirectional sample holder. Explanatory drawing of the processing position adjustment of a sample piece. Sectional drawing of the standard sample holder for SEM. The block diagram of a sample breakage protection cover. The basic block diagram of the focused ion beam processing apparatus of one Example of this invention. Explanatory drawing which shows the process of cutting out a thick protrusion using a dicer. Explanatory drawing which shows the process of cutting out a thick protrusion using a dicer. Explanatory drawing of the process process of a sample piece. Explanatory drawing of the process process of a sample piece. Explanatory drawing of the process process of a sample piece. Explanatory drawing of the process process of a sample piece. Explanatory drawing which shows the relationship between the radius of the projection part formed in a sample piece, and an ion beam processing position. Explanatory drawing of the observation object part on a sample piece. Explanatory drawing of a projection cut surface theorem.

  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 tilt mechanism 6, in-column type 7 or post-column type 35 energy filter, image It comprises a recording device 8 and a computer 9 provided with 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 protruding portion 11 on a certain surface. The central axis of the protrusion 11 is the z axis. The protruding portion 11 includes the observation object 12. The diameter 2R of the protrusion in the region is set within a range where the electron beam can pass. The diameter 2R depends on the acceleration voltage of the incident electron beam, and the distance through which the electron beam passes increases as the acceleration voltage increases. In the case of an acceleration voltage of 100 to 300 kV, 2R is 100 nm or less, and in the case of 3 MV, it is 10 μm or less.

  The sample piece 10 is fixed to a sample table 13 shown in FIG. At the upper part of the sample stage 13, a stage for installing the sample piece 10 is provided, and at the lower part, a screw 16 for fixing the sample stage 13 to the rod-like support 15 is provided. There are a sample table (FIG. 3A) for fixing the sample piece 10 with an adhesive and a sample table (FIG. 3B) for fixing with a screw.

  3A, the upper part 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, it is easy to downsize. The sample stage 13 in FIG. 3 (b) has a concave part for placing the sample on the upper part of the sample stage 13, and the sample piece 10 is fixed by four screws 40 attached to the outer frame of the concave part. In this structure, fine adjustment of the sample position in the sample table can be performed with four screws. In addition, since the sample piece 10 can be easily detached, it is possible to observe the same sample piece 10 after processing the sample piece 10 once observed with 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 uniaxial omnidirectional sample holder has a bar-like support 15 supported by a holding cylinder 14, and the bar-like support 15 can be tilted in all directions on one axis. The sample tilt axis direction is the Z axis, the incident direction of the electron beam is the Y axis, and the direction perpendicular to the two axes is the X axis. Similar to the conventional TEM sample holder, 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. The sample stage 13 to which the sample piece 10 is fixed is attached by inserting a screw 16 below the sample stage 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 table 13 in order to prevent the protrusion 11 from being destroyed when the sample table is fixed. The protective cover 34 has a cylindrical shape, and has a vertically long hole in the side surface. If the protective cover 34 is raised and fixed with the screw 41 as shown in FIG. 7A, it is possible to considerably prevent the protrusion 11 from being accidentally broken during the operation. When processing and observing the protrusion 11 from the side, the protective cover 34 is lowered and fixed with screws 41 as shown in FIG.

  Since the center axis of the screw 16 and the sample tilt axis Z coincide with each other, when the rod-shaped support 15 is tilted, the sample stage 13 tilts around the center axis of the screw 16. Furthermore, if the sample piece 10 is fixed to the sample stage 13 with the center axis of the protrusion 11 and the center axis of the screw 16 aligned, the protrusion 11, that is, the observation object 12 can be observed tilted in one axis in all directions.

  For example, there are the following two apparatuses for aligning the center axis z of the protrusion 11 with the sample tilt axis Z.

  One is to use an optical microscope in which a mark 17 provided on the sample stage 13 as shown in FIG. 5A and a cross pattern 18 are inserted on the optical axis. Two marks 17 are assembled so as to face the upper part of the sample stage 13, and a straight line connecting the marks intersects with the Z axis when the sample stage 13 is fixed to the rod-shaped support 15. If the sample stage 13 is installed so that the straight line connecting the marks 17 of the sample stage 13 and the cross pattern 18 coincide, and the sample is fixed to the sample stage 13 so that the tip of the protrusion 11 coincides with the center of the cross pattern 18, The central axis z of the protrusion 11 coincides with the sample tilt axis Z of the sample holder.

  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 central axis of the screw 16. The sample stage 13 on which the sample piece 10 is placed is rotated, and the movement of the protrusion 11 is observed with an optical microscope. If the center axis z of the protrusion 11 coincides with the sample stage and the rotation axis, the center position of the protrusion 11 does not rotate.

  In addition, when observing a sample piece other than the shape shown in FIG. 2, for example, a sample in which an observation target is attached to the tip of a support bar or a biological sample of various shapes, in three dimensions, the sample stage 13 is set according to each sample shape. If a common screw 16 with the sample stage 13 is provided at the lower part of the processed sample stage, it can be attached to the common bar-shaped support 15. In other words, only the sample stage may be processed according to the sample shape.

  Further, when observing a sample piece with another measuring device, the sample table 13 can be used in common if a screw hole corresponding to the sample table fixing screw is provided in the sample holder of the measuring device. For example, if a screw hole suitable for 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 with high-resolution SEM.

  Next, FIG. 8 shows a basic configuration of a focused ion beam processing apparatus which is a three-dimensional structural analysis specimen preparation apparatus. Liquid metal ion source 21, condenser lens 22, blanker 23, ion beam deflector 24, objective lens 25, sample holder 26, sample tilt mechanism 27, sample cooling mechanism 28, secondary ion detection and secondary ion mass analyzer 29 and It is composed of 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 be scanned by an arbitrary scanning method under the control of the computer 30. The blanker 23 and the deflector 24 are controlled by a computer 30 and have a function of interrupting ion irradiation to the sample piece 10 by the blanker 23 when the focused ion beam attempts to scan a specified region.

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

  First, a chip having a thick protrusion 11 is processed using a dicer. In the processing accuracy of the dicer, the width of the protrusion 11 is several tens of μm. As the above method, there are two methods, that is, a method in which the protrusion 11 is formed and then cut into chips, and a method in which the protrusion 11 is formed after cutting into chips.

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

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

  Next, a step of fixing the sample piece 10 to the sample stage 13 with the central axis of the thick protrusion 11 and the sample tilt axis aligned with each other is shown. If the sample piece 10 deviates greatly from the center of the sample stage 13, it will be an obstacle to the subsequent process. For example, when processing the focused ion beam while rotating the sample piece 10, if the protrusion 11 moves due to the rotation of the sample piece 10, the processing accuracy of the protrusion 11 is lowered. When the positional deviation is large, a device for correcting it is necessary. For example, a sample holder fine movement mechanism that corrects the positional deviation, a focused ion beam irradiation mechanism that follows the positional deviation, and the like are required.

  In order to make the center axis of the projection 11 coincide with the sample tilt axis, the sample stage 13 is set so that the cross pattern 18 inserted into the optical microscope and the straight line connecting the mark 17 of the sample stage 13 coincide (FIG. 5 (a)) or the movement of the center of the protrusion 11 is observed with an optical microscope while rotating the sample stage 13 as shown in FIG. 5 (b), and the sample position is adjusted so that the center position of the protrusion 11 does not rotate. Use a fine-tuning method.

  Next, FIGS. 11 and 12 show a process of thinning the protrusion 11 to a thickness that allows transmission of an electron beam using a focused ion beam. There is a method in which the focused ion beam is incident from a direction orthogonal to a method in which the focused ion beam is incident from a direction substantially parallel to the central axis z of the protrusion 11.

  First, FIG. 11 shows a step in which the focused ion beam 33 is incident from a direction substantially parallel to the central axis z of the protrusion 11. The sample piece 10 is placed in the focused ion beam sample chamber so 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 region 111 is designated. The mark 32 is marked by using a focused ion beam at the center of the projection region 111, that is, at the position that becomes 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 an image obtained by observing the thinned projection 11 from the z-axis direction. Note that a sample that loses the position of the observation target when it is processed into the thick protrusion 11 needs to have a mark 32 before it is processed into the thick protrusion 11. In addition, since the thickness of the protrusion 11 near the observation target is 100 nm or less by this step, the protrusion is very easily damaged. In order to prevent breakage of the protrusion, it is desirable that the protrusion shape be 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. c)). When processing into a shape such as an ellipse or a square, the focused ion beam 33 may be scanned into an ellipse or a square. When the protrusion shape is conical, the focused ion beam scanning speed in the vicinity of the center is adjusted to be higher than that in the vicinity of the periphery so that the vicinity of the protrusion center remains. This method can be realized by rewriting the control program for the focused ion beam deflector of the conventional focused ion beam processing apparatus.

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

  Next, a process in which the focused ion beam 33 is incident from a direction substantially orthogonal to the central axis z of the protrusion 11 will be described. The sample piece 10 is placed in the focused ion beam sample chamber so that the central axis z of the protrusion 11 and the incident direction of the focused ion beam 33 are orthogonal to each other, and a secondary ion image is observed. For example, as shown in FIG. 13A, a mark 32 is marked near the root of the protrusion. The projection region 111 is designated, and other regions are deleted by irradiating the focused ion beam 33. When the deletion of the region is completed, the sample is tilted, the above process is repeated (FIG. 13B), and the sample is processed into a desired shape (FIG. 13C). In the processing method in which the incident direction of the focused ion beam 33 and the central axis z of the protrusion 11 are set in parallel, it can be observed only from directly above the protrusion 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.

Further, 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 this time, the incident position of the focused ion beam 33 is specified by being shifted from the position of the central axis Z of the protrusion 11 by a desired radius R. The incident angle θ of the focused ion beam 33 with respect to the sample surface is incident at 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 decreases, the sample incident angle decreases (θ2
Therefore, the processing speed is reduced, 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 is automatically terminated (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. The position is measured and input to a computer, and the focused ion beam is scanned while synchronizing with the sample rotation so as to track the positional deviation. This method is characterized in that a projection thinner than the beam diameter of the focused ion beam can be produced relatively easily. In addition, since the sample damage is reduced as the processing proceeds, it is effective as a sample finishing step.

  The sample is processed using the above method. Judgment of whether the sample has been processed into a desired shape uses shape observation by secondary ion image, composition analysis by secondary ion mass spectrometry, shape observation with high spatial resolution by secondary electron image, or the like.

  Note that, in the process of processing into a protruding shape, the analysis target may be determined after observing the sample. In other words, there are a plurality of locations that can cause defects in a certain device, and there are cases where an area to be analyzed three-dimensionally cannot be determined unless it is 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 specifying, it processes into the protrusion (FIG.16 (b)) which includes the said observation object 12, and observes a disconnection state three-dimensionally.

  Observation of the sample piece 10 produced by the above process is performed in the same manner as conventional TEM observation. A sample stage 13 on which a 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 12 to obtain a TEM image. The three-dimensional structure is observed while the observation object 12 is freely tilted around the z axis.

  By using the present invention, it is possible to directly evaluate, for example, the device pattern shape in the vicinity of a certain defective portion and the three-dimensional distribution of precipitates in the vicinity thereof. In addition, this technology makes it possible to obtain an omnidirectional projection image, and the requirement for three-dimensional reconstruction is satisfied for the first time. With this method, it is possible to reconstruct a structure of an arbitrary shape from only one sample piece.

  In addition, when the area | region of the observation object 12 is wide, the diameter 2R of the processus | protrusion which encloses the observation object 12 will necessarily become large. When the diameter 2R of the protrusion is increased, the number of electrons scattered in the sample increases, so that the spatial resolution of the observation image is reduced. When a normal TEM image is obtained at an acceleration voltage of 100 kV to 300 kV, the sample is observed with a thickness of several tens of nanometers. If the sample is thicker than this, the observed image becomes unclear. Removal of inelastically scattered electrons using an energy filter is effective for thick film sample observation. If the slit of the energy filter is set so that only the elastic scattered electrons among the electrons that have passed through the sample can be passed and the non-scattered electrons are removed, the sample can be observed several times thicker than the case without the filter. Become.

  DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Condenser lens, 3 ... Electron deflection coil, 4 ... Objective lens, 5 ... Sample holder, 6 ... Sample inclination mechanism, 7 ... In-column type energy filter, 8 ... Image recording device, 9 ... Control A computer equipped with software for image processing and software for image processing, 10 ... sample piece, 11 ... protrusion, 12 ... observation object, 13 ... sample stand, 14 ... holding cylinder, 15 ... rod-shaped support, 16 ... screw for fixing the sample stand, DESCRIPTION OF SYMBOLS 17 ... Mark for sample piece position adjustment, 18 ... Cross pattern inserted on the optical axis of optical microscope, 19 ... Sample stage rotation apparatus, 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 spectrometer, 30 ... Image recording device and control computer 31 ... Dicer, 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 (7)

A method for observing a three-dimensional structure of a sample using a transmission electron microscope,
Producing the sample having a protrusion containing the observation object by a focused ion beam;
Installing a sample stage on which the sample is placed between the upper and lower poles of the electron lens of the transmission electron microscope;
Irradiating an electron beam while tilting the observation target in an arbitrary direction around the central axis of the protrusion, and obtaining a projection image in all directions of the observation target;
A three-dimensional analysis of the structure of the sample from the omnidirectional projection image;
A support that can be tilted at an arbitrary angle with respect to the central axis of the protrusion is attached to the sample stage.
At least a part of the holding cylinder that supports the support is disposed between the upper pole and the lower pole of the electronic lens,
Three-dimensional structure observation for irradiating the observation object with an electron beam while tilting the sample stage around the central axis of the protrusion independently of the holding cylinder to obtain an omnidirectional projection image of the observation object Method. A method for observing a three-dimensional structure of a sample using a transmission electron microscope,
Producing a sample having a cylindrical or conical protrusion including an observation target by a focused ion beam;
Installing a sample stage on which the sample is placed between the upper and lower poles of the electron lens of the transmission electron microscope;
Irradiating the observation target with an electron beam while tilting the support fixture fixing the sample stage in one axis in all directions with respect to the sample tilt axis to obtain a projection image in all directions of the observation target;
Reconstructing the three-dimensional structure of the sample from the omnidirectional projection image;
A support that can be tilted at an arbitrary angle with respect to the central axis of the protrusion is attached to the sample stage.
At least a part of the holding cylinder that supports the support is disposed between the upper pole and the lower pole of the electronic lens,
Three-dimensional structure observation for irradiating the observation object with an electron beam while tilting the sample stage around the central axis of the protrusion independently of the holding cylinder to obtain an omnidirectional projection image of the observation object Method. The three-dimensional structure observation method according to claim 2,
A three-dimensional structure observation method in which the sample is fixed to the sample stage with the sample tilt axis and the central axis of the protrusion aligned. The three-dimensional structure observation method according to claim 1 or 2,
A three-dimensional structure observation method of irradiating the focused ion beam in synchronization with an inclination around the central axis of the projection so as to track a positional deviation between the sample and the sample stage caused by the inclination. The three-dimensional structure observation method according to claim 1 or 2,
Displaying an observation image obtained by irradiating the sample with a focused ion beam on a display device;
Marking the sample with the focused ion beam based on the displayed observation image. The three-dimensional structure observation method according to claim 1 or 2,
A three-dimensional structure observation method in which the central axis of the protrusion is orthogonal to the incident direction of the focused ion beam. The three-dimensional structure observation method according to claim 1 or 2,
The step of producing the sample having the protrusion by a focused ion beam is as follows.
After the sample is processed by the focused ion beam, the observation target is specified by the transmission electron microscope;
And processing the protrusions including the specified observation object with the focused ion beam.

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