JPH04223034A - Scanning type electron microscope device and method of observation using it - Google Patents

Abstract

PURPOSE:To enable high-resolution observation of fine structure having deep unevenness of an optional surface by means of a clear image by not cutting but inclination of a semiconductor wafer by providing a rod-like magnetic path for magnetically connecting the first and second poles and both poles. CONSTITUTION:A first pole 1 is constituted to be symmetrical with respect to an axis while having a hole in its center and being cylindrical and having a flat tip. A second pole 7 is constituted to be cylindrical in opposition to first pole 1 and flat in its tip so as to form a magnetic field for focusing electron beams 12 together with the pole 1. Then, a rod-like magnetic path 7-1 is made to go through the hollow part of a movable table 9 to be connected to a pole 7 while inclination, rotation inside the face and movement of a sample 2 to be observed are carried out with the direction of the magnetic path 7-1 as an axis. Thereby, high-resolution observation is made practicable on the whole surface of a sample 2 of a huge size such as a wafer at an optional angle and in a short focal length. Accordingly, even on the whole wafer surface, inclined observation of fine structure having deep unevenness is practicable by means of a clear image of high contrast.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope apparatus for irradiating an electron beam focused by an objective lens onto a sample to be observed and observing its image, and an observation method using the same.

0002

2. Description of the Related Art In general, an objective lens of a conventional scanning electron microscope has a structure shown in FIGS. The axial magnetic field strength Bz (hereinafter referred to as longitudinal magnetic field strength) on the axis in this structure is shown in FIGS. 5A to 5B. The objective lens is usually cylindrically symmetrical with the electron beam path 43 as a common axis. Magnetic poles 41-1, 41-
A magnetic path 41 connecting the two is made of a magnetic material such as pure iron, and a current is passed through a coil 44 that provides magnetomotive force to generate a magnetic field between the magnetic poles 41-1 and 41-2. The electron beam passing through this magnetic field is converged and collides with the observation surface 46 of the wafer (semiconductor substrate) 42 to be observed, generating secondary electrons. The secondary electrons generated in this way leave the wafer 42 while making a spiral motion along the vertical magnetic field generated by the objective lens and the electric field applied in the axial direction, and the secondary electrons placed above the wafer 42 captured by the detector. The secondary electrons captured by the secondary electron detector are image-processed and displayed on a cathode ray tube.

In the conventional technology, when trying to improve the resolution of a scanning electron microscope, 2
It is possible to apply a uniform and strong vertical magnetic field to the secondary electrons and to minimize lens aberration. Below, three examples of conventional techniques that utilize the above principle are listed. A first example of the prior art is a scanning electron microscope having the structure shown in FIGS. This method attempts to obtain an image with small lens aberrations and little distortion by placing the lenses as close as possible. In this case, although it is possible to observe a relatively large sample, there is a limit to how close the sample to be observed can be to the intermediate position between the magnetic poles 41-1 and 41-2 because the lower magnetic pole 41-2 becomes an obstacle. Therefore, it is difficult to dramatically improve resolution. Furthermore, some scanning electron microscopes with this structure are provided with a tilting mechanism for large samples such as semiconductor wafers, but in practice, it is not possible to tilt the tilting mechanism to a large extent in order to obtain a certain resolution. Therefore, it is in a contradictory relationship with the realization of high resolution.

A second prior art example is shown in FIG.
) In this method, the wafer 42 is inserted into a position where the vertical magnetic field is strongest between the magnetic poles 41-1 and 41-2 of a scanning electron microscope having the structure, and the wafer 42 is observed under a strong vertical magnetic field. At the same time, this is the position where the focal length becomes small and the lens aberration becomes the smallest. For this type of usage, approx.
There are some that can be tilted within the operating range of 00 degrees. However,
In this case, the disadvantage is that only a small cut sample to be observed can be observed.

The third prior art example solves the shortcomings of the above two prior art examples in an average manner from the viewpoint of obtaining high resolution even for a huge sample such as a semiconductor wafer. This is an objective lens having the structure shown in (b)-(a). This structure can be said to be an intermediate structure between the first and second prior art examples. In this case as well, the aim is to detect secondary electron signals with high SN under a strong longitudinal magnetic field while reducing lens aberration. However, when the sample to be observed is a semiconductor wafer, the magnetic circuit must be extremely large in order to realize the structure shown in FIGS. Figure 5 (b)-(
b)).

[0006] Furthermore, it is extremely difficult to install a moving sample stage on which a wafer (sample to be observed) is mounted inside the magnetic pole.
Furthermore, it is extremely difficult in practice to provide a tilting mechanism. Next, consider the conventional technology from the viewpoint of SN (signal to noise ratio) of the secondary electronic signal. The decrease in SN is caused by a decrease in the yield of secondary electrons. The decrease in the yield of secondary electrons is because the cyclotron radius (Lamor radius), which is inversely proportional to the longitudinal magnetic field strength, increases due to the small longitudinal magnetic field strength, so some secondary electrons collide with the side walls of the observed fine structure. arises from doing. This situation is shown in Figure 6(a).
Shown below. FIG. 6 shows the difference in the behavior of secondary electrons depending on the strength of the longitudinal magnetic field. In particular, when observing a fine structure pattern with deep irregularities of submicron size or less, the above phenomenon becomes remarkable.

In order to prevent this phenomenon, a method of applying a stronger longitudinal magnetic field more actively to the third prior art example is proposed.
The 35th Japan Society of Applied Physics Related Conference in Spring 1988 [31
a-H-3] published by NTT LSI Laboratories. However, this device simply adds an auxiliary coil to the objective lens of a conventional scanning electron microscope to enhance the magnetic field.

[0008] Therefore, when observing a fine structure pattern (trench groove, contact hole, etc.) with deep irregularities of sub-micron size vertically or obliquely using conventional techniques, it is difficult to observe it with the highest resolution or to measure its dimensions. In order to do this, the sample to be observed was cut and the method shown in the second prior art example was used. FIG. 7 shows a SEM observation sequence diagram in the semiconductor manufacturing process. In the conventional technology, the wafer must be cut to observe the cross section, so the wafer used for observation cannot be returned to the manufacturing process. Therefore, there has been a problem that throughput and yield in the semiconductor manufacturing process are reduced, and development efficiency is reduced.

[0009]

However, with the above configuration, if the sample to be observed is a semiconductor wafer (generally a wafer with a diameter of 2 inches or more is used), the size of the sample is large; A structure with a built-in movable platform that can move in a plane perpendicular to the axial direction is required.
Because the magnetic path of the objective lens becomes an obstacle, the wafer is not cut and the magnetic poles 41-1 and 41-2 in FIG.
(Second prior art example).

[0010] Also, a third prior art example, (b)-
As shown in (a), the wafer can be inserted between the magnetic poles,
Even if a movable stage that can fix the wafer and move in a plane perpendicular to the axial direction could be incorporated, a working range twice the size of the wafer would be required to observe the entire wafer surface. Therefore, there was a problem in that the size of the magnetic path of the objective lens became enormous, making it difficult to realize. Furthermore, when attempting to observe the wafer at an angle, the wafer comes into contact with the magnetic pole, making it impossible to observe the wafer at an angle. In the case of the second embodiment ((a) of FIG. 5A), although it is possible to tilt, there is a problem in that it cannot be tilted unless the wafer is cut. Furthermore, by using the structure shown in (b) (a) in FIG. 5, a larger vertical magnetic field can be obtained than in the structure shown in (b)-(a) in FIG. 41
Since the distance of -2 becomes large, it becomes very difficult to increase the maximum longitudinal magnetic field strength. Therefore, a sufficient cyclotron radius reduction effect could not be obtained.

As described above, conventional scanning electron microscopes are capable of observing semiconductor wafers without cutting them, observing them under a strong longitudinal magnetic field, and observing them at an oblique angle. The problem was that they could not be achieved at the same time. Therefore, as shown in FIG. 7, the wafer cannot be advanced to the next process, reducing efficiency in semiconductor development.

In view of these points, the present invention enables high-resolution observation without cutting the semiconductor wafer, and applies a uniform strong longitudinal magnetic field to any part of a large-sized sample such as a wafer to be observed. Objective lens with possible structure (Fig. 1
) and a tilting mechanism. At the same time, the semiconductor wafer can be tilted to observe deep sub-micron microstructures on any surface with clear images at high resolution without cutting the semiconductor wafer. The purpose is to provide a method to do so.

[0013]

[Means for Solving the Problems] The present invention provides a first magnetic pole 1 that is axially symmetrical, has a hole in the center through which an electron beam passes, and is conical and has a flat tip; It has a conical shape with a flat tip facing the above-mentioned first part.
The second magnetic pole 7 is magnetically connected to the magnetic pole 1 by a rod-shaped magnetic path 7-1, and the rod-shaped magnetic path 7-1 is hollow, and the first magnetic pole 1 and the The sample to be observed 2 is mounted between the magnetic pole 7 of 2 and is movable in a plane perpendicular to the axis, and the sample to be observed 2 can be arbitrarily rotated within the plane and placed in a hollow part. Rotation/tilt/Z that can tilt around the direction of the magnetic path 7-1 and move arbitrarily in the direction of the axis
A moving table 9 equipped with a moving mechanism is provided, and the electron beam passing through the hole of the first magnetic pole 1 is focused and irradiated onto the sample to be observed 2 mounted on the moving table 9. Observe the tilted image of.

[0014]

[Function] With the above-described configuration, the present invention can generate a uniform and strong magnetic field on the surface of the wafer, which is the sample to be observed 2, and at the same time has a short focal length structure. In addition, the sample to be observed (wafer) 2 mounted on the moving table 9 is rotated within the plane.
By providing a mechanism that tilts with the direction of the magnetic path 7-1 as an axis and moves in the Z direction, the sample to be observed 2 can be observed while tilting at any angle.

Therefore, the magnetic poles 1 and 7 constituting the objective lens
A bar-shaped magnetic path 7-1 is connected to one of the magnetic poles 7 by penetrating the hollow part of the movable moving stage 9, and the specimen 2 to be observed is connected with the direction of this magnetic path 7-1 as an axis. Tilt the
By in-plane rotation and Z movement, it is possible to observe the entire surface of a huge sample 2 to be observed, such as a wafer, at any angle and with high resolution under a short focal length. As a result, even on the entire surface of the wafer, it becomes possible to obliquely observe the fine structure with deep unevenness with a clear and high-contrast image. Furthermore, similar effects can be obtained when observing fine structures other than semiconductor wafers.

[0016]

Embodiment Next, the structure and operation of an embodiment of the present invention will be explained in detail using FIGS. 1 to 4. FIG. 1 shows a basic configuration diagram of the present invention. FIG. 1(a) shows the principle configuration diagram, and FIG. 1(b) shows the longitudinal magnetic field strength. Here, in Figure 1 (
As shown in b), the objective lens of the present invention can obtain almost the maximum longitudinal magnetic field strength in the vicinity of the sample to be observed 2, and can generate high secondary electrons from deep holes with concavities and convexities without colliding with the side walls. It becomes possible to take out the electrons toward the secondary electron detector with high efficiency.

In FIG. 1(a), the magnetic pole 1 is an axially symmetrical magnetic pole with a hole in the center and a conical shape with a flat tip, and forms a magnetic field that converges the electron beam. be. The magnetic paths 1-1 and 1-2 are magnetic paths that constitute the objective lens, and are paths for the magnetomotive force generated by passing a current through the coil 4.

Passage 3 is a passage for the electron beam. The coil 4 is excited by passing a current through it. The magnetic lines of force 6 are the lines of force of the magnetic field generated between the magnetic poles 1 and 7, and are schematically shown. The magnetic pole 7 is a conical magnetic pole with a flat tip facing the first magnetic pole 1, and together with the first magnetic pole 1 forms a magnetic field that converges the electron beam. This magnetic pole 7 is magnetically connected to a bar-shaped magnetic path 7-1.

The bar-shaped magnetic path 7-1 connects the second magnetic pole 7 to the first
It has a rod-like shape and magnetically connects the magnetic path 1-2 and the magnetic pole 7. This bar-shaped magnetic path 7-1 is arranged in a hollow part provided through the moving table 9 so as not to come into contact with the moving table 9 during sample movement, and is magnetically connected to the magnetic path 1-2. is connected to. By providing this bar-shaped magnetic path 7-1, as shown in the perspective view of FIG. It becomes possible to move the observed sample 2 to a very large extent. Further, a tilting mechanism is provided with the direction of the rod-shaped magnetic pole 7-1 as a tilting axis (see FIGS. 3 and 4).

The movable table 9 is horizontally movable and is provided parallel to the magnetic poles 1 and 7. The sample to be observed 2 is mounted on the movable table 9 and irradiated with a focused electron beam, the generated secondary electrons are collected and a secondary electron image is displayed. Further, on this moving table 9, there is a rotation mechanism for rotating the observed sample 2 within the plane, a tilting mechanism with the direction of the above-mentioned bar-shaped magnetic path 7-1 as the tilting axis, and a tilting mechanism in the direction of the axis (Z direction). It is equipped with a Z movement mechanism.

The sample stage 23 holds and fixes a wafer, which is the sample 2 to be observed. The sample stage tilting mechanism 5 is
This is a mechanism for tilting the sample stage 23 with the direction of the magnetic path 7-1 as the tilt axis. The sample stage rotation motor 29 is connected to the sample stage 23.
A motor that rotates the motor in a plane, such as an ultrasonic motor or a linear motor.

The sample stage height adjustment motor 34 is connected to the sample stage 2.
3 in the Z direction. this is,
When the sample stage 23 is tilted or rotated, the electron beam 12
The object is moved in the Z direction so that the irradiation position is within the working distance (in-focus range). As described above, the magnetic path 7-1 is arranged in the hollow part of the horizontally movable sample stage 9, and the magnetic pole 7 is connected to this, and
By tilting the sample stage 23 with the direction of the magnetic path 7-1 as the tilt axis, rotating it in the plane, and moving it in the Z direction, the entire surface of the large-sized sample 2 such as a wafer can be observed under a short focal length. It becomes possible to easily observe with high resolution in a tilted state. Furthermore, since both the magnetic poles 1 and 7 are fixed, a constant and uniform magnetic field is always obtained, and disturbances in the magnetic field due to movement of the wafer do not occur. Therefore, observed sample 2
The entire area can be observed stably and with high resolution in a tilted position. Furthermore, by optimizing the shape and size of the magnetic pole 7, such as by making it a truncated cone, a uniform strong longitudinal magnetic field can be generated.

FIG. 6(b) shows how secondary electrons behave when using the objective lens of the present invention. As can be seen by comparing the conventional case with FIG. 6(a), by increasing the longitudinal magnetic field strength Bz, the cyclotron radius becomes smaller.
It is possible to significantly improve the SN reduction caused by collision of secondary electrons with the sidewalls of the fine structure. As a result, it becomes possible to observe the bottom of a deep three-dimensional structure from any direction with high SN and clear high resolution.

The present invention will be specifically explained using FIGS. 2 to 4. Figure 2 is a configuration diagram (front view) of an embodiment of the present invention.
3 is a block diagram (side view) of an embodiment of the present invention, showing the objective lens portion in FIG. 1(a) in detail. FIG. 4 is a perspective view of essential parts according to the present invention. Also,
2 and 3 are views seen from direction A and direction B in FIG. 4.

In FIGS. 2 and 3, an electron gun 11 emits an electron beam. The electron beam 12 is an electron beam emitted from the electron gun 11. Aligning coil 1
3 is for aligning the axis of the electron beam. The converging lens 14 is a magnetic field lens that converges the electron beam. The converging coil 15 applies a magnetomotive force to the converging lens 14 by passing a current through it, thereby generating a lens action.

[0026] The aperture 16 blocks unnecessary electron beams,
This is for irradiating only the significant electron beam 12 onto the wafer 22. The magnetic pole 18 is a magnetic pole that is axially symmetrical, has a hole in the center, and has a conical shape with a flat tip. The magnetic pole 19 is a magnetic pole facing the magnetic pole 18, and is a conical magnetic pole with a flat tip.

The coil 20 is connected to the objective lens 1 by passing a current through it.
7 to generate a lens effect. The bar-shaped magnetic path 21 is related to this embodiment, and is a magnetic path for generating an objective lens magnetic field in the gap between the opposing magnetic poles 18 and 19. It is also shaped like a rod so that it does not come into contact with the hollow part provided in the sample stage 23 (see FIG. 4).

The wafer 22 is a sample to be observed. The sample stand (holding stand) 23 is a stand that holds the wafer 22,
It has a hollow part under the part that holds the wafer 22, and is configured so that the bar-shaped magnetic path 21 is inserted into the hollow part. The sample stage 23 is mounted on a sample stage tilting mechanism 33. By providing a hollow part in this sample stage 23 and arranging the rod-shaped magnetic path 21 inside, the wafer 22 can be moved significantly in the horizontal plane, and the sample stage tilting mechanism 33 can be moved in the direction of this magnetic path 21. Huge size wafer 2 with the tilt axis
2 can be easily tilted in the range of 0° to 90° (or the angle until it contacts the magnetic pole 18) (see β in Figure 4)
. Further, this sample stage 23 can rotate within the plane and move in the Z direction.

The secondary electron detector 24 collects and detects secondary electrons generated by irradiating the electron beam 12 onto the wafer 22. The deflection coil 25
is scanned onto the wafer 22. The magnetic path 26 magnetically connects the bar-shaped magnetic path 21 to the objective lens 17 .

The moving stages 27 and 28 are used to move the sample stage 23 in a plane perpendicular to the axial direction of the objective lens 17 (movement in the X direction and Y direction). The sample stage rotation motor 29 is a motor that rotates the sample stage 23 within a plane, and is, for example, an ultrasonic motor or a linear motor. By rotating using these ultrasonic motors and linear motors,
Stable and highly accurate rotation control is possible. Here, Figure 4
Rotate in the direction of α shown in .

The sample chamber 30 is a vacuum chamber containing the wafer 22 and the like. The fixtures 31, 31', 32, 32' are
This is for fixing the wafer 22 to the sample stage 23. The sample stage tilting mechanism 33 is a mechanism that tilts the sample stage 23 in the β direction shown in FIG. 3 with the direction of the bar-shaped magnetic path 21 as the tilt axis, and is, for example, a mechanism in which circular arcs with a constant curvature are aligned. , or a mechanism that tilts around a tilt axis. To change the angle β, position accuracy (
Uses a motor with high angle accuracy).

The sample stage height adjustment motor 34 is connected to the sample stage 2.
This is a motor that adjusts the position of No. 3 in the Z direction. When the sample stand 23 is rotated by the sample stand rotation motor 23 or when the sample stand 23 is tilted by the sample stand tilting mechanism 33, the working position of the objective lens 17 is The height in the Z direction is adjusted so that it falls within the area (range where focusing is possible). Although the sample stage height adjustment motor 34 is provided at four locations in the figure, it may be provided at three locations. Moreover, although it is provided between the sample stage 23 and the sample stage tilting mechanism 33, it may be provided between the sample stage tilting mechanism 33 and the moving stage 27. In this case, the height adjustment range can be widened.

The secondary electron trajectory 35 represents the trajectory of a certain secondary electron, and represents a spiral trajectory determined by the magnetic field and the initial velocity of the secondary electron. Next, the operation of the configuration shown in FIGS. 2 to 4 will be explained. (1) The electron beam 12 emitted from the electron gun 11 is
The beam is aligned by the alignment coil 13, converged by the converging lens 14, and enters the objective lens 17 via the aperture 16. The electron beam further focused by the objective lens 17 irradiates the wafer 22 and scans this irradiation point by the deflection coil 25, and the secondary electrons emitted from the wafer 22 are detected by the secondary electron detector 24. A so-called secondary electron image is displayed by modulating the brightness on an external display.

(2) By passing a current through the coil 20 constituting the objective lens 17, the generated magnetomotive force is applied to the loop indicated by the dotted line in the figure. Of this loop,
The only magnetic field that effectively acts as the objective lens 17 on the electron beam 12 is the axially symmetrical magnetic field generated between the magnetic poles 18 and 19. The rod-shaped magnetic path 21 is connected to the magnetic pole 19
This is for forming a magnetic loop between the objective lens 17 and the objective lens 17. Further, the wafer 22 to be observed is placed closely on the sample stage 23, and the fixtures 31, 31',
32, 32'. The sample chamber 30 and the electron beam 12 passage are evacuated by a vacuum exhaust system (not shown) so as not to interfere with the movement of the electron beam 12. Further, a wafer transport mechanism for inserting and removing the wafer 22 is provided. magnetic pole 18,
19. The magnetic circuit such as the bar-shaped magnetic path 21 is made of a high magnetic permeability material (for example, pure iron, cobalt iron, permalloy, etc.).

(3) The secondary electrons emitted from the wafer 22 are captured by the magnetic field generated by the magnetic poles 18 and 19, and move upward in the figure while rotating, drawing a spiral trajectory. Positive voltage is applied2
Since the secondary electrons are collected by the secondary electron detector 24, it is possible to make the collection efficiency of the secondary electrons extremely high. When the objective lens 17 having the structure of the present invention is used, a strong axial magnetic field can be generated on the surface of the wafer 22, so that the secondary electron collection efficiency is further improved. Therefore, a bright, high-quality secondary electron image can be displayed. At this time, objective lens 1
The sample stage 23 on the lower side of the sample table 7 is made horizontally movable (in the X and Y directions), and the wafer 22, which is the sample to be observed, is placed between the magnetic poles 18 and 19 of the objective lens 17 under a short focal length. 2
By collecting secondary electrons and displaying a secondary electron image,
It becomes possible to easily observe the entire surface of the gigantic wafer 22 with high resolution.

As described above, if it becomes possible to observe the fine structure with deep unevenness of a gigantic sample such as the wafer 22, there will be no need to cut the wafer 22, and a great effect will be obtained in the semiconductor manufacturing process. As shown in FIG. 7, after SEM observation of a wafer during the semiconductor manufacturing process, it can be returned to the next process, thereby significantly improving throughput and yield in the semiconductor manufacturing process. As a result, development efficiency in semiconductor manufacturing is greatly improved.

(4) Next, the operation when observing the wafer 22 while tilting it will be explained. When observing an arbitrary observation point on the wafer 22 at an angle, the sample stage rotation motor 2
9 rotates the sample stage 23 in the α direction, and the sample stage tilting mechanism 33 tilts it in the β direction, and when this arbitrary observation point is about to go out of the observation field, it is rotated in the X direction and The wafer 22 is observed by repeatedly moving it in the Y direction and returning it to the observation field, tilting it by a desired angle. At this time, if the observation point is about to go out of the working area, the sample stage height adjustment motor 34 moves it in the Z direction to return it to the working area. In this way, rotate α, tilt β, and further move Z, X, and Y as necessary (5-axis control),
It becomes possible to observe a desired observation point on the wafer 22 fixed to the sample stage 23 while tilting it at a desired angle.

[0038]

[Effects of the Invention] As explained above, according to the present invention,
The lower magnetic pole of the magnetic poles constituting the objective lens is magnetically connected via the hollow part of the movable sample stage by a bar-shaped magnetic path, and the sample to be observed is placed between the magnetic poles of the objective lens. A sample table tilting mechanism with the direction of this magnetic path as the tilt axis (tilt in the β direction), a rotation mechanism in the plane of the sample table (α
(rotation in the direction) and a Z movement mechanism (movement in the Z direction) for the sample stage. (1) The sample to be observed can be tilted and observed with high resolution under a strong magnetic field.

(2) Since the sample to be observed can be observed by tilting it, the side and bottom parts of an aspect ratio structure such as a trench can be observed with high resolution. (3) Lens aberrations can be reduced by using a short focal length. (4) Since the magnetic poles are fixedly arranged, a uniform and uniform magnetic field can be easily generated.

(5) Even if the sample to be observed is as large as a semiconductor wafer, the magnetic path does not become huge, and a uniform strong magnetic field can be efficiently generated. (6) Since the sample to be observed is in a uniform strong magnetic field, the generated secondary electrons can be detected with high efficiency. (7) Since the collection efficiency of secondary electrons is dramatically improved, a high-quality secondary electron image can be obtained even if the amount of primary electron beam is reduced. Image deterioration due to charging can be prevented.

(8) Since the secondary electron collection efficiency is high, it is possible to easily observe a bright, high-quality, high-resolution secondary electron image even if the surface of the sample to be observed has deep irregularities. (9) High-resolution observation is possible without cutting the semiconductor wafer. As a result of the above effects, it becomes possible to easily obliquely observe a high-resolution, bright, high-quality secondary electron image of a huge sample such as a wafer at a short focal length. As a result, microstructures such as trench grooves (width: 0.2 to 0.7 μm, depth: 3 to 5 μm) with an aspect ratio exceeding 5 and contact holes can be formed from the surface to the bottom.
By tilting it further, it is possible to observe the sides with clear images at high resolution.

Furthermore, since high-resolution observation is possible without cutting the wafer, it is possible to observe the wafer in the middle of the manufacturing process using the scanning electron microscope of the present invention, and then continue manufacturing from the next process. This greatly improves throughput in the semiconductor manufacturing process and its development stage. Therefore, it can be said that the effect of the present invention on the semiconductor manufacturing industry is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention.

FIG. 2 is a block diagram (front view) of an embodiment of the present invention, showing the objective lens portion of FIG. 1 in detail.

FIG. 3 is a configuration diagram (side view) of an embodiment of the present invention, showing the objective lens portion of FIG. 1 in detail.

FIG. 4 is a perspective view of essential parts according to the present invention.

FIG. 5 is an explanatory diagram of the prior art.

FIG. 6 is an explanatory diagram of differences in the behavior of secondary electrons depending on the strength of the longitudinal magnetic field.

FIG. 7 is a SEM observation sequence diagram in a semiconductor manufacturing process.

[Explanation of symbols]

1, 7, 18, 19: magnetic pole 1-1, 1-2, 26: Magnetic path 7-1, 21: Bar-shaped magnetic path 2: Observed sample (wafer) 4, 20: Coil 9, 27, 28: Moving platform 11: Electron gun 12: Electron beam 13: Axis alignment coil 14: Convergent lens 16: Aperture 17: Objective lens 22: Wafer 23: Sample stand 24: Secondary electron detector 25: Deflection coil 29: Sample stage rotation motor 31, 31', 32, 32': Fixtures 33: Sample stage tilting mechanism 34: Sample stage height adjustment motor α: Rotation angle of sample stage β: Inclination angle of sample stage Z: Z movement distance of sample stage

Claims (4)

[Claims] Claim 1: In a scanning electron microscope in which an electron beam focused by an objective lens is irradiated onto a sample to be observed and an image thereof is observed, the microscope has an axially symmetrical hole through which the electron beam passes through the center, and has a conical shape. a first magnetic pole (1) with a flat tip; and a conical magnetic pole (1) opposite to the first magnetic pole (1) with a flat tip;
The second
The first magnetic pole (1) and the second magnetic pole (7) have a hollow portion penetrating the rod-shaped magnetic path (7-1).
A specimen to be observed (2) is mounted between the magnetic pole (7) of the specimen, and is movable in a plane perpendicular to the axis, and
2) can be rotated arbitrarily in the plane, tilted with the direction of the magnetic path (7-1) arranged in the hollow part as the tilt axis, and a rotation/tilt/Z movement mechanism that can be moved arbitrarily in the direction of the axis. a moving table (9) mounted thereon, the electron beam passing through the hole of the first magnetic pole (1) is focused and irradiated onto the sample to be observed (2) mounted on the moving table (9); The sample to be observed (2)
A scanning electron microscope characterized in that it is configured to observe a tilted image of. 2. In claim 1, the secondary electrons emitted from the observed sample (2) are transferred to the first magnetic pole (1).
What is claimed is: 1. A scanning electron microscope characterized in that the scanning electron microscope is configured to detect the hole with a secondary electron detector provided at a position upside down and display a secondary electron image. 3. A scanning electron microscope according to claim 1, characterized in that the sample to be observed is rotated by an ultrasonic motor or a linear motor. 4. An axially symmetrical hole through which the electron beam passes through the center when observing a semiconductor wafer using a scanning electron microscope that irradiates the sample to be observed with an electron beam focused by an objective lens and observes its image. a first magnetic pole (1) having a conical shape and a flat tip; and a first magnetic pole opposite to this first magnetic pole (1) having a conical shape and a flat tip; It has a second magnetic pole (7) magnetically connected to (1) by a bar-shaped magnetic path (7-1), and a hollow part that penetrates this bar-shaped magnetic path (7-1). , and a sample to be observed (2) is mounted between the first magnetic pole (1) and the second magnetic pole (7), and is movable in a plane perpendicular to the axis; A moving table (9) equipped with a rotation/tilting mechanism that rotates the sample (2) arbitrarily within the plane and tilts the sample (2) around the direction of the magnetic path (7-1) placed in the hollow part.
), the electron beam passing through the hole of the first magnetic pole (1) is focused and irradiated onto the observed sample (2) mounted on the movable table (9), and 1. A method for observing a semiconductor wafer, the method comprising observing a fine structure on a semiconductor wafer by tilting the semiconductor wafer without cutting the semiconductor wafer using a scanning electron microscope configured to observe an image of the semiconductor wafer.