JPH09134696A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of an image quality of a secondary electron image, and prevent the degradation of sensitivity of an X-ray detector when a sample holder to heat a sample at a high temperature is provided. SOLUTION: A light shielding plate 13 to shield the emitted light generated from a heating member 11 and a sample is arranged between a sample holder 14 having the heating member 11, a secondary electron detector 9 and an X-ray detector. A primary electron beam 4 is irradiated to the sample through a small hole 22 of the light shielding plate, and a secondary electron 10 generated from the sample is rolled upward by a magnetic field of an objective lens 8, and is detected by the secondary electron detector 9. On the other hand, since the emitted light 12 generated from the heating member 11 or the sample is not made incident on the secondary electron detector 9 and the X-ray detector by being shielded by the light shielding plate 13, the degradation of a secondary electron image and the degradation of sensitivity of the X-ray detector can be prevented.

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, and more particularly to a scanning electron microscope which enables observation of a secondary electron image while holding a sample at a high temperature and a sample holder used for the scanning electron microscope.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional scanning electron microscope for observing a secondary electron image of a high temperature sample. Electrons are emitted from the tip of the filament 1 arranged in a high vacuum by the electric field of the extraction electrode 2 to which a high voltage is applied.
The emitted electrons are accelerated by the acceleration electrode 3 to form the primary electron beam 4. The primary electron beam 4 is narrowed down by the first condenser lens 5 and the second condenser lens 6, then two-dimensionally scanned and deflected by the deflection coil 7, and focused by the objective lens 8 on the sample supported on the heating member 11. It Secondary electrons 10 generated by irradiating the sample and the heating member 11 supporting the sample with the primary electron beam 4 are wound up by the magnetic field of the objective lens 8 and then detected by the secondary electron detector 9 to form an image. To be done.

The sample and the heating member 11 are, if necessary,
It is heated by a heating power supply 15 connected to the sample holder 14. As the sample holder 14, JP-A-6-449 is used.
Japanese Patent No. 36 discloses a structure in which a heating power source and wiring are incorporated.

[0004]

A heating member of a sample holder incorporated in a scanning electron microscope is energized to heat the sample to a temperature of several hundreds to several thousands, and a secondary electron image of the sample is observed in a high temperature state. Then, striped noise is mixed into the image to deteriorate the image quality, and in the worst case, the entire image may be hidden by the noise and unobservable. Further, in a scanning electron microscope observing a high temperature sample, the X
It was found that the sensitivity of the line detector deteriorates quickly.

The present invention has been made in view of the above problems, and an object thereof is to provide a scanning electron microscope capable of obtaining a high-quality secondary electron image even when a sample is in a high temperature state. And Another object of the present invention is to suppress sensitivity deterioration of an X-ray detector attached to a scanning electron microscope for observing a high temperature sample.

[0006]

[Means for Solving the Problems] As a result of investigating the cause of deterioration of the image quality of the secondary electron image of the sample in the high temperature state, the radiated light from the incandescent sample or the heating member is detected as the secondary electron together with the secondary electron. It was found that the incident was on the vessel. The secondary electron detector 9 shown in FIG. 9 has a structure in which a scintillator and a photomultiplier tube are coupled by a light guide, and guides the light emitted from the scintillator by the incidence of secondary electrons to the photomultiplier tube by the light guide. To detect. By the way, radiated light is emitted in all directions from the incandescent sample and the heating member 11. When the radiated light 12 is incident on the secondary electron detector, it passes through the scintillator and reaches the photomultiplier tube, which causes noise. It produces a signal. The emitted light is not limited to direct light from the sample and the heating member 11 as shown in FIG.
The reflected light 20 reflected by the inner wall of the sample holder 14 also enters the secondary electron detector 9 and deteriorates the image quality.

It has also been found that this emitted light is incident on the X-ray detector arranged inside the lens barrel of the scanning electron microscope and causes the sensitivity deterioration of the X-ray detector to be accelerated. FIG.
FIG. 1 is a configuration diagram in the vicinity of an objective lens of a conventional scanning electron microscope equipped with an X-ray detector. The X-ray 17 generated from the sample by irradiating the sample supported on the heating member 11 of the sample holder 14 with the primary electron beam 4 is the objective lens 8
The X-ray detector 1 passing through the collimator 16 installed above
8 to be detected. At this time, the heated sample and the radiation 12 generated from the heating member 11 are incident on the X-ray detector 18, so that the sensitivity of the X-ray detector 18 is deteriorated.

The present invention is based on this recognition of the problem and the cause of the conventional scanning electron microscope for observing a high-temperature sample, and the emitted light emitted from the sample or the heating member is used as a secondary electron detector or a secondary electron detector. The object is achieved by taking measures to prevent the light from entering the X-ray detector. That is, the present invention is a sample holder in a scanning electron microscope including a sample holder having a heating member for heating a sample, and a secondary electron detector for detecting secondary electrons generated from the sample by primary electron beam irradiation. And a secondary electron detector, a light shielding plate for preventing radiated light generated from the heating member or the sample from reaching the secondary electron detector.

The light shielding plate blocks the path of the light that travels straight from the heating member or the sample toward the secondary electron detector. on the other hand,
The secondary electrons generated from the sample are rolled up (vertically) by the magnetic field of the objective lens, and most of them pass through the small holes provided in the light shielding plate, and due to the bias electric field applied to the secondary electron detector. It is captured by the secondary electron detector. As a result, light incidence on the secondary electron detector is minimized,
It is possible to prevent image quality deterioration of the secondary electron image.

In the case of normal observation in which the sample is not heated, by moving the shading plate to the standby position, a small amount of secondary electrons cut by the shading plate have passed through the small holes of the shading plate. Similar to the secondary electrons of the part, they reach the secondary electron detector and are detected, and the S / N of the image is improved. By removing the light shielding plate from the optical axis, it is possible to secure a wide observation field during low magnification observation.

The present invention also provides a sample holder having a heating member for heating the sample, a secondary electron detector for detecting secondary electrons generated from the sample by the primary electron beam irradiation, and a secondary electron detector by the primary electron beam irradiation. In a scanning electron microscope including an X-ray detector for detecting X-rays generated from a sample, radiation emitted from the heating member or the sample is generated between the sample holder and the secondary electron detector and the X-ray detector. It is characterized in that a light-shielding plate is arranged to prevent reaching the secondary electron detector and the X-ray detector.

In the scanning electron microscope equipped with the X-ray detector for detecting the X-rays generated from the sample, the light shielding plate prevents direct light and reflected light from entering the X-ray detector. In the case of a scanning electron microscope equipped with an X-ray detector, since X-rays generated from a sample travel straight in the same manner as light, it is impossible to perform X-ray analysis while preventing the incidence of light. For this reason, X-ray analysis is performed while avoiding high temperature observation. But X
X by high temperature observation regardless of whether line analysis is performed or not
Since the incidence of light on the line detector deteriorates the sensitivity of the X-ray detector, it is necessary to shield the light to prevent the deterioration of sensitivity.
According to the present invention, light (and X-rays) is prevented from reaching the X-ray detector, and sensitivity deterioration is prevented. Further, by making the shield plate movable, X-ray analysis becomes possible in the case of normal observation in which the sample is not heated.

It is preferable that the light shielding plate has a small hole for passing the primary electron beam and the secondary electron, and is movable between a light shielding position where the small hole is located on the optical axis and a retracted position. The light shield is
Allows the primary electron beam to irradiate the sample and the passage of secondary electrons generated from the sample through the small holes when it is in the light-shielded position, and prevents the radiated light from entering the secondary electron detector and X-ray detector. To do. In the retracted position, the shading plate is far away from the secondary electron detection path and the X-ray detection optical path, thereby enabling more efficient secondary electron detection or X-ray detection.

Further, the sample holder may be provided with a light shielding plate having holes for passing the primary electron beam with which the sample is irradiated and the secondary electrons generated from the sample.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to examples. FIG. 1 is a block diagram of a scanning electron microscope and a sample heating apparatus according to an embodiment of the present invention. Electrons are emitted from the tip of the filament 1 arranged in a high vacuum by the electric field of the extraction electrode 2 to which a high voltage is applied. The emitted electrons are accelerated by the acceleration electrode 3 to form the primary electron beam 4. The primary electron beam 4 is narrowed down by the first condenser lens 5 and the second condenser lens 6, two-dimensionally scanned and deflected by the deflection coil 7, passes through the small hole 22 provided in the light shielding plate 13, and then the objective lens 8 Thus, the sample supported on the heating member 11 of the sample holder 14, for example, the powder sample adhered to the heating member 11 is focused. As shown in the perspective view of FIG. 2, the light shielding plate is a thin metal plate such as aluminum, copper, or brass, which has a small hole 22 with a diameter of about 2 mm.
The small hole 22 is adjusted by the light shielding plate position adjusting knob 21 provided outside the sample chamber so that the small hole 22 is located on the optical axis. The heating member 11 is made of tungsten,
It is a high melting point conductive material such as platinum, and is made to have a small heat capacity in order to improve thermal efficiency. Most of the secondary electrons 10 generated by the irradiation of the sample and the heating member 11 supporting the sample with the primary electron beam 4 are wound up by the magnetic field of the objective lens 8 and pass through the small holes 22 of the light shielding plate 13. An image is formed by being detected by the secondary electron detector 9.

The sample and heating member 11 are heated by a heating power source 15 connected to the sample holder 14 as needed. At this time, the radiated light 12 generated from the heating member 11 and the sample is blocked by the light blocking plate 13, so that it does not enter the secondary electron detector 9 and deteriorate the image quality. In the case of normal observation in which the sample is not heated, the light-shielding plate 13 is not necessary, and therefore the light-shielding plate position adjusting knob 21 moves it to the standby position. As a result, even a small amount of secondary electrons cut by the light shield plate 13 reach the secondary electron detector 9 and are detected like most of the secondary electrons that have passed through the small holes 22 of the light shield plate 13. Therefore, the S / N of the image is improved.

FIG. 3 shows an embodiment of a scanning electron microscope equipped with an X-ray analyzer. FIG. 3 is an enlarged cross-sectional view near the objective lens. A sample and an X-ray detector 18 are placed on the objective lens 8.
The collimator 16 that defines the optical path between the two is fixed.
A small hole 22 is provided between the sample holder 14 and the collimator 16.
The light-shielding plate 13 having is arranged. By operating the light shielding plate position adjusting knob 21, the small hole 22 of the light shielding plate 13
Are adjusted so as to be located on the optical axis, and the primary electron beam 4 and the secondary electrons 10 generated from the sample can pass through the small hole 22. On the other hand, the radiated light 12 generated from the heating member 11 and the sample by heating is shielded by the light shielding plate 13 and does not enter the secondary electron detector 9 and the X-ray detector 18. Therefore, it is possible to prevent light from entering the X-ray detector 18 during observation of a high-temperature sample and degrading the sensitivity of the X-ray detector.

The shading plate 13 is movable, and in the case of normal observation in which the sample is not heated, as shown in FIG. 4, the shading plate 13 is moved to a retracted position that does not interfere with X-ray detection.
Therefore, the X-rays 17 generated from the sample by irradiating the sample supported on the heating member 11 with the primary electron beam 4
Passes through the collimator 16 installed on the objective lens 8 and is detected by the X-ray detector 18.

The light shielding plate 13 blocks the optical path connecting the sample holder 14 and the secondary electron detector and the X-ray detector, so that the radiation from the heating member 11 or the sample is detected by the secondary electron detector and the X-ray detector.
Prevents incident on line detector. However, it is also conceivable that the emitted light is reflected by the inner surface or the edge of the small hole 22 provided in the light shielding plate 13 and enters the secondary electron detector or the X-ray detector. In order to prevent the generation of such reflected light, as shown in the enlarged view of FIG. 5, a thin film 19 of carbon or the like having a low light reflectance is formed on the inner surface of the small hole 22 of the light shielding plate 13 and the edge of the small hole. It is preferably applied. It is more effective to provide this thin film having a low reflectance also in the electron beam passage and the X-ray passage of the collimator 16.

FIG. 6 is a sectional view of an embodiment in which a light shielding plate is incorporated in a sample holder. In this embodiment, a light shielding plate 26, which is a thin metal plate made of aluminum, copper, brass or the like and provided with a small hole 27 having a diameter of about 0.3 mm, is attached to the upper surface of the sample holder 14. The light shielding plate 26 may be fixed to the sample holder 14 or may be detachable. When the shading plate is fixed, the heating member 11 and the sample are attached to the sample holder 14 from the opening opposite to the shading plate. Heating element 1
Irradiation of the primary electron beam 4 onto the sample held at
Most of the secondary electrons 10 generated from the sample through the small holes 27 of 6 are rolled up by the magnetic field of the objective lens 8 and pass through the small holes 27 of the light shielding plate 26 in the opposite direction, and the secondary electrons are generated. An image is formed by being detected by the detector 9. At this time,
The radiated light 12 generated from the heating member 11 and the sample held therein by the heating is blocked by the light blocking plate 26, so that it does not enter the secondary electron detector 9 and deteriorate the image quality. Since the light shield plate 26 also blocks the optical path connecting the heating member 11 and the X-ray detector 18, it is possible to prevent the X-ray detector 18 from degrading the sensitivity due to the incident radiation light.

FIG. 7 is a perspective view of a sample holder according to another embodiment of the present invention. In this embodiment, a thin film 19 of carbon or the like having a low light reflectance is provided on the inner wall of the sample holder 14.
Is applied to prevent the generation of scattered light due to the radiation 12 generated from the heating member 11 and the sample due to heating being reflected by the inner wall of the sample holder 14. By using the sample holder of the present embodiment together with, for example, the scanning electron microscope equipped with the light shielding plate 13 shown in FIG. 1, it is possible to more effectively prevent light from entering the secondary electron detector 9. Becomes Further, even if the light shielding plate 26 having the small holes is attached to the upper portion of the sample holder 14 of FIG. 7 in which a thin film having a low light reflectance is applied to the inner wall, the light incident on the detector can be effectively performed. Can be prevented.

FIG. 8 is a diagram showing the relationship between the sample temperature and the signal amount of the secondary electron detector. The horizontal axis represents the sample temperature, and the vertical axis represents the signal amount (relative value) of the secondary electron detector. In the figure, a represents a measured value by a conventional scanning electron microscope (FIG. 9) that does not use a light shield, and b represents a scan using a sample holder in which a thin film of carbon is applied to the inner wall and a light shield is attached to the upper part. It represents the measured value by an electron microscope. The measurement was performed under constant conditions other than the sample temperature. In FIG. 8, the fact that the signal amount of the secondary electron detector increases as the sample temperature rises indicates that the intensity of the radiated light incident on the secondary electron detector increases due to the temperature rise. When the signal amount of the secondary electron detector exceeded 1.0, image observation became impossible.

As shown in FIG. 8, in a conventional scanning electron microscope which does not take measures against radiated light, when the sample temperature exceeds 1300 ° C., image observation becomes impossible due to noise. However, according to the scanning electron microscope of the present invention in which the emitted light incident on the secondary electron detector is reduced as much as possible, the image observation is possible even if the sample is heated up to about 1600 ° C.

[0024]

According to the present invention, it is possible to observe a secondary electron image in a state where the sample is kept at a high temperature without deterioration of image quality due to light incident on the secondary electron detector. Further, it becomes possible to prevent the sensitivity deterioration of the X-ray detector due to the high temperature observation.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a scanning electron microscope.

FIG. 2 is a perspective view of a light shielding plate.

FIG. 3 is a sectional view in the vicinity of an objective lens of an example of a scanning electron microscope equipped with an X-ray analysis device.

FIG. 4 is an explanatory diagram of an arrangement during normal observation in which a sample is not heated.

FIG. 5 is an enlarged view of a sample holder and a light shielding plate.

FIG. 6 is an explanatory diagram of an embodiment in which a light shielding plate is attached to the sample holder.

FIG. 7 is a perspective view of a sample holder.

FIG. 8 is a diagram showing a relationship between a sample temperature and a signal amount of a secondary electron detector.

FIG. 9 is a block diagram of a conventional scanning electron microscope.

FIG. 10 is a perspective view of a conventional sample holder.

FIG. 11 is a cross-sectional view in the vicinity of an objective lens of a conventional scanning electron microscope equipped with an X-ray analyzer.

[Explanation of symbols]

1 ... Filament, 2 ... Extraction electrode, 3 ... Accelerating electrode, 4 ...
Primary electron beam, 5 ... First condenser lens, 6 ... Second condenser lens, 7 ... Deflection coil, 8 ... Objective lens, 9 ...
Secondary electron detector, 10 ... Secondary electron, 11 ... Heating member, 1
2 ... Synchrotron light, 13 ... Slit, 14 ... Sample holder, 1
5 ... Heating power supply, 16 ... Collimator, 17 ... X-ray, 18 ...
X-ray detector, 19 ... Low reflectance thin film, 20 ... Reflected light, 21
... Slit position adjustment knob, 22 ... Small hole, 26 ... Light shielding plate, 27 ... Small hole

Claims (4)

[Claims] 1. A scanning electron microscope comprising a sample holder having a heating member for heating a sample, and a secondary electron detector for detecting secondary electrons generated from the sample by irradiation with a primary electron beam. And a secondary electron detector, and a light shielding plate for preventing radiated light generated from the heating member or the sample from reaching the secondary electron detector. 2. A sample holder having a heating member for heating the sample, a secondary electron detector for detecting secondary electrons generated from the sample by the primary electron beam irradiation, and a secondary electron detector generated by the primary electron beam irradiation. X for detecting X-rays
In a scanning electron microscope including a line detector, radiant light generated from the heating member or the sample between the sample holder and the secondary electron detector and the X-ray detector detects the secondary electron detector and the X-ray. A scanning electron microscope characterized in that a light-shielding plate is arranged to prevent it from reaching the vessel. 3. The light shielding plate has a small hole for passing a primary electron beam and a secondary electron, and is movable between a light shielding position where the small hole is located on the optical axis and a retracted position. The scanning electron microscope according to claim 1 or 2. 4. A sample holder having a heating member for holding and heating a sample, the upper part of which is provided with a light-shielding plate having a small hole for passing a primary electron beam applied to the sample and a secondary electron generated from the sample. A sample holder characterized in that