JP2006302548A - Scanning electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning electron microscope in which testpiece charging with electricity when observing a non-conductivity testpiece by the scanning electron microscope is prevented by removing scattered floating electrons between the testpiece and an objective lens. <P>SOLUTION: A scattered floating electron ejection mechanism configured with an electrically conductive plate 23 having a through hole through which an electron beam passes and electrodes 21a and 21b insulated from the electrically conductive plate 23 is prepared between the testpiece and the objective lens. By applying negative potential to the electrode 21a and positive potential to the electrode 21b, electric field in a direction perpendicular to an optical axis of the electron beam EB is generated. The floating electrons are ejected to a position apart from the testpiece by the generated electric field as shown by electron ejection orbits DE, and thereby testpiece surface charging with electricity is prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for preventing charging of a sample in a scanning electron microscope (hereinafter abbreviated as SEM) that performs image observation and analysis by irradiating the surface of the sample with an electron beam.

  SEM irradiates a sample surface while scanning a finely focused electron beam two-dimensionally, detects secondary electrons and reflected electrons generated from the sample with the irradiation of the electron beam, and detects the detected signal as an electron beam. The surface of the sample is observed by displaying it as an image in synchronization with the scanning.

  FIG. 1 shows a schematic configuration example of a conventional SEM. In FIG. 1, a mirror 100 represents a cross section of a surface including an electron beam optical axis of an SEM mirror, and the focusing lens 2, the scanning coil 3, and the objective lens 4 are provided so as to be substantially annular. However, the objective lens 4 shows a state in which a hole for inserting the secondary electron detector 6 in the magnetic pole piece and a hole symmetrical to the hole are formed, and the objective lens 4 is not separated vertically. The electron beam EB radiated from the electron gun 1 disposed in the mirror body 100 is finely focused by the focusing lens 2 and the objective lens 4 and irradiated onto the sample 5 attached to the sample stage 7. The acceleration power supply 9 supplies a voltage necessary for accelerating the electron beam EB to the electron gun 1. The focusing lens 2, the objective lens 4, and the scanning coil 3 are supplied with electric power necessary for exciting the coils from the driving unit 10.

  The sample stage 7 is placed on the sample stage 8, and the sample stage controller can horizontally move the X and Y axes, move the height of the Z axis, rotate, and tilt. The control arithmetic processing unit 13 performs control of the acceleration voltage, various lenses and scanning coils, a sample stage, etc., processing of detection signals of secondary electrons, and the like. The operator can operate the operation unit 15 to set observation conditions such as a secondary electron image, display conditions, etc. to desired conditions, or to perform an operation of selecting an observation area on the sample 5.

  The secondary electrons emitted from the sample surface by the electron beam irradiation are rolled up by the magnetic field of the objective lens along the optical axis of the electron beam EB, and, for example, detect secondary electrons along the secondary electron trajectory SE shown in FIG. It is guided to the detector 6 and detected. Since the electron beam EB is scanned two-dimensionally by the scanning coil 3, the secondary electron detection signal detected in synchronization therewith is sent to the display device 14 via the image signal processing unit 11 and the bus 16. And displayed as a secondary electron image. The scattered floating electron orbit FE will be described later.

  The electron beam EB irradiated to the sample 5 is divided into electrons emitted outside the sample as secondary electrons and reflected electrons, and electrons absorbed by the sample. When the sample 5 is conductive, the electrons absorbed by the sample 5 flow to the ground through the sample stage 7 supporting the sample 5. However, when the sample 5 is non-conductive, the region irradiated with the electron beam on the sample surface is charged.

  When the surface of the sample is charged, the observation image is affected variously by the influence. For example, it causes troubles such as extreme contrast of brightness and darkness, drift of observation field of view, and astigmatism increase, and high-resolution image observation cannot be performed. In order to prevent this charging, many techniques are conventionally known.

  For example, charging can be prevented by coating the surface of a non-conductive sample with a thin conductive material such as gold. However, there are also problems such as the possibility of causing surface artifacts, troublesome sample preparation, and inability to restore the original. In particular, when performing high-resolution image observation, there is a basic problem that the fine surface structure is deformed by the coating, and it cannot be determined whether the correct surface shape is observed.

  There is also a method of preventing or reducing electrification by selecting observation conditions. It is known that when the acceleration voltage of an electron beam applied to a sample is lowered, the ratio of secondary electrons emitted from the sample to incident electrons increases. It is also well known that when the sample is tilted to reduce the angle at which the electron beam is incident on the sample surface, the ratio of secondary electrons emitted from the sample to the incident electrons increases. Therefore, when observing a non-conductive sample having a particularly high insulation resistance, a method of preventing charging by combining a low acceleration voltage and a sample tilt observation condition is effective.

  Other methods for reducing charging depending on the observation conditions include a method in which the scanning speed of the electron beam is increased to reduce the number of electrons remaining on the sample surface that cause charging, and the energy of electrons emitted from the sample is selected and charged. A method of forming an image with only electrons that are not affected by the influence of the charging, and forming an image so as not to be affected by charging by increasing the energy when the sample is biased to generate secondary electrons from the sample. There are methods.

Japanese Patent Laid-Open No. 4-363849 JP 11-154479 A JP 2003-151479 A

  None of the methods described in the background art described above is a method of selecting a condition for preventing charging or reducing the charging phenomenon. However, it actively removes excess electrons that cause charging of the sample. is not. Therefore, when a magnetic field or the like is present on the sample, secondary electrons emitted from the sample by electron beam irradiation may float near the surface of the sample and return to the sample because of low energy. The scattered floating electron trajectory FE in FIG. 1 shows such behavior of electrons as an example. Furthermore, the secondary electrons emitted when the reflected electrons hit the lower surface of the objective lens etc. may float and re-fly to the sample surface. This phenomenon becomes more prominent as the hole diameter of the electron beam passage hole below the objective lens is smaller. Electrons floating between the objective lens and the sample fly to places other than the region directly irradiated by the primary electron beam, and the charge is further increased when the sample is non-conductive.

  On the other hand, there is also known a conventional technique that positively eliminates charging. For example, Japanese Patent Laid-Open No. 4-363849 of Patent Document 1 discloses a technique for neutralizing charging by providing a gas ejection device and a gas suction device for injecting ion gas in the vicinity of a sample surface. However, adjustment of the gas flow rate according to the degree of charging requires skill, and there is a problem that the electron source is damaged when the vacuum is lowered by injecting the gas into the vacuum.

  Japanese Patent Application Laid-Open No. 11-154479 of Patent Document 2 discloses a method for inducing a conductive layer by irradiating a sample surface with a positive ion beam to release charged charges. However, it is not easy to match the irradiation amount of the ion beam used for charge removal with the charge amount, and there is a problem that control of the irradiation amount requires experience of an operator.

  Japanese Patent Laid-Open No. 2003-151479 of Patent Document 3 discloses that a probe-like charge neutralizing electrode is placed near or in contact with a charged region of a sample to generate a current between the charged region. A technique for performing charge neutralization control is disclosed. However, since the gap between the objective lens and the sample is narrow in the SEM aiming at high resolution observation, it is not easy to control the probe-like electrode in the vicinity of the charged region. In the first place, the scattered stray electrons widely distributed between the objective lens and the sample cannot be excluded.

  The present invention is for solving the above-described problems, and the object thereof is to efficiently discharge scattered floating electrons distributed between the objective lens and the sample by a simple operation without requiring a complicated mechanism. This is to prevent charging of the non-conductive sample.

In order to solve the above problems, the present invention provides:
An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. The present invention is characterized in that a scattering stray electron discharge mechanism composed of an electrode that can be formed is provided.

  The present invention is also characterized in that a coating layer made of a substance having a lower secondary electron generation efficiency than the conductive plate material is formed on the surface of the conductive plate material facing the sample.

  Further, the invention is characterized in that a coating layer made of a material having a lower secondary electron generation efficiency than the conductive plate material is formed of a material containing carbon as a main component.

  Further, the present invention is characterized in that the conductive plate material is formed of a substance containing carbon as a main component.

  The present invention is also characterized in that at least the surface of the conductive plate facing the sample is kept at the ground potential.

  Further, the present invention is characterized in that a retracting mechanism for retracting the scattered floating electron discharge mechanism from the electron beam path is provided.

  The present invention further includes an adjustment mechanism that moves the conductive plate in a direction perpendicular to the optical axis of the electron beam to align a through hole through which the electron beam is provided in the conductive plate. Features.

  The present invention is also characterized in that a deflector for correcting an axial misalignment of the electron beam by an electric field perpendicular to the optical axis of the electron beam formed by the electrode is provided above the objective lens. .

  The present invention is also characterized in that a discharge electron detector for detecting stray electrons discharged by the scattered stray electron discharge mechanism is provided.

The present invention also provides an objective lens for narrowing an electron beam to irradiate the sample, scanning means for scanning the electron beam irradiation position on the sample, and electrons generated from the sample by electron beam irradiation. In a scanning electron microscope comprising a detecting means for detecting, and a display means for displaying a detection signal from the detecting means as an image in synchronization with the scanning means,
Scattering composed of a conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and a magnetic pole disposed on the conductive plate and capable of selecting an S pole and an N pole A floating electron discharge mechanism is provided.

The present invention also provides
An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. Equipped with a scattered floating electron emission mechanism composed of electrodes
Scattered stray electrons generated in the space between the sample and the objective lens due to electron beam irradiation on the sample are formed in a plane direction perpendicular to the optical axis of the electron beam by the electrode configured in the scattered stray electron discharge mechanism. The electric field is discharged out of the space between the sample and the objective lens to prevent the sample from being charged.

According to the first invention,
An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. Because it has a scattering stray electron emission mechanism composed of electrodes that can
Scattered stray electrons generated in the space between the sample and the objective lens due to electron beam irradiation on the sample are formed in a plane direction perpendicular to the optical axis of the electron beam by the electrode configured in the scattered stray electron discharge mechanism. By the applied electric field, the sample can be discharged out of the space between the sample and the objective lens, and charging of the sample can be prevented.

  According to the second aspect of the invention, since the coating layer made of a substance having a lower secondary electron generation efficiency than the conductive plate is formed on the surface of the conductive plate facing the sample, the reflection generated from the sample Secondary electrons that are generated indirectly when the electrons collide with the lower surface of the conductive plate can be reduced, and charging can be prevented.

  According to the third invention, since the coating layer made of a material having a secondary electron generation efficiency lower than that of the conductive plate material is formed of a material containing carbon as a main component, reflected electrons generated from a sample are Secondary electrons generated by collision with the lower surface of the conductive plate material can be reduced and charging can be prevented.

  According to the fourth aspect of the invention, since the conductive plate is made of a material whose main component is carbon, the reflected electrons generated from the sample collide with the lower surface of the conductive plate and are indirectly generated. Secondary electrons can be reduced and charging can be prevented.

  According to the fifth invention, since at least the surface of the conductive plate facing the sample is maintained at the ground potential, the secondary electrons generated from the sample collide with the lower surface of the conductive plate and the conductive The conductive plate material can be prevented from being charged by being absorbed by the plate material and flowing to the ground.

  According to the sixth aspect of the present invention, a retracting mechanism for retracting the scattered floating electron discharge mechanism from the electron beam path is provided. Therefore, when it is not necessary to use the scattered floating electron discharge mechanism, the scattered floating electron discharge mechanism is retracted from the electron beam path. The operability can be improved.

According to the seventh invention, the conductive plate is moved in a direction perpendicular to the optical axis of the electron beam,
Since the adjustment mechanism for aligning the through hole through which the electron beam passes provided in the conductive plate material is provided, the normal secondary electron image is adjusted by correctly adjusting the electron beam to pass through the center of the through hole. Can be observed.

  According to the eighth invention, since the deflector for correcting the axial deviation of the electron beam by the electric field perpendicular to the optical axis of the electron beam formed by the electrode is provided above the objective lens, A normal secondary electron image can be observed by correcting so that the axis of the electron beam inclined due to the influence of the electric field generated by the electrode provided for discharging floating electrons is not inclined.

  According to the ninth aspect of the invention, since the detector for discharged electrons for detecting the stray electrons discharged by the scattered floating electron discharge mechanism is provided, the detection signal of the discharged electron detector is sent from the secondary electron detector. By displaying the image by performing operations such as switching, addition, or subtraction with the obtained detection signal, it is possible to obtain secondary effects such as improving the sensitivity of the secondary electron image and acquiring information about the charged region.

According to the tenth invention, the objective lens for narrowing the electron beam to irradiate the sample, the scanning means for scanning the irradiation position of the electron beam on the sample, and generated from the sample by the electron beam irradiation In a scanning electron microscope provided with a detection means for detecting the electrons and a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
Scattering composed of a conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and a magnetic pole disposed on the conductive plate and capable of selecting an S pole and an N pole Equipped with a floating electron discharge mechanism,
Since scattered magnetic electrons are discharged by a magnetic field formed by the magnetic pole in a plane direction perpendicular to the optical axis of the electron beam,
Scattered floating electrons generated in the space between the sample and the objective lens by electron beam irradiation to the sample are formed in a plane direction perpendicular to the optical axis of the electron beam by the magnetic poles configured in the scattered floating electron discharge mechanism By the applied magnetic field, the sample can be discharged out of the space between the sample and the objective lens to prevent the sample from being charged.

According to the eleventh invention,
An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. Equipped with a scattered floating electron emission mechanism composed of electrodes
Scattered stray electrons generated in the space between the sample and the objective lens due to electron beam irradiation on the sample are formed in a plane direction perpendicular to the optical axis of the electron beam by the electrode configured in the scattered stray electron discharge mechanism. Since the electric field is discharged outside the space between the sample and the objective lens and the sample is prevented from being charged,
With a simple configuration and simple operation, charging of the sample is prevented, and high-resolution secondary electron image observation becomes possible.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS. However, the present invention is not limited to the embodiments. FIG. 2 shows a schematic configuration example of an SEM implementing the present invention. In FIG. 2, components that perform the same or similar operations as those in the conventional SEM shown in FIG. The acceleration power source 9, the drive unit 10, the image signal processing unit 11, the sample stage control unit 12, the control arithmetic processing unit 13, the display unit 14, the operation unit 15, and the bus 16 shown in FIG. Although included in the configuration example of the invention, it is omitted in FIG. 2 for the sake of simplicity.

  FIG. 2 shows a state in which a scattered floating electron discharge mechanism composed of a conductive plate 23 and electrodes 21 a and 21 b supported by the conductive plate 23 is inserted between the objective lens 4 and the sample 5. . Power sources 22a and 22b are connected to the electrodes 21a and 21b, respectively. However, when the voltage applied to the electrodes is negative, the electrodes 21a and 21b are referred to as eviction electrodes 21a, and when the voltages are positive, they are referred to as suction electrodes 21b.

  FIG. 4 is an enlarged view in which only the scattered floating electron discharge mechanism 20 is taken out. FIG. 4A is a plan view of the scattered floating electron discharge mechanism 20 as viewed from the objective lens 4 side. 4b is a cross-sectional view taken along the line AA of FIG. 4a. On the surface of the conductive plate 23 facing the objective lens 4, a discharge electrode 21 a and a suction electrode 21 b are disposed so as to be electrically insulated from the conductive plate 23 by insulators 25 a and 25 b. Lead wires 26a and 26b are insulated from the conductive plate 23 and are wired to the electrodes 21a and 21b. The lead wires 26a and 26b are for applying a negative or positive voltage to the electrodes 21a and 21b.

Between the purge electrode 21a and the suction electrode 21b, a through hole 23a for allowing the electron beam EB to pass therethrough is provided. The position of the through hole 23a may be on the line connecting the purge electrode 21a and the suction electrode 21b, but it is not always necessary to be at the middle point between both electrodes. In FIG. 4, the position of the through hole 23a is shown close to the eviction electrode 21a side, but this is not necessary.
The conductive plate 23 is held by a moving / holding mechanism (not shown) at the right end (only shown partway in FIG. 2a) on the side of the suction electrode 21b, and the conductive plate 23 is inserted and retracted as necessary. Can be done. In addition, the moving / holding mechanism moves the position of the through hole in the plane direction perpendicular to the optical axis of the electron beam after inserting the scattered floating electron discharging mechanism 20 between the objective lens 4 and the sample 5 to perform alignment. An adjustment mechanism is provided.

Next, the operation of the scattered floating electron discharge mechanism 20 will be described.
As described above, when observing a non-conductive sample, the secondary electrons emitted directly from the sample 5 and the secondary electrons generated indirectly by the collision of the reflected electrons with the objective lens 4 are the objective lens. 4 and the sample 5 are in a floating state. These scattered stray electrons again fly to the sample surface and increase the charge of the sample. As a result, the surface structure of the sample cannot be observed, or normal image observation cannot be performed due to an increase in drift, noise, etc. of the observed image. When such a situation occurs, the scattered floating electron discharging mechanism 20 is inserted between the objective lens 4 and the sample 5 to discharge the floating electrons.

  When the scattered floating electron discharge mechanism 20 is inserted, the electron beam EB passes through the through hole 23a and is irradiated to the sample. Among the generated secondary electrons, electrons having a relatively large upward initial velocity component are wound up by the magnetic field of the objective lens along the optical axis of the electron beam EB and reach the secondary electron detector 6. However, since there exist secondary electrons having initial velocity components in various directions including secondary electrons returning downward from the lower part of the objective lens 4, not all secondary electrons are necessarily directed upward of the objective lens. Do not mean. That is, even if the conductive plate member 23 is present, many floating electrons still exist in the vicinity of the through hole.

  Therefore, when the scattered floating electron discharging mechanism 20 is inserted, a negative voltage is applied to the purge electrode 21a. As a result, the scattered stray electrons start to move in the direction opposite to the purge electrode 21a by receiving a force from the electric field generated in the direction perpendicular to the optical axis of the electron beam EB. In addition, a space between the objective lens 4 and the sample 5 is applied by applying a positive voltage to the suction electrode 21b and applying a force in the direction from the extraction electrode 21a to the suction electrode 21b to the scattered floating electrons that have started to move. The scattered stray electrons generated inside are discharged out of the space between the objective lens 4 and the sample 5. The discharge electron trajectory DE of FIG. 2 is an example schematically showing the trajectory of the electrons thus discharged.

  Some of secondary electrons and reflected electrons generated from the sample 5 by irradiation with the electron beam EB are blocked by the conductive plate 23. Since the conductive plate 23 is maintained at the ground potential through a moving / holding mechanism (not shown), secondary electrons having low energy collide with the conductive plate 23 and are absorbed as they are. When reflected electrons having higher energy than secondary electrons collide with the lower surface of the conductive plate 23, secondary electrons are indirectly generated. When the secondary electrons return to the sample again, charging is increased. For this reason, it is desirable that the lower surface of the conductive plate member 23 be formed of a material having as low a secondary electron generation efficiency as possible.

  When a metal such as brass is used as the conductive plate 23, it is known that brass is a substance having a relatively high secondary electron generation efficiency. Therefore, it is desirable to cover the lower surface where the reflected electrons collide with a material having a lower secondary electron generation efficiency than brass. FIG. 4b shows a case where a coating layer 24 for reducing the secondary electron generation efficiency is provided. The secondary electron efficiency of various materials is already well known, but for the purposes of the present invention, for example, conductive paints based on carbon can be used. A conductive paint containing carbon as a main component is known as a material that has conductivity and satisfies the conditions of a substance having low secondary electron generation efficiency and is relatively inexpensive and easily available.

  However, in the present invention, it is not always necessary to provide the coating layer 24 separately from the conductive plate 23, and from the beginning, the conductive plate 23 using a conductive material mainly composed of carbon such as graphite. May be configured. In this case, it is not necessary to form all of the conductive plate 23 with a single material such as graphite. For example, the tip near the through hole 23a is made of a material such as graphite, and the portion close to the moving / holding mechanism is For example, a structure using a metal such as brass having sufficient strength may be used.

In the above description, the scattering floating electron discharging mechanism 20 of FIG. 4 has been shown as an example in which two electrodes of the extraction electrode 21a and the suction electrode 21b are provided. However, the number of the electrodes is not necessarily two. If either 21a or suction electrode 21b is provided, scattered floating electrons can be discharged.
Further, there is no need to provide one purge electrode 21a and one suction electrode 21b, and each may be composed of a plurality of electrodes.
Further, the position where these electrodes are attached may be on the surface of the conductive plate 23 facing the sample 5.
Further, these electrodes may be provided simultaneously on both sides of the surface of the conductive plate 23 facing the objective lens 4 and the surface facing the sample 5 so that floating electrons are discharged on each side.

Next, a method for correcting an axial misalignment of an electron beam due to an electric field in a plane direction perpendicular to the optical axis of the electron beam will be described. The orbit of the electron beam EB is also affected by the electric field generated to discharge the scattered stray electrons. A deflector for correcting the inclination of the axis of the electron beam EB is provided above the scattered floating electron discharge mechanism 20. FIG. 2 shows a state in which a deflector 27 for this purpose is provided between the objective lens and the scanning coil 3. The deflector 27 is connected to the drive unit 10 although not shown in FIG.
Here, the deflector 27 does not necessarily have to be provided between the objective lens and the scanning coil 3, and only needs to be above the scattered floating electron discharge mechanism 20 and correct the axis of the electron beam EB. Alternatively, an operation equivalent to that performed by the deflector 27 may be realized by superimposing on the scanning coil 3.

  Next, FIG. 3 will be described. FIG. 3 shows a schematic configuration example in the case where the detector 300 for the scattered electron discharge electrons is configured in the mirror body 300. If the discharged electron detector 30 is removed from the mirror body 300, the configuration is the same as that of the mirror body 200 of FIG. Therefore, the acceleration power source 9, the drive unit 10, the image signal processing unit 11, the sample stage control unit 12, the control arithmetic processing unit 13, the display unit 14, the operation unit 15, and the bus 16 shown in FIG. Although included in the configuration example, it is omitted in FIG. 3 in order to simplify the drawing as in the case of FIG. The output of the discharged electron detector 30 is input to the image signal processing unit 11 (not shown), and is switched to the signal input from the secondary electron detector 6 or performs operations such as switching, addition, and subtraction. Can be done.

  For the purpose of preventing or reducing the electrification of the sample, it is not necessary to configure the discharged electron detector 30, and the configuration shown in FIG. 2 is sufficient. However, it is considered that the secondary electrons and the reflected electrons that generate the scattered stray electrons have some information about the sample surface. Therefore, if the detection signal of the discharge electron detector 30 is switched or added to or subtracted from the detection signal obtained from the secondary electron detector 6 to display an image, the sensitivity of the secondary electron image can be improved and charged. It is possible to obtain a secondary effect such as information acquisition related to the area.

  The scattered floating electron discharge mechanism described above is provided with an electrode that generates an electric field and discharges scattered floating electrons. However, the same effect can be obtained by providing a magnetic pole that generates a magnetic field instead of an electric field. it is obvious.

The figure which shows the schematic structural example of the conventional scanning electron microscope. The figure which shows the schematic structural example of the scanning electron microscope which implements this invention. The figure which shows the other schematic structural example of the scanning electron microscope which implements this invention. The figure which shows the structural example of the scattering floating electron discharge mechanism of this invention.

Explanation of symbols

(Those that perform the same or similar operations are denoted by a common reference.)
EB electron beam SE secondary electron orbit FE scattered floating electron orbit DE discharge electron orbit 1 electron gun 2 focusing lens 3 scanning coil 4 objective lens 5 sample 6 secondary electron detector 7 sample stage 8 sample stage 9 acceleration power source
10 Drive unit
11 Image signal processor
12 Sample stage controller
13 Control processing unit
14 Display device
15 Operation unit
16 bus
20 Scattered floating electron emission mechanism
21a, 21b electrode
22a, 22b Power supply
23 Conductive plate
23a Through hole
24 Coating layer
25a, 25b insulation
26a, 26b Lead wire
27 Axis deviation corrector
30 Detector for emitted electrons
100, 200, 300 mirror

Claims (11)

An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. A scanning electron microscope comprising a scattered floating electron emission mechanism composed of an electrode that can be formed. 2. The scanning electron microscope according to claim 1, wherein a coating layer made of a substance having a lower secondary electron generation efficiency than the conductive plate is formed on a surface of the conductive plate facing the sample. . 3. The scanning electron microscope according to claim 1, wherein a coating layer made of a material having a secondary electron generation efficiency lower than that of the conductive plate material is formed of a material containing carbon as a main component. The scanning electron microscope according to claim 1, wherein the conductive plate material is made of a substance mainly composed of carbon. The scanning electron microscope according to any one of claims 1 to 4, wherein at least a surface of the conductive plate facing the sample is maintained at a ground potential. The scanning electron microscope according to claim 1, further comprising a retracting mechanism for retracting the scattered floating electron discharging mechanism from the electron beam path. An adjustment mechanism is provided, wherein the conductive plate is moved in a direction perpendicular to an optical axis of an electron beam to align a through hole through which an electron beam is provided in the conductive plate. Item 7. A scanning electron microscope according to any one of Items 1 to 6. 8. A deflector for correcting an axial misalignment of an electron beam by an electric field in a direction perpendicular to the optical axis of the electron beam formed by the electrode is provided above the objective lens. A scanning electron microscope according to any one of the above. The scanning electron microscope according to claim 1, further comprising a discharge electron detector for detecting stray electrons discharged by the scattered floating electron discharge mechanism. An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
Scattering composed of a conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and a magnetic pole disposed on the conductive plate and capable of selecting an S pole and an N pole A scanning electron microscope comprising a floating electron discharge mechanism. An objective lens for narrowing the electron beam and irradiating the sample; a scanning unit for scanning the irradiation position of the electron beam on the sample; and a detecting unit for detecting electrons generated from the sample by the electron beam irradiation; In a scanning electron microscope comprising a display means for displaying a detection signal from the detection means as an image in synchronization with the scanning means,
A conductive plate having a through-hole through which an electron beam passes and disposed between the objective lens and the sample, and positive and negative voltages that are electrically insulated and arranged on the conductive plate are selectively applied. Equipped with a scattered floating electron emission mechanism composed of electrodes
Scattered stray electrons generated in the space between the sample and the objective lens due to electron beam irradiation on the sample are formed in a plane direction perpendicular to the optical axis of the electron beam by the electrode configured in the scattered stray electron discharge mechanism. An antistatic method, wherein the sample is discharged out of a space between the sample and the objective lens by an electric field to prevent the sample from being charged.

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