JP2020009779A - Charged particle beam device - Google Patents

Abstract

To realize a charged particle beam device that can operate, process, or measure a sample while performing observation with high resolution.SOLUTION: An charged particle beam device includes an electron source that emits a primary electron beam (12), and a lower objective lens (26) that focuses the primary electron beam (12) emitted from the electron source onto a sample (23), and the lower objective lens (26) is placed on the opposite side of the sample (23) from the side where the primary electron beam (12) enters, and the arrangement configuration of the upper part of the sample (23) is determined such that a space for performing any one of the processing, to the sample (23), to operate, process, and measure the sample (23) is secured on the upper part of the lower objective lens (26).SELECTED DRAWING: Figure 9

Description

  The present invention relates to a charged particle beam device.

  Conventional charged particle beam devices include a scanning electron microscope (hereinafter abbreviated as "SEM"), an EPMA (Electron Probe Micro Analyzer), an electron beam welding machine, an electron beam lithography device, and an ion beam microscope. Known as technology.

  In the conventional SEM (Patent Documents 1, 2, and 3), the aberration of the electron beam in the objective lens increases, and the resolution is insufficient. For this reason, a technique for suppressing aberration is required for high-resolution observation.

  As such a technique, there is a retarding technique for generating an electric field between a sample and an objective lens for decelerating a primary electron beam. Usually, a negative voltage is applied to the sample. In this case, the aberration of the objective lens is reduced. By using the retarding technique, high-resolution observation can be realized even with low incident energy.

JP-A-9-171791 (published on June 30, 1997) JP-A-2000-133194 (released on May 12, 2000) JP-A-8-68772 (published on March 12, 1996)

  When using the retarding technique, a potential plate is arranged in a space on the electron gun side with respect to the sample, and a potential difference is given between the potential plate and the sample. Usually, since a negative voltage is applied to the sample, if the surface of the sample on the potential plate side is sharp, a strong electric field is generated around the sharpness, causing a problem that discharge occurs between the potential plate and the sample. is there.

  For example, if a retarding voltage is applied while dust or the like adheres to the sample surface, the dust rises in the direction of the electric field, and as a result, sharpness may occur on the sample surface. In particular, the sharper the sharpness of the sample surface and the greater the potential difference, the more the electric field concentration occurs around the sharpness, and the above problem becomes more serious. The potential difference between the potential plate and the sample cannot be increased, and it is difficult to realize the retarding technique.

  There is also a problem that the electric field concentration on the sample surface deteriorates the sample characteristics. Further, there is a problem that the trajectory of the primary electron beam emitted from the electron gun is bent.

  This is because, in addition to the sharpness of the sample surface described above, for example, (1) when the surface of the sample on the potential plate side has irregularities, (2) the sample surface is inclined and the sample is made of an insulator. Even if the electric field distribution generated between the electric potential plate and the electric potential plate is not parallel to the sample table, there is a problem that can occur even when the electric field distribution is not parallel to the sample stage.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a charged particle beam apparatus using a retarding technique, in which, for various samples, an electric field generated on the sample surface is reduced, and the retarding technique is used. It is an object of the present invention to realize a charged particle beam device excellent in the effectiveness of the present invention.

  Further, an object of the present invention is to perform an operation, processing, or measurement on a sample above a lower objective lens in a charged particle beam apparatus including a lower objective lens arranged in a space on the opposite side of the electron gun when viewed from the sample. To provide a charged particle beam apparatus that can operate, process, or measure a sample while observing with high resolution by providing a space in which various devices for the apparatus can be arranged.

  In order to solve the above problems, a charged particle beam device according to one embodiment of the present invention includes a charged particle source that emits a charged particle beam, and a lower portion that focuses the charged particle beam emitted from the charged particle source on a sample. An objective lens, wherein the lower objective lens is disposed on a side opposite to a side where the charged particle beam is incident on the sample, and an upper portion of the lower objective lens is provided for operation, processing, or measurement of the sample. The arrangement configuration of the upper part of the sample is determined so that a space including at least one of them for performing the processing on the sample is secured.

  According to one embodiment of the present invention, by using the lower objective lens, it is possible to measure and manipulate the sample while observing the sample with high resolution. Further, when the sample is observed at low magnification, the primary electron beam may be focused by using the upper objective lens. This makes it possible to realize a charged particle beam apparatus capable of operating, processing, or measuring a sample while performing high-resolution observation.

FIG. 1 is a schematic sectional view illustrating a configuration of an SEM according to a first embodiment of the present invention. FIG. 6 is a schematic sectional view illustrating a configuration of an SEM according to a second embodiment of the present invention. FIG. 9 is a schematic sectional view illustrating a configuration of an SEM according to a third embodiment of the present invention. FIG. 9 is a schematic sectional view illustrating a configuration of an SEM according to a fourth embodiment of the present invention. It is a schematic sectional view explaining the composition of the SEM concerning Embodiment 5 of the present invention. FIG. 13 is a schematic sectional view illustrating a configuration of an SEM according to a sixth embodiment of the present invention. It is a schematic sectional view explaining the composition of the SEM concerning Embodiment 7 of the present invention. It is a schematic sectional view explaining the composition of the SEM concerning Embodiment 8 of the present invention. It is a schematic sectional view explaining the composition of the SEM concerning Embodiment 9 of the present invention.

  An embodiment of the present invention will be described with reference to the drawings. It should be noted that the following drawings are schematic, and dimensions and aspect ratios are different from actual ones. The following embodiments of the present invention exemplify apparatuses and methods for embodying the technical idea of the present invention. The technical concept of the present invention does not specify the materials, shapes, structures, arrangements, and the like of the components as follows. Various changes can be made to the technical idea of the present invention within the technical scope described in the claims.

[Embodiment 1]
With reference to FIG. 1, the schematic configuration of the SEM according to the first embodiment of the present invention will be described.

(Basic configuration of SEM)
The SEM includes an electron source (charged particle source) 11, an acceleration power source 14, a condenser lens 15, an objective lens aperture 16, a two-stage deflection coil 17, an upper objective lens 18, a lower objective lens 26, It is an electron beam device provided with the vessel 20. The acceleration power supply 14 accelerates the primary electron beam (charged particle beam) 12 emitted from the electron source 11. The condenser lens 15 focuses the accelerated primary electron beam 12. The objective lens aperture 16 removes unnecessary portions of the primary electron beam 12. The two-stage deflection coil 17 scans the primary electron beam 12 two-dimensionally on the sample 23. The upper objective lens 18 and the lower objective lens 26 focus the primary electron beam 12 on the sample 23. The detector 20 detects signal electrons 21 (secondary electrons 21a and reflected electrons 21b) emitted from the sample 23.

  The SEM includes an upper objective lens power supply 41, a lower objective lens power supply 42, and a controller 45 as a control unit of an electromagnetic lens including the upper objective lens 18 and the lower objective lens 26. The upper objective lens power supply 41 varies the strength of the upper objective lens 18. The lower objective lens power supply 42 varies the strength of the lower objective lens 26. The control device 45 controls the upper objective lens power supply 41 and the lower objective lens power supply 42.

  The control device 45 can control the intensity of the upper objective lens 18 and the intensity of the lower objective lens 26 independently. The control device 45 can control both lenses simultaneously.

  As the electron source 11, a thermionic emission type (thermoelectron source type) or a field emission type (Schottky type or cold cathode type) can be used. In the first embodiment, a crystal electron source such as thermionic emission type LaB6 or a tungsten filament is used as the electron source 11. For example, an acceleration voltage of −0.5 kV to −30 kV is applied between the electron source 11 and the anode plate 14 d (ground potential). The Wehnelt electrode 13 is supplied with a potential that is more negative than the potential of the electron source 11. Thereby, the amount of the primary electron beam 12 generated from the electron source 11 is controlled. Then, just before the electron source 11, a crossover diameter, which is the first minimum diameter of the primary electron beam 12, is formed. This minimum diameter is called the size So of the electron source.

  The accelerated primary electron beam 12 is focused by the condenser lens 15. Thereby, the size So of the electron source is reduced. The condenser lens 15 adjusts the reduction ratio and the current applied to the sample 23 (hereinafter, referred to as a probe current). Then, unnecessary trajectories of electrons are removed by the objective lens aperture 16. The opening angle α of the beam incident on the sample 23 and the probe current are adjusted according to the hole diameter of the objective lens aperture 16.

  The primary electron beam 12 that has passed through the objective lens aperture 16 passes through a two-stage deflection coil 17 for scanning, and then passes through an upper objective lens 18. The general-purpose SEM focuses the primary electron beam 12 on the sample 23 using the upper objective lens 18. The SEM of FIG. 1 can also be used in such a manner.

  In FIG. 1, the configuration from the electron source 11 to the upper objective lens 18 constitutes an upper device 71 for emitting the primary electron beam 12 toward the sample 23. Further, the lower device 72 is constituted by the potential plate 22 and members arranged below the potential plate 22. The sample 23 is held by the lower device 72. The upper device 71 has a hole 18c from which the primary electron beam 12 passing through the inside is finally emitted. In the first embodiment, the hole 18c exists in the upper objective lens 18. The detector 20 is mounted below the hole 18c. The detector 20 also has an opening through which the primary electron beam 12 passes. The detector 20 is attached to the lower part of the upper objective lens 18 such that the opening of the detector 20 and the hole 18c overlap. A plurality of detectors 20 may be mounted below the upper objective lens 18. The plurality of detectors 20 are arranged so that the trajectory of the primary electron beam 12 is not obstructed, and the detectors of the detectors 20 are as small as possible except for the hole 18c of the upper device 71. Attached between the device 72.

  The primary electron beam 12 that has passed through the upper objective lens 18 is reduced and focused by the lower objective lens 26. The lower objective lens 26 realizes a low-aberration lens having a stronger magnetic field distribution as it approaches the sample 23. The upper objective lens 18 is used for controlling the opening angle α and adjusting the reduction ratio, the shape of the lens, and the depth of focus so that an image can be easily viewed. That is, the upper objective lens 18 is used to optimize each of these control values. If the primary electron beam 12 cannot be focused by the lower objective lens 26 alone, the upper objective lens 18 can assist in focusing the primary electron beam 12.

  When retarding is not performed, the potential plate 22 may be removed. Further, the potential plate 22 is detachable, and can be replaced with a new potential plate 22. The sample 23 is preferably set so as to be as close to the lower objective lens 26 as possible. More specifically, the sample 23 is preferably installed close to the upper part of the lower objective lens 26 so that the distance from the upper part (upper surface) of the lower objective lens 26 is 5 mm or less.

  The primary electron beam 12 scans over the sample 23 with the energy accelerated by the acceleration power supply 14. At this time, the secondary electrons 21a are wound around the magnetic flux by the magnetic field of the lower objective lens 26 and rise while spirally moving. When the secondary electrons 21 a move away from the surface of the sample 23, the magnetic flux density is rapidly reduced, so that the secondary electrons 21 a are swung away from the swirl and diverge, and are deflected by the electric field drawn from the secondary electron detector 19 to be deflected. Captured at 19. That is, the secondary electron detector 19 is arranged such that the electric field generated from the secondary electron detector 19 attracts secondary electrons emitted from the sample by the charged particles. In this way, the number of secondary electrons 21a entering the secondary electron detector 19 can be increased.

  Since the magnetic flux density on the optical axis of the lower objective lens 26 has a stronger distribution as it is closer to the sample, the lower objective lens 26 becomes a low-aberration lens when retarding. When a negative potential is applied to the sample 23, the primary electron beam 12 is decelerated as it approaches the sample 23. The lower the velocity of the primary electron beam 12 becomes, the more easily the primary electron beam 12 is affected by the magnetic field. Therefore, when a negative potential is applied to the sample 23, the lower objective lens 26 becomes a lens with even lower aberration.

  Further, the signal electrons 21 are accelerated by an electric field due to the retarding voltage of the sample 23, are amplified in energy, and enter the detector 20. Therefore, the detector 20 has high sensitivity. With such a configuration, a high-resolution electron beam device can be realized.

  The distance between the upper objective lens 18 and the lower objective lens 26 is set to 10 mm to 200 mm. More preferably, the thickness is set to 30 mm to 50 mm. When the distance between the upper objective lens 18 and the lower objective lens 26 is shorter than 10 mm, the reflected electrons 21b can be detected by the detector 20 placed immediately below the upper objective lens 18. However, the secondary electrons 21a are easily drawn into the upper objective lens 18 during retarding. By making the distance between the upper objective lens 18 and the lower objective lens 26 10 mm or more, the secondary electrons 21a are easily detected by the detector 20. In addition, when the gap between the upper objective lens 18 and the lower objective lens 26 is about 30 mm, it is very easy to take the sample 23 in and out.

  Next, the configuration of each component will be described in detail. First, the shape of the lower objective lens 26 will be described with reference to FIG.

  The magnetic poles forming the lower objective lens 26 include a central magnetic pole 26a whose central axis coincides with an ideal optical axis of the primary electron beam 12, an upper magnetic pole 26b, a cylindrical side magnetic pole 26c, and a lower magnetic pole 26d. The center magnetic pole 26a is shaped such that the diameter decreases as it goes upward. The upper portion of the center magnetic pole 26a has, for example, a one-stage, multi-stage or curved truncated cone shape. The lower part of the center magnetic pole 26a has a cylindrical shape. There is no through hole in the central axis below the central magnetic pole 26a. The upper magnetic pole 26b has a disk shape in which the side near the center of gravity of the central magnetic pole 26a is tapered toward the center and becomes thinner. An opening having an opening diameter d is open at the center of the upper magnetic pole 26b. The tip diameter D of the center magnetic pole 26a is larger than 6 mm and smaller than 14 mm. The relationship between the opening diameter d and the tip diameter D is d−D ≧ 4 mm.

  Next, a specific example of the magnetic pole will be described. The upper surfaces of both the center magnetic pole 26a and the upper magnetic pole 26b on the sample side have the same height. The outer diameter of the lower portion of the central magnetic pole 26a is 60 mm. If the outer diameter is small, the magnetic permeability is undesirably reduced.

  When the center magnetic pole 26a is D = 8 mm, the opening diameter d of the upper magnetic pole 26b is preferably set to 12 mm to 32 mm. More preferably, the opening diameter d is from 14 mm to 24 mm. As the aperture diameter d increases, the magnetic flux density distribution on the optical axis becomes gentler and the width increases, and the AT (ampere turn: the number of coil turns N [T] and the current I [A] necessary for focusing of the primary electron beam 12 are obtained. ]) Can be reduced. However, when the relationship between the opening diameter d and the tip diameter D satisfies d> 4D, the aberration coefficient increases. Here, the opening diameter d of the upper magnetic pole 26b is 20 mm, and the outer diameter of the side magnetic pole 26c is 150 mm. Further, a through hole may be provided at the axis center of the center magnetic pole 26a.

  Here, for example, when the primary electron beam 12 is focused on the sample 23 having a thickness of 5 mm even at a high acceleration voltage of 30 kV, the tip diameter D is preferably larger than 6 mm and smaller than 14 mm. If D is too small, the magnetic pole is saturated and the primary electron beam 12 is not focused. On the other hand, when D is increased, performance deteriorates. On the other hand, if the difference between d and D is smaller than 4 mm, the magnetic poles are too close to each other and are likely to be saturated, so that the primary electron beam 12 is not focused. If the distance between the upper objective lens 18 and the lower objective lens 26 is 10 mm or less, workability deteriorates. If this distance is longer than 200 mm, the opening angle α becomes too large. In this case, in order to optimize the aberration, it is necessary to make adjustment using the upper objective lens 18 to reduce α, and the operability deteriorates.

  Further, for example, when only the acceleration voltage of 5 kV or less is used and the thickness of the sample 23 is small, the tip diameter D may be 6 mm or less. However, for example, when the acceleration voltage is 5 kV, if D is 2 mm, d is 5 mm, the thickness of the sample 23 is 5 mm, and only the lower objective lens 26 is used, the magnetic pole is saturated, and the primary electron beam 12 Do not focus. However, if the sample 23 is limited to a thin one, the lens can have higher performance.

  As a method of applying a potential to the sample 23, a part of the magnetic pole of the lower objective lens 26 is floated from a ground potential with an electrical insulating portion interposed therebetween, and a retarding voltage is applied to the sample 23 and a part of the magnetic pole. Can also. However, in this case, if a non-magnetic material is sandwiched in the magnetic circuit, the magnetic lens becomes weak. Also, when the retarding voltage is increased, discharge occurs. When the electrical insulating portion is thickened, there is a problem that the magnetic lens becomes weaker.

  As shown in FIG. 1, it is desirable to place a seal portion 26f (for example, copper, aluminum, or Monel) made of a non-magnetic material between the upper magnetic pole 26b and the center magnetic pole 26a. The seal portion 26f makes the space between the upper magnetic pole 26b and the center magnetic pole 26a vacuum-tight by an O-ring or brazing. In the lower objective lens 26, the vacuum side and the atmosphere side are air-tightly separated by the upper magnetic pole 26b, the seal portion 26f, and the center magnetic pole 26a. Although not shown, the upper magnetic pole 26b and the vacuum vessel are airtightly connected by an O-ring. By doing so, the lower objective lens 26 can be exposed to the atmosphere except for the surface on the vacuum side. Therefore, the lower objective lens 26 is easily cooled.

  Although the lower objective lens 26 can be placed in a vacuum container, the degree of vacuum is reduced. This is because when the coil portion 26e is on the vacuum side, it becomes a gas emission source. If the vacuum side and the atmosphere side are not air-tightly separated in this manner, there is a problem that when vacuum is evacuated, the gas passes through the place where the lower objective lens 26 and the insulating plate 25 are in contact, and the sample moves. is there.

  The coil section 26e can have a coil current of, for example, 6000AT. When the temperature of the coil becomes high due to heat generation, the coating of the winding may be melted to cause a short circuit. By allowing the lower objective lens 26 to be exposed to the atmosphere, the cooling efficiency is increased. For example, if the base on the lower surface of the lower objective lens 26 is made of aluminum, the base can be used as a heat sink. Then, the lower objective lens 26 can be cooled by an air cooling fan or water cooling. Such airtight separation allows the lower objective lens 26 to be strongly excited.

  The retarding unit will be described with reference to FIG.

  The insulating plate 25 is placed on the lower objective lens 26. The insulating plate 25 is, for example, a polyimide film, a polyester film, or the like having a thickness of about 0.1 mm to 0.5 mm, a fluororesin, a ceramic plate, or the like. To increase the retarding voltage, the thickness of the insulating plate 25 may be increased from 0.5 mm to about 2 mm. Then, a conductive sample table 24 having no magnetism is placed thereon. The sample stage 24 is, for example, an aluminum plate having a bottom surface of 250 μm in thickness, and is processed into a curved surface shape in which the peripheral edge is separated from the insulating plate 25 as it approaches the peripheral edge. The sample table 24 may be one in which a gap between the curved surface portion and the insulating plate 25 is further filled with an insulating material 31. By doing so, the withstand voltage between the lower objective lens 26 and the sample stage 24 is increased, and the device can be used stably. The plane shape of the sample stage 24 is circular, but may be any shape such as an ellipse or a rectangle.

  The sample 23 is placed on the sample stage 24. The sample stage 24 is connected to a retarding power supply 27 to apply a retarding voltage. The retarding power supply 27 is a power supply whose output can be varied from 0 V to −30 kV, for example. The sample stage 24 is connected to a sample stage stage plate 29 made of an insulating material so that the sample stage 24 can be moved from outside the vacuum. Thus, the position of the sample 23 can be changed. The sample stage plate 29 is connected to the second XY-direction stage adjustment unit 56c and can be moved from outside the vacuum.

  A potential plate 22 having a circular opening is disposed on the sample 23. The potential plate 22 is installed perpendicular to the optical axis of the lower objective lens 26. The potential plate 22 is arranged insulated from the sample 23. The potential plate 22 is connected to a potential plate power supply 28. The potential plate power supply 28 is a power supply whose output is variable, for example, 0 V and -10 kV to +10 kV. The diameter of the circular opening of the potential plate 22 may be about 2 mm to about 20 mm. More preferably, the diameter of the opening may be from 4 mm to 12 mm. Alternatively, the portion of the potential plate 22 through which the primary electron beam 12 or the signal electrons 21 pass may be formed into a conductive mesh. The mesh portion of the mesh is preferably thinned so that electrons can easily pass therethrough, and the aperture ratio may be increased. The potential plate 22 is connected to the first XY-direction stage adjustment unit 56b so that the position can be moved from outside the vacuum for center axis adjustment.

  The periphery of the sample stage 24 has a thickness on the side of the potential plate 22. For example, if the potential plate 22 is flat, the potential plate 22 is closer to the sample stage 24 at the periphery of the sample stage 24. In that case, discharge becomes easy. Since the potential plate 22 has a shape separated from the conductive sample stage 24 in a place other than near the sample 23, the withstand voltage with the sample stage 24 can be increased.

  The potential plate 22 is arranged so as not to be discharged by being separated from the sample 23 by a distance of about 1 mm to 15 mm. However, they should be arranged so that they are not too far apart. The purpose is to superimpose the deceleration electric field at a position where the magnetic field generated by the lower objective lens 26 is strong. If the potential plate 22 is placed far from the sample 23, or if there is no potential plate 22, the primary electron beam 12 is decelerated before being focused by the lower objective lens 26, and the effect of reducing aberration is reduced. Decrease. If the opening of the potential plate 22 is too large and the distance between the sample 23 and the potential plate 22 is too short, the equipotential lines protrude largely toward the electron gun from the opening of the potential plate 22 and are distributed. In this case, the primary electrons may decelerate before reaching the potential plate 22. The smaller the opening diameter of the potential plate 22, the more effective it is to reduce the leakage of the electric field. However, it is necessary to prevent the signal electrons 21 from being absorbed by the potential plate 22. Therefore, while adjusting the potential difference between the sample 23 and the potential plate 22 within a range in which no discharge occurs, adjusting the distance between the sample 23 and the potential plate 22 and appropriately selecting the opening diameter of the potential plate 22 are required. It is important.

  By placing the potential plate 22 near the sample 23, the velocity of the primary electrons does not change much up to near the potential plate 22. Then, the speed of the primary electrons decreases as the position approaches the sample 23 from around the potential plate 22, and the primary electrons are easily affected by the magnetic field. Since the magnetic field produced by the lower objective lens 26 is also stronger as it is closer to the sample 23, the two effects are combined, so that the closer to the sample 23, the stronger the lens and the smaller the aberration.

  If the retarding voltage can be made close to the accelerating voltage while increasing the accelerating voltage as much as possible, the irradiation electron energy can be reduced and the depth at which electrons enter the sample 23 can be reduced. This enables high-resolution observation of the surface shape of the sample. Further, since the aberration can be reduced, an SEM with high resolution and low acceleration can be realized.

  In the first embodiment, the withstand voltage between the sample 23 and the potential plate 22 can be easily increased. The distance between the upper objective lens 18 and the lower objective lens 26 can be between 10 mm and 200 mm. Therefore, for example, in the case of the flat sample 23, if the distance between the sample 23 and the potential plate 22 is about 5 mm, a potential difference of about 10 kV can be relatively easily applied to the sample 23 and the potential plate 22. In the case of the sample 23 having a sharp portion, it is necessary to appropriately select a distance and an opening diameter so as not to discharge.

  As the detector 20 in the first embodiment, a semiconductor detector 20, a microchannel plate detector 20 (MCP), or a Robinson detector 20 of a phosphor emission type is used. At least one of them is arranged immediately below the upper objective lens 18. The secondary electron detector 19 is arranged so that an electric field is applied above the sample 23 so as to collect the secondary electrons 21a.

  The semiconductor detector 20, the MCP detector 20, or the Robinson detector 20 is in contact with the sample side of the upper objective lens 18, and is arranged within 3 cm from the optical axis. More preferably, a detector 20 is used in which the center of the detection unit is located on the optical axis and the center thereof is provided with an opening through which primary electrons pass. The reason why the signal electrons are set within 3 cm from the optical axis is that when retarding is performed, signal electrons travel near the optical axis.

  The primary electron beam 12 has a value obtained by subtracting the retarding voltage Vdecel from the acceleration voltage (Vacc) used for acceleration by the acceleration power supply 14, that is, energy obtained by multiplying electron charge by − (Vacc−Vdecel) [V]. The sample 23 is scanned. At that time, the signal electrons 21 are emitted from the sample 23. The effect of electrons depends on the values of the acceleration voltage and the retarding voltage. The backscattered electrons 21b receive a rotating force by the magnetic field of the lower objective lens 26, and at the same time accelerate due to an electric field between the sample 23 and the potential plate 22. Therefore, the spread of the emission angle of the reflected electrons 21b is narrowed, and the reflected electrons 21b are easily incident on the detector 20. The secondary electrons 21a also receive a rotating force due to the magnetic field of the lower objective lens 26, and at the same time, accelerate due to the electric field between the sample 23 and the potential plate 22 to detect the secondary electron 21a under the upper objective lens 18. Incident on the vessel 20. Both the secondary electrons 21a and the reflected electrons 21b are accelerated, the energy is amplified, and the energy is incident on the detector 20, so that the signal is increased.

  In a general-purpose SEM, electrons are usually focused by an objective lens such as the upper objective lens 18 arranged in a space on the electron gun side with respect to the sample. The upper objective lens 18 is usually designed to have a higher resolution as the sample 23 is closer to the upper objective lens 18. However, the semiconductor detector 20 and the like have a thickness, and it is necessary to separate the sample 23 from the upper objective lens 18 by the thickness. Further, if the sample 23 is too close to the upper objective lens 18, it becomes difficult for the secondary electrons 21 a to enter the secondary electron detector 19 outside the upper objective lens 18. For this reason, a general-purpose SEM uses a thin semiconductor detector 20 which is disposed immediately below the upper objective lens 18 and has an opening through which primary electrons pass. The sample 23 is placed with a small gap so as not to hit the detector 20. Therefore, the sample 23 and the upper objective lens 18 are slightly separated from each other, and it is difficult to achieve high performance.

  In the first embodiment, when the lower objective lens 26 is used as a main lens, the sample 23 can be installed close to the lower objective lens 26. Then, the distance between the upper objective lens 18 and the lower objective lens 26 can be increased. For example, if the distance is 30 mm, the MCP detector 20 having a thickness of about 10 mm can be placed immediately below the upper objective lens 18. In addition, a Robinson-type detector 20 and a semiconductor detector 20 can naturally be provided. There is also a method in which a reflector is placed, the signal electrons 21 are applied to the reflector, and electrons generated or reflected therefrom are detected by a second secondary electron detector. Various signal electron detectors 20 having the same function can be installed.

  Next, specific examples of various uses of the device according to the first embodiment will be described.

  For example, the acceleration voltage Vacc may be -4 kV, the sample 23 may be -3.9 kV, and the irradiation voltage Vi may be 100 V. As the ratio between the acceleration voltage and the retarding voltage is closer to 1, the aberration coefficient can be reduced. In the above description, the case where the magnetic pole of the lower objective lens 26 is set to D = 8 mm and d = 20 mm, but if D = 2 mm, d = 6 mm, etc., there are restrictions on the sample height and the acceleration voltage. The performance can be improved.

  When the acceleration voltage is -10 kV and there is no retarding, the secondary electrons 21 a can be detected by the secondary electron detector 19 but cannot be detected by the semiconductor detector 20. However, if the acceleration voltage is -20 kV and the retarding voltage is -10 kV, the secondary electrons 21a enter the semiconductor detector 20 and can be detected with an energy of about 10 keV.

  When the acceleration voltage is set to -10.5 kV and the retarding voltage is set to -0.5 kV, the secondary electrons 21 a cannot be detected with high sensitivity by the semiconductor detector 20. However, at this time, the secondary electrons 21a can be detected by the secondary electron detector 19. That is, the secondary electrons 21a can be captured by the secondary electron detector 19 when the retarding voltage is low, and the amount that can be detected by the semiconductor detector 20 increases as the retarding voltage is gradually increased. As described above, the secondary electron detector 19 is also useful at the time of adjusting the retarding voltage while focusing.

  The lower objective lens 26 is designed to focus primary electrons at 30 keV at Z = -4.5 mm. If the sample position is closer to the lower objective lens 26, for example, at a position of Z = -0.5 mm, primary electrons of 100 keV can also be focused. When retarding is not performed, the insulating plate 25 (insulating film) need not be placed on the lower objective lens 26. Therefore, in this case, the lower objective lens 26 can sufficiently focus the primary electron beam 12 having an acceleration voltage of -100 kV. Preferably, in the lower objective lens 26, the charged particle beam accelerated by setting the acceleration power source to any one of -30 kV to -10 kV is viewed from 0 mm to 4.0 mm when viewed from a position closest to the magnetic pole sample of the lower objective lens 26. It is designed so that it can be focused at any height of 5 mm.

  The case where the acceleration voltage is −15 kV, the sample 23 is −5 kV, and the potential plate 22 is −6 kV will be described. When the primary electrons hit the sample 23, they become 10 keV. The energy of the secondary electrons 21a emitted from the sample 23 is 100 eV or less. Since the potential of the potential plate 22 is 1 kV lower than the potential of the sample 23, the secondary electrons 21a cannot exceed the potential plate 22. Therefore, the secondary electrons 21a cannot be detected. The reflected electrons 21 b having an energy of 1 keV or more emitted from the sample 23 can pass through the potential plate 22. Further, there is a potential difference of 6 kV between the potential plate 22 and the detector 20 below the upper objective lens 18, and the reflected electrons 21b are accelerated and enter the detector 20. As described above, by adjusting the voltage of the potential plate 22, the potential plate 22 can be used as an energy filter, and the sensitivity can be increased by accelerating the signal electrons 21.

  Next, a case where the height of the sample is, for example, 7 mm will be described.

  At this time, even when the retarding is performed, the measurement is performed at a position of, for example, about Z = -7.75 mm including the thickness of the insulating plate 25 and the sample table 24 from the upper magnetic pole 26b. In this case, the primary electron beam 12 of 30 keV cannot be focused only by the lower objective lens 26. However, the primary electron beam 12 can be focused without lowering the acceleration voltage with the help of the upper objective lens 18.

  In addition, depending on the height of the sample 23, focusing with only the upper objective lens 18 may enable observation with higher performance. As described above, the optimum usage can be selected depending on the sample 23.

  Although the case where the distance between the upper objective lens 18 and the lower objective lens 26 is set to 40 mm has been described above, this distance may be fixed or movable. As the distance between the upper objective lens 18 and the lower objective lens 26 increases, the reduction ratio of the lens formed by the upper objective lens 18 and the lower objective lens 26 decreases. The opening angle α can be increased. In this way, α can be adjusted.

  If the retarding voltage is high, the signal electrons 21 pass near the optical axis and easily enter the opening through which the primary electrons of the detector 20 pass. Therefore, the smaller the opening of the detector 20 is, the better. The sensitivity is good if the opening of the detector 20 is about Φ1 to Φ2 mm. By adjusting the opening diameter and height of the potential plate 22 and slightly displacing the position of the potential plate 22 from the optical axis, the trajectory of the signal electrons 21 is adjusted so that the signal electrons 21 hit the detector 20 to improve the sensitivity. There is a way. Alternatively, an electric field and a magnetic field may be applied between the upper objective lens 18 and the lower objective lens 26 so that the electric field and the magnetic field are applied in a perpendicular direction, and the signal electrons 21 may be slightly bent. Since the traveling direction of the primary electrons and the traveling direction of the signal electrons 21 are opposite to each other, a weak electric field and a magnetic field may be provided to slightly bend the signal electrons 21. If it bends a little, it does not enter the opening at the center of the detector 20 and can be detected. Further, an electric field may be simply applied between the upper objective lens 18 and the lower objective lens 26 from the side with respect to the optical axis. Even in this case, the primary electrons are hardly affected, and if only the lateral displacement occurs, the influence on the image is small. For example, the trajectory of the signal electrons 21 can be controlled using an electric field generated by the collector electrode of the secondary electron detector 19 or the like.

  In the first embodiment, the lower objective lens 26 is used as a main lens. When the sample stage 24 is at the ground potential, the secondary electrons 21 a are detected by the secondary electron detector 19. The backscattered electrons 21b are detected by the semiconductor detector 20, the Robinson detector 20, or the like. When the sample 23 and the detector 20 are separated from each other by about 10 mm to 20 mm, detection can be performed with high sensitivity. However, when the distance is about 40 mm, the number of backscattered electrons 21b that do not enter the detector 20 increases, and the amount of backscattered electrons 21b detected decreases. At this time, when a retarding voltage is applied to the sample 23, the secondary electrons 21a are detected by the semiconductor detector 20, the Robinson detector 20, or the like. Further, by applying the retarding voltage, the spread of the backscattered electrons 21b is suppressed, and the semiconductor detector 20, the Robinson detector 20, and the like can detect with high sensitivity. As described above, even when the potential plate 22 is not provided, the retarding can be used.

  In the first embodiment, when the sample 23 is thick, the upper objective lens 18 may be used as the objective lens. The potential plate stage 61 for moving the potential plate 22 and the first XY-direction stage adjustment unit 56b can be used as a sample stage. The first XY-direction stage adjustment unit 56b can also move in a direction approaching the upper objective lens 18 (Z-direction stage adjustment unit 56a). Thus, the device is used like a general-purpose SEM. The reflected electrons 21 b are detected by the semiconductor detector 20 or the Robinson detector 20, and the secondary electrons 21 a are detected by the secondary electron detector 19. Normally, the sample 23 is at the ground potential, but can be easily retarded (retarding can be performed without the potential plate 22).

  When only the lower objective lens power supply 42 is used, the apparatus is configured such that the distance between the lower objective lens 26 and the sample measurement surface is shorter than the distance between the upper objective lens 18 and the sample measurement surface. When only the power supply 41 is used, the apparatus is configured such that the distance between the upper objective lens 18 and the sample measurement surface is shorter than the distance between the lower objective lens 26 and the sample measurement surface. In the case of a measurement of relatively low performance where high measurement performance is not required, even when only the upper objective lens power supply 41 is used, the distance between the lower objective lens 26 and the sample measurement surface is larger than the distance between the lower objective lens 26 and the sample measurement surface. It is not necessary to make the distance between the upper objective lens 18 and the sample measurement surface shorter. The distance between the lower objective lens 26 and the sample measurement surface may be shorter than the distance between the upper objective lens 18 and the sample measurement surface. That is, the sample 23 may be disposed between the upper objective lens 18 and the lower objective lens 26. For example, in the case of low magnification measurement, the sample 23 may be arranged near the lower objective lens 26, and only the upper objective lens 18 may be used using the upper objective lens power supply 41.

  When the retarding is performed in FIG. 1, the potential of the sample 23 becomes negative. It is also possible to apply a positive voltage to the potential plate 22 while keeping the sample 23 at the GND level (this method is called a boosting method). It is also possible to apply a negative voltage to the sample 23 and apply a positive potential to the potential plate 22 to further improve the performance as a low-acceleration SEM. As an example, a case will be described in which the upper objective lens 18 is set to the ground potential, +10 kV is applied to the potential plate 22, and the sample 23 is set to the ground potential. The acceleration voltage is -30 kV. The primary electrons are at 30 keV when passing through the upper objective lens 18, accelerated from the upper objective lens 18 toward the potential plate 22, and decelerated from around the potential plate 22 toward the sample 23.

  The signal electrons 21 are accelerated between the sample 23 and the potential plate 22, but are decelerated between the potential plate 22 and the detector 20. When the detector 20 is a semiconductor detector 20, the reflected electrons 21b can be detected. However, since the semiconductor detector 20 is at the ground potential, the secondary electrons 21a decelerate and cannot be detected. The secondary electrons 21a can be detected by the secondary electron detector 19. If a retarding voltage is applied to the sample 23, the secondary electrons 21a can also be detected by the semiconductor detector 20.

  Next, moving the intersection of the deflection trajectories by adjusting the two-stage deflection coil 17 will be described. The sample 23 is two-dimensionally scanned by the two-stage deflection coil 17. The electron source side of the two-stage deflection coil 17 is called an upper stage deflection coil 17a, and the sample side is called a lower stage deflection coil 17b.

  As shown in FIG. 1, the two-stage deflection coil 17 includes an upper stage deflection power supply 43 for varying the intensity of the upper stage deflection coil 17a, a lower stage deflection power supply 44 for varying the intensity of the lower stage deflection coil 17b, and an upper stage deflection power source 43. It is controlled by a controller 45 for controlling the lower deflection power supply 44.

  The upper deflecting coil 17a and the lower deflecting coil 17b are installed in a space on the side from which the primary electron beam 12 comes in when viewed from inside the upper objective lens 18 (installed upstream of the main lens surface of the upper objective lens 18, Alternatively, when the lower deflecting member is placed at the position of the lens main surface, it is installed upstream of the outer magnetic pole 18b). The current ratio used between the upper deflection power supply 43 and the lower deflection power supply 44 is variable by the control device 45.

  Due to the two-stage deflection coil 17, electrons have a trajectory passing near the intersection of the optical axis and the main surface of the upper objective lens 18. When the upper objective lens 18 is used as a main lens, the setting is made in this manner. When the lower objective lens 26 is used as a main lens, the intensity ratio between the upper deflection coil 17a and the lower deflection coil 17b is set so that electrons pass near the intersection between the main surface of the lower objective lens 26 and the optical axis. It is adjusted to. The adjustment is performed by a control device 45 that adjusts the current ratio between the upper deflection power supply 43 and the lower deflection power supply 44. By doing so, image distortion is reduced. It is to be noted that, instead of shifting the intersection (cross point) of the deflection trajectory by adjusting the operating current ratio, a method of switching coils having different numbers of windings with a relay or the like (providing a plurality of coils having different numbers of windings and using a coil with a control device) Selection method) or, in the case of an electrostatic lens, a method of switching the voltage (a method of varying the used voltage ratio).

  The deflection coil 17 may be arranged in a gap in the upper objective lens 18. The deflection coil 17 may be located in the upper objective lens 18 or may be located further upstream of the charged particle beam as shown in FIG. When employing electrostatic deflection, deflection electrodes are used instead of deflection coils.

(Shield electrode)
In the SEM according to the first embodiment, as shown in FIG. 1, between the potential plate 22 and the sample stage 24, more specifically, the potential plate 22 and the sample 23 Between them, the shield electrode 51 is arranged. When viewed from the sample stage 24 side, the shield electrode 51 and the potential plate 22 are arranged in this order.

  The shield electrode 51 is connected to the potential plate 22 with the insulator 52 interposed therebetween. The shield electrode 51 is fixed above the sample 23 by connection to the potential plate 22 via the insulator 52. Further, since the insulator 52 is an insulator, the shield electrode 51 is electrically insulated from the potential plate 22. In FIG. 1, the insulator 52 is provided at a position near the sample 23 on the potential plate 22. However, since the potential plate 22 has a shape separated from the sample table 24 at a position other than near the sample 23, Of course, the insulator 52 may be provided in a place other than the vicinity of the sample 23 on the potential plate 22, that is, as shown in FIG.

  Further, the shield electrode 51 has an opening. The central axes of the openings of the shield electrode 51 and the potential plate 22 substantially coincide with each other, and the two openings are connected to the primary electron beam 12 and the signal electrons 21 (the secondary electrons 21a and the reflected electrons 21b). Passes. In short, the central axes of the openings of the shield electrode 51 and the potential plate 22 need only coincide with each other so that the passage of the primary electron beam 12 and the signal electrons 21 is not hindered.

  It should be noted here that the shield electrode 51 is electrically connected to the sample stage 24 via the wiring 53, that is, the shield electrode 51 has the same potential as the sample stage 24. Hereinafter, the effect of disposing the shield electrode 51 having the same potential as that of the sample stage 24 will be described.

  First, when retarding, it is effective when it is not desired to apply a strong electric field to the sample 23. In the related art, when a strong electric field is generated on the surface of the sample 23 as a result of a potential difference between the potential plate 22 and the sample stage 24, discharge occurs between the surface of the sample 23 and the potential plate 22. . This discharge may cause deterioration of the characteristics of the sample 23 or damage the sample 23. On the other hand, by disposing the shield electrode 51, a potential difference given between the potential plate 22 and the sample stage 24 can be given between the potential plate 22 and the shield electrode 51. That is, an electric field is generated between the potential plate 22 and the shield electrode 51, and the electric field generated on the surface of the sample 23 can be reduced. This is particularly effective for a sample 23 which has a fine structure such as a semiconductor element and which does not want to generate an electric field.

  Further, when the sample 23 is an insulator, the potential of the retarding voltage cannot be applied to the surface of the sample 23. On the other hand, the arrangement of the shield electrode 51 allows the vicinity of the surface of the sample 23 to be at the same potential as the sample stage 24. Thus, even if the sample 23 is an insulator, the surface of the sample 23 can be set to the potential applied to the sample stage 24.

  Further, an electrostatic lens is formed by a potential difference provided between the potential plate 22 and the sample stage 24. In the case where the surface of the sample 23 has sharpness or unevenness, the shape of the surface of the sample 23 has a slope, or the case where the sample 23 has a cylindrical shape and it is desired to observe the end of the cylinder, the sample 23 is used. Since an electric field is generated on the surface of the lens, the equipotential lines serving as the electrostatic lens are not rotationally symmetric with respect to the optical axis, and the electrostatic lens has large aberration. On the other hand, by disposing the shield electrode 51, the electric field generated on the surface of the sample 23 is reduced, and the electrostatic lens can be made rotationally symmetric with respect to the optical axis.

  Further, it is known that if the irradiation voltage is set to about 1 keV or less, it becomes difficult to charge even an insulator. When the irradiation voltage is set to about 1 keV by retarding, the shield electrode 51 is arranged, and the sample stage 24 and the shield electrode 51 are set to the same potential, so that the insulator can be observed in a state that is difficult to be charged. it can.

  Here, since the magnetic flux density on the optical axis of the lower objective lens 26 has a stronger distribution as it is closer to the sample 23, the lower objective lens 26 is a low aberration lens. When a negative potential is applied to the sample 23, the closer to the sample 23, the stronger the lens becomes, and the lower objective lens 26 becomes a lower aberration lens. The signal electrons 21 are accelerated by an electric field generated by the retarding voltage of the sample 23, and are amplified in energy and enter the detector 20, so that the detector 20 has high sensitivity.

  Further, when a negative potential is applied to the shield electrode 51, the speed of the primary electron beam 12 decreases as it approaches the shield electrode 51. Therefore, the primary electron beam 12 is easily bent by the lower objective lens 26. As the primary electron beam 12 approaches the shield electrode 51, the lower objective lens 26 Become a strong lens. Further, the primary electron beam 12 almost stops decelerating near the shield electrode 51, and slightly decelerates with the sample 23 (when the sample stage 24 and the shield electrode 51 have the same potential).

  The magnetic flux density on the optical axis of the lower objective lens 26 has a stronger distribution as it is closer to the sample 23. A stronger lens is formed between the shield electrode 51 and the sample 23 as the sample is closer to the sample 23, and the width of the strong lens between the shield electrode 51 and the sample 23 is larger than that without the shield electrode 51. It is possible to make a strong lens with a narrow width.

  The potential of the shield electrode 51 may be given a different potential from that of the sample stage 24 by another power source. When a potential at which the secondary electrons 21a do not pass through the shield electrode 51, for example, a potential 200 V lower than the potential of the sample 23 is applied to the shield electrode 51, the signal electrons 21 passing through the shield electrode 51 can be only the reflected electrons 21b. An image using only the backscattered electrons 21b is obtained. Further, the potential plate 22 may be one integrated with the shield electrode 51, a separate one from the shield electrode 51, a single potential plate 22, or a first detector 720 or a second detector 820. Some are attached. Further, various potential plates 22 can be replaced.

(Axis alignment)
In the SEM according to the first embodiment, as shown in FIG. 1, a corrector 54a, a corrector 54b, a corrector 54c, a corrector 54d, a corrector 54e, and a corrector 54f are provided. The correctors 54a to 54f are correctors for adjusting an image with aberration displayed on the display device 57. The correctors 54a to 54d are connected to a corrector power supply 55, and the control device 45 controls the corrector power supply 55. The correctors 54a to 54d may be configured such that the correctors 54b and 54d are alignment deflectors and the correctors 54a and 54c are astigmatism correctors. Alternatively, an astigmatism corrector and an alignment deflector may be arranged in the corrector 54a, and the corrector 54c may be an alignment deflector. The corrector 54e and the corrector 54f are used to align the optical axis of the upper device 71 with the optical axis of the lower objective lens 26, and can be moved using, for example, a screw.

  Furthermore, in order to move the trajectory of the primary electron beam 12 from the optical axis of the upper device 71 to the optical axis of the lower objective lens 26 to accurately align the trajectory, for example, a corrector 54c may be used as an alignment deflector. The display device 57 displays the electric signal output from the detector 20 two-dimensionally in synchronization with the scanning signal. The trajectory of the primary electron beam 12 is deflected by the alignment deflector 54c while viewing the image on the display device 57, and is adjusted to the image with less aberration by adjusting it to the optical axis of the lower objective lens 26. As described above, the alignment deflector can be provided in one stage, but a two-stage alignment deflector may be used for further adjusting the axis. For example, by using the corrector 54b and the corrector 54d as alignment deflectors, it becomes possible to translate or tilt the trajectory, or a combination thereof.

  A wobble method may be used as the axis adjustment method. The wobble method is used to facilitate axis alignment with a function of periodically changing the focal length. The wobble method is a method of adjusting the objective lens diaphragm 16 and the deflector 54 so that the movement of the image becomes isotropic by observing the movement of the image. In the wobble method, it is necessary to increase the scanning speed, and when adjusting at a high magnification, the adjustment may be difficult because the signal amount decreases and the image becomes difficult to see. In order to find the optical axis of the lower objective lens 26 and facilitate astigmatism correction, the lens state of the lower objective lens 26 may be imaged and adjusted.

  The intensity of the lower objective lens 26 is adjusted so that the image of the sample 23 can be seen. Thereafter, the lower objective lens 26 is two-dimensionally scanned and switched to the deflector 17 (54) for generating aberration by the controller 45 for use. For example, the lower objective lens 26 is two-dimensionally scanned only by the upper deflection coil 17a. That is, the deflection fulcrum is set not to be near the main surface of the lower objective lens 26 but to be from the object point of the lower objective lens 26 to a position before the main surface of the lower objective lens 26. In this case, the position of the upper stage deflection coil 17a becomes a deflection fulcrum.

  The display device 57 displays the electric signal output from the detector 20 two-dimensionally in synchronization with the scanning signal. An image having distortion appears on the display device 57. Alignment and astigmatism correction are performed using the correctors 54a to 54f so that the image having aberration displayed on the display device 57 becomes an image having a center-symmetric distortion. For example, coarse adjustment may be performed using the correctors 54e and 54f, and fine adjustment may be performed using the correctors 54a to 54d.

  A specific example will be described. When the correctors 54b and 54d are used as alignment deflectors, the center of the distortion may be moved to the center of the display screen by adjusting the deflection intensity. In the case where the distortion is distorted with respect to the center rather than the object to be rotated, for example, the corrector 54c is used as the astigmatism corrector, and the astigmatism can be corrected to obtain a center-symmetric distortion. The axis may be adjusted by moving the potential plate 22 or the shield electrode 51. When a normal image is viewed (that is, the deflection fulcrum is located near the main surface of the lower objective lens 26), an image in which aberration has been corrected can be obtained.

  As a deflector for generating an aberration for two-dimensionally scanning the lower objective lens 26, for example, using an upper deflection coil 17a and a lower deflection coil 17b, changing the intensity ratio to adjust the deflection fulcrum, 26 may be scanned two-dimensionally. Thus, a distorted image suitable for the magnification can be seen. For example, if the deflection fulcrum is brought closer to the object point of the lower objective lens 26 (crossover point of the condenser lens 15b), a distorted image can be easily viewed at a high magnification. The above method can also be used when the upper objective lens 18 is used as the main lens.

  It is particularly effective when the lower objective lens 26 is mainly used and when the aberration at the time of retarding is adjusted. The axis alignment and the astigmatism correction from the distorted image may be automatically corrected by a program. The two-stage deflection coil 17 and the objective lens diaphragm 16 are used to adjust the center of the distorted image displayed on the display device 57 to the center of the display screen, and then the distortion is corrected using the correctors 54a to 54f. The image should be close to point symmetry.

  Further, in the SEM according to the first embodiment, the wobble method may be used. In the wobble method, the current amount of the lower objective lens 26 may be changed, or the acceleration voltage, the retarding voltage, and the potential plate voltage may be changed. The axis may be adjusted using the two-stage deflection coil 17 using the wobble method.

(Moving mechanism)
The SEM according to the first embodiment includes a moving mechanism for moving the potential plate 22 and the sample stage 24 in the XYZ directions, as shown in FIG. The space on the upper surface side of the lower device 72 of the SEM is surrounded by the vacuum wall 60. Thus, the upper objective lens 18, the secondary electron detector 19, the detector 20, the sample 23, and the like are placed in a vacuum environment. Specifically, the moving mechanism includes a Z-direction stage adjustment unit 56a, a first XY-direction stage adjustment unit 56b, a second XY-direction stage adjustment unit 56c, a potential plate stage 61, and a sample stage stage plate 29. The Z-direction stage adjustment unit 56a, the first XY-direction stage adjustment unit 56b, and the second XY-direction stage adjustment unit 56c are arranged outside the vacuum and operated by the user. The potential plate stage 61 is moved in the XYZ directions by a user operation using the Z-direction stage adjustment unit 56a and the first XY-direction stage adjustment unit 56b. With the movement of the potential plate stage 61, the movement of the potential plate 22 in the XYZ directions is realized. Similarly, the sample stage stage plate 29 is moved in the X and Y directions by a user's operation using the second XY direction stage adjustment unit 56c. With the movement of the XY stage, the movement of the sample stage 24 in the XY directions is realized with the movement of the sample stage stage plate 29.

  Since the shield electrode 51 is connected to the potential plate 22, the user moves the potential plate 22 and the shield electrode 51 in the XYZ directions using the Z-direction stage adjustment unit 56a and the first XY-direction stage adjustment unit 56b. Therefore, the positions of the openings of the potential plate 22 and the shield electrode 51 can be adjusted.

  In addition, by using the moving mechanism as one of the above-described compensators, the potential plate 22 and the shield electrode 51 can be moved to adjust the axis of the electrostatic lens. In this adjustment, the focus of the primary electron beam 12 may be adjusted using the upper objective lens 18, and the position may be adjusted while observing the opening of the shield electrode 51.

  In the case of retarding, the aberration increases due to the distortion of the electrostatic lens due to the retarding, and further, the axial deviation between the electrostatic lens and the magnetic lens also occurs. Regarding the axis shift between the electrostatic lens and the magnetic lens, it is preferable to adjust the axis shift using the potential plate stage 61. As described above, the potential plate stage 61 can be adjusted in height (Z direction) depending on the height of the sample 23 and can be moved in the left-right and front-rear directions (XY directions).

  Regarding an increase in aberration due to distortion of the electrostatic lens, although the electrostatic lens can be made axially symmetrical by the shield electrode 51, it may be slightly displaced from the magnetic lens due to, for example, the inclination of the sample 23. Aberration can be adjusted by fine adjustment using the potential plate stage 61.

  As a method of aligning the center of the opening of the shield electrode 51 with the optical axis, the lower objective lens 26 is turned off and the upper objective lens 18 is used to focus on the shield electrode 51 so that the center of the opening of the shield electrode 51 is displayed. The adjustment may be performed by operating the first XY-direction stage adjustment unit 56b so as to be at the center of the display screen of the device 57. Thus, the axes of the electrostatic lens and the lower objective lens 26 can be aligned. Similarly, the sample 23 may be adjusted by operating the second XY direction stage adjustment unit 56c.

(Gas introduction mechanism)
The SEM according to the first embodiment includes a gas introduction mechanism 58 as shown in FIG. The space between the potential plate 22 and the sample 23 (hereinafter, referred to as “lower space”) and the space from the potential plate 22 to the upper objective lens 18 (hereinafter, referred to as “upper space”) are a potential plate stage. Vacuum separation is performed by using the slide plate 61 and the slide plate 62. The gas introduction mechanism 58 introduces various gases into the lower space, makes the lower space a low vacuum, or causes the gas to stay near the surface of the sample 23.

  For example, when the sample 23 is an insulator, it is usually coated with a conductive material, but sometimes the observation is performed without coating with a conductive material. As a method used in such a case, a method is known in which the sample chamber is set to a low vacuum so that the sample is not charged.

  Therefore, in the SEM of FIG. 1, a gas is introduced into the lower space by using the gas introducing mechanism 58 to make the lower space a low vacuum. Alternatively, the sample 23 may be neutralized by spraying a minute amount of gas or ions introduced using the gas introduction mechanism 58 onto the sample 23.

  On the other hand, by maintaining a high vacuum in the upper space, the scattering rate of the primary electron beam 12 can be reduced, so that performance near high vacuum can be exhibited.

  When the vacuum is set low, a withstand voltage failure between the shield electrode 51 and the potential plate 22 is likely to occur. For this reason, as shown in FIG. 2 to be described later, by providing the insulator 52 at a position further away from the sample table 24, the creepage distance of the insulator 52 is increased, and the withstand voltage of the insulator 52 is increased. It may be.

  Note that, instead of the gas introduction mechanism 58, the inside of the lower space can be made to have a low vacuum by narrowing the exhaust port for exhausting the inside of the lower space.

[Embodiment 2]
The schematic configuration of the SEM according to the second embodiment of the present invention will be described with reference to FIG. Hereinafter, the same parts as those of the first embodiment of the present invention are denoted by the same reference numerals, and the detailed description thereof will be omitted.

  The difference between the SEM of the second embodiment of the present invention and the SEM of the first embodiment of the present invention is that the first detector 720 for detecting the backscattered electrons 21 b and the characteristic X-ray 121 on the lower surface of the potential plate 22. A second detector (electromagnetic wave detector) 820 is provided. Further, as described above, the insulator 52 is provided at a position farther from the sample table 24.

  As the first detector 720, for example, a microchannel plate, a Robinson detector, a semiconductor detector, or the like is used. The first detector 720 and the second detector 820 are configured as a detection unit configured to be combined with each other. The detection unit is, for example, one in which the first detector 720 is arranged in a part of the area viewed from the lower objective lens 26 side, and the second detector 820 is arranged in another area. The detection unit is provided with a hole through which the primary electron beam 12 and the secondary electrons 21a pass. Note that the first detector 720 and the second detector 820 may be separately mounted or only one of them may be attached to the lower surface of the potential plate 22.

  The first detector 720 and the second detector 820 are arranged at a position relatively close to the sample 23. That is, the position where the signal electrons 21 are incident on the first detector 720 and the position where the characteristic X-rays 121 are incident on the second detector 820 are the same from the incident position where the primary electron beam 12 is incident on the sample 23. About a distance apart. Therefore, the solid angles of the reflected electrons 21 b and the characteristic X-rays 121 incident on the first detector 720 and the second detector 820 increase. Therefore, in the first detector 720, the detection sensitivity of the reflected electrons 21b is improved, so that the sample 23 can be observed with higher sensitivity. Further, the EDX analysis can be efficiently performed by the second detector 820 while observing the sample 23 with high resolution. The second detector 820 is arranged so as not to hinder the detection of the backscattered electrons 21b by the first detector 720, and the observation of the sample 23 by detecting the backscattered electrons 21b and the EDX analysis are performed simultaneously. It can be carried out.

  Note that another type of detector may be provided as the second detector 820. Further, the detector 20 may be arranged above the potential plate 22. The size of the hole of the first detector 720 or the second detector 820 may be so small that the primary electron beam 12 passes. For example, the hole is a circular through-hole, and preferably has a diameter of, for example, about 1 to 2 mm. By reducing the hole in this way, most of the reflected electrons 21 b cannot pass above the potential plate 22. Therefore, since most of the signal electrons 21 incident on the secondary electron detector 19 or the detector 20 are the secondary electrons 21a, a clear secondary electron image that is not mixed with the reflected electron image can be obtained.

[Embodiment 3]
FIG. 3 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 3 of the present invention. Hereinafter, the same parts as those in the first and second embodiments of the present invention are denoted by the same reference numerals, and the detailed description thereof will be omitted.

  The difference between the SEM of the third embodiment of the present invention and the SEM of the first embodiment of the present invention is that a second detector (electromagnetic wave detector) 110 for detecting characteristic X-rays 121 emitted from the sample 23 is provided. It is a point.

  As shown in FIG. 3, the space on the upper surface side of the lower device of the SEM is surrounded by a vacuum wall 60. Thereby, the upper objective lens 18, the first detectors 19 and 20, the sample 23, and the like are placed in a vacuum environment. The sample 23 is placed on a sample stage 24 placed on the upper surface of the lower objective lens 26 via an insulating plate 25. The detector 20 that detects the signal electrons 21 is arranged at the lower end of the upper objective lens 18. A secondary electron detector 19 that detects the secondary electrons 21 a is arranged on a side of the upper objective lens 18.

  Here, a second detector 110 that detects the characteristic X-ray 121 emitted from the sample 23 is disposed in the SEM illustrated in FIG. The second detector 110 is an energy dispersive X-ray (EDX (sometimes referred to as EDS)) analyzer. The second detector 110 is mounted as a device accompanying the SEM. In this SEM, the EDX analysis of the sample 23 can be performed along with the observation of the sample 23 by detecting the signal electrons 21. The second detector 110 is arranged so as not to hinder the detection of the signal electrons 21 by the first detectors 19 and 20. The detection of the signal electrons 21 and the detection of the characteristic X-ray 121 are simultaneously performed ( (In parallel), but is not limited to such.

  The second detector 110 has a structure in which the arm 113 extends substantially linearly from the main body disposed outside the vacuum wall 60 to the inside of the vacuum wall 60. The arm 113 is inserted into a vacuum section surrounded by the vacuum wall 60. A plate-like portion 114 formed in a plate shape is provided at the tip of the arm portion 113. The arm portion 113 and the plate portion 114 are made of metal and have conductivity.

  The mount 65 is attached to the vacuum wall 60 using an O-ring or the like so as to maintain airtightness. The second detector 110 is fixed to the mount 65 using a plurality of adjustment bolts 67, nuts, and the like. By adjusting the adjustment bolt 67, the nut, and the like, the fixing position and the like of the mount 65 and the adjustment bolt 67 are adjusted. Thereby, the position of the second detector 110 with respect to the sample 23 can be finely adjusted. A large moving direction of the second detector 110 is a vertical direction (arrow Z direction in the figure; the incident direction of the primary electron beam 12) and a longitudinal direction of the arm 113 (arrow Y direction in the figure). By adjusting the position of the second detector 110 in this manner, the position of the tip of the arm 113, that is, the position of the plate-like portion 114 can be changed. The position of the plate portion 114 with respect to the sample 23, that is, the position of the plate portion 114 with respect to the position through which the primary electron beam 12 passes, can be changed. Accordingly, even when the primary electron beam 12 is focused using the upper objective lens 18, the height adjustment and the front-rear and left-right adjustment can be performed. When not in use, the second detector 110 and the plate-shaped portion 114 can be stored by being largely moved in the longitudinal direction of the arm portion 113 (the direction of the arrow Y in the drawing).

  The plate-shaped portion 114 is disposed so as to be substantially perpendicular to the emission direction of the primary electron beam 12 (hereinafter, sometimes referred to as an optical axis). The plate portion 114 is provided with a hole 114a. The position of the plate portion 114 is adjusted so that the primary electron beam 12 passes through the hole 114a. An X-ray detection unit 120 is disposed on a surface (lower surface in the figure) of the plate-like portion 114 on the sample 23 side. The X-ray detector 120 is, for example, a silicon drift detector (SDD) or a superconducting transition edge sensor (TES). The characteristic X-ray 121 emitted from the sample 23 with the incidence of the primary electron beam 12 is incident on the X-ray detector 120. When the characteristic X-ray 121 is incident on the X-ray detector 120, the second detector 110 detects the incident characteristic X-ray 121.

  The X-ray detection unit 120 may be divided into a part capable of detecting the characteristic X-ray 121 and a part capable of detecting other signal electrons, electromagnetic waves, and the like. An organic thin film, a beryllium thin film, or the like may be disposed on the surface of the X-ray detection unit 120 on the sample side. Thereby, the secondary electrons 21a and the reflected electrons 21b emitted from the sample 23 are stopped without entering the X-ray detection unit 120, and the X-ray detection unit 120 is not affected by the signal electrons 21 and the like. Can be

  The plate portion 114 of the second detector 110 also functions as a potential plate when performing retarding. That is, the retarding power supply 27 is connected to the sample stage 24, and the plate portion 114 is connected to, for example, the ground potential via the arm portion 113. The plate portion 114 functions similarly to the potential plate 22 in the above-described embodiment. Therefore, the same effect as the case where the potential plate 22 is provided can be obtained without separately providing the potential plate 22. Note that the plate-like portion 114 is not limited to the ground potential and may be given a positive potential or a negative potential.

  The position of the plate portion 114 can be appropriately changed as described above. By controlling the upper objective lens 18 and the lower objective lens 26 and controlling the retarding voltage, the sample 23 can be observed with high resolution, as in the above-described embodiment. In addition, EDX analysis of the sample 23 can be performed in accordance therewith, and various analyzes and observations can be performed.

  The second detector 110 is not limited to the one that functions as the potential plate 22 when retarding is performed. The second detector 110 may simply include an X-ray detector that detects the characteristic X-ray 121 and the like.

[Embodiment 4]
FIG. 4 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 4 of the present invention. Hereinafter, the same parts as those in the first, second and third embodiments of the present invention are denoted by the same reference numerals, and the detailed description thereof will be omitted.

  The difference between the SEM of the fourth embodiment of the present invention and the SEM of the first embodiment of the present invention is that a second detector 610 for WDX analysis is provided together with a second detector 210 for EDX analysis. It is.

  The second detector 610 for WDX analysis uses the polycapillary 617, and can perform WDX analysis with higher sensitivity.

  A potential plate 422 used for retarding is provided at the tip of the second detector 210 for EDX analysis. The potential plate 422 is arranged so as to be located near the sample 23 via a potential plate fixing portion 218 attached to the casing of the second detector 210.

  The potential plate 422 has a hole through which the primary electron beam 12, the signal electrons 21 and the like pass, and is arranged so as to be located near the sample 23. The hole is arranged at a position where the characteristic X-ray 121 emitted from the sample 23 enters the collimator 214 and the X-ray transmission window 220a of the second detector 210. An insulating plate 25, a sample stage 24, an insulating material 31, and the like are arranged above the lower objective lens 26. The sample stage 24 is connected to the retarding power supply 27, and the potential plate 422 is connected to the potential plate power supply 28. With this configuration, retarding is performed in this SEM in the same manner as in the first embodiment.

  As described above, in the apparatus shown in FIG. 4, since each of the second detectors 210 and 610 can be brought close to the sample 23, the sample 23 can be sampled with high resolution while increasing the detection efficiency of the EDX analysis and the WDX analysis. Can be observed. Further, the effect of the retarding is obtained, the irradiation electron energy can be reduced, and the depth of electrons of the primary electron beam 12 entering the sample 23 can be reduced. This enables high-resolution observation of the surface shape of the sample. Furthermore, since the aberration can be reduced by bringing the potential plate 422 closer to the sample 23, a high-resolution and low-acceleration SEM can be realized.

  In the SEM shown in FIG. 4, the positions of members and the like constituting the second detector 210 for EDX analysis and the second detector 610 for WDX analysis can be finely adjusted. The potential plate 422 may be independently movable without being connected to the second detector 210 for EDX analysis.

  Note that the potential plate 422 may be attached to the second detector 610 for WDX analysis. For example, a potential plate 422 may be attached near the tip of the polycapillary 617. Further, the potential plate 422 may be independently movable without being connected to the polycapillary 617.

  Here, when electrons or X-rays hit the potential plate 422, fluorescent X-rays are emitted. Then, when performing the EDX analysis or the WDX analysis, the X-rays emitted from the sample 23 and the X-rays emitted from the potential plate 422 are analyzed together. In order to reduce the influence of the X-rays emitted from the potential plate 422 on the analysis result, the potential plate 422 is a light element thin film (for example, a beryllium thin film, an organic thin film, a silicon nitride thin film, etc.). (Not limited). When the potential plate 422 is formed of a thin film of a light element, X-rays easily pass through the potential plate 422. Note that, when the potential plate 422 is formed of a thin film of a light element, X-rays can easily pass through the potential plate 422 and enter the detector even when the hole of the potential plate 422 is small.

  Further, in order to reduce the influence of the X-rays emitted from the potential plate 422 on the analysis result, for example, a material having a composition having a different detection peak from the sample 23 to be analyzed is used as the material of the potential plate 422. Is also good. This makes it easier to remove the influence of the potential plate 422 on the analysis result.

[Embodiment 5]
FIG. 5 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 5 of the present invention. Hereinafter, the same parts as those in the first, second, third and fourth embodiments of the present invention are denoted by the same reference numerals, and the detailed description thereof will be omitted.

  The difference between the SEM of the fifth embodiment of the present invention and the SEM of the first embodiment of the present invention is that a second detector 410 for detecting a cathode luminescence (CL) 321 is provided.

  The second detector 410 has a parabolic mirror (an example of an optical element) 420, a detector main body 310a, and an optical lens 411. The mirror surface 420b of the parabolic mirror 420 has a curved shape whose focal point is the point where the CL 321 is emitted from the sample 23. The CL 321 that has entered the mirror surface 420 b becomes parallel light and enters the optical lens 411. The CL 321 is refracted and condensed by the optical lens 411 and enters the detector main body 310a. Thus, the CL 321 is efficiently detected by the detector main body 310a.

  Below the parabolic mirror 420, a potential plate 422, which is a conductive plate, is attached. The potential plate 422 has a hole through which the primary electron beam 12, the signal electrons 21 and the like pass, and is arranged so as to be located near the sample 23. An insulating plate 25, a sample stage 24, an insulating material 31, and the like are arranged above the lower objective lens 26. The sample stage 24 is connected to the retarding power supply 27, and the potential plate 422 is connected to the potential plate power supply 28. With this configuration, retarding is performed in this SEM in the same manner as in the first embodiment.

  The size of the hole provided in the parabolic mirror 420 through which the primary electron beam 12 and the like pass is set as appropriate. That is, if the hole is relatively small, the amount of the reflected electrons 21b passing therethrough decreases, but the amount of light of the CL 321 increases. On the other hand, if the hole is relatively large, the amount of light of the CL 321 decreases, but the amount of the reflected electrons 21b passes increases. Note that the parabolic mirror 420 may be an elliptical mirror to detect the CL 321. In addition, a reflection mirror may be arranged in place of the parabolic mirror 420, and an optical microscope and a fluorescence microscope may be attached to the positions of the optical lens 411 and the detector main body 310a so that observation is possible. The image obtained by the secondary electron detector 19 and the semiconductor detector 20 and the image obtained by the second detector 410 may be simultaneously observed. Further, the image from the signal electronics 21 and the image from the second detector 410 may be displayed in a superimposed manner.

[Embodiment 6]
FIG. 6 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 6 of the present invention. Hereinafter, the same parts as those in Embodiments 1 to 5 of the present invention are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The SEM of the sixth embodiment of the present invention is different from the SEM of the first embodiment of the present invention in that an open case 700 is provided instead of the shield electrode 51, the insulator 52, and the wiring 53.

  The open case 700 is arranged on the sample stage 24 so as to cover the sample 23. In the open case 700, the upper surface 701 has the same function as the shield electrode 51, and the side surface 702 has the same function as the wiring 53. Specifically, the upper surface 701 is electrically connected to the sample stage 24 via the side surface 702. Thus, the upper surface 701 has the same potential as the sample stage 24.

  The open case 700 may be fixed to the sample stage 24 using a fastener or the like. In addition, the upper part and the lower part may be separable so that the height can be easily adjusted outside the SEM. If it is arranged on the sample stage 24 after the adjustment, the distance between the sample 23 and the upper surface 701 can be easily adjusted.

  For example, the upper surface 701 is a non-magnetic material and has conductivity. The end of the side surface portion 702 in contact with the sample stage 24 is a tip of a set screw. The height can be adjusted by turning the set screw. Since the conductive set screw is in contact with the sample stage 24, the upper surface 701 has the same potential as the sample stage 24.

  The upper surface 701 is arranged so as to cover the sample 23, and has an opening at a portion where the primary electron beam 12 scans. When a retarding voltage is applied to the sample stage 24, a potential difference is generated between the sample stage 24 and the potential plate 22. In the case of the sharp sample 23, when there is no upper surface portion 701, a discharge is easily generated between the sample 23 and the potential plate 22. Discharge can be prevented by covering the sharpness of the sample 23 with the upper surface portion 701.

  If the sample 23 has unevenness, the electrostatic lens may be disturbed by the unevenness if the upper surface 701 is not provided, and high resolution may not be obtained. By attaching the upper surface portion 701, the potential is stabilized and the electrostatic lens can be prevented from being disturbed.

  It should be noted that the SEM of the sixth embodiment of the present invention is different from the SEM of the first embodiment of the present invention in that the SEM includes an insulating portion 710 in which the insulating plate 25 and the insulating material 31 are integrated. It is.

[Embodiment 7]
FIG. 7 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 7 of the present invention. Hereinafter, the same parts as those in Embodiments 1 to 6 of the present invention are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The difference between the SEM of the seventh embodiment of the present invention and the SEM of the first embodiment of the present invention is that a sealed case 800 is provided instead of the shield electrode 51, the insulator 52, and the wiring 53.

  The closed case 800 is different from the open case 700 in that the sample 23 is stored. The inside of the closed case 800 is a closed space. The sealed case 800 has an upper surface portion 801 having the same function as the shield electrode 51, and a side surface portion 802 having the same function as the wiring 53. Specifically, the upper surface portion 801 is electrically connected to the sample stage 24 via the side surface portion 802. Thus, the upper surface 801 has the same potential as the sample stage 24.

  By providing an opening in the upper surface 801 and closing the opening with the conductive thin film 803, a sealed space is realized inside the sealed case 800. By variously selecting the conductive thin film 803, primary electrons, reflected electrons, electromagnetic waves, and the like are transmitted through the conductive thin film 803. Further, since the opening is flat, even if the sample stage 24 is moved, the shape of the electrostatic lens composed of the potential plate 22 and the sample stage 24 does not change. As a result, the potential plate 22 and the upper surface 801 Is unnecessary.

  Gas or liquid can be introduced into the sealed case 800 due to its sealing property. For this reason, it is possible to handle the sample 23 that cannot be observed in a high vacuum, such as a liquid, an organism, a cell, and the like.

  The closed case 800 may be fixed to the sample stand 24 using fasteners or the like, similarly to the open case 700. In addition, the upper part and the lower part may be separable so that the height can be easily adjusted outside the SEM. If it is arranged on the sample stage 24 after the adjustment, the distance between the sample 23 and the upper surface 801 can be easily adjusted.

  It is preferable that the conductive thin film 803 and the upper surface 801 be as flush as possible. Thus, even when the sample table 24 is moved, the electric field between the sample table 24 and the potential plate can be prevented from being disturbed. The conductive thin film 803 has a thickness of about 30 nm to 1 μm, and may be an organic thin film, a carbon thin film, a metal thin film, SiN, SiC, polyimide, graphene, silicon oxide, or the like. Since the conductive thin film 803 is thin, it can transmit electromagnetic waves such as light and X-rays. Therefore, as shown in FIGS. 3, 4 and 5, the first detectors 19 and 20 and the second detectors 110, 210, 610 and 410 are similarly arranged, and the signal electrons 21 and the electromagnetic waves 121 and 321 and the light Can be detected simultaneously.

  The closed case 800 can store a sample that evaporates and deforms its shape when evacuated. For example, it is suitable for living organisms and samples in liquids. A stand for height adjustment may be placed in the closed case 800 so that the sample in the liquid is in contact with the conductive thin film 803. It may be installed so that gas is present between the conductive thin film 803 and the sample 23. The gas may be air, helium, hydrogen, nitrogen, argon, or the like. The pressure may be atmospheric or reduced. The sealed case 800 prevents leakage of gas with an O-ring or the like.

  An exhaust port may be provided in the sealed case 800, or the outside air may be depressurized and sealed when the lid is closed. The gas may be sealed and sealed.

  It should be noted that, unlike the SEM of the first embodiment of the present invention, the SEM of the seventh embodiment of the present invention also includes an insulating portion 810 in which the insulating plate 25 and the insulating material 31 are integrated. It is. However, it should be noted that, unlike the SEM according to the sixth embodiment of the present invention, a portion corresponding to the insulating plate 25 extends toward the outside of the device as in the first embodiment of the present invention. Thereby, the withstand voltage of the sample stage 24 is improved.

[Embodiment 8]
FIG. 8 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 8 of the present invention. Hereinafter, the same parts as those in Embodiments 1 to 7 of the present invention are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The difference between the SEM of the eighth embodiment of the present invention and the SEM of the first embodiment of the present invention is that the sample 23 is placed on the potential plate 22 instead of being placed on the sample stage 24. is there. That is, the SEM according to the eighth embodiment of the present invention uses the potential plate 22 as a sample stage on which the sample 23 is placed.

  As shown in FIG. 8, the sample 23 is mounted on a sample pedestal 904 arranged on the potential plate 22. A magnetic pole (for example, a ground potential or a potential) 18 d of the upper objective lens 18 has the same function as the potential plate 22. The shield electrode 900 is electrically connected via a wiring 903 to the potential plate 22 as a sample stage. With this connection, the shield electrode 900 and the potential plate 22 have the same potential.

  The sample pedestal 904 is for adjusting the distance between the sample 23 and the shield electrode 900. By adjusting the height of the sample pedestal 904, the distance between the sample 23 and the shield electrode 900 can be adjusted.

  The shield electrode 900 is connected to a shield electrode moving mechanism 901 that moves the shield electrode 900 in the XYZ directions. Since the shield electrode moving mechanism 901 has the same function as the moving mechanism of the first embodiment, the description is omitted here.

  In the SEM shown in FIG. 8, a snorkel lens is used as the upper objective lens 18. The signal electrons 21 travel through the upper objective lens 18 and are detected by a detector arranged in or on the upper objective lens 18.

  It can be understood that the present invention can be easily applied to a charged particle beam apparatus such as an EPMA, an electron beam welding machine, an electron beam drawing apparatus, and an ion beam microscope. For example, the lower objective lens 26 can be used as an objective lens of a mirror electron microscope which is a kind of a charged particle beam device. A negative potential slightly larger than the accelerating voltage of the primary electron beam 12 is applied to the sample 23, and the primary electron beam 12 is reflected without being applied to the sample 23. In this case, the signal electrons 21 are reflected from the primary electron beam 12. It is possible to obtain information on minute irregularities and potential distribution on the sample surface. Further, a shield electrode 51 having a moving mechanism may be arranged so that the position can be adjusted. A potential may be applied to the shield electrode 51 so that the potential difference from the sample 23 can be adjusted.

[Embodiment 9]
FIG. 9 is a cross-sectional view illustrating a schematic example of an SEM device configuration according to Embodiment 9 of the present invention. Hereinafter, the same parts as those in Embodiments 1 to 7 of the present invention are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The SEM of the ninth embodiment of the present invention is different from the SEM of the first embodiment of the present invention in that a second detector 210 for EDX analysis and a second detector 610 for WDX analysis are provided. is there. The second detector 210 for EDX analysis and the second detector 610 for WDX analysis are the same as those in the fourth embodiment of the present invention, and therefore will not be described here.

  Note that FIG. 9 does not show the potential plate 22 and the shield electrode 51 shown in FIG. 1 and the like. However, it goes without saying that the SEM shown in FIG. 9 may be provided with the potential plate 22 and the shield electrode 51 shown in FIG. 1 and the like.

  The difference between the SEM of the ninth embodiment of the present invention and the SEM of the first embodiment of the present invention is that a scanning probe microscope (hereinafter, referred to as “SPM”) 500 and a manipulator 504 are provided. It is a point.

  First, the configuration and functions of the SPM 500 will be described.

  The SPM 500 is disposed between the upper device 71 and the lower objective lens 26. Further, the SPM 500 may be arranged on the potential plate stage 61 shown in FIG. Further, the SPM 500 may be disposed above the lower objective lens 26.

  The SPM 500 includes a cantilever (leaf spring) 501, an SPM detector 502, and an SPM laser 503. A probe (SPM probe) 501a is provided at the tip of the cantilever 501. The SPM 500 detects a change in a force applied between the probe 501a and the sample 23 as the amount of change in deflection or vibration of the cantilever 501. The detection of the amount of change is performed by the SPM detector 502 detecting a laser beam emitted from the SPM laser 503. The SPM 500, the sample 23, or the sample stage 24 is provided with a piezoelectric element that can expand and contract in each of the XYZ directions. The SPM 500, the sample 23, or the sample stage 24 can be moved in the XYZ directions by the piezoelectric element.

  Also, a three-dimensional image using a method of synthesizing a depth of focus (a method in which a plurality of images are taken while automatically moving the focal position and an image is synthesized to obtain an image with a large depth of field) is obtained. While obtaining, the probe 501a of the cantilever 501 may be operated.

  The moving range of the SPM 500 is narrow. For this reason, only observation using the SPM 500 is expected to require a considerable amount of time to search for a target measurement position over a wide range on the sample 23. In the SEM of the present embodiment, the SEM image of the sample 23 can be observed in a wide range in real time, so that the measurement position of the SPM 500 can be quickly found. Then, the probe 501a at the tip of the cantilever 501 can be reliably set at the target measurement position by the second XY-direction stage adjusting section 56c or the piezoelectric element.

  When the sample 23 is observed using only the upper objective lens 18, it is necessary to bring the upper objective lens 18 and the sample 23 closer. For this reason, it is expected that it will be difficult to dispose an optical system (here, the SPM detector 502 and the SPM laser 503) for detecting the amount of deflection or vibration change of the cantilever 501 directly below the upper objective lens 18. Is done.

  In addition, if a self-sensing cantilever having a strain resistance is used, the above-described optical system becomes unnecessary, but in order to operate the cantilever 501, a cantilever portion is placed between the upper objective lens 18 and the sample 23 in the first place. It is necessary to enter.

  Thus, when only the upper objective lens 18 is used, it is necessary to observe the sample 23 by separating the sample 23 from the upper objective lens 18 (by increasing the working distance). Increasing the working distance decreases the resolution of the SEM. In the SEM of this embodiment, by using the lower objective lens 26 in addition to the upper objective lens 18, if the thickness of the sample 23 is about 5 mm or less, the SPM 500 is observed while observing the sample 23 with high resolution. It can be used to measure and manipulate the sample 23.

  Further, when the sample 23 is observed at a low magnification, the primary electron beam 12 may be focused using the upper objective lens 18. It is also possible to optimize the opening angle α of the primary electron beam 12 using the upper objective lens 18 and the lower objective lens 26. As a matter of course, even if the working distance is increased, a decrease in the resolution of the SEM can be avoided, so that the above-described optical system can be easily arranged directly below the upper objective lens 18.

  Next, measurement of the sample 23 and operation of the sample 23 using the manipulator 504 will be described.

  First, the measurement of the sample 23 will be described.

  Although only one manipulator 504 is shown in FIG. 9, the SEM of the present embodiment may include a plurality of manipulators 504.

  By bringing the probe 504a of the manipulator 504 into contact with the sample 23, the electrical characteristics of the sample 23 can be measured. The measurable electrical properties include, for example, the resistance value of the sample 23, the conductivity of the sample 23, the current value flowing through the sample 23, the applied voltage applied to the sample 23, the insulation property of the sample 23, and the sheet resistance of the sample 23. No.

  Further, by using the manipulator 504, a current flowing when the sample 23 is irradiated with an electron beam, that is, an electron beam excitation current (EBIC) can be measured. In the SEM of this embodiment, it is also possible to image the internal structure of the sample 23 based on the measured electron beam excitation current. This makes it possible to visualize a pn junction formed inside the sample 23 and to observe a crystal defect of the sample 23.

  Furthermore, it is also possible to measure the local resistance of the sample 23 by measuring the absorption current (electron beam absorption current (EBAC)) flowing between the electron beam and the probe 504a of the manipulator 504.

  Next, the operation of the sample 23 will be described.

  The sample 23 can be operated by bringing the probe 504 a of the manipulator 504 into contact with the sample 23. A variety of shapes of the probe 504a are prepared, and a part of the sample 23 can be operated and processed (cut, peeled, pierced, moved, joined). For example, using the probe 504a, a part of the sample 23 can be grasped, moved, and joined to another position of the sample 23. Further, the tensile measurement and the stress measurement of the sample 23 can be performed.

  A mechanism for supplying gas or liquid to the manipulator 504 may be provided. By supplying gas or liquid supplied from the mechanism to the sample 23 from the probe 504a, a thin film is deposited on the surface of the sample 23, marking is performed on the surface of the sample 23, etching is performed on the surface of the sample 23, Can cause a chemical reaction on the surface of the surface.

  Further, by providing a heating mechanism and a cutter capable of high-frequency vibration to the probe 504a, variations in experiments performed using the sample 23 can be increased.

  When retarding, it is preferable to insulate the probe 504a from the manipulator 504.

  As shown in FIG. 9, the SEM of this embodiment further includes a heating laser 601, a focused ion beam (FIB) 602, a physical vapor deposition device (PVD) 603, and an optical camera 604.

  The heating laser 601 irradiates the sample 23 with laser light, thereby heating the sample 23 and sublimating and evaporating a part of the sample 23. In the SEM according to the present embodiment, a change in the state of the sample 23 due to laser beam irradiation can be observed in real time and with high resolution. The heating laser 601 may be arranged at the position of the polycapillary 617 shown in FIG. Further, the heating laser 601 can be used in a retarded state. Further, the emission port of the heating laser 601 is preferably arranged between the upper device 71 and the lower objective lens 26.

  The focused ion beam 602 cuts and processes the sample 23 by irradiating the sample 23 with finely focused ions. In the SEM of this embodiment, the sample 23 can be cut and processed using the focused ion beam 602. When the lower objective lens 26 is used, the lens barrel of the focused ion beam 602 can be arranged near the sample 23 without causing interference with the upper objective lens 18.

  The physical vapor deposition device 603 vapor-deposits a thin film such as a metal on the surface of the sample 23. In the SEM of the present embodiment, a change in the state of the sample 23 due to thin film deposition can be observed in real time and with high resolution.

  In the SEM of this embodiment, it is also possible to confirm the positions of the cantilever 501 and the manipulator 504 using the optical camera 604.

  The present invention is not limited to the above embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  For example, the potential plate 22 may be removed from the SEM. The potential plate 22 or the shield electrode 51 is attached to the SEM as needed. The potential plate 22 or the shield electrode 51 can be attached to and detached from the SEM. Even when retarding is performed, the potential plate 22 and the shield electrode 51 may be removed. In the case of attaching them, the holes of the potential plate 22 and the shield electrode 51 may be arranged so as to be located above the probe 504a or the cantilever 501 of the manipulator 504.

  The shapes of the potential plate 22 and the shield electrode 51 need only be rotationally symmetric with respect to the optical axis of the primary electron beam 12, and are not limited to plate shapes. For example, it may have a ring shape or a conical shape having a downward convex shape and a hole at the tip. The arrangement of the potential plate 22 and the shield electrode 51 above the sample is determined so that a space for processing the sample 23 is secured.

  The sample 23 is preferably separated from the upper device 71 by 20 mm or more, preferably 30 mm or more, more preferably 40 mm or more.

  When the sample 23 is observed at a low magnification, it is preferable that the primary electron beam 12 be focused using the upper objective lens 18. On the other hand, when observing the sample 23 with high magnification and high resolution, it is preferable to use the lower objective lens 26. Further, it is preferable to use the upper objective lens 18 and the lower objective lens 26 at the same time and optimize the opening angle α of the SEM.

  A charged particle beam device according to one embodiment of the present invention mounts a charged particle source that emits a charged particle beam, an objective lens that focuses the charged particle beam emitted from the charged particle source on a sample, and the sample. A sample stage and a shield electrode and a potential plate for passing the charged particle beam are provided.From the sample stage side, the shield electrode and the potential plate are arranged in this order, and the sample stage and the potential plate A potential difference is applied between the electrodes, and a potential is applied to the shield electrode to reduce an electric field generated in the sample due to the potential difference.

  It is preferable to include a moving mechanism for moving the shield electrode and the potential plate.

  It is preferable that the objective lens includes a lower objective lens arranged on a side opposite to a side where the charged particle beam is incident on the sample.

  The objective lens includes an upper objective lens arranged on a side where the charged particle beam is incident on the sample, an upper objective lens power supply that varies the intensity of the upper objective lens, and an intensity of the lower objective lens. With a variable lower objective lens power supply, when using only the upper objective lens power supply, the sample is disposed between the upper objective lens and the lower objective lens, when using only the lower objective lens power supply, It is preferable that the distance between the lower objective lens and the measurement sample surface is shorter than the distance between the upper objective lens and the measurement sample surface.

  The shield electrode is connected to the potential plate so as to sandwich an insulator. The shield electrode and the potential plate each have an opening through which the charged particle beam passes, and the central axes of the openings are substantially the same. It is preferable that they match.

  It is preferable that a gas introduction mechanism is provided for introducing the gas into the space including the potential plate and the sample stage so that the gas stays near the sample.

  It is preferable that a detector is provided on a surface of the potential plate facing the shield electrode so as not to block an opening of the potential plate, and a detector for detecting signal electrons or electromagnetic waves emitted from the sample is provided.

  It is preferable that the shield electrode is connected to the sample stage so as to sandwich a conductor, and has the same potential as the sample stage via the conductor.

  It is preferable that the shield electrode and the conductor constitute a sample case mounted on the sample stage so as to cover the sample.

  The sample case is an airtight container, and a thin film member is provided so as to cover the opening of the shield electrode. The thin film member passes through the charged particle beam and signal electrons or electromagnetic waves emitted from the sample. It is preferable to be composed of a material to be made.

  Preferably, the potential plate is a magnetic pole of the upper objective lens facing the shield electrode.

  A charged particle beam device according to one embodiment of the present invention is a charged particle beam source that emits a charged particle beam, and is arranged on a side opposite to a side where the charged particle beam is incident on a sample, and is emitted from the charged particle source. A lower objective lens for focusing the charged particle beam on the sample, a sample stage on which the sample is mounted, a shield electrode and a potential plate for passing the charged particle beam, and a moving mechanism for moving the shield electrode and the potential plate And a gas introduction mechanism for introducing the gas into the space including the potential plate and the sample stage to cause the gas to stay in the vicinity of the sample, and the shield electrode and the potential plate are arranged from the sample stage side. , Are arranged in this order.

  The arrangement configuration of the upper part of the sample is determined so that a space for performing processing on the sample is secured on the upper part of the lower objective lens, including at least one of operation, processing, and measurement on the sample. Is preferably performed.

  A scanning electron microscope according to one embodiment of the present invention includes the above charged particle beam device.

  Reference Signs List 11 electron source (charged particle source), 12 primary electron beam (charged particle beam), 13 Wehnelt electrode, 14 acceleration power supply, 14d anode plate, 15 condenser lens, 16 objective lens aperture, 17 two-stage deflection coil, 17a upper stage deflection coil , 17b lower deflection coil, 18 upper objective lens, 18b outer magnetic pole, 18c hole, 18d magnetic pole, 19 secondary electron detector (first detector), 20 detector (first detector) (semiconductor detector , MCP detector or Robinson detector), 21 signal electrons, 21a secondary electrons, 21b backscattered electrons, 22, 422 potential plate, 23 sample, 24 sample stage, 25 insulating plate, 26 lower objective lens, 26a central magnetic pole, 26b Upper magnetic pole, 26c Side magnetic pole, 26d Lower magnetic pole, 26e Coil part, 26f Seal part, 27 retarding Source, 28 potential plate power supply, 29 sample stage stage plate, 31 insulating material, 41 upper objective lens power supply, 42 lower objective lens power supply, 43 upper stage deflection power supply, 44 lower stage deflection power supply, 45 controller, 51, 900 shield electrode, 52 Insulator, 53, 903 wiring, 54a, 54b, 54c, 54d, 54e, 54f Corrector, 55 Corrector power supply, 56a Z-direction stage adjuster, 56b First XY-direction stage adjuster, 56c Second XY-direction stage adjuster, 57 display device, 58 gas introduction mechanism, 60 vacuum wall, 61 potential plate stage, 62 slide plate, 65 mount portion, 67 adjustment bolt, 71 upper device, 72 lower device, 110, 210, 410, 610, 820 second Detector (electromagnetic wave detector), 113 arm, 114 plate, 114a hole, 20 X-ray detection unit, 121 characteristic X-ray, 214 collimator, 218 potential plate fixing unit, 220 X-ray detection element, 220a X-ray transmission window, 310a detector body, 321 CL, 411 optical lens, 420 parabolic mirror, 420b Mirror surface, 500 SPM, 501 cantilever, 501a probe (SPM probe), 502 SPM detector, 503 SPM laser, 504 manipulator, 504a probe, 601 heating laser, 602 focused ion beam, 603 physical vapor deposition device , 604 optical camera, 617 polycapillary, 700 open case, 701, 801 top, 702, 802 side, 710, 810 insulating, 720 First detector (semiconductor detector, MCP) provided on potential plate Detector or Robinson detector), 800 sealed case , 803 conductive thin film, 901 shield electrode moving mechanism, 904 sample base

Claims (6)

A charged particle source for emitting a charged particle beam;
A lower objective lens for focusing the charged particle beam emitted from the charged particle source on a sample,
With
The lower objective lens is disposed on a side opposite to a side where the charged particle beam is incident on the sample,
The arrangement configuration of the upper part of the sample is determined so that a space for performing processing on the sample is secured on the upper part of the lower objective lens, including at least one of operation, processing, and measurement on the sample. A charged particle beam device characterized by being performed.   The charged particle beam apparatus according to claim 1, further comprising an upper objective lens arranged on a side where the charged particle beam is incident on the sample.   3. The charged particle beam apparatus according to claim 1, further comprising a scanning probe microscope for performing an operation or measurement on the sample.   The charged particle beam device according to any one of claims 1 to 3, further comprising a manipulator for performing operation, processing, or measurement on the sample.   The charged particle beam apparatus according to any one of claims 1 to 4, further comprising a vapor deposition device that performs vapor deposition on the sample.   The charged particle beam apparatus according to any one of claims 1 to 5, further comprising a focused ion beam for performing operation, processing, or measurement on the sample.

Images