JP6591681B2 - Charged particle beam apparatus and scanning electron microscope - Google Patents

Description

  The present invention relates to a charged particle beam apparatus and a scanning electron microscope.

  As a charged particle beam apparatus, a scanning electron microscope (hereinafter abbreviated as “SEM”), an EPMA (Electron Probe Micro Analyzer), an electron beam welding machine, an electron beam drawing apparatus, an ion beam microscope, and the like are conventionally used. Known as technology.

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

  As such a technique, there is a retarding technique for generating an electric field for decelerating a primary electron beam between a sample and an objective lens. 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 at low incident energy.

Japanese Patent Publication “JP 9-171791 A” (published on June 30, 1997) Japanese Patent Publication “JP 2000-133194 A (published on May 12, 2000)” Japanese Patent Publication “JP-A-8-68772” (published March 12, 1996)

  When the retarding technique is used, a potential plate is arranged in the 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 there is a sharp point on the surface of the sample on the potential plate side, a strong electric field is generated around the sharp point, causing a problem that discharge occurs between the potential plate and the sample. is there.

  For example, when a retarding voltage is applied in a state where dust or the like is attached 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 surface of the sample is, and the greater the potential difference is, the greater the concentration of electric field generated around the sharpness, and the above problem becomes more serious. It becomes impossible to increase the potential difference between the potential plate and the sample, and it becomes difficult to realize the retarding technique.

  In addition, there is a problem that sample characteristics are deteriorated due to electric field concentration on the sample surface. Further, there is a problem that the trajectory of the primary electron beam emitted from the electron gun is bent.

  For example, 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 is uneven, (2) the sample surface is inclined and the sample is an insulator. Even if the electric field distribution generated between the electric potential plate and the potential plate is not parallel to the sample stage, there is a problem that may occur in the same manner.

  The present invention has been made in view of the above problems, and its object is to reduce the electric field generated on the sample surface for various samples in charged particle beam devices and scanning electron microscopes using a retarding technique. An object of the present invention is to realize a charged particle beam apparatus and a scanning electron microscope excellent in the effectiveness of the retarding technique.

  Another object of the present invention is to freely arrange a potential plate and a shield electrode in a charged particle beam apparatus and a scanning electron microscope each having a lower objective lens disposed in a space opposite to an electron gun when viewed from a sample. By realizing a possible configuration, it is to realize a charged particle beam apparatus and a scanning electron microscope with high resolution.

  In order to solve the above problems, a charged particle beam apparatus according to one embodiment of the present invention includes a charged particle source that emits a charged particle beam, and an objective that focuses the charged particle beam emitted from the charged particle source onto a sample. A lens, a sample stage on which the sample is placed, and a shield electrode and a potential plate that allow the charged particle beam to pass through. From the sample stage side, the shield electrode and the potential plate are arranged in this order. A potential difference is applied between the sample stage and the potential plate, and a potential that relaxes the electric field generated in the sample due to the potential difference is applied to the shield electrode.

  According to one aspect of the present invention, in charged particle beam apparatuses and scanning electron microscopes that use a retarding technique, charged particles that reduce the electric field generated on the sample surface for various samples and are excellent in the effectiveness of the retarding technique. A line device and a scanning electron microscope can be realized.

  Further, according to one aspect of the present invention, in a charged particle beam apparatus and a scanning electron microscope having a lower objective lens disposed on the opposite side of the electron gun as viewed from the sample, the potential plate and the shield electrode can be freely set. By realizing a configuration that can be arranged, a high-resolution charged particle beam apparatus and a scanning electron microscope can be realized.

It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 1 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 2 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 3 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 4 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 5 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 6 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 7 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 8 of this invention. It is a schematic sectional drawing explaining the structure of SEM concerning Embodiment 9 of this invention.

  Embodiments 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 idea of the present invention does not specify the material, shape, structure, arrangement, etc. of the component parts as follows. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

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

(Basic configuration of SEM)
This SEM includes an electron source (charged particle source) 11, an acceleration power source 14, a condenser lens 15, an objective lens diaphragm 16, a two-stage deflection coil 17, an upper objective lens 18, a lower objective lens 26, and a detection. An electron beam apparatus provided with a vessel 20. The acceleration power source 14 accelerates a 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 stop 16 removes unnecessary portions of the primary electron beam 12. The two-stage deflection coil 17 scans the primary electron beam 12 on the sample 23 two-dimensionally. 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 the signal electrons 21 (secondary electrons 21a and reflected electrons 21b) emitted from the sample 23.

  The SEM includes an upper objective lens power source 41, a lower objective lens power source 42, and a control device 45 as an electromagnetic lens control unit including the upper objective lens 18 and the lower objective lens 26. The upper objective lens power supply 41 varies the intensity of the upper objective lens 18. The lower objective lens power source 42 varies the intensity of the lower objective lens 26. The control device 45 controls the upper objective lens power source 41 and the lower objective lens power source 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 for 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 14d (ground potential). A negative potential is applied to the Wehnelt electrode 13 more 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. A crossover diameter that is the first minimum diameter of the primary electron beam 12 is formed immediately in front of the electron source 11. This minimum diameter is called the electron source size So.

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

  The primary electron beam 12 that has passed through the objective lens stop 16 passes through the upper objective lens 18 after passing through the scanning two-stage deflection coil 17. The general-purpose SEM uses the upper objective lens 18 to focus the primary electron beam 12 on the sample 23. The SEM of FIG. 1 can be used in this way.

  In FIG. 1, the configuration from the electron source 11 to the upper objective lens 18 constitutes an upper device 71 that emits the primary electron beam 12 toward the sample 23. Further, the lower device 72 is configured by the potential plate 22 and members disposed below the potential plate 22. The sample 23 is held in the lower device 72. The upper device 71 has a hole 18c through which the primary electron beam 12 passing through the upper device 71 is finally emitted. In the first embodiment, the hole 18 c exists in the upper objective lens 18. The detector 20 is attached 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 so that the opening of the detector 20 and the hole 18c overlap. A plurality of detectors 20 may be attached to the lower part of the upper objective lens 18. The plurality of detectors 20 do not block the trajectory of the primary electron beam 12, and the detection unit of the detector 20 has no gap as much as possible except for the hole 18 c of the upper device 71, so that the upper device 71 and the lower device 20 It is 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 to control the opening angle α and adjust the reduction ratio, lens shape, and depth of focus so that an easy-to-view image is obtained. That is, the upper objective lens 18 is used to optimize each of these control values. Further, when the primary electron beam 12 cannot be focused only by the lower objective lens 26, assistance for focusing the primary electron beam 12 by the upper objective lens 18 can be performed.

  When the retarding is not performed, the potential plate 22 may be removed. Further, the potential plate 22 can be removed, and can be replaced with a new potential plate 22. The sample 23 is preferably installed as close to the lower objective lens 26 as possible. More specifically, the sample 23 is preferably placed 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 the sample 23 with energy accelerated by the acceleration power source 14. At that time, the secondary electrons 21 a are wound around the magnetic flux by the magnetic field of the lower objective lens 26 and rise while making a spiral motion. When the secondary electrons 21a move away from the surface of the sample 23, the magnetic flux density rapidly decreases, so that the secondary electrons 21a are unwound from the turn and diverge. The secondary electrons 21a are deflected by the drawn electric field from the secondary electron detector 19 to be secondary electron detectors. Captured by 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. Since the primary electron beam 12 is more susceptible to the influence of the magnetic field as the speed is lower, it can be said that the lower the objective lens 26 becomes a stronger lens as it is closer to the sample 23. Therefore, when a negative potential is applied to the sample 23, the lower objective lens 26 becomes a lens with further low aberration.

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

  The distance between the upper objective lens 18 and the lower objective lens 26 is 10 mm to 200 mm. More preferably, the thickness is 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 the retarding. By separating the distance between the upper objective lens 18 and the lower objective lens 26 by 10 mm or more, the secondary electrons 21 a are easily detected by the detector 20. Further, when there is a gap of about 30 mm between the upper objective lens 18 and the lower objective lens 26, the sample 23 can be put in and taken out very easily.

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

  The magnetic pole forming the lower objective lens 26 includes a central magnetic pole 26a whose central axis coincides with the 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 has a shape with a smaller diameter at the top. The upper portion of the center magnetic pole 26a has, for example, a single-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 close to the center of gravity of the central magnetic pole 26a is thinned toward the center. An opening having an opening diameter d is open at the center of the upper magnetic pole 26b. The tip diameter D of the central 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 is shown. The upper surfaces on the sample side of both the center magnetic pole 26a and the upper magnetic pole 26b have the same height. The lower outer diameter of the center magnetic pole 26a is 60 mm. A thin outer diameter is not preferable because it causes a decrease in magnetic permeability.

  When the center magnetic pole 26a has D = 8 mm, the opening diameter d of the upper magnetic pole 26b is preferably 12 mm to 32 mm. More preferably, the opening diameter d is 14 mm to 24 mm. As the aperture diameter d is larger, the magnetic flux density distribution on the optical axis becomes gentler and wider, and the AT (ampere turn: number of coil turns N [T] and current I [A] necessary for focusing the primary electron beam 12 is increased. ], The product can be reduced. However, when the relationship between the opening diameter d and the tip diameter D is 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. A through hole may be provided at the center of the central 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 is deteriorated. On the other hand, if the difference in size between d and D is smaller than 4 mm, the magnetic poles are too close to be saturated and the primary electron beam 12 is not focused. Further, when the distance between the upper objective lens 18 and the lower objective lens 26 is 10 mm or less, workability is deteriorated. When this distance is longer than 200 mm, the opening angle α becomes too large. In this case, in order to optimize the aberration, adjustment using the upper objective lens 18 to reduce α is necessary, and the operability is deteriorated.

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

  As a method for applying a potential to the sample 23, a part of the magnetic poles of the lower objective lens 26 is sandwiched by an electrically insulating portion and part of the magnetic poles are floated from the ground potential, and a retarding voltage is applied to the sample 23 and a part of the magnetic poles. You can also. However, in this case, if a non-magnetic material is sandwiched in the magnetic circuit, the magnetic lens becomes weak. Further, when the retarding voltage is increased, discharge occurs. If the electrical insulating part 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 central magnetic pole 26a. The seal part 26f makes the space between the upper magnetic pole 26b and the central magnetic pole 26a vacuum-tight with an O-ring or brazing. In the lower objective lens 26, the vacuum side and the atmosphere side are hermetically separated by the upper magnetic pole 26b, the seal portion 26f, and the central magnetic pole 26a. Although not shown in the drawing, the upper magnetic pole 26b and the vacuum vessel are coupled so as to be airtight by an O-ring. By doing so, the lower objective lens 26 can be exposed to the atmosphere except for the vacuum side surface. Therefore, it becomes easy to cool the lower objective lens 26.

  Although the lower objective lens 26 can be placed in the vacuum vessel, the degree of vacuum is deteriorated. This is because if the coil part 26e is on the vacuum side, it becomes a gas emission source. Further, if the vacuum side and the atmosphere side are not hermetically separated in this way, there is a problem that the gas moves through the place where the lower objective lens 26 and the insulating plate 25 are in contact with each other when vacuuming is performed. is there.

  The coil portion 26e can be set to a coil current of 6000AT, for example. When the coil generates heat and becomes high temperature, the coating of the winding may melt and cause a short circuit. By allowing the lower objective lens 26 to be exposed to the atmosphere, the cooling efficiency is increased. For example, when the base of 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. By performing airtight separation in this way, the lower objective lens 26 with strong excitation can be obtained.

  The retarding unit will be described with reference to FIG.

  An insulating plate 25 is placed on the lower objective lens 26. The insulating plate 25 is, for example, a polyimide film or a polyester film having a thickness of about 0.1 mm to 0.5 mm, or a fluororesin or a ceramic plate. In order to increase the retarding voltage, the thickness of the insulating plate 25 may be increased from about 0.5 mm to about 2 mm. Then, a non-magnetic conductive sample stage 24 is placed thereon. The sample table 24 is, for example, an aluminum plate having a bottom surface of 250 μm, and is processed into a curved shape that is separated from the insulating plate 25 as the peripheral edge approaches the peripheral edge. The sample table 24 may be further filled with an insulating material 31 in a gap between the curved surface portion and the insulating plate 25. In this way, the withstand voltage between the lower objective lens 26 and the sample stage 24 is increased, and it can be used stably. The planar shape of the sample stage 24 is circular, but may be any planar shape such as an ellipse or a rectangle.

  A sample 23 is placed on the sample table 24. The sample stage 24 is connected to a retarding power source 27 in order to give a retarding voltage. The retarding power source 27 is a power source whose output that can be applied from 0 V to −30 kV is variable, for example. The sample stage 24 is connected to a sample stage stage plate 29 made of an insulator so that the position can be moved from outside the vacuum. Thereby, the position of the sample 23 can be changed. The sample stage 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 disposed so as to be insulated from the sample 23. The potential plate 22 is connected to a potential plate power source 28. The potential plate power supply 28 is a power supply whose output is variable, for example, from 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 20 mm. More preferably, the diameter of the opening may be 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 shape. The mesh portion of the mesh is preferably made thin so that electrons can easily pass therethrough so that the aperture ratio is increased. The potential plate 22 is connected to the first XY direction stage adjustment unit 56b so that the position can be moved from the outside of the vacuum for the central axis adjustment.

  The periphery of the sample stage 24 has a thickness on the potential plate 22 side. For example, when the potential plate 22 is flat, the potential plate 22 is close to the sample table 24 at the periphery of the sample table 24. Then, it becomes easy to discharge. Since the potential plate 22 has a shape away from the conductive sample stage 24 at a place other than the vicinity of the sample 23, the withstand voltage with respect to the sample stage 24 can be increased.

  The potential plate 22 is arranged so as not to be discharged by separating a distance of about 1 mm to 15 mm from the sample 23. However, it should be arranged so that it is not too far apart. The purpose is to overlap 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 the potential plate 22 is not present, the primary electron beam 12 is decelerated before being focused by the lower objective lens 26, and the effect of reducing aberrations is obtained. 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 are distributed far beyond the opening of the potential plate 22 toward the electron gun. In this case, the primary electrons may be decelerated before reaching the potential plate 22. As the opening diameter of the potential plate 22 is smaller, there is an effect of reducing 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, it is possible to adjust the potential difference between the sample 23 and the potential plate 22 within a range in which no discharge occurs, to adjust the distance between the sample 23 and the potential plate 22, and to appropriately select the opening diameter of the potential plate 22. It becomes important.

  By placing the potential plate 22 near the sample 23, the velocity of the primary electrons does not change so much until the potential plate 22 is close. The speed of the primary electrons decreases as the distance from the potential plate 22 approaches the sample 23, and the primary electrons are easily affected by the magnetic field. Since the magnetic field generated by the lower objective lens 26 is stronger as it is closer to the sample 23, both effects are combined, and the closer to the sample 23, the stronger the lens and the smaller the aberration.

  If the retarding voltage can be brought 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 the electrons enter 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, an SEM with high resolution and low acceleration can be realized.

  In the first embodiment, the breakdown 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 10 mm to 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 applied to the sample 23 and the potential plate 22 relatively easily. In the case of the sample 23 having a sharp portion, it is necessary to appropriately select the distance and the 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 phosphorson-type Robinson detector 20 is used. At least one of these is arranged directly below the upper objective lens 18. The secondary electron detector 19 is arranged so that the 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 disposed within 3 cm from the optical axis. More preferably, a detector 20 is used in which the center of the detection unit is placed on the optical axis and an opening through which primary electrons pass is provided at the center. The reason why it is set within 3 cm from the optical axis is that when retarding, 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 source 14, that is, energy obtained by multiplying − (Vacc−Vdecel) [V] by an electron charge, The sample 23 is scanned. At that time, signal electrons 21 are emitted from the sample 23. Depending on the values of the acceleration voltage and the retarding voltage, the way of being affected by electrons differs. The reflected electrons 21 b are subjected to a rotating force by the magnetic field of the lower objective lens 26 and at the same time are accelerated due to the electric field between the sample 23 and the potential plate 22. For this reason, the spread of the radiation angle of the reflected electrons 21b is narrowed, and it becomes easy to enter the detector 20. Further, the secondary electrons 21 a are also subjected to a rotating force by the magnetic field of the lower objective lens 26, and at the same time are accelerated due to the electric field between the sample 23 and the potential plate 22, and are detected under the upper objective lens 18. Incident on the vessel 20. Since both the secondary electrons 21a and the reflected electrons 21b are accelerated and the energy is amplified and enters the detector 20, the signal becomes large.

  In a general-purpose SEM, electrons are usually focused by an objective lens such as the upper objective lens 18 that is disposed 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 has a thickness, and it is necessary to separate the sample 23 from the upper objective lens 18 by the thickness. If the sample 23 is too close to the upper objective lens 18, the secondary electrons 21 a will not easily enter the secondary electron detector 19 outside the upper objective lens 18. Therefore, in the general-purpose SEM, a thin semiconductor detector 20 that is disposed at a position directly below the upper objective lens 18 and has an opening through which primary electrons pass is used. The sample 23 is placed with a slight 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 improve the performance.

  In the first embodiment, when the lower objective lens 26 is used as a main lens, the sample 23 can be placed 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. Naturally, a Robinson type detector 20 or a semiconductor detector 20 can also be provided. There is also a method in which a reflecting plate is placed, the signal electrons 21 are applied to the reflecting plate, 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 usages of the apparatus according to the first embodiment will be shown.

  For example, the acceleration voltage Vacc can be set to −4 kV, the sample 23 can be set to −3.9 kV, and the irradiation voltage Vi can be set to 100V. The closer the ratio of the acceleration voltage and the retarding voltage is to 1, the smaller the aberration coefficient. In the above description, the case where D = 8 mm and d = 20 mm is shown for the magnetic pole of the lower objective lens 26. However, if D = 2mm, d = 6mm, etc., the sample height and the acceleration voltage are limited. The performance can be improved.

  Further, when the acceleration voltage is −10 kV and there is no retarding, the secondary electron 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 21 a enter the semiconductor detector 20 with an energy of about 10 keV and can be detected.

  Further, when the acceleration voltage is set to -10.5 kV and the retarding voltage is set to -0.5 kV, the secondary electrons 21a cannot be detected with high sensitivity by the semiconductor detector 20. However, at this time, the secondary electrons 21 a 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 during adjustment in which the retarding voltage is raised while focusing.

  The lower objective lens 26 is designed so that primary electrons of 30 keV can be focused at Z = −4.5 mm. If the sample position is close to the lower objective lens 26, for example, at the position of Z = −0.5 mm, primary electrons of 100 keV can also be focused. When the retarding is not performed, the insulating plate 25 (insulating film) may 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, the lower objective lens 26 has a charged particle beam accelerated with an accelerating power source set to any one of −30 kV to −10 kV, as viewed from a position closest to the magnetic pole sample of the lower objective lens 26, and from 0 mm to 4. It is designed to be focusable at any height of 5 mm.

  The case where the acceleration voltage is −15 kV, the sample 23 is −5 kV, and −6 kV is applied to the potential plate 22 will be described. The primary electrons are 10 keV when they hit the sample 23. 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 21 a 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 21 b are accelerated and enter the detector 20. By making the voltage of the potential plate 22 adjustable in this way, the potential plate 22 can be used as an energy filter, and the sensitivity can be increased by further accelerating the signal electrons 21.

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

  At this time, even when the retarding is performed, the measurement is performed at a position of about Z = −7.75 mm including the thickness of the insulating plate 25 and the sample stage 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 with the help of the upper objective lens 18 without lowering the acceleration voltage.

  In addition, depending on the height of the sample 23, it may be possible to observe with better performance by focusing with the upper objective lens 18 alone. Thus, the optimal usage can be selected depending on the sample 23.

  In the above description, the case where the distance between the upper objective lens 18 and the lower objective lens 26 is 40 mm has been described, but 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. Α can be adjusted by this method.

  Further, when the retarding voltage is high, the signal electrons 21 easily pass through the vicinity of the optical axis and enter the opening for the primary electrons of the detector 20 to pass. Therefore, the smaller the opening of the detector 20, the better. Sensitivity is good when the opening of the detector 20 is about Φ1 to Φ2 mm. By adjusting the aperture diameter and height of the potential plate 22 and slightly shifting the position of the potential plate 22 from the optical axis, the trajectory of the signal electrons 21 is adjusted to improve the sensitivity so that the signal electrons 21 hit the detector 20. There is a way. In addition, it is also possible to insert an ecrosby (ExB) to be applied by directing an electric field and a magnetic field between the upper objective lens 18 and the lower objective lens 26, and the signal electrons 21 may be bent slightly. Since the traveling direction of the primary electrons and the traveling direction of the signal electrons 21 are opposite, a weak electric field and magnetic field may be provided to bend the signal electrons 21 slightly. If it is slightly bent, it can be detected without entering the opening at the center of the detector 20. Alternatively, an electric field may be applied between the upper objective lens 18 and the lower objective lens 26 from the side with respect to the optical axis. Even if it does in this way, a primary electron is hard to be influenced, and if it is only a lateral shift, there will be little influence on an image. 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 reflected 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, they can be detected with high sensitivity. However, if the distance is approximately 40 mm, the number of reflected electrons 21b that do not enter the detector 20 increases, and the amount of reflected 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 reflected electrons 21b can be suppressed, and the semiconductor detector 20 or the Robinson detector 20 can be detected with high sensitivity. Thus, retarding can be used even when the potential plate 22 is not provided.

  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 utilized to be used as a sample stage. The first XY direction stage adjustment unit 56b can also move in the direction approaching the upper objective lens 18 (Z direction stage adjustment unit 56a). Thereby, the apparatus is used like a general-purpose SEM. The reflected electrons 21b are detected by the semiconductor detector 20 or the Robinson detector 20, and the secondary electrons 21a are detected by the secondary electron detector 19. Usually, the sample 23 is at the ground potential, but it can be simply retarded (retarding can be performed without the potential plate 22).

  When only the lower objective lens power source 42 is used, the apparatus is configured such that the distance between the lower objective lens 26 and the sample measurement surface is closer 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 closer than the distance between the lower objective lens 26 and the sample measurement surface. If high measurement performance is not required and the measurement is relatively low performance, even when only the upper objective 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 closer. 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 measurement at a low magnification, the sample 23 may be disposed 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 30 keV when passing through the upper objective lens 18, are accelerated toward the potential plate 22 from the upper objective lens 18, and decelerate toward the sample 23 around the potential plate 22.

  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 the 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 are decelerated and cannot be detected. The secondary electrons 21 a can be detected by the secondary electron detector 19. If the retarding voltage is applied to the sample 23, the semiconductor detector 20 can also detect the secondary electrons 21a.

  Next, moving the intersection of the deflection trajectories by adjusting the two-stage deflection coil 17 will be described. The two-stage deflection coil 17 scans the sample 23 two-dimensionally. 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 source 43 that varies the strength of the upper stage deflection coil 17a, a lower stage deflection power source 44 that varies the strength of the lower stage deflection coil 17b, and an upper stage deflection power source 43. It is controlled by a control device 45 that controls the lower deflection power source 44.

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

  The two-stage deflection coil 17 forms an orbit where electrons pass 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 performed as described above. When the lower objective lens 26 is used as the main lens, the intensity ratio of the upper deflection coil 17a and the lower deflection coil 17b is such that the electrons pass through the intersection of the main surface of the lower objective lens 26 and the optical axis. Adjusted to The adjustment is performed by a control device 45 that adjusts a use current ratio between the upper deflection power supply 43 and the lower deflection power supply 44. By doing so, image distortion is reduced. Instead of shifting the intersection (cross point) of the deflection trajectory by adjusting the current ratio used, a method of switching coils with different numbers of turns using a relay or the like (providing a plurality of coils with different numbers of turns and using the coil with a controller) In the case of an electrostatic lens, a method of switching the voltage (a method of changing the working voltage ratio) may be employed.

  The deflection coil 17 may be disposed in a gap in the upper objective lens 18. The deflection coil 17 may be in the upper objective lens 18 or may be positioned further upstream of the charged particle beam as shown in FIG. When electrostatic deflection is employed, a deflection electrode is employed instead of the deflection coil.

(Shield electrode)
In the SEM according to the first embodiment, as shown in FIG. 1, more specifically, between the potential plate 22 and the sample table 24, more specifically, the sample 23 placed on the potential plate 22 and the sample table 24 Between these, the shield electrode 51 is arrange | positioned. 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 with 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 location near the sample 23 on the potential plate 22, but the potential plate 22 has a shape away from the sample stage 24 at a location other than near the sample 23. Of course, the insulator 52 may be provided at a location other than the vicinity of the sample 23 on the potential plate 22, that is, at a location further away from the sample stage 24 as shown in FIG.

  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 (secondary electrons 21a and reflected electrons 21b). Pass through. In short, it is only necessary that the central axes of the openings of the shield electrode 51 and the potential plate 22 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 by arranging the shield electrode 51 having the same potential as the sample stage 24 will be described.

  First, it is effective when it is not desired to apply a strong electric field to the sample 23 during the retarding. Conventionally, if a strong electric field is generated on the surface of the sample 23 as a result of applying a potential difference between the potential plate 22 and the sample stage 24, a 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, the potential difference applied between the potential plate 22 and the sample stage 24 can be applied between the potential plate 22 and the shield electrode 51 by arranging 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 relaxed. This is particularly effective for a sample that does not generate an electric field because the sample 23 has a fine structure such as a semiconductor element.

  Further, when the sample 23 is an insulator, the retarding voltage potential 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 have the same potential as the sample table 24. As a result, even if the sample 23 is an insulator, the surface of the sample 23 can be set at the potential applied to the sample table 24.

  Further, an electrostatic lens is formed by the potential difference given between the potential plate 22 and the sample stage 24. When the surface of the sample 23 has sharp edges or irregularities, or when the surface of the sample 23 has an inclined shape, or when the sample 23 has a cylindrical shape and it is desired to observe the vicinity of the end of the cylinder, the sample 23 Since an electric field is generated on the surface, the equipotential lines that become the electrostatic lens are not rotationally symmetric with respect to the optical axis, and the electrostatic lens has a large aberration. On the other hand, the arrangement of the shield electrode 51 alleviates the electric field generated on the surface of the sample 23 and makes the electrostatic lens 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, even an insulator becomes difficult to be charged. When the irradiation voltage is set to about 1 keV by retarding, the insulator can be observed in a state where it is difficult to be charged by arranging the shield electrode 51 and setting the sample stage 24 and the shield electrode 51 to the same potential. 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 becomes a low aberration lens. When a negative potential is applied to the sample 23, the closer to the sample 23, the stronger the lens, and the lower objective lens 26 becomes a further low aberration lens. The signal electrons 21 are accelerated by the electric field generated by the retarding voltage of the sample 23, and the energy is amplified and enters the detector 20. Therefore, 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 lower objective lens 26 is more likely to bend. Become a strong lens. In addition, the primary electron beam 12 is almost decelerated near the shield electrode 51, and only slight deceleration occurs between the sample 23 (when the sample stage 24 and the shield electrode 51 are at 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 it is closer to the sample 23, and the width of the stronger 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 provided with a different potential different from that of the sample table 24 by a separate power source. If the shield electrode 51 is given a potential at which the secondary electrons 21a do not pass through the shield electrode 51, for example, a potential 200V lower than the potential of the sample 23, the signal electrons 21 that pass through the shield electrode 51 can be limited to the reflected electrons 21b. An image by only the reflected electrons 21b is obtained. The potential plate 22 is integrated with the shield electrode 51, the potential plate 22 is separate from the shield electrode 51, or the first detector 720 or the second detector 820 is provided. There is something attached. Furthermore, 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 54 a to 54 f are correctors for adjusting an image with aberration displayed on the display device 57. The correctors 54 a to 54 d are connected to the corrector power supply 55, and the control device 45 controls the corrector power supply 55. In the correctors 54a to 54d, for example, the corrector 54b and the corrector 54d may be alignment deflectors, and the corrector 54a and the corrector 54c may be 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 and the optical axis of the lower objective lens 26, and can be moved using, for example, screws.

  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 and accurately match it, for example, a corrector 54c may be used as an alignment deflector. The display device 57 displays the electrical signal output from the detector 20 two-dimensionally in synchronization with the scanning signal. While viewing the image on the display device 57, the alignment deflector 54c deflects the trajectory of the primary electron beam 12 and adjusts it to the optical axis of the lower objective lens 26 so that an image with less aberration is obtained. Although the alignment deflector can be formed in one stage as described above, a two-stage alignment deflector may be used to further adjust the axis. For example, by using the corrector 54b and the corrector 54d as alignment deflectors, the trajectory can be translated, tilted, or a combination thereof.

  The wobbler method may be used as the axis adjustment method. The wobbler method is a function that periodically varies the focal length and is used to facilitate axis alignment. The wobbler method is a method in which the objective lens diaphragm 16 and the deflector 54 are adjusted so as to obtain an isotropic movement by looking at the movement of the image. In the wobbler method, it is necessary to increase the scanning speed. When adjustment is to be performed at a high magnification, adjustment is sometimes difficult because the signal amount is small and the image is difficult to see. In order to find the optical axis of the lower objective lens 26 and to 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) that generates aberration by the controller 45 and used. For example, the lower objective lens 26 is scanned two-dimensionally only by the upper deflection coil 17a. That is, the deflection fulcrum is not near the main surface of the lower objective lens 26 but between the object point of the lower objective lens 26 and the front of the main surface of the lower objective lens 26. In this case, the position of the upper deflection coil 17a becomes the deflection fulcrum.

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

  A specific example is shown. When the corrector 54b and the corrector 54d are used as alignment deflectors, the center of distortion may be moved to the center of the display screen by adjusting the deflection intensity. If the distortion is distorted rather than being rotated with respect to the center, for example, the corrector 54c is used as the astigmatism corrector, and astigmatism correction can be made to have a center-symmetric distortion. Further, the axis may be adjusted by moving the potential plate 22 or the shield electrode 51. When an ordinary image is viewed (that is, the deflection fulcrum is near the main surface of the lower objective lens 26), an image with corrected aberration can be obtained.

  For example, an upper deflection coil 17a and a lower deflection coil 17b are used as deflectors for generating aberrations for two-dimensional scanning with respect to the lower objective lens 26, and the deflection fulcrum is adjusted by changing the intensity ratio. 26 may be scanned two-dimensionally. As a result, a distorted image suitable for the magnification can be seen. For example, when the deflection fulcrum is brought close to the object point of the lower objective lens 26 (crossover point of the condenser lens 15b), the distorted image can be easily seen at high magnification. The above method can also be used when the upper objective lens 18 is a main lens.

  This is particularly effective when the lower objective lens 26 is mainly used and when aberrations during retarding are adjusted. Axis alignment and astigmatism correction may be automatically corrected from the distorted image by a program. Adjustment is performed using the two-stage deflection coil 17 and the objective lens diaphragm 16 so that the center of the distortion image displayed on the display device 57 is at the center of the display screen, and then the distortion is corrected using the correctors 54a to 54f. It is preferable that the image approaches point symmetry.

  Further, in the SEM according to the first embodiment, the wobbler method may be used. In the wobbler 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 a wobbling method.

(Movement mechanism)
As shown in FIG. 1, the SEM according to the first embodiment includes a moving mechanism that moves the potential plate 22 and the sample stage 24 in the XYZ directions. The space on the upper surface side of the lower device 72 of the SEM is surrounded by the vacuum wall 60. As a result, 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 disposed outside the vacuum and are operated by the user. The potential plate stage 61 moves 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 moves in the XY directions by a user 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 direction 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.

  Further, by using the moving mechanism as one of the above-described correctors, the axis of the electrostatic lens can be adjusted by moving the potential plate 22 and the shield electrode 51. 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.

  When the retarding is performed, 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 axial deviation between the electrostatic lens and the magnetic lens, the axial deviation adjustment by the potential plate stage 61 may be performed. As described above, the potential plate stage 61 can be adjusted in height (Z direction) according to the height of the sample 23 and moved in the left-right front-rear direction (XY direction).

  Regarding the increase in aberration due to the distortion of the electrostatic lens, although the electrostatic lens can be made axially symmetric by the shield electrode 51, it may slightly deviate from the magnetic lens due to the inclination of the sample 23, for example. Aberration can be adjusted by fine adjustment with 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. What is necessary is just to operate and adjust the 1st XY direction stage adjustment part 56b so that it may become the center of the display screen of the apparatus 57. FIG. Thereby, axial alignment of the electrostatic lens and the lower objective lens 26 can be performed. 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. A space on the sample 23 side from the potential plate 22 (hereinafter referred to as “lower space”) and a space on the upper objective lens 18 side from the potential plate 22 (hereinafter referred to as “upper space”) are a potential plate stage. 61 and slide plate 62 are used to separate them in a vacuum. The gas introduction mechanism 58 introduces various gases into the lower space, makes the inside of 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 observation may be performed without coating the 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 introduction mechanism 58 to make the inside of the lower space a low vacuum. Alternatively, the sample 23 may be neutralized by spraying a small amount of gas or ions introduced using the gas introduction mechanism 58 onto the sample 23.

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

  Note that when the vacuum is reduced, a withstand voltage failure between the shield electrode 51 and the potential plate 22 is likely to occur. Therefore, as shown in FIG. 2, which will be described later, by providing the insulator 52 at a location further away from the sample stage 24, the creeping distance of the insulator 52 is increased, and the withstand voltage of the insulator 52 is increased. It may be.

  Instead of the gas introduction mechanism 58, it is also possible to make the inside of the lower space a low vacuum by narrowing the exhaust port for exhausting the inside of the lower space.

[Embodiment 2]
With reference to FIG. 2, a schematic configuration of the SEM according to the second embodiment of the present invention will be described. Hereinafter, the same parts as those of the first embodiment of the present invention are denoted by the same reference numerals, and detailed description thereof is 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 reflected electrons 21b and the characteristic X-ray 121 are detected on the lower surface of the potential plate 22. The second detector (electromagnetic wave detector) 820 is provided. In addition, as described above, the insulator 52 is provided at a location further away 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. In the detection unit, for example, the first detector 720 is arranged in a part of the region viewed from the lower objective lens 26 side, and the second detector 820 is arranged in the other region. The detection unit is provided with a hole through which the primary electron beam 12 and the secondary electron 21a pass. Note that the first detector 720 and the second detector 820 may be attached to the lower surface of the potential plate 22 separately or only one of them.

  The first detector 720 and the second detector 820 are arranged at positions 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. It is far away. For this reason, the solid angle of the reflected electrons 21b and the characteristic X-rays 121 incident on the first detector 720 and the second detector 820 increases. 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 enabling the sample 23 to be observed with high resolution. The second detector 820 is arranged so as not to interfere with the detection of the reflected electrons 21b by the first detector 720, and the observation of the sample 23 by detecting the reflected 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. In addition, the detector 20 may be disposed above the potential plate 22. The size of the hole of the first detector 720 or the second detector 820 may be small enough to pass the primary electron beam 12. For example, the hole is a circular through hole, and its diameter is preferably about 1 to 2 millimeters, for example. By making the hole small in this way, most of the reflected electrons 21b 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 become 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 the device configuration of the SEM according to the third embodiment of the present invention. Hereinafter, the same parts as those in Embodiments 1 and 2 of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  The difference between the SEM according to the third embodiment of the present invention and the SEM according to the first embodiment of the present invention includes a second detector (electromagnetic wave detector) 110 that detects the characteristic X-ray 121 emitted from the sample 23. 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 arranged on a sample table 24 arranged 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 disposed at the lower end of the upper objective lens 18. The secondary electron detector 19 that detects the secondary electrons 21 a is disposed on the side of the upper objective lens 18.

  Here, in the SEM shown in FIG. 3, the second detector 110 that detects the characteristic X-ray 121 emitted from the sample 23 is arranged. The second detector 110 is an energy dispersive X-ray (EDX (sometimes referred to as EDS)) analyzer. The second detector 110 is attached as a device attached to the SEM. In this SEM, the EDX analysis of the sample 23 can be performed with the observation of the sample 23 by detecting the signal electrons 21. The second detector 110 is arranged so as not to interfere with the detection of the signal electrons 21 by the first detectors 19 and 20, and the detection of the signal electrons 21 and the detection of the characteristic X-ray 121 are performed simultaneously ( Can be done in parallel), but is not limited to this.

  The second detector 110 has a structure in which the arm portion 113 extends substantially linearly from the main body portion arranged outside the vacuum wall 60 to the inside of the vacuum wall 60. The arm portion 113 is inserted into a vacuum portion surrounded by the vacuum wall 60. A plate-like portion 114 formed in a plate shape is provided at the distal end portion of the arm portion 113. The arm part 113 and the plate-like part 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 portion 65 using a plurality of adjustment bolts 67 and nuts. By adjusting the adjustment bolt 67 and the nut, the mounting position of the mount portion 65 and the adjustment bolt 67 and the like are adjusted. Thereby, the position of the second detector 110 with respect to the sample 23 can be finely adjusted. The large moving direction of the second detector 110 is the vertical direction (the arrow Z direction in the figure; the incident direction of the primary electron beam 12) and the longitudinal direction of the arm portion 113 (the arrow Y direction in the figure). By adjusting the position of the second detector 110 in this way, 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-like portion 114 with respect to the sample 23, that is, the position of the plate-like portion 114 with respect to the position through which the primary electron beam 12 passes can be changed. Thus, even when the primary electron beam 12 is focused using the upper objective lens 18, height adjustment and front / rear / left / right adjustment are possible. When not in use, the second detector 110 and the plate-like portion 114 can be moved and stored in the longitudinal direction of the arm portion 113 (in the direction of arrow Y in the figure).

  The plate-like 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-like portion 114 is provided with a hole portion 114a. The position of the plate-like portion 114 is adjusted so that the primary electron beam 12 passes through the hole portion 114a. An X-ray detector 120 is disposed on the surface of the plate-like portion 114 on the sample 23 side (the lower surface in the figure). 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 enters the X-ray detection unit 120. The second detector 110 detects the incident characteristic X-ray 121 when the characteristic X-ray 121 is incident on the X-ray detector 120.

  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 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-like portion 114 of the second detector 110 also functions as a potential plate when performing retarding. That is, the retarding power source 27 is connected to the sample stage 24, and the plate-like portion 114 is connected to, for example, the ground potential via the arm portion 113. The plate-like portion 114 functions in the same manner as the potential plate 22 in the above-described embodiment. Therefore, the same effect as when the potential plate 22 is provided can be obtained without providing the potential plate 22 separately. 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-like 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 accordance with this, EDX analysis of the sample 23 can be performed, 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 the retarding is performed. The second detector 110 only needs to include an X-ray detection unit that detects the characteristic X-ray 121 and the like.

[Embodiment 4]
FIG. 4 is a cross-sectional view illustrating a schematic example of the device configuration of the SEM according to the fourth embodiment of the present invention. Hereinafter, the same parts as those of Embodiments 1, 2, and 3 of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  The difference between the SEM according to Embodiment 4 of the present invention and the SEM according to Embodiment 1 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 a polycapillary 617 and can perform analysis by WDX 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 disposed so as to be positioned in the vicinity of the sample 23 via a potential plate fixing portion 218 attached to the housing 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 positioned in the vicinity of 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. In addition, an insulating plate 25, a sample table 24, an insulating material 31, and the like are disposed above the lower objective lens 26. The sample stage 24 is connected to the retarding power source 27, and the potential plate 422 is connected to the potential plate power source 28. By having such a configuration, retarding is performed in this SEM, as in the first embodiment described above.

  As described above, in the apparatus shown in FIG. 4, each of the second detectors 210 and 610 can be brought close to the sample 23, so that the detection efficiency of the EDX analysis and the WDX analysis is increased, and the sample 23 is obtained with high resolution. Can be observed. Moreover, the effect by performing retarding is acquired, irradiation electron energy can be made small and the depth which the electron of the primary electron beam 12 enters in the sample 23 can be made shallow. This enables high-resolution observation of the surface shape of the sample. Further, 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 the members 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 moved independently 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 side 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 moved independently 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 EDX analysis or 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, beryllium thin film, organic thin film, silicon nitride thin film, etc.). It is preferable that it is not limited. When the potential plate 422 is formed of a light element thin film, X-rays easily pass through the potential plate 422. Note that when the potential plate 422 is formed of a light element thin film, X-rays easily pass through the potential plate 422 and enter the detector even if 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 detection peak different from that of the sample 23 to be analyzed is used as the material of the potential plate 422. Also good. Thereby, it becomes easy to remove the influence of the potential plate 422 in the analysis result.

[Embodiment 5]
FIG. 5 is a cross-sectional view illustrating a schematic example of an apparatus configuration of an SEM according to the fifth embodiment of the present invention. Hereinafter, the same parts as those of Embodiments 1, 2, 3, and 4 of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

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

  The second detector 410 includes 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 surface shape with the point where the CL 321 is emitted from the sample 23 as a focal point. The CL 321 incident on the mirror surface 420b 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. Thereby, CL321 is efficiently detected by the detector main body 310a.

  A potential plate 422 which is a conductive plate is attached to the lower part of the parabolic mirror 420. 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 positioned in the vicinity of the sample 23. In addition, an insulating plate 25, a sample table 24, an insulating material 31, and the like are disposed above the lower objective lens 26. The sample stage 24 is connected to the retarding power source 27, and the potential plate 422 is connected to the potential plate power source 28. By having such a configuration, retarding is performed in this SEM, as in the first embodiment described above.

  Note that the size of the hole through which the primary electron beam 12 or the like provided in the parabolic mirror 420 passes is appropriately set. That is, if the hole portion is relatively small, the amount of reflected electrons 21b passing through decreases, but the light amount of CL 321 increases. On the other hand, if the hole is relatively large, the amount of light of CL321 decreases, but the amount of passage of the reflected electrons 21b increases. Note that CL321 may be detected by using a parabolic mirror 420 as an elliptical mirror. Further, a reflecting mirror may be arranged in place of the parabolic mirror 420, and an optical microscope and a fluorescence microscope may be attached to the optical lens 411 and the detector main body 310a for observation. You may make it observe the image by the secondary electron detector 19 and the semiconductor detector 20, and the image by the 2nd detector 410 simultaneously. Furthermore, the image by the signal electrons 21 and the image by the second detector 410 may be displayed in an overlapping manner.

[Embodiment 6]
FIG. 6 is a cross-sectional view illustrating a schematic example of an apparatus configuration of an SEM according to the sixth embodiment of the present invention. Hereinafter, the same parts as those in the first to fifth embodiments of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  The difference between the SEM according to the sixth embodiment of the present invention and the SEM according to the first embodiment of the present invention is that an open type 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. The open-type case 700 has an upper surface portion 701 having the same function as the shield electrode 51, and a side surface portion 702 having the same function as the wiring 53. Specifically, the upper surface portion 701 is electrically connected to the sample table 24 via the side surface portion 702. As a result, the upper surface portion 701 has the same potential as the sample table 24.

  The open case 700 may be fixed to the sample table 24 using a fastener or the like. Alternatively, the upper part and the lower part can be separated 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 portion 701 can be easily adjusted.

  For example, the upper surface portion 701 is a nonmagnetic material and has conductivity. The end of the side surface portion 702 that contacts the sample table 24 is the 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 portion 701 has the same potential as the sample stage 24.

  The upper surface portion 701 is disposed 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 table 24, a potential difference is generated between the sample plate 24 and the potential plate 22. In the case of the sample 23 having a sharp point, when there is no upper surface portion 701, discharge is likely to occur between the potential plate 22 and the sample. Discharge can be prevented by the upper surface portion 701 covering the sharpness of the sample 23.

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

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

[Embodiment 7]
FIG. 7 is a cross-sectional view illustrating a schematic example of an apparatus configuration of an SEM according to the seventh embodiment of the present invention. Hereinafter, the same parts as those in the first to sixth embodiments of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  The difference between the SEM according to the seventh embodiment of the present invention and the SEM according to 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.

  Unlike the open-type case 700, the sealed case 800 stores the sample 23. The sealed case 800 has a sealed space inside. The sealed case 800 has an upper surface portion 801 that has the same function as the shield electrode 51, and a side surface portion 802 that has 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. As a result, the upper surface portion 801 has the same potential as the sample table 24.

  By providing an opening in the upper surface portion 801 and closing the opening using the conductive thin film 803, a sealed space is realized in the sealed case 800. By selecting the conductive thin film 803 variously, primary electrons, reflected electrons, electromagnetic waves, and the like are transmitted through the conductive thin film 803. 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 Axis alignment between the two is unnecessary.

  Gas or liquid can be introduced into the sealed case 800 due to its sealing property. For this reason, as the sample 23, it is possible to handle liquids, organisms, cells, and the like that cannot be observed under high vacuum.

  The sealed case 800 may also be fixed to the sample stage 24 using a fastener or the like, like the open type case 700. Alternatively, the upper part and the lower part can be separated 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 portion 801 can be easily adjusted.

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

  The sealed case 800 can store a sample that evaporates and deforms when evacuated. For example, it is suitable for organisms and samples in liquids. A height adjustment base may be placed in the sealed case 800 so that the sample in the liquid is in contact with the conductive thin film 803. You may install so that gas may exist between the conductive thin film 803 and the sample 23. FIG. The gas may be air, helium, hydrogen, nitrogen, argon or the like. The pressure may be atmospheric or reduced. The sealed case 800 is made to prevent gas from leaking through an O-ring or the like.

  The sealed case 800 may be provided with an exhaust port, or when the lid is covered, the outside air may be decompressed and sealed. You may seal so that gas may be enclosed.

  It should be noted that the SEM according to the seventh embodiment of the present invention also includes the insulating portion 810 in which the insulating plate 25 and the insulating material 31 are integrated, unlike the SEM according to the first embodiment of the present invention. It is. However, it should be noted that, unlike the SEM of the sixth embodiment of the present invention, the portion corresponding to the insulating plate 25 extends toward the outside of the apparatus, 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 the device configuration of the SEM according to the eighth embodiment of the present invention. Hereinafter, the same parts as those in the first to seventh embodiments of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  The difference between the SEM of Embodiment 8 of the present invention and the SEM of Embodiment 1 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 of 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 placed on a sample base 904 disposed 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 to the potential plate 22 as a sample stage via a wiring 903. With this connection, the shield electrode 900 and the potential plate 22 have the same potential.

  The sample base 904 is for adjusting the distance between the sample 23 and the shield electrode 900. By adjusting the height of the sample base 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 also has the same function as the moving mechanism of the first embodiment described above, description thereof is omitted here.

  In the SEM of 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 EPMA, which is a charged particle beam apparatus, 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 charged particle beam apparatus. A negative potential slightly higher than the acceleration voltage of the primary electron beam 12 is applied to the sample 23, and the primary electron beam 12 is not applied to the sample 23 and reflected. In this case, the signal electrons 21 are reflected from the primary electron beam 12. Information on minute irregularities and potential distribution on the sample surface can be obtained. 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 apparatus configuration of an SEM according to the ninth embodiment of the present invention. Hereinafter, the same parts as those in the first to seventh embodiments of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted.

  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 second detector 210 for EDX analysis and a second detector 610 for WDX analysis are provided. is there. Since 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, they will not be described here.

  Note that FIG. 9 does not show the potential plate 22 and the shield electrode 51 described in FIG. 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 described in FIG.

  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 function 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 disposed on the potential plate stage 61 shown in FIG. Further, the SPM 500 may be disposed on the lower objective lens 26.

  The SPM 500 includes a cantilever (plate spring) 501, an SPM detector 502, and an SPM laser 503. A probe (SPM probe) 501 a is provided at the tip of the cantilever 501. The SPM 500 detects a change in force applied between the probe 501a and the sample 23 as a change amount of deflection or vibration of the cantilever 501. The amount of change is detected when the SPM detector 502 detects the 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 be expanded and contracted in each direction of XYZ. The SPM 500, the sample 23 or the sample stage 24 can be moved in the XYZ directions by the piezoelectric element.

  In addition, a three-dimensional image using a method of synthesizing depth of focus (a method of automatically capturing multiple images while moving the focal position and synthesizing images to obtain an image with a deep depth of field) The probe 501a of the cantilever 501 may be operated while obtaining it.

  The movement range of the SPM 500 is narrow. For this reason, it is expected that it takes a considerable time to search for the target measurement position over a wide range on the sample 23 only by observation using the SPM 500. In the SEM of this embodiment, the SEM image of the sample 23 can be observed in real time and in a wide range, 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 installed at the target measurement position by the second XY direction stage adjustment unit 56c or the piezoelectric element.

  When only the upper objective lens 18 is used and the sample 23 is observed, it is necessary to bring the upper objective lens 18 and the sample 23 closer to each other. Therefore, it is expected that it will be difficult to dispose the optical system (here, the SPM detector 502 and the SPM laser 503) that detects the deflection or vibration variation of the cantilever 501 directly below the upper objective lens 18. Is done.

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

  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 (increasing the working distance). The expansion of the working distance reduces the resolution of the SEM. In the SEM of the present embodiment, by using the lower objective lens 26 in addition to the upper objective lens 18, if the thickness of the sample 23 is approximately 5 mm or less, the SPM 500 is observed while observing the sample 23 with high resolution. It is possible to measure and manipulate the sample 23 by using it.

  Further, when observing the sample 23 at a low magnification, the upper objective lens 18 may be used to focus the primary electron beam 12. 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. Naturally, even if the working distance is increased, it is possible to avoid a reduction in the resolution of the SEM, so that the above-described optical system can be easily disposed immediately 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 electrical characteristics that can be measured 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 of the sample 23, and the sheet resistance of the sample 23. Can be mentioned.

  Further, the manipulator 504 can be used to measure the current that flows when the sample 23 is irradiated with the electron beam, that is, the electron beam excitation current (EBIC). In the SEM of this embodiment, the internal structure of the sample 23 can be imaged based on the measured electron beam excitation current. This makes it possible to visualize the pn junction formed inside the sample 23 and observe the crystal defects of the sample 23.

  Further, the local resistance of the sample 23 can be measured by measuring an 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 manipulated by bringing the probe 504 a of the manipulator 504 into contact with the sample 23. Various shapes of the probe 504a are prepared, and a part of the sample 23 can be manipulated and processed (cut, peeled, punched, moved, joined). For example, by using the probe 504 a, a part of the sample 23 can be grasped, moved, and joined to another position of the sample 23. Further, the tensile measurement and stress measurement of the sample 23 can be performed.

  A mechanism for supplying gas or liquid to the manipulator 504 may be provided. A gas or liquid supplied from the mechanism is supplied from the probe 504a to the sample 23, thereby depositing a thin film on the surface of the sample 23, marking on the surface of the sample 23, etching the surface of the sample 23, sample 23 It is possible to cause a chemical reaction on the surface of the material.

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

  In the case of retarding, the probe 504a is preferably insulated from the manipulator 504.

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

  The heating laser 601 is for heating the sample 23 or sublimating / evaporating a part of the sample 23 by irradiating the sample 23 with laser light. In the SEM of this embodiment, the state change of the sample 23 caused by laser light irradiation can be observed in real time and with high resolution. The heating laser 601 may be disposed at the position of the polycapillary 617 shown in FIG. Further, the heating laser 601 can be used in a retarded state. Furthermore, it is preferable to arrange the emission port of the heating laser 601 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 the present embodiment, the sample 23 can be cut and processed using the focused ion beam 602. If the lower objective lens 26 is used, the lens barrel of the focused ion beam 602 can be disposed in the vicinity of the sample 23 without interfering with the upper objective lens 18.

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

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

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining 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 necessary. The potential plate 22 or the shield electrode 51 can be attached to and detached from the SEM. Even when retarding, 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 positioned above the probe 504a or the cantilever 501 of the manipulator 504.

  The shape of the potential plate 22 and the shield electrode 51 may be rotationally symmetric with respect to the optical axis of the primary electron beam 12, and is not limited to a plate shape. For example, a ring shape may be sufficient, and the thing which has a hole at the front-end | tip by the cone shape convex downward may be sufficient. The arrangement configuration of the potential plate 22 and the shield electrode 51 in the upper part of 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.

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

  A charged particle beam apparatus according to an aspect 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 onto the sample, and the sample. A sample stage, and a shield electrode and a potential plate that allow the charged particle beam to pass through.From the sample stage side, the shield electrode and the potential plate are arranged in this order, and the sample stage, the potential plate, A potential difference is applied between them, and a potential that relaxes the electric field generated in the sample due to the potential difference is applied to the shield electrode.

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

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

  The objective lens includes an upper objective lens disposed on the side on which the charged particle beam is incident on the sample, and an upper objective power supply that varies the intensity of the upper objective lens, and an intensity of the lower objective lens. When using only the upper objective lens power source, the sample is disposed between the upper objective lens and the lower objective lens, and when using only the lower objective lens power source. It is preferable that the distance between the lower objective lens and the measurement sample surface is closer 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. Preferably match.

  It is preferable to provide a gas introduction mechanism that retains the gas in the vicinity of the sample by introducing the gas into a space including the potential plate and the sample stage.

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

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

  The shield electrode and the conductor preferably constitute a sample case that is placed on the sample stage so as to cover the sample.

  The sample case is a sealed container, and a thin film member is provided so as to block the opening of the shield electrode, and the thin film member passes the charged particle beam and signal electrons or electromagnetic waves emitted from the sample. It is preferable that it is comprised from the material to make.

  The potential plate is preferably 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 disposed on the opposite side of a charged particle beam that emits a charged particle beam and the side on which the charged particle beam is incident on a sample, and is emitted from the charged particle source. A lower objective lens that focuses the charged particle beam on the sample, a sample stage on which the sample is placed, a shield electrode and a potential plate that pass the charged particle beam, and a moving mechanism that moves the shield electrode and the potential plate And a gas introduction mechanism for retaining the gas in the vicinity of the sample by introducing a gas into a space including the potential plate and the sample stage. From the sample stage side, the shield electrode and the potential plate are Are arranged in this order.

  The arrangement configuration of the upper portion of the sample is determined so that a space for performing processing on the sample including at least one of operation, processing, or measurement on the sample is secured on the lower objective lens. It is preferred that

  The scanning electron microscope which concerns on 1 aspect of this invention is equipped with the said charged particle beam apparatus.

  DESCRIPTION OF SYMBOLS 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 reflected electrons, 22, 422 potential plates, 23 samples, 24 sample stands, 25 insulating plates, 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 deflection power supply, 44 Lower 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 adjustment unit, 56b First XY direction stage adjustment unit, 56c Second XY direction stage adjustment unit, 57 display device, 58 gas introduction mechanism, 60 vacuum wall, 61 potential plate stage, 62 slide plate, 65 mounting portion, 67 adjustment bolt, 71 upper device, 72 lower device, 110, 210, 410, 610, 820 second Detector (electromagnetic wave detector), 113 arm, 114 plate-like part, 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-type case, 701, 801 top surface portion, 702, 802 side surface portion, 710, 810 insulation portion, 720 first detector (semiconductor detector, MCP) provided on the potential plate Detector or Robinson detector), 800 sealed case 803 Conductive thin film 901 Shield electrode moving mechanism 904 Sample base

Claims (13)

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 onto the sample;
A sample stage on which the sample is placed;
A shield electrode and a potential plate for passing the charged particle beam;
A moving mechanism for moving the shield electrode and the potential plate;
A display device that displays an image of an opening that allows the charged particle beam to pass through the shield electrode;
From the sample stage side, the shield electrode and the potential plate are arranged in this order,
A potential difference is given between the sample stage and the potential plate,
A charged particle beam device, wherein a potential that relaxes an electric field generated in the sample due to the potential difference is applied to the shield electrode. 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 onto the sample;
A sample stage on which the sample is placed;
A shield electrode that allows the charged particle beam to pass therethrough and a potential plate;
From the sample stage side, the shield electrode and the potential plate are arranged in this order,
A potential difference is given between the sample stage and the potential plate,
A potential that relaxes the electric field generated in the sample due to the potential difference is applied to the shield electrode,
The charged particle beam apparatus according to claim 1, wherein the objective lens is a lower objective lens disposed on a side opposite to a side on which the charged particle beam is incident on the sample. An upper objective lens that is arranged on the side where the charged particle beam is incident on the sample and focuses the charged particle beam emitted from the charged particle source onto the sample;
An upper objective lens power source for varying the intensity of the upper objective lens;
A lower objective lens power source for varying the intensity of the lower objective lens,
When using only the upper objective power supply, the sample is placed between the upper objective lens and the lower objective lens,
3. The charging according to claim 2, wherein when only the lower objective lens power source is used, the distance between the lower objective lens and the measurement sample surface is made shorter than the distance between the upper objective lens and the measurement sample surface. Particle beam device. The potential plate has an opening through which the charged particle beam passes,
The opening of the potential plate is at a position closest to the lower objective lens,
Insulator is connected to the potential plate, the shield electrode is connected to the insulator,
The distance between the shield electrode and the potential plate where the insulator is connected is greater than the distance between the shield electrode and the opening of the potential plate.
The charged particle beam apparatus according to claim 2 or 3 , wherein the central axes of the openings of the shield electrode and the potential plate substantially coincide with each other. An upper space which is a space on the upper objective lens side from the potential plate;
A lower space which is a space on the sample side from the potential plate;
A mechanism for vacuum-separating the upper space and the lower space;
The charged particle beam apparatus according to claim 3 , further comprising a gas introduction mechanism that retains the gas in the vicinity of the sample by introducing the gas into the lower space. It is disposed on the surface of the potential plate facing the shield electrode so as not to block the opening of the potential plate, and includes a detector for detecting signal electrons or electromagnetic waves emitted from the sample. The charged particle beam apparatus according to any one of claims 1 to 4 . The charged particle beam apparatus according to any one of claims 2, 3 , 5, and 6 , wherein the shield electrode is connected to a conductor connected to the sample stage. The charged particle beam apparatus according to claim 7 , wherein the shield electrode and the conductor constitute a sample case placed on the sample stage so as to cover the sample. The sample case is a sealed container,
A thin film member is provided so as to close the opening of the shield electrode,
9. The charged particle beam apparatus according to claim 8 , wherein the thin film member is made of a material that allows the signal electrons or electromagnetic waves emitted from the charged particle beam and the sample to pass therethrough. The charged particle beam apparatus according to claim 3 , wherein the potential plate is a magnetic pole of the upper objective lens facing the shield electrode. The arrangement configuration of the upper portion of the sample is determined so that a space for performing processing on the sample including at least one of operation, processing, or measurement on the sample is secured on the lower objective lens. The charged particle beam device according to any one of claims 2, 3, and 5 , wherein 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 onto the sample;
A sample stage on which the sample is placed;
A shield electrode that allows the charged particle beam to pass therethrough and a potential plate;
From the sample stage side, the shield electrode and the potential plate are arranged in this order,
A potential difference is given between the sample stage and the potential plate,
A potential that relaxes the electric field generated in the sample due to the potential difference is applied to the shield electrode,
The objective lens is
A lower objective lens disposed on the opposite side of the charged particle beam to the sample;
An upper objective lens disposed on the side on which the charged particle beam is incident on the sample, different from the objective lens,
A charged particle beam apparatus, further comprising a detector that is disposed below the upper objective lens and detects signal electrons emitted from the sample when the charged particle beam is irradiated on the sample. A scanning electron microscope comprising the charged particle beam device according to any one of claims 1 to 12 .

Images