WO2024180669A1

WO2024180669A1 - Charged particle beam device

Info

Publication number: WO2024180669A1
Application number: PCT/JP2023/007352
Authority: WO
Inventors: 恵理齊藤; 信裕岡井; 直正鈴木; 哲也新堀; 竜己服部
Original assignee: 株式会社日立ハイテク
Priority date: 2023-02-28
Filing date: 2023-02-28
Publication date: 2024-09-06

Abstract

In the present invention, the visibility of a region which is difficult to observe can be improved. A charged particle beam device 100 irradiates a sample with a charged particle beam 121 to obtain an observation image of the sample. The charged particle beam device 100 comprises: an electron gun 101 that emits a primary electron beam 121; and an energy discriminator 200 disposed between the electron gun 101 and a sample 111, and having a first region for discriminating, in accordance with energy, signal particles 122 emitted from the sample 111 irradiated with the charged particle beam 121, and a second region that allows signal particles 122 to pass therethrough.

Description

Charged Particle Beam Device

This disclosure relates to charged particle beam devices.

As semiconductor devices become more miniaturized and 3D devices are developed, the number of areas where signal detection is difficult, such as the bottom of deep trench patterns, is increasing, and there is a growing need to observe these areas. For this reason, scanning electron microscopes (SEMs) used to inspect and measure semiconductor devices are required to have higher sensitivity and precision than ever before.

In order to inspect and measure the bottom of a groove pattern, it is effective to selectively detect only electrons emitted in a specific direction from among the electrons emitted from the sample. To achieve this, a configuration is required that suppresses the detection of electrons emitted from anywhere other than the bottom, while efficiently detecting electrons emitted from the bottom.

Patent document 1 describes a method in which holes are created in a reflector plate for electrons to pass through, and a secondary electron deflector installed below the reflector deflects the electrons of the desired component so that they pass through the holes, and after passing through the reflector, they are deflected by another secondary electron deflector to reach a detector.

Patent No. 6820660

The technology of Patent Document 1 mentioned above makes it possible to limit the detection range of electrons by deflecting the electrons emitted from the sample and passing them through holes formed in the reflector. However, with the technology of Patent Document 1 mentioned above, electrons escape through the holes in the reflector, so a deflector is needed to change the electrons that have passed through the holes in the reflector, and a detector is needed to detect the electrons that have passed through the holes in the reflector, making the device configuration complicated.

The present disclosure aims to solve the above problems and provide a charged particle beam device that uses an energy discriminator to improve the visibility of areas that are difficult to observe.

In order to solve the above problems, the charged particle beam device disclosed herein is a charged particle beam device that irradiates a sample with a charged particle beam to obtain an observation image of the sample, and includes a charged particle beam source that emits the charged particle beam, and an energy discriminator that is disposed between the charged particle beam source and the sample and has a first region that discriminates signal particles emitted from the sample irradiated with the charged particle beam according to their energy, and a second region that allows the signal particles to pass.

According to the present disclosure, an energy discriminator can be used in a charged particle beam device to improve visibility of areas that are difficult to observe.

　Problems, configurations and advantages other than those mentioned above will become clear from the description of the embodiments below.

1 is a diagram showing an overall configuration of a charged particle beam apparatus according to a first embodiment. FIG. 2 is a diagram illustrating an energy filter according to the first embodiment. FIG. 2 is a diagram illustrating an energy filter according to the first embodiment. FIG. 11 is a diagram showing the relationship between the number of signal particles passing through the energy filter of the first embodiment and the negative voltage VEF. FIG. 11 is a diagram showing the relationship between the number of signal particles passing through the energy filter of the first embodiment and the negative voltage VEF. 1A to 1C are diagrams illustrating the trajectories of electrons emitted from the upper layer and the bottom of the groove of the sample in Example 1. 4A and 4B are diagrams for explaining the azimuth angle and elevation angle of electrons emitted from the sample in Example 1. 4 is a diagram illustrating the distribution on the reflector of signal particles that have reached the reflector from the surface layer of the sample in Example 1. FIG. 10 is a diagram illustrating the distribution on the reflector of signal particles that have reached the reflector from the bottom of the groove of the sample in Example 1. FIG. 1 is a diagram illustrating the detection range of all signal particles that have reached a reflector from a surface layer of a sample in Example 1. FIG. 1 is a diagram illustrating the detection range of all signal particles that reach the reflector from the groove bottom of the sample in Example 1. FIG. 13 is a diagram showing the visibility of the groove bottom when all signal particles that reach the reflector of Example 1 are detected. FIG. 13 is a diagram showing the visibility of the groove bottom when all signal particles that reach the reflector of Example 1 are detected. FIG. 1 is a diagram for explaining a detection range including many signal particles from the bottom of a groove among signal particles that reached a reflector from a surface layer of a sample in Example 1. FIG. 10 is a diagram for explaining the detection range of signal particles from the bottom of the groove among signal particles that reach the reflector from the bottom of the groove of the sample in Example 1. FIG. 13 is a diagram showing the visibility of the groove bottom when only a detection range containing a large number of signal particles from the groove bottom among signal particles that have reached the reflector of Example 1 is detected. FIG. 13 is a diagram showing the visibility of the groove bottom in the case where only a region containing a large number of signal particles from the groove bottom among the signal particles that have reached the reflector of Example 1 is detected. FIG. FIG. 2 is a diagram showing an example of an energy filter capable of azimuth angle discrimination according to the first embodiment; 13 is a diagram showing a laminated structure of an energy filter capable of azimuth angle discrimination according to a second embodiment of the present invention; FIG. 13 is a diagram showing the structure of each grid of an energy filter capable of azimuth angle discrimination according to the second embodiment. FIG. FIG. 13 is a diagram showing a layered structure of an energy filter capable of azimuth angle discrimination according to Modification 1 of the second embodiment. 13 is a diagram showing the structure of each grid of an energy filter capable of azimuth angle discrimination according to modified example 1 of the second embodiment; FIG. FIG. 13 is a diagram showing the structure of each energy filter grid of the second modified example of the second embodiment. FIG. 13 is a diagram showing a structure of an energy filter grid according to a third modified example of the second embodiment. FIG. 13 is a diagram showing a structure of an energy filter grid according to a third modified example of the second embodiment. FIG. 13 is a diagram showing a structure of an energy filter grid according to a third modified example of the second embodiment. FIG. 13 is a diagram showing a structure of an energy filter grid according to a third modified example of the second embodiment. 1 is a diagram showing a primary electron beam being deflected by an electric field produced by an energy filter. FIG. 13 is a diagram showing an energy filter according to a third embodiment in which a center pipe is installed. FIG. 13 is a diagram showing signal particles detected by azimuth angle discrimination in the fourth embodiment. FIG. 13 is a diagram showing signal particles detected by energy discrimination in Example 4. 13A and 13B are diagrams illustrating a discrimination method in which azimuth angle discrimination and energy discrimination are combined in the fourth embodiment. 13A and 13B are diagrams illustrating a discrimination method in which azimuth angle discrimination and energy discrimination are combined in the fourth embodiment. FIG. 13 is a diagram showing the positional relationship between a reflector and an energy filter in the fifth embodiment. FIG. 1 is a diagram showing the shape of a typical reflector. FIG. 13 is a diagram showing the shape of a reflector according to a fifth embodiment. 13A and 13B are diagrams illustrating an azimuth angle discrimination method using a reflector according to a fifth embodiment. FIG. 13 is a diagram showing a configuration in which a reflector and an energy filter are combined according to a fifth embodiment. FIG. 23 is a diagram showing an example of an energy filter capable of azimuth angle discrimination and elevation angle discrimination according to the sixth embodiment. FIG. 23 is a diagram showing an example of an energy filter grid capable of elevation angle discrimination according to a modified example of the sixth embodiment. FIG. 13 is a diagram showing an example of the structure of a rotatable energy filter grid according to a seventh embodiment. FIG. 23 is a diagram showing an example of an energy filter grid in which the voltage of each of a plurality of mesh electrodes of Example 8 can be controlled.

The embodiments of the present disclosure will be described in detail with reference to the drawings. It goes without saying that in the following embodiments, the configurations (including the steps of the flow chart) are not necessarily essential unless specifically stated or considered to be obviously essential in principle. Below, preferred examples of the present disclosure will be described with reference to the drawings.

The first embodiment will be explained using Figures 1 to 8.

(Charged particle beam device 100)
First, the overall configuration of a charged particle beam device 100 will be described with reference to FIG. 1. The charged particle beam device 100 of the first embodiment is an electron microscope. The charged particle beam device 100 irradiates a sample 111 with a charged particle beam to obtain an observation image of the sample 111. The charged particle beam device 100 includes an electron gun 101, a condenser lens 102, a condenser lens 103, an aperture 104, a reflector 105, an ExB deflector 106, a detector 107, a deflector 108, a deflector 109, an objective lens 110, a sample stage 112, a retarding power supply 113, a display 114, a storage device 115, and a control device 120. The control device 120 is a device that controls the operation of each part, and is a computer system having a processor, a memory, and the like. The storage device 115 stores a control table 116 that defines control conditions such as voltage and current of each part. The control device 120 may read the control table 116 from the storage device 115 and control each part based on the control conditions defined in the control table 116 .

The electron gun 101 is an electron source that emits electrons. The electron gun 101 is an example of a charged particle beam source in this disclosure. A negative voltage of, for example, 3000 V is applied to the electron source. The condenser lens 102 and the condenser lens 103 are lenses that focus the primary electron beam 121. The aperture 104 is a member that determines the aperture angle of the primary electron beam 121 in the objective lens 110, and has an aperture through which the primary electron beam 121 passes. The

deflectors

108 and 109 deflect the primary electron beam 121 to scan it over the sample 111.

The objective lens 110 is a lens that focuses the deflected primary electron beam 121, and thins the primary electron beam 121 by a magnetic field generated by a current flowing through an internal coil.

The sample stage 112 holds the sample 111 and controls the position and attitude of the sample 111. That is, the sample stage 112 moves the sample 111 horizontally or vertically, and rotates it around the vertical axis. A retarding power supply 113 for applying a voltage to the sample stage 112 is connected to the sample stage 112. By applying a negative voltage of several kV to the sample stage 112, an electric field that decelerates the primary electron beam 121 is formed between the sample 111 and the objective lens 110. When the decelerated primary electron beam 121 is irradiated onto the sample 111, signal particles 122 are emitted from the sample 111. In general, signal particles emitted with an energy of 50 eV or less are called secondary electrons, and signal particles emitted with an energy of more than 50 eV and close to the energy of the primary electron beam 121 are called reflected electrons.

The electric field that slows down the primary electron beam 121 also works to accelerate the signal particles 122 generated on the sample 111. The signal particles 122 that move upward collide with the reflector 105. When the signal particles 122 collide with the reflector 105, tertiary electrons 123 are emitted from the reflector 105. The tertiary electrons 123 are deflected by the electric field and magnetic field in the ExB deflector 106 and detected by the detector 107. Note that the electric field and magnetic field in the ExB deflector 106 also act on the primary electron beam 121, but since the effects of the two cancel each other out on the primary electron beam 121, the primary electron beam 121 travels straight toward the sample 111.

The charged particle beam device 100 further includes an energy filter 200. The energy filter 200 is installed directly below the ExB deflector 106, and is capable of discriminating the signal particles 122 according to their energy.

(Energy Filter 200)
The structure of the energy filter 200 will be described with reference to FIGS. 2A and 2B. The energy filter 200 is an example of an energy discriminator of the present disclosure. The energy filter 200 is disposed between the electron gun 101 and the sample 111. As shown in FIG. 2A, the energy filter 200 has a grounded conductor grid 201, an energy filter grid 202 to which a voltage can be applied, and an energy filter power supply 203 connected to the energy filter grid 202 so as to apply a voltage. The conductor grid 201 is disposed above and below the energy filter grid 202. As shown in FIG. 2B, the conductor grid 201 and the energy filter grid 202 have mesh electrodes 204 disposed on mesh fixing beams 205. The mesh electrodes 204 of both the conductor grid 201 and the energy filter grid 202 are provided with holes 210 through which the primary electron beam 121 passes.

A potential barrier is formed by applying a negative voltage VEF to the energy filter grid 202 by the energy filter power supply 203. Of the signal particles 122 that enter the energy filter 200, signal particles 124 that have an energy E lower than the potential barrier are bounced off, and only signal particles 122 that have an energy E higher than the potential barrier pass through the energy filter 200 and collide with the reflector 105. Tertiary electrons 123 generated by the reflector 105 are then detected by the detector 107.

(Relationship between the voltage applied to the energy filter 200 and the number of signal particles passing through the energy filter 200)
Here, with reference to Figures 3A and 3B, how the number of signal particles passing through the energy filter 200 changes depending on the negative voltage VEF applied to the energy filter 200 will be described. As shown in Figure 3A, in energy discrimination, it is ideal to not detect any electrons whose energy is smaller than the negative voltage VEF, and to detect all electrons whose energy exceeds the negative voltage VEF. If there is only one energy filter grid 202, as shown in Figure 3B, electrons whose energy is lower than the negative voltage VEF are also detected, resulting in a decrease in energy discrimination performance. In order to prevent this, it is preferable to install two or more energy filter grids 202. Here, the energy filter grid 202 may be one or more.

(Detection range of signal particles 122)
In the observation of semiconductor devices, there is an increasing need to observe areas where signal detection is difficult, such as the bottom of a groove pattern. For shape observation and inspection of the bottom of a groove pattern, it is effective to detect only secondary electrons emitted in a specific direction. The reason for this will be explained using Figures 4A to 7D.

One of the reasons why it is difficult to observe the groove bottom 401 of the groove pattern 400 is that there are fewer signal particles 122 emitted from the groove bottom 401 compared to the signal particles 122 emitted from the surface layer 410. Figure 4A shows the trajectory of the signal particles 122 emitted from the groove bottom 401 of the groove pattern 400. Of the signal particles 122 emitted from the groove bottom 401 of the groove pattern 400, those that collide with the wall surface 402 of the groove pattern 400 do not reach the detector 107, so the only signal particles 122 that can be detected from the groove bottom 401 are those emitted in a direction where there are no wall surfaces 402.

Here, as shown in FIG. 4B, the X-axis and Y-axis are taken in the planar direction, and the Z-axis is taken in the direction of the beam optical axis, and the angle between the emission direction of the signal particle 122 and the Z-axis is defined as the elevation angle 131, and the angle between the emission direction of the signal particle 122 and the X-axis is defined as the azimuth angle 132. A discrimination method in which the signal particles 122 are discriminated by the elevation angle 131 and only signal particles 122 emitted near directly above the sample 111 are detected is called elevation angle discrimination, and a discrimination method in which the signal particles 122 are discriminated by the azimuth angle 132 and only signal particles 122 emitted in a specific direction, such as the longitudinal direction of the groove pattern 400, are detected is called azimuth angle discrimination.

5A and 5B show the distribution of signal particles 122 emitted from the sample 111 and reaching the reflector 105. For the signal particles 122 emitted from the surface layer 410, there is no obstacle such as the wall surface 402 on the trajectory to reach the reflector 105, so the signal particles 122 emitted in any direction reach the reflector 105 and are distributed isotropically as shown in FIG. 5A. On the other hand, the signal particles 122 emitted from the groove bottom 401 that collide with the wall surface 402 do not reach the reflector 105, so as shown in FIG. 5B, they are distributed elongated in one direction corresponding to the longitudinal direction of the groove pattern 400 where there are no walls. In the example of FIG. 5A and FIG. 5B, all the signal particles 122 that reach the reflector 105 are detected.

FIG. 6A shows a detection range 600 of signal particles 122 reaching the reflector 105 from the surface layer 410, and FIG. 6B shows a detection range 600 of signal particles 122 reaching the reflector 105 from the groove bottom 401. In this detection range 600, as shown in FIG. 6C, there is a large difference in the detection amount between the groove bottom 401 and the surface layer 410. If an SEM image is created in this state, the minute changes in the signal amount at the groove bottom 401 are not displayed on the observation image as differences in gradation values, as shown in FIG. 6D.

Therefore, as shown in Figures 7A and 7B, the detection range 700 is limited to only the area containing many signal particles 122 from the groove bottom 401. This makes it possible to reduce the signal particles 122 from the surface layer 410 while maintaining the detection amount of signal particles 122 from the groove bottom 401 as shown in Figure 7C, and the detection amount of signal particles 122 from the groove bottom 401 approaches the detection amount of the surface layer 410. When an SEM image is created in this state, minute changes in the signal amount are emphasized as shown in Figure 7D, and the signal amount change at the groove bottom 401 can be confirmed as contrast on the image.

It is effective to limit the detection range by the elevation angle and detect only the signal particles 122 emitted near the area directly above the sample 111, but if there are no walls in the longitudinal direction of the groove pattern 400, etc., it is more effective to limit the detection range to a long distance in one direction as shown in Figures 7A and B, which allows a relatively large number of signal particles 122 to be detected from the groove bottom 401.

(Azimuth Angle Discrimination by Energy Filter 200)
In the first embodiment, a method is proposed in which an energy filter 200 is used to detect only signal particles 122 emitted in a specific elongated direction that corresponds to the longitudinal direction of a groove pattern 400. This method will be described with reference to FIG.

As shown in FIG. 8, the mesh electrode 204 installed on the energy filter grid 202 is divided into, for example, four parts in the circumferential direction, and only specific diagonal parts are installed on the mesh fixing beam 205. When a negative voltage VEF is applied to the energy filter grid 202, a potential barrier is formed only in the area AR1 (first area) where the mesh electrode 204 is installed. Signal particles 122 emitted into the area AR1 where the mesh electrode 204 is installed are repelled by the potential barrier and do not reach the detector 107. In addition, it becomes possible to detect only the signal particles 122 emitted into the area AR2 (second area) where the mesh electrode 204 is not installed, and azimuth angle discrimination can be achieved.

In FIG. 8, two divided mesh electrodes 204 are arranged horizontally, and a structure that can observe the groove bottom 401 of a groove pattern 400 that extends vertically is shown as an example. The installation position of the mesh electrode 204 can be freely determined, such as vertically or diagonally, depending on the longitudinal direction of the groove pattern 400 that is the observation target. The mesh electrode 204 of the conductor grid 201 is not divided.

(Effects of Example 1)
As shown in Fig. 8, by providing an area AR1 for discriminating the signal particles 122 according to their energy and an area AR2 for passing the signal particles 122 in the energy filter grid 202, it is possible to reduce the signal particles 122 from the area corresponding to the area AR1 (e.g., the surface layer 410) while maintaining the detection amount of the signal particles 122 from the area corresponding to the area AR2 (e.g., the groove bottom 401). As a result, the detection amount of the signal particles 122 from the area corresponding to the area AR2 approaches the detection amount of the signal particles 122 from the area corresponding to the area AR1. When an SEM image is created in this state, as shown in Fig. 7D, minute changes in the signal amount are emphasized, and the signal amount changes in the area corresponding to the area AR2 can be confirmed as contrast on the image.

Next, Example 2 will be described with reference to Figures 9A to 12D. Note that matters described in Example 1 but not described in Example 2 are also applicable to Example 2 unless there are special circumstances.

In the energy filter 200 shown in the first embodiment, the direction in which the signal particles 122 can be discriminated is fixed to the direction in which the mesh electrode 204 of the energy filter grid 202 is installed, and is limited to one specific direction, such as only the vertical direction. Therefore, in the second embodiment, as shown in FIG. 9A, the energy filter grids 202 are stacked in the optical axis direction. As shown in FIG. 9B, the area AR1 in which the mesh electrode 204 of the energy filter grid 202 is provided limits the azimuth angle range of the signal particles 122, which differ from one another for each energy filter grid 202. Specifically, in the first energy filter grid 202, the area AR1 in which the mesh electrode 204 is installed is, for example, horizontal, and in the second energy filter grid 202, the area AR1 in which the mesh electrode 204 is installed is, for example, vertical. Between each energy filter grid 202, an insulating member 206 is installed to insulate the mesh electrodes 204, and a structure is provided in which a negative voltage VEF of any magnitude can be applied to each energy filter grid 202. When discriminating the azimuth angle of the signal particle 122, a negative voltage VEF is applied to one of the energy filter grids 202 in accordance with the pattern on the sample 111.

(Modification 1 of Example 2)
10A and 10B , in addition to the energy filter grid 202 having the mesh electrodes 204 in the vertical direction and the energy filter grid 202 having the mesh electrodes 204 in the horizontal direction, two types of energy filter grids 202 having mesh electrodes 204 in the diagonal direction may be added, so that a total of four energy filter grids 202 are stacked via insulating members 206. This enables azimuth angle discrimination in the diagonal direction in addition to the vertical and horizontal directions.

(Modification 2 of Example 2)
In addition, while the mesh electrode 204 has been divided into four and two opposing pieces have been provided in the above examples, it may be divided into more than four pieces as shown in Fig. 11. In the case of Fig. 11, no voltage is applied to only the energy filter grid 202 in which the mesh electrode 204 is installed in the area to be detected, and a negative voltage VEF is applied to the other energy filter grids 202, thereby achieving azimuth angle discrimination.

(Modification 3 of Example 2)
The mesh electrode 204 installed on the energy filter grid 202 may have any shape as long as it is installed so that only the signal particles 122 emitted in a specific direction can be detected. Examples of the installation of the mesh electrode 204 are shown in Figs. 12A to 12D. In the energy filter grid 202 of Fig. 12A, only half of the mesh electrode 204 is installed, and the signal particles 122 emitted to either the left or right or the top or bottom can be discriminated. This makes it possible to observe the side of a pattern with a height in the optical axis direction, for example. In the energy filter grid 202 of Fig. 12B, by installing a divided mesh electrode 204 for each energy filter grid 202, the discriminable area can be freely changed according to the pattern, such as half discrimination as in Fig. 12A, not just in the diagonal direction. In the energy filter grid 202 of Fig. 12C, the mesh electrode 204 of Fig. 12B is further divided into eight parts, so that the detection range can be narrowed further. In the energy filter grid 202 of FIG. 12D, in accordance with the elongated distribution of the signal particles 122 emitted from the groove bottom 401, the mesh electrodes 204 are not only divided in the circumferential direction but also arranged vertically.

(Effects of Example 2)
In the second embodiment, a plurality of energy filter grids 202 are stacked in the optical axis direction, and the directions in which the mesh electrodes 204 are installed are different for each energy filter grid 202, thereby making it possible to discriminate the azimuth angles of the signal particles 122 in accordance with the pattern, etc., of the sample 111.

The third embodiment will be described with reference to Figs. 13 and 14. Note that matters described in the first and second embodiments but not described in the third embodiment can also be applied to the third embodiment unless there are special circumstances.

Since a negative voltage VEF of several kV is applied to the energy filter grid 202, in the configuration of the energy filter 200 described above, when the primary electron beam 121 passes through the center of the energy filter 200 as shown in FIG. 13, it is deflected by the effect of the electric field of the energy filter grid 202. Therefore, in the third embodiment, a metallic center pipe 207 is installed at the center of the energy filter 200 as shown in FIG. 14. By installing the center pipe 207, even if a voltage is applied to the energy filter grid 202, the primary electron beam 121 can pass through the energy filter 200 without being affected. The diameter of the center pipe 207 is about 1 mm. In FIG. 14, the center pipe 207 is connected to both of the two conductor grids 201 installed, but it can also be connected to only one of them.

(Effects of Example 3)
By providing the center pipe 207, the primary electron beam 121 is not affected by the electric field of the energy filter 200. This eliminates the effect on the beam diameter of the primary electron beam 121, and has the effect of reducing positional deviation and focus blur on the sample 111. Even if the negative voltage VEF applied to the energy filter grid 202 by the energy filter power supply 203 is changed, there is no need to correct the position or focus, and the optimal applied voltage conditions can be smoothly searched for.

Example 4 will be described with reference to Figures 15A to 16B. Note that matters described in Examples 1 to 3 but not described in Example 4 are also applicable to Example 4 unless there are special circumstances.

As described in Example 2, a voltage can be applied to each of the energy filter grids 202, and the voltage applied can be changed arbitrarily for each energy filter grid 202. By changing this applied voltage VEF, in addition to discrimination based on the emission direction of the signal particles 122, it is possible to perform energy discrimination as in the conventional method.

As shown in FIG. 15A, the azimuth discrimination of the signal particles 122 described above discriminates the signal particles 122 according to their azimuth direction. All signal particles 122 emitted into the detectable area pass through. Furthermore, a conventional energy filter discriminates the energy according to the energy of the signal particles 122, as shown in FIG. 15B. It is configured to pass through all signal particles 122 that have energy equal to or greater than the negative voltage VEF set by the energy filter power supply 203.

As shown in FIG. 16A, by combining discrimination based on the emission direction of the signal particles 122 and discrimination based on the magnitude of energy, it is possible to detect only signal particles 122 that are emitted in a specific direction and have high energy, such as backscattered electrons. In the azimuth angle discrimination in the above-mentioned embodiment, no voltage was applied to the mesh electrode 204 in the area to be detected. In this embodiment 4, however, by applying a negative voltage Ve to the mesh electrode 204 in the area to be detected of the energy filter grid 202, it is possible to pass only signal particles 122 that have energy equal to or greater than the applied negative voltage Ve. At this time, the applied negative voltage Ve is a value smaller than the negative voltage VEF applied to the mesh electrode 204 in the area not to be detected for azimuth angle discrimination. Also, by applying a negative voltage Ve to all the energy filter grids 202, it is possible to perform energy discrimination in the same way as in the conventional case.

Furthermore, by applying no voltage to one energy filter grid 202, applying a negative voltage Ve to one of the remaining energy filter grids 202, and applying a negative voltage VEF to the other energy filter grids 202, as shown in FIG. 16B, it becomes possible to distinguish such that all signal particles 122 in the direction of the energy filter grid 202 to which no voltage is applied are detected, and only signal particles 122 having energy equal to or greater than Ve are detected in the direction of the energy filter grid 202 to which the negative voltage Ve is applied, while other signal particles 122 are not detected.

(Effects of Example 4)
In the fourth embodiment, by controlling the voltage applied to the mesh electrode 204, it becomes possible to perform energy discrimination as in the conventional case, in addition to azimuth angle discrimination based on the emission direction of the signal particles 122.

The fifth embodiment will be described with reference to Figures 17 to 20. Note that matters described in the first to fourth embodiments but not described in the fifth embodiment can also be applied to the fifth embodiment unless there are special circumstances.

As shown in FIG. 17, a reflector 105 is installed on the top of the energy filter 200. The reflector 105 is an example of a conversion electrode of the present disclosure. The signal particles 122 that pass through the energy filter 200 collide with the reflector 105, and the generated tertiary electrons 123 (secondary signal particles) are detected by the detector 107.

A typical reflector 105 is a circular metal plate with a hole in the center through which the primary electron beam 121 passes, as shown in Figure 18A.

In Example 5, the reflector 105 is divided to perform azimuth discrimination of the signal particles 122. First, the reflector 105 is divided in the circumferential direction as shown in Figure 18B. Each of the divided regions 105a to 105h of the reflector 105 is installed so as not to come into contact with each other, and a voltage can be applied to each of them. An arbitrary positive voltage Vh is applied to regions other than the region to be detected, and no voltage is applied to the region to be detected.

Figure 19 shows the trajectories of signal particles 122 that collide with the divided reflector 105 and tertiary electrons 123 generated on the reflector 105. The tertiary electrons 125 generated in the area where the positive voltage Vh is applied are pulled back to the reflector 105 by the applied positive voltage Vh and do not reach the detector 107. On the other hand, only the tertiary electrons 123 generated by collision with the area where no voltage is applied are detected by the detector 107.

(Effects of Example 5)
20, by using the reflector 105 and the energy filter 200 together, the signal particles 122 can be discriminated twice. As described in the fourth embodiment, since the energy filter 200 can also perform energy discrimination, it is possible to discriminate, for example, secondary electrons by the energy filter 200 and reflected electrons by the reflector 105.

The sixth embodiment will be described with reference to FIG. 21. Note that matters described in the first to fifth embodiments but not described in the sixth embodiment can also be applied to the sixth embodiment unless there are special circumstances.

In observing groove patterns, in addition to azimuth angle discrimination, elevation angle discrimination, which detects signal particles 122 emitted near directly above the sample 111, is also an effective means. Using Figure 21, we will explain an energy filter 200 that can perform both azimuth angle discrimination and elevation angle discrimination.

By combining an elevation angle discrimination energy filter grid 208 having a different size of central area with an energy filter grid 202 on which divided mesh electrodes 204 are installed for azimuth angle discrimination, elevation angle discrimination is possible in addition to azimuth angle discrimination. The elevation angle discrimination energy filter grid 208 for elevation angle discrimination limits the range of elevation angle directions of the signal particles 122. The elevation angle discrimination energy filter grid 208 (second energy filter grid) has a central area AR3 larger than the central area AR3 of the energy filter grid 202 for azimuth angle discrimination (first energy filter grid).

In addition, as shown in FIG. 21B, the elevation angle discrimination energy filter grid 208 may have a central area AR3 that is an opening near the center, and a mesh electrode 204 may be provided around the entire outer periphery of the central area AR3.

(Effects of Example 6)
When performing elevation angle discrimination, a negative voltage VEF is applied to the elevation angle discrimination energy filter grid 208, which has a large central area AR3, to bounce back the signal particles 124, making it possible to detect only the signal particles 122 emitted near the center that pass between the elevation angle discrimination energy filter grid 208 and the center pipe 207.

By combining azimuth angle discrimination and elevation angle discrimination, it is possible to detect signal particles emitted in a specific direction within a narrow elevation angle range. In addition, as explained in Example 4, energy discrimination is also possible by changing the applied voltage VEF of the energy filter grid 202, making it possible to detect, for example, only reflected electrons within a specific elevation angle range.

Example 7 will be explained with reference to FIG. 22. Note that matters described in Examples 1 to 6 but not described in Example 7 are also applicable to Example 7 unless there are special circumstances.

The energy filter 200 has a structure in which the energy filter grid 202 on which the divided mesh electrodes 204 are installed can be rotated. In the structures described up to Example 6, the area in which the mesh electrodes 204 are installed cannot be changed after the energy filter 200 is installed in the electron microscope. Therefore, as shown in FIG. 22, a rotation mechanism 209 is installed on the energy filter grid 202 to provide a mechanism that can rotate the energy filter grid 202. The rotation mechanism 209 in Example 7 rotates the energy filter grid 202 to displace the area AR1 in which the mesh electrodes 204 are installed and the area AR2 of the opening, but the areas AR1 and AR2 may be displaced by a mechanism other than the rotation mechanism 209. The rotation mechanism 209 is an example of a displacement means of the present disclosure.

(Effects of Example 7)
By using this rotation mechanism 209, the region where the mesh electrode 204 is installed can be moved, and the discrimination region can be changed even after the energy filter 200 is incorporated into the electron microscope. In addition, by using this rotation mechanism 209, the discrimination region can be finely adjusted to match the pattern of the sample 111.

This rotation mechanism 209 may be any mechanism that can change the area in which the mesh electrode 204 is installed after the energy filter 200 is installed. In FIG. 22, the energy filter grid 202 is rotated, but for example, the entire energy filter 200 may be rotated.

Example 8 will be described with reference to FIG. 23. Note that matters described in Examples 1 to 7 but not described in Example 8 are also applicable to Example 8 unless there are special circumstances.

As shown in FIG. 23, the mesh electrodes 204 installed on the energy filter grid 202 are divided into, for example, eight parts in the circumferential direction, and a negative voltage VEF can be applied to each mesh electrode 204. When a negative voltage VEF is applied to a desired mesh electrode 204, a potential barrier is formed only in the area where the mesh electrode 204 to which the negative voltage VEF is applied is installed. Signal particles 122 emitted in the direction where the mesh electrode 204 is installed are repelled by the potential barrier and do not reach the detector 107, and it becomes possible to detect only the signal particles 122 emitted in the direction where the mesh electrode 204 to which the negative voltage VEF is not applied is installed, thereby achieving azimuth angle discrimination.

(Effects of Example 8)
By using the energy filter grid 202 of Example 8, it is possible to realize an energy filter having various potential barriers (e.g., FIG. 11 and FIGS. 12A to 12C) with a single energy filter grid 202 by controlling the application of a negative voltage VEF to the multiple mesh electrodes 204.

Note that this disclosure is not limited to the above examples, and includes various modified examples. The above examples have been described in detail to clearly explain this disclosure, and are not necessarily limited to those having all of the configurations described. It is also possible to replace part of the configuration of one example with the configuration of another example, and it is also possible to add the configuration of another example to the configuration of one example. It is also possible to add, delete, or replace part of the configuration of each example with other configurations.

101: electron source (charged particle beam source), 102: condenser lens, 103: condenser lens, 104: aperture, 105: reflector, 106: ExB deflector, 107: detector, 108: deflector, 109: deflector, 110: objective lens, 111: sample, 112: sample stage, 113: returning power supply, 114: display, 115: storage device, 116: control table, 120: control device, 121: primary electron beam, 122: signal particle, 123: tertiary electron, 124: (bounced by energy filter and not detected) signal particle, 125: (pulled back by split reflector and not detected) tertiary electron, 1 31: elevation angle, 132: azimuth angle, 200: energy filter (energy discriminator), 201: conductor grid, 202: energy filter grid, 203: energy filter power supply, 204: mesh electrode, 205: mesh fixed beam, 206: insulating member, 207: center pipe, 208: elevation angle discrimination energy filter grid, 209: rotation mechanism (displacement means), 210: hole, 400: groove pattern, 401: groove bottom, 402: wall surface, 410: surface layer, 600: detection range, 700: detection range (limited to the azimuth angle range), AR1: area (first area), AR2: area (second area), AR3: central area

Claims

1. A charged particle beam apparatus for irradiating a sample with a charged particle beam and obtaining an observation image of the sample, comprising:
a charged particle beam source that emits the charged particle beam;
an energy discriminator disposed between the charged particle beam source and the sample, the energy discriminator having a first region for discriminating signal particles emitted from the sample irradiated with the charged particle beam according to energy and a second region for passing the signal particles;
A charged particle beam device comprising:
The energy discriminator comprises:
A mesh electrode provided in the first region;
2. The charged particle beam device according to claim 1, further comprising: a power supply for applying a voltage to the mesh electrode.
The charged particle beam device according to claim 2 , wherein the second region is an opening through which the charged particle beam passes.
2. The charged particle beam device according to claim 1, wherein the first region is provided in correspondence with a direction of a groove pattern of the sample, and limits a range of an azimuthal angle direction of the signal particles.
the energy discriminator includes a plurality of energy filter grids having the first region and the second region;
The plurality of energy filter grids are stacked in the optical axis direction of the charged particle beam,
2. The charged particle beam device according to claim 1, wherein the first regions of the energy filter grids limit azimuthal ranges of the signal particles that differ from one another for each of the energy filter grids.
6. The charged particle beam device according to claim 5, wherein the plurality of energy filter grids are stacked with an insulating member interposed between the mesh electrodes.
2. The charged particle beam device according to claim 1, wherein the energy discriminator comprises a metal pipe through which the charged particle beam passes from the charged particle beam source toward the sample.
a conversion electrode with which the signal particles passing through the energy discriminator collide to generate secondary signal particles;
The charged particle beam device according to claim 1 , further comprising: a detector for detecting the secondary signal particles.
2. The charged particle beam device according to claim 1, wherein the energy discriminator comprises a first energy filter grid having the first region and the second region, and a second energy filter grid that limits a range in an elevation angle direction of the charged particle beam.
The charged particle beam device according to claim 1 , further comprising: a displacement unit for displacing the first region and the second region.