Charged particle beam device and method for controlling the charged particle beam device

Abstract

According to the present invention, reflected electrons are detected with high efficiency. This charged particle beam apparatus comprises: a charged particle source that emits a primary electron beam with which a specimen 1 is irradiated; a focusing lens that focuses the primary electron beam; an objective lens 13 that forms a first magnetic field lens 6 and a second magnetic field lens 7, in which a first main surface 6a of the first magnetic field lens 6 is disposed more on the specimen 1 side than a second main surface 7a of the second magnetic field lens 7; a detector 10 that is disposed more on the charged particle source side than the second main surface 7a of the second magnetic field lens 7; and a controller having a processor and a memory. The controller controls the focusing action of the second magnetic field lens 7 to be weaker than the focusing action of the first magnetic field lens 6, focuses signal electrons emitted from the specimen 1, and controls the quantity of the signal electrons which arrive at the detector 10.

Description

[Technical Field]

[0001] The present invention relates to a charged particle beam device and a method for controlling a charged particle beam device. [Background technology]

[0002] Generally, charged particle beam devices, such as scanning electron microscopes, scan a sample with an electron beam and detect secondary electrons or backscattered electrons generated from the sample to obtain a scanning electron microscope image. The scanning electron microscope image is used to observe, inspect, and measure minute objects.

[0003] The performance required for scanning electron microscope objective lenses varies depending on the resolution and intended use of the device. In-lens and semi-in-lens objective lenses enable high-resolution observation by leaking a magnetic field onto the sample. On the other hand, out-lens objective lenses have inferior resolution, but do not leak a magnetic field onto the sample, allowing analysis and observation in the absence of a magnetic field and are also suitable for observation at low magnifications.

[0004] Patent Document 1 discloses a scanning electron microscope equipped with both an objective lens for high-magnification observation and an objective lens for low-magnification observation.

[0005] Patent Document 2 discloses an objective lens that is composed of a plurality of magnetic poles and a plurality of coils and has a power supply that independently supplies current to the plurality of coils.

[0006] Furthermore, in order to obtain a high-contrast sample image in a scanning electron microscope, it is important to efficiently collect secondary electrons and reflected electrons emitted from the sample and to selectively collect signal electrons.

[0007] Patent Document 3 discloses a charged particle beam device that includes a first lens that controls the trajectory of signal electrons emitted from a sample, and a second lens that changes the focusing conditions of a charged particle beam according to the control conditions of the first lens. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-230464 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-41733 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-16755 Summary of the Invention [Problem to be solved by the invention]

[0009] Signal electrons generated from a sample are broadly divided into secondary electrons and backscattered electrons, each with different properties. Secondary electrons are low-energy (50 eV or less) electrons generated secondarily on the sample surface, and have the characteristic of easily reflecting the shape of the sample surface. On the other hand, backscattered electrons are high-energy electrons that are generated when electrons are irradiated onto the sample, penetrate the sample, scatter, and are then emitted outside the sample, allowing the acquisition of images that reflect information about the sample's composition.

[0010] In a scanning electron microscope, a detector is installed inside or outside the electron beam column to detect these signal electrons. The detector is installed taking into consideration the type of signal to be acquired and the yield. However, since it is necessary to avoid interference of the signal electrons with other structures, the installation location of the detector is restricted, which limits the number of detectors that can be installed and the detection efficiency of the detector.

[0011] In particular, backscattered electrons, which have high energy, are emitted from the sample on trajectories that diverge linearly except in areas where the magnetic field of the objective lens or a strong electric field is generated. In order to detect these electrons efficiently, it is generally important to install a detector close to the sample.

[0012] An object of the present invention is to detect backscattered electrons with high efficiency. [Means for solving the problem]

[0013] The charged particle beam device of the present invention comprises a charged particle source that emits a charged particle beam to be irradiated onto a sample, a focusing lens that focuses the charged particle beam, an objective lens that forms a first lens that is a magnetic lens or an electrostatic lens, and a second lens that is a magnetic lens or an electrostatic lens, and the first main surface of the first lens is arranged closer to the sample than the second main surface of the second lens, a detector that is arranged closer to the charged particle source than the second main surface of the second lens, and a controller having a processor and memory, wherein the controller controls the focusing action of the second lens to be weaker than the focusing action of the first lens, focuses signal electrons generated from the sample, and controls the amount of signal electrons that reach the detector. [Effects of the Invention]

[0014] According to the present invention, the focusing effect of the second lens makes it possible to detect reflected electrons with high efficiency. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an overview of a scanning electron microscope 100 according to a first embodiment; [Figure 2] FIG. 2 is a hardware block diagram of a control unit 25 according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing details of the objective lens 13 of the first embodiment. [Figure 4] 10 is a diagram showing the relationship between the distance from the bottom surface of the objective lens 13 and the arrival rate of backscattered electrons in Example 1. FIG. [Figure 5] FIG. 10 is a diagram showing details of an objective lens 13 and a detector 30 according to a second embodiment. [Figure 6] 10 is a diagram showing details of the objective lens 13 and the focal point of the primary electron beam 28 in the third embodiment. FIG. [Figure 7] FIG. 10 is a diagram showing a GUI according to a third embodiment. [Figure 8] FIG. 10 is a diagram showing details of an objective lens 13 and a retarding power supply 34 according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following embodiments, when necessary for convenience, the description will be divided into multiple sections or embodiments, but unless otherwise expressly stated, they are not unrelated to each other, and one is a partial or complete variation, detail, supplementary explanation, etc. of the other.

[0017] Furthermore, in the following embodiments, when referring to the number of elements (including the number, numerical value, amount, range, etc.), unless otherwise specified or when it is clearly limited to a specific number in principle, it is not limited to that specific number and may be more or less than the specific number.

[0018] Furthermore, it goes without saying that in the following embodiments, the components (including element steps, etc.) are not necessarily essential unless otherwise specified or unless they are clearly considered essential in principle.

[0019] Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of components, etc., it is intended to include those that are substantially similar or similar to those shapes, etc., unless otherwise specified or when it is considered that this is clearly not the case in principle. This also applies to the above numerical values ​​and ranges.

[0020] In addition, in all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations thereof will be omitted.

[0021] Hereinafter, an embodiment of a charged particle beam device of the present invention will be described with reference to the drawings. A charged particle beam device is a device that includes a charged particle beam source that emits a charged particle beam, a lens that focuses the charged particle beam on a sample, a detector that detects particles emitted from the sample, and a sample image that is formed using the detected signal. Below, a scanning electron microscope (SEM) will be described as an example of a charged particle beam device. [Example]

[0022] 1 is a diagram showing an overview of a scanning electron microscope (SEM) 100 of Example 1. In the following description, an SEM is used as an example, but the charged particle beam device of the present invention is not limited to an SEM, and in the following examples, a charged particle beam device other than an SEM may also be used.

[0023] The electron gun 21 for irradiating an electron beam (primary electron beam 28) includes an electron source 20, an extraction electrode 19 for extracting electrons from the electron source 20, and an acceleration electrode 18 for accelerating the electrons extracted by the extraction electrode 19 toward the sample 1. An acceleration voltage V0 is applied to the electron source 20 (charged particle source), and the primary electron beam 28 has acceleration energy V0 due to the potential difference with the acceleration electrode 18, which is at ground potential. The primary electron beam 28 emitted from the electron gun 21 is focused by a first focusing lens 17, a second focusing lens 15, and an objective lens 13, and is then irradiated onto the sample 1. In addition, an aperture 16 for limiting the irradiation amount of the primary electron beam 28 is provided between the first focusing lens 17 and the second focusing lens 15. The focusing conditions of each lens are controlled by adjusting the excitation current supplied by a lens power supply 22 (or the applied voltage in the case of an electrostatic lens).

[0024] The deflector 5 is provided to scan the primary electron beam 28 one-dimensionally or two-dimensionally on the sample 1. A signal waveform (line profile) and a two-dimensional image are generated by synchronizing a scanning signal supplied from a scanning signal generator 24 that controls the deflector 5 with an output signal from a detector (detector 10 or 14) described later. The amount of excitation current for each lens, the amplitude of the scanning signal, etc. are controlled by a control unit 25.

[0025] The scanning electron microscope 100 of FIG. 1 is equipped with two detectors: a detector 10 and a detector 14. Each of the detectors 10 and 14 detects secondary electrons (SE) or backscattered electrons (BSE) emitted from the sample 1. The detector 14 mainly directly detects secondary electrons generated from the sample 1. A conversion plate 8 having an aperture through which the primary electron beam 28 passes is installed on the optical path of the primary electron beam 28. New secondary electrons (conversion electrons 9, tertiary electrons) generated when backscattered electrons or the like collide with the conversion plate 8 are detected by the detector 10. Note that the configuration of the detectors 10 and 14 is not limited to this combination. The type, number, and arrangement of the detectors may be changed as needed. The signals output from the detectors 10 and 14 are amplified by an amplifier 23 and output to an image processing unit 26. The image processing unit 26 converts the amplified signals into signal waveforms or two-dimensional images, which are then displayed on a display device 27.

[0026] Here, a hardware configuration of the control unit 25 of the first embodiment will be described with reference to FIG. 2. FIG. 2 is a hardware block diagram of the control unit 25 of the first embodiment. As shown in FIG. 2, the control unit 25 (controller) includes a processor 251, a main memory (memory) 252, an auxiliary memory 253, and an input / output I / F 254. The processor 251 is a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), or the like. I / F stands for interface. The main memory 252 is a dynamic random access memory (DRAM), or the like. The auxiliary memory 253 is a hard disk drive (HDD), a solid state drive (SSD), or the like, and stores an adjustment program for adjusting the focusing action of the first magnetic field lens 6 and the second magnetic field lens 7, or the like. The input / output I / F 254 is communicably connected to the lens power supply 22, the scanning signal generator 24, and the image processing unit 26.

[0027] FIG. 3 is a diagram showing the details of the objective lens 13 of Example 1. The objective lens 13 has a magnetic pole 2, a first coil 3, and a second coil 4. The principal surface (first principal surface) 6a of the first magnetic field lens 6 formed by passing a current through the first coil 3 is located closer to the sample 1 than the principal surface (second principal surface) 7a of the second magnetic field lens 7 formed by passing a current through the second coil 4. In other words, the second principal surface 7a is located farther from the sample 1 (closer to the electron source 20) than the first principal surface 6a. The objective lens 13 of Example 1 is configured to form two magnetic field lenses, but it may also be configured to form a magnetic lens and an electrostatic lens, or two electrostatic lenses.

[0028] Furthermore, the objective lens 13 may be an out-lens type in which the sample 1 is placed below the objective lens 13, an in-lens type in which the sample 1 is placed inside the objective lens 13, or a semi-in-lens type which is intermediate between the two.

[0029] The objective lens 13, which forms two lenses, may switch between lenses depending on the purpose of observation. For example, when observing the sample 1 without applying a magnetic field to it, no current is passed through the first coil 3, and only the second coil 4 is passed to form only the second magnetic field lens 7, thereby focusing the primary electron beam 28 on the sample 1 (second mode). On the other hand, when observing at high magnification, current is passed through only the first coil 3, and no current is passed through the second coil 4, forming only the first magnetic field lens 6 (first mode). Furthermore, in this embodiment 1, in order for the detector 10 to detect secondary electrons or backscattered electrons with high efficiency, current is passed through both the first coil 3 and the second coil 4, forming both the first magnetic field lens 6 and the second magnetic field lens 7 (third mode). The control unit 25 switches between the first mode, second mode, and third mode according to the mode selected by the user depending on the purpose of observation.

[0030] Here, we consider the case where backscattered electrons are detected using the converter plate 8 and detector 10 when observation is performed using only the first magnetic lens 6. Backscattered electrons have high energy, equal to or lower than that of the primary electron beam 28. Some of the backscattered electrons generated from the sample 1 are directed toward the interior of the objective lens 13. When the backscattered electrons reach the first principal surface 6a of the first magnetic lens 6, they are focused by the first magnetic lens 6, causing their direction of motion to change. After passing through the first principal surface 6a, the backscattered electrons are no longer affected by magnetic or electric fields, and their trajectories 12 diverge. Only some of the electrons that reach the converter plate 8 without colliding with structures inside the objective lens 13, such as the deflector 5, are detected by the detector 10. Instead of the converter plate 8, a detector capable of directly detecting electrons, such as a semiconductor detector, may be installed. The converter plate 8 is often installed above the objective lens 13, away from the sample 1. Furthermore, structures such as the deflector 5 must be installed inside the objective lens 13, making it impossible to increase the inner diameter of the path through which the backscattered electrons pass. As a result, only a small portion of the backscattered electrons can reach the conversion plate 8.

[0031] FIG. 4 shows the results of calculating the proportion of backscattered electrons generated from the sample 1 that reach the conversion plate 8 for each distance from the bottom surface of the objective lens 13 to the conversion plate 8 when the sample 1 is observed using only the first magnetic field lens 6 of the objective lens 13 of Example 1. In this example, the sample 1 is placed at a working distance WD (see FIG. 3) of 4 mm. The calculation was performed assuming that the size of the conversion plate 8 is 10 mm in diameter. The arrival rate of backscattered electrons is nearly inversely proportional to the distance from the bottom surface (which may be the first principal surface 6 a) of the objective lens 13 to the conversion plate 8. As a result, when the conversion plate 8 is placed 10 mm from the bottom surface of the objective lens 13, 30% or more of the backscattered electrons emitted from the sample 1 reach the conversion plate 8. On the other hand, when the conversion plate 8 is placed 100 mm from the bottom surface of the objective lens 13, the arrival rate of backscattered electrons emitted from the sample 1 decreases to 3%.

[0032] Therefore, in this embodiment, a case will be described in which the focusing action of the second magnetic field lens 7 is adjusted so that backscattered electrons that have entered the objective lens 13 can reach the conversion plate 8. As shown in FIG. 3 , backscattered electrons that have passed through the first magnetic field lens 6 then diverge. However, by passing a current through the second coil 4 of the objective lens 13 in advance and forming the second magnetic field lens 7, the trajectories 11 of the diverging backscattered electrons can be focused again. In this case, in the first embodiment, the detection efficiency of backscattered electrons can be improved by adjusting the amount of current passed through the second coil 4 so that the amount of backscattered electrons that reach the conversion plate 8 is increased, or by determining and setting an optimal current amount in advance by trajectory calculation or the like.

[0033] When the second magnetic field lens 7 is formed, the lens characteristics change compared to when the primary electron beam 28 is focused on the sample 1 using only the first magnetic field lens 6. In particular, deterioration of lens characteristics such as the spherical aberration coefficient and the chromatic aberration coefficient affects the resolution of the SEM image, so it is important to change the strength of the second magnetic field lens 7 within a range where these effects are not present. Therefore, the second magnetic field lens 7 is used in a range where its focusing effect on the primary electron beam 28 is smaller than that of the first magnetic field lens 6. When the focal length of the second magnetic field lens 7 is longer than that of the first magnetic field lens 6, it can be said that the focusing effect of the second magnetic field lens 7 on the primary electron beam 28 is smaller than that of the first magnetic field lens 6.

[0034] Furthermore, the higher the rate at which backscattered electrons reach the second principal surface 7a of the second magnetic field lens 7, the more electrons can reach the conversion plate 8, so the position of the second principal surface 7a is an important parameter in designing the device. The rate at which backscattered electrons reach the conversion plate 8 versus the distance from the bottom surface of the objective lens 13 can be seen in Figure 4.

[0035] Assuming that the converter plate 8 is located 100 mm from the bottom surface of the objective lens 13, the arrival rate of backscattered electrons is approximately 3%. The arrival rate increases as the distance from the bottom surface of the objective lens 13 decreases. When improving detection efficiency by positioning the second main surface 7a of the second magnetic field lens 7 at an arbitrary position, the arrival rate of backscattered electrons to the second main surface 7a becomes important. For example, when the second main surface 7a is positioned 20 mm from the bottom surface (first main surface 6a) of the objective lens 13, the arrival rate of backscattered electrons to the second main surface 7a is approximately 18%, which is expected to improve detection efficiency by up to approximately six times.

[0036] In reality, when backscattered electrons are focused on the second principal surface 7a, some loss occurs in the number of signals that can reach the detector 10 due to differences in energy of the backscattered electrons. Considering this, a significant practical effect can be achieved if an approximately three-fold increase in the arrival rate can be expected. To achieve an approximately three-fold increase in the arrival rate, the second principal surface 7a must be positioned 40 mm or less from the lower surface of the objective lens (first principal surface 6a).

[0037] Here, a description will be given of a method for controlling the scanning electron microscope 100 of the first embodiment. The method for controlling the scanning electron microscope 100 of the first embodiment includes the following processes (1) to (4). Note that the order of the processes does not have to be the numerical order.

[0038] (1) An acceleration voltage V0 is applied to the electron gun 21, causing the electron gun 21 to emit a primary electron beam 28.

[0039] (2) A current is passed from the lens power supply 22 to the first coil 3 and the second coil 4 to form the first magnetic field lens 6 and the second magnetic field lens 7. The second main surface 7a of the second magnetic field lens 7 is disposed closer to the electron gun 21 than the first main surface 6a of the first magnetic field lens 6.

[0040] (3) The primary electron beam 28 is irradiated onto the sample 1 by the focusing effect of the first magnetic lens 6 .

[0041] (4) The focusing effect of the second magnetic field lens 7 is controlled to be weaker than the focusing effect of the first magnetic field lens 6, so that the signal electrons generated from the sample 1 are focused and reach the detector 10, which is located closer to the electron gun 21 than the second main surface 7a of the second magnetic field lens 7.

[0042] (Effects of Example 1) In the first embodiment, by forming the second magnetic field lens 7, the focusing effect of the second magnetic field lens 7 makes it possible to detect backscattered electrons (reflected electrons) with high efficiency.

[0043] Furthermore, in Example 1, by setting the distance between the first main surface 6a of the first magnetic field lens 6 and the second main surface 7a of the second magnetic field lens 7 to 40 mm or less, backscattered electrons can reach the detector 10 at a rate approximately three times higher than when the second magnetic field lens 7 is not in operation.

[0044] Furthermore, in the first embodiment, the first magnetic field lens 6 and the second magnetic field lens 7 can be switched between the first mode, the second mode, and the third mode described above depending on the purpose of observation. [Example]

[0045] In the second embodiment, a configuration for simultaneously detecting secondary electrons with high efficiency while improving the detection efficiency of backscattered electrons will be described.

[0046] 5 is a diagram showing details of the objective lens 13 of Example 2. Similar to Example 1, the objective lens 13 of Example 2 has a magnetic pole 2, a first coil 3, and a second coil 4. A detector 30 for detecting secondary electrons 29 is disposed within the objective lens 13.

[0047] Furthermore, a signal collecting electrode 31 is disposed at the tip of the objective lens 13 in order to increase the efficiency of collecting secondary electrons 29. The signal collecting electrode 31 may be a single electrode or may be configured with multiple electrodes, and is configured in consideration of the efficiency of collecting secondary electrons 29. Note that this signal collecting electrode 31 may be disposed on the objective lens 13 of the first embodiment.

[0048] Furthermore, an electrostatic deflector or a magnetic / electric field orthogonal deflector for bending the trajectory of the secondary electrons 29 toward the detector 30 may be disposed within the objective lens 13 .

[0049] As described in the first embodiment, in order to improve the detection efficiency of backscattered electrons, it is important to position the second principal surface 7a close to the bottom surface of the objective lens 13. Although it is possible to position the detector 30 that detects secondary electrons 29 between the first principal surface 6a and the second principal surface 7a, securing the mounting space for the detector 30 necessitates positioning the second principal surface 7a at a position away from the bottom surface of the objective lens 13.

[0050] Therefore, it is effective to install the detector 30 for the secondary electrons 29 closer to the electron gun 21 than the second principal surface 7a. Therefore, holes 2c for passing the detector 30 are provided in both the inner magnetic path 2a and the outer magnetic path 2b constituting the magnetic pole 2 of the objective lens 13, and the detector 30 is installed inside the objective lens 13. This shortens the flight distance of the secondary electrons 29, making it easier to control the trajectory and enabling the detector 30 to detect the secondary electrons 29 without loss.

[0051] Furthermore, at this time, if the voltage of the signal collecting electrode 31 is set so that the amount of secondary electrons detected is appropriate depending on the operating state of the objective lens 13, the loss of secondary electrons 29 can be minimized.

[0052] With this configuration, secondary electrons can be acquired simultaneously and with high efficiency while backscattered electrons are efficiently detected by the focusing action of the second magnetic field lens 7, as described in Example 1. The backscattered electrons mainly contain composition information of the sample 1, and the secondary electrons 29 mainly contain topographical information of the surface of the sample 1, so SEM images containing different information can be observed simultaneously. [Example]

[0053] In Example 3, a configuration will be described in which the focusing effect of the signal electrons at the second principal surface 7a can be freely selected to enhance the controllability of the signal electrons. The focusing effect of the second principal surface 7a affects not only the signal electrons but also the primary electron beam 28. Therefore, if the focusing effect at the second principal surface 7a is changed, it is necessary to also change the focusing effect at the first principal surface 6a. Furthermore, if the primary electron beam 28 is strongly affected by the focusing effect of the second principal surface 7a, the beam diameter of the primary electron beam 28 will also be affected. Therefore, in order to control only the trajectory of the signal electrons with a high degree of freedom, it is desirable that changing the lens strength at the second principal surface 7a has little effect on the primary electron beam 28.

[0054] 6, the primary electron beam 28 is focused on the second principal surface 7a using the second focusing lens 15. The control unit 25 controls the second focusing lens 15 so that the position of the focal point of the primary electron beam 28 irradiating the sample 1 coincides with the second principal surface 7a. As a result, the primary electron beam 28 is hardly affected by the focusing effect at the second principal surface 7a, and the trajectory of the signal electrons can be controlled at the second principal surface 7a while maintaining the characteristics of the primary electron beam 28.

[0055] 7 may be provided on the user interface (GUI) to allow the user to freely control the signal electrons. The focusing effect on the second principal surface 7a changes depending on the position of the adjustment slider 102 (information on the adjustment unit) operated by the user, and the user adjusts the adjustment slider 102 to obtain a desired image while viewing the charged particle beam image displayed on the image display unit 101.

[0056] In the example of Figure 7, an adjustment slider 102 is used to change the focusing effect on the second main surface 7a, but multiple signal detection modes may be determined in advance by calculating the trajectory of a charged particle beam, and the user may select the signal detection mode using a radio button, selection box, etc. on the GUI. [Example]

[0057] In the fourth embodiment, a mode for utilizing the present invention while retarding, which is one of the observation techniques using a scanning electron microscope, is being performed will be described.

[0058] 8 is a diagram showing details of the objective lens 13 of Example 4. The objective lens 13 of Example 4 has the same configuration as the objective lens 13 provided with the detector 30 of Example 2. In addition to the configuration of Example 2 (see FIG. 5), the device of Example 4 includes a retarding power supply 34 that applies a retarding voltage to the sample 1, and a conversion plate 32 provided above the detector 30 in the objective lens 13.

[0059] The retarding power supply 34 applies a retarding voltage so as to decelerate the primary electron beam 28 near the sample 1. This reduces the energy of the primary electron beam irradiated onto the sample 1, making this an effective observation method when it is desired to obtain information about the surface of the sample 1 or when it is desired to reduce damage to the sample 1.

[0060] During retarding, signal electrons generated from the sample 1 are accelerated by the retarding voltage and move toward the objective lens 13. The signal electrons pass through the objective lens 13 while being subjected to the focusing action of the objective lens 13 (first magnetic field lens 6 and second magnetic field lens 7), but since secondary electrons and backscattered electrons have different energies, they have different trajectories.

[0061] Furthermore, since secondary electrons and backscattered electrons contain different information about the specimen, it is desirable to acquire each of them using separate detectors.

[0062] In Example 4, by adjusting the focusing action of the second magnetic lens 7 so that the secondary electrons pass through the central hole of the conversion plate 32, it is possible to selectively detect backscattered electrons at the detector 30 in the objective lens 13 and secondary electrons at the detector 10.

[0063] Since the trajectory of the signal electrons also changes depending on the retarding voltage and the landing energy of the primary electron beam, it is desirable to control the focusing action of the second magnetic field lens 7 according to the retarding voltage and the landing energy of the primary electron beam.

[0064] It is also possible to change the signal information that can be acquired by each of the detectors 10 and 30 by controlling the focusing action of the second magnetic field lens 7. Therefore, the user may be allowed to freely change the focusing action of the second magnetic field lens 7 to adjust the contrast to a desired level, or the signal electron trajectory may be calculated in advance to provide several conditions with different detection characteristics so that the user can select the one they need.

[0065] (Variation) The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0066] 1: sample, 2: magnetic pole, 3: first coil, 4: second coil, 5: deflector, 6: first magnetic lens, 6a: first main surface, 7: second magnetic lens, 7a: second main surface, 8: conversion plate, 9: conversion electrons, 10: detector, 11: trajectory (of backscattered electrons focused by second magnetic lens 7), 12: trajectory (of backscattered electrons when second magnetic lens 7 is not used), 13: objective lens, 14: detector, 15: second focusing lens, 16: Aperture, 17: first focusing lens, 18: acceleration electrode, 19: extraction electrode, 20: electron source, 21: electron gun, 22: lens power supply, 23: amplifier, 24: scanning signal generator, 25: control unit, 26: image processing unit, 27: display device, 28: primary electron beam, 29: secondary electrons, 30: detector, 31: signal collecting electrode, 32: conversion plate, 33: backscattered electrons, 34: retarding power supply, 101: image display unit, 102: adjustment slider

Claims

1. a charged particle source that emits a charged particle beam to be irradiated onto a sample; a focusing lens that focuses the charged particle beam; an objective lens that forms a first lens that is a magnetic lens or an electrostatic lens and a second lens that is a magnetic lens or an electrostatic lens, and a first main surface of the first lens is disposed closer to the sample than a second main surface of the second lens; a detector disposed closer to the charged particle source than the second principal surface of the second lens; a controller having a processor and a memory; The controller The focusing effect of the second lens is controlled to be weaker than the focusing effect of the first lens, thereby focusing the signal electrons generated from the sample and controlling the amount of the signal electrons that reach the detector. A charged particle beam device characterized by:

2. The distance between the first main surface and the second main surface is 40 mm or less 2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

3. The controller a first mode using only the first lens; a second mode using only the second lens; a third mode in which the first lens and the second lens are used, and 2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

4. the second main surface is disposed on the charged particle source side and on the sample side of the detector; 2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

5. the objective lens includes a magnetic pole and a coil; The inner and outer magnetic paths of the magnetic pole are formed with holes for installing the other detectors.

5. The charged particle beam device according to claim 4.

6. A signal collecting electrode is disposed at the tip of the objective lens to increase the efficiency of collection of the signal electrons by the detector or the other detector.

5. The charged particle beam device according to claim 4.

7. The controller controls the focusing lens so that the position of the focal point of the charged particle beam irradiated onto the sample coincides with the second principal surface.

2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

8. a display unit that displays an adjustment unit for adjusting the focusing effect of the second lens; The controller controls the focusing action of the second lens according to information on the adjustment unit operated by a user.

2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

9. a retarding power supply that applies a retarding voltage that decelerates the charged particle beam irradiated onto the sample; The controller changes the focusing effect of the second lens in accordance with the energy of the charged particle beam and the retarding voltage.

2. The charged particle beam device according to claim 1, wherein the charged particle beam is a laser beam.

10. a charged particle source that emits a charged particle beam to be irradiated onto a sample; a focusing lens that focuses the charged particle beam; an objective lens that forms a first lens that is a magnetic lens or an electrostatic lens and a second lens that is a magnetic lens or an electrostatic lens, and a first main surface of the first lens is disposed closer to the sample than a second main surface of the second lens; a first detector disposed closer to the charged particle source than the second principal surface of the second lens; a second detector disposed on the objective lens and closer to the charged particle source than the second principal surface and closer to the sample than the first detector; A charged particle beam device characterized by:

11. The distance between the first main surface and the second main surface is 40 mm or less 11. The charged particle beam device according to claim 10.

12. the objective lens includes a magnetic pole and a coil; The inner and outer magnetic paths of the magnetic pole are formed with holes for installing the second detector.

11. The charged particle beam device according to claim 10.

13. A signal collecting electrode is disposed at the tip of the objective lens to increase the efficiency of collection of signal electrons generated from the sample by the first detector or the second detector.

11. The charged particle beam device according to claim 10.

14. A method for controlling a charged particle beam device comprising: a charged particle source that emits a charged particle beam to be irradiated onto a sample; a focusing lens that focuses the charged particle beam; an objective lens that forms a first lens that is a magnetic lens or an electrostatic lens, and a second lens that is a magnetic lens or an electrostatic lens, and in which a first main surface of the first lens is disposed closer to the sample than a second main surface of the second lens; and a detector that is disposed closer to the charged particle source than the second main surface of the second lens, emitting a charged particle beam from the charged particle source; forming the first lens; forming the second lens so that a second principal surface of the first lens is disposed closer to the charged particle source than a first principal surface of the first lens; irradiating the sample with the charged particle beam by the focusing action of the first lens; and controlling the focusing effect of the second lens to be weaker than the focusing effect of the first lens, thereby focusing signal electrons generated from the sample and controlling the amount of the signal electrons reaching the detector. A method for controlling a charged particle beam device, comprising:

15. and focusing the charged particle beam so that the position of the focal point of the charged particle beam irradiated onto the sample coincides with the second principal surface.

15. The method for controlling a charged particle beam device according to claim 14.

16. an adjustment unit for adjusting the focusing effect of the second lens is displayed on a display unit; and and controlling the focusing action of the second lens according to the adjustment unit operated by a user.

15. The method for controlling a charged particle beam device according to claim 14.

17. The focusing action of the second lens is changed in accordance with the energy of the charged particle beam and a retarding voltage that decelerates the charged particle beam irradiated onto the sample.

15. The method for controlling a charged particle beam device according to claim 14.

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