JP2019057384A - Charged particle beam device and control method of the same - Google Patents

Abstract

To provide a charged particle beam device comprising a plurality of optical elements, capable of easily reducing influence of each optical element.SOLUTION: A charged particle beam device includes: an optical system having a plurality of optical elements that occurs a magnetic field when a current is supplied; and a control part that detects a change of the current supplied to each of the plurality of optical elements, and performs a relaxation treatment against each optical element in accordance with the change of the current to be detected.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a charged particle beam apparatus and a method for controlling the charged particle beam apparatus.

  An electron microscope, such as a transmission electron microscope (TEM) or a scanning electron microscope (SEM), is an apparatus that can acquire a sample image using an electron beam. In such an electron microscope, an optical system including a plurality of electromagnetic lenses and a plurality of electromagnetic deflectors is used.

  Since such an electromagnetic lens and an electromagnetic deflector are configured to include a magnetic material, hysteresis (magnetic hysteresis) becomes a problem when the lens condition and the deflection condition are greatly changed.

  For example, Patent Document 1 describes that when the monochromator is turned on / off, a residual magnetic field is generated in the monochromator due to the hysteresis of the magnetic material, and this residual magnetic field increases the aberration of the monochromator.

  Further, for example, in Patent Document 2, in an electromagnetic deflector, an electromagnetic deflector can be provided by alternately repeating a step of flowing a maximum deflection current through a coil and a step of flowing a minimum deflection current through the coil a plurality of times. A technique for reducing the influence of hysteresis is disclosed.

JP 2006-269101 A JP 2010-123472 A

  Two methods are mainly known as methods for reducing the influence of hysteresis in optical elements such as electromagnetic lenses and electromagnetic deflectors. One of the two methods is a method of setting a target current value after periodically oscillating a current flowing through an electromagnetic lens or the like. The other of the two methods is a method of once stopping the current flowing through the electromagnetic lens or the like (after setting the current to “0”), and then setting the target current value again. Such processing for reducing the influence of hysteresis in the optical element is referred to as lens relaxation processing (lens relaxation) or simply relaxation processing.

  In recent years, the number of lenses incorporated in an electron microscope has increased due to the introduction of spherical aberration correction devices. In an electron microscope using a large number of lenses, it is necessary to reproduce the lens state adjusted in advance and obtain the best electron beam, particularly in high-resolution observation. Therefore, the reproduction error due to the hysteresis of each lens must be reduced. As a technique for reducing this reproduction error, the above-described relaxation processing is used.

  The relaxation processing is performed when the lens current is largely changed, such as when shifting from TEM observation to STEM observation (observation by scanning transmission electron microscopy). By performing relaxation processing on the electromagnetic lens, reproduction errors can be reduced, and the lens state adjusted in advance can be reproduced.

  The functions of electron microscopes in recent years have been diversified, and the lens current is greatly changed when each function is executed. As an example in which the lens current is greatly changed, in addition to switching between TEM observation (TME mode) and STEM observation (STEM mode), switching to electron diffraction (ED) mode, nano-beam diffraction (nano-beam) Examples include switching to a diffraction (NBD) mode, switching to a convergent-beam electron diffraction (CBED) mode, ON / OFF of an aberration correction device (collector), and changing an acceleration voltage.

  The electromagnetic lens and electromagnetic deflector to be subjected to the relaxation process are different for each mode. Therefore, relaxation processing must be performed on the target electromagnetic lens and electromagnetic deflector at the timing when the mode is switched. Further, depending on the mode, relaxation processing must be performed on the plurality of electromagnetic lenses and the plurality of electromagnetic lenses.

  Therefore, attaching a trigger for executing the relaxation processing for each mode is a huge work. That is, it takes time and effort to register the optical elements that perform relaxation processing for each mode and combinations thereof. Furthermore, a new mode may be added, and each time a mode is added, a trigger for executing the relaxation process must be attached. In other words, every time a mode is added, the optical elements to be subjected to relaxation processing and combinations thereof must be registered.

  Furthermore, even if the mode is not changed, there are many scenes in which the lens current is greatly changed, such as when the excitation of the objective lens is greatly changed or when the lens power is turned on / off. For this reason, there is a limit to attaching a trigger for executing the relaxation process to all scenes that require hysteresis reduction.

  The present invention has been made in view of the above-described problems, and one of the objects according to some aspects of the present invention is to provide a charged particle beam apparatus including a plurality of optical elements. An object of the present invention is to provide a charged particle beam apparatus capable of reducing the influence of hysteresis of an optical element. Further, one of the objects according to some aspects of the present invention is a method for controlling a charged particle beam apparatus including a plurality of optical elements, and can easily reduce the influence of hysteresis of the optical elements. An object of the present invention is to provide a method for controlling a charged particle beam apparatus.

The charged particle beam apparatus according to the present invention is
An optical system including a plurality of optical elements that generate a magnetic field when supplied with an electric current;
A control unit that detects a change in current supplied to each of the plurality of optical elements, and performs relaxation processing on the optical element in accordance with the detected change in current;
including.

  In such a charged particle beam apparatus, the relaxation process is performed on the optical element in accordance with the detected change in current, so there is no need to set an optical element or a combination of optical elements that perform the relaxation process for each mode. In the charged particle beam apparatus including the optical element, the influence of the hysteresis of the optical element can be easily reduced. Furthermore, in such a charged particle beam apparatus, the relaxation process can be appropriately executed not only when the mode is switched but also in various situations where the relaxation process is required.

The charged particle beam device control method according to the present invention includes:
A method for controlling a charged particle beam apparatus including an optical system including a plurality of optical elements that generate a magnetic field by being supplied with an electric current,
A change in current supplied to each of the plurality of optical elements is detected, and relaxation processing is performed on the optical element in accordance with the detected change in current.

  In such a charged particle beam device control method, since the optical element is subjected to relaxation processing in accordance with the detected current change, it is necessary to set an optical element or a combination of optical elements for which relaxation processing is performed for each mode. In the charged particle beam apparatus including a plurality of optical elements, the influence of the hysteresis of the optical elements can be easily reduced. Furthermore, in such a control method of the charged particle beam apparatus, the relaxation process can be appropriately executed not only when the mode is switched but also in various situations where the relaxation process is required.

The figure which shows the structure of the electron microscope which concerns on this embodiment. The figure which shows the structure of the optical system of an electron microscope main body. A graph for explaining relaxation processing. A graph for explaining relaxation processing. The flowchart which shows an example of the flow of a process of the control apparatus of the electron microscope which concerns on this embodiment. The graph which shows the change of the electric current supplied to an objective lens. The graph which shows the change of the electric current supplied to an objective lens. The graph which shows the change of the electric current supplied to an objective lens. The graph which shows the change of the electric current supplied to an objective lens.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

  Hereinafter, an electron microscope will be described as an example of the charged particle beam apparatus according to the present invention, but the charged particle beam apparatus according to the present invention is not limited to the electron microscope.

1. First, an electron microscope according to the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of an electron microscope 100 according to the present embodiment.

  As shown in FIG. 1, the electron microscope 100 includes an electron microscope main body 2, a driving device 4, and a control device 6 (an example of a control unit). The electron microscope 100 is a transmission electron microscope (TEM). The electron microscope 100 also functions as a scanning transmission electron microscope (STEM).

  The electron microscope main body 2 includes an optical system including an electron source (electron gun), an irradiation system for irradiating the sample with an electron beam, and an imaging system for forming an image with electrons transmitted through the sample. The optical system includes a plurality of optical elements (such as an electromagnetic lens and an electromagnetic deflector) that generate a magnetic field when supplied with an electric current. The electron microscope main body 2 further includes a sample stage for holding a sample, a detector for detecting electrons transmitted through the sample, and acquiring a TEM image or an STEM image.

  The drive device 4 operates each part of the electron microscope main body 2. For example, the driving device 4 supplies a driving current (such as a lens current) to each part of the electron microscope main body 2 in accordance with a control signal from the control device 6. Further, the driving device 4 receives a signal output from a detector mounted on the electron microscope main body 2 and stores a TEM image or a STEM image as image data. The drive device 4 is connected to the control device 6 via a LAN or a network.

  The control device 6 (computer) controls the electron microscope main body 2. Specifically, for example, the control device 6 generates a control signal for operating the electron microscope main body 2 and sends the control signal to the driving device 4. Thereby, each part of the electron microscope main body 2 can be operated. Moreover, the control apparatus 6 can receive a user's operation and can perform control according to the user's operation.

  Although not shown, the control device 6 includes a processor such as a CPU (Central Processing Unit), and a storage device such as a ROM (Read Only Memory), a RAM (Random access Memory), and a hard disk. The storage device stores various programs, data, and the like for controlling the electron microscope main body 2.

  FIG. 2 is a diagram showing the configuration of the optical system of the electron microscope main body 2. As shown in FIG. 2, the optical system of the electron microscope main body 2 includes an electron gun 20, a first converging lens 22 including three stages of lenses, a transfer lens 24, deflection coils 25 a and 25 b, and a second converging lens. 26, an objective lens 27, an intermediate lens 28, and a projection lens 29. Although not shown, the optical system of the electron microscope main body 2 may include a scanning coil.

  In addition, an aberration correction device 40 is incorporated in the optical system of the electron microscope main body 2. The aberration correction apparatus 40 includes a first multipole element 41, a first transfer lens 42, deflection coils 44a, 44b, and 44c, a second transfer lens 46, and a second multipole element 48. . In the aberration correction apparatus 40, the spherical aberration of the irradiation system is corrected by a two-stage multipole field generated by the first multipole element 41 and the second multipole element 48.

  The first converging lens 22, the transfer lens 24, the second converging lens 26, the objective lens 27, the intermediate lens 28, the projection lens 29, the first transfer lens 42, and the second transfer lens 46 are, for example, electromagnetic lenses. The electromagnetic lens converges or diverges an electron beam by a magnetic field. The electromagnetic lens bends an electron beam by a magnetic field generated by passing a current through a coil (solenoid), for example. In the electromagnetic lens, when the current flowing through the coil is changed, the strength of the generated magnetic field changes, and the focal length, magnification, and the like change. A magnetic material is used for the electromagnetic lens.

  The deflection coils 25a and 25b, the scanning coil, and the deflection coils 44a, 44b, and 44c are, for example, electromagnetic deflectors. The electromagnetic deflector deflects an electron beam by a magnetic field. The electromagnetic deflector bends an electron beam by a magnetic field generated by passing a current through a coil (solenoid), for example. In the electromagnetic deflector, when the current flowing through the coil is changed, the strength of the generated magnetic field changes, and the amount of deflection of the electron beam changes. A magnetic material is used for the electromagnetic deflector.

  When the electron microscope 100 functions as a scanning transmission electron microscope (in the STEM mode), the electron beam emitted from the electron gun 20 is converged by the first converging lens 22 and enters the aberration correction device 40. In the aberration correction device 40, aberration (spherical aberration) is corrected. The electron beam that has passed through the aberration correction device 40 is transferred by the transfer lens 24, converged by the second focusing lens 26 and the objective lens 27, and irradiated on the sample S. The electron microscope 100 includes a scanning coil (not shown), and scans an electron beam on the sample S with the scanning coil. The electron beam transmitted through the sample S passes through the intermediate lens 28 and the projection lens 29, and is detected by a detector (not shown). Thereby, a STEM image can be acquired.

When the electron microscope 100 functions as a transmission electron microscope (in the TEM mode), the electron beam emitted from the electron gun 20 is converged by the first converging lens 22 and the second converging lens 26 and irradiated onto the sample S. . The electron beam that has passed through the sample S passes through the objective lens 27 and the intermediate lens 28.
, And through the projection lens 29, a TEM image is formed on the detector. Thereby, a TEM image can be acquired.

2. Next, the operation of the electron microscope 100 will be described. First, relaxation processing in optical elements such as an electromagnetic lens and an electromagnetic deflector will be described. The relaxation processing is processing for reducing the influence of hysteresis (magnetic hysteresis) in an optical element such as an electromagnetic lens and an electromagnetic deflector.

  3 and 4 are graphs for explaining the relaxation processing. In the graphs shown in FIGS. 3 and 4, the horizontal axis is time, and the vertical axis is current (lens current).

  As the relaxation process, as shown in FIG. 3, a process for obtaining a target current value is performed after the current flowing through the electromagnetic lens is periodically oscillated. In the example shown in FIG. 3, the amplitude of the current is gradually reduced around the target current value. More specifically, in the example shown in FIG. 3, the current is swung at a constant frequency with the target current value as the center, and the amplitude is gradually decreased with the passage of time so that the amplitude finally becomes zero. . By this processing, the influence of hysteresis in the electromagnetic lens can be reduced.

  Further, as the relaxation processing, as shown in FIG. 4, after the supply of the current flowing through the electromagnetic lens is stopped for a predetermined time (after the current is set to “0”), the processing for setting the target current value again may be performed. Good. By this processing, the influence of hysteresis in the electromagnetic lens can be reduced.

  Here, the relaxation processing of the electromagnetic lens has been described, but the same applies to the relaxation processing of other optical elements such as an electromagnetic deflector.

  Next, the operation of the electron microscope 100 will be described. In the electron microscope 100, a change in current supplied to each of a plurality of optical elements (electromagnetic lens or electromagnetic deflector) is detected, and relaxation processing is performed on the optical element in accordance with the detected change in current.

  Below, the relaxation process with respect to the objective lens 27 is demonstrated. FIG. 5 is a flowchart illustrating an example of a process flow of the control device 6. 6 to 9 are graphs showing changes (time changes) in the current (lens current) supplied to the objective lens 27. In the graphs shown in FIGS. 6 to 9, the horizontal axis is time (elapsed time), and the vertical axis is lens current.

  The control device 6 starts processing for acquiring information on the current (lens current) supplied to the objective lens 27 at given time intervals (S100).

  The driving device 4 outputs a command voltage (control signal) for the objective lens 27. The command voltage is a voltage for designating the lens current of the objective lens 27. In the illustrated example, the control device 6 acquires this command voltage every 0.5 seconds. Thereby, information on the lens current of the objective lens 27 can be acquired.

  The control device 6 may receive information on the lens current of the objective lens 27 by receiving an output signal of a detector (not shown) that detects the lens current of the objective lens 27. That is, the control device 6 may acquire information on the lens current of the objective lens 27 from the command voltage (control signal) output from the drive device 4, and the actual measurement result of the lens current of the objective lens 27 may be obtained. The lens current information may be acquired by acquiring the lens current.

The control device 6 determines the lens current specified by the lens current information (command voltage) of the objective lens 27 (lens current acquired for the nth time) and the lens current of the objective lens 27 acquired immediately before the lens current. It is determined whether or not the difference D between the lens current specified from the information (command voltage) (the lens current acquired at the (n-1) th time) exceeds the threshold T (S102). The threshold T is appropriately set according to the hysteresis characteristic of the objective lens 27. A change in the lens current of the objective lens 27 can be detected by the process of step S102. The control device 6 repeats this process until the acquired lens current exceeds the threshold T (No in S102).

  As illustrated in FIG. 7, when the control device 6 determines that the difference D exceeds the threshold value T (Yes in S102), the lens current specified from the acquired lens current information of the objective lens 27 (obtained at the nth time). The difference D between the lens current (the lens current acquired at the (n + 1) th time) and the lens current specified from the lens current information of the objective lens 27 acquired next is equal to or less than a predetermined value A (for example, the difference is 0). It is determined whether or not there is (S104). The control device 6 repeats this process until the difference D between the current acquired at the nth time and the current acquired at the (n + 1) th time is equal to or smaller than a predetermined value A (for example, the difference is 0) (No in S104). FIG. 8 illustrates a case where the difference D between the current acquired at the nth time and the current acquired at the (n + 1) th time is greater than a predetermined value A.

  When the control device 6 determines that the difference D between the lens current acquired at the nth time and the lens current acquired at the (n + 1) th time is equal to or less than the predetermined value A (Yes in S104, see FIG. 9), the objective lens 27 A relaxation process is performed on the (S106). The relaxation process is performed by, for example, either the method shown in FIG. 3 or the method shown in FIG.

  After performing the relaxation process (after S106), the control device 6 returns to Step S102. The control device 6 repeatedly performs the process of step S102, the process of step S104, and the process of step S106.

  In the above description, the control device 6 has described the processing for the objective lens 27. However, the control device 6 performs, for example, all of the plurality of electromagnetic lenses and the plurality of electromagnetic deflectors constituting the optical system of the electron microscope main body 2. Perform the process.

  The electron microscope 100 has the following features, for example.

  In the electron microscope 100, the control device 6 detects a change in current supplied to each of the plurality of optical elements, and performs relaxation processing on the optical element in accordance with the detected change in current. Therefore, in the electron microscope 100, it is not necessary to set an optical element or a combination of optical elements for performing relaxation processing for each mode. In the electron microscope 100 including a plurality of optical elements, the influence of the hysteresis of the optical element can be easily obtained. Can be reduced. Furthermore, the electron microscope 100 can appropriately execute the relaxation process not only when the mode is switched but also in various situations where the relaxation process is required.

  For example, in a general electron microscope, there may be a large number (for example, 50 or more) of modes that require relaxation processing at the time of switching. It takes time and effort to register optical elements that perform relaxation processing and combinations thereof for each mode. Furthermore, each time a mode is added, an optical element that performs relaxation processing and a combination thereof must be registered.

  On the other hand, in the electron microscope 100, such a trouble can be saved and the influence of the hysteresis of the optical element can be easily reduced.

In observation with an electron microscope, the objective lens 27 is often used to focus the sample. In a general electron microscope, when the focus is greatly shifted, the lens current of the objective lens 27 is changed to adjust the focus. After that, again the objective lens 2
When 7 is returned to neutral excitation with a neutral button or the like (that is, when the lens current is returned to the initial state), alignment is often shifted in the spherical aberration correction device due to the influence of hysteresis. In the electron microscope 100, even in the same mode (that is, even when the mode is not switched), such a problem does not occur because the relaxation processing is performed according to the change in the lens current.

  In the electron microscope 100, the control device 6 starts a process (S100) for acquiring information on the current supplied to the optical element at a given time interval for each of the plurality of optical elements, and the nth time. In the process of determining whether or not the difference between the current acquired in step n and the current acquired in the (n−1) th time exceeds the threshold T (S102), and when it is determined that the threshold T has been exceeded (Yes in S102), Processing for determining whether or not the difference between the current acquired at the nth time and the current acquired at the (n + 1) th time is equal to or smaller than a predetermined value A (S104), and a case where it is determined that the current is equal to or smaller than the predetermined value A (Yes in S104) In addition, a relaxation process is performed on the optical element. Therefore, the electron microscope 100 can appropriately execute the relaxation process not only when the mode is switched but also in various situations where the relaxation process is necessary.

  For example, when the mode is switched and the lens current of the objective lens 27 is greatly changed, the change in current becomes 0 (predetermined value A or less) immediately after the mode is switched. Therefore, the relaxation processing is performed on the objective lens 27 immediately after the mode is switched by the processing in step S102 and the processing in step S104.

  Further, for example, when the user performs an operation of changing the focus greatly in order to adjust the focus while confirming the TEM image, the lens current of the objective lens 27 is the time interval (the time interval at which the control device 6 acquires current information ( It changes for a time longer than a given time interval of step S100 (for example, 0.5 seconds). In this case, if it is determined whether or not the mitigation process is performed only by the process of step S102, the mitigation process is performed while the user is focusing. By performing the process of step S104 in addition to the process of step S102, even when the lens current of the objective lens 27 changes over a time longer than the time interval at which the control device 6 acquires the current information, at an appropriate timing. The mitigation process can be performed (at the timing when the change in current becomes 0 (below a predetermined value)).

  In the electron microscope 100, the relaxation process (S106) is performed by stopping the supply of current to the optical element for a predetermined time. In the electron microscope 100, the relaxation process (S106) is performed by periodically vibrating the current supplied to the optical element. Thereby, the influence of the hysteresis in an optical element can be reduced.

  An electron microscope control method according to the present embodiment is an electron microscope control method including an optical system including a plurality of optical elements, and detects and detects a change in current supplied to each of the plurality of optical elements. A relaxation process is performed on the optical element in accordance with a change in current. Specifically, in the control method of the electron microscope according to the present embodiment, the process of starting the process of acquiring information on the current supplied to the optical element at a given time interval for each of the plurality of optical elements. And the step of determining whether or not the difference between the current acquired at the nth time and the current acquired at the (n-1) th time exceeds the threshold value T, and if it is determined that the threshold value T has been exceeded, acquired at the nth time A step of determining whether or not a difference between the obtained current and the current acquired at the n + 1th time is equal to or less than a predetermined value, and a step of performing relaxation processing on the optical element when it is determined to be equal to or less than the predetermined value; including. Therefore, there is no need to set an optical element or a combination of optical elements for performing relaxation processing for each mode, and in the electron microscope 100 including a plurality of optical elements, the influence of hysteresis of the optical elements can be easily reduced. .

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation implementation is possible within the range of the summary of this invention.

  For example, in the above-described embodiment, an example in which the charged particle beam apparatus according to the present invention is an electron microscope has been described. However, the charged particle beam apparatus according to the present invention uses a charged particle beam (such as an electron beam or an ion beam). Any apparatus that can observe, analyze, and process a sample may be used. The charged particle beam apparatus according to the present invention may be, for example, a scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), a focused ion beam apparatus (FIB apparatus), or the like.

  In addition, embodiment mentioned above and a modification are examples, Comprising: It is not necessarily limited to these. For example, each embodiment and each modification can be combined as appropriate.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 2 ... Electron microscope main body, 4 ... Drive apparatus, 6 ... Control apparatus, 20 ... Electron gun, 22 ... 1st convergence lens, 24 ... Transfer lens, 25a ... Deflection coil, 25b ... Deflection coil, 26 ... 2nd convergence lens, 27 ... objective lens, 28 ... intermediate lens, 29 ... projection lens, 40 ... aberration correction device, 41 ... first multipole, 42 ... first transfer lens, 44a ... deflection coil, 44b ... deflection coil, 44c ... deflection coil, 46 ... second transfer lens, 48 ... second multipole, 100 ... electron microscope

Claims (7)

An optical system including a plurality of optical elements that generate a magnetic field when supplied with an electric current;
A control unit that detects a change in current supplied to each of the plurality of optical elements, and performs relaxation processing on the optical element in accordance with the detected change in current;
A charged particle beam apparatus. In claim 1,
The control unit, for each of the plurality of optical elements,
A process of starting a process of acquiring information on the current supplied to the optical element at a given time interval;
a process of determining whether or not a difference between the current acquired at the nth time and the current acquired at the (n-1) th time exceeds a threshold;
A process of determining whether or not a difference between the current acquired at the nth time and the current acquired at the (n + 1) th time is equal to or less than a predetermined value when it is determined that the threshold value has been exceeded;
A process of performing relaxation processing on the optical element when it is determined that the predetermined value or less;
A charged particle beam device. In claim 1 or 2,
In the relaxation process, a charged particle beam apparatus that stops supplying current to the optical element for a predetermined time. In claim 1 or 2,
In the relaxation process, a charged particle beam apparatus that periodically vibrates a current supplied to the optical element. In any one of Claims 1 thru | or 4,
The charged particle beam device, wherein the optical element is an electromagnetic lens that converges or diverges an electron beam by a magnetic field, or an electromagnetic deflector that deflects the electron beam by a magnetic field. A method for controlling a charged particle beam apparatus including an optical system including a plurality of optical elements that generate a magnetic field by being supplied with an electric current,
A method for controlling a charged particle beam apparatus, comprising: detecting a change in current supplied to each of the plurality of optical elements; and performing relaxation processing on the optical element in accordance with the detected change in current. In claim 6,
For each of the plurality of optical elements,
Starting the process of obtaining information on the current supplied to the optical element at given time intervals;
determining whether the difference between the current acquired at the nth time and the current acquired at the (n-1) th time exceeds a threshold;
A step of determining whether or not a difference between the current acquired at the nth time and the current acquired at the (n + 1) th time is equal to or less than a predetermined value when it is determined that the threshold value has been exceeded;
A step of performing relaxation processing on the optical element when it is determined that the predetermined value or less;
A method for controlling a charged particle beam apparatus, comprising:

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