JP6660787B2 - Electron microscope and aberration correction method - Google Patents

Description

  The present invention relates to an electron microscope and an aberration correction method.

  In high-resolution STEM observation, it is necessary to frequently correct low-order aberrations such as double astigmatism, coma aberration, and focus. The double astigmatism can be corrected using a stigma coil or a deflection coil disposed between two multipole lenses of the spherical aberration corrector. Coma can be corrected using a deflection coil. Focus can be corrected by changing the excitation of the objective lens.

  When correcting aberrations in a STEM, generally, aberration information is obtained from the shape of the Ronchigram. For example, Patent Document 1 discloses that an autocorrelation of a local region of a Ronchigram figure of an amorphous sample is obtained, and an aberration of an electron beam calculated from a local angle region on an aperture surface is detected from the autocorrelation or Fourier analysis of the autocorrelation. An aberration measurement method using a Ronchigram, which calculates each aberration based on the detection result, is disclosed.

JP 2007-180013 A

  In high-resolution STEM observation, aberrations such as double astigmatism, coma, and focus change with time until the device is stabilized, which may hinder observation. In such a case, observation must be interrupted until the device is stable.

  FIG. 13 is a diagram showing a state in which coma changes with time after a current flowing through a lens in an electron microscope is largely changed.

  In an experiment in which the mode of the device is switched or an experiment in which time is limited, it is desirable for many users to be able to observe before the device is stabilized.

  The present invention has been made in view of the above problems, and one of objects of some aspects of the present invention is to provide an electron microscope and an aberration correction method capable of correcting a time-varying aberration. Is to provide.

(1) The electron microscope according to the present invention
An electron microscope including an aberration correction element for correcting aberration of an optical system,
An aberration recording unit that records a time change of the aberration,
A control unit that controls the operation of the aberration correction element such that the time-varying aberration is corrected based on the information on the time change of the aberration recorded by the aberration recording unit;
Only including,
The control unit includes:
Based on information on the time change of the aberration, a process of predicting the time change of the aberration,
A process of performing control for operating the aberration correction element based on a prediction result of the time change of the aberration,
Do.

In such an electron microscope, the control unit controls the aberration correction element to operate to correct the time-varying aberration based on the information on the time change of the aberration recorded by the aberration recording unit. Aberration can be corrected. Therefore, in such an electron microscope, even when the aberration of the optical system changes with time, the state where the aberration is corrected can be maintained. Further, in such an electron microscope, the aberration correction element can be operated so as to correct the time-varying aberration.

(2) In the electron microscope according to the present invention,
The aberration recording unit,
A first recording process of acquiring a Ronchigram and measuring the aberration, recording the measured aberration, and recording a time at which the Ronchigram was acquired;
After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
May be performed.

  (3) The electron microscope according to the present invention
  An electron microscope including an aberration correction element for correcting aberration of an optical system,
  An aberration recording unit that records a time change of the aberration,
  A control unit that controls the operation of the aberration correction element such that the time-varying aberration is corrected based on the information on the time change of the aberration recorded by the aberration recording unit;
Including
  The aberration recording unit,
  A first recording process of acquiring a Ronchigram and measuring the aberration, recording the measured aberration, and recording a time at which the Ronchigram was acquired;
  After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
I do.

(4) an electron microscope according to the present invention,
An electron microscope including an aberration correction element for correcting aberration of an optical system,
An operation state recording unit that records a time change of an operation state of the aberration correction element,
A control unit that controls the operation of the aberration correction element so that the time-varying aberration is corrected based on information on the time change of the operation state of the aberration correction element recorded by the operation state recording unit.
Including
The control unit includes:
A process of predicting a time change of the operation state of the aberration correction element based on information of a time change of the operation state of the aberration correction element;
A process of performing control for operating the aberration correction element based on a prediction result of a temporal change in an operation state of the aberration correction element;
I do.

  In such an electron microscope, the control unit operates the aberration correction element such that the time-varying aberration is corrected based on the information on the time change of the operation state of the aberration correction element recorded by the operation state recording unit. . Here, as described later, the time change of the operation state of the aberration correction element can correspond to the time change of the aberration. Therefore, according to such an electron microscope, it is possible to correct a time-varying aberration. Further, in such an electron microscope, the aberration correction element can be operated so as to correct the time-varying aberration.

  (5) In the electron microscope according to the present invention,
  The operation state recording unit may perform a process of recording an operation state of the aberration correction element and recording a time of recording an operation state of the aberration correction element in response to a recording instruction from a user.

  (6) The electron microscope according to the present invention comprises:
  An electron microscope including an aberration correction element for correcting aberration of an optical system,
  An operation state recording unit that records a time change of an operation state of the aberration correction element,
  A control unit that controls the operation of the aberration correction element so that the time-varying aberration is corrected based on information on the time change of the operation state of the aberration correction element recorded by the operation state recording unit.
Including
  The operation state recording unit records an operation state of the aberration correction element and a time of recording an operation state of the aberration correction element in response to a recording instruction from a user.

  (7) The aberration correction method according to the present invention includes:
  An aberration correction method for correcting aberration of an optical system in an electron microscope,
  An aberration recording step of recording a time change of the aberration,
  An aberration correction step of correcting the time-varying aberration based on information of the time change of the aberration recorded in the aberration recording step;
Including
  In the aberration correction step,
  Based on the information of the time change of the aberration, predict the time change of the aberration,
  The aberration correction element is operated based on the prediction result of the time change of the aberration.

  Such an aberration correction method can correct a time-varying aberration.

  (8) The aberration correction method according to the present invention includes:
  An aberration correction method for correcting aberration of an optical system in an electron microscope,
  An aberration recording step of recording a time change of the aberration,
  An aberration correction step of correcting the time-varying aberration based on information of the time change of the aberration recorded in the aberration recording step;
Including
  In the aberration recording step,
  A first recording process of acquiring a Ronchigram and measuring the aberration, recording the measured aberration, and recording a time at which the Ronchigram was acquired;
  After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
I do.

  (9) The aberration correction method according to the present invention includes:
  An aberration correction method for correcting aberration of an optical system in an electron microscope,
  An operation state recording step of recording a time change of an operation state of the aberration correction element for correcting the aberration,
  Based on the information on the time change of the operation state of the aberration correction element recorded in the operation state recording step,
An aberration correction step of correcting the aberration that changes over time by operating the aberration correction element,
Including
  In the aberration correction step,
  Based on information on the time change of the operation state of the aberration correction element, predict the time change of the operation state of the aberration correction element,
  The aberration correction element is operated based on a prediction result of a temporal change in an operation state of the aberration correction element.

  (10) The aberration correction method according to the present invention includes:
  An aberration correction method for correcting aberration of an optical system in an electron microscope,
  An operation state recording step of recording a time change of an operation state of the aberration correction element for correcting the aberration,
  An aberration correction step of correcting the time-varying aberration by operating the aberration correction element based on information on a time change of the operation state of the aberration correction element recorded in the operation state recording step;
Including
  In the operation state recording step, an operation state of the aberration correction element is recorded according to a recording instruction from a user, and a time when the operation state of the aberration correction element is recorded.

FIG. 2 is a diagram schematically showing an electron microscope according to the first embodiment. The figure which shows typically the optical system of an electron microscope main body. FIG. 1 is a diagram illustrating a configuration of an electron microscope according to a first embodiment. FIG. 4 is a diagram illustrating an example of a control GUI of the main body control device. 9 is a flowchart illustrating a flow of an aberration correction process of the main body control device. FIG. 6 is a diagram illustrating a configuration of an electron microscope according to a second embodiment. 9 is a flowchart illustrating a flow of an aberration correction process of the main body control device. FIG. 9 is a diagram illustrating a configuration of an electron microscope according to a third embodiment. FIG. 4 is a diagram illustrating an example of a control GUI of the main body control device. 9 is a graph showing a time change of coma aberration when the mode is shifted from the TEM mode to the STEM mode. 9 is a graph showing a time change of coma aberration when the mode is shifted from the TEM mode to the STEM mode. FIG. 7 is a diagram illustrating a result of correcting a time-varying coma aberration. FIG. 7 is a diagram showing a state in which coma changes with time after a current flowing through a lens in an electron microscope is largely changed.

  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, all of the configurations described below are not necessarily essential components of the invention.

1. First embodiment 1.1. Electron Microscope First, an electron microscope according to the first embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an electron microscope 100 according to the first embodiment.

  As shown in FIG. 1, the electron microscope 100 includes an electron microscope main body 2, an aberration correction device 4, a main body control device 6, an aberration correction device control device 8, and an aberration correction device power supply 9. The electron microscope 100 is a transmission electron microscope (TEM). Further, the electron microscope 100 also functions as a scanning transmission electron microscope (STEM).

  The electron microscope main body 2 includes an optical system, a sample stage for holding a sample, a detector for capturing a TEM image and a STEM image, and the like.

  The aberration correction device 4 is incorporated in an optical system (irradiation system) of the electron microscope main body 2. The aberration corrector 4 is a spherical aberration corrector for correcting spherical aberration. The aberration corrector 4 corrects the spherical aberration of the optical system by creating negative spherical aberration and canceling the positive spherical aberration of the optical system.

  The main body control device 6 controls the electron microscope main body 2. Further, the main body control device 6 receives a signal output from the detector of the electron microscope main body 2 and generates a TEM image and a STEM image. The main body control device 6 is connected to the aberration correction device control device 8 via a network such as a LAN. The main body control device 6 can operate the aberration correction device 4 via the aberration correction device control device 8.

  The main body control device 6 performs an aberration correction process for correcting a time-varying aberration of the optical system. This aberration correction processing will be described later in “1.2. Operation of electron microscope”.

  The aberration correction device control device 8 controls the aberration correction device 4. The aberration correction device control device 8 controls the aberration correction device power supply 9 so that predetermined power is supplied to the aberration correction device 4.

  FIG. 2 is a diagram schematically showing an 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 focusing lens 22 composed of three stages of lenses, a transfer lens 24, deflection coils 25a and 25b, and a second focusing lens. 26, an objective lens 27, an intermediate lens 28, and a projection lens 29. The optical system of the electron microscope body 2 incorporates an aberration correction device 4.

  The aberration corrector 4 includes a first multipole 40, a first transfer lens 42, deflection coils 44a, 44b, 44c, a second transfer lens 46, and a second multipole 48. . The aberration corrector 4 corrects the spherical aberration of the optical system with a two-stage multipole field generated by the first multipole 40 and the second multipole 48.

  When the electron microscope 100 functions as a scanning transmission electron microscope (in the case of the STEM mode), the electron beam emitted from the electron gun 20 is focused by the first focusing lens 22 and enters the aberration correction device 4. In the aberration correction device 4, the aberration (spherical aberration) is corrected. The electron beam that has passed through the aberration corrector 4 is transferred by the transfer lens 24, is focused by the second focusing lens 26 and the objective lens 27, and is irradiated on the sample S. The electron microscope 100 includes a scanning coil (not shown), and scans the sample S with the electron beam focused by the scanning coil. The electron beam transmitted through the sample S is detected by a detector (not shown) via the intermediate lens 28 and the projection lens 29. Thereby, a STEM image can be obtained.

In the STEM mode, the double astigmatism is determined by the two-stage deflection coils 44a and 44b disposed between the first multipole 40 and the second multipole 48 of the aberration corrector 4 (for correcting the double astigmatism). Correction element). Further, double astigmatism can be corrected using the single-stage deflection coil 44c. The double astigmatism can be corrected using a stigma coil (not shown), or can be corrected by regarding a multipole coil as a stigma coil. Further, the coma can be corrected by using deflection coils 25a and 25b (aberration correction elements for correcting coma) arranged between the transfer lens 24 and the second focusing lens 26. The focus can be corrected using the objective lens 27 (an aberration correction element for correcting the focus).

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

  FIG. 3 is a diagram showing a configuration of the electron microscope 100.

  The main body control device 6 includes a processing unit 610, an operation unit 620, a display unit 630, and a storage unit 640.

  The operation unit 620 performs a process of acquiring an operation signal according to an operation by the user and sending the operation signal to the processing unit 610. The function of the operation unit 620 can be realized by, for example, buttons, keys, a touch panel display, a microphone, and the like.

  The display unit 630 displays an image generated by the processing unit 610, and its function can be realized by an LCD, a CRT, or the like. The display unit 630 displays a STEM image, a TEM image, a Ronchigram used for measuring aberrations, and the like.

  The storage unit 640 stores programs, data, and the like for the processing unit 610 to perform various calculation processes and control processes. Further, the storage unit 640 is used as a work area of the processing unit 610, and is also used to temporarily store a calculation result or the like executed by the processing unit 610 according to various programs. The function of the storage unit 640 can be realized by a hard disk, a RAM, or the like.

  The processing unit 610 performs processing such as control of the electron microscope main body 2 and aberration correction processing for correcting time-varying aberration. The function of the processing unit 610 may be realized by executing a program by various processors (CPU, DSP, etc.), or may be realized by a dedicated circuit such as an ASIC (gate array, etc.). The processing section 610 includes an aberration recording section 612, an aberration correction element control section 614, and a main body control section 616.

  The aberration recording unit 612 records the time change of the aberration of the optical system.

  Here, the aberration to be corrected is at least one of double astigmatism, coma aberration, and focus. These aberrations change with time when the current flowing through the lens constituting the optical system is greatly changed. When the mode is switched from the TEM mode to the STEM mode, or when the high-voltage power supply for accelerating the electrons emitted from the electron gun 20 is switched, the current flowing through the lens is greatly changed.

  The aberration recording unit 612 acquires the Ronchigram, measures the aberration, records the measured aberration, records the time at which the Ronchigram was acquired, and records the Ronchigram again after the first recording process. A second recording process is performed to acquire and measure the aberration, record the measured aberration, and record the time at which the Ronchigram was acquired. Thereby, the time change of the aberration can be recorded.

  The aberration recording unit 612 measures the aberration by, for example, an SRAM (Segmental-Ronchigram-Autocorrelation-Function Matrix) method. Specifically, when acquiring the Ronchigram imaged by the electron microscope main body 2, the aberration recording unit 612 divides the Ronchigram into small regions, acquires an autocorrelation function (auto correlation function) for each small region, and The aberration is calculated from the shape of the autocorrelation function. The amount of double astigmatism, the amount of coma aberration, and the amount of defocus can be measured from the Ronchigram.

  The aberration recording unit 612 has a timer for measuring time (having a function as a clock), and records the time at which the Ronchigram was acquired by the timer.

  The aberration recording unit 612 performs a process of storing information on the time change of the aberration obtained in the first recording process and the second recording process in the storage unit 640.

  Here, the case where the aberration recording unit 612 performs the process of recording the aberration twice has been described, but the number of times the aberration recording unit 612 performs the process of recording the aberration is not particularly limited. For example, the aberration recording unit 612 may perform the process of recording aberration three or more times.

  The aberration correction element control unit 614 controls the operation of the aberration correction element based on the information on the time change of the aberration recorded by the aberration recording unit 612 so that the time-varying aberration is corrected. Specifically, the aberration correction element control unit 614 predicts a time change of the aberration based on the information of the time change of the aberration, and operates the aberration correction element based on a prediction result of the time change of the aberration. And performing control.

  The process of estimating the time change of the aberration is performed by estimating the time change of the aberration from the information of the time change of the aberration and the aberration variation function described below.

  Here, for example, when the lens current fluctuates when shifting from the TEM mode to the STEM mode, the time change of the aberration can be approximated by a predetermined function (a function approximating the time change of the aberration is called an aberration change function). ). Therefore, the time change of the aberration can be predicted from the information on the aberration change function and the time change of the aberration. For example, as shown in an embodiment to be described later, when the mode is shifted from the TEM mode to the STEM mode, the time change of the coma aberration can be linearly approximated within a predetermined time immediately after switching. Therefore, by recording the time change of the coma aberration, the subsequent time change of the coma aberration can be predicted. A plurality of aberration variation functions are prepared in advance according to the cause of the change in aberration, and are stored in the storage unit 640, for example.

  The aberration correction element control unit 614 generates a control signal for operating the aberration correction element so as to cancel the time-varying aberration from the prediction result of the time change of the aberration, and controls the aberration correction element.

  The main body control unit 616 controls the electron microscope main body 2. The main body control unit 616 controls the optical system of the electron microscope main body 2, the sample stage, and the like, for example, based on an operation signal from the operation unit 620.

  FIG. 4 is a diagram illustrating an example of a control GUI (Graphical User Interface) 70 of the main body control device 6.

  The control GUI 70 displays a recording start button 72a, a recording end button 72b, a recording time input unit 74, an aberration correction start button 76a, an aberration correction end button 76b, and an aberration correction time input unit 78.

  The recording start button 72a is a button for starting measurement of aberration. When the recording start button 72a is pressed, the aberration recording unit 612 performs the above-described first recording processing.

  The recording end button 72b is a button for ending the measurement of the aberration. When the recording end button 72b is pressed, the aberration recording unit 612 performs the above-described second recording process.

  The recording time input section 74 is for inputting a time when the measurement of the aberration is completed. When the recording start button 72a is pressed after the time is input to the recording time input unit 74, the aberration recording unit 612 performs the first recording process and then performs the second recording at the timing when the input time has elapsed. Perform processing.

  The aberration correction start button 76a is a button for starting aberration correction. When the aberration correction start button 76a is pressed, the aberration correction element control unit 614 starts control for operating the aberration correction element.

  The aberration correction end button 76b is a button for ending aberration correction. When the aberration correction end button 76b is pressed, the aberration correction element control unit 614 ends the control for operating the aberration correction element.

  The aberration correction time input section 78 is for inputting a time to end the aberration correction. When the aberration correction start button 76a is pressed after the time is input to the aberration correction time input unit 78, the aberration correction element control unit 614 starts control to operate the aberration correction element, and the input time elapses. At this timing, the processing for operating the aberration correction element ends.

1.2. Next, the operation of the electron microscope 100 will be described. Here, a case where the main body control device 6 performs a process of correcting aberration of the optical system of the electron microscope main body 2 will be described. FIG. 5 is a flowchart illustrating an example of the flow of the aberration correction process of the main body control device 6.

  First, the aberration recording unit 612 determines whether the user has issued a recording start instruction (step S100). The aberration recording unit 612 determines that the user has issued the recording start instruction when the recording start button 72a of the control GUI 70 is pressed.

  If it is determined that the recording start instruction has been issued (YES in step S100), the aberration recording unit 612 acquires the Ronchigram, measures twice astigmatism, coma aberration, and focus, and measures the measured values. Is recorded (step S102). Further, the aberration recording unit 612 records the time at which the Ronchigram was acquired (step S104). The information on the aberration and the information on the time at which the Ronchigram was acquired are stored in the storage unit 640. Note that the aberration recording unit 612 may display the elapsed time from the start of recording on the display unit 630.

  Next, the aberration recording unit 612 determines whether the user has issued an instruction to end recording (step S106). The aberration recording unit 612 determines that the user has issued a recording end instruction when a press operation is performed on the recording end button 72b of the control GUI 70.

  If it is determined that the recording end instruction has been issued (YES in step S106), the aberration recording unit 612 acquires the Ronchigram, measures twice astigmatism, coma aberration, and focus, and measures the measured values. Is recorded (step S108). Further, the aberration recording unit 612 records the time at which the Ronchigram was acquired (Step S110). The information on the aberration and the information on the time at which the Ronchigram was acquired are stored in the storage unit 640.

  Next, the aberration correction element control unit 614 predicts the time change of the aberration based on the information of the time change of the aberration (Step S112).

  The aberration correction element control unit 614 predicts the temporal change of the double astigmatism from the information of the temporal change of the double astigmatism and the aberration variation function of the double astigmatism. Similarly, the aberration correction element control unit 614 predicts the time change of the coma aberration from the information of the time change of the coma aberration and the aberration variation function of the coma aberration. Similarly, the aberration correction element control unit 614 predicts the time change of the focus from the information on the time change of the focus and the aberration variation function of the focus.

  After the aberration correction element control unit 614 performs a process of estimating a time change of the aberration, the processing unit 610 may perform a process of notifying a user that the aberration correction can be started. For example, the processing unit 610 may perform a process of coloring the aberration correction start button 76a of the control GUI 70, a process of turning on the color, and the like, and notify the user that the aberration correction can be started.

  Next, the aberration correction element control unit 614 determines whether or not the user has issued an instruction to start aberration correction (step S114). The aberration correction element control unit 614 determines that the user has issued an instruction to start aberration correction when the operation of pressing the aberration correction start button 76a of the control GUI 70 is performed.

  If it is determined that an instruction to start aberration correction has been issued (YES in step S114), the aberration correction element control unit 614 performs control to operate the aberration correction element based on the prediction result of the time change of aberration. (Step S116).

  Specifically, the aberration correction element control unit 614 controls the deflecting coils 44a and 44b or the deflecting coil 44c based on the prediction result of the twice astigmatic time change so that the temporally changing twice astigmatism is canceled. And outputs the control signal to the aberration correction device controller 8 to operate the deflection coils 44a and 44b or the deflection coil 44c.

  Further, the aberration correction element control unit 614 generates a control signal for controlling the deflection coils 25a and 25b so as to cancel the time-varying coma aberration based on the prediction result of the time variation of the coma aberration, and generates an electron microscope. Output to the main body 2 to operate the deflection coils 25a and 25b.

  Further, the aberration correction element control unit 614 generates a control signal for controlling the objective lens 27 so that the time change of the defocus amount does not change based on the prediction result of the time change of the focus, and sends the control signal to the electron microscope main body 2. And the objective lens 27 is operated.

  Next, the aberration correction element control unit 614 determines whether the end time of the aberration correction has been set (step S118). The aberration correction element control unit 614 determines that the end time of the aberration correction has been set when the time has been input to the aberration correction time input unit 78 of the control GUI 70.

  When it is determined that the end time of the aberration correction is set (YES in step S118), the aberration correction element control unit 614 determines whether the set time has elapsed (step S120). If it is determined that the set time has elapsed (YES in step S120), aberration correction element control section 614 ends the control for operating the aberration correction element.

On the other hand, when it is determined that the end time of the aberration correction has not been input (NO in step S118), the aberration correction element control unit 614 determines whether the user has issued an instruction to end the aberration correction ( Step S122). The aberration correction element control unit 614 determines that the user has issued an instruction to end the aberration correction when the operation of pressing the aberration correction end button 76b of the control GUI 70 is performed.

  When it is determined that the instruction to end the aberration correction is performed (YES in step S122), the aberration correction element control unit 614 ends the process of operating the aberration correction element.

  By performing the above processing, it is possible to correct time-varying aberrations (double astigmatism, coma aberration, and focus).

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

  In the electron microscope 100, the aberration recording unit 612 records the time change of the aberration of the optical system, and the aberration correction element control unit 614 corrects the aberration so that the time-varying aberration is corrected based on the information of the time change of the aberration. Control for operating the element is performed. Therefore, according to the electron microscope 100, it is possible to correct a time-varying aberration. Therefore, in the electron microscope 100, even when the aberration changes with time, the state where the aberration is corrected can be maintained. Thus, for example, when switching from the TEM mode to the STEM mode, or when switching the high-voltage power supply for accelerating the electrons emitted from the electron gun 20, there is no need to wait for a long time until the device is stabilized. Before the device is stabilized, observation with high resolution and analysis with high positional accuracy can be performed.

  In the electron microscope 100, the aberration correction element control unit 614 performs a process of predicting the time change of the aberration based on the time change of the aberration, and controls the operation of the aberration correction element based on the prediction result of the time change of the aberration. Processing. Therefore, in the electron microscope 100, the aberration correction element can be operated so that the time-varying aberration is corrected.

  In the electron microscope 100, the aberration recording unit 612 acquires the Ronchigram, measures the aberration, records the time at which the Ronchigram was acquired, and acquires the Ronchigram again after the first recording process. A second recording process for measuring the aberration and recording the time at which the Ronchigram was obtained is performed. Thereby, the time change of the aberration can be recorded.

2. Second embodiment 2.1. Next, an electron microscope according to a second embodiment will be described with reference to the drawings. FIG. 6 is a diagram illustrating a configuration of an electron microscope 200 according to the second embodiment. Hereinafter, in the electron microscope 200 according to the second embodiment, members having the same functions as those of the constituent members of the electron microscope 100 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

  In the above-described electron microscope 100, as shown in FIG. 3, the processing unit 610 includes the aberration recording unit 612, and the aberration recording unit 612 records the time change of the aberration.

  On the other hand, in the electron microscope 200, as shown in FIG. 6, the processing unit 610 includes an operation state recording unit 618, and the operation state recording unit 618 records the time change of the operation state of the aberration correction element.

The operation state recording unit 618 records the time change of the operation state of the aberration correction element. Here, the operation state of the aberration correction element is, for example, a voltage value (or a current value) applied to the deflection coils 44a and 44b when the aberration to be corrected is double astigmatism. The operation state of the aberration correction element is, for example, a voltage value (or a current value) applied to the deflection coils 25a and 25b when the aberration to be corrected is a coma aberration. The operation state of the aberration correction element is, for example, a voltage value (or a current value) applied to the objective lens 27 when the aberration to be corrected is a focus.

  The operation state recording unit 618 performs processing for recording the operation state of the aberration correction element and recording the time when the operation state of the aberration correction element was recorded, for example, when there is a recording instruction from the user. By performing this process a plurality of times, the operation state recording unit 618 can record the time change of the operation state of the aberration correction element.

  The operation state recording unit 618 includes a voltage value (or current value) applied to the deflection coils 44a and 44b, a voltage value (or current value) applied to the deflection coils 25a and 25b, and a voltage applied to the objective lens 27. By reading the value (or the current value), information on the operating state of each element is recorded. Further, the operation state recording unit 618 has a timer (having a function as a clock) for measuring time, and records the time when the operation state of the aberration correction element is recorded by the timer.

  Here, in the electron microscope 200, the user can correct the aberration by operating the operation unit 620 to adjust the voltage value (or current value) applied to the aberration correction element. That is, in the electron microscope 200, the aberration can be manually corrected. The operation state of the aberration correction element when the user manually corrects the aberration corresponds to the aberration amount of the aberration. Therefore, the time change of the operation state of the aberration correction element when the user manually corrects the time-varying aberration corresponds to the time change of the aberration.

  Therefore, the aberration correction element control unit 614 controls the operation of operating the aberration correction element such that the time-varying aberration is corrected based on the time change of the operation state of the aberration correction element recorded by the operation state recording unit 618. It can be carried out.

  In the present embodiment, the aberration correction element control unit 614 performs a process of predicting a time change of the operation state of the aberration correction element based on the information on the operation state of the aberration correction element recorded by the operation state recording unit 618, Performing a control for operating the aberration correction element based on a prediction result of a temporal change in the operation state of the correction element.

  Although the case where the operation state recording unit 618 performs the process of recording the operation state of the aberration correction element twice has been described above, the number of times that the operation state recording unit 618 performs the process of recording the operation state of the aberration correction element is described. Is not particularly limited. For example, the operation state recording unit 618 may perform the process of recording the operation state of the aberration correction element three or more times.

  In the present embodiment, the recording start button 72a of the control GUI 70 shown in FIG. 4 functions as a button for starting recording of the operation state of the aberration correction element. The recording end button 72b functions as a button for ending the recording of the operation state of the aberration correction element.

2.2. Next, the operation of the electron microscope 200 will be described. FIG. 7 is a flowchart illustrating an example of the flow of the aberration correction process of the main body control device 6.

  First, the operation state recording unit 618 determines whether or not the user has issued a recording start instruction (recording instruction) (step S200). The operation state recording unit 618 determines that the user has issued a recording start instruction when the recording start button 72a of the control GUI 70 is pressed.

  The user manually corrects twice astigmatism, coma, and focus. Then, when the user determines that these aberrations have been corrected, the user presses the recording start button 72a of the control GUI 70.

  If it is determined that the recording start instruction has been issued (YES in step S200), the operation state recording unit 618 records the operation states of the deflection coils 44a and 44b, the deflection coils 25a and 25b, and the objective lens 27. (Step S202). The operation state recording unit 618 records the time at which the operation states of these aberration correction elements were acquired (step S204). Information on the operation state of the aberration correction element and information on the time when the operation state of the aberration correction element is recorded are stored in the storage unit 640. The operation state recording unit 618 may display the elapsed time from the start of recording on the display unit 630.

  Next, the operation state recording unit 618 determines whether or not the user has issued a recording end instruction (recording instruction) (step S206). The operation state recording unit 618 determines that the user has issued an instruction to end recording when the recording end button 72b of the control GUI 70 is pressed.

  The user again manually corrects twice astigmatism, coma, and focus. When the user determines that these aberrations have been corrected, the user presses the recording end button 72b of the control GUI 70.

  If it is determined that the recording end instruction has been issued (YES in step S206), the operation state recording unit 618 records the operation states of the deflection coils 44a and 44b, the deflection coils 25a and 25b, and the objective lens 27. (Step S208). The operation state recording unit 618 records the time at which the operation states of these aberration correction elements were acquired (step S210). Information on the operation state of the aberration correction element and information on the time when the operation state of the aberration correction element is recorded are stored in the storage unit 640.

  Next, the aberration correction element control unit 614 predicts the time change of the operation state of the aberration correction element based on the information of the time change of the operation state of the aberration correction element (step S212).

  The aberration correction element control unit 614 predicts the time change of the deflection coils 44a and 44b from the information of the time change of the operation state of the deflection coils 44a and 44b and the double astigmatism variation function. Similarly, the aberration correction element control unit 614 predicts the time change of the operation state of the deflection coils 25a and 25b from the information on the time change of the operation state of the deflection coils 25a and 25b and the aberration variation function of the coma aberration. Similarly, the aberration correction element control unit 614 predicts the time change of the operation state of the objective lens 27 from the information on the time change of the operation state of the objective lens 27 and the aberration variation function of focus.

  After the aberration correction element control unit 614 performs a process of predicting a time change of the operation state of the aberration correction element, the processing unit 610 may perform a process of notifying a user that the aberration correction can be started.

  Next, the aberration correction element control unit 614 determines whether the user has issued an instruction to start aberration correction (Step S214). The aberration correction element control unit 614 determines that the user has issued an instruction to start aberration correction when the operation of pressing the aberration correction start button 76a of the control GUI 70 is performed.

If it is determined that the instruction to start the aberration correction has been issued (YES in step S214), the aberration correction element control unit 614 controls the aberration correction element based on the prediction result of the time change of the operation state of the aberration correction element. The operation is controlled (step S216).

  Specifically, the aberration correction element control unit 614 controls the deflection coils 44a and 44b based on the prediction result of the time change of the operation state of the deflection coils 44a and 44b so that the time-changed double astigmatism is canceled. And outputs the control signal to the aberration correction device controller 8 to operate the deflection coils 44a and 44b.

  Further, the aberration correction element control unit 614 controls the deflection coils 25a and 25b based on the prediction result of the time change of the operation state of the deflection coils 25a and 25b so as to cancel the time-varying coma. Is generated and output to the electron microscope main body 2 to operate the deflection coils 25a and 25b.

  In addition, the aberration correction element control unit 614 generates a control signal for controlling the objective lens 27 based on the prediction result of the time change of the operation state of the objective lens 27 so that the defocus amount does not change with time. The signal is output to the electron microscope main body 2 and the objective lens 27 is operated.

  Subsequent processing in steps S218, S220, and S222 is the same as the processing in steps S118, S120, and S222, respectively, and will not be described.

  By performing the above processing, it is possible to correct time-varying aberrations (double astigmatism, coma aberration, and focus).

  The electron microscope 200 has the following features, for example.

  In the electron microscope 200, the operation state recording unit 618 records the time change of the operation state of the aberration correction element, and the aberration correction element control unit 614 records the time change of the operation state of the aberration correction element recorded by the operation state recording unit 618. Based on the information, control is performed to operate the aberration correction element so that the time-varying aberration is corrected. Here, as described above, the time change of the operation state of the aberration correction element can correspond to the time change of the aberration. Therefore, according to the electron microscope 200, similarly to the above-described electron microscope 100, time-varying aberration can be corrected.

  In the electron microscope 200, the aberration correction element control unit 614 predicts a time change of the operation state of the aberration correction element based on information on a time change of the operation state of the aberration correction element, And performing control for operating the aberration correction element based on the prediction result of the time change. Therefore, in the electron microscope 200, by recording the time change of the operation state of the aberration correction element, the time-varying aberration can be corrected. Therefore, the electron microscope 200 can correct a time-varying aberration without acquiring a Ronchigram and measuring the aberration.

  In the electron microscope 200, the operation state recording unit 618 performs a process of recording the operation state of the aberration correction element and recording the time of recording the operation state of the aberration correction element when a recording instruction is given from the user. Therefore, in the electron microscope 200, for example, the user manually corrects the aberration and gives a recording instruction, and after a predetermined time elapses, the user again manually corrects the aberration and gives a recording instruction again, so that the aberration correction element The time change of the operation state can be made to correspond to the time change of the aberration. Accordingly, it is possible to correct the time-varying aberration from the time change of the operation state of the aberration correction element.

3. Third Embodiment Next, an electron microscope according to a third embodiment will be described with reference to the drawings. FIG. 8 is a diagram illustrating a configuration of an electron microscope 300 according to the third embodiment. Hereinafter, in the electron microscope 300 according to the third embodiment, members having the same functions as the constituent members of the electron microscope 100 according to the first embodiment and the electron microscope 200 according to the second embodiment are denoted by the same reference numerals. , And a detailed description thereof will be omitted.

  In the electron microscope 300, as shown in FIG. 8, the processing unit 610 includes an aberration recording unit 612 and an operation state recording unit 618. Therefore, in the electron microscope 300, a mode for recording the time change of the aberration and correcting the aberration (mode using the aberration recording unit 612) and a mode for recording the time change of the operation state of the aberration correction element to correct the aberration ( And a mode using the operation state recording unit 618).

  FIG. 9 is a diagram illustrating an example of the control GUI 70 of the main body control device 6 of the electron microscope 300.

  A mode selection button 79 is further displayed on the control GUI 70 of the present embodiment. The mode selection button 79 is a button for selecting a mode for recording a temporal change in aberration and a mode for recording a temporal change in the operation state of the aberration correction element. For example, when the mode selection button 79 is pressed, the electron microscope 300 operates in a mode for recording a time change of aberration. On the other hand, when the mode selection button 79 is not pressed, the electron microscope 300 operates in a mode for recording a time change of the operation state of the aberration correction element.

4. Others The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

  In the above-described embodiment, the case where the aberration to be corrected is double astigmatism, coma, and focus is described. However, the present invention provides other astigmatism other than double astigmatism, coma, and focus. It can also be applied to aberration correction for aberrations.

  Further, for example, in the above-described embodiment, an example in which the aberration correction device 4 is incorporated in the irradiation system as illustrated in FIG. 2 has been described. However, the aberration correction device 4 may be incorporated in the imaging system. .

5. EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples.

  In the present embodiment, the correction for the time change of coma aberration immediately after shifting from the TEM mode to the STEM mode was performed using a transmission electron microscope (atomic resolution electron microscope JEM-ARM300F manufactured by JEOL Ltd.).

(1) Temporal change of coma aberration First, in the JEM-ARM300F, a temporal change of coma aberration when the mode was shifted from the TEM mode to the STEM mode was recorded.

  Specifically, first, the mode was shifted from the STEM mode to the TEM mode, and the apparatus was kept on standby for 10 minutes to stabilize the optical system of the apparatus under the conditions of the TEM mode. Next, the mode was shifted from the TEM mode to the STEM mode. Then, the lens was relaxed, and the time change of the coma after that was examined.

  FIG. 10 and FIG. 11 are graphs showing a temporal change of coma aberration when the mode shifts from the TEM mode to the STEM mode. The horizontal axis of the graphs shown in FIGS. 10 and 11 is time, and the vertical axis is the CLA display value (the voltage value applied to the aberration correction element for correcting coma) in a state where coma is corrected. ). That is, the vertical axis corresponds to the amount of aberration of coma. FIG. 10 is a graph showing the component of the coma aberration in the X direction, and FIG. 11 is a graph showing the component of the coma aberration in the Y direction. The X direction and the Y direction are directions orthogonal to each other.

  From the graphs shown in FIGS. 10 and 11, it can be seen that the coma aberration changes linearly for 4 to 15 minutes after the transition from the TEM mode to the STEM mode.

(2) Correction of Time-Varying Coma Aberration In the JEM-ARM300F, the mode was shifted from the TEM mode to the STEM mode, and time-varying coma was corrected.

  Specifically, first, the mode was shifted from the STEM mode to the TEM mode, and after waiting for 10 minutes to stabilize the optical system of the apparatus under the conditions of the TEM mode, the mode was shifted from the TEM mode to the STEM mode. Next, from 6 minutes to 8 minutes after the shift to the STEM mode, the amount of change in the CLA display value of the aberration correction element with the coma corrected was recorded. Next, a change in the CLA display value corresponding to a time change of the coma aberration after 8 minutes from the recording of the change amount was predicted. After 8 minutes, the coma was corrected based on the prediction result.

  Here, the change in the CLA display value after 8 minutes was predicted from the graphs shown in FIGS. From the graphs shown in FIGS. 10 and 11, since the coma aberration changes linearly for about 15 minutes after the transition from the TEM mode to the STEM mode, it is predicted that the CLA display value also changes linearly. Therefore, the amount of change in the CLA display value per unit time is determined from the amount of change in the CLA display value from 6 minutes to 8 minutes, and the CLA value changes with the same amount of change after 8 minutes. The correction element was activated.

  FIG. 12 is a diagram showing a result of correcting time-varying coma. FIG. 12 compares a case where the coma aberration is corrected based on the prediction result (see “Correct”) and a case where the coma aberration is not corrected (see “Non Correct”). FIG. 12 shows the case where the coma aberration is corrected based on the prediction result and the case where the coma aberration is not corrected, after 2 minutes, 4 minutes, and 6 minutes, respectively. The Ronchigram is shown.

  From the results shown in FIG. 12, it can be seen that when the coma is corrected based on the prediction result, a good Ronchigram can be maintained. When the coma is not corrected, the coma becomes larger with time, and obstructs observation and analysis.

  It should be noted that the above-described embodiments and modified examples are merely examples, and the present invention is not limited to these. For example, each embodiment and each modification can be appropriately combined.

  The invention includes substantially the same configuration as the configuration described in the embodiment (for example, a configuration having the same function, method, and result, or a configuration having the same object and effect). Further, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the invention includes a configuration having the same function and effect as the configuration described in the embodiment or a configuration capable of achieving the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

2 ... Electron microscope main body, 4 ... Aberration correction device, 6 ... Main body control device, 8 ... Aberration correction device control device, 9 ... Aberration correction device power supply, 20 ... Electron gun, 22 ... First focusing lens, 24 ... Transfer lens, 25a deflection coil, 25b deflection coil, 26 second focusing lens, 27 objective lens, 28 intermediate lens, 29 projection lens, 40 first multipole, 42 first transfer lens, 44a deflection coil , 44b: deflection coil, 46: second transfer lens, 48: second multipole, 70: control GUI, 72a: recording start button, 72b: recording end button, 74: recording time input section, 76a: aberration correction start button , 76b: aberration correction end button, 78: aberration correction time input section, 79: mode selection button, 100: electron microscope, 200: electron microscope, 300: electron microscope, 610: processing section, 6 2 ... aberration recording unit, 614 ... aberration correction element control unit, 616 ... main control unit, 618 ... operating state recording unit, 620 ... operating unit, 630 ... display unit, 640 ... storage unit

Claims (10)

An electron microscope including an aberration correction element for correcting aberration of an optical system,
An aberration recording unit that records a time change of the aberration,
A control unit that controls the operation of the aberration correction element such that the time-varying aberration is corrected based on the information on the time change of the aberration recorded by the aberration recording unit;
Only including,
The control unit includes:
Based on information on the time change of the aberration, a process of predicting the time change of the aberration,
A process of performing control for operating the aberration correction element based on a prediction result of the time change of the aberration,
Do, electron microscope. Oite to claim 1,
The aberration recording unit,
A first recording process of acquiring a Ronchigram and measuring the aberration, recording the measured aberration, and recording a time at which the Ronchigram was acquired;
After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
Do, electron microscope. An electron microscope including an aberration correction element for correcting aberration of an optical system,
An aberration recording unit that records a time change of the aberration,
A control unit that controls the operation of the aberration correction element such that the time-varying aberration is corrected based on the information on the time change of the aberration recorded by the aberration recording unit;
Only including,
The aberration recording unit,
Obtaining a Ronchigram and measuring the aberration, and recording the measured aberration,
A first recording process for recording the time at which the Ronchigram was acquired;
After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
Do, electron microscope. An electron microscope including an aberration correction element for correcting aberration of an optical system,
An operation state recording unit that records a time change of an operation state of the aberration correction element,
A control unit that controls the operation of the aberration correction element so that the time-varying aberration is corrected based on information on the time change of the operation state of the aberration correction element recorded by the operation state recording unit.
Only including,
The control unit includes:
A process of predicting a time change of the operation state of the aberration correction element based on information of a time change of the operation state of the aberration correction element;
A process of performing control for operating the aberration correction element based on a prediction result of a temporal change in an operation state of the aberration correction element;
Do, electron microscope. In claim 4 ,
The electron microscope, wherein the operation state recording unit performs a process of recording an operation state of the aberration correction element and recording a time of recording an operation state of the aberration correction element in response to a recording instruction from a user. An electron microscope including an aberration correction element for correcting aberration of an optical system,
An operation state recording unit that records a time change of an operation state of the aberration correction element,
A control unit that controls the operation of the aberration correction element so that the time-varying aberration is corrected based on information on the time change of the operation state of the aberration correction element recorded by the operation state recording unit.
Only including,
The electron microscope , wherein the operation state recording unit performs a process of recording an operation state of the aberration correction element and recording a time of recording an operation state of the aberration correction element in response to a recording instruction from a user . An aberration correction method for correcting aberration of an optical system in an electron microscope,
An aberration recording step of recording a time change of the aberration,
An aberration correction step of correcting the time-varying aberration based on information of the time change of the aberration recorded in the aberration recording step;
Only including,
In the aberration correction step,
Based on the information of the time change of the aberration, predict the time change of the aberration,
An aberration correction method, wherein an aberration correction element is operated based on a prediction result of the time change of the aberration. An aberration correction method for correcting aberration of an optical system in an electron microscope,
An aberration recording step of recording a time change of the aberration,
An aberration correction step of correcting the time-varying aberration based on information of the time change of the aberration recorded in the aberration recording step;
Only including,
In the aberration recording step,
A first recording process of acquiring a Ronchigram and measuring the aberration, recording the measured aberration, and recording a time at which the Ronchigram was acquired;
After the first recording process, again, obtain a Ronchigram, measure the aberration, record the measured aberration, and record the time at which the Ronchigram was obtained, a second recording process,
The aberration correction method. An aberration correction method for correcting aberration of an optical system in an electron microscope,
An operation state recording step of recording a time change of an operation state of the aberration correction element for correcting the aberration,
An aberration correction step of correcting the time-varying aberration by operating the aberration correction element based on information on a time change of the operation state of the aberration correction element recorded in the operation state recording step;
Only including,
In the aberration correction step,
Based on information on the time change of the operation state of the aberration correction element, predict the time change of the operation state of the aberration correction element,
An aberration correction method , comprising: operating the aberration correction element based on a prediction result of a temporal change in an operation state of the aberration correction element . An aberration correction method for correcting aberration of an optical system in an electron microscope,
An operation state recording step of recording a time change of an operation state of the aberration correction element for correcting the aberration,
An aberration correction step of correcting the time-varying aberration by operating the aberration correction element based on information on a time change of the operation state of the aberration correction element recorded in the operation state recording step;
Only including,
In the operation state recording step, in accordance with a recording instruction from a user, an operation state of the aberration correction element is recorded, and a time when the operation state of the aberration correction element is recorded is recorded.