JP2023117159A - Measuring method and electron microscope - Google Patents

Abstract

The present invention provides a measurement method that allows changing the irradiation angle of an electron beam without tilting a sample or deflecting the electron beam. A measuring method according to the present invention includes an electron source that emits an electron beam, an irradiation system diaphragm that restricts passage of the electron beam, and an irradiation system that focuses the electron beam and irradiates the sample. A measurement method in an electron microscope comprising: arranging the position of the irradiation system aperture at the first position to make the irradiation angle of the electron beam incident on the sample the first irradiation angle; by arranging the electron beam at a second position different from the first position, thereby setting the irradiation angle of the electron beam incident on the sample to a second irradiation angle different from the first irradiation angle. [Selection diagram] Figure 4

Description

The present invention relates to measuring methods and electron microscopes.

Alchemi (atom location by channeling enhanced microanalysis) is known, which uses the phenomenon (electron channeling) in which incident electrons pass through specific atomic positions in a transmission electron microscope to identify the positions of impurity atoms in crystals. ing.

For example, in Patent Literature 1, alchemy is performed to determine which parts of the main phase, which is the crystal structure that determines the properties of the material, are replaced by added trace elements. In Patent Document 1, characteristic X-rays are detected by changing the incident angle of an electron beam with respect to a sample, and from the difference in the intensity of the characteristic X-rays due to the change in the incident angle, the site of the main phase substituted by trace elements is specified. are doing.

Patent Literature 1 describes a method of tilting the sample by a sample stage having a tilting mechanism and a method of tilting the electron beam by a deflector as methods for changing the incident angle of the electron beam with respect to the sample.

JP 2019-124492 A

When the sample is tilted by the sample stage in order to change the incident angle of the electron beam on the sample, the sample may be displaced because the sample stage operates mechanically. Therefore, the analysis position shifts every time the incident angle of the electron beam is changed.

Further, when the electron beam is tilted by a deflector in order to change the angle of incidence of the electron beam on the sample, the electron beam may deviate from the optical axis. Therefore, the optical system such as the aberration corrector must be adjusted each time the incident angle of the electron beam is changed.

One aspect of the measuring method according to the present invention is
an electron source that emits an electron beam;
an irradiation system for converging the electron beam and irradiating it onto a sample, the irradiation system including an irradiation system aperture for restricting passage of the electron beam;
A measuring method in an electron microscope comprising
a step of setting the irradiation angle of the electron beam incident on the sample to a first irradiation angle by arranging the position of the irradiation system aperture at a first position;
setting the irradiation angle of the electron beam incident on the sample to a second irradiation angle different from the first irradiation angle by arranging the position of the irradiation system aperture at a second position different from the first position; ,
including.

In such a measurement method, since the irradiation angle of the electron beam is changed by changing the position of the irradiation system diaphragm, there is no need to tilt the sample or deflect the electron beam in order to change the irradiation angle. .

One aspect of the electron microscope according to the present invention is
an electron source that emits an electron beam;
an irradiation system for converging the electron beam and irradiating it onto a sample, the irradiation system including an irradiation system aperture for restricting passage of the electron beam;
a control unit that controls the irradiation system aperture;
including
The control unit
a process of setting the irradiation angle of the electron beam incident on the sample to a first irradiation angle by arranging the position of the irradiation system aperture at a first position;
A process of setting the irradiation angle of the electron beam incident on the sample to a second irradiation angle different from the first irradiation angle by arranging the position of the irradiation system aperture at a second position different from the first position. ,
I do.

In such an electron microscope, since the irradiation angle of the electron beam can be changed by changing the position of the irradiation system aperture, there is no need to tilt the sample or deflect the electron beam in order to change the irradiation angle. .

The figure which shows the structure of the electron microscope which concerns on one Embodiment of this invention. A ray diagram of a state in which an electron beam is converged and irradiated onto a sample. Ronchigram corresponding to the ray diagram shown in FIG. A ray diagram when the position of the irradiation system diaphragm is changed in a state where the electron beam is converged and irradiated onto the sample. Ronchigram corresponding to the ray diagram shown in FIG. A ray diagram when the position of the irradiation system diaphragm is changed in a state where the electron beam is converged and irradiated onto the sample. Ronchigram corresponding to the ray diagram shown in FIG. A ray diagram when the position of the irradiation system diaphragm is changed in a state where the electron beam is converged and irradiated onto the sample. Ronchigram corresponding to the ray diagram shown in FIG. 4 is a flowchart showing an example of processing by a control unit; EDS spectrum of InP. EDS spectrum of InP.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the scope of the invention described in the claims. Moreover, not all the configurations described below are essential constituent elements of the present invention.

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

The electron microscope 100 includes an electron source 10, an irradiation system lens 20, an irradiation system diaphragm 22, an aberration corrector 30, a sample stage 40, an objective lens 50, an intermediate lens 60, a projection lens 70, and an imaging device. 80 , an X-ray detector 90 and a control unit 110 .

The electron source 10 emits electron beams. The electron source 10 is, for example, an electron gun that accelerates electrons emitted from a cathode at an anode and emits an electron beam.

The irradiation system lens (condenser lens) 20 converges the electron beam emitted from the electron source 10 and irradiates the sample S with the electron beam. For example, a plurality of illumination system lenses 20 are arranged.

The irradiation system diaphragm 22 restricts passage of electron beams emitted from the electron source 10 . The illumination system aperture 22 is, for example, a condenser aperture arranged within the illumination system lens (condenser lens) 20 . The irradiation system diaphragm 22 has a plurality of diaphragm holes with different diameters. Further, the irradiation system diaphragm 22 can move the position of the diaphragm hole. That is, the irradiation system diaphragm 22 is a movable diaphragm that allows selection of the diameter of the diaphragm hole and adjustment of the position of the diaphragm hole.

The electron microscope 100 includes a driving section for moving the irradiation system diaphragm 22, and the irradiation system diaphragm 22 (aperture hole) can be moved by the control section 110 operating the driving section. The driving unit includes, for example, a driving device such as a motor for moving the irradiation system diaphragm 22 .

Although not shown, the electron microscope 100 has a deflector that two-dimensionally deflects the electron beam. By two-dimensionally deflecting the electron beam converged by the deflector, the sample S can be scanned with the electron beam. By scanning the sample S with an electron beam and detecting the electrons transmitted through the sample S, a scanning transmission electron microscope image (STEM image) can be obtained.

The aberration corrector 30 corrects aberration of the irradiation system 2 . The aberration corrector 30 is, for example, a spherical aberration corrector that corrects spherical aberration of the irradiation system 2 . The aberration corrector 30 corrects the spherical aberration of the illumination system 2 by creating negative spherical aberration to cancel the positive spherical aberration of the illumination system 2 .

The irradiation system 2 for irradiating the sample S with the electron beam in the electron microscope 100 includes an irradiation system lens 20 , an irradiation system diaphragm 22 , an aberration corrector 30 , and a front magnetic field of the objective lens 50 .

The sample stage 40 holds the sample S. The sample stage 40 holds a sample S fixed to a sample holder 42, for example. In the illustrated example, the sample stage 40 is a side entry stage into which the sample S is inserted from the side of the pole piece of the objective lens 50 .

The objective lens 50 is a first-stage lens for forming an image with the electron beam that has passed through the sample S. FIG. The objective lens 50 has a pole piece (not shown) and generates a magnetic field between the upper pole and the lower pole of the pole piece to converge the electron beam. A sample S is placed between the upper and lower pole pieces of the pole piece. When acquiring an STEM image, the electron beam is converged by the front magnetic field of the objective lens 50 to form a minute probe on the sample S. FIG.

Intermediate lens 60 magnifies and transfers the electron diffraction pattern formed at the back focal plane of objective lens 50 . Projection lens 70 projects the electron diffraction pattern magnified and transferred by intermediate lens 60 onto imaging device 80 .

The imaging device 80 is arranged in the back focal plane of the objective lens 50 or in a plane conjugate to the back focal plane of the objective lens 50 . The imaging device 80 can shoot a Ronchigram. The imaging device 80 is, for example, a digital camera capable of recording a Ronchigram as a two-dimensional digital image. A Ronchigram is a projected image (figure) of a sample formed on a diffraction plane (back focal plane) by converging an electron beam near the sample.

Although not shown, the electron microscope 100 includes, as detectors for detecting electrons transmitted through the sample S, an annular detector for obtaining a high-angle scattering dark-field image (HAADF-STEM image) and a bright-field STEM image. It is equipped with a bright-field detector and the like to acquire the .

The X-ray detector 90 detects characteristic X-rays emitted from the sample S when the sample S is irradiated with the electron beam. The X-ray detector 90 is placed near the sample S when detecting X-rays. The X-ray detector 90 is, for example, an energy dispersive X-ray detector, and can perform EDS analysis (energy dispersive Xray spectroscopy). As the X-ray detector 90, for example, a silicon drift detector (SDD), a Si (Li) detector, or the like can be used.

Control unit 110 includes, for example, a processor such as a CPU (Central Processing Unit), and storage devices such as RAM (Random Access Memory) and ROM (Read Only Memory). The storage device stores programs and data for performing various controls. The functions of the control unit 110 can be realized by executing a program with a processor.

The controller 110 controls each part of the electron microscope 100 . The control unit 110 adjusts the irradiation angle of the electron beam with which the sample S is irradiated, for example, by controlling the position of the irradiation system diaphragm 22 . The control unit 110 can perform alchemy by repeating changing the irradiation angle of the electron beam and acquiring the EDS spectrum. The details of the processing for carrying out the alchemy will be described later.

2. Operation In the electron microscope 100 , the irradiation angle of the electron beam incident on the sample S can be adjusted by converging the electron beam using the irradiation system 2 and controlling the position of the irradiation system aperture 22 .

FIG. 2 is a ray diagram of a state in which the electron beam EB is converged and irradiated onto the sample S. As shown in FIG. FIG. 3 is a Ronchigram corresponding to the ray diagram shown in FIG.

As shown in FIG. 2, the irradiation system 2 is used to converge the electron beam EB into a conical shape and irradiate the sample S at one point. Accordingly, as shown in FIG. 3, a circle corresponding to the angular range of the electron beam EB converged on the sample S can be confirmed in the Ronchigram. At this time, by increasing the convergence angle 2θ of the electron beam EB with which the sample S is irradiated, the circle becomes larger, and the irradiation angle range of the electron beam EB that can be selected by the irradiation system aperture 22 can be widened.

4, 6, and 8 are ray diagrams when the position of the irradiation system diaphragm 22 is changed while the electron beam EB is converged and irradiated onto the sample S. FIG. FIG. 5 is a Ronchigram corresponding to the ray diagram shown in FIG. FIG. 7 is a Ronchigram corresponding to the ray diagram shown in FIG. FIG. 9 is a Ronchigram corresponding to the ray diagram shown in FIG.

As shown in FIGS. 4 to 9, the irradiation angle of the electron beam EB with respect to the sample S can be changed by changing the position of the irradiation system aperture 22. FIG. The irradiation angle of the electron beam EB is represented by the incident angle of the electron beam EB and the incident direction of the electron beam EB. The incident angle of the electron beam EB is the angle formed by the normal to the surface of the sample S and the electron beam EB incident on the sample S. The incident azimuth of the electron beam EB is the direction in the sample S surface of the incident electron beam EB at the incident position of the electron beam EB on the sample S surface.

The position of the irradiation system diaphragm 22 corresponds to the irradiation angle of the electron beam EB. Therefore, by changing the position of the irradiation system diaphragm 22, the irradiation angle of the electron beam EB can be changed.

The diameter of the irradiation system diaphragm 22 corresponds to the irradiation angle range of the electron beam EB. So, for example,
By reducing the diameter of the aperture of the irradiation system aperture 22, the irradiation angle range of the electron beam EB with which the sample S is irradiated can be narrowed. That is, by reducing the diameter of the aperture of the irradiation system aperture 22, the convergence angle (apex angle) of the conically converging electron beam EB can be reduced.

3. Alchemy With the electron microscope 100, alchemy can be performed using the method of adjusting the irradiation angle of the electron beam EB described above. In the electron microscope 100, the control unit 110 performs processing for performing alchemy. FIG. 10 is a flowchart showing an example of processing of the control unit 110. As shown in FIG.

First, the user sets the sample S on the sample holder 42 and mounts it on the sample stage 40 . A sample S fixed to the sample holder 42 is placed in a sample chamber within the lens barrel. The sample S placed in the sample chamber is irradiated with the electron beam EB, and observation of the sample S is started. Then, the sample S is tilted to the desired tilt amount for alchemy, and the analysis position on the sample S is irradiated with the electron beam EB.

As shown in FIG. 2, the controller 110 controls the irradiation system 2 to converge the electron beam EB conically with a large convergence angle and irradiate the analysis position of the sample S (S10).

Next, the controller 110 adjusts the aberration corrector 30 to correct the aberration of the irradiation system 2 (S20).

Next, the controller 110 moves the irradiation system diaphragm 22 to the initial position (first position) (S30). As a result, the sample S is irradiated with the electron beam EB at an irradiation angle (first irradiation angle) corresponding to the position of the irradiation system diaphragm 22 (aperture hole).

Next, control unit 110 acquires an EDS spectrum (S40). In the electron microscope 100, when the sample S is irradiated with the electron beam EB, the sample S emits characteristic X-rays. A characteristic X-ray emitted from the sample S is detected by an X-ray detector 90 . The X-ray detector 90 discriminates detected X-rays by energy to obtain an EDS spectrum. The control unit 110 acquires the obtained EDS spectrum and stores the EDS spectrum in the storage device in association with the irradiation angle of the electron beam EB (the position of the irradiation system diaphragm 22).

Next, the control unit 110 determines whether or not EDS spectra have been acquired at all preset irradiation angles (S50). When the control unit 110 determines that the EDS spectrum has not been acquired at all irradiation angles (No in S60), the control unit 110 returns to the process S30, moves the irradiation system diaphragm 22 from the first position to the second position, and performs irradiation. The angle is changed from the first irradiation angle to the second irradiation angle (S30). In this way, since the irradiation angle is changed by moving the position of the irradiation system aperture 22, the positional deviation of the sample S and the axial deviation of the electron beam EB do not occur. Therefore, it is not necessary to correct the position of the sample S or adjust the aberration corrector 30 even if the irradiation angle is changed.

The control unit 110 acquires the EDS spectrum, stores the EDS spectrum in the storage device in association with the irradiation angle (S40), and determines whether the EDS spectrum has been acquired at all irradiation angles (S50).

The control unit 110 moves the irradiation system aperture 22 (S30), acquires the EDS spectrum (S40), and controls the EDS spectrum at all irradiation angles until it is determined that the EDS spectrum has been acquired at all irradiation angles set in advance. is obtained (S50).

If the control unit 110 determines that the EDS spectrum has been acquired at all irradiation angles (Yes in S52), it ends the process of performing the alchemy.

In the above description, the case where the control unit 110 performs the processing S10, the processing S20, the processing S30, the processing S40, the processing S50, and the processing S60 for performing alchemy has been described. can be done manually.

11 and 12 are EDS spectra of InP. The EDS spectrum measurement conditions shown in FIG. 11 and the EDS spectrum measurement conditions shown in FIG. 12 are the same except that the position of the irradiation system aperture 22 is different.

As shown in FIGS. 11 and 12, by moving the position of the irradiation system diaphragm 22, the intensity ratio between the L line of In and the K line of P is greatly changed. This is due to the effect of electronic channeling. That is, the change in the intensity ratio indicates that the irradiation angle of the electron beam EB with respect to the sample S is changed by moving the position of the irradiation system diaphragm 22 .

4. Effect The measurement method in the electron microscope 100 includes a step of setting the irradiation angle of the electron beam EB incident on the sample S to the first irradiation angle by arranging the irradiation system diaphragm 22 at the first position, and a step of setting the irradiation system diaphragm 22 to the first irradiation angle. setting the irradiation angle of the electron beam EB incident on the sample S to a second irradiation angle different from the first irradiation angle by arranging the electron beam EB at a second position different from the first irradiation angle.

As described above, in the measurement method in the electron microscope 100, the irradiation angle of the electron beam EB is changed by changing the position of the irradiation system aperture 22. Therefore, in order to change the irradiation angle, the sample S may be tilted or the electron beam EB may be directed. It does not have to be deflected. Therefore, in the measurement method in the electron microscope 100, the deviation of the analysis position due to the tilting of the sample S and the deviation of the electron beam EB from the optical axis due to the deflection of the electron beam EB do not occur. Therefore, in the electron microscope 100, it is not necessary to correct the deviation of the analysis position or adjust the aberration correction device 30 each time the irradiation angle of the electron beam EB is changed.

In addition, in the electron microscope 100, the irradiation angle can be changed by changing the position of the irradiation system diaphragm 22. Therefore, the irradiation angle can be finely adjusted compared to the case where the irradiation angle is adjusted by tilting the sample S.

In the measurement method in the electron microscope 100, the electron beam EB is converged using the irradiation system 2 including the aberration corrector 30. FIG. Therefore, in the electron microscope 100, the electron beam EB can be accurately focused on one point on the sample S with a large convergence angle.

In the measurement method in the electron microscope 100, the irradiation system 2 is used to converge the electron beam EB into a conical shape and irradiate the analysis position of the sample S. FIG. Further, a step of detecting X-rays with the X-ray detector 90 to acquire a first spectrum while setting the irradiation angle of the electron beam EB to the first irradiation angle; and detecting the X-rays with the X-ray detector 90 to obtain a second spectrum. In the measurement method in the electron microscope 100, as described above, it is not necessary to correct the deviation of the analysis position or adjust the aberration correction device 30 each time the irradiation angle is changed. Multiple spectra can be acquired easily.

In the electron microscope 100, the control unit 110 sets the irradiation angle of the electron beam EB incident on the sample S to the first irradiation angle by arranging the position of the irradiation system diaphragm 22 at the first position; and setting the irradiation angle of the electron beam EB incident on the sample S to a second irradiation angle different from the first irradiation angle by arranging the position of (1) to a second position different from the first position. In the electron microscope 100, since the irradiation angle of the electron beam EB can be changed by changing the position of the irradiation system aperture 22, it is not necessary to tilt the sample S or deflect the electron beam EB in order to change the irradiation angle. good too.

In the electron microscope 100, the control unit 110 uses the irradiation system 2 to converge the electron beam EB into a conical shape and irradiate the analysis position of the sample S with the conical beam. Further, the control unit 110 acquires the first spectrum obtained by the X-ray detector 90 with the irradiation angle of the electron beam EB set to the first irradiation angle, and sets the irradiation angle of the electron beam EB to the second irradiation angle. and a process of acquiring a second spectrum obtained by the X-ray detector 90 in the angled state. Therefore, in the electron microscope 100, the controller 110 acquires a plurality of spectra obtained under different irradiation angles, so that alchemy can be easily performed.

5. Modification 5.1. First Modification In the above-described embodiment, the illumination system aperture 22 is a condenser aperture.

5.2. Second Modification In the above-described embodiment, the case of applying the method of changing the irradiation angle of the electron beam EB using the irradiation system diaphragm 22 to Alchemy was described. The technique of changing angles may be applied to analyzes other than Alchemy.

For example, the technique of changing the irradiation angle of the electron beam EB using the irradiation system aperture 22 is such that the electron beam EB irradiated onto the sample S is fixed at one point on the sample S, and the incident angle of the electron beam EB is changed over a certain angular range. It may also be used for variable beam locking.

5.3. Third Modification In the above-described embodiment, the electron microscope 100 is a transmission electron microscope (scanning transmission electron microscope), but the electron microscope 100 may be a scanning electron microscope.

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

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments. "Substantially the same configuration" means, for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect. Moreover, the present invention includes configurations in which non-essential portions of the configurations described in the embodiments are replaced. In addition, the present invention includes a configuration that achieves the same effects or achieves the same purpose as the configurations described in the embodiments. In addition, the present invention includes configurations obtained by adding known techniques to the configurations described in the embodiments.

2... Irradiation system 10... Electron source 20... Irradiation system lens 22... Irradiation system diaphragm 30... Aberration corrector 40... Sample stage 42... Sample holder 50... Objective lens 60... Intermediate lens 70... Projection lens 80 Imaging device 90 X-ray detector 100 Electron microscope 110 Control unit

Claims (8)

an electron source that emits an electron beam;
an irradiation system for converging the electron beam and irradiating it onto a sample, the irradiation system including an irradiation system aperture for restricting passage of the electron beam;
A measuring method in an electron microscope comprising
a step of setting the irradiation angle of the electron beam incident on the sample to a first irradiation angle by arranging the position of the irradiation system aperture at a first position;
setting the irradiation angle of the electron beam incident on the sample to a second irradiation angle different from the first irradiation angle by arranging the position of the irradiation system aperture at a second position different from the first position; ,
How to measure, including. In claim 1,
The measurement method, wherein the irradiation system includes an aberration corrector. In claim 1 or 2,
A measuring method comprising the step of converging the electron beam into a conical shape using the irradiation system and irradiating the analysis position of the sample. In any one of claims 1 to 3,
The electron microscope includes an X-ray detector for obtaining a spectrum by detecting X-rays emitted from the sample when the sample is irradiated with the electron beam,
obtaining a first spectrum by detecting X-rays with the X-ray detector while the irradiation angle of the electron beam is set to the first irradiation angle;
obtaining a second spectrum by detecting X-rays with the X-ray detector while the irradiation angle of the electron beam is set to the second irradiation angle;
How to measure, including. an electron source that emits an electron beam;
an irradiation system for converging the electron beam and irradiating it onto a sample, the irradiation system including an irradiation system aperture for restricting passage of the electron beam;
a control unit that controls the irradiation system aperture;
including
The control unit
a process of setting the irradiation angle of the electron beam incident on the sample to a first irradiation angle by arranging the position of the irradiation system aperture at a first position;
A process of setting the irradiation angle of the electron beam incident on the sample to a second irradiation angle different from the first irradiation angle by arranging the position of the irradiation system aperture at a second position different from the first position. ,
electron microscopy. In claim 5,
An electron microscope, wherein the illumination system includes an aberration corrector. In claim 5 or 6,
The electron microscope, wherein the control unit uses the irradiation system to converge the electron beam into a conical shape and irradiate the analysis position of the sample. In any one of claims 5 to 7,
an X-ray detector for obtaining a spectrum by detecting X-rays emitted from the sample when the sample is irradiated with the electron beam;
The control unit
a process of acquiring a first spectrum obtained by the X-ray detector with the irradiation angle of the electron beam set to the first irradiation angle;
a process of acquiring a second spectrum obtained by the X-ray detector with the irradiation angle of the electron beam set to the second irradiation angle;
electron microscopy.

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