JP2020119667A - Electron microscope - Google Patents

Abstract

To provide an electron microscope capable of accurately matching an incidence angle of an electron beam to a specimen with a crystal azimuth of the specimen.SOLUTION: In an electron microscope, a control section performs processing for causing a specimen tilt mechanism to successively change a tilt angle of a specimen and acquiring multiple first electronic diffraction graphics obtained at mutually different tilt angles, processing for searching a first electronic diffraction graphic having the most diffraction spots from among the multiple first electronic diffraction graphics and calculating a first tilt angle that is a tilt angle at which the first electronic diffraction graphic having the most diffraction spots is obtained, processing for causing the specimen tilt mechanism to successively change the tilt angle of the specimen within an angle range including the first tilt angle, and acquiring multiple second electronic diffraction graphics obtained at mutually different tilt angles, processing for mutually circularly approximating the multiple second electronic diffraction graphics and calculating a second tilt angle at which a radius of the circle becomes minimum, and processing for causing the specimen tilt mechanism to change the tilt angle of the specimen into the second tilt angle.SELECTED DRAWING: Figure 7

Description

The present invention relates to an electron microscope.

In a transmission electron microscope, a sample is irradiated with an electron beam, and an electron transmitted through the sample is imaged, so that a transmission electron microscope image and an electron diffraction pattern can be acquired.

When acquiring an electron diffraction pattern with a transmission electron microscope, the incident direction of the electron beam on the sample is adjusted. When measuring the length of a fine structure in a semiconductor sample or the like, the incident direction of an electron beam is adjusted by using an electron diffraction pattern of a substrate made of silicon crystal or the like. The incident direction of the electron beam on the sample is adjusted by adjusting the tilt angle of the sample so that the incident direction of the electron beam on the sample and the crystal orientation of the sample match.

For example, Patent Document 1 discloses an electron microscope in which the tilt angle of a sample is automatically adjusted by analyzing the change in the electron diffraction pattern due to the tilt of the sample, and the incident direction of an electron beam and the crystal orientation of the sample are matched. Has been done.

In the method disclosed in Patent Document 1, electron diffraction patterns are acquired at various inclination angles, the acquired electron diffraction patterns are approximated to a circle, and the sample inclination angle at which the radius of the approximate circle is minimized is set as the optimum sample inclination angle. ..

JP, 2010-212067, A

FIG. 9 is a diagram showing an electron diffraction pattern obtained at each tilt angle when the tilt angle in the Y direction is changed, and an approximate circle of the electron diffraction pattern. FIG. 10 is a graph in which the radius of the approximate circle of each electron diffraction pattern of FIG. 9 is plotted. The horizontal axis of the graph shown in FIG. 10 is the inclination angle, and the vertical axis is the radius of the approximate circle.

As shown in FIG. 9, the electron diffraction pattern can be approximated by a circle. From the graph shown in FIG. 10, the tilt angle at which the radius of the approximate circle is minimized can be obtained, and the tilt angle at which the radius of the approximate circle is minimized is the optimum tilt angle in the Y direction.

However, if the difference between the tilt angle of the sample before automatic adjustment and the optimum tilt angle is large, that is, if the deviation between the incident angle of the electron beam on the sample and the crystal orientation of the sample is large, the electron diffraction pattern should be accurate with a circle. Cannot be approximated to.

FIG. 11 is an electron diffraction pattern obtained at each tilt angle when the tilt angle in the Y direction is changed and the electron diffraction pattern when the difference between the tilt angle of the sample before automatic adjustment and the optimum tilt angle is large. It is a graph which shows the approximate circle of a figure. FIG. 12 is a graph in which the radius of the approximate circle of each electron diffraction pattern of FIG. 11 is plotted.

As shown in FIG. 11, when the difference between the tilt angle of the sample before automatic adjustment and the optimum tilt angle is large, the electron diffraction pattern cannot be accurately approximated by a circle. Therefore, as shown in FIG. 12, the optimum tilt angle cannot be obtained from the radius of the approximate circle.

(1) One aspect of the electron microscope according to the present invention is
An irradiation system for irradiating a sample with an electron beam,
A sample tilting mechanism for tilting the sample,
An image forming system for forming an image with electrons transmitted through the sample;
An image pickup device for picking up an image formed by the image forming system;
A control unit for controlling the sample tilting mechanism,
Including
The control unit is
A process of sequentially changing the inclination angle of the sample by the sample inclination mechanism, and acquiring a plurality of first electron diffraction patterns obtained at different inclination angles,
The first electron diffraction pattern having the largest number of diffraction spots is searched for from the plurality of first electron diffraction patterns, and the first electron diffraction pattern having the largest number of diffraction spots is obtained. The process of obtaining the tilt angle,
A process of sequentially changing the tilt angle of the sample in the angle range including the first tilt angle in the sample tilt mechanism, and acquiring a plurality of second electron diffraction patterns obtained at different tilt angles;
A process of approximating each of the plurality of second electron diffraction patterns by a circle to obtain a second tilt angle at which the radius of the circle is minimized;
A process of causing the sample tilting mechanism to set a tilt angle of the sample to a second tilt angle;
I do.

In such an electron microscope, a first tilt angle at which the incident angle of the electron beam with respect to the sample and the crystal orientation of the sample are small is obtained, and the tilt angle is changed within an angle range including the first tilt angle to obtain a plurality of first tilt angles. Acquire a two-electron diffraction pattern. Therefore, the second electron diffraction pattern can be accurately approximated to a circle. Therefore, according to such an electron microscope, the incident angle of the electron beam with respect to the sample and the crystal orientation of the sample can be accurately matched.

(2) One aspect of the electron microscope according to the present invention is
An irradiation system for irradiating a sample with an electron beam,
A sample tilting mechanism for tilting the sample,
An image forming system for forming an image with electrons transmitted through the sample;
An image pickup device for picking up an image formed by the image forming system;
A control unit for controlling the sample tilting mechanism,
Including
The control unit is
A process of sequentially changing the inclination angle of the sample by the sample inclination mechanism and acquiring a plurality of first electron diffraction patterns obtained at different inclination angles;
The first tilt that is the tilt angle at which the first electron diffraction pattern that most resembles the template image is searched for from the plurality of first electron diffraction patterns and the first electron diffraction pattern that most resembles the template image is obtained. The process of finding the corner,
A process of sequentially changing the tilt angle of the sample within an angle range including the first tilt angle in the sample tilt mechanism, and acquiring a plurality of second electron diffraction patterns obtained at different tilt angles;
Circle-approximating each of the plurality of second electron diffraction patterns to obtain a second inclination angle at which the radius of the circle is minimized;
A process of causing the sample tilting mechanism to set a tilt angle of the sample to a second tilt angle;
And then
The template image is an electron diffraction pattern obtained in a state where the incident direction of the electron beam on the sample and the crystal orientation of the sample match.

In such an electron microscope, a first tilt angle at which the incident angle of the electron beam with respect to the sample and the crystal orientation of the sample are small is obtained, and the tilt angle is changed within an angle range including the first tilt angle to obtain a plurality of first tilt angles. Acquire a two-electron diffraction pattern. Therefore, the second electron diffraction pattern can be accurately approximated to a circle. Therefore, according to such an electron microscope, the incident angle of the electron beam with respect to the sample and the crystal orientation of the sample can be accurately matched.

The figure which shows the structure of the electron microscope which concerns on embodiment. FIG. 6 is a view for explaining the operation of the sample tilting mechanism. The figure which shows an electron diffraction pattern typically. The figure which shows an electron diffraction pattern typically. A table showing the number of electron diffraction spots of a plurality of electron diffraction patterns obtained at different tilt angles. The flowchart which shows an example of a process of a control part. The flowchart which shows an example of a process of the control part of the electron microscope which concerns on a 1st modification. The flowchart which shows an example of a process of the control part of the electron microscope which concerns on a 2nd modification. The figure which shows the electron diffraction pattern obtained by each inclination angle when changing the inclination angle of a Y direction, and the approximate circle of the said electron diffraction pattern. The graph which plotted the radius of the approximate circle of each electron diffraction pattern. The figure which shows the electron diffraction pattern obtained by each inclination angle when changing the inclination angle of a Y direction, and the approximate circle of the said electron diffraction pattern. The graph which plotted the radius of the approximate circle of each electron diffraction pattern.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the content of the invention described in the claims. In addition, not all of the configurations described below are essential configuration requirements of the invention.

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

The electron microscope 100 is an apparatus for observing the sample S using the electron beam EB. The electron microscope 100 is a transmission electron microscope (TEM).

As shown in FIG. 1, the electron microscope 100 includes an electron gun 10, an irradiation lens 12, a sample stage 14, a sample holder 16, an objective lens 18, an imaging device 20, an imaging control device 22, and a tilt mechanism. The control device 30, the control unit 32, the display unit 34, and the storage unit 36 are included.

The electron gun 10 emits an electron beam EB. In the electron gun 10, for example, electrons emitted from the cathode are accelerated by the anode and the electron beam EB is emitted.

The irradiation lens 12 focuses the electron beam EB emitted from the electron gun 10 and irradiates the sample S with the electron beam EB. The irradiation lens 12 is composed of a plurality (three in the illustrated example) of condenser lenses. The irradiation lens 12 constitutes an irradiation system 2 that irradiates the sample S with the electron beam EB. Although not shown, the irradiation system 2 may include a lens other than the irradiation lens 12, a diaphragm, and the like.

The sample stage 14 holds the sample S. In the illustrated example, the sample stage 14 holds the sample S via the sample holder 16. The sample S can be positioned by the sample stage 14. In the illustrated example, the sample stage 14 is a side-entry type sample stage in which the sample holder 16 is inserted into the pole piece of the objective lens 18 in the horizontal direction (sideways). The sample stage 14 may be a top entry type sample stage in which the sample S is inserted from above the pole piece of the objective lens 18. The sample stage 14 and the sample holder 16 have a sample tilting mechanism 15 for tilting the sample S. Further, the sample stage 14 has a sample moving mechanism for moving the sample S in the horizontal direction and the vertical direction.

The objective lens 18 is a first stage lens for forming a transmission electron microscope image (hereinafter also referred to as a “TEM image”) and an electron diffraction pattern with the electron beam EB that has passed through the sample S.

Although not shown, the electron microscope 100 includes an intermediate lens and a projection lens. The intermediate lens and the projection lens magnify the image formed by the objective lens 18 and form the image on the imaging device 20. The objective lens 18, the intermediate lens, and the projection lens form the image forming system 4 of the electron microscope 100. Although not shown, the image forming system 4 may include a lens other than the objective lens 18, the intermediate lens, and the projection lens, a diaphragm, and the like.

In the imaging system 4, the TEM image and the electron diffraction pattern can be imaged by the electrons transmitted through the sample S. For example, by adjusting the focus of the intermediate lens to the transmission electron microscope image (sample image) formed by the objective lens 18, the transmission electron microscope image can be captured by the imaging device 20. Further, for example, by focusing the intermediate lens on the electron diffraction pattern formed by the objective lens 18, the electron diffraction pattern can be photographed by the imaging device 20.

The imaging device 20 captures an image (a TEM image and an electron diffraction pattern) formed by the image forming system 4. The imaging device 20 is, for example, a digital camera such as a CCD (Charge Coupled Device) camera. The image data of the image captured by the imaging device 20 is output to the control unit 32 via the imaging control device 22. The image captured by the imaging device 20 is stored in the storage unit 36 as an image file and displayed on the display unit 34.

The imaging control device 22 operates the imaging device 20 based on the control signal from the control unit 32. The imaging control device 22 also sends the image data of the image captured by the imaging device 20 to the control unit 32. The tilt mechanism control device 30 operates the sample tilt mechanism 15 based on a control signal from the control unit 32.

The controller 32 controls the sample tilting mechanism 15. The control unit 32 performs a process of matching the incident direction of the electron beam EB with respect to the sample S and the crystal orientation of the sample S. The function of the control unit 32 can be realized, for example, by executing a program by various processors (CPU (Central Processing Unit) or the like).

The display unit 34 displays the image generated by the control unit 32, and the function thereof can be realized by an LCD (liquid crystal display) or the like. The display unit 34 displays, for example, an image captured by the imaging device 20.

The storage unit 36 serves as a work area of the control unit 32, and its function can be realized by a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk, and the like. The storage unit 36 stores programs and data for the control unit 32 to perform various control processes and calculation processes. The storage unit 36 is also used to temporarily store the calculation result and the like executed by the control unit 32 according to various programs.

FIG. 2 is a diagram for explaining the operation of the sample tilting mechanism 15. Note that FIG. 2 illustrates an X axis, a Y axis, and a Z axis as three axes that are orthogonal to each other. The Z axis is an axis that coincides with the optical axis of the irradiation system 2. That is, the electron beam EB is incident on the sample S along the Z axis. The X direction is the insertion direction of the sample holder 16.

The sample tilting mechanism 15 has an X tilting mechanism 15A and a Y tilting mechanism 15B. The X tilting mechanism 15A tilts the sample S in the X direction by rotating (tilting) the sample S around the Y axis. The X tilt mechanism 15A is provided on the sample holder 16, for example. The X tilting mechanism 15A tilts the sample S in the X direction by rotating the portion of the sample holder 16 supporting the sample S around the Y axis.

The Y tilting mechanism 15B tilts the sample S in the Y direction by rotating (tilting) the sample S around the X axis. The Y tilt mechanism 15B is provided on the sample stage 14, for example. The Y tilt mechanism 15B tilts the sample S in the Y direction by rotating the sample holder 16 around the X axis.

2. Method FIG. 3 and FIG. 4 are diagrams schematically showing electron diffraction patterns. When the crystalline sample S is irradiated with the electron beam EB, electron diffraction patterns as shown in FIGS. 3 and 4 can be obtained. The electron diffraction pattern shown in FIG. 3 is obtained when the incident direction of the electron beam EB on the sample S and the crystal orientation of the sample S match. The electron diffraction pattern shown in FIG. 4 is obtained when the incident direction of the electron beam EB on the sample S and the crystal orientation of the sample S are deviated. Normally, when the sample S is introduced into the sample chamber of the electron microscope 100, an electron diffraction pattern as shown in FIG. 4 is obtained. Therefore, by adjusting the inclination angle of the sample S so that the electron diffraction pattern shown in FIG. 3 is obtained, the incident direction of the electron beam EB to the sample S and the crystal orientation of the sample S are matched.

Hereinafter, a method of matching the incident direction of the electron beam EB with respect to the sample S and the tilt azimuth of the sample S will be described.

First, a plurality of electron diffraction patterns obtained at different tilt angles of the sample S are acquired. For example, while the tilt angle of the sample S is sequentially changed by the X tilt mechanism 15A and the Y tilt mechanism 15B, an electron diffraction pattern is photographed each time the tilt angle is changed. Thereby, a plurality of electron diffraction patterns can be acquired.

The angle range for changing the tilt angle of the sample S and the angle step for changing the tilt angle of the sample S can be set arbitrarily. The angle step for changing the tilt angle of the sample S (hereinafter, also referred to as “first angle step”) is preferably 2° or less. The reason why the first angle step is preferably 2° or less will be described later.

Next, the electron diffraction pattern having the largest number of electron diffraction spots is searched from the plurality of electron diffraction patterns.

For example, first, the electron diffraction pattern is binarized to separate the electron diffraction spot and the background. When binarized, the place where the electron diffraction spot is present is expressed in white, and the other regions are expressed in black. Next, a numbering is assigned to the electron diffraction spots by performing a labeling process for assigning a number to a portion where white pixels are continuous, and the number of electron diffraction spots is obtained.

FIG. 5 is a table showing the number of electron diffraction spots of a plurality of electron diffraction patterns obtained at different tilt angles. In the table shown in FIG. 5, a plurality of electron diffraction patterns are acquired by changing the tilt angle TX in the X direction in 1° steps and the tilt angle TY in the Y direction in 1° steps, and the number of electron diffraction spots is obtained. Is the result of seeking.

In the example shown in FIG. 5, the number of electron diffraction spots is largest when the tilt angle TX in the X direction is −2° and the tilt angle TY in the Y direction is TY=−2°. Hereinafter, the tilt angle at which the electron diffraction pattern having the largest number of electron diffraction spots is obtained is referred to as a first tilt angle.

Here, in the electron diffraction pattern, generally, when the incident angle of the electron beam EB with respect to the sample S and the crystal orientation of the sample S are deviated, the number of electron diffraction spots is small, and the electron beam EB with respect to the sample S When the incident angle and the crystal orientation of the sample S match, the number of electron diffraction spots is large. Therefore, it can be said that the first tilt angle is a tilt angle at which the deviation between the incident angle of the electron beam EB on the sample S and the crystal orientation of the sample S is relatively small.

Next, the tilt angle of the sample S is set to the first tilt angle. This makes it possible to start the process of adjusting the incident direction of the electron beam EB to the sample S and the crystal orientation of the sample S, which will be described below, with the tilt angle of the sample S set to the first inclination angle.

Next, a plurality of electron diffraction patterns obtained at different tilt angles of the sample S are acquired. For example, while sequentially changing the tilt angle in the Y direction using the Y tilt mechanism 15B, an electron diffraction pattern is photographed each time the tilt angle is changed. Thereby, a plurality of electron diffraction patterns can be acquired.

At this time, the angle range for changing the tilt angle of the sample S is an angle range centered on the first tilt angle. Further, the angle step for changing the inclination angle of the sample S (hereinafter also referred to as “second angle step”) is made smaller than the first angle step.

Next, the plurality of electron diffraction patterns obtained at the different tilt angles of the sample S are each approximated to a circle, and the tilt angle at which the radius of the circle is minimized is obtained.

For example, first, the center coordinates of each of the plurality of electron diffraction spots appearing in the electron diffraction pattern are obtained. Next, as shown in FIG. 9, circle approximation is performed from the center coordinates of the electron diffraction spot, and the coordinates and radius of the center of the circle are calculated. The circle approximation can be performed using a general mathematical method such as the least square method. Next, as shown in FIG. 10, a graph in which the radii of the approximate circles of the electron diffraction patterns of FIG. 9 are plotted is created, and the inclination angle at which the radius of the approximate circle is minimized (hereinafter referred to as “second inclination angle”). Ask). In this way, the second tilt angle in the Y direction can be obtained.

Note that the method of obtaining the tilt angle that minimizes the radius of the approximate circle is not limited to this, and other methods described in JP 2010-212067 A may be used, for example.

Next, while the tilt angle in the Y direction is set to the second tilt angle, the electron tilt pattern is photographed each time the tilt angle is changed while sequentially changing the tilt angle in the X direction using the X tilt mechanism 15A. Using the plurality of electron diffraction patterns obtained in this way, the second tilt angle in the X direction is obtained by using the same method as in the case of obtaining the second tilt angle in the Y direction.

Next, the tilt angle in the Y direction is the second tilt angle, and the tilt angle in the X direction is the second tilt angle.

Through the above steps, the incident direction of the electron beam EB with respect to the sample S and the tilt azimuth of the sample S can be matched.

Here, as shown in FIG. 11, when the deviation between the incident direction of the electron beam EB on the sample S and the crystal orientation of the sample S is large, the electron diffraction pattern cannot be approximated by a circle. According to the above method, a plurality of electron diffraction patterns obtained at different tilt angles are acquired with a small deviation between the incident direction of the electron beam EB with respect to the sample S and the crystal orientation of the sample S, and a plurality of electrons are acquired. The diffraction pattern can be approximated to a circle, and the tilt angle that minimizes the radius of the circle can be obtained. Therefore, according to the above method, the electron diffraction pattern can be accurately approximated by a circle. Therefore, the incident direction of the electron beam EB with respect to the sample S and the tilt azimuth of the sample S can be accurately matched.

In general, when the deviation between the incident direction of the electron beam EB on the sample S and the crystal orientation of the sample S is larger than 2°, the electron diffraction pattern cannot be accurately approximated by a circle. Therefore, as described above, the first angle step is preferably 2° or less.

3. Process FIG. 6 is a flowchart showing an example of the process of the control unit 32.

For example, the initial value of the tilt angle TX in the X direction is TX1, and the initial value of the tilt angle TY in the Y direction is TY1. Further, the interval at which the tilt angle TX in the X direction is changed is an angle step ΔTX, and the number of times (the number of steps) at which the tilt angle TX in the X direction is changed is NX. Further, an interval for changing the tilt angle TY in the Y direction is an angle step ΔTY, and the number of times (the number of steps) of changing the tilt angle TY in the Y direction is NY. At this time, the control unit 32 controls the sample tilting mechanism 15 according to the following equation.

TX=TX1+(m−(NX−1)/2)×ΔTX
TY=TY1+(n−(NY−1)/2)×ΔTY
Note that m is the number of times the tilt angle in the X direction is changed, and n is the number of times the tilt angle in the Y direction is changed.

The control unit 32 sets m=0 and n=0 (S100), causes the sample tilting mechanism 15 to set the tilt angle TX in the X direction to TX=TX1+((1-NX)/2)×ΔTX, and tilts in the Y direction. The angle TY is set to TY=TY1+((1-NX)/2)×ΔTY (S102). Then, the control unit 32 acquires the electron diffraction pattern imaged by the imaging device 20 (S104).

Next, the control unit 32 obtains the number N _spot (TX,TY) of electron diffraction spots in the acquired electron diffraction pattern (S106). The obtained number N _spot (TX,TY) of electron diffraction spots is stored in the storage unit 36 in association with the information on the tilt angle (TX,TY).

Next, the control unit 32 determines whether or not the number m of times the tilt angle in the X direction is changed is smaller than the step number NX-1 (S108).

When it is determined that the number of times m is smaller than the number of steps NX-1 (Yes in S108), the control unit 32 sets m=m+1 (S110) and sets the tilt angle TX in the X direction to the sample tilt mechanism 15 as TX=TX1+. ((3-NX)/2)*[Delta]TX, and the tilt angle TY in the Y direction is TY=TY1+((1-NY)/2)*[Delta]TY (S102). Then, the control unit 32 acquires the electron diffraction pattern imaged by the imaging device 20 (S104).

Next, the control unit 32 obtains the number N _spot (TX,TY) of electron diffraction spots in the acquired electron diffraction pattern (S106).

As described above, the control unit 32 performs step S102, step until the number m of times of changing the tilt angle in the X direction is determined not to be smaller than the step number NX-1, that is, m=NX-1. The processing of S104, step S106, step S108, and step S110 is repeated.

When it is determined that the number of times m is not smaller than the number of steps NX-1 (No in S108),
The control unit 32 sets the number of times n of changing the tilt angle in the Y direction to n=n+1 (S112), and determines whether the number of times n of changing the tilt angle in the Y direction is smaller than the number of steps NY (S114). ).

When it is determined that the number of times n is smaller than the number of steps NY (Yes in S114), the control unit 32 sets m=0 (S116) and sets the tilt angle TX in the X direction to the sample tilt mechanism 15 as TX=TX1+(( 1−NX)/2)×ΔTX, and the tilt angle TY in the Y direction is TY=TY1+((3-NY)/2)×ΔTY (S102). Then, the control unit 32 acquires the electron diffraction pattern imaged by the imaging device 20 (S104). Next, the control unit 32 obtains the number N _spot (TX,TY) of electron diffraction spots in the acquired electron diffraction pattern (S106).

In this way, the control unit 32 performs step S102, step until it is determined that the number n of times the tilt angle in the Y direction is changed is not smaller than the step number NY, that is, n=NY. The processing of S104, step S106, step S108, step S110, step S112, step S114, and step S116 is repeated. As a result, as shown in FIG. 5, the number of electron diffraction spots of a plurality of electron diffraction patterns obtained at different tilt angles can be obtained.

When it is determined that the number of times n is not smaller than the number of steps NY (No in S114), the control unit 32 searches for an electron diffraction pattern having the largest number of electron diffraction spots among the plurality of electron diffraction patterns (S118). The tilt angle (TX, TY) of the electron diffraction pattern having the largest number of electron diffraction spots is set as the first tilt angle (S120).

In the table shown in FIG. 5, when the tilt angle (TX, TY)=(−2°, −2°), the number of electron diffraction spots becomes maximum at Nspot(−2°, −2°)=39. .. Therefore, the first tilt angle in the X direction is determined to be −2° and the first tilt angle in the Y direction is determined to be −2°.

The controller 32 causes the sample tilting mechanism 15 to set the tilt angle of the sample S to the first tilt angle (S122).

Next, the controller 32 causes the Y tilt mechanism 15B to sequentially change the tilt angle of the sample S within an angle range including the first tilt angle in the Y direction, and acquires a plurality of electron diffraction patterns obtained at different tilt angles. (S124). Next, the control unit 32 approximates each of the acquired electron diffraction patterns to a circle, and obtains the second tilt angle in the Y direction that minimizes the radius of the circle (S126).

Next, the control unit 32 causes the X tilt mechanism 15A to sequentially change the tilt angle of the sample S within an angle range including the first tilt angle in the X direction with the tilt angle TY in the Y direction set to the second tilt angle. , A plurality of electron diffraction patterns obtained at different tilt angles are acquired (S128). Next, the control unit 32 approximates each of the acquired electron diffraction patterns to a circle to obtain a second tilt angle in the X direction that minimizes the radius of the circle (S130).

Next, the controller 32 causes the X tilt mechanism 15A to set the tilt angle TX in the X direction to the second tilt angle, and causes the Y tilt mechanism 15B to set the tilt angle TY in the Y direction to the second tilt angle (S132).

Through the above processing, the incident direction of the electron beam EB with respect to the sample S and the crystal orientation of the sample S can be matched.

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

In the electron microscope 100, the control unit 32 causes the sample tilting mechanism 15 to sequentially change the tilt angle of the sample S and acquires a plurality of first electron diffraction patterns obtained at different tilt angles, and a plurality of first electron diffraction patterns. A process of searching a first electron diffraction pattern having the largest number of diffraction spots from the electron diffraction pattern to obtain a first tilt angle that is a tilt angle at which the first electron diffraction pattern having the largest number of diffraction spots is obtained; I do. In addition, the control unit 32 causes the sample tilting mechanism 15 to sequentially change the tilt angle of the sample S within an angle range including the first tilt angle, and acquires a plurality of second electron diffraction patterns obtained at different tilt angles. The process, the process of approximating each of the plurality of second electron diffraction patterns into a circle to obtain the second tilt angle that minimizes the radius of the circle, and the sample tilting mechanism 15 set the tilt angle of the sample S to the second tilt angle. Processing and.

As described above, in the electron microscope 100, the first tilt angle with a small deviation between the incident angle of the electron beam EB with respect to the sample S and the crystal orientation of the sample S is obtained, and the tilt angle is changed within the angle range including the first tilt angle. , A plurality of second electron diffraction patterns are acquired. Therefore, the second electron diffraction pattern can be accurately approximated to a circle. Therefore, according to the electron microscope 100, the incident angle of the electron beam EB with respect to the sample S and the crystal orientation of the sample S can be accurately matched.

In the electron microscope 100, the angle range including the above-described first tilt angle is an angle range centered on the first tilt angle. Therefore, in the electron microscope 100, the incident angle of the electron beam EB with respect to the sample S and the crystal orientation of the sample S can be accurately matched.

In the electron microscope 100, in the process of acquiring the first electron diffraction pattern, the tilt angle is changed in the first angle step, and in the process of acquiring the second electron diffraction pattern, the second angle step smaller than the first angle step. Change the tilt angle. Therefore, in the electron microscope 100, the incident angle of the electron beam EB with respect to the sample S and the crystal orientation of the sample S can be matched efficiently and accurately.

5. Modified example 5.1. First Modified Example FIG. 7 is a flowchart showing an example of processing of the control unit 32 of the electron microscope according to the first modified example. In FIG. 7, steps that perform the same processing as in FIG. 6 are given the same reference numerals. Hereinafter, points different from the processing of the control unit 32 of the electron microscope 100 described above will be described, and description of the same points will be omitted.

In the above-described electron microscope 100, as shown in FIG. 6, the control unit 32 searches for an electron diffraction pattern having the largest number of diffraction spots from a plurality of electron diffraction patterns (S118), and has the largest number of diffraction spots. The first tilt angle, which is the tilt angle at which the electron diffraction pattern was obtained, was determined (S120).

On the other hand, in the electron microscope according to the first modification, as shown in FIG. 7, the control unit 32 searches for an electron diffraction pattern most similar to the template image from the plurality of electron diffraction patterns (S200), The first tilt angle, which is the tilt angle at which the electron diffraction pattern most similar to the template image is obtained, is obtained (S202). The template image is an electron diffraction pattern obtained in a state where the incident direction of the electron beam EB on the sample S and the crystal orientation of the sample S match.

For example, an electron diffraction pattern obtained in a state where the incident direction of the electron beam EB with respect to the sample S and the crystal orientation of the sample S are preliminarily stored in the storage unit 36 as a template image. The control unit 32 obtains the degree of similarity with the template image for each of the plurality of electron diffraction patterns obtained at different tilt angles. Then, the tilt angle at which the electron diffraction pattern with the highest degree of similarity is obtained is determined as the first tilt angle. The method of obtaining the degree of similarity is not particularly limited, and known image processing by template matching can be used.

The electron microscope according to the first modification can achieve the same effects as the electron microscope 100 described above.

5.2. Second Modified Example FIG. 8 is a flowchart showing an example of processing of the control unit 32 of the electron microscope according to the second modified example. In FIG. 8, steps that perform the same processing as in FIG. 6 are assigned the same reference numerals. Hereinafter, points different from the processing of the control unit 32 of the electron microscope 100 described above will be described, and description of the same points will be omitted.

In the electron microscope 100 described above, as shown in FIG. 6, the control unit 32 causes the sample tilting mechanism 15 to set the tilt angle of the sample S to the first tilt angle (S122).

On the other hand, in the electron microscope according to the second modification, as shown in FIG. 8, the control unit 32 does not cause the sample tilting mechanism 15 to perform the process of setting the tilt angle of the sample S to the first tilt angle. After determining the first tilt angle (after step S120), the control unit 32 causes the angle range for changing the tilt angle of the sample S to include the first tilt angle in the processes of steps S124 and S128. To do. This allows the electron diffraction pattern to be accurately approximated by a circle. In addition, it is preferable that the angle range in which the tilt angle of the sample S is changed is an angle range centered on the first tilt angle. Thereby, the minimum value of the radius of the approximate circle of the electron diffraction pattern can be obtained more accurately.

The electron microscope according to the first modification can achieve the same effects as the electron microscope 100 described above.

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 combined appropriately.

The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations having the same function, method and result, or configurations having the same purpose and effect). Further, the invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Further, the invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes configurations in which known techniques are added to the configurations described in the embodiments.

2... Irradiation system, 4... Imaging system, 10... Electron gun, 12... Irradiation lens, 14... Sample stage, 15... Sample tilting mechanism, 15A... X tilting mechanism, 15B... Y tilting mechanism, 16... Sample holder, 18 ... objective lens, 20... imaging device, 22... imaging control device, 30... tilting mechanism control device, 32... control unit, 34... display unit, 36... storage unit, 100... electron microscope

Claims (4)

An irradiation system for irradiating a sample with an electron beam,
A sample tilting mechanism for tilting the sample,
An image forming system for forming an image with electrons transmitted through the sample;
An image pickup device for picking up an image formed by the image forming system;
A control unit for controlling the sample tilting mechanism,
Including
The control unit is
A process of sequentially changing the inclination angle of the sample by the sample inclination mechanism, and acquiring a plurality of first electron diffraction patterns obtained at different inclination angles,
The first electron diffraction pattern having the largest number of diffraction spots is searched for from the plurality of first electron diffraction patterns, and the first electron diffraction pattern having the largest number of diffraction spots is obtained. The process of obtaining the tilt angle,
A process of sequentially changing the tilt angle of the sample in the angle range including the first tilt angle in the sample tilt mechanism, and acquiring a plurality of second electron diffraction patterns obtained at different tilt angles;
A process of approximating each of the plurality of second electron diffraction patterns by a circle to obtain a second tilt angle at which the radius of the circle is minimized;
A process of causing the sample tilting mechanism to set a tilt angle of the sample to a second tilt angle;
Do an electron microscope. An irradiation system for irradiating a sample with an electron beam,
A sample tilting mechanism for tilting the sample,
An image forming system for forming an image with electrons transmitted through the sample;
An image pickup device for picking up an image formed by the image forming system;
A control unit for controlling the sample tilting mechanism,
Including
The control unit is
A process of sequentially changing the inclination angle of the sample by the sample inclination mechanism and acquiring a plurality of first electron diffraction patterns obtained at different inclination angles;
The first tilt that is the tilt angle at which the first electron diffraction pattern that most resembles the template image is searched for from the plurality of first electron diffraction patterns and the first electron diffraction pattern that most resembles the template image is obtained. The process of finding the corner,
A process of sequentially changing the tilt angle of the sample within an angle range including the first tilt angle in the sample tilt mechanism, and acquiring a plurality of second electron diffraction patterns obtained at different tilt angles;
Circle-approximating each of the plurality of second electron diffraction patterns to obtain a second inclination angle at which the radius of the circle is minimized;
A process of causing the sample tilting mechanism to set a tilt angle of the sample to a second tilt angle;
And then
An electron microscope, wherein the template image is an electron diffraction pattern obtained in a state where an incident direction of the electron beam with respect to the sample and a crystal orientation of the sample coincide with each other. In claim 1 or 2,
The electron microscope, wherein the angle range is an angle range centered on the first tilt angle. In any one of Claim 1 thru|or 3,
In the process of acquiring the first electron diffraction pattern, the tilt angle is changed in the first angle step, and in the process of acquiring the second electron diffraction pattern, the tilt angle is changed in the second angle step smaller than the first angle step. Change the electron microscope.

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