Transmission electron microscope and sample analysis method using transmission electron microscope

Abstract

To provide a transmission electron microscope, which can analyze a sample over a wide range and with high resolution.SOLUTION: A transmission electron microscope includes: an irradiation section that can irradiate a sample with a parallel electron beam at a predetermined incident angle; a sample holding section that can hold the sample; an aperture section that is located downstream in a traveling direction of the electron beam transmitted the sample or scattered by the sample, and that has an opening; an image forming lens that is located downstream in the traveling direction of the electron beam with respect to the opening of the aperture section and that forms an image of the electron beam selected by the aperture section; an image capturing section that is located downstream in the traveling direction of the electron beam with respect to the image forming lens, that captures a bright-field image and a dark-field image formed by the image forming lens, and that has an imaging surface; and an analysis section that analyzes the sample on the basis of the bright-field image and the dark-field image.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE An embodiment of the present invention relates to a transmission electron microscope and a method of analyzing a sample using the transmission electron microscope. [Background technology]

[0002] In a transmission electron microscope, an electron beam is emitted from an irradiation section including an electron gun. The irradiated electron beam passes through or is scattered by a sample. The electron beam is imaged by an imaging section. The image obtained by the imaging section is used for analyzing the sample. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-017424 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments is to provide a transmission electron microscope capable of analyzing a sample over a wide range and with high resolution, and a method of analyzing a sample using the transmission electron microscope. [Means for solving the problem]

[0005] The transmission electron microscope of the embodiment includes an irradiation unit capable of irradiating a parallel electron beam onto a sample at a predetermined angle of incidence, a sample holding unit capable of holding a sample, an aperture unit located downstream in the traveling direction of the electron beam that has passed through the sample or been scattered by the sample and having an opening, an imaging lens located downstream of the opening of the aperture unit in the traveling direction of the electron beam and forming an image of the electron beam selected by the aperture unit, an imaging unit located downstream of the imaging lens in the traveling direction of the electron beam and having an imaging surface that captures bright field and dark field images formed by the imaging lens, and an analysis unit that analyzes the sample based on the bright field and dark field images. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of a transmission electron microscope according to an embodiment. [Diagram 2] 4 is a schematic diagram for explaining the angle of incidence of an electron beam e with respect to a sample in the embodiment. FIG. [Diagram 3] 1 is a flowchart of a sample analysis method using a transmission electron microscope of an embodiment. [Figure 4] 1A to 1C are schematic diagrams showing an example of a sample analysis method using a transmission electron microscope according to an embodiment. [Diagram 5] 1A to 1C are schematic diagrams showing an example of a sample analysis method using a transmission electron microscope according to an embodiment. [Figure 6] 1A to 1C are schematic diagrams showing an example of a sample analysis method using a transmission electron microscope according to an embodiment. [Figure 7] 1A to 1C are schematic diagrams showing an example of a sample analysis method using a transmission electron microscope according to an embodiment. [Figure 8] 1A to 1C are schematic diagrams showing an example of a sample analysis method using a transmission electron microscope according to an embodiment. [Figure 9] FIG. 11 is a schematic diagram showing another example of a sample analysis method using the transmission electron microscope of the embodiment. [Figure 10] FIG. 11 is a schematic diagram showing another example of a sample analysis method using the transmission electron microscope of the embodiment.

[0007] Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0008] In this specification, in order to indicate the positional relationship of parts, etc., the upward direction of the drawing is described as "upper" and the downward direction of the drawing is described as "lower." In this specification, the concepts of "upper" and "lower" are not necessarily terms that indicate a relationship with the direction of gravity.

[0009] (Embodiment) The transmission electron microscope of the embodiment includes an irradiation unit capable of irradiating a parallel electron beam onto a sample at a predetermined angle of incidence, a sample holding unit capable of holding a sample, an aperture unit located downstream in the traveling direction of the electron beam that has passed through the sample or been scattered by the sample and having an opening, an imaging lens located downstream of the opening of the aperture unit in the traveling direction of the electron beam and forming an image of the electron beam selected by the aperture unit, an imaging unit located downstream of the imaging lens in the traveling direction of the electron beam and having an imaging surface that captures bright field and dark field images formed by the imaging lens, and an analysis unit that analyzes the sample based on the bright field and dark field images.

[0010] Fig. 1 is a schematic diagram of a transmission electron microscope 100 according to an embodiment. Fig. 2 is a schematic diagram for explaining the angle of incidence of an electron beam e with respect to a sample according to the embodiment.

[0011] The transmission electron microscope 100 includes an irradiation unit 2, a sample holder 4, an objective lens 6, an aperture unit 8, an imaging lens 9, an image capture unit 10, a control unit 12, and an analysis unit 14.

[0012] The sample S has a sample surface S1.

[0013] The imaging unit 10 has an imaging surface 11 .

[0014] The irradiation unit 2 has an electron gun (not shown). The electron gun emits an electron beam e. The irradiation unit 2 further has, for example, a focusing lens (not shown). The focusing lens can form an electric field and a magnetic field that can focus the electron beam e while maintaining the parallelism of the electron beam. The focusing lens makes the electron beam e emitted from the electron gun a parallel electron beam. The focusing lens is, for example, an electromagnetic lens. The irradiation unit 2 may have multiple focusing lenses (not shown) to ensure the parallelism and focussing of the electron beam e.

[0015] Here, the X direction, the Y direction perpendicular to the X direction, and the Z direction perpendicular to the X direction are defined. The sample surface S1 of the sample S, the aperture unit 8, and the imaging surface 11 of the imaging unit 10 are provided in a plane perpendicular to the Z direction. The sample surface S1 of the sample S, the aperture unit 8, and the imaging surface 11 of the imaging unit 10 are provided parallel to the XY plane.

[0016] The electron beam e is made incident on the sample surface S1 of the sample S by the irradiation unit 2 at a predetermined angle of incidence.

[0017] Here, the predetermined angle will be described. As shown in Fig. 2(a), in a plane parallel to the XY plane, the electron beam e is incident on the sample surface S1 of the sample S at an angle φ with respect to the X direction.

[0018] Also, as shown in FIG. 2(b), the electron beam e is incident on the sample surface S1 of the sample S at an angle θ with respect to the -Z direction. This will be further explained with reference to FIG. 2(c) and FIG. 2(d). As shown in FIG. 2(c), in a plane parallel to the XZ plane, the electron beam e is incident on the sample surface S1 of the sample S at an angle θx (tiltX) with respect to the -Z direction. Also, as shown in FIG. 2(d), in a plane parallel to the YZ plane, the electron beam e is incident on the sample surface S1 of the sample S at an angle θy (tiltY) with respect to the -Z direction.

[0019] The angle φ, the angle θx (tiltX), and the angle θy (tiltY) can be changed by using, for example, a deflector (polarizer) of the irradiation unit 2 (not shown).

[0020] 2(b), 2(c), and 2(d) also show the optical axis O of the transmission electron microscope 100. The optical axis O is, for example, parallel to the Z axis.

[0021] The sample S is held by the sample holder 4 so that the sample surface S1 is parallel to the XY plane.

[0022] The electron beam e that has passed through the sample S or has been scattered by the sample S is imaged on an imaging surface 11 of an imaging unit 10 using an objective lens 6 and an aperture unit 8 located downstream in the traveling direction of the electron beam e. Here, the downstream side in the traveling direction of the electron beam e is the -Z direction side.

[0023] The objective lens 6 is, for example, an electromagnetic lens.

[0024] The diaphragm portion 8 has a thickness in a direction parallel to the Z direction that is sufficient to block the electron beam e. The diaphragm portion 8 has an opening 8a. The electron beam e can pass through the opening 8a.

[0025] The imaging lens 9 includes, for example, an electromagnetic lens. Note that the imaging lens 9 may include a mechanism used for other imaging (not shown).

[0026] The imaging unit 10 is, for example, a camera. The imaging surface 11 is, for example, a surface on which an imaging element of the camera is provided. A bright-field image (BF image: Bright-field imaging) or a dark-field image (DF image: Dark-field imaging) of the sample S is formed on the imaging surface 11 by the diaphragm unit 8 and the imaging lens 9.

[0027] The imaging unit 10 captures a bright-field image and a dark-field image formed on an imaging surface 11 .

[0028] Here, the bright-field image is an image obtained by imaging only the electron beam e that has passed through the sample S. The dark-field image is an image obtained by imaging only a specific portion of the electron beam e that has been scattered by the sample S.

[0029] The control unit 12, for example, controls the emission of the electron beam e from the electron gun of the irradiation unit 2, the focusing of the electron beam e by the focusing lens of the irradiation unit 2, and the incident angle of the electron beam e to the sample S by the irradiation unit 2. The control unit 12 also controls, for example, the excitation amount of the objective lens 6 to control the focus of the bright field image and the dark field image. The control unit 12 also controls, for example, the movement of the aperture unit 8 in the XY plane. The control unit 12 also controls, for example, the size of the opening 8a of the aperture unit 8. The control unit 12 also controls, for example, the exposure time of the imaging unit 10. The control unit 12 may also control, for example, the movement of the sample S using the sample holder 4 and the tilt of the sample S.

[0030] The analysis section 14 analyzes the sample S based on the bright-field image and the dark-field image captured by the imaging section 10.

[0031] The control unit 12 and the analysis unit 14 are, for example, electronic circuits, and are, for example, computers configured by a combination of hardware such as an arithmetic circuit and software such as a program.

[0032] Fig. 3 is a flowchart of a sample analysis method using the transmission electron microscope 100 of the embodiment. Fig. 4 to Fig. 8 are schematic diagrams showing an example of a sample analysis method using the transmission electron microscope 100 of the embodiment.

[0033] A sample analysis method using a transmission electron microscope according to an embodiment involves irradiating a parallel electron beam onto a sample at a predetermined angle of incidence, forming an image of the electron beam using an imaging lens, the electron beam being selected by an aperture section having an opening and positioned downstream in the direction of travel of the electron beam that has passed through or been scattered by the sample, capturing bright-field and dark-field images formed by the imaging lens, and analyzing the sample based on the bright-field and dark-field images.

[0034] A sample analysis method using the transmission electron microscope 100 of the embodiment will be described with reference to FIGS.

[0035] First, the sample S is placed on the sample holder 4 (S102 in FIG. 3).

[0036] Next, the control unit 12, for example, controls the irradiation unit 2 to set an irradiation point on the sample S to which the electron beam is irradiated (S104 in FIG. 3). Here, the irradiation point is defined by, for example, the X coordinate (X0) and the Y coordinate (Y0) on the sample S. In other words, the irradiation point is information indicating which irradiation point on the sample S is to be irradiated with the electron beam. For example, using the control unit 12 and the irradiation unit 2, the observation area, which is the irradiation point on the sample S, is brought to the center of the field of view of the transmission electron microscope.

[0037] Next, the control unit 12 sets the irradiation angles (tiltX0 and tiltY0) of the electron beam with respect to the set irradiation point (S106). Next, the control unit 12 acquires a bright-field image (BF image) and a dark-field image (DF image) using the imaging unit 10 (S108).

[0038] Next, the control unit 12 judges whether acquisition of a bright-field image (BF image) and a dark-field image (DF image) at the last irradiation angle at the irradiation point is completed (S110). If it is determined that acquisition of a bright-field image (BF image) and a dark-field image (DF image) at the last irradiation angle is not completed (S110, No), a new electron beam irradiation angle (tiltX1 and tiltY1) is set (S112). In other words, if acquisition of a bright-field image (BF image) and a dark-field image (DF image) at the last irradiation angle is not completed, the electron beam irradiation angle is changed from the previous value (tiltXi and tiltYi) to the next value (tiltXi+1 and tiltYi+1). Then, a bright-field image (BF image) and a dark-field image (DF image) are acquired at the new electron beam irradiation angle (tiltX1 and tiltY1) (S108).

[0039] When it is determined that the acquisition of the bright-field image (BF image) and the dark-field image (DF image) at the last irradiation angle has been completed (S110, Yes), it is determined whether the acquisition of the bright-field image (BF image) and the dark-field image (DF image) at the last irradiation point has been completed (S114, Yes). When it is determined that the acquisition of the bright-field image (BF image) and the dark-field image (DF image) at the last irradiation point has not been completed (S114, No), a new electron beam irradiation point (X1 and Y1) is set (S116). In other words, when the acquisition of the bright-field image (BF image) and the dark-field image (DF image) at the last irradiation point has not been completed, the electron beam irradiation position is changed from the previous value (Xi and Yi) to the next value (Xi+1 and Yi+1). Then, the irradiation angles (tiltX0 and tiltY0) of the electron beam are set at the new irradiation point (X1 and Y1) of the electron beam (S106), and a bright-field image (BF image) and a dark-field image (DF image) are acquired (S108). Here, the irradiation position of the electron beam is changed by, for example, moving the sample S using the control unit 12.

[0040] When it is determined that acquisition of the bright-field image (BF image) and the dark-field image (DF image) at the last irradiation point has been completed (S114, Yes), the analysis unit 14 performs an analysis of the sample S based on the obtained bright-field image and dark-field image, and obtains an analysis result (S118). This analysis will be described below.

[0041] Here, for convenience, Fig. 4(c), Fig. 5(c), Fig. 6(c), Fig. 7(c) and Fig. 8(c) show the same image. For convenience, Fig. 4(d), Fig. 5(d), Fig. 6(d), Fig. 7(d) and Fig. 8(d) show the same image. For convenience, Fig. 4(e), Fig. 5(e), Fig. 6(e), Fig. 7(e) and Fig. 8(e) show the same image. For convenience, Fig. 4(f), Fig. 5(f), Fig. 6(f), Fig. 7(f) and Fig. 8(f) show the same image. For convenience, Fig. 4(g), Fig. 5(g), Fig. 6(g), Fig. 7(g) and Fig. 8(g) show the same image.

[0042] For example, as shown in Fig. 4(a), consider a case where the irradiation unit 2 and the aperture unit 8 are controlled to change the incident angle of the electron beam e, the electron beam e that has passed through the sample S is blocked by the aperture unit 8, and an image of the electron beam e scattered by the sample S is captured. The image captured in this case is a dark field image (DF image) shown in Fig. 4(g).

[0043] 5(a), for example, consider a case where the irradiation unit 2 and the aperture unit 8 are controlled to change the incident angle of the electron beam e, the electron beam e that has passed through the sample S is blocked by the aperture unit 8, and the electron beam e scattered by the sample S is imaged. The image captured in this case is a dark field image (DF image) shown in FIG. 5(f).

[0044] Also, for example, as shown in Fig. 6(a), consider a case where the irradiation unit 2 and the aperture unit 8 are controlled to change the incident angle of the electron beam e, the electron beam e scattered by the sample S is blocked by the aperture unit 8, and the electron beam e transmitted through the sample S is imaged. The image captured in this case is a bright field image (BF image) shown in Fig. 6(e).

[0045] 7(a), for example, consider a case where the irradiation unit 2 and the aperture unit 8 are controlled to change the incident angle of the electron beam e, the electron beam e that has passed through the sample S is blocked by the aperture unit 8, and the electron beam e scattered by the sample S is imaged. The image captured in this case is a dark field image (DF image) shown in FIG. 7(d).

[0046] 8(a), for example, consider a case where the irradiation unit 2 and the aperture unit 8 are controlled to change the incident angle of the electron beam e, the electron beam e that has passed through the sample S is blocked by the aperture unit 8, and the electron beam e scattered by the sample S is imaged. The image captured in this case is a dark field image (DF image) shown in FIG. 8(c).

[0047] The analysis unit 14 preferably performs analysis using the respective electron beam intensities in a plurality of images, including bright-field images (BF images) or dark-field images (DF images), obtained using a plurality of angles of incidence. An example of such an analysis is described below.

[0048] It is preferable that the analysis unit 14 analyzes the sample based on data D in which the electron beam intensity of a bright-field image or a dark-field image obtained for one of a plurality of incidence angles is plotted, with a first axis being a first angle (an example of θx or tiltX) of the incidence angle in a first direction (an example of X direction) parallel to the imaging surface, and a second axis being a second angle (an example of θy or tiltY) of the incidence angle in a second direction parallel to the imaging surface and intersecting the first direction.

[0049] For example, in Fig. 4(a), Fig. 5(a), Fig. 6(a), Fig. 7(a) and Fig. 8(a), it is assumed that bright-field images (BF images) and dark-field images (DF images) are acquired when the tiltX value is changed while the tiltY value is kept constant for the angle of incidence of the electron beam e. Fig. 4(b), Fig. 5(b), Fig. 6(b), Fig. 7(b) and Fig. 8(b) are a summary of data D in which the electron beam intensity of a bright-field image or a dark-field image is plotted against tiltX and tiltY. The white arrows shown in each figure are used to indicate data D plotted corresponding to each tiltX and tiltY. It is preferable that the plot of the electron beam intensity is performed by processing the electron beam intensity within a range of the bright-field image or the dark-field image that is larger than 3 nm square and smaller than 10 μm square. If it is within a range of 3 nm square or less, the range is too small and the variation in the electron beam intensity becomes large, making it impossible to perform a stable analysis. On the other hand, if the area is 10 μm square or more, the area is too large and multiple crystal grains and amorphous parts are mixed in, making it impossible to obtain valid analysis results. Here, "processing" refers to, for example, integrating the electron beam intensity within an area larger than 3 nm and smaller than 10 μm square. However, "processing" here is not limited to integration processing.

[0050] In Figures 4(b), 5(b), 6(b), 7(b) and 8(b), the positions of the data obtained by acquiring bright-field images (BF images) and dark-field images (DF images) using Figures 4(a), 5(a), 6(a), 7(a) and 8(a) are indicated by white arrows.

[0051] The electron beam intensity is indicated by color. A large number of white areas indicate high electron beam intensity. A large number of black areas indicate low electron beam intensity.

[0052] By varying tiltX and tiltY, the data shown in Figures 4(b), 5(b), 6(b), 7(b) and 8(b) can be obtained.

[0053] Fig. 9 is a schematic diagram showing another example of a sample analysis method using the transmission electron microscope 100 of the embodiment. Here, the sample analysis method shown in Fig. 9(a) corresponds to the example of the sample analysis method described using Figs. 4 to 8, for example. The sample analysis method shown in Fig. 9(b) is a sample analysis method in which data D of the electron beam intensity is plotted against the distance (r) from the center on the sample S and the angle (θ) from a predetermined direction parallel to the XY plane. Either sample analysis method can be preferably used. Other methods can also be used.

[0054] FIG. 10 is a schematic diagram showing another example of a sample analysis method using the transmission electron microscope 100 of the embodiment. The analysis unit 14 classifies the sample S into crystal, non-crystal, or crystal grain based on the above data. FIG. 10(a) is an example of a transmission electron microscope photograph of the sample S. Regions 1, 3, and 5 are amorphous (non-crystalline) regions. Regions 2, 4, and 6 are crystal grain portions. FIG. 10(b) is data D obtained by plotting the electron beam intensity of a bright-field image or a dark-field image, with a first axis being a first angle (an example of θx or tiltX) of the angle of incidence in a first direction (an example of X direction) parallel to the imaging plane, and a second axis being a second angle (an example of θy or tiltY) of the angle of incidence in a second direction parallel to the imaging plane and intersecting the first direction, corresponding to each region shown in FIG. 10(a). In the cases of regions 1, 3, and 5, the center is the maximum intensity in all cases. In contrast, in the cases of regions 2, 4, and 6, high intensity portions are found in areas other than the center. In this manner, it is possible to classify the sample S as crystalline, non-crystalline, or crystalline grain.

[0055] The analyses performed by the analysis unit 14 are not limited to those described above.

[0056] It is also preferable that the control unit 12 performs hollow cone irradiation of the electron beam e using the irradiation unit 2. In hollow cone irradiation, the electron beam e is formed into a hollow cone pattern and then irradiated onto the sample S. In this case, it is possible to reduce the influence of inelastic scattering, which causes blurring and reduced contrast in the captured image. In addition, since electrons with small scattering angles are excluded, it is possible to suppress the multiple scattering effect that deteriorates the captured image. In addition, in the case of hollow cone irradiation, it is not necessary to obtain a bright field image and perform analysis based on the bright field image.

[0057] Next, the effects of the transmission electron microscope according to the embodiment will be described.

[0058] For example, analysis using nano-beam diffraction (NBD) requires focusing an electron beam on a very small area on the sample S for measurement, which results in a narrow measurement range and a long measurement time.

[0059] In contrast, when using the transmission electron microscope of the embodiment, the electron beam can be irradiated onto a large area on the sample S and measurements can be performed at various angles, resulting in a wide measurement range and a short measurement time.

[0060] According to the embodiment of the transmission electron microscope and the sample analysis method using the transmission electron microscope, it is possible to provide a transmission electron microscope and a sample analysis method using the transmission electron microscope that can analyze a sample over a wide range and with high resolution.

[0061] Although some embodiments and examples of the present invention have been described, these embodiments and examples are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0062] 2: Irradiation section 4: Sample holder 6: Objective lens 8: Aperture section 8a: Aperture 9: Imaging lens 10: Imaging section 11: Imaging surface 12: Control section 14: Analysis section 100: Transmission electron microscope D: Data O: Optical axis S: Sample S1: Sample surface e: Electron beam θ: Angle θx: Angle θy: Angle φ: Angle

Claims

1. an irradiation unit capable of irradiating a parallel electron beam at a predetermined incident angle to a sample; A sample holder capable of holding the sample; a diaphragm portion having an opening and located downstream in a traveling direction of the electron beam that has been transmitted through the sample or scattered by the sample; an imaging lens that is located downstream of an opening of the diaphragm in a traveling direction of the electron beam and that forms an image of the electron beam selected by the diaphragm; an imaging unit having an imaging surface that is located downstream of the imaging lens in a traveling direction of the electron beam and captures a bright field image and a dark field image formed by the imaging lens; an analysis unit that analyzes the sample based on the bright-field image and the dark-field image; A transmission electron microscope equipped with a

2. The analysis unit performs analysis using the respective electron beam intensities in a plurality of images, including the bright-field image or the dark-field image, obtained using a plurality of the incidence angles.

2. The transmission electron microscope according to claim 1.

3. the analysis unit performs an analysis of the sample based on data obtained by plotting electron beam intensity of the bright-field image or the dark-field image obtained for one of the plurality of incidence angles, with a first axis being a first angle of the incidence angle in a first direction parallel to the imaging plane and a second axis being a second angle of the incidence angle in a second direction parallel to the imaging plane and intersecting the first direction.

2. The transmission electron microscope according to claim 1.

4. The analysis unit processes and plots electron beam intensities within a range of greater than 3 nm square and smaller than 10 μm square of the bright-field image or the dark-field image.

4. The transmission electron microscope according to claim 3.

5. The analysis unit classifies the sample as crystalline, amorphous, or crystalline based on the data.

4. The transmission electron microscope according to claim 3.

6. A parallel electron beam is irradiated onto the sample at a predetermined angle of incidence. a diaphragm portion having an aperture and positioned downstream in a traveling direction of the electron beam that has passed through the sample or been scattered by the sample, the diaphragm portion selecting the electron beam and using an imaging lens to form an image; capturing a bright-field image and a dark-field image formed by the imaging lens; analyzing the sample based on the bright-field image and the dark-field image; A method for analyzing samples using a transmission electron microscope.

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