Transmission electron microscope system

Abstract

A transmission electron microscope system according to the present invention comprises an electron gun, deflectors 7a, 7b, an objective lens 4, an objective aperture 10, a detection unit which is for detecting an electron beam that has passed through a sample 9, and a control unit which can generate an observation image of the sample 9 on the basis of a detection signal from the detection unit. The deflection angle of the electron beam 16 is adjusted by the deflectors 7a, 7b so that the sample 9 is irradiated with the electron beam 16 while the electron beam 16 precesses at a prescribed angle with respect to the optical axis 70. A zero-order diffracted wave 19 and a first-order diffracted wave 20 which are generated by the electron beam 16 passing through the sample 9 are passed through the objective aperture 10. The detection signal of the zero-order diffracted wave 19 and the first-order diffracted wave 20 which have passed through the objective aperture 10 is detected by the detection unit 50. On the basis of the detection signal, a hollow-cone bright-field TEM image is generated.

Description

Transmission Electron Microscope System

[0001] The present invention relates to a transmission electron microscope system, and more particularly to a transmission electron microscope system capable of generating an observation image of a sample and measuring the length of the sample.

[0002] A transmission electron microscope (TEM) is a device that irradiates a highly accelerated electron beam onto a material to be observed, and forms an image of the electrons that have passed through or scattered through the sample, thereby observing its microstructure. The obtained observation image (TEM image) makes it possible to evaluate the material properties of a microscopic region of the sample.

[0003] For example, in the TEM image obtained in Patent Document 1, the direction in which enhanced contrast occurs is observed to change continuously and periodically by periodically moving the diffraction spot. Enhanced contrast can be obtained from various directions for the structure contained in the sample. Isotropic image contrast can be obtained by integrating the enhanced contrast from various directions.

[0004] In Patent Document 2, an electron beam is irradiated onto a sample while precessing at a predetermined angle relative to the optical axis. At this time, the deflection angle of the electron beam is controlled by a beam deflector so that, of the diffracted waves and / or scattered waves generated by the electron beam passing through the sample, only the diffracted waves and / or scattered waves at a desired angle pass through the objective movable aperture. This allows a hollow-cone dark-field TEM image to be acquired.

[0005] International Publication No. 2018 / 037444 International Publication No. 2020 / 217456

[0006] In the semiconductor industry, for example, samples containing multilayer films are observed using TEM to measure the thickness of the films within the multilayer film. Measurement of multilayer films requires high accuracy of sub-nanometer or better. For example, in the case of an ONO film (silicon oxide / silicon nitride / silicon oxide) that serves as the gate insulating film in semiconductor samples, it is necessary to measure the thickness of each film, making edge detection of the boundaries between each film important.

[0007] The ONO film is composed of light elements and has an amorphous structure. However, in normal TEM observation, the granular structure contained in the amorphous layer is observed as a granular contrast. This granular structure interferes with edge detection in length measurement. Line profiles are acquired from TEM images to measure the thickness of each film, but the contrast of the granular structure increases the variation in the line profile of the amorphous layer, resulting in a wide distribution width. This poses a problem in that high-precision length measurement is not possible.

[0008] Therefore, there is a demand for a technology that can suppress the contrast of the granular structure contained in the amorphous layer, and a technology that can perform highly accurate length measurements.

[0009] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0010] A brief summary of a representative embodiment of the present invention will be given below.

[0011] In one embodiment, a transmission electron microscope system includes an electron gun capable of emitting an electron beam toward a sample, a deflector for deflecting the electron beam emitted from the electron gun, an objective lens for forming an image of the electron beam transmitted through the sample, an objective aperture for allowing a portion of the electron beam transmitted through the sample to pass, a detector for detecting a detection signal of the electron beam transmitted through the sample, and a controller for generating an observation image of the sample based on the detection signal from the detector. The deflector adjusts the deflection angle of the electron beam so that the electron beam is irradiated onto the sample while precessing at a predetermined angle with respect to an optical axis, passes zeroth-order and first-order diffracted waves generated by the electron beam passing through the sample through the objective aperture, detects detection signals of the zeroth-order and first-order diffracted waves that have passed through the objective aperture using the detector, and generates a hollow-cone bright-field TEM image from the detection signal.

[0012] In one embodiment, a transmission electron microscope system includes an electron gun capable of emitting an electron beam toward a sample, a deflector for deflecting the electron beam emitted from the electron gun, an objective lens for forming an image of the electron beam transmitted through the sample, a detector for detecting a detection signal of the electron beam transmitted through the sample, and a controller for generating an observation image of the sample based on the detection signal from the detector, wherein the deflector adjusts a deflection angle of the electron beam so that the electron beam is irradiated onto the sample at a predetermined angle with respect to an optical axis, the detector accumulates and detects detection signals of the electron beam transmitted through the sample by irradiating the electron beam multiple times to satisfy the adjusted deflection angle, the detector generates an observation image having multiple contrasts from the accumulated detection signals, and the observation image is used to identify boundaries of the contrasts.

[0013] According to one embodiment, the contrast of the granular structure contained in the amorphous layer can be suppressed, and highly accurate length measurement can be performed based on the observation image thus obtained.

[0014] FIG. 1 is a schematic diagram showing a transmission electron microscope in embodiment 1. FIG. 2 is an explanatory diagram of a hollow-cone illumination method using a transmission electron microscope in embodiment 1. FIG. 3 is an electron diffraction pattern obtained by hollow-cone illumination in embodiment 1. FIG. 4 is a TEM image in a comparative example and its FFT pattern. FIG. 5 is a hollow-cone bright-field TEM image in embodiment 1 and its FFT pattern. FIG. 6 is a line profile obtained from a TEM image in a comparative example. FIG. 7 is a line profile obtained from a hollow-cone bright-field TEM image in embodiment 1. FIG. 8 is a schematic diagram showing a GUI in embodiment 1.

[0015] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0016] (Embodiment 1) <Transmission Electron Microscope System> A transmission electron microscope system 1 according to embodiment 1 will be described below with reference to Fig. 1. The transmission electron microscope system 1 has an observation function that can obtain an observation image of a sample 9 by irradiating the sample 9 with an electron beam, and a length measurement function that can measure the lengths of structures included in the sample 9 based on the obtained observation image.

[0017] In the first embodiment, the transmission electron microscope system 1 is exemplified as being composed of a single device having both an observation function and a length measurement function. However, the transmission electron microscope system 1 may be separated into an observation device having an observation function and a length measurement device having a length measurement function.

[0018] The transmission electron microscope system 1 mainly comprises an electron gun 2, a converging lens 3, an objective lens 4, an intermediate lens 5, a projection lens 6, a deflector 7a, a deflector 7b, a sample holder 8, an objective aperture 10, a detection unit 50, a control unit 60, and a monitor 15.

[0019] A sample 9 is mounted on the sample holder 8. When observing the sample 9, the sample holder 8 with the sample 9 mounted thereon is transported from outside the transmission electron microscope system 1 to inside the transmission electron microscope system 1 so that the sample 9 is positioned inside the objective lens 4.

[0020] The electron gun 2 can emit an electron beam onto a sample 9. The converging lens 3 is provided to converge the electron beam emitted from the electron gun 2. The deflectors 7a and 7b are provided above the sample 9 to deflect the electron beam emitted from the electron gun 2. The objective lens 4 is provided to form an image of the electron beam that has passed through the sample 9. The objective aperture 10 is provided on the back focal plane of the objective lens 4 to allow a portion of the electron beam that has passed through the sample 9 to pass therethrough. The intermediate lens 5 and the projection lens 6 are provided to magnify the image of the electron beam. The detection unit 50 is provided to detect a detection signal of the electron beam that has passed through the sample 9.

[0021] The electron beam emitted from the electron gun 2 is converged by the converging lens 3, deflected by the deflectors 7a and 7b, and irradiated onto the sample 9. The electron beam that has passed through the sample 9 is imaged by the objective lens 4, and any transmitted waves and diffracted waves are captured by the objective aperture 10. The objective aperture 10 is configured so that it can be moved at least in and out of the optical axis. Whether or not the objective aperture 10 is placed on the optical axis is determined by the object or purpose of observation, etc. The transmitted image of the sample 9 that has passed through the objective aperture 10 is enlarged by the intermediate lens 5 and the projection lens 6 and detected by the detection unit 50.

[0022] The detection unit 50 includes a fluorescent screen 11 and a camera 12. The computer 14 can generate an observation image (TEM image) of the sample 9 based on a detection signal from the detection unit 50. For example, a magnified transmission image is projected onto the fluorescent screen 11. When the fluorescent screen 11 is removed from the optical axis, the transmission image is projected onto the camera 12. The transmission image acquired by the camera 12 is stored in the computer 14.

[0023] The control circuit 13 is electrically connected to the electron gun 2, the converging lens 3, the objective lens 4, the intermediate lens 5, the projection lens 6, the deflector 7a, the deflector 7b, the sample holder 8, the objective aperture 10, the fluorescent screen 11, and the camera 12, and controls their operations. The computer 14 is electrically connected to the control circuit 13, and issues instructions to the control circuit 13. The computer 14 can also store various information about operations performed by the transmission electron microscope system 1.

[0024] The control circuit 13 and the computer 14 may be integrated into one control unit, and therefore, in the present application, the control circuit 13 and the computer 14 are referred to as a control unit 60.

[0025] The monitor 15 is electrically connected to the computer 14. When a user inputs an instruction for controlling the transmission electron microscope system 1 on the monitor 15 using an input device or the like, the instruction is transmitted to the computer 14.

[0026] The configuration of the transmission electron microscope system 1 is not limited to the configuration shown in FIG. 1, and may include other lenses, detectors, etc.

[0027] <Observation Function of Transmission Electron Microscope System> The hollow cone irradiation method using the transmission electron microscope system 1 will be described below with reference to FIG.

[0028] The deflection angle of the electron beam 16 is adjusted by the deflectors 7 a and 7 b so that the electron beam 16 converged by the convergent lens 3 is irradiated onto the sample 9 while precessing at a predetermined angle with respect to the optical axis 70 .

[0029] The electron beam 16 is tilted at a predetermined angle by the first-stage deflector 7a, and deflected back by the second-stage deflector 7b so as to irradiate the same location on the sample 9. The electron beam 16 is also irradiated onto the sample 9 while being rotated about the optical axis 70. By appropriately selecting the precession conditions, the electron beam 16 is irradiated along a hollow cone whose apex is the surface on which the sample 9 is located. In the first embodiment, this type of irradiation is referred to as hollow cone irradiation.

[0030] As shown in the electron diffraction pattern 17 at the focal plane, a transmitted wave (zeroth-order diffracted wave) 19 and a first-order diffracted wave 20 are generated as the electron beam 16 passes through the sample 9. The transmitted wave 19 rotates circularly around the optical axis 70. The first-order diffracted wave 20 rotates circularly around a position slightly away from the optical axis 70.

[0031] The objective aperture 10 is provided with an objective aperture hole 18. The deflection angle of the electron beam 16 is adjusted by the deflectors 7a and 7b so that the transmitted wave 19 and the first-order diffracted wave 20 pass through the objective aperture hole 18. Detection signals of the transmitted wave 19 and the first-order diffracted wave 20 that have passed through the objective aperture 10 are detected by the detection unit 50. The control unit 60 (computer 14) generates a hollow-cone bright-field TEM image as an observation image from the detected detection signals.

[0032] 3 shows an electron diffraction pattern 17 obtained by hollow-cone irradiation. The sample 9 has a plurality of stacked films. Here, the plurality of films includes a silicon film (single crystal of Si

[110] ) and an ONO film (silicon oxide film / silicon nitride film / silicon oxide film).

[0033] An electron beam 16 is irradiated onto a Si

[110] single crystal under hollow-cone illumination conditions. The deflection angle of the electron beam 16 is adjusted so that a transmitted wave 19 and a first-order diffracted wave 20 pass through an objective aperture hole 18. Within the objective aperture 10, the transmitted wave 19 and the first-order diffracted wave 20 rotate circularly. By imaging the transmitted electrons under these conditions, a hollow-cone bright-field TEM image can be obtained.

[0034] As described above, under hollow cone illumination conditions, the electron beam 16 is irradiated onto the sample 9 while being rotated about the optical axis 70. Therefore, strictly speaking, an electron diffraction pattern at a given instant is represented as a single electron diffraction spot. The circular electron diffraction pattern 17 in the first embodiment can also be said to be a collection of multiple electron diffraction spots.

[0035] Therefore, the process of irradiating the sample 9 with the electron beam 16 while causing it to precess and generating a hollow-cone bright-field TEM image can also be expressed as follows.

[0036] The deflection angle of the electron beam 16 is adjusted by the deflectors 7a and 7b so that the electron beam 16 is irradiated onto the sample 9 at a predetermined angle with respect to the optical axis 70. The electron beam 16 is irradiated multiple times to satisfy the adjusted deflection angle, and the detection signals of the electron beam 16 that have passed through the sample 9 are integrated and detected by the detection unit 50. From the integrated detection signals, an observation image with multiple contrasts is generated.

[0037] 4 and 5 show an observed image of the ONO film and an FFT pattern (crystal lattice image) obtained by fast Fourier transform of the observed image. Fig. 4 is a comparative example for comparison with the first embodiment shown in Fig. 5.

[0038] Fig. 4 shows a normal TEM image 21 of the ONO film, an enlarged image 22 of a portion of the TEM image 21, and an FFT pattern 23. Fig. 5 shows a hollow-cone bright-field TEM image 24 of the ONO film taken under the conditions shown in Figs. 2 and 3, an enlarged image 25 of a portion of the hollow-cone bright-field TEM image 24, and an FFT pattern 26.

[0039] In FIG. 4, as shown in the TEM image 21 and the enlarged image 22, the granular structure contained in the amorphous layer is observed as granular contrast.

[0040] 5, the granular structure contained in the amorphous layer is averaged, and almost no granular contrast is observed, as shown in the hollow-cone bright-field TEM image 24 and the enlarged image 25. Furthermore, the overall detection signal intensity of the hollow-cone bright-field TEM image 24 is almost equal to that of the TEM image 21.

[0041] Furthermore, as can be seen from the FFT pattern 26, by passing the transmitted wave 19 and the first-order diffracted wave 20 through the objective aperture hole 18, the crystal lattice of the silicon substrate can also be simultaneously observed in the hollow-cone bright-field image TEM 24.

[0042] As will be described later, the thickness of each ONO film is measured based on the hollow-cone bright-field image TEM 24, but the value of the crystal lattice spacing is a known constant. Therefore, by using the value of the crystal lattice spacing, the results of the measurement can be corrected to more accurate values. In other words, by correcting the results of the measurement using the crystal lattice spacing of the FFT pattern 26, more accurate measurements can be performed.

[0043] Fig. 6 is a line profile 27 obtained from the TEM image 21 in Fig. 4. Fig. 7 is a line profile 28 obtained from the hollow-cone bright-field TEM image 24 in Fig. 5. In these line profiles 27 and 28, the vertical axis indicates the intensity of the detection signal detected by the detection unit 50 (integrated intensity of the detection signal), and the horizontal axis indicates the thickness of the sample 9.

[0044] As shown in Figure 6, the line profile 27 exhibits large variations and a wide distribution width due to the influence of the granular structure contained in the amorphous layer. For example, the standard deviation σ of the line profile 27 is 154. Therefore, it is difficult to identify the boundaries of the ONO film from the TEM image 21. It is also difficult to identify the boundaries of contrast (edge ​​detection) using the TEM image 21.

[0045] On the other hand, as shown in FIG. 7 , the influence of the granular structure is suppressed in the line profile 28, resulting in small variations and a narrow distribution width. For example, the standard deviation σ of the line profile 28 is 31. Therefore, it is easy to identify the boundaries of the ONO film from the hollow-cone bright-field image TEM 24. Furthermore, it is easy to identify the boundaries of contrast (edge ​​detection) using the hollow-cone bright-field image TEM 24.

[0046] <Measurement Function of Transmission Electron Microscope System> The thickness of each of the silicon oxide (SiO) film, silicon nitride (SiN) film, and silicon oxide (SiO) film is measured using the line profile 28. In other words, the line profile 28 is used to identify two or more contrast boundaries in the hollow-cone bright-field image TEM 24, and the distance between the identified two or more boundaries is measured.

[0047] In this case, a part of the line profile 28 may be configured as a curve, such as between an SiN film and an SiO film. In this case, the thickness of each of the SiN film and the SiO film can be roughly measured, but in order to measure the thickness more accurately, the curve is differentiated.

[0048] By differentiating the curve, the boundary between adjacent films can be calculated. That is, the boundary between two or more contrasts can be identified (edge ​​detection), and a peak search for the inflection point of the curve can be performed. The boundary calculation result obtained by such differentiation is used to correct the measurement result. By calculating the position of each boundary of the ONO film with high accuracy, the thickness of each ONO film can be measured with high accuracy. In other words, by calculating the position of the boundary between two or more contrasts with high accuracy, the distance between the boundaries of two or more contrasts can be measured with high accuracy.

[0049] 5, the results of the length measurement can be corrected to more accurate values ​​by acquiring the FFT pattern 26 as a crystal lattice image and using the value of the crystal lattice spacing. That is, by correcting the results of the length measurement using the crystal lattice spacing of the FFT pattern 26, it is possible to perform length measurement with higher accuracy.

[0050] In the first embodiment, to obtain the hollow-cone bright-field image TEM 24, the electron beam 16 is irradiated onto the sample 9 while precessing, and the deflection angle of the electron beam 16 is adjusted so that the transmitted wave 19 and the first-order diffracted wave 20 pass through the objective aperture hole 18. However, even if the electron beam 16 is irradiated onto the sample 9 while precessing, and only the transmitted wave 19 passes through the objective aperture hole 18, the hollow-cone bright-field image TEM 24 can be obtained. However, in this case, the FFT pattern 26 cannot be acquired as a crystal lattice image, and the measurement results cannot be corrected using the crystal lattice spacing. Therefore, to perform measurements with higher accuracy, it is preferable that both the transmitted wave 19 and the first-order diffracted wave 20 pass through the objective aperture hole 18.

[0051] <GUI of Transmission Electron Microscope System> The transmission electron microscope system 1 includes a graphical user interface (GUI) 29 that is displayed on the monitor 15. As shown in Fig. 8 , the GUI 29 includes an electron diffraction pattern display section 30, setting buttons 31a and 31b, an observation image display section 32, a line profile display section 33, and a length measurement result display section 34. Note that each display section and each button does not have to be displayed in a single window, and may be displayed in separate windows as appropriate.

[0052] The electron diffraction pattern display unit 30 is provided to allow the user to set the electron diffraction pattern. Setting buttons 31a and 31b are provided to allow the user to set the use of the length measurement mode. The observation image display unit 32 is provided to display the generated observation image (hollow-cone bright-field TEM image 24). The line profile display unit 33 is provided to display the line profile 28. The measurement result display unit 34 is provided to display the results of length measurement of each thickness (the distance between two or more contrast boundaries) of multiple films, such as ONO films.

[0053] The electron diffraction pattern display section 30 displays a virtual objective aperture hole 18a, a virtual transmitted wave 19a, and a virtual first-order diffracted wave 20a which simulate the objective aperture hole 18, the transmitted wave 19, and the first-order diffracted wave 20. By operating a cursor 35 in the electron diffraction pattern display section 30, the user can set the radii of the virtual objective aperture hole 18a and the virtual transmitted wave 19a.

[0054] In response to changes in the radii of the virtual objective aperture hole 18a and the virtual transmitted wave 19a, the radii of the actual objective aperture hole 18, the transmitted wave 19, and the first-order diffracted wave 20 are also changed, and the actual deflection angle of the electron beam 16 by the deflectors 7a, 7b is also changed. Based on such settings of the electron diffraction pattern, the deflection angle of the electron beam 16 can be adjusted, for example, so that the transmitted wave 19 and the first-order diffracted wave 20 pass through the objective aperture hole 18.

[0055] When the user selects the setting button 31 a (ON), the use of the length measurement mode is set, and when the user selects the setting button 31 b (OFF), the use of the length measurement mode is canceled. When the use of the length measurement mode is set (ON), the irradiation of the electron beam 16 becomes a hollow cone irradiation with a deflection angle adjusted in the electron diffraction pattern display unit 30, and the length of the sample 9 can be measured automatically.

[0056] That is, when the measurement mode is set to be used, the following operations can be performed automatically: irradiating the sample 9 with the electron beam 16, generating an observation image (hollow-cone bright-field TEM image 24), acquiring a line profile 28, and measuring the thickness of each of a plurality of films (the distance between the boundaries of two or more contrasts). In this case, the generated hollow-cone bright-field TEM image 24 is displayed in the observation image display unit 32, the line profile 28 is displayed in the line profile display unit 33, and the measurement result display unit 34 displays the measurement results as numerical values.

[0057] The line profile display section 33 displays a dashed line indicating the location of the line profile within the sample 9. The user can set the start point and end point of the dashed line by operating a cursor 36 within the line profile display section 33. Furthermore, the measurement result in the measurement result display section 34 is also changed in response to the change in the dashed line.

[0058] It is also possible to automatically differentiate a part of the curve of the line profile 28. In this case, the measurement result display unit 34 displays the result of the measurement corrected using the calculation result obtained by differentiation.

[0059] The GUI 29 may also have a display unit for displaying the FFT pattern 26. The FFT pattern 26 can also be automatically acquired from the hollow-cone bright-field TEM image 24. In this case, the measurement result display unit 34 displays the measurement result corrected using the crystal lattice spacing of the FFT pattern 26.

[0060] The present invention has been specifically described above based on the form for implementing the present invention, but the present invention is not limited to the above-described embodiment and can be modified in various ways without departing from the spirit of the present invention.

[0061] 1 Transmission electron microscope system 2 Electron gun 3 Converging lens 4 Objective lens 5 Intermediate lens 6 Projection lens 7a, 7b Deflector 8 Sample holder 9 Sample 10 Objective aperture 11 Fluorescent screen 12 Camera 13 Control circuit 14 Computer 15 Monitor 16 Electron beam 17 Electron diffraction pattern 18 Objective aperture hole 18a Virtual objective aperture hole 19 Transmitted wave (0th order diffracted wave) 19a Virtual transmitted wave (virtual 0th order diffracted wave) 20 1st order diffracted wave 20a Virtual 1st order diffracted wave 21 TEM image 22 Enlarged image of TEM image 23 FFT pattern of TEM image (crystal lattice image) 24 Hollow-cone bright-field TEM image 25 Enlarged image of hollow-cone bright-field TEM image 26 FFT pattern of hollow-cone bright-field TEM image (crystal lattice image) 27 Line profile of TEM image 28 Line profile of hollow-cone bright-field TEM image 29 Graphical user interface (GUI) 30 Electron diffraction pattern display section 31a, 31b Setting buttons 32 Observation image display section 33 Line profile display section 34 Measurement result display section 35, 36 Cursor 50 Detector section 60 Control section 70 Optical axis

Claims

1. A transmission electron microscope system comprising: an electron gun capable of emitting an electron beam toward a sample; a deflector for deflecting the electron beam emitted from said electron gun; an objective lens for forming an image of the electron beam that has passed through said sample; an objective aperture for allowing a portion of the electron beam that has passed through said sample to pass; a detection unit for detecting a detection signal of the electron beam that has passed through said sample; and a control unit for generating an observation image of the sample based on the detection signal from the detection unit, wherein: said deflector adjusts the deflection angle of the electron beam so that the electron beam is irradiated onto the sample while precessing at a predetermined angle with respect to the optical axis; zeroth-order diffracted waves and first-order diffracted waves generated by the electron beam passing through the sample are passed through said objective aperture; detection signals of the zeroth-order diffracted waves and first-order diffracted waves that have passed through the objective aperture are detected by the detection unit; and a hollow-cone bright-field TEM image is generated from the detection signal.

2. A transmission electron microscope system according to claim 1, wherein a line profile showing the relationship between the intensity of the detection signal and the thickness of the sample is obtained from the hollow-cone bright-field TEM image, the sample having a plurality of stacked films, and the line profile is used to measure the thickness of each of the plurality of films.

3. A transmission electron microscope system according to claim 2, wherein the boundary between adjacent films is calculated by differentiating a curve that constitutes part of the line profile, and the result of the boundary calculation is used to correct the result of the length measurement.

4. A transmission electron microscope system according to claim 2, wherein a crystal lattice image of the sample is obtained from the hollow-cone bright-field TEM image, and the results of the length measurement are corrected using the crystal lattice spacing of the crystal lattice image.

5. A transmission electron microscope system according to claim 2, further comprising: a monitor electrically connected to the control unit; and a graphical user interface displayed on the monitor, wherein the graphical user interface has: an electron diffraction pattern display section for a user to set an electron diffraction pattern; a setting button for the user to set use of a length measurement mode; an observation image display section for displaying the generated hollow-cone bright-field TEM image; a line profile display section for displaying the line profile; and a measurement result display section for displaying the results of the length measurement of the thickness of each of the plurality of films, wherein the deflection angle of the electron beam is adjusted based on the setting of the electron diffraction pattern, and when use of the length measurement mode is set, the transmission electron microscope system can automatically irradiate the sample with the electron beam, generate the hollow-cone bright-field TEM image, obtain the line profile, and measure the thickness of each of the plurality of films.

6. A transmission electron microscope system comprising: an electron gun capable of emitting an electron beam toward a sample; a deflector for deflecting the electron beam emitted from said electron gun; an objective lens for forming an image of the electron beam that has passed through said sample; a detection unit for detecting a detection signal of the electron beam that has passed through said sample; and a control unit for generating an observation image of said sample based on said detection signal from said detection unit, wherein said deflector adjusts the deflection angle of the electron beam so that the electron beam is irradiated onto the sample at a predetermined angle with respect to an optical axis; said detection unit accumulates and detects detection signals of the electron beam that has passed through the sample by irradiating the electron beam multiple times that satisfy the adjusted deflection angle; 7. A transmission electron microscope system according to claim 6, wherein the electron beam irradiated onto the sample precesses at the predetermined angle relative to the optical axis.

8. A transmission electron microscope system according to claim 6, wherein a line profile indicating the relationship between the integrated intensity of the detection signal and the thickness of the sample is obtained from the observed image, and the boundary is identified using the line profile.

9. A transmission electron microscope system according to claim 8, wherein two or more of the boundaries are identified, and the distance between the two or more identified boundaries is measured.

10. A transmission electron microscope system according to claim 9, wherein the boundary is calculated by differentiating a curve that constitutes part of the line profile, and the result of the boundary calculation is used to correct the result of the length measurement.

11. A transmission electron microscope system according to claim 9, wherein a crystal lattice image of the sample is obtained from the observation image, and the results of the length measurement are corrected using the crystal lattice spacing of the crystal lattice image.

12. A transmission electron microscope system according to claim 9, further comprising: a monitor electrically connected to the control unit; and a graphical user interface displayed on the monitor, wherein the graphical user interface has: an electron diffraction pattern display section for a user to set an electron diffraction pattern; a setting button for the user to set use of a length measurement mode; an observation image display section for displaying the generated observation image; a line profile display section for displaying the line profile; and a measurement result display section for displaying the results of the measurement of the distance between the two or more boundaries, wherein the deflection angle of the electron beam is adjusted based on the setting of the electron diffraction pattern, and when use of the length measurement mode is set, the transmission electron microscope system can automatically irradiate the sample with the electron beam, generate the observation image, obtain the line profile, and measure the distance between the two or more boundaries.

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