JPH05135728A - Transmission type electron microscope - Google Patents

Abstract

PURPOSE:To improve the switching operability between the image observation mode and the diffraction image observation mode in a transmission type electron microscope. CONSTITUTION:When the image observation mode is instructed, an electron beam is focused to satisfy the focus state set by an operator, an objective aperture 11 is inserted on the optical axis, no exciting current is fed to a mini-lens ML, and a visual field limiting aperture 12 is removed from the optical axis. An electron microscope image is formed at the position of the visual field limiting aperture 12, and this image is projected on a screen 13. When the diffraction image observation mode is instructed, the electron beam is radiated at the preset radiation angle. The objective aperture 11 is removed from the optical axis, the preset exciting current is fed to the mini-lens ML, and the visual field limiting aperture 12 is inserted on the optical axis. A diffraction image is formed at the position of the visual field limiting aperture 12, and the diffraction image is projected on the screen 13.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a transmission electron microscope (T
EM), especially a mode for observing an electron microscope image,
The present invention relates to a configuration of an imaging system lens for switching a mode for observing a diffraction image.

[0002]

2. Description of the Related Art In a TEM, a mode for observing an electron microscope image which is a magnified image of a sample (hereinafter referred to as an image observation mode) and an electron beam diffraction imaged on a back focal plane of an objective lens (OL). A mode in which an image (hereinafter simply referred to as a diffraction image) is projected on a screen by an imaging lens and observed (hereinafter,
This mode is called a diffraction image observation mode), and the latter is called the selected area diffraction method. FIG. 2 shows the outline of the operation of the imaging system lens in the image observation mode and the diffraction image observation mode. In the figure, 1 is a sample, 2 is an objective diaphragm, 3 is a field limiting diaphragm, 4 is a screen, OL is an objective lens, I
L ₁ is the first intermediate lens, IL ₂ is the second intermediate lens, PL
Indicates a projection lens.

FIG. 2A is a diagram showing the operation of the imaging system lens in the image observation mode. At this time, the objective diaphragm 2 is inserted to improve the contrast of the electron microscope image, and the field limiting diaphragm 3 is removed. .. The electron beam is converged so that the desired brightness can be obtained.

When the sample 1 is irradiated with an electron beam, a diffraction image is formed at the position of the objective diaphragm 2, that is, the back focal plane of the OL, and an electron microscope image is formed at the position of the field limiting diaphragm 3. Is imaged. Then, the first intermediate lens IL ₁ forms an electron microscope image at a predetermined position with the electron microscope image formed at the position of the field limiting diaphragm 3 as the object plane, and hereinafter, the electron microscope image is the second intermediate image. The image is enlarged on the screen 4 by the lens IL ₂ and the projection lens RL.

FIG. 2B is a diagram showing the operation of the image forming system lens in the diffraction image observation mode, in which the objective diaphragm 2 is removed and the field limiting diaphragm 3 is inserted. Further, the electron beam has a large irradiation angle in order to prevent the screen 4 from being burned by the spot at the center of the diffraction image. Then, the first intermediate lens IL ₁ forms a diffracted image at a predetermined position with the diffracted image formed at the position of the objective diaphragm 2 as the object plane, and hereinafter, the diffracted image is the second intermediate lens I 1.
L _{2 is} enlarged by the projection lens RL and is focused on the screen 4.

[0006]

By the way, when observing a sample having crystallinity such as metal, it is necessary to frequently switch between the image observation mode and the diffraction image observation mode. In order to take a pair of photographs of a diffraction image in the same field of view as the electron microscope image, it is usual to switch the mode about 20 to 30 times. Then, as is clear from the above description, it is necessary to insert or remove the objective diaphragm, insert or remove the field limiting diaphragm, and switch the electron beam convergence state every time the mode is switched. The operation was troublesome.

The present invention is intended to solve the above problems, and an object thereof is to provide a transmission electron microscope capable of easily switching between an image observation mode and a diffraction image observation mode. is there.

[0008]

In order to achieve the above object, the transmission electron microscope of the present invention includes an objective diaphragm, a field limiting diaphragm, and an intermediate position between the objective diaphragm and the field limiting diaphragm. A first lens that sometimes forms a diffraction image at the position of the objective diaphragm at the position of the field limiting diaphragm;
At least a second lens that always has an image at the position of the field limiting diaphragm as an object plane is provided.

[0009]

The first lens is arranged in the middle of the objective diaphragm and the field limiting diaphragm, and the second lens is arranged in the subsequent stage. Then, the first lens forms a diffraction image formed at the position of the objective diaphragm at the position of the field limiting diaphragm during operation. The second lens always forms an image at the position of the field limiting diaphragm at a predetermined position as an object plane. Therefore, when the first lens is not operated, the electron microscope image formed at the position of the field limiting diaphragm is projected on the screen by the second lens and the lens at the subsequent stage. On the other hand, when the first lens is operated, a diffraction image is formed at the position of the field limiting diaphragm by the action of the first lens, so that the diffraction image is generated by the second lens and the lens at the subsequent stage. Projected on the screen by.

[0010]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an embodiment of a transmission electron microscope according to the present invention. In the figure, ML is a mini lens, IL ₁ is a first intermediate lens, 10 is an electron gun, 11 is an objective aperture, and 12 Is a field limiting diaphragm, 13 is a screen, 14 is a control device, 1
Reference numeral 5 is a mode setting unit, 16 is an electron gun drive unit, 17 is an objective aperture drive unit, 18 is an ML drive unit, 19 is a field limiting aperture drive unit, 20 is a deflection coil, and 21 is a deflection coil drive unit. Note that, in FIG. 1, the irradiation system lens, the second intermediate lens, the projection lens, and the like arranged in the subsequent stage of the first intermediate lens IL ₁ are omitted because they are not related to the essence of the present invention.

In FIG. 1, the mini-lens ML forms a diffracted image at the position of the field limiting diaphragm 12 with the diffracted image formed at the position of the objective diaphragm 11 as an object surface during operation. It is desirable to use a coil having very small hysteresis such as. In addition, the first intermediate lens I
L ₁ always forms an image at a predetermined position with the image formed at the position of the field limiting diaphragm 12 as the object plane. This first
The image formed by the intermediate lens IL ₁ is enlarged and formed on the screen 13 by a second intermediate lens, a projection lens and the like (not shown). The deflection coil 20 is arranged as blanking means for preventing the electron beam from irradiating the screen 13.

The mode setting section 15 switches between the image observation mode and the diffraction image observation mode, and is composed of appropriate switches such as button switches. The control device 14 is composed of a microprocessor and its peripheral circuits.

When the image setting mode is instructed by the mode setting unit 15, the control unit 14 instructs the electron gun driving unit 16 to converge the electron beam, and the objective aperture driving unit 17. On the other hand, the objective stop 11 is instructed to be inserted on the optical axis, the ML drive section 18 is instructed not to operate, and the field limiting stop drive section 19 is set on the optical axis of the field limiting stop 12. Instruct to remove from. As a result, the electron beam emitted from the electron gun 10 is converged so as to satisfy a predetermined state, for example, a converged state set by the operator, the objective aperture 11 is inserted on the optical axis, and the exciting current is applied to the mini lens ML. Is not supplied, field limiting diaphragm 1
2 is removed from the optical axis. Therefore, at this time, since the electron microscope image is formed at the position of the field limiting diaphragm 12, the electron microscope image is projected on the screen 13.

On the other hand, when the mode setting section 15 instructs the diffraction image observation mode, the control device 14
Instructs the electron gun drive unit 16 to increase the convergence angle of the electron beam, instructs the objective aperture drive unit 17 to remove the objective aperture 11 from the optical axis, and instructs the ML drive unit. 18 is instructed to operate, and the field limiting diaphragm driving unit 19 is instructed to insert the field limiting diaphragm 12 on the optical axis. As a result, the electron beam emitted from the electron gun 10 is made to have a predetermined state, for example, a predetermined irradiation angle, the objective diaphragm 11 is removed from the optical axis, and a predetermined exciting current is applied to the mini lens ML. After being supplied, the field limiting diaphragm 12 is inserted on the optical axis. Therefore, at this time, since the diffraction image is formed at the position of the field limiting diaphragm 12, the diffraction image is projected on the screen 13.

Further, when the image observation mode is switched to the diffraction image observation mode, the control device 14 starts the electron gun 10, the objective diaphragm 11, the mini lens ML and the field of view from the time when the mode switching is instructed. The deflection coil driving unit 21 is instructed to perform blanking until the state of the limiting diaphragm 12 is set for the diffraction image observation mode. As a result, a predetermined exciting current is supplied to the deflection coil 20, so that the electron beam is deflected and does not reach the screen 13, so that it is possible to prevent flicker of the image on the screen 13 during mode switching. The same applies when switching from the diffraction image observation mode to the image observation mode.

According to the above construction, the image setting mode and the diffraction image viewing mode can be easily switched by simply instructing the mode setting section 15 to switch the mode. Further, if the mini-lens ML is composed of an air-core coil, the air-core coil has a very small inductance, so that mode switching can be performed at high speed.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, in the above-described embodiment, the mode switching is performed manually, but the control device 14 may automatically perform the mode switching at a desired cycle. Further, although the deflection coil is used as the means for blanking in the above embodiment, a member for blocking the electron beam may be inserted on the optical axis. It can be arranged at any position.

[0018]

As is apparent from the above description, according to the present invention, the state for achieving the instructed mode is automatically set only by instructing the image observation mode and the diffraction image observation mode. Therefore, the operability can be significantly improved as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing an outline of the operation of the imaging system lens in the image observation mode and the diffraction image observation mode.

[Explanation of symbols]

ML ... Mini lens, IL ₁ ... First intermediate lens, 10 ... Electron gun, 11 ... Objective diaphragm, 12 ... Field limiting diaphragm, 13 ... Screen, 14 ... Control device, 15 ... Mode setting unit, 16
... Electron gun drive unit, 17 ... Objective aperture drive unit, 18 ... ML drive unit, 19 ... Field limiting aperture drive unit, 20 ... Deflection coil,
21 ... Deflection coil drive unit.

Claims (3)

[Claims] 1. An objective diaphragm, a field limiting diaphragm, and an intermediate position between the objective diaphragm and the field limiting diaphragm, which forms a diffraction image formed at the position of the objective diaphragm during operation at the position of the field limiting diaphragm. A transmission electron microscope comprising at least a first lens for imaging and a second lens having an image of the position of the field limiting diaphragm as an object surface at all times. 2. The transmission type according to claim 1, further comprising control means for automatically inserting and removing the objective diaphragm and the field limiting diaphragm according to the operation / non-operation of the first lens. electronic microscope. 3. The transmission electron according to claim 1, further comprising a blanking means for preventing an electron beam from irradiating the screen or the film when the first lens is operated / not operated. microscope.