JPH01267945A - Focusing system of electron microscope - Google Patents

Abstract

PURPOSE:To select the diffraction image reasonably in terms of mechanism of a permeative electron microscope by obtaining a diffraction image on a restricted view field stop with an objective mini-lens, and by using this restricted view field stop also as an objective stop. CONSTITUTION:A focusing system according to existing invention is equipped with an objective mini-lens (MO) 10, which focuses a diffraction image at the rear focal surface of an objective lens (OL) 2 on a restricted view field stop, and deflection coils 11, 12 to deflect image on this restricted view field stop. That is, no objective stop is provided, and the diffraction image formed on the rear focal surface 3 of the OL 2 is focused on the restricted view field stop 4 by the OM 10 directly as it is. At this time, the image by OL 2 is formed in the position 13, i.e. between the OM 10 and the restricted view field stop 4. The diffraction image formed on the restricted view field stop 4 is deflected by No.1 and No.2 deflection coils 11, 12, and thereby only desired diffraction image is taken out from the aperture of the restricted view field stop 4. This allows obtainment of a desired diffraction image easily and reasonably in from the structural point of view.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electron microscope, and in particular to an imaging system for obtaining a desired diffraction pattern [Prior Art] Transmission electron microscope (hereinafter referred to as , TEM) allows not only electron microscopic images but also diffraction images to be obtained, so it is widely practiced to observe diffraction images in order to identify crystal structures and the like. There are various methods for obtaining dark-field images (diffraction images), such as image processing methods and scanning transmission methods using scanning electron microscopy techniques, but in TEM, the method using objective aperture is generally used. It is true. The second example is
As shown in the figure.

In Figure 2, 1 is a sample, 2 is an objective lens (hereinafter, the objective lens is referred to as OL), 3 is a back focal plane, 4 is a selected area diaphragm, 5 is an intermediate lens, 6 is a projection lens, and 7 is a fluorescent screen. , 8 is an objective aperture. In addition, in the figure, only the position of the center of each lens is shown. The same applies hereafter.

In FIG. 2, when the beam is applied to the sample 1, a diffraction image of the sample 1 is formed on the back focal plane 3, and the image is formed at the position of the selected area diaphragm 4.

That is, the diffraction image plane is located at the back focal plane 3, and the image plane is located at the selected area diaphragm 4. In this state, adjust the opening of the objective diaphragm 8 placed at the back focal plane 3 of the OL2, move it in the direction shown by the arrow 9 to select a desired diffraction image, and then focus the intermediate lens 5. By adjusting the distance, the front focal plane of the intermediate lens 5 is made to coincide with the rear focal plane 3 of the OL 2, and this plane is imaged onto the fluorescent screen 7 as a final image by the projection lens 6, thereby forming a desired diffraction image of the sample. can be observed. Note that, at this time, the intermediate lens 5 has an extremely low magnification, that is, a very small magnification.

Alternatively, the beam selected by the objective aperture 8 can be introduced into an energy analyzer to perform energy analysis.

When observing an electron microscope image of the sample 1 with the configuration shown in FIG. 2, the image on the selected area diaphragm 4 may be enlarged by the intermediate lens 5 and the projection lens 6 and projected onto the fluorescent screen 7.

[Problems to be Solved by the Invention] However, the conventional method has the following problems.

One is that the objective diaphragm 8 is arranged at the position of the back focal plane 3 of the OL 2. Certainly, it is theoretically correct to arrange the objective diaphragm 8 at the position of the back focal plane 3 of the OL2, and it also appears possible to arrange it with considerable margin in the drawings. but,
In reality, there are restrictions such as the shape of the sample holder and the gap length of the pole pieces, so it is not always possible to correctly position the objective diaphragm 8 at the back focal plane 3. If the objective diaphragm 8 is not placed in the correct position, undesired beams will pass through, and conversely, the area around the objective lens should be designed so that the objective diaphragm 8 can be placed in the correct position. If you try to do this, the gap length between pole pieces, hole diameter, etc. will be restricted, making it extremely difficult to design high-resolution pole pieces. Thus, in any case, it is difficult to arrange the objective diaphragm 8 at the position of the back focal plane 3 of the OL2.

Next, conventionally, the selection of a diffraction image was carried out by manually moving the objective aperture 8, which took time and required skill to obtain a desired diffraction image.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an imaging system for an electron microscope that can easily obtain a desired diffraction image even though the structure is unreasonable. be.

[Means for Solving the Problems] In order to achieve the above object, the imaging system of the electron microscope of the present invention has an objective miniaturization system that images a diffraction image formed at the back focal plane of the objective lens on a selected area aperture. It is characterized by comprising at least a lens and a deflection coil that deflects the image on the selected area diaphragm.

[Function] According to the present invention, a diffraction image is obtained on the selected area diaphragm using the objective mini-lens, and the selected area diaphragm is also used as a conventional objective diaphragm, so diffraction can be easily achieved due to the mechanism of the transmission electron microscope. A selection of statues can be made. Also,
Since the diffraction image is deflected by the deflection coil and only the desired diffraction image is taken out from the selected area diaphragm, the selection of the diffraction image can be easily performed.

[Example code] Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of an imaging system of an electron microscope according to the present invention, and in the figure, reference numeral 10 denotes an objective mini-lens (hereinafter, the objective mini-lens is referred to as OM).

), IL 12 are the first and second deflection coils, respectively.
13 indicates an image plane. Components that are the same as those in FIG. 2 are given the same numbers and their explanations will be omitted.

Further, although not shown in FIG. 1, an intermediate lens and the like are arranged below the selected area diaphragm 4 as in FIG. 2.

In FIG. 1, unlike in FIG. 2, no objective diaphragm is arranged, and the diffraction image formed on the back focal plane 3 of the OL2 is directly focused on the selected area diaphragm 4 at 0 Ml0. . At this time, the image by OL2 is formed at position 13 in the figure, that is, between 0M10 and selected area aperture 4. Then, the diffraction image formed on the selected area aperture 4 is
The second deflection coils 11 and 12 deflect the light as indicated by solid lines or broken lines in the figure, so that only a desired diffraction image is extracted from the aperture of the selected area diaphragm 4. Since the selected area diaphragm 4 is usually located at a location with sufficient space, it is not subject to various restrictions unlike the objective diaphragm.

As is clear from the above description, the position where O'M10 is placed is closer to the sample 1 than the image plane 13 formed by OL2, and its excitation is strong enough to form a real image.

The above is a case of observing a diffraction image, but when observing an electron microscope image, the excitation of the intermediate lens (not shown) in the state shown in Fig. 1 should be made weaker than the normal excitation conditions, or the 0M10 As a non-operating device, an image plane may be formed on the selected area diaphragm 4 as in FIG. 2, and the image may be magnified by an intermediate lens and a projection lens. In the former case, the object surface will be farther away than usual for the intermediate lens, so the maximum magnification will decrease, but an effective countermeasure to this is to place the selected area diaphragm 4 in the gap between the intermediate lenses. It is.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, although two deflection coils are used in FIG. 1, it is obvious that one deflection coil may also be used.

[Effects of the Invention] As is clear from the above description, according to the present invention, a selected area diaphragm is used to select a desired diffraction image, so the diaphragm can be placed at the correct position. It is something. Furthermore, by deflecting the diffraction image with a deflection coil, a desired diffraction image can be selected without moving the selected area diaphragm, so it is also possible to automatically select a large number of diffraction images using a program.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of an imaging system for an electron microscope according to the present invention, and FIG. 2 is a diagram showing an imaging system for a conventional electron microscope. DESCRIPTION OF SYMBOLS 1... Sample, 2... Objective lens, 3... Back focal plane, 4... Selected area aperture, 5... Intermediate lens, 6...
・Projection lens, 7... Fluorescent screen, 8... Objective diaphragm, 1
0... Objective mini lens, 11.12... Deflection coil, 13... Image plane. Applicant JEOL Ltd. Agent Patent Attorney Hideo Sugai (4 others) District 1

Claims (3)

[Claims] (1) An electron microscope characterized by comprising at least an objective mini-lens that forms a diffraction image formed on the back focal plane of the objective onto a selected area diaphragm, and a deflection coil that deflects the image on the selected area diaphragm. Imaging system. (2) The imaging system for an electron microscope according to claim 1, wherein the objective mini-lens is arranged closer to the sample than the image plane formed by the objective lens. (3) The imaging system for an electron microscope according to claim 1 or 2, wherein the selected area diaphragm is provided in a gap of an intermediate lens located immediately behind the objective lens.