JPS6014463B2 - electronic microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that can independently control the rotation of an electron beam image in a transmission imaging electron microscope, regardless of the image magnification.

Transmission imaging electron microscopes use multiple electromagnetic lenses as their imaging lens system, but the symmetrical magnetic field of the electromagnetic lenses causes a rotational effect on the electron beam, and as the image magnification is changed, The field of view of the electron beam image formed on the optical slope rotates. Both FIG. 1 and FIG. 2 are schematic diagrams showing the configuration of an imaging lens system in a normal electron microscope, in which a thin film sample 2, an objective lens 3, an intermediate lens 4, a projection lens 5 and a saddle light plate 6 are sequentially arranged. Figure 1 shows the electron beam path for obtaining a high-magnification image. 4, the image is enlarged to the position 8, and the image is further projected onto the light-emitting plate 6 by the projection lens 5. Figure 2 shows the electron beam path for obtaining an intermediate magnification image.The excitation of the objective lens 3 is weak, and the electron beam that passes through the sample 2 forms an electron beam image for the first time at a position 8 behind the intermediate lens 4. The image is projected onto the image light plate 6 by the projection lens 5. In these figures, each electron beam image is drawn as if it were all on the same plane (paper surface), but each number in the solid line is an angle corresponding to the excitation intensity of the electromagnetic lens in a plane perpendicular to optical axis 1. Because of the rotation, the electron beam image displayed on the crab light slope will be displayed in different directions if the image magnification is different. Therefore, when a large number of electron beam images with different magnifications are photographed for the same area of a sample and comparatively observed, the direction of the field of view becomes inconsistent, which causes inconvenience. The purpose of the present invention is to solve such problems by providing an electromagnetic lens at or near the position of the electron beam image formed within the imaging lens system, and using the electromagnetic lens for controlling the rotation of the elephant. It is characterized by its use.

The present invention will be explained in detail below based on the drawings. In FIG. 3, the focal length of the lens 9 is F between the distance a between the electromagnetic lens 9 (principal surface) and the object surface 10 and the distance b between the lens 9 and the rear surface 11.
The following m formula holds true.

Kijutoku=sound -...- (1) In the {1} formula, when a is decreased and F>a, a virtual image 12 is formed in front of the lens 9 as shown in FIG. 4, and b<0.

When a further approaches the lens 9, the image plane b also approaches the lens, and if the object surface is very close to the main surface of the lens (a〒0), the image plane will also be at approximately the same position, and the image magnification will be equal to b/a by 1. Become. In other words, in this case, the lens exhibits a rotational effect on the image along with the effect of changing the image position, enlarging the image, and reducing the amount of fringes.
The present invention utilizes the principles described above, and an embodiment thereof is shown in FIG.

In FIG. 5, the same numbers as those used in FIGS. 1 and 2 represent the same components, and the difference from the conventional example is that the image is placed at the position of the bride surface of the intermediate lens 4. An electromagnetic lens 13 for rotation control is provided. The electron beam path when the excitation of the lens 13 is zero is shown by a solid line 14, and the electron beam path when the positive and negative excitation currents are sequentially increased to the lens coil of the lens 13 is shown by a broken line 15 and a two-dot chain line 1.
6. By adjusting the excitation of the lens 13 in this manner, the pseudo position can be rotated in any direction about the optical axis 1 while keeping the magnification of the electron beam image formed on the crab light plate 6 constant. In the case of the apparatus shown in FIG. 5, it is actually difficult to provide another lens 13 near the pole of the projection lens 5 due to the relatively small hole diameter and spacing of the magnetic pole pieces of the projection lens 5. Often. FIG. 6 shows an embodiment for solving the drawbacks of the device shown in FIG. 5, in which an electromagnetic lens 17 for image rotation control and an auxiliary lens 18 are provided at a position relatively distant from the projection lens 5. be.

In the figure, an enlarged image by the intermediate lens 4 is formed near the main surface of the rotation control lens 17, and the image is formed at a position 19 near the projection lens 5 by the auxiliary lens 16.
The magnification of these images is determined by a magnification variable means 22 that controls an imaging lens power supply 21 that supplies current to each imaging lens 3, 4, and 5.
It is possible to display an image at any magnification on the saddle light plate. Furthermore, in the embodiment shown in FIG. 6, the lens power source 23 for the rotation control lens 17 and the auxiliary lens 18 is controlled by the output from the magnification variable means 22, and the rotation of the electron beam image on the light plate as the magnification is varied is controlled. The objects of the invention described above are automatically achieved. Note that the electron beam paths when rotating the electron beam image at the same magnification are indicated by 20, 21, and 22 in the figure.

[Brief explanation of drawings]

Figures 1 and 2 are schematic diagrams for explaining the action of the imaging lens system in an electron microscope, Figures 3 and 4 are schematic diagrams for explaining the principle of the present invention, and Figures 5 and 6 are schematic diagrams for explaining the principle of the present invention. 2A and 2B are schematic diagrams showing embodiment devices of the present invention, respectively. 1: optical axis, 2: sample, 3: objective lens, 4: intermediate lens, 5: projection lens, 6: optical plate, 13, 17: rotation control lens, 18: auxiliary lens, 21: imaging lens power supply,
22: Magnification variable means, 23: Lens power supply. O diagram O Z diagram Zuroen *4 diagram Fire 5 Nails 6 diagram

Claims (1)

[Claims] 1. In an imaging lens system consisting of at least an objective lens, an intermediate lens, and an electromagnetic lens larger than a projection lens, an electromagnetic lens whose main surface is at or near the image formation position by the intermediate lens is provided, and the excitation intensity of the electromagnetic lens is An electron microscope characterized in that it is configured to control rotation of an electron beam image by the imaging lens system by adjusting.