JPS59123147A - Electron lens - Google Patents

Abstract

PURPOSE:To obtain a small easily-manufactured electron lens by making a yoke, for introducing a magnetic flux developing from an excitation coil into a gap in order to form a lens magnetic field, by bundling thin belts of an amorphous alloy containing iron, silicon and boron. CONSTITUTION:A yoke 3 for introducing a magnetic flux developing from an excitation coil 1 into a gap 2 in which a lens magnetic field is to be formed, consists of cylindrical outer and inner yoke sections 3a and 3b and disk-like upper and lower yoke sections 3c and 3d. The yoke 3 is formed by bundling thin belts made of an amorphous alloy containing iron, silicon and boron. The yoke section 3a is made by winding the above thin belts into toroidal form before they are fixed with an adhesive to form bundles 6a-6d prior to sticking them together. The yoke section 3b is also made by forming bundles 8a-8c before they are stuck together in the same manner as above. The yoke sections 3c and 3d are made by stacking thin belts parallel arranged along one direction before they are stuck together to form bundles 7a-7h prior to sticking them together. As a result a small easily-manufactured electron lesn is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an electron lens used in a charged particle beam device such as an electron microscope.

[Prior Art] As shown in FIG. 1, an electron lens used in an electron microscope or the like includes an excitation coil 1 and a yoke 3 for guiding the magnetic flux generated from the excitation coil 1 to a gap 2 for forming a lens magnetic field. It consists of This yoke 3 has a cylindrical outer yoke portion 3a.

It consists of a middle yoke part 3b, a disc-shaped upper yoke part 3c, and a lower yoke part 3d.The cylindrical yoke part must pass magnetic flux in the direction along the axis of the cylinder. The parts must conduct magnetic flux either radially from the center or converging at the center. These yokes are made by cutting regular structural steel or pure iron round bars, but in such electronic lenses, even if the supply of excitation current to the excitation coil 1 is cut off, it will last for about 1 second. Because the magnetic field remains, it is not possible to turn the lens magnetic field on and off or switch it at high speed.

Therefore, in order to solve these drawbacks, electronic lenses capable of high-speed response have been devised and used.

FIGS. 2(a) and 2(b) are for explaining the outer yoke part and the upper (or lower) yoke part of such an electron lens, respectively. As is clear from this figure, in the conventional electron lens, In order to minimize or reduce eddy currents in order to enable high-speed response, each yoke was made using a bundle of thin ribbons made of ferromagnetic material. This ferromagnetic material needed to have high magnetic permeability and high mechanical strength, so silicon steel was used as the material. Therefore, as shown in FIG. 2(a), the outer yoke part is made up of bundles of thin ribbons 4a, 4b,
4c... are made by extending them in parallel along the axis of the outer yoke portion so that a cylinder is formed therebetween. In addition, the upper (lower) yoke part has bundles of thin strips 5a, 5 stacked in a direction perpendicular to the plane of the paper, as shown in FIG. 2(b).
b, 5c, etc. are arranged radially.

Therefore, such a conventional electron lens must first be made by placing a yoke part with a gap S of 4r. Considering that, it is larger than a normal electronic lens.

Second, since there are restrictions on the direction of the bundle of ribbons, manufacturing is troublesome.

[Objective of the invention] 1 The present invention has been made in order to solve the drawbacks of the conventional electronic lens capable of high-speed response.It is an object of the present invention to provide an electronic lens that is small and easy to manufacture. The purpose is

[Structure of the Invention] The present invention provides an electron lens comprising an excitation coil and a yoke for guiding magnetic flux generated from the excitation coil to a gap for forming a lens magnetic field, wherein the yoke is made of iron,
It is characterized by being made by bundling thin strips made of amorphous alloy containing silicon and boron.

[Operation of the invention] When an alloy containing iron (Fe), silicon (Si), and boron (B) is rapidly cooled from a molten state and solidified, 1q of an amorphous (non-crystalline) alloy is produced. The alloy is a ferromagnetic material, and the ribbon made from this alloy has sufficient mechanical strength and has no magnetic anisotropy, so it can be magnetized in any direction, so the ribbon can be bundled to create a yoke. There are no restrictions when doing so, and the direction of the bundle can be matched to the shape of each yoke.

[Example] FIG. 3(a) shows outer yoke portions 6a, 6b, and 6c of an electromagnetic lens based on the present invention.

6d is a toroidally wound ribbon of amorphous alloy made of iron, silicon, and boron and bound together with adhesive.
These bundles 6a, 6b, 6c, and 6d are also bonded to each other with adhesive. Note that the thickness of the ribbon is 20 μm. Third
The figure shows the upper yoke part (or lower yoke part) of the electronic lens based on the present invention.
As is clear from FIG. 3(C) showing the A-A cross section, these are 4-bundles obtained by stacking the thin strips in a direction perpendicular to the plane of the paper, and these bundles are indicated by dotted lines in the figure. -1
They are fixed in parallel in the direction of arrow 1- in order to match the desired shape of the New York section. Incidentally, adhesive is used to adhere the thin ribbons to each other and to fix the bundles 7a, 7b, 7c, . . . , to each other. Similarly, FIG. 3(d) shows the middle yoke portion, which is also a bundle 8a, 8b of the thin ribbons wound in a toroidal shape.

It is created by stacking 8C..., 8e.

In such a configuration, if an excitation current that switches at an extremely fast cycle is supplied to the excitation coil (not shown) of this electronic lens, each yoke will respond rapidly to the switching of the magnetic field generated by the excitation coil, and the lens magnetic field will increase. Can be switched at high speed.

FIG. 4(a) is a diagram for explaining an application example in which the electron lens based on the present invention described above is used as an intermediate lens of an electron microscope, in which 9 is an electron gun, 11.12 is a focusing lens, 13 is an objective lens, 14 is an intermediate lens using an electron lens based on the present invention, 15 is a projection lens, 16
is a fluorescent screen.

17 indicates a sample, and 18 indicates an objective aperture. The intermediate lens 14 is connected to a lens power source 19, which controls the lens state for focusing the sample image formed by the objective lens 13 on the object plane of the projection lens 15, and the diffraction image formed at the position of the objective aperture 18. Lens currents of two different magnitudes are alternately supplied at a rate of, for example, 10 times per second, each having a lens state for forming an image on the object plane position of the projection lens 15. Reference numeral 20 denotes a drive mechanism for inserting and removing the objective diaphragm 18 onto the optical axis 10 at high speed. ” Solenoid coil 20 that applies a force in the direction of pulling the shaft 20a when the force is applied.
c and a drive power source 20d. This drive type rI
A synchronous signal synchronized with switching of the lens current is supplied to A20d from the lens power supply 19, and the aperture 1 is turned on only when the intermediate lens 17I is in a lens state for obtaining a transmitted image.
8 is inserted on the optical axis 10.

In such a configuration, by switching the current supplied to the intermediate lens 14, the excitation state of the intermediate lens 14 is switched, and the optical system mode when obtaining the first transmission image and the fourth transmission image shown in FIG. 4(b) are switched. Since the optical system mode for removing the diffraction image as shown in Fig. In other words, they are superimposed and displayed at the same time. In addition, in FIG. 4(b) and (C), Ef3 indicates an electron beam, and the circle indicates a diffraction image, which is 21.22°23
shows a transmitted image. In addition, by expanding this application example and placing a deflector between the intermediate lens and the fluorescent screen, and deflecting the image by supplying a deflection signal to this deflector in synchronization with switching of the intermediate lens, it is possible to It is also possible to display the transmission image and the diffraction image separately at different locations.

In the above-mentioned embodiments, a ribbon made of an amorphous alloy made of iron, silicon, and boron was used. A thin strip made of an amorphous alloy of iron, silicon, boron, and carbon (C) may also be used.

[Effect] As is clear from the above explanation, in the electronic lens based on the present invention, the direction of the ribbon bundle is adjusted according to the shape of each yoke so that no gaps are created between the ribbon bundles. Since each yoke can be appropriately selected and created, the electronic lens can be made small and easy to manufacture.

[Brief explanation of the drawing]

Figure 1 is a diagram to explain an electron lens, Figure 2 is a diagram to explain a conventional electron lens capable of high-speed response, and Figure 3 is a diagram to explain a conventional electron lens capable of high-speed response.
The figure is a diagram showing one embodiment of the present invention, and FIG. 4 is a diagram showing an example of application of an electron lens based on the present invention to an electron microscope. 1: Excitation coil, 2: Gap, 3: Yoke, 4a, 4
b, 4c, 5a, 5b, 5c, ... bundle of bow silicon steel ribbons, S: gap, 6a, 6b, 6c, 6d, ... 8a,
8b,...,8e Nidroidal-wound iron
Bundle of silicon boron amorphous alloy ribbon, 7a, 7
b,..., 7h: Iron/Silicon/Bundle of 8-ron amorphous alloy ribbon, 9: Electron gun, 11.1
2: Focusing lens, 13: Objective lens, 14: Intermediate lens, 15: Projection lens, 16: Fluorescent screen, 17: Sample, 18
: Objective aperture, 19: Lens power supply, 20: Drive mechanism, 21
, 22.23: Transmission image. Patent applicant JEOL Ltd. Representative Ito-husband

Claims (3)

[Claims] (1) An electron lens consisting of an excitation coil and a yoke for guiding magnetic flux generated from the excitation coil to a gap forming a lens magnetic field, wherein the yoke is a thin film made of an amorphous alloy containing iron, silicon, and poron. An electronic lens characterized by being made by bundling bands. (2) The electronic lens according to claim 11, wherein the outer yoke portion and the middle yoke portion of the yoke are made by toroidally winding the ribbon. (3) The electronic lens according to claim 1 or 2, wherein the upper yoke part and the lower yoke part of the yoke are made by stacking the thin strips arranged in parallel in one direction. .