JP3100648B2 - High voltage / low current electron beam irradiation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention aims at realizing a quick and accurate irradiation of an electron beam to a desired area on a substrate or the like by modifying the electron beam irradiation apparatus.

[0002]

2. Description of the Related Art Recently, a surface modification of a metal or alloy has been carried out by irradiating the surface of the metal or alloy with an electron beam having a small beam diameter generated at a high voltage and a low current in a dot shape or a line shape. Attempts have been made to develop new functional materials.

Means for modifying the surface of metals and alloys include laser irradiation, plasma irradiation and mechanical methods in addition to electron beam irradiation. In particular, electron beam irradiation requires the use of a high vacuum. Despite some handicap, the irradiation area is small compared to the above method, and the beam can penetrate deeply in the thickness direction of the irradiation target, and the scanning and swinging of the beam is easy and the irradiation work is fast. It has many advantages such as being able to be applied to large industrial materials, and having good thermal efficiency. In the surface modification for functional materials such as oriented silicon steel sheets, the above-described electron beam irradiation is used. Was a very effective means.

[0004]

In applying the electron beam irradiation technique, for example, a high-speed continuous vacuum apparatus using an air-to-air method must be developed so that a mass-produced steel sheet can be continuously processed. In addition, in such irradiation technology, it is also necessary to further reduce the beam diameter of the electron beam generated at high voltage and low current and obtain a beam with a deeper penetration depth. Development of a device capable of irradiating, or development of a device capable of irradiating uniformly, regularly and quickly over the width and / or longitudinal direction of a steel plate to be irradiated, and establishment of a scanning method remain as important issues.

The above-mentioned high-speed continuous vacuum apparatus is disclosed in, for example, JP-A-64-65265, and the apparatus capable of obtaining an electron beam having a small beam and a large penetration depth is disclosed in Japanese Patent Application Laid-Open No. 64-65265. As disclosed in the specification of Japanese Patent Application No. 63-268316, which has already reached the stage of industrialization, the electron beam is uniformly and quickly and uniformly distributed in the width direction or the longitudinal direction of the steel sheet to be irradiated. As for a device capable of performing irradiation, a sufficient device has not yet been obtained.

[0006] The inventors of the present invention have a technique relating to this point.
First, even if the irradiation area of the electron beam changes, irradiation is performed over the width direction of the steel sheet (hereinafter referred to as the dynamic focus method) while appropriately correcting the focal length of the beam so that the same beam intensity is always obtained. Proposed a method for producing a low iron loss unidirectional silicon steel sheet by further subdividing the magnetic domain structure of
68316).

The above-mentioned technique is of a type in which a current flowing through a converging coil is controlled so that an accurate beam focus is obtained in accordance with a position to which an electron beam is irradiated. The output signal is output from the converter and the output signal is amplified by an amplifier, and a current is passed through the focusing coil so as to have a predetermined focal length. According to such an irradiation method, the beam focus of the electron beam is adjusted by the focusing coil. Since the current is determined by the value of the current flowing through the amplifier, the amplifier only needs to be a current amplification control. Therefore, the product characteristics can be remarkably improved as compared with the conventional method in which the irradiation intensity of the electron beam varies depending on the irradiation position.

However, there is a disadvantage that it is very difficult to control the current amplification when performing rapid beam irradiation because of the followability of the deflection frequency in the deflection coil that controls the deflection of the electron beam. In order to enable simple control using the dynamic focus method, the electron beam converging coil includes at least two types of converging coils: a converging coil of a current control type and a converging coil of a voltage control type. Although an irradiation device (see Japanese Patent Application No. 2-145492) has been proposed, it is difficult to uniformly irradiate the electron beam from the center to the end in the width direction of the steel plate even with this device (the center in the width direction). Even if the part has a round beam shape, it becomes elliptical as it goes to the end), but at present, there is no effective means yet.

The above-mentioned problems in the electron beam irradiation to which the dynamic focus method is applied can be avoided, and a substrate or the like to be irradiated can be quickly and uniformly irradiated with an electron beam generated at a high voltage. It is an object of the present invention to propose a simple device.

[0010]

According to the present invention, there is provided an electron beam generator for emitting an electron beam, a converging coil for converging the electron beam emitted from the electron beam generating unit, and a predetermined coil for converging the electron beam. In an electron beam irradiation apparatus having a deflection coil for irradiating an area, a gas insulating mechanism is installed in the electron beam generating unit, and the convergence coil is formed into a current control type and a voltage control type. Comprising at least two types of focusing coils of
A high-voltage / low-current type electron beam irradiation apparatus (first invention), wherein a water-cooling slit is disposed on the entrance side of the focusing coil, and astigmatism is provided inside the focusing coil. Stingmatol, which is responsible for the correction of the above, is arranged (second invention).

FIG. 1 shows an example of a high-voltage / low-current type wide-angle deflection electron beam irradiation apparatus according to the present invention.
In the figure, reference numeral 1 denotes a casing provided with exhaust ports 1a and 1b to form a vacuum chamber, 2 denotes an electron beam generator for emitting an electron beam B, and 2a denotes an electron beam emitted from an electron gun of the electron beam generator 2. A multi-stage anode for accelerating B, 2b is a high-voltage cable, 2c is a gas insulation mechanism that ensures electrical insulation by gas when a high voltage is applied (gas uses fluorinated gas), and 2d is a column valve. The column valve 2d always keeps the electron beam generator at a high vacuum. Also, 3
Is an alignment coil, 4 is a cooling slit (one-step stop) having a tapered shape useful for reducing the background and increasing the intensity of the electron beam, and 5 is a converging coil for converging the electron beam B. In the figure, the one installed at the top is shown as a converging coil 5a of a current control type, and the one installed at the bottom is shown as a converging coil 5b of a voltage control type. A deflecting coil 6 changes the traveling direction of the electron beam converged by the convergence coil 5 and irradiates a predetermined area with the deflecting coil. A D / A converter for conversion, a deflection amplifier for amplifying a signal output from the D / A converter, and a speed-up circuit for quickly transmitting the signal amplified by the deflection amplifier to a deflection coil are provided. Reference numeral 7 denotes a Sting matol for correcting astigmatism, which is used to correct the beam into a circle by dividing the circumference into a number of divisions and generating a +-magnetic field.

The Stingmatol 7 is of a 4-pole, 8-pole or 16-pole type, but a large number of 8-pole types are usually used in order to effectively make the beam circular.
Here, in the present invention, in order to generate a stable electron beam under a high voltage of about 200 to 500 KV and a low current of 0.5 to 5 mA, the electron beam generating unit having the above-described configuration is replaced with the conventional oil insulation. Gas insulation.

In the present invention, a gas insulating mechanism 2c is installed in the electron beam irradiation apparatus, or a cooling slit 4 and a sting matol 7 are installed in addition to the gas insulating mechanism 2c. It is assumed that it is constituted by a coil 5a and a coil 5b of a voltage control type. In such an apparatus, in order to perform beam irradiation on the substrate K immediately below the electron beam generating unit 2 (see the point P on the substrate K in FIG. 1), since the focal length hardly changes, the coil is controlled by the current control of the amplifier. 5a is kept constant while the substrate K
In the beam irradiation on both side areas of
Is adjusted by applying a current to the coil 5b by voltage control of the amplification amplifier, whereby a beam having a rapid and equal beam intensity over a wide range due to the combined magnetic field in the converging coil 5 is obtained. An electron beam having a uniform shape can be irradiated.

The converging coil 5 is not limited to the case where one coil of current control type and one coil of voltage control type are respectively arranged.
The installation number can be increased as needed.

FIG. 2 shows the relationship between the acceleration voltage and the current of the electron beam generator. Currently, the most widely used electron microscope (including scanning electron microscope) has an accelerating voltage of 20 to 3000 KV.
In order to increase the resolution of the image, the current is extremely small, from 10 ^-3 to 10 ^-8 , while the acceleration voltage is relatively low in electron beam melting furnaces, electron beam welding machines, plasma (HCD) coating, etc. The current is often used, especially in the area of about 65KV (some are about 150KV) where electron beam welding machines do not generate a large amount of X-rays. The electron beam irradiation apparatus according to the present invention is in an area as shown in FIG. 2 (acceleration voltage: 200 to 500 KV, acceleration current: about 0.05 to 5 mA), and the technique used in the electron microscope is directly applied. It is impossible to do so, and in order to stably manufacture industrial products, it is indispensable to make the structure of the electron optical system in the apparatus simple and stable in performance.

[0016]

EXAMPLE A steel sheet having an insulating film containing phosphate and colloidal silica as main components, C: 0.001 wt% (hereinafter simply referred to as%), Mn: 0.07%, Si: 3.25%, Se: 0.001%
The above-mentioned Fig. 1 shows a unidirectional silicon steel sheet
Applying the device with the configuration as shown in the figure, the acceleration voltage of the current control type coil: 250 KV, the acceleration current: 0.8 mA, and the beam intensity of the voltage control type coil is always the same according to the variation of the irradiation area. Irradiate the electron beam (beam diameter: 0.7 mmφ) in dot form under the condition that the interval is 150 μm along the width direction of the steel sheet and the interval is 5 mm along the longitudinal direction, giving a variation of about 15% so that Then, the error of the beam diameter in the width direction of the steel sheet was measured, and the iron loss value of the obtained electron beam-irradiated steel sheet was investigated based on samples cut out from the central area and both end areas.

As a result, the irradiation error is about ± 10%,
In addition, the _iron loss value W _{17/50 of} the sample taken from the central region of the steel sheet
Is 0.76 W / Kg, the iron loss value W of the sample taken from both end areas
_17/50 was 0.77 W / Kg, and a product of uniform quality could be obtained.

[0018]

As described above, according to the present invention, in the electron beam irradiation useful for the surface modification of metals and alloys, the electron beam can be quickly and uniformly irradiated over a wide range, so that the product quality can be improved and the productivity can be improved. Can be expected to be further improved.

[0019]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of an electron beam device according to the present invention.

FIG. 2 is a graph showing a relationship between an acceleration voltage and a current for each use of an electron gun. DESCRIPTION OF SYMBOLS 1 Casing 1a, 1b ... Exhaust port 2 Electron beam generation part 2a Multistage anode 2b High voltage cable 2c Gas insulation mechanism 2d Column valve 3 Alignment coil 4 Cooling slit 5 Focusing coil 5a Current control type coil 5b Voltage control type coil 6 Deflection coil 7 Stingmatol B Electron beam K Substrate P Center point of substrate width

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01J 37/153 H01J 37/153 Z // B23K 15/00 502 B23K 15/00 502 (72) Inventor Souhachi Kanai Tokyo 7-1, Shiba 5-chome, Minato-ku NEC Corporation (72) Inventor Masaaki Kawanami 5-7-1, Shiba, Minato-ku Tokyo, Japan (56) References JP-A-2-40910 (JP) JP-A-58-32349 (JP, A) JP-A-57-112455 (JP, U) Patent 2971518 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37 / 317 C21D 1/09 H01J 37/06 H01J 37/141 H01J 37/153 B23K 15/00 502

Claims (2)

(57) [Claims] An electron beam generator for emitting an electron beam;
An electron beam irradiator comprising: a converging coil for converging an electron beam emitted from the electron beam generating unit; and a deflection coil for irradiating a predetermined region with the electron beam converged by the converging coil. A high-voltage / low-current method, wherein an insulating mechanism is installed, and the convergence coil comprises at least two types of convergence coils of a current control type and a voltage control type. Electron beam irradiation device. 2. The apparatus according to claim 1, wherein a water-cooling slit is arranged on the entrance side of the focusing coil, and Stingmatol for correcting astigmatism is arranged inside the focusing coil.