JP2971518B2 - Electron beam irradiation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a quick and accurate method of installing an electron beam on a desired region by improving a coil for converging an electron beam, particularly in an electron beam irradiation apparatus. It is intended to realize a proper irradiation.

(Prior Art) Recently, the surface modification of these metals or alloys has been achieved by irradiating the surface of a metal or alloy with an electron beam having a small beam diameter generated at a high voltage and a low current in a dot or line shape. Attempts have been made to develop new functional materials.

Other methods for modifying the surface of metals and alloys include laser irradiation, plasma irradiation, and mechanical methods.Especially for electron beam irradiation, there is a handy method that requires the use of a high vacuum. The area is small compared to the above method, and the beam can be deeply penetrated in the thickness direction of the irradiation object. Also, the scanning and swinging of the electron beam is easy, and the irradiation operation can be performed at high speed. It can be applied to industrial materials and has many advantages such as high thermal efficiency, and the above-mentioned electron beam irradiation is an extremely effective means in the surface modification of functional materials such as oriented silicon steel sheets. .

(Problems to be Solved by the Invention) In applying the electron beam irradiation technique, for example, a high-speed continuous vacuum apparatus by an air-to-air method must be developed so that a steel plate to be mass-produced 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. The development of a device capable of irradiating, or a device capable of irradiating uniformly, regularly and quickly over the width direction of a steel plate to be irradiated, and the establishment of a scanning direction remain important issues.

Here, the above-mentioned high-speed continuous vacuum apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 64-65265, and an apparatus capable of obtaining an electron beam having a small beam and a large penetration depth is disclosed in Japanese Patent Application No. As disclosed in the specification of JP-A-63-268316, it has already reached the stage of industrialization, but a device capable of uniformly, regularly and quickly irradiating an electron beam across the width of a steel sheet to be irradiated is still insufficient. It was the current situation that nothing was obtained.

The inventor of the present invention first irradiates the electron beam over the width direction of the steel sheet while appropriately correcting the focal length of the beam so that the beam intensity is always the same even when the irradiation area of the electron beam is changed. (Hereinafter referred to as the dynamic focus method), and proposed a method for producing a low iron loss unidirectional silicon steel sheet which subdivides the magnetic domain structure of the steel sheet and further improves the product characteristics (Japanese Patent Application No. 63-63). −
268316).

The above-described technique is to control a current flowing through a focusing coil so that accurate beam focusing is performed according to a position at which an electron beam is irradiated.Specifically, predetermined data is converted from a D / A converter. This 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 determined by the current value flowing through the focusing coil. Since the amplifier is controlled by the current amplification, 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 quick beam irradiation because of the followability of the deflection frequency in the deflection coil that controls the deflection of the electron beam.

Note that control by voltage amplification is also conceivable, but when voltage amplification is performed by an amplifier, a conversion resistor is necessary to allow current to flow through the focusing coil.
When the resistance value R changes to (R + ΔR) due to a temperature change or a temporal change, the current i flowing through the focusing coil becomes i = v / (R + jwL) i ₁ = v / (R + ΔR + jwL) where R + ΔR; resistance value ΔR: resistance value L: Inductance of coil j: Complex number w: Angular frequency In other words, D / A
Although the command value from the converter does not change, the current flowing through the focusing coil changes, and this has the disadvantage that the focal length of the electron beam becomes inaccurate.

It is also conceivable to prepare a current control amplifier and a voltage control amplifier for one converging coil, and to supply a current by interconnecting them (see FIG. 6). However, in this method, the current control amplifier performs constant current control and always keeps the current flowing to the output side constant. Therefore, it is difficult to control the variation current flowing for dynamic focus because it is corrected.

It is an object of the present invention to avoid the above-described problems in the electron beam irradiation using the dynamink focus method and to propose a novel device capable of rapidly and uniformly irradiating an electron beam to a substrate or the like to be irradiated. Is the purpose.

(Means for Solving the Problems) The present invention provides an electron gun that emits an electron beam, a focusing coil that focuses the electron beam emitted by the electron gun,
In an electron beam irradiation apparatus including a deflection coil for irradiating a predetermined region of the electron beam converged by the converging coil,
An electron beam irradiation apparatus characterized in that at least two types of convergence coils of a current control type and a voltage control type are provided as the convergence coils.

FIG. 1 shows an example of an electron beam irradiation apparatus according to the present invention.
a, 1b, a casing for forming a vacuum chamber, 2 is an electron gun for emitting an electron beam B, and this electron gun 2 is a high-pressure insulator 2a, a filament 2b for emitting electrons,
An anode 2c for accelerating the emitted electrons and a column valve 2d for constantly evacuating the electron beam generator. Reference numeral 3 denotes a converging coil for converging the electron beam B emitted from the electron gun 2, and here, a converging coil provided at the upper portion is a current controlling type converging coil (hereinafter referred to as a first coil). Also, the one installed at the bottom is shown as a voltage control type focusing coil (hereinafter referred to as a second coil).
A deflecting coil 4 changes the traveling direction of the converged electron beam and irradiates a predetermined area with the deflecting coil. The deflecting coil 4 is not shown, but is a D / A converter for converting a scanning signal of the electron beam B. And a deflection amplifier for amplifying the signal output from the D / A converter, and a speed-up circuit for quickly transmitting the signal amplified by the deflection amplifier to the deflection coil.

(Effect) As shown in the schematic diagram of FIG. 2, the conventional focusing coil arranged in the electron beam irradiation apparatus has difficulty in controlling the current amplification because of the followability to the deflection frequency. That is, when irradiating an electron beam, scanning is performed while the beam spot is stopped on the substrate, and if the moving speed of the beam is low, a trail of trailing by the beam irradiation is formed, which causes various characteristics to deteriorate. Was. Further, when the amplifier is of the voltage control type as shown in FIG. 3, there is a disadvantage that the current value flowing through the focusing coil fluctuates due to the conversion resistor arranged in the circuit, and accurate irradiation cannot be performed. It is.

In the present invention, as shown in FIG. 4, the focusing coil 3 installed in the electron beam irradiation device is composed of a first coil 3a of a current control type and a second coil 3b of a voltage control type. and, in the beam irradiation to the substrate K immediately below the electron gun 2 (refer to point P in the substrate K of FIG. 1) flows to the first coil 3a by the current control of the amplifier a ₁ because the focal distance does not substantially change to keep the current constant, in contrast beam irradiation in each side region of the substrate K, it is so arranged to adjust the second coil 3b by the voltage control of the amplifier a ₂ the variation due to the deflection of the beam B, The combined magnetic field with the first coil and the second coil irradiates so that the beam intensity is quickly and equal over a wide area. Here, the conversion resistor provided in the second coil may cause a current flowing in the coil to fluctuate due to a change in temperature or a change with time, but a change in the focus value in the voltage control (a current flowing in the second coil). Current fluctuation) is about 15
Since it is about 20%, the effect on product quality is very small.

The coil of the current control type and the coil of the voltage control type can be arranged along the electron beam irradiation direction as shown in FIG. 1 (the arrangement order is not particularly limited). A concentric arrangement as shown in FIG. 5 can also be taken. Further, the number of the converging coils is not limited to the case where one coil of the current control type and one coil of the voltage control type are arranged, and the number of the converging coils can be increased as needed.

Incidentally FIG. 6 is a current control amplifier A ₁ and the voltage controlled amplifier A ₂ provided for a single convergence coil, an example of supplying a current of (i ₂ + i ₃₎ with respect to the convergence coil 3 . However, in such a configuration, the current control amplifier for the current flowing in the output side has the constant current control is always kept constant, suppress a variation current i ₃ for dynamic focus flows convergence coil And that control is offset.

(Examples) Example-1 C: 0.051 wt% (hereinafter simply referred to as%), Mn: 0.26%, P: 0.
On the surface of a cold-rolled steel sheet containing 009% and S: 0.016% and having a thickness of 0.8 mm, applying the apparatus shown in FIG. 1 above, the acceleration voltage of the first coil (current control): 225 KV , Acceleration current: 0.9mA
And the second coil (voltage control) is given a variation of about 13% so that the beam intensity becomes equal in accordance with the variation of the irradiation area, and the second coil (voltage control) has an interval of 100% along the width direction of the steel sheet. ~ 1
The electron beam is radiated in the form of dots under the conditions of 500 μm and intervals of 100 to 2000 μm along the longitudinal direction, and the electron beam is irradiated based on the samples cut out from the central region and both end regions of the obtained electron beam irradiated steel sheet. As a result of investigating characteristics such as trace conditions, deep drawability and sharpness of the steel plate, good characteristics were obtained.

Example 2 After an insulating film was formed on a unidirectional silicon steel sheet subjected to finish annealing, the acceleration voltage of a first coil (current control) was applied to the surface of the steel sheet by applying the apparatus according to the present invention. : 250KV,
Acceleration current: 1.2 mA, a variation of about 16% is applied to the second coil (voltage control) so that the beam intensity remains constant even when the irradiation area changes, irradiation interval: 6 mm, beam irradiation atmosphere The electron beam was irradiated in the form of dots under the condition of vacuum degree: 5 × 10 ⁻⁴ Torr, and the iron loss value representing the product properties of the obtained steel sheet was examined.

As a result, it was confirmed that the iron loss value W _17/50 exhibited a favorable value of 0.77 W / kg.

(Effect of the Invention) Thus, 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, and the product quality as well as the productivity can be improved. Further improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the configuration of an electron beam apparatus according to the present invention, FIG. 2 is an explanatory view of a focusing coil, FIG. 3 is an explanatory view of a focusing coil installed in a conventional type apparatus, and FIG. FIG. 5 is a view showing another example of a converging coil suitable for being installed in an apparatus, FIG. 5 is a concentric arrangement diagram of a first coil and a second coil, and FIG. 6 is a view showing another example of a converging coil. is there. DESCRIPTION OF SYMBOLS 1 ... Casing, 1a, 1b ... Exhaust port 2 ... Electron gun, 2a ... High-pressure insulator 2b ... Filament, 2c ... Anode 2d ... Column valve 3, ... Converging coil 3a ... First coil .., 3b... Second coil 4... Deflecting coil, B... Electron beam K... Substrate, P.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fukuhachi Kanai 5-7-1 Shiba, Minato-ku, Tokyo Within NEC Corporation (56) References JP-A-61-216753 (JP, A) JP-A 58-5954 (JP, A) JP-A-2-118022 (JP, A) Japanese Utility Model Showa 57-133854 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 37 / 30 H01J 37/141 H01J 37/21

Claims (1)

(57) [Claims] An electron gun for emitting an electron beam, a converging coil for converging an electron beam emitted by the electron gun, and a deflection coil for irradiating a predetermined region with the electron beam converged by the converging coil. 2. An electron beam irradiation apparatus according to claim 1, wherein at least two types of focusing coils are provided as said focusing coils, a focusing coil of a current control type and a focusing coil of a voltage control type.