JP2546143B2 - Electron gun for electron beam processing machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun for an electron beam processing machine, and more particularly to an indirectly heated hot cathode electron gun.

[0002]

2. Description of the Related Art Conventionally, electron guns of electron beam devices are roughly classified.
The hot cathode electron gun, field emission electron gun, and plasma electron gun are used.
It has been used.(Electron / Ion Beam Handbook 2
Edition pp. 115~173. Nikkan Kogyo Shimbun, Showa 61
Year). Among them, the hot-cathode electron gun has long been an electron source.
Widely used. Hot cathode electron gun is a pure metal shade
Electrodes, monatomic layer cathodes and oxide cathodes are roughly classified. Typically
Pure using refractory metal such as tungsten or tantalum
Due to its good stability, the metal cathode is not suitable for semiconductor manufacturing equipment.
Is it a processing device that requires a high-precision microbeam?
, Electron beam processing that requires a large current in a low vacuum atmosphere
It has been widely used in devices. Most widely used
For tungsten cathode, straight type, hairpin type, mesh type
NewType, ribbon type, etc.heat
Type) and a cylindrical or button type refractory metal cathode.
The method of heating by child impact (indirect heating type) has been used.
Was. Direct heating type is easy to manufacture and good for excessive heat fluctuation
It is also that the indirectly heated type has a long life.
Peculiar to eachAdvantage ofhave.

[0003]

In the case of the direct heating cathode, the pure metal hot cathode electron gun for the conventional electron beam processing machine described above does not heat up to the operating temperature by directly energizing the refractory metal. Therefore, in order to efficiently convert the applied current into heat, the cross-sectional area of the cathode is made small so that the electric resistance becomes high, and generally the cathode 2 has a structure as shown in FIG.
Since a hairpin type or a ribbon type is used for 3, there is a defect that the metal is evaporated by high temperature, the cathode material is consumed by sputtering due to ion bombardment to the cathode during beam irradiation, and the life is short.

The indirectly heated cathode (not shown) is the main cathode.
Since a heating filament separately provided around or behind the high melting point metal used as the auxiliary cathode of the auxiliary electron gun is heated by the electron impact method, a power source for the auxiliary cathode is required, Although it requires an extra heating power and the cathode has a longer life than the direct heating type, it has drawbacks such as being limited by the life of the heating filament.

[0005]

Electron beam processing machine electron gun of the present invention SUMMARY OF] is an electron beam processing machine for an electron gun of the installed behind heated indirectly heated in the first vacuum container, behind heating
The auxiliary cathode of the auxiliary electron gun for impregnation type cathode, lanthanum hexaboride
(Hereinafter referred to as LaB ₆ ) and oxide cathode
Using a material of any of the low work function of Chi, also a second installed the rear heating auxiliary electron gun to the first vacuum chamber
It is hermetically sealed in a vacuum container, and the auxiliary electron gun for heating the back is included.
Of the walls of the vacuum container constituting the second vacuum container
The vacuum container wall facing the electron emission surface of the sub-cathode of the auxiliary heating electron gun for back heating is made of a refractory metal, and the refractory metal is used as a main cathode for generating a main electron beam.

Further, those having a getter in the second vacuum container, and that a combination of heating power and the secondary cathode heater power supply of the getter further after evacuation of the second vacuum chamber, said second sealing the vacuum container, by blowing the getter of the second true <br/> empty container at regular intervals,
The present invention also includes a device that constantly maintains the second vacuum container at a high vacuum.

[0007]

[Action] In this way, e-Bee behind heating auxiliary electron gun
Inside the first vacuum container in which the electron gun for the machine tool is installed
Sealed in the second vacuum container which is installed in, also, a second vacuum to entailment auxiliary electron gun behind heated using getter
By be Rukoto the vessel at a high vacuum, impact and reduce contamination or ionization of the residual gas of the residual gas to the secondary cathode, further metal vapor generated during welding because it is sealed in the second vacuum container It is possible to prevent the ion bombardment
it can. As a result, it has a low work function that is weak against ion bombardment.
Impregnated cathode or LaB ₆ or oxide cathode is used as a sub-cathode
It is possible to lower the operating temperature of the sub-cathode.
Therefore, the operating power of the sub-cathode can be reduced .

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows an embodiment of an electron gun for electron beam processing according to the present invention, which is an electron gun which operates on the principle of a three-electrode system. A target that emits an electron gun or electron beam
(Shown) is installed in a vacuum container (not shown)
The high voltage applied to the
It is supplied from a source through a current introduction terminal (not shown).

The electron gun for this electron beam processing machine has a main cathode 8
With the, the weather Ne belt electrode 1, an anode 2. The main cathode 8 made of a refractory metal such as tungsten or tantalum is configured as a part of a vacuum container 10. Vacuum container 10
A back heating auxiliary electron gun 9 including a sub-cathode 5, an insulator support 6, and a sub-electron beam correction electrode 11 is provided inside, and the inside of the vacuum container 10 is evacuated and then sealed. To maintain a high vacuum . The sub-cathode 5 is held by the insulator support 6 and is insulated from the vacuum container 10. Sub-cathode 5
Is a current introduction terminal 7 that can introduce current while maintaining a vacuum.
Heater power is supplied from the heater power supply 15 through the heater to heat it to the sub-cathode operating temperature. From the operable sub-cathode 5, the irradiation direction of the sub-electron beam 4 is corrected by the sub-electron beam correcting electrode 11 by the sub-accelerating voltage 14, and the main cathode 8 is irradiated with the sub-electron beam 4. The main cathode 8 which has been subjected to electron impact is heated to an operable temperature, and the main electron beam 3 is anode- generated by the main acceleration voltage 12 which is a potential difference between the anode 2 and the main cathode.
The main electron beam emitted in the direction 2 is the anode.
The light passes through the opening and is irradiated onto a target (not shown).
The main electron beam current is controlled by the bias voltage 13 applied to the Wehnelt electrode 1.

The cathode material of the sub-cathode 5 is evacuated to a high vacuum.
Since it is installed in the vacuum container 10 having a high temperature, it is possible to use a cathode material having a low work function that can operate only in a high vacuum. FIG. 1 shows a structure using an impregnated cathode as an example. Impregnated cathode, as shown in FIG. 4, the impregnation member 19 attached to the support sleeve 20, the heater 22 and Potte I ring member 21 is in the embedded structure support sleeve 20. Generally, the operating temperature of an impregnated cathode is around 1000 ° C , which is less than half that of a tungsten cathode, and the power required for operation is less than half.
It When low power is taken into consideration, Vogue is used as another cathode material .
LaB ₆ such as Le type It is also possible to use a system cathode (not shown) or an oxide cathode ( not shown).

[0012] Figure 2 is a getter 16 in the vacuum vessel 10 to entailment sub cathode 5 shown in FIG. 1, there is shown the the provided structure getter supply 17. The vacuum container 1 is evacuated and then sealed, and the getter 16 is blown to remove the vacuum container 1.
The inside of 0 can be further vacuumed. FIG. 3 shows FIG.
The getter power supply 17 shown in (1) is also used as the heater power supply 15 to simplify the power supply structure. Getter 16
This is possible by using the heater changeover switch 18.

[0013]

As described above, according to the present invention, by installing the sub-cathode of the auxiliary electron gun for back heating in the high vacuum container, it is possible to extremely reduce the contamination by residual gas.
Wear. As a result , an impregnated cathode with a low work function, LaB ₆ System cathode, to be capable of an oxide cathode or the like ing. These low work function cathodes range from about 1000 ° C
It can operate at 1600 ° C and has a pure metal cathode , eg
100 compared to the operating temperature of the Nungsten cathode of 2700 ° C
It operates at a low temperature of 0 ° C or more, so it is necessary to operate the auxiliary cathode.
Power consumption can be reduced by 50% or more
It In addition , the sub-cathode is operated at a low temperature, which extends the service life.
Will also be possible. As a result, there is an effect that both the long life and the low power consumption of the indirectly heated type negative electrode, which have been problems in the past, can be achieved at the same time.

[Brief description of drawings]

FIG. 1 is a schematic view of a basic structure of an electron gun that operates by a three-electrode system in an embodiment of the electron gun for an electron beam processing machine of the present invention.

FIG. 2 is a schematic diagram of a structure in which a getter is provided in a vacuum container 10 containing the sub-cathode 5 shown in FIG.

FIG. 3 is a schematic diagram of a structure in which the power source of the getter 16 shown in FIG. 2 is also used as a sub-cathode power source.

FIG. 4 is a schematic structural diagram of an impregnated cathode.

FIG. 5 is a schematic structural diagram of a conventional cathode.

[Explanation of symbols]

1 Wehnelt electrode 2 Anode 3 Main electron beam 4 Sub-electron beam 5 Sub-cathode 6 Insulator support 7 Current introduction terminal 8 Main cathode 9 Back heating auxiliary electron gun 10 Vacuum container 11 Sub-electron beam correction electrode 12 Main acceleration voltage 13 Bias voltage 14 secondary accelerating voltage 15 heater power supply 16 getter 17 a getter power 18 changeover switch 19 impregnant 20 support sleeve 21 Potte _Lee ring member 22 heater 23 cathode

Claims (4)

(57) [Claims] 1. An electron gun for a backside heating indirectly heated type electron beam processing machine installed in a first vacuum container, wherein the auxiliary cathode of the backside heating auxiliary electron gun is an impregnated cathode, hexahedron.
Low work of either lanthanum fluoride or oxide cathode
Using a function of the material, also said the rear heating auxiliary electron gun
The second vacuum container, which is sealed in a second vacuum container installed in the first vacuum container and includes the back heating auxiliary electron gun,
The rear heating auxiliary electronic sub-cathode electron emission surface of the gun facing the vacuum chamber wall of the vacuum vessel wall constituting constituted by refractory metal, the main cathode for primary electron beam generating the high-melting point metal An electron gun for an electron beam processing machine, which has a structure as follows. 2. The electron gun for an electron beam processing machine according to claim 1, further comprising a getter in the second vacuum container. 3. The electron gun for an electron beam processing machine according to claim 1, wherein the getter heating power source and the sub- cathode heater power source are used together. 4. After evacuating the second vacuum container,
Sealing the second vacuum vessel, said by the getter in the second vacuum container skip at regular intervals, always electron beam according to claim 2 or 3 to maintain the vacuum vessel of the second high vacuum Electron gun for processing machines.