JP2003066199A - Electron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the shape of the end of electron beam able to the trimmed and make mitigable the variation of extraction electrode by reducing temperature difference caused near the end of the extraction electrode. SOLUTION: The electron source 6a is composed of a hot cathode 8 generating electron 10 in surface shape and two extraction electrodes extracting generated with it as an electron beam 10a and is provided with an upstream side first extraction electrode 12 and a downstream side second extraction electrode 14 with the same electric potential as it. In between the first extraction electrode 12 and the second extraction electrode 14, masks 26 shielding the end region of the electron 10 in surface shape from the hot cathode 8 and shaping the end parts of the electron beam 10a extracted out of the second extraction electrode 14 are provided at both ends in Y-direction of the second extraction electrode 14. Each of the masks 26 consists of porous conductor and electrically insulated from other conductor and is in floating potential state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron source used in, for example, an electron beam irradiation apparatus and the like, and more specifically to an electron source configured to extract an electron generated by a hot cathode as an electron beam through an extraction electrode. Relates to an improvement in a mask that blocks an end region of electrons from a hot cathode and shapes an end of an electron beam extracted from an extraction electrode.

[0002]

2. Description of the Related Art An example of an electron beam irradiation apparatus having a conventional electron source is shown in FIG. This electron beam irradiation apparatus uses an electron beam 10
a is relatively short in the X direction without scanning
This is a device that generates an electron beam 10a having a planar shape (for example, a rectangular shape) relatively long in the Y direction orthogonal to the direction, and is called a non-scanning type or an area type. The Y direction is called the irradiation width direction, and the X direction is called the irradiation object transport direction.

In this electron beam irradiation apparatus, a cylindrical shield electrode 4 which is long in the Y direction is provided in a cylindrical vacuum container 2 which is long in the Y direction.
Is arranged, and the electron source 6 which is long in the Y direction is arranged therein.

In this example, the electron source 6 includes a hot cathode 8 for generating electrons 10 in a planar shape (for example, a flat rectangular shape) and two sheets of electrons 10 for extracting the electrons 10 generated by the hot cathode 8 as an electron beam 10a. It is a porous extraction electrode and is provided with a first extraction electrode 12 on the upstream side and a second extraction electrode 14 on the downstream side having the same potential as this.

The hot cathode 8 has a structure in which a plurality of linear (also referred to as rod-shaped) filaments 9 extending in the X direction are arranged in the Y direction, as in the example shown in FIG. However, a flat hot cathode or the like may be used as the hot cathode 8.

Both the first extraction electrode 12 and the second extraction electrode 14 are porous electrodes, one example of which is shown in FIG. The first extraction electrode 12 has a large number of electron extraction holes 12a.
have. The second extraction electrode 14 also has a structure similar to this. The second extraction electrode 14 is arranged near the opening of the shield electrode 4.

Referring again to FIG. 6, the shield electrode 4, the first extraction electrode 12 and the second extraction electrode 14 are made to have the same potential, and between them and the hot cathode 8, the hot cathode 8 side is a negative electrode. Then, the extraction voltage Ve (for example, about 200 V to 500 V) for extracting the electron beam 10a is applied.
Further, the opening of the vacuum container 2 has a window foil 18 for transmitting the electron beam 10a, and an irradiation window 20 having the same potential as the vacuum container 2 is provided. In between, the side of the second extraction electrode 14 or the like is set to a negative electrode and the acceleration voltage Va (for example, 30 kV to
(Approx. 300 kV) is applied.

In this way, the electron beam 10a extracted and accelerated from the electron source 6 is taken out of the vacuum container 2 through the irradiation window 20 and irradiated on the irradiation object 22 to modify it. Is used for processing.

By the way, the end region of the planar electron 10 generated in the hot cathode 8 (the end region in the Y direction is the focus here, the same applies hereinafter) is the other portion (central region).
Since the electron density is much lower than that of, it cannot be used for irradiation of the irradiation object 22. Further, when such an end region of the electron 10 is directly drawn out as a part of the electron beam 10a through the first extraction electrode 12 and the second extraction electrode 14, the end of the electron beam 10a is irradiated with the irradiation window 2.
There is also a problem that it collides with the end portion of 0 and heats it undesirably.

In order to solve such a problem, conventionally, the end region of the electron 10 from the hot cathode 8 is shielded between the first extraction electrode 12 and the second extraction electrode 14 and the second extraction electrode 14 is cut off.
The plate-shaped mask 16 for shaping the end portion of the electron beam 10a extracted from the extraction electrode 14 is provided as Y of the second extraction electrode 14.
They are provided at both ends in the direction (see also FIG. 7).

[0011]

However, when the plate-shaped mask 16 as described above is provided, the thermal radiation 24 generated from the hot cathode 8 (only a part of the radiation is shown in FIG. 6). Also reaches the second extraction electrode 14 in the absence of the mask 16 (that is, between the two masks 16), but is blocked by the mask 16 at the end of the second extraction electrode 14 and the second extraction electrode 14 Do not reach 14. The occurrence of the location where the thermal radiation 24 reaches and the location where the thermal radiation 24 does not reach generate a large temperature difference near the end portion of the second extraction electrode 14, and the deformation (thermal strain) of the second extraction electrode 14 increases. .

When the deformation of the second extraction electrode 14 becomes large, for example, the distortion of the accelerating electric field due to the acceleration voltage Va between the second extraction electrode 14 and the irradiation window 20 becomes large, and thus the electron beam 10a taken out to the outside. The uniformity of the dose distribution is deteriorated.

Therefore, the present invention is capable of shaping the end portion of the electron beam and reducing the temperature difference generated near the end portion of the extraction electrode to mitigate the deformation of the extraction electrode. The main purpose.

[0014]

A first invention is a hot cathode for generating electrons and two extraction electrodes for extracting the electrons generated by the hot cathode as an electron beam, and a first extraction on the upstream side. In the electron source including an electrode and a second extraction electrode on the downstream side having the same potential as the electrode, the hot cathode and the second extraction electrode are provided.
A porous conductor is provided between the extraction electrode and the end portion of the electron beam emitted from the second extraction electrode to block the edge region of the electron from the hot cathode. It is characterized in that it has a mask that is formed and is in a floating potential state.

Since the mask is made of a porous conductor and is in a floating potential state, it is negatively charged by the incident collision of electrons from the hot cathode, and the potential of the mask finally becomes the energy of the incident electrons. It reaches the corresponding potential.
As a result, the electrons from the hot cathode are pushed back by the negatively charged mask and cannot pass through the mask. In this way, although the mask is porous, it acts to electrostatically block electrons by charging. Therefore, it is possible to block the end region of the electron from the hot cathode and shape the end of the electron beam extracted from the second extraction electrode.

Moreover, since the mask is porous,
The thermal radiation from the hot cathode can pass through a large number of holes in the mask and reach the second extraction electrode. As a result, even if the mask is provided, the temperature difference generated near the end of the second extraction electrode is reduced, and the deformation of the second extraction electrode is alleviated.

A second aspect of the present invention is an electron source comprising a hot cathode for generating electrons and an extraction electrode for extracting the electrons generated by the hot cathode as an electron beam, wherein an electron source is provided between the hot cathode and the extraction electrode. A mask which is provided and blocks the end region of the electron from the hot cathode to shape the end of the electron beam extracted from the extraction electrode, and which is made of a porous conductor and is in a floating potential state. It is characterized by having.

The second aspect of the present invention relates to the case where the number of extraction electrodes is one, but the operation of the mask is the same as the above-described operation of the first aspect of the invention.

That is, although the mask is porous, it functions to electrostatically shield electrons by charging,
It is possible to block the end region of the electron from the hot cathode and shape the end portion of the electron beam extracted from the extraction electrode.

Moreover, since the mask is porous,
Thermal radiation from the hot cathode can reach the extraction electrode through many holes in the mask. as a result,
Even if the mask is provided, the temperature difference generated near the end of the extraction electrode is reduced, and the deformation of the extraction electrode is alleviated.

[0021]

1 is a schematic sectional view showing an example of an electron source according to the present invention. The same or corresponding parts as those in the examples shown in FIGS. 6 and 7 are designated by the same reference numerals, and the differences from the conventional electron source 6 will be mainly described below.
Otherwise, refer to FIGS. 6 and 7 and their descriptions above.

The electron source 6a shown in FIG. 1 is similar to the conventional electron source 6 shown in FIG. 6 in that it has two extraction electrodes, that is, the first extraction electrode 12 and the second extraction electrode 14 described above. (The same applies to FIGS. 2 and 3).

In the electron source 6a, as an example between the second extraction electrode 14 and the hot cathode 8, a conventional plate-shaped mask 16 is provided between the second extraction electrode 14 and the first extraction electrode 12. As an alternative, the porous mask 26 that blocks the end region of the planar electron 10 from the hot cathode 8 and shapes the end of the electron beam 10a extracted from the second extraction electrode 14 is provided as a second extraction electrode. 14 are provided at both ends in the Y direction (see also FIG. 7). Each mask 26
The second extraction electrode 14 is located above both ends of the second extraction electrode 14 in the Y direction (upstream of the flow of the electrons 10. The same applies hereinafter).

Each mask 26 is made of a porous conductor.
An example thereof is shown in FIG. The mask 26 of this example has a large number of holes 26a which are substantially evenly distributed in the plane. Other than that, each mask 26 may be one in which conductors are arranged in a grid pattern in the vertical and horizontal directions, a mesh shape (mesh shape), or a blind shape only in the vertical or horizontal direction. These are also many holes (openings)
Can be said to be porous.

The size and density of the holes of each mask 26, in other words, the aperture ratio of each mask 26 is determined by the balance between the effect of electrostatically blocking the electrons 10 and the effect of passing the thermal radiation 24. good.

Each mask 26 is electrically insulated from other conductors (for example, the first extraction electrode 12, the second extraction electrode 14, the shield electrode 4, the hot cathode 8 etc.) and is in a floating potential state. . Each mask 26 is supported, for example, by a plurality of insulators 28 as shown in FIG. 5 at a position avoiding the region of the hole 26a.

Since each of the masks 26 is made of a porous conductor and is in a floating potential state, electrons 1 from the hot cathode 8 are generated.
It is negatively charged by the incident collision of 0, and finally the potential of each mask 26 reaches the potential corresponding to the energy of the incident electron 10. As a result, electrons 10 from the hot cathode 8
Will be pushed back by each negatively charged mask 26 and will not be able to pass through each mask 26. Thus, although each mask 26 is porous, it serves to electrostatically block the electrons 10 by charging. Therefore, both end regions of the planar electron 10 from the hot cathode 8 can be blocked and both ends of the electron beam 10 a extracted from the second extraction electrode 14 can be shaped.

Moreover, since each of the masks 26 is porous, the thermal radiation 24 from the hot cathode 8 passes through a large number of holes (for example, holes 26a shown in FIG. 5) of each mask and reaches the second extraction electrode 14. Can be reached As a result, even if each mask 26 is provided, the temperature difference generated near both ends of the second extraction electrode 14 is reduced, and the thermal deformation of the second extraction electrode 14 is mitigated. As a result, it is possible to prevent the distortion of the accelerating electric field from increasing and prevent the uniformity of the dose distribution of the electron beam 10a extracted to the outside through the second extraction electrode 14 from being deteriorated.

If a porous mask whose potential is fixed to a negative potential by a DC power source is used instead of the mask 26, the same effect as that of the mask 26 can be obtained. Because you need a power supply,
It is better to use the mask 26 in the floating potential state as in the present invention because the structure can be simplified.

Each of the masks 26 has the second extraction electrode 14
If it is between the hot cathode 8 and the hot cathode 8, it may be provided in a place other than the example shown in FIG. An example will be described below.

In the electron source 6a shown in FIG. 2, the masks 26 as described above are provided on both end portions of the first extraction electrode 12 in the Y direction on substantially the same plane as the first extraction electrode 12. Each mask 26 is located above both ends of the second extraction electrode 14 in the Y direction. Of course, also in this case, each mask 26 is electrically separated from the first extraction electrode 12 by providing a gap between the mask 26 and the first extraction electrode 12.
It is insulated from the second grade.

In the electron source 6a shown in FIG. 3, the mask 26 as described above is provided between the first extraction electrode 12 and the hot cathode 8. Each mask 26 has Y of the second extraction electrode 14.
It is located above both ends in the direction.

The examples of FIGS. 2 and 3 are similar to the example of FIG.
Although the mask 26 is porous, it functions to electrostatically shield the electrons 10 by charging, and therefore shields both end regions of the electrons 10 from the hot cathode 8 to extract the electron beam 10 a from the second extraction electrode 14. Both ends of can be shaped.

Moreover, since each mask 26 is porous, the thermal radiation 24 from the hot cathode 8 can reach the second extraction electrode 14 through many holes of each mask 26. As a result, even if the mask 26 is provided,
The temperature difference generated near both ends of the second extraction electrode 14 is reduced, and the thermal deformation of the second extraction electrode 14 is mitigated. As a result, it is possible to prevent the distortion of the accelerating electric field from increasing and prevent the uniformity of the dose distribution of the electron beam 10a extracted to the outside through the second extraction electrode 14 from being deteriorated.

In some cases, the number of extraction electrodes may be one instead of two. An example thereof is shown in FIG. In the electron source 6a, the second extraction electrode 14 is provided in the opening of the shield electrode 4, that is, the second extraction electrode 14
An extraction electrode 15 for extracting the electron 10 generated by the hot cathode 8 as an electron beam 10a is provided at a position corresponding to. The planar shape of the extraction electrode 15 is similar to that of the first extraction electrode 12 shown in FIG. 7, for example.

In the electron source 6a, the extraction electrode 1
5 and the hot cathode 8, the planar electrons 10 from the hot cathode 8
The mask 2 as described above, which blocks the end region of the electron beam 10a and shapes the end of the electron beam 10a extracted from the extraction electrode 15.
6 are provided at both ends of the extraction electrode 15 in the Y direction. Each mask 26 is located above both ends of the extraction electrode 15 in the Y direction.

In the example of FIG. 4 as well, as in the examples of FIGS. 1 to 3, although the mask 26 is porous, it functions to electrostatically shield the electrons 10 by charging, so that the mask from the hot cathode 8 is removed. Both ends of the electron beam 10 a extracted from the extraction electrode 15 can be shaped by blocking both end regions of the electron 10.

Moreover, since each mask 26 is porous, the thermal radiation 24 from the hot cathode 8 can reach the extraction electrode 15 through many holes of each mask 26. As a result, even if the mask 26 is provided, the temperature difference generated near both ends of the extraction electrode 15 is reduced, and the thermal deformation of the extraction electrode 15 is mitigated. As a result, it is possible to prevent the above-mentioned distortion of the acceleration electric field from becoming large and prevent the uniformity of the dose distribution of the electron beam 10a extracted to the outside through the extraction electrode 15 from being deteriorated.

When the mask 26 as described above is provided on the downstream side of the second extraction electrode 14 and the extraction electrode 15, the accelerating electric field due to the accelerating voltage Va described above is applied to the mask 26. This disturbs the accelerating electric field, which is not preferable.

In addition, the second extraction electrode 14 and the extraction electrode 1
5 rather than blocking the electron beam 10a after being extracted from No. 5 and accelerated by the accelerating electric field by the mask 26, that is, before the electron beam is accelerated, that is, at the upstream side of the second extraction electrode 14 or the extraction electrode 15 as in the above example. Blocking 10 is easier because the energy of the electron 10 is lower.

Although each of the above examples is an example in which the mask 26 is provided at both ends of the second extraction electrode 14 and the extraction electrode 15 in the Y direction, it is necessary to shape only one side of the extracted electron beam 10a. The mask 26 may be provided on only one side. If it is desired to shape the end portion of the electron beam 10a to be extracted in the X direction, the second extraction electrode 1
The mask 26 as described above may be provided on the ends (both sides or one side) of the extraction electrode 4 and the extraction electrode 15 in the X direction.

[0042]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, although the mask is porous, it functions to electrostatically shield electrons by charging, so that it blocks the end region of the electrons from the hot cathode to 2 The end of the electron beam extracted from the extraction electrode can be shaped.

Moreover, since the mask is porous,
The thermal radiation from the hot cathode can pass through a large number of holes in the mask and reach the second extraction electrode. As a result, even if the mask is provided, the temperature difference generated near the end of the second extraction electrode is reduced, and the deformation of the second extraction electrode is alleviated. As a result, it is possible to prevent the uniformity of the dose distribution of the electron beam extracted to the outside through the second extraction electrode from being deteriorated.

Furthermore, since the mask in the floating potential state is used, the DC power supply is not required, compared with the case where a porous mask in which the potential is fixed to a negative potential by the DC power supply is used. Can be planned.

According to the second aspect of the present invention, although the mask is porous, it functions to electrostatically shield electrons by charging, so that the end regions of the electrons from the hot cathode are shielded and extracted. The end of the electron beam extracted from the electrode can be shaped.

Moreover, since the mask is porous,
Thermal radiation from the hot cathode can reach the extraction electrode through many holes in the mask. as a result,
Even if the mask is provided, the temperature difference generated near the end of the extraction electrode is reduced, and the deformation of the extraction electrode is alleviated. As a result, it is possible to prevent the uniformity of the dose distribution of the electron beam extracted to the outside through the extraction electrode from being deteriorated.

Further, since the mask in the floating potential state is used, the DC power source is unnecessary and the structure is simplified as compared with the case of using the porous mask in which the potential is fixed to the negative potential by the DC power source. Can be planned.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an electron source according to the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the electron source according to the present invention.

FIG. 3 is a schematic sectional view showing another example of the electron source according to the present invention.

FIG. 4 is a schematic sectional view showing still another example of the electron source according to the present invention.

FIG. 5 is a plan view showing an example of the mask in FIGS. 1 to 4 in an enlarged manner.

FIG. 6 is a schematic sectional view showing an example of an electron beam irradiation apparatus including a conventional electron source.

FIG. 7 is a plan view showing a hot cathode, a first extraction electrode and a mask.

[Explanation of symbols]

6a electron source 8 hot cathode 10 electronic 10a electron beam 12 First extraction electrode 14 Second extraction electrode 15 Extraction electrode 24 Thermal radiation 26 masks

Claims (2)

[Claims] 1. A hot cathode for generating electrons, and two extraction electrodes for drawing out the electrons generated by the hot cathode as an electron beam, the first extraction electrode on the upstream side and the downstream side of the same potential as the extraction electrode. In an electron source provided with a second extraction electrode, the electron is extracted from the second extraction electrode by being provided between the hot cathode and the second extraction electrode and blocking an end region of electrons from the hot cathode. An electron source for shaping an end portion of an electron beam, comprising a mask made of a porous conductor and in a floating potential state. 2. An electron source comprising a hot cathode for generating electrons and an extraction electrode for extracting the electrons generated by the hot cathode as an electron beam, the electron source being provided between the hot cathode and the extraction electrode. An end region of electrons emitted from the hot cathode is blocked to shape an end of an electron beam extracted from the extraction electrode, and a mask made of a porous conductor and in a floating potential state is provided. An electron source characterized by the above.