JP2005337915A - Electron source for electron beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent uniformity in a Y-directional electron beam distribution from getting worse caused by thermal deformation of an extraction electrode piece constituting an extraction electrode in the most downstream side. <P>SOLUTION: This electron source concerned in the present invention has one stage or more of the extraction electrodes along an extraction direction Z of an electron beam 14. The extraction electrode 12a in the most downstream side out of them is divided with clearances 26 Y-directionally in the plurality of extraction electrode pieces 22. Bent parts 30 with an end part bent toward an opposite direction of the electron beam extraction direction Z are formed respectively in the end parts of clearance 26 sides in the respective extraction electrode pieces 22 constituting the extraction electrode 12a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an electron source used in a non-scanning type (also called area type) electron beam irradiation apparatus, and has one or more extraction electrodes for extracting electrons emitted from a filament as an electron beam. The extraction electrode on the most downstream side in the line extraction direction relates to an electron source having a split structure, and more specifically, to a means for preventing deterioration in uniformity of electron dose distribution due to thermal deformation or the like of the extraction electrode on the most downstream side. .

  An example of a non-scanning electron beam irradiation apparatus provided with this type of electron source is shown in FIG. An electron beam irradiation apparatus having a structure substantially similar to this is described in Patent Document 1.

Japanese Patent Laying-Open No. 2003-4898 (paragraphs 0020, 0021, FIGS. 1 and 2)

  The electron beam irradiation apparatus shown in FIG. 7 arranges a shield electrode 4 for reducing electric field concentration that has a long cylindrical shape in the Y direction in a cylindrical vacuum vessel 2 that is long in the front and back direction (Y direction). It has a structure in which an electron source 6 long in the Y direction is arranged.

  The electron source 6 emits electrons and has a plurality of linear (also referred to as rod-shaped) filaments 8 extending in the X direction, and these are in the Y direction perpendicular to the X direction. They are arranged parallel to each other and on the same plane with a predetermined interval (see also FIG. 9). The Y direction in which the filaments 8 are arranged is also called the irradiation width direction of the electron beam 14. The X direction is also referred to as an irradiation object transport direction.

  The electron source 6 further includes porous extraction electrodes 10 and 12 that are arranged in parallel to the plane on which the filaments 8 are arranged and draw out electrons emitted from the filaments 8 as electron beams 14. In this example, the extraction electrodes 10 and 12 are arranged in two stages at intervals in the electron beam extraction direction Z perpendicular to the X direction and the Y direction. The two extraction electrodes 10 and 12 and the shield electrode 4 are electrically connected to each other at the same potential.

  Both extraction electrodes 10 and 12 each have a large number of electron extraction holes (see, for example, the electron extraction hole 24 in FIG. 8). The shape of the electron extraction hole is not limited to a circular shape as shown in FIG. 8 or the like, and may be another shape such as a square (the same applies to the embodiment of FIG. 1 described later).

Although the extraction electrode may be one stage (one sheet), if two stages (two sheets) of extraction electrodes 10 and 12 are provided as in this example, the radiant heat from the filament 8 is downstream by the upstream extraction electrode 10. It is possible to reduce the thermal deformation of the extraction electrode 12 by reducing the reaching to the extraction electrode 12 on the side, and to accelerate the acceleration electric field due to the acceleration voltage V _A described later by the extraction electrode 12 on the downstream side. Since it is possible to prevent the electric field from reaching the extraction electrode 10 which is easily thermally deformed on the upstream side, the uniformity of the dose distribution of the electron beam 14 can be improved. For the same purpose, there are cases where three or more extraction electrodes having the same potential are provided.

  A reflector electrode 16 may be provided between the upper part of each filament 8 and the shield electrode 4 so as to push back the electrons emitted from each filament 8 to the extraction electrodes 10 and 12 as shown in FIG. good. In this example, each filament 8 is supported by being electrically insulated from the reflector electrode 16 by a support means (not shown). The extraction electrode 10 is supported from the reflector electrode 16 via a plurality of insulating columns 18. The extraction electrode 12 is attached to the opening of the shield electrode 4, and the peripheral edge thereof is fixed to the shield electrode 4.

The shield electrode 4 and the extraction electrodes 10 and 12 are connected to each other at the same potential as described above, and between them and each filament 8, the filament 8 side is negative, and the direct current for extracting the electron beam 14 is used. The extraction voltage V _E is applied from an extraction power source (not shown). Further, a window foil 20 having the same potential as that of the vacuum container 2 is provided at the opening of the vacuum container 2, and the extraction electrode 12 side is negative between these window foils 20 and the electron beam 14. _A DC acceleration voltage V _A for acceleration is applied from an acceleration power source (not shown).

  The electron beam 14 drawn out and accelerated from the electron source 6 in this way passes through the window foil 20 that separates the atmosphere inside and outside the vacuum vessel 2 and is taken out of the vacuum vessel 2 to be irradiated ( (Not shown) and subjected to a process such as reforming.

  By the way, even if the extraction electrodes are arranged in two stages as described above, the extraction electrode 12 on the downstream side is still heated by the heat from the filament 8 and the electron beam 14 that has hit the portions other than the electron extraction holes 24. . In order to reduce the length in the Y direction and reduce the thermal deformation of the extraction electrode 12 due to the heating, the extraction electrode 12 has gaps between the plurality of extraction electrode pieces 22 in the Y direction, as shown in FIG. 26 is divided. A gap 26 between the adjacent extraction electrode pieces 22 in the divided portion has a width that can absorb the thermal expansion of the extraction electrode piece 22 in the Y direction. However, electrically, all the extraction electrode pieces 22 are connected to each other at the same potential by a wiring (not shown), and the extraction electrode 12 functions as one electrode as a whole. The number of divisions, that is, the number of extraction electrode pieces 22 is not limited to three as in the illustrated example.

  The extraction electrode 10 on the upstream side is also heated more strongly than the extraction electrode 12 by heat from the filament 8 and electrons hitting a portion other than the electron extraction hole. In order to reduce the thermal deformation caused by this, normally, like the extraction electrode 12, a plurality of extraction electrode pieces are provided with gaps in the Y direction. In many cases, the number of divisions is larger than that of the extraction electrode 12.

Paying attention to the extraction electrode 12 on the downstream side, more specifically, on the downstream side of the extraction electrode 12, more specifically between the extraction electrode 12 and the window foil 20 facing it, due to the acceleration voltage V _A. An acceleration electric field is formed. An example of the equipotential surface 28 of this acceleration electric field is shown in FIG. In FIG. 9, the electron extraction holes of the extraction electrodes 10 and 12 are not shown (the same applies to FIGS. 3 and 5).

  When the extraction electrode 12 is divided into a plurality of extraction electrode pieces 22 as described above, the length in the Y direction is shortened and thermal deformation is reduced as compared with the case where the extraction electrode pieces 22 are integrated, but each extraction electrode piece 22 is still heated. Cause thermal deformation. In particular, the end portion on the gap 26 side of each extraction electrode piece 22 is a free end that is not fixed to another object, and thus tends to be thermally deformed. An example of this state is shown by a two-dot chain line 22a in FIG. Here, the example which carried out the heat deformation in the convex shape downstream is shown. The direction and magnitude of this thermal deformation usually differ from each other in the situation in which each extraction electrode piece 22 is placed, and therefore usually differs from one extraction electrode piece 22 to another. As a result, a step occurs between adjacent extraction electrode pieces 22. FIG. 9 shows an enlarged cross section of an example.

  When the step is generated as described above, the acceleration electric field (see the equipotential surface 28) in the vicinity of the gap 26 between the adjacent extraction electrode pieces 22 is disturbed and becomes non-uniform as shown in the example shown in FIG. A part of the electron beam 14 extracted from 12 and accelerated is bent, for example, in the Y direction as shown in the example, and the acceleration direction of the electron beam 14 becomes non-uniform. As a result, the dose of the electron beam 14 in the Y direction The uniformity of distribution deteriorates.

  The above-described problems exist even when the number of extraction electrodes is one, when the extraction electrode is two, as in the above example, or when there are three or more. That is, it exists when the most downstream extraction electrode of one or more extraction electrodes is divided as described above. This is because, regardless of the number of extraction electrodes, the acceleration electric field is formed immediately downstream of the most downstream extraction electrode and is disturbed by the step. In the case of one stage, the one-stage extraction electrode is also the most downstream extraction electrode (in other words, it can be regarded as the most downstream extraction electrode). In the case of two stages, the downstream extraction electrode 12 It is the extraction electrode on the most downstream side. It can be said that the most downstream extraction electrode is an extraction electrode facing the window foil 20. Further, the most downstream extraction electrode in the case of a plurality of stages is also referred to as an acceleration electrode because an acceleration electric field is applied as described above.

  Accordingly, the main object of the present invention is to prevent the deterioration of the uniformity of the electron dose distribution in the Y direction due to the thermal deformation of the extraction electrode piece constituting the most downstream extraction electrode.

  In the electron source according to the present invention, a bent portion obtained by bending the end portion in the direction opposite to the electron beam extraction direction is formed at the end portion on the gap side of each extraction electrode piece constituting the most downstream extraction electrode. It is characterized by forming each.

  According to the above configuration, since the sectional modulus of the extraction electrode piece is increased by the bent portion and the mechanical strength is increased, the thermal deformation of each extraction electrode piece is reduced, and particularly on the gap side of each extraction electrode piece. It is possible to reduce the thermal deformation of the end portion and prevent a step from being generated between adjacent extraction electrode pieces.

  A plurality of conductive rods that are fixed to one bent portion and extend through the holes of the other bent portion so as to be stretchable in the Y direction between adjacent bent portions of the extraction electrode piece, They may be provided side by side in the X direction.

  According to the first aspect of the present invention, since the sectional modulus of the extraction electrode piece is increased by the bent portion and the mechanical strength is increased, the thermal deformation of each extraction electrode piece is reduced, and in particular each extraction electrode piece. It is possible to reduce the thermal deformation of the end portion on the gap side and to prevent a step from occurring between adjacent extraction electrode pieces. As a result, it is possible to prevent the accelerating electric field formed immediately downstream of the most downstream extraction electrode from being disturbed and non-uniform, thereby preventing deterioration in the uniformity of the electron dose distribution in the Y direction. it can.

  According to the second aspect of the present invention, since the adjacent extraction electrode pieces are mechanically connected by the conductive rods so as not to deviate from each other in the vertical direction, there is a step between the adjacent extraction electrode pieces. Can be prevented more reliably. As a result, it is possible to more reliably prevent the deterioration of the uniformity of the electron dose distribution in the Y direction due to the generation of the step.

  In addition, since the accelerating electric field can be prevented from entering the gap between the extraction electrode pieces by the conductive rod, the accelerating electric field enters the gap and the accelerating electric field is disturbed and becomes non-uniform. It is possible to prevent the uniformity of the electron dose distribution from deteriorating.

  Therefore, the above two effects are combined, and the deterioration of the uniformity of the electron dose distribution in the Y direction can be prevented more reliably.

  FIG. 1 is a perspective view showing an example of the most downstream extraction electrode constituting the electron source according to the present invention. FIG. 2 is a partially enlarged perspective view of the extraction electrode of FIG. Portions that are the same as or correspond to those in the conventional example shown in FIG. 8 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. Further, the configuration of the electron source 6 and the configuration of the entire electron beam irradiation apparatus other than the extraction electrode 12a replaced with the extraction electrode 12a described below are the same as those in FIG. Here, redundant description is omitted.

  The extraction electrode 12a shown in FIGS. 1 and 2 is an alternative to the extraction electrode 12, and the end of each extraction electrode piece 22 constituting the extraction electrode 12a is connected to the end on the gap 26 side. The bent portions 30 are formed by bending the portions in the L-shaped cross section in the direction opposite to the electron beam extraction direction Z. Each bent portion 30 extends along the gap 26 in parallel with the X direction.

  As shown in the example shown in FIG. 1, it is preferable that each bent portion 30 is provided continuously from one end to the other end in the X direction of the extraction electrode piece 22 because the processing is simple and the strength is maximized. However, it is not necessarily limited to that. A part may be omitted if necessary.

  The bent portion 30 is formed by bending the end portion of the extraction electrode piece 22 in the direction opposite to the electron beam extraction direction Z. The bent portion 30 is formed immediately downstream of the extraction electrode 12a. This is to prevent the acceleration electric field from being disturbed. Even if the extraction electrode 10 exists on the upstream side of the extraction electrode 12a, both the electrodes 10 and 12a are at the same potential as described above. Does not happen.

  Note that the bent portion 30 may not be provided at the end portion in the Y direction that does not face the gap 26 of the extraction electrode piece 22, and is not provided in the example of FIG. This is because the end is fixed to the shield electrode 4 as described above, for example.

  According to the above configuration, the bending modulus 30 increases the sectional modulus of the extraction electrode piece 22 and increases the mechanical strength. Therefore, the thermal deformation of each extraction electrode piece 22 is reduced, and in particular, The thermal deformation at the end on the gap 26 side can be reduced to prevent a step between adjacent extraction electrode pieces 22. As a result, it is possible to prevent the accelerating electric field formed immediately downstream of the extraction electrode 12a from being disturbed and non-uniform, thereby preventing deterioration of the uniformity of the dose distribution of the electron beam 14 in the Y direction. be able to.

  This extraction electrode 12a is an example in the case of the extraction electrode on the downstream side (that is, the most downstream side) of the two-stage extraction electrode, similarly to the extraction electrode 12, but as described above, the extraction electrode has one stage. In this case, since the extraction electrode is also the extraction electrode on the most downstream side, the bent portion 30 as described above may be provided in the extraction electrode piece constituting the extraction electrode. When the number of extraction electrodes is three or more, the bent portion 30 as described above may be provided on the extraction electrode piece constituting the most downstream extraction electrode.

  Referring to FIG. 2, the width a of each gap 26 is set to a size capable of absorbing the thermal expansion in the Y direction of the extraction electrode piece 22 as described above. The height b of each bent portion 30 on both sides is preferably large to some extent from the viewpoint of improving mechanical strength. However, when the extraction electrode has one stage, that is, when there is no extraction electrode 10 and the extraction electrode 12a is in the first stage and the filament 8 is positioned immediately above, it is preferable that a ≧ b.

  This is because the filaments 8 are arranged side by side at a predetermined interval as described above (see, for example, FIG. 3), and most of the electrons emitted from each filament 8 are curved to form a first-stage extraction electrode (this In such a case, if a ≧ b is set, the bent portion 30 is unlikely to become an obstacle when the electrons are drawn through the gap 26, and the gap 26 is This is because it can be used effectively by drawing. When there are a plurality of extraction electrodes, the electrons entering the most downstream extraction electrode 12a are substantially parallel to the electron beam extraction direction Z, and therefore it is not always necessary to satisfy a ≧ b.

  By the way, in FIG. 9 and the description thereof, it is ignored that the acceleration electric field enters each gap 26. However, in detail, as in the example shown in FIG. 3, regardless of the presence or absence of a step in the extraction electrode 12a. The acceleration electric field enters each gap 26, the acceleration electric field in the vicinity of each gap 26 becomes disordered and becomes non-uniform, and the electron beam 14 drawn out and accelerated from the vicinity of the gap 26 is bent, which is also the Y direction of the electron beam 14. It becomes a factor which deteriorates the uniformity of the dose distribution in. Therefore, means capable of solving such a problem will be described next.

  In the extraction electrode 12a shown in FIG. 4, between the adjacent bending parts 30 of each extraction electrode piece 22, it fixes to one bending part 30 (right side in FIG. 4), and the other (left side in FIG. 4). ), A plurality of conductive rods 32 penetrating through the holes 34 provided in the bent portion 30 in the Y direction are provided side by side in the X direction.

  The plurality of conductive bars 32 are preferably arranged at equal intervals in the X direction. If it does so, the penetration | inhibition effect | action to the clearance gap 26 of the acceleration electric field mentioned later can be made uniform. Each conductive rod 32 is longer than the width a of the gap 26 (see FIG. 2). This is to cope with contraction of the gap 26 due to thermal expansion of the extraction electrode piece 22. The material of each conductive rod 32 is preferably the same material as that of the extraction electrode piece 22 including the bent portion 30. This is because the coefficient of thermal expansion is the same as that of the extraction electrode piece 22. For example, nickel, stainless steel, molybdenum and the like.

  Each hole 34 is provided at a position corresponding to each conductive rod 32, and the size thereof is preferably reduced within a range in which expansion and contraction of the conductive rod 32 in the Y direction can be allowed. By doing so, the gap between the outer peripheral portion of the hole 34 and the conductive rod 32 becomes small, so that the effect of preventing the later-described step generation can be further enhanced.

  When a plurality of conductive bars 32 as described above are provided, each conductive bar 32 is fixed to one bent portion 30 and has the same potential as the extraction electrode piece 22. As an example, the accelerating electric field can be prevented from entering each gap 26. As a result, an accelerating electric field enters each gap 26 and the accelerating electric field is disturbed and becomes non-uniform. This can prevent the uniformity of the dose distribution in the Y direction of the electron beam 14 from deteriorating.

  Moreover, since the adjacent extraction electrode pieces 22 are mechanically connected to each other by the conductive rod 32 so as not to be displaced in the vertical direction, it is more sure that a step is generated between the adjacent extraction electrode pieces 22. Can be prevented. As a result, it is possible to more reliably prevent the deterioration of the uniformity of the dose distribution in the Y direction of the electron beam 14 due to the generation of the step.

  Therefore, the above two effects are combined, and the deterioration of the uniformity of the dose distribution in the Y direction of the electron beam 14 can be prevented more reliably.

  Each conductive bar 32 is fixed to one bent portion 30 and penetrates the hole 34 of the other bent portion 30 in the Y direction so that it can expand and contract in the Y direction. Can be tolerated. Therefore, the original effect (that is, reduction of thermal deformation of the extraction electrode 12a) obtained by dividing the extraction electrode 12a into the plurality of extraction electrode pieces 22 in the Y direction is not reduced.

  In the example of FIG. 4, all the conductive bars 32 are fixed to the same bent portion 30 and penetrated through the hole 34 of the opposite bent portion 30, but as in the example shown in FIG. 6, The fixing of the conductive bars 32 and the penetration of the holes 34 may be alternated. Even if it does so, there exists an effect similar to the case of the example of FIG.

It is a perspective view which shows an example of the extraction electrode of the most downstream side which comprises the electron source which concerns on this invention. It is a perspective view which expands and shows partially the extraction electrode of FIG. It is a figure which shows the example of the track | orbit of an electron beam at the time of using the extraction electrode of FIG. It is a perspective view which expands and partially shows the other example of the extraction electrode of the most downstream side which comprises the electron source which concerns on this invention. It is a figure which shows the example of the track | orbit of an electron beam at the time of using the extraction electrode of FIG. It is a perspective view which expands and partially shows other example of the extraction electrode of the most downstream side which comprises the electron source which concerns on this invention. It is a schematic sectional drawing which shows an example of a non-scanning type electron beam irradiation apparatus provided with an electron source. It is a perspective view which shows an example of the extraction electrode of the downstream which comprises the conventional electron source. It is a figure which shows the example of the track | orbit of an electron beam at the time of using the extraction electrode of FIG.

Explanation of symbols

6 Electron source 8 Filament 10 Extraction electrode 12a Extraction electrode (the most downstream extraction electrode)
14 Electron beam 22 Extraction electrode piece 26 Gap 30 Bending part 32 Conductive rod 34 Hole

Claims (2)

Each of them extends in the X direction and emits electrons, and is arranged along the filament with a plurality of filaments arranged on the same plane and arranged in the Y direction orthogonal to the X direction. And an extraction electrode for extracting electrons emitted from the filament as an electron beam, and the extraction electrodes having the same potential are arranged in one or more stages in the electron beam extraction direction. In the electron source in which the most downstream extraction electrode is divided in the Y direction by providing a plurality of extraction electrode pieces with gaps,
Bending portions are formed by bending the end portions in the direction opposite to the electron beam extraction direction at the end portions on the gap side of the extraction electrode pieces constituting the most downstream extraction electrode. An electron source for an electron beam irradiation apparatus.   A plurality of conductive rods that are fixed to one bent portion and extend through the holes of the other bent portion so as to be stretchable in the Y direction between adjacent bent portions of the extraction electrode piece, 2. The electron source for an electron beam irradiation apparatus according to claim 1, wherein the electron source is arranged in the X direction.

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