JP6194178B2 - Electron gun and electron beam emission method - Google Patents

Description

The present invention relates to an electron gun and an electron beam emission method , and more particularly to an electron gun having a structure capable of extending the life of a filament and an electron beam emission method .

  Conventionally, the evaporation material such as metal contained in the crucible in the vacuum chamber is irradiated with an electron beam to evaporate the evaporation material, or the accelerated electron beam is collided with a target such as metal and welded to the target. An electron gun is used for processing such as the above. Such an electron gun is known from Patent Document 1, for example. This includes a filament that emits thermoelectrons, an opening surrounding the filament and facing the filament, converging the emitted thermoelectrons, and a Wenelt orthogonal to the plane containing the Wenelt opening. And an anode for accelerating the thermoelectrons with an opening that allows the passage of the thermoelectrons in front of the Wehnelt. The anode and Wehnelt are usually arranged so that an axis (hole axis) extending in the front-rear direction through the center of the opening is positioned on the coaxial line (see Patent Document 1, for example, FIG. 1).

  Here, the case where the electron gun having the above-described configuration is applied to a vacuum deposition apparatus will be described as an example. During the deposition, the vacuum chamber is vaporized from an evaporation material and corresponds to the pressure (vacuum degree) in the vacuum chamber. Gas remains, and the electron beam collides with these vaporized substances and residual gas to ionize them to generate cations of the vaporized substance and residual gas. The generated cations are accelerated toward the filament as the cathode, and the accelerated cations are converged by the electric field lens formed by Wehnelt and the anode and collide with a part of the filament. Then, the filament is locally cut and disconnected.

  When the anode and Wehnelt are arranged so that the hole axis of the opening is located on the same axis as in the conventional example, a self-induction electric field generated in the space between the Wehnelt and the anode when an acceleration voltage is applied. Becomes a profile symmetric with respect to the hole axis, and the cation collides through a trajectory along the hole axis (that is, from a direction perpendicular to the plane direction). And if it cuts for the diameter of the wire which comprises a filament, it will break, and there exists a problem that the lifetime of a filament is short. In such a case, it is conceivable to form an electric field lens in which the anode is arranged only on one side of the opening in front of the Wehnelt opening so that cations do not concentrate on a part of the filament (so-called asymmetric type electrons). Gun), such an asymmetric type has a problem that the electron beam extraction efficiency is inferior.

JP 2011-119140 A

In view of the above points, the present invention provides an electron gun having a structure capable of extending the life of a filament without impairing the function of efficiently extracting an electron beam, and an electron beam emission method. It is to be an issue.

In order to solve the above-mentioned problems, a filament that emits thermoelectrons, a Wenelt that surrounds the filament and has an opening facing the filament, and converges the emitted thermoelectrons, and a plane that includes the Wenelt opening. And an anode to which an acceleration voltage is applied, having an opening that allows the passage of thermoelectrons in front of the Wehnelt, which is perpendicular to the direction in which thermionic electrons are emitted toward the Wehnelt opening. The electron gun has the following features. That is, in the present invention, a filament made of a metal wire wound in a coil shape is used, and the Wehnelt opening and the anode opening facing the outer peripheral surface of the filament are elongated holes in the filament bus direction, When an acceleration voltage is applied to the anode, the self-induced electric field generated in the space between Wehnelt and the anode shifts toward the inner periphery of the anode opening, so that the hole axis passing through the anode opening center and the Wehnelt opening center Was offset in the direction perpendicular to the generatrix direction within a range of 0.1 to 2.5 mm within the plane including the Wehnelt opening. Further, in order to solve the above-mentioned problems, the present invention allows the filament to be energized in a vacuum to emit thermoelectrons, and the emitted thermoelectrons are converged by Wehnelt provided with an opening facing the filament. In an electron beam emission method in which an accelerated voltage is applied to an anode provided with an opening to accelerate the focused thermoelectrons to be emitted into a vacuum, the electron beam is emitted during the electron beam emission. The self-induced electric field generated in the space between them is shifted toward the inner periphery of the anode opening, and the positive ions generated in front of the anode with the emission of this electron beam are directed to the hole axis passing through the center of the anode opening. The method includes a step of colliding with a filament from an inclined direction.

  According to the above, for example, when each of the electron guns described above is applied to a vacuum deposition apparatus, the cations generated by the electron beam colliding with the evaporated substance or residual gas in the vacuum chamber during the deposition are accelerated toward the filament. However, the self-induction electric field may be generated by offsetting the Wehnelt opening and the anode opening in the plane direction or by locally changing the distance in the front-rear direction to the periphery of the anode opening with respect to the Wehnelt opening. Is shifted to the inner peripheral edge side of the anode opening, so that cations collide with the filament from a direction inclined with respect to an axis extending in the front-rear direction through the center of the Wehnelt opening. The time until disconnection can be lengthened as compared with the above. In this case, since the anode provided with the opening is disposed in front of the Wehnelt opening, the function of efficiently extracting the electron beam is not impaired, and the life of the filament can be increased.

  In the case where the filament is a metal wire wound in a coil shape, and the Wehnelt opening facing the filament and the anode opening are formed by long holes, the offset direction is set to the both openings. If the direction is orthogonal to the longitudinal direction, a configuration capable of extending the life of the filament can be realized without changing the components of the existing electron gun.

1 is a schematic cross-sectional view illustrating a configuration of an electron gun according to an embodiment of the present invention. The schematic front view of the electron gun shown in FIG. The figure explaining the positional relationship of the opening of the anode with respect to the opening of Wehnelt, and the trajectory of the cation with respect to a filament with the electron gun which concerns on embodiment of this invention. The figure explaining the positional relationship of the opening of the anode with respect to the opening of Wehnelt, and the orbit of the cation with respect to a filament with the electron gun which concerns on a prior art example. (A) And (b) is a figure explaining the positional relationship of the opening of an anode with respect to the opening of Wehnelt with the electron gun which concerns on a modification.

  Hereinafter, referring to the drawings, the present invention is applied to an example in which the evaporation material such as a metal housed in a crucible in a vacuum chamber outside the drawing is irradiated with an electron beam to evaporate the evaporation material. The form of the electron gun will be described. In the following, terms indicating directions such as “up” and “down” are based on FIG.

  1 to 3, EG is an electron gun according to an embodiment of the present invention. The electron gun EG includes a filament 1 that emits thermoelectrons, an opening 21, a Wehnelt 2 that converges emitted thermoelectrons, and a Wehnelt 2 that is orthogonal to the plane including the opening 21 of the Wehnelt 2. A direction in which thermionic electrons are emitted toward the opening 21 is the front (right side in FIG. 1), and an anode 3 that has an opening 31 that allows the passage of thermionic electrons in front of the Wehnelt 2 and accelerates thermionic electrons. Prepare.

  As the filament 1, for example, a tungsten wire in the range of φ0.5 mm to 1.0 mm has an inner diameter in the range of φ2 mm to φ5 mm, and the total length is in the range of 2.0 mm to 30.0 mm. A coil wound is used. Then, both free ends of the filament 1 are attached to a support plate 5 that stands on a metal base 4 and supports the Wehnelt 2. In this case, the free end (upper side) of one filament 1 is inserted through, for example, a hole 2a formed in the support plate 5 in order to electrically insulate. Further, both free ends of the filament 1 are connected to a power source E1, and are energized by the power source E1 to become red hot and emit thermoelectrons. In addition, the form of the filament 1 is not limited to this, The thing which bent the wire simply in the shape of a U character, and the thing wound in the spiral shape can be used. In FIG. 1, E2 is another power source for applying the acceleration voltage. Since the power sources E1 and E2 have a known structure, detailed description thereof is omitted here.

  The Wehnelt 2 is composed of a plate-like member 2a supported via a cylindrical member 51 provided on the front surface of the support plate 5, and a space surrounding the filament 1 with the plate-like member 2a, the support plate 5 and the cylindrical member 51. Is defined. And the oval hole as the opening 21 which the filament 1 faces to the plate-shaped member 2a is opened. In this case, the length of the opening 21 in the longitudinal direction is set longer than the entire length of the filament 1, while the anode 3 held at the ground potential is constituted by a plate-like member supported by the pedestal 4. In addition, an oval long hole is formed as an opening 31 through which the filament 1 faces through the opening 21. In this case, the inner peripheral edge of the opening 31 is formed in a tapered surface that widens toward the front. The inner peripheral edge portion of the opening 31 is not limited to a tapered one. Then, the filament 1 is energized in vacuum to emit red hot electrons, and is accelerated by the anode 3 while being focused by the Wehnelt 2 and bent 180 ° by a magnetic field of an electromagnetic coil (not shown). The evaporating material 7 accommodated in the grounded crucible 6 is irradiated with the electron beam EB.

Here, while the evaporation material 7 accommodated in the crucible 6 is irradiated with the electron beam EB and evaporated, positive ions of the evaporation substance and residual gas in the vacuum chamber are generated, and the generated positive ions are used as the cathode. Accelerated toward the filament 1, the accelerated positive ions are converged by an electric field lens formed by the Wehnelt 2 and the anode 3 and concentrated and collide with a part of the filament 1. At this time, in the electron gun 100 of the conventional example, as shown in FIG. 4, it extends in the front-rear direction (left-right direction in FIG. 4) through the centers of the opening 111 of the Wehnelt 110 and the opening 121 of the anode 120. Since the Wehnelt 110 and the anode 120 are arranged so that the hole axes HA ₁₀ and HA ₂₀ are positioned on the same axis, the acceleration voltage is applied by the power source E2 in the space between the Wehnelt 2 and the anode 3. The generated self-inducing electric field Ef has a symmetric profile with respect to both hole axes HA ₁₀ and HA ₂₀ , and under the influence of the self-inducing electric field Ef, cations are trajectories along the hole axis HAc, that is, Wehnelt 110 and anode. 120 collides with the filament 130 from a direction perpendicular to the plane direction including the openings 111 and 121 with the 120 (that is, the filament 130 When the cations collide with the electron beam EB emitted through the openings 121 and 111 along the trajectory and return to the filament 1 side), the wire breaks when the wire 130 constituting the filament 130 is cut by the diameter. End up.

In this embodiment, referring again to FIG. 3, the opening 21 of the Wehnelt 2 and the opening 31 of the anode 3 are offset in the plane direction, and the self-induction electric field Ef is the inner peripheral edge (lower longitudinal length) of the opening 31 of the anode 3. It was configured to have a profile shifted to the edge of the direction) side. That is, by offsetting the attachment position of the anode 3 to the base 4 downward, the opening 31 of the anode 3 is offset downward in the range of 0.1 to 2.5 mm with respect to the opening 21 of Wehnelt 2, The hole axis HA ₁ extends in the front-rear direction (left-right direction in FIG. 3) through the center of the opening 21 of the Wehnelt 2 and extends in the front-rear direction (left-right direction in FIG. 3) through the center of the opening 31 of the anode 3. The hole axis HA ₂ was offset in the vertical direction. Thereby, positive ions collide with the filament 1 from the direction inclined with respect to the hole axes HA ₁ and HA ₂ . As a result, it is possible to lengthen the time until disconnection as compared with the conventional example. In this case, since the anode 3 having the opening 31 is disposed in front of the opening 21 of the Wehnelt 2, the function of efficiently extracting the electron beam EB is not impaired, and the life of the filament 1 is increased. Can be planned.

  Next, in order to confirm the above effect, the following experiment was performed using the electron gun EG. In this case, the opening 31 of the anode 3 is offset 0.5 mm downward with respect to the opening 21 of the Wehnelt 2 (invention product), and the opening 31 of the anode 3 is not offset with respect to the opening 21 of the Wehnelt 2 (Conventional product). Then, the inside of the vacuum chamber was placed in a vacuum atmosphere, and the filament was energized with an output of 10 kV and 300 mA, and the time until disconnection was measured between the inventive product and the conventional product. According to this, the conventional product was disconnected in about 9 hours, but according to the invention, it was confirmed that the filament was not disconnected even after 30 hours had passed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above embodiment, an example in which the opening 31 of the anode 3 is offset with respect to the opening 21 of the Wehnelt 2 with a simple structure using existing components has been described as an example. However, the cations are the hole axes HA ₁ , HA. If it can be made to collide with the filament 1 from the direction inclined with respect to ₂ , the form will not be ask | required. For example, in the modification of the second mode shown in FIG. 5A, the distances D1 and D2 in the front-rear direction to the peripheral portions of the openings 310a and 310b of the anode 3 with respect to the openings 21 of the Wehnelt 2 are locally changed. The self-induced electric field Ef has a profile shifted toward the inner peripheral edge of the opening 31 of the anode 3 at a position where the distance D2 in the front-rear direction is different, so that the cation collides with the filament 1 from the inclined direction. Yes. Further, in another modification shown in FIG. 5B, the cations are inclined by forming the inclinations of the inner peripheral edge portions 320a and 320b of the opening 320 of the anode 3 so as to be locally reverse tapered surfaces. It collides with the filament 1 from the direction made.

  EB ... Electron gun, Ef ... Self-induction electric field, 1 ... Filament, 2 ... Wehnelt, 21 ... Wehnelt opening, 3 ... Anode, 31 ... Anode opening.

Claims (2)

A Wenelt that has a filament that emits thermoelectrons, an opening that surrounds and faces the filament, and focuses the emitted thermoelectrons, and toward the Wenelt opening that is orthogonal to the plane that includes the Wenelt opening. An electron gun including an anode for accelerating thermoelectrons having an opening that allows the passage of thermoelectrons in front of Wehnelt in front of the direction in which thermionic electrons are emitted;
In a filament, a metal wire wound in a coil shape, and a Wehnelt opening facing the outer peripheral surface of the filament and an anode opening are elongated holes in the filament's generatrix direction,
When an acceleration voltage is applied to the anode, the self-induced electric field generated in the space between Wehnelt and the anode shifts toward the inner periphery of the anode opening, so that the hole axis passing through the anode opening center and the Wehnelt opening center An electron gun characterized by being offset in a range of 0.1 to 2.5 mm in a direction perpendicular to the generatrix direction in a plane including a Wehnelt opening with a hole axis passing through The filament is energized in vacuum to emit thermoelectrons, and the emitted thermoelectrons are converged by a Wehnelt provided with an opening facing the filament, and an acceleration voltage is applied to the anode provided with the opening facing the filament. In the electron beam emission method in which the focused thermoelectrons are accelerated and emitted into a vacuum,
During the emission of the electron beam, the self-induced electric field generated in the space between Wehnelt and the anode is shifted to the inner peripheral edge side of the opening of the anode, and the positive ions generated in front of the anode are generated as the electron beam is emitted. A method of emitting an electron beam comprising the step of colliding with a filament from a direction inclined with respect to a hole axis passing through an opening center of an anode.

Images