WO2011068101A1 - Filament supporting method, electron gun, and processing apparatus - Google Patents

Abstract

Disclosed is an electron gun including a filament (12) to which electricity is applied for heating a cathode electrode (13) with thermal electrons, and two filament supports (42, 43) for supporting the filament (12). The filament supports (42, 43) have front ends (42c, 43c) respectively onto which the filament (12) is installed, and base ends to be fixed to a base (41). The filament supports (42, 43) make the front ends (42c, 43c) thereof be displaced respectively, in accordance with elongation that takes place at the filament (12) due to the applying of electricity. Electron beam output can be stabilized with this configuration.

Description

Filament support method, electron gun, and processing apparatus

The present invention relates to a method for supporting a filament of an electron gun used as a heating apparatus such as a melting furnace or a vapor deposition apparatus, an electron gun, and a processing apparatus.

Conventionally, an electron gun is used as a heating source for an evaporation apparatus, a melting furnace, a heat treatment furnace, and the like because an energy source is electrons and an electron beam can be easily oscillated and deflected. A piercing electron gun is known as one of electron guns that emit an electron beam (see, for example, Patent Document 1 and Patent Document 2). In general, when an electron beam is emitted from this pierce-type electron gun, first, thermoelectrons are emitted from a filament that has generated heat due to Joule heat of an alternating current. Thermal electrons are emitted from the cathode electrode to which a positive voltage is applied. The thermoelectrons emitted from the cathode electrode are focused by an electric field formed by a Wehnelt electrode having the same potential as the cathode electrode and an anode electrode to which a positive voltage is applied to the cathode electrode and the Wehnelt electrode. And emitted as an electron beam.

Japanese Patent Laid-Open No. 7-258832 JP 2005-268177 A

An alternating current is continuously supplied to the filament used as a heating source of the cathode electrode during the period when the electron beam is emitted, and supplies the cathode electrode with an amount of heat sufficient for the cathode electrode to emit thermoelectrons. Therefore, the filament temperature is about 2000K to 3000K. This temperature causes the filament to thermally expand and deform into a convex shape toward the cathode electrode. Since the deformation of the filament changes the distance between the filament and the cathode electrode, the control of the electron beam may become unstable, that is, the electron beam output may become unstable.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a filament supporting method capable of stabilizing the electron beam output, an electron gun, and a treatment including the electron gun. To provide an apparatus.

Hereinafter, means for solving the above problems will be described.
The first aspect of the present invention is a supporting method for supporting a filament that is energized in order to heat a cathode electrode with thermoelectrons. The method includes supporting a filament by a support member, and includes supporting the filament so that a tip of the support member is displaced according to elongation of the filament generated by energization. According to this method, since the extension of the filament is absorbed by the displacement of the tip of the support member that supports the filament, the amount of displacement of the bent portion of the filament is suppressed. Therefore, fluctuations in the distance between the filament and the cathode electrode can be suppressed. For this reason, the electron beam output is stabilized.

In the above method, an example of the support member is a support, and when the filament is stretched by energization, the tip of the support may be displaced according to heat during energization of the filament. According to this method, during the energization of the filament, the tip of the column is displaced according to heat. Thereby, it becomes possible to displace the front-end | tip of a support | pillar according to the elongation of the filament generate | occur | produced with a heat | fever.

The second aspect of the present invention is an electron gun. The electron gun includes a cathode electrode, a filament that is energized to heat the cathode electrode with thermoelectrons, two struts that support the filament, a tip to which the filament is attached, and a base Two struts each having a proximal end to be secured. Each said support | pillar displaces each said front-end | tip according to the expansion | extension which generate | occur | produces in the said filament by electricity supply. According to this configuration, the displacement of the bending portion of the filament is suppressed because the extension of the filament is absorbed by the displacement of the tip of each support column supporting the filament. Therefore, fluctuations in the distance between the filament and the cathode electrode can be suppressed. For this reason, the electron beam output is stabilized.

In the above-described electron gun, each of the support columns may be configured to displace the tip of the support in accordance with heat applied to the filament. According to this configuration, the tip of the column is displaced in response to heat during energization of the filament. Thereby, it becomes possible to displace the front-end | tip of a support | pillar according to the elongation of the filament generate | occur | produced with a heat | fever.

In the above-described electron gun, each of the support columns may be configured to displace the tip of the support along the extension direction of the filament according to the extension of the filament. According to this configuration, since the elongation of the filament is absorbed by the displacement of the tip of the support column, the variation in the distance between the filament and the cathode electrode can be suppressed.

In the electron gun, each of the support columns may be configured such that the ends of the two support columns are displaced in opposite directions according to the elongation of the filament. Since the filament legs are fixed to the two columns, respectively, the filament elongation occurs in a direction toward the two legs. Therefore, according to this structure, the elongation which generate | occur | produces in a filament is absorbed by displacing the front-end | tip of two support | pillars in a mutually reverse direction.

In the electron gun, each of the support columns may be configured to include a plurality of members having different thermal expansion coefficients. According to this configuration, the tip of each column can be easily displaced according to heat by the difference in the linear expansion coefficient, that is, the thermal expansion coefficient, of the plurality of members constituting each column.

In the electron gun, each of the support columns has a first side portion and a second side portion opposite to the first side portion, and the two support columns are fixed to the base. The second sides of the two struts face each other. In this case, each of the support columns is disposed on the first side portion, and is disposed on the second side portion with the first member having the first thermal expansion coefficient, and the first thermal expansion coefficient. And a second member having a larger second thermal expansion coefficient. According to this configuration, it is possible to easily displace the end of each support column according to heat by the difference between the first and second linear expansion coefficients, that is, the thermal expansion coefficients.

In each of the electron guns, each of the support columns includes a fixing portion that fixes the base end to the base, a support portion that extends from the fixing portion, and a tip portion that is formed at the tip of the support portion and to which the filament is attached. May be included. In this case, the support part may be constituted by the first member and the second member. According to this configuration, the support portions can be easily displaced according to heat by the difference between the first and second linear expansion coefficients.

A third aspect of the present invention is a processing apparatus including the above-described electron gun. In such a processing apparatus, the electron gun suppresses fluctuations in the distance between the filament and the cathode electrode, and stabilizes the electron beam output. Accordingly, the processing apparatus can stably perform processing using an electron beam, for example, heating of an object.

As described above, according to the present invention, it is possible to provide a filament supporting method, an electron gun, and a processing apparatus including the electron gun, which can stabilize the electron beam output.

The schematic block diagram of the electron gun of one Embodiment. The schematic block diagram of the emitter part provided in the electron gun of FIG. The perspective view which shows an example of the filament of FIG. (A) (b) Explanatory drawing of the emitter part provided in the electron gun of FIG. The graph which shows the relationship between the input electric power to the filament in the electron gun of FIG. 1, and an electron beam output. The graph which shows the relationship between the input electric power to the filament in the electron gun of FIG. 1, and an electron beam output. The graph which shows the relationship between the input electric power to the cathode electrode in the electron gun of FIG. 1, and an electron beam output. (A) (b) The wave form diagram which shows the output stability evaluation result of the electron beam in the electron gun of FIG. (A) (b) The graph which shows the lifetime evaluation result of the filament in the electron gun of FIG. The schematic block diagram of another electron gun. The perspective view of another filament.

Hereinafter, an embodiment will be described.
As shown in FIG. 1, the electron gun 10 is attached to the side wall 30 a of the processing apparatus 30. The processing apparatus 30 is a vapor deposition chamber for forming a vapor deposited film of a metal oxide such as MgO (magnesium oxide) on the surface of a substrate such as a glass substrate. The electron gun 10 is, for example, a piercing electron gun, and a flange 11a of the casing 11 is fixed to the side wall 30a.

The electron gun 10 generates an electron beam EB, and emits the electron beam EB from the opening of the housing 11 toward the process chamber of the processing apparatus 30. The electron beam EB is applied to an object (deposition material) 31 disposed in the process chamber.

The electron gun 10 includes a filament 12, a cathode electrode 13, an ion collector 14, a Wehnelt electrode 15, an anode electrode 16, a flow register 17, a focusing coil 18, and an oscillating coil 19.

The filament 12, the cathode electrode 13, and the ion collector 14 are disposed on the optical axis A extending in the emission direction of the electron beam EB. The cathode electrode 13 is disposed on the emission side, that is, the opening side from the filament 12, and the ion collector 14 is disposed on the reflection exit side (opposite opening side) from the filament 12.

The central portion of the filament 12 and the cathode electrode 13 are disposed so as to face each other in the optical axis A direction.
The periphery of the cathode electrode 13 centering on the emission direction is surrounded by the Wehnelt electrode 15. On the emission side of the Wehnelt electrode 15, an anode electrode 16 having a cylindrical shape is arranged so that the center of the through hole thereof is located on the optical axis A. A cylindrical flow register 17 is arranged on the emission side of the anode electrode 16 so that the axis center thereof is located on the optical axis A.

A focusing coil 18 and an oscillating coil 19 are provided on the outer periphery of the flow register 17 in order from a position close to the anode electrode 16. The focusing coil 18 focuses the electron beam EB that has passed through the anode electrode 16 by the magnetic field generated by the focusing coil 18. The oscillating coil 19 oscillates the electron beam EB by the magnetic field generated by it.

The filament 12 is connected to a filament power source 21, and an alternating current is supplied from the filament power source 21. The cathode electrode 13 and the Wehnelt electrode 15 are connected to a cathode power source 22, and a DC voltage is applied from the cathode power source 22. The anode electrode 16 is connected to an acceleration power source 23, and a DC voltage is applied from the acceleration power source 23. The DC voltage applied to the cathode electrode 13, the Wehnelt electrode 15 and the anode electrode 16 is set so that the potential of the filament 12 is the lowest and the potential of the anode electrode 16 is the highest.

In such a pierce-type electron gun 10, first, an alternating current from the filament power source 21 is supplied to the filament 12, and the filament 12 is heated to 2000K to 3000K to emit thermoelectrons. The emitted thermoelectrons are received by the cathode electrode 13 maintained at a positive potential with respect to the filament 12 by the cathode power source 22. At the same time, the cathode electrode 13 is heated by the radiant heat of the filament 12. The cathode electrode 13 is heated by these thermoelectrons and radiant heat, and this also emits thermoelectrons. The thermoelectrons emitted by the cathode electrode 13 are a Wehnelt electrode 15 having the same potential as the cathode electrode 13 and an anode electrode 16 maintained at a positive potential with respect to the cathode electrode 13 and the Wehnelt electrode 15. The aircraft flies along the optical axis A while being accelerated by the potential difference therebetween. The thermoelectrons that have passed through the through hole of the anode electrode 16 and the flow register 17 connected to the anode electrode 16 are emitted as an electron beam EB from the opening of the housing 11 into the processing apparatus 30.

At this time, if some of the thermoelectrons emitted from the cathode electrode 13 collide with the gas remaining in the casing 11 and the processing apparatus 30, the residual gas is cationized, and the cation becomes It is accelerated by the voltage of the cathode electrode 13 and the anode electrode 16. When this accelerated cation collides with the cathode electrode 13, a hole (dent) is formed in the cathode electrode 13 due to this collision. Therefore, if such cations are released over a long period of time, a through hole is formed in the cathode electrode 13. Therefore, the ion collector 14 is disposed at a position opposite to the irradiation direction with respect to the cathode electrode 13, that is, at a position opposite to the anode electrode 16 with respect to the cathode electrode 13. The ion collector 14 absorbs positive ions passing through the through holes formed in the cathode electrode 13, that is, an ion beam, thereby suppressing damage to the electron gun 10 due to the ion beam.

Next, the configuration of the emitter section 40 included in the electron gun 10 will be described.
The emitter section 40 is an electron beam generating section and includes the filament 12, the cathode electrode 13, the Wehnelt electrode 15, the anode electrode 16, and the ion collector 14, as shown in FIG. An example of the filament 12 is shown in FIG.

The filament 12 is made of a refractory metal such as tungsten or a tungsten alloy. The filament 12 is a wire having a rectangular cross section having an outer peripheral surface constituted by four surfaces. The filament 12 has an uneven curved bent portion 12a composed of three continuous bent 12c on a virtual plane Pi including one surface (cathode facing surface) constituting the outer peripheral surface thereof. A pair of straight legs 12b extending in the normal direction of the cathode-facing surface is bent at both ends of the bent portion 12a in the direction in which the three bent portions 12c are continuous. That is, the filament 12, which is a wire having a rectangular cross section, is configured so that any of the bendings included in the filament 12 do not have a twist in the circumferential direction by forming along one of the outer peripheral surfaces. .

The filament 12 is produced by, for example, electric discharge machining. An outline of this processing method will be described. First, for example, a tungsten metal plate is prepared. The thickness of this metal plate is, for example, 0.5 mm, and this thickness corresponds to the width of the filament 12 in the optical axis A direction (see FIG. 1). A wire rod for forming the filament 12 is cut out from the metal plate by a known wire electric discharge machining apparatus. This wire has a bent portion 12a at the center in the longitudinal direction. And the filament 12 is obtained by bending the both ends of the longitudinal direction of a wire, and forming the leg part 12b.

As shown in FIG. 2, the filament 12 is attached to filament struts 42 and 43 as support members fixed to the base 41.
The emitter section 40 includes a base 41, and the base 41 is fixed to an emitter case (both not shown) by bolts or the like. Two filament struts 42 and 43 are attached to the base 41. In this example, two filament struts 42 and 43 are inserted through two through holes formed in the base 41 via insulators 44 and 45, and are fixed by nuts 46 and 47.

The filament struts 42 and 43 each have a distal end that supports the filament 12 and a proximal end that is fixed to the base 41. In this example, insertion portions for inserting the leg portions 12b of the filaments 12 are formed at the tips of the filament struts 42 and 43, respectively. Then, the filament 12 is fixed to the filament struts 42 and 43 by, for example, set screws (set screws) 48 and 49 by inserting the leg portions 12b of the filament 12 inserted into the insertion portions of the filament struts 42 and 43, respectively. It is attached to the columns 42 and 43.

Filament wires 50 and 51 are connected to the filament posts 42 and 43, respectively, and an alternating current is supplied to the filament 12 through the wires 50 and 51 and the filament posts 42 and 43.

The cathode electrode 13 is attached to the emitter case (not shown) to which the base 41 is attached, and is disposed so as to face the filament 12. A Wehnelt electrode 15 attached to the emitter case is disposed in front of the cathode electrode 13 (in the electron beam emission direction and rightward in FIG. 2).

An insulator (for example, insulator) 52 is attached to the base 41 at a position between the filament columns 42 and 43, and the ion collector 14 is attached to the tip of the insulator. As described above, the ion collector 14 is disposed on the side opposite to the cathode electrode 13 with respect to the filament 12. The ion collector 14 is connected to one of the filament struts 42 and 43 by wiring not shown.

The filament struts 42 and 43 at least partially include a portion made of a plurality of members having different materials. That is, this part may be a part of each filament support 42 or 43 or the entire filament support 42 or 43. For example, the location from the position fixed to the base 41 to the tip of each filament support 42, 43 may be constituted by a plurality of members having different materials. In the present embodiment, the filament post 42 has a fixing portion 42a for fixing the base end to the base 41, a support portion 42b extending from the fixing portion 42a, and the tip of the support portion 42b (that is, the tip of the filament post 42). ) And a tip end portion 42c to which the filament 12 is attached. And the support part 42b of this filament support | pillar 42 is comprised from the several member which has a different material. Similarly, the filament strut 43 has a fixing portion 43a for fixing its base end to the base 41, a support portion 43b extending from the fixing portion 43a, and a tip of the support portion 43b (that is, the tip of the filament strut 43). And a tip 43c to which the filament 12 is attached. And the support part 43b of this filament support | pillar 43 is comprised from the several member which has a different material. In the present embodiment, the filament struts 42 and 43 have the same configuration.

Both filament struts 42 and 43 are configured to absorb expansion and contraction generated in the filament 12 when the electron beam EB is emitted, that is, when the filament 12 is energized. The filament 12 generates heat when energized. And since the material of the filament 12 is tungsten or a tungsten alloy, it extends according to the temperature rise by heat_generation | fever. That is, the interval between the two leg portions 12b increases. For this reason, the filament struts 42 and 43 are configured so that their respective tips are displaced corresponding to the elongation of the filament 12, that is, the distance between the tips of the two filament struts 42 and 43 increases as the temperature rises. ing.

A configuration example of the filament struts 42 and 43 will be described. In the filament struts 42 and 43 of the present embodiment, each of the support portions 42b and 43b includes two types of members, that is, a first member B1 and a second member B2. The first member B1 and the second member B2 are formed of materials having different linear expansion coefficients, that is, thermal expansion coefficients. For example, the first member B1 is molybdenum (Mo), and the second member B2 is tantalum (Ta). However, as will be described later, the combination of the members B1 and B2 is not limited to molybdenum and tantalum. In other words, each of the filament struts 42 and 43 has a first side and a second side opposite to the first side, and the filament struts 42 and 43 are fixed to the base 41. In the state, those second side portions face each other. And the 1st member B1 which has a 1st linear expansion coefficient is arrange | positioned in the 1st side part (this example 1st side part of each support part 42b, 43b) of each filament support | pillar 42,43. ing. On the other hand, a second linear expansion coefficient larger than the first linear expansion coefficient is applied to the second side portions of the filament struts 42 and 43 (in this example, the second side portions of the support portions 42b and 43b). The 2nd member B2 which has is arrange | positioned. Then, based on the arrangement relationship between the two members B1 and B2 having different linear expansion coefficients, the tips of the filament struts 42 and 43 are displaced in directions away from each other as the temperature rises.

As described above, the filament 12 extends as the temperature rises. If the two filament struts 42 and 43 are not deformed, as shown in FIG. 4B, the position of the leg 12b does not change. In b), it is deformed convexly upward. That is, the distance Lsb indicated by the arrow in FIG. In addition, the position of the filament 12 at room temperature is indicated by a one-dot chain line. Due to this deformation, stress is applied to the bent portion 12a of the filament 12 during heating. When the driving of the electron gun is stopped, the temperature of the filament 12 decreases, so that the filament 12 attempts to return to the original state (position of the one-dot chain line). In other words, the bending stress is repeatedly applied to the filament 12 as the electron gun is driven / stopped. This stress causes the filament 12 to break.

On the other hand, as shown in FIG. 4 (a), in the filament struts 42 and 43 of the present embodiment, the distance between their tips increases as the temperature rises. If the spread is substantially equal to the elongation of the filament 12, the position of the bent portion 12a is substantially equal to the normal position where no temperature is applied. That is, the distance Lsa indicated by the arrow in FIG. Even if the distance between the tips is less than the extension of the filament 12, the amount of movement of the bent portion 12a, that is, the deformation (curvature) of the filament 12 is smaller than when the tip is not displaced. In FIG. 4A, the filament struts 42, 43 are all shown as the first member B1 and the second member B2 from the proximal end to the distal end.

4 (a) and 4 (b), a cathode electrode 13 (see FIG. 2) is disposed above the filament 12. FIG. Therefore, as shown in FIG. 4A, when the tips of the filament struts 42 and 43 spread, the change in the position of the bent portion 12a of the filament 12 is suppressed, so the distance Lsa between the filament 12 and the cathode electrode 13 is as shown in FIG. Compared to the case shown in (b). That is, the fluctuation of the distance Lsa between the filament 12 and the cathode electrode 13 accompanying the temperature rise is suppressed.

(Example)
A tungsten plate having a thickness of 0.5 mm was used as a metal plate, and the filament 12 was obtained using a wire electric discharge machining apparatus for the tungsten plate.

The length of the filament 12 (the distance between the centers of both legs 12b) is 35 mm at room temperature, and 35.5 mm at the time of output of the electron beam EB (filament temperature is 2800 k).

Each of the support portions 42b and 43b of the filament struts 42 and 43 is constituted by the first member B1 and the second member B2, and the first member B1 is made of molybdenum and the second member B2 is made of tantalum. The length L (the direction along the optical axis A in FIG. 2A) of the first and second members B1 and B2 is 11.5 mm, and the thickness (the direction orthogonal to the optical axis A) is 3.5 mm. The displacement amount (direction perpendicular to the optical axis A) of the tips of the filament struts 42 and 43 is 0.2 to 0.25 mm.

In addition, it is preferable that each filament support | pillar 42 and 43 has the mutually equal displacement amount of each front-end | tip. This prevents relative displacement (axial displacement) between the bent portion 12a of the filament 12 and the cathode electrode 13 with respect to the optical axis A. Further, the amount of displacement of the tip of each filament support 42, 43 is set so that the amount of variation in the distance between the bent portion 12a of the filament 12 and the cathode electrode 13 is within ± 1 mm in the direction along the optical axis A. It is preferable.

As a method for controlling the output of the electron beam EB emitted from the electron gun 10, so-called filament control and cathode control are known. The filament control is a method of controlling the output of the electron beam EB by changing the voltage applied between the filament 12 and the cathode electrode 13 by controlling the electric power supplied to the filament 12 while keeping the cathode voltage constant. is there. The cathode control is a method of controlling the cathode voltage while keeping the electric power supplied to the filament 12 constant.

Below, the result obtained by driving the electron gun 10 by filament control among these two control methods is shown.
The dependence of the output of the electron beam EB emitted from the electron gun 10 on various irradiation conditions was measured. The rated output of the electron gun 10 and the electron gun power source used for measurement is 30 kW (acceleration voltage 20 kV × 1.5 A).

FIG. 5 is a diagram showing the relationship between the input power to the filament 12 and the output of the electron beam EB for each FC distance (distance between the filament 12 and the cathode electrode 13) under the following irradiation conditions. Here, in FIG. 5, the results obtained when the FC distance is 2.6 mm are indicated by black circles, while the results obtained when the FC distance is 4.2 mm are indicated by black squares. Show.
・ Cathode voltage: 1.2kV
・ FC distance: 2.6mm, 4.2mm
It can be seen that the input power to the filament 12 when the output of the electron beam EB is 17 kV can be reduced by about 10% when the FC distance is set to 2.6 mm, compared with the case where it is set to 4.2 mm. This is considered to be because thermal electrons emitted from the filament 12 are more easily drawn into the cathode electrode 13 when the FC distance is shorter.

FIG. 6 is a diagram showing the relationship between the input power to the filament 12 and the output of the electron beam for each cathode voltage under the following irradiation conditions. In FIG. 6, the results obtained when the cathode voltage is 1.0 kV are indicated by black diamonds, the results obtained when the cathode voltage is 1.2 kV are indicated by black circles, and the cathode voltage is 1.4 kV. The results obtained at times are indicated by black triangles.
・ Cathode voltage: 1.0 kV, 1.2 kV, 1.4 kV
・ FC distance: 2.6mm
The input power to the filament 12 when the output of the electron beam EB is 17 kV decreases as the cathode voltage increases. This is presumably because thermoelectrons emitted from the filament 12 are easily drawn into the cathode electrode 13 as the cathode voltage is higher. However, it can be seen from the slopes of the graphs relating to the respective cathode voltages that the controllability of the output of the electron beam EB is improved as the cathode voltage is lower (that is, the lower the cathode voltage, the lower the slope of the graph in FIG. 6). Is).

FIG. 7 is a diagram showing the relationship between the voltage applied to the cathode electrode 13 and the output of the electron beam EB for each FC distance under the following irradiation conditions. The voltage applied to the cathode electrode 13 is the product of the cathode voltage and the current flowing between the filament 12 and the cathode electrode 13. In FIG. 7, the results obtained when the FC distance is 2.6 mm are indicated by black circles, while the results obtained when the FC distance is 4.2 mm are indicated by black squares. .
・ Cathode voltage: 1.2kV
・ FC distance: 2.6mm, 4.2mm
When the output of the electron beam EB is 17 kV, the input power to the cathode electrode 13 is reduced by about 40% when the FC distance is 2.6 mm, compared to when the FC distance is 4.2 mm. I understand that This is presumably because the heat radiation form factor, that is, the ratio of the heat reaching the cathode electrode 13 out of the heat radiated from the filament 12 is larger when the FC distance is shorter. In addition, since the amount of space charge is limited, it is considered that a higher cathode voltage is required as the FC distance is larger.

Next, the output stability of the electron gun 10 equipped with the emitter section 40 of the present embodiment and the conventional emitter section, that is, the electron gun equipped with the emitter section in which the filament column does not deform corresponding to the elongation of the filament, are measured. did. The rated output of the electron gun and the electron gun power source is 30 kW (acceleration voltage 20 kV × 1.5 A). The measurement time is about 30 hours.

FIG. 8A shows the measurement result of the electron gun 10 of the present embodiment, and FIG. 8B shows the measurement result of the electron gun of the conventional configuration.
In the conventional electron gun, the FC distance is set to 4.2 mm in order to prevent contact with the cathode electrode due to deformation (elongation) of the filament. In the conventional electron gun, the beam current value fluctuated by +3 mA / −2 mA with respect to the beam current value of 850 mA.

On the other hand, in the electron gun 10 of the present embodiment, the FC distance is set to 2.6 mm in order to deform the filament 12 so that the filament struts 42 and 43 absorb the elongation of the filament 12. In this electron gun 10, a change in beam current value of +1 mA / −1 mA was observed with respect to a beam current value of 850 mA. That is, the electron gun 10 of this embodiment can improve the fluctuation range of the beam current value to 1 / 2.5 compared to the conventional configuration.

This is considered to be because the fluctuation of the distance between the filament 12 and the cathode electrode 13 during energization can be reduced by the emitter section 40 of the present embodiment. Further, it is considered that the cathode voltage can be set low because the distance between the filament 12 and the cathode electrode 13 is shortened, and the controllability of the EB output of the electron beam is improved.

Next, in the electron gun 10 of the present embodiment and the electron gun of the conventional configuration, for each of 25 filaments, the operating time from when the filament is energized until the filament breaks is measured as the filament life (filament life) did. The output of the electron beam EB emitted from each electron gun is 17 kW.

The measurement result with the electron gun 10 of this embodiment is shown in FIG. 9A, and the measurement result with the electron gun of the conventional configuration is shown in FIG. 9B.
The average filament lifetime using a conventional electron gun was 663 hours. On the other hand, the average filament life using the electron gun 10 of this embodiment was 875 hours. As a result, the electron gun 10 of the present embodiment has an average filament life of about 1.3 times that of the conventional electron gun. This is probably because the stress applied to the filament 12 by the emitter section 40 of the present embodiment can be reduced. In addition, since the distance between the filament 12 and the cathode electrode 13 can be shortened, the cathode electrode 13 can be raised to a necessary temperature even when the power supplied to the filament 12 is small, and the filament temperature can be suppressed. it is conceivable that.

Usually, the filament of an electron gun can be obtained by bending a wire. In contrast to such a filament, the filament 12 of the present embodiment is less subject to thermal deformation because of less processing distortion. This is because the filament 12 of this embodiment is not subjected to bending, but a wire rod is cut out from one metal plate in a form having a bent portion 12a. Therefore, when an alternating current is supplied to the filament 12, the displacement of the filament 12 in the direction toward the cathode electrode 13 is suppressed more than the filament created by bending the wire. That is, the distance (FC distance) between the filament 12 and the cathode electrode 13 is stabilized. Therefore, in obtaining the output of the electron beam EB, the heating condition of the filament 12 is further relaxed by the amount of stabilization of the FC distance. Therefore, the stability of the output of the electron beam EB emitted from the electron gun 10 can be improved.

The electron gun 10 having the above configuration can be used in various processing apparatuses. The processing apparatus is, for example, a melting apparatus, a surface processing apparatus, or a film forming apparatus. For example, in the film forming apparatus, the electron gun 10 is used as a heating source for forming a protective film (for example, magnesium oxide: MgO) on the substrate surface. In this case, for example, the electron gun 10 is fixed to the side wall of the processing chamber (deposition chamber), and the electron beam EB emitted from the electron gun 10 evaporates magnesium oxide in the hearth as an evaporation source by a deflector or the like. The point is illuminated. This electron beam EB generates an evaporating flow of magnesium oxide, and a magnesium oxide film is formed on the surface of the substrate mounted on the carrier that moves so as to pass through the evaporating flow. Since the electron beam EB emitted from the electron gun 10 is stabilized, an evaporating flow of magnesium oxide is stably generated, so that a uniform film can be formed on the substrate surface. The material of the coating is selected from the group including silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum (Al), nickel / cobalt alloy (CoNi), and copper (Cu) in addition to magnesium oxide. A vapor deposition material such as at least one metal, metal oxide, or metal compound is used. Similarly, other processing apparatuses can perform stable processing.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The electron gun 10 includes a filament 12 that is energized to heat the cathode electrode 13 with thermoelectrons, and filament struts 42 and 43 as support members that support the filament 12. The filament struts 42 and 43 have front end portions 42c and 43c to which the filament 12 is attached, and fixing portions 42a and 43a fixed to the base 41, respectively. The filament struts 42 and 43 displace the tip portions 42c and 43c according to the elongation generated in the filament 12 by energization.

For this reason, the displacement of the bent portion 12a of the filament 12 is suppressed because the extension of the filament 12 is absorbed by the displacement of the tip portions 42c, 43c of the filament columns 42, 43 that support the filament 12. Therefore, fluctuations in the distance between the filament 12 and the cathode electrode 13 are suppressed. As a result, the output of the electron beam EB can be stabilized.

(2) The filament 12 is stretched by energization. And the filament support | pillars 42 and 43 displace the front-end | tip parts 42c and 43c which support the filament 12 according to the heat | fever during the electricity supply with respect to the filament 12. FIG. Therefore, it becomes possible to displace the tip portions 42c and 43c of the filament posts 42 and 43 according to the elongation of the filament 12 generated by the energized heat, and the elongation of the filament 12 can be absorbed.

(3) The filament struts 42 and 43 displace the tip portions 42 c and 43 c to which the filament 12 is attached along the direction of the filament 12 according to the elongation of the filament 12. Accordingly, since the elongation of the filament 12 is absorbed by the displacement of the tip portions 42c and 43c of the filament columns 42 and 43, it is possible to suppress the variation in the distance between the filament 12 and the cathode electrode 13.

(4) The filament struts 42 and 43 displace the respective tip portions 42c and 43c in opposite directions according to the elongation of the filament 12. Since the leg portion 12b of the filament 12 is fixed to the two filament struts 42 and 43, respectively, the elongation of the filament 12 occurs in the direction toward the two ends, that is, the two leg portions 12b. Therefore, the elongation generated in the filament 12 can be easily absorbed by displacing the tip portions 42c, 43c of the filament struts 42, 43 in opposite directions.

(5) The filament struts 42 and 43 are configured to include a plurality of members B1 and B2 having different thermal expansion coefficients. Accordingly, the tip portions 42c and 43c can be easily displaced according to heat by the difference between the linear expansion coefficients of the members B1 and B2, that is, the thermal expansion coefficient.

(6) The electron gun 10 stabilizes the output of the electron beam EB by suppressing fluctuations in the distance between the filament 12 and the cathode electrode 13. Therefore, the processing apparatus can stably perform processing using the electron beam EB, for example, heating of the object.

In addition, the said embodiment shows an example and the shape of each member etc. may be changed suitably. Some of the changes are shown below.
In the above embodiment, the support member that supports the filament 12 is formed in the shape of a “column” such as the filament columns 42 and 43. The shape of the “column” may be a columnar shape, a prismatic shape, or other shapes. But you can. That is, the shape of the “support member” is not limited to the filament struts 42 and 43 as shown in FIGS.

In the above embodiment, each of the support portions 42b and 43b is configured by the two members B1 and B2. However, in addition to the support portions 42b and 43b, the tip portions 42c and 43c are also configured by the two members B1 and B2. May be. Moreover, you may comprise each filament support | pillar 42 and 43 whole by the two members B1 and B2.

In the above embodiment, the members B1 and B2 of the filament struts 42 and 43 are molybdenum (Mo) and tantalum (Ta). However, the combination of the member B1 and the member B2 is not limited to the above embodiment, and it is sufficient that the elongation of the filament can be absorbed by the difference in the linear expansion coefficient. For example, the member B1 may be tungsten (W) and the member B2 may be molybdenum. Alternatively, the member B1 may be tungsten and the member B2 may be tantalum. That is, in the combination of the two members B1 and B2, the linear expansion coefficient (thermal expansion coefficient) of the first member B1 located outside the filament struts 42 and 43 is located inside the filament struts 42 and 43. What is necessary is just to select so that it may become smaller than that of 2nd member B2.

The thicknesses and lengths of the members B1 and B2 may be set so that the tips of the filament struts 42 and 43 are displaced corresponding to the deformation amount of the filament 12 due to thermal expansion.
-You may change suitably the structure of the electron gun 10 of the said embodiment. For example, as shown in FIG. 10, the present invention may be embodied in a so-called two-stage focusing electron gun 60 including two focusing coils 61 and 62 and two flow registers 63 and 64.

-You may change suitably the shape, the processing method, etc. of the filament 12 of the said embodiment. For example, as shown in FIG. 11, a filament 71 using a wire having a circular cross section may be used.
-Although the example by filament control was shown in the said embodiment, you may actualize this invention to the apparatus which controls an output by cathode control.

Claims (10)

A support method for supporting a filament that is energized to heat a cathode electrode by thermoelectrons,
Supporting the filament by a support member, and supporting the filament so as to displace the tip of the support member according to the elongation of the filament generated by energization;
A method for supporting a filament, comprising: The support member is a support;
Depending on the heat during energization of the filament, the tip of the column is displaced,
The method for supporting a filament according to claim 1. An electron gun,
A cathode electrode;
A filament that is energized to heat the cathode electrode with thermoelectrons;
Two struts for supporting the filament, two struts each having a distal end to which the filament is attached and a proximal end fixed to the base;
With
The electron gun according to claim 1, wherein each of the columns displaces the tip according to elongation generated in the filament by energization. Each of the columns displaces the tip according to heat during energization of the filament.
The electron gun according to claim 3. Each of the columns is configured to displace the tip of each of the filaments along the direction of the filament extension in accordance with the elongation of the filament.
The electron gun according to claim 3 or 4, wherein Each of the struts is configured such that the ends of the two struts are displaced in opposite directions according to the elongation of the filament.
The electron gun according to any one of claims 3 to 5, characterized in that: The electron gun according to any one of claims 3 to 6, wherein each of the support columns includes a plurality of members having different thermal expansion coefficients. Each of the columns has a first side and a second side opposite to the first side, and the two columns are fixed to the base. The second sides of each other face each other,
Each strut is disposed on the first side and has a first member having a first coefficient of thermal expansion and a second member disposed on the second side and larger than the first coefficient of thermal expansion. 7. The electron gun according to claim 3, comprising a second member having a thermal expansion coefficient of 2. Each post is
A fixing portion for fixing the base end to the base;
A support portion extending from the fixed portion;
And a tip portion to which the filament is attached, wherein the support portion is constituted by the first member and the second member. 9. The electron gun according to 8. A processing apparatus comprising the electron gun according to any one of claims 3 to 7.

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