JP2010040417A - Electron beam generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a heat load of a porous plate-made electrode by devising a shape of the porous plate-made electrode to achieve the high densification of electron beam excited plasma and service life prolongation of the electrode. <P>SOLUTION: In the electron beam generating device 5, the outer shape of each electrode part 10 held at an electrode holding part of a cooling chamber, shows a rectangular shape. The electrode part 10 includes a porous discharge anode 15, a porous accelerating electrode 16, a first insulating plate 17, a second insulating plate 18, a lead wire 19, and a frame-like metal plate 20. The first insulating plate 17 and the second insulating plate 18 are constituted of a heat-conductive electric insulating material, having a thermal conductivity of 5W/(m×K) or higher. The heat load of the porous discharge anode 15 and the porous accelerating electrode 16 can be reduced, and efficient cooling of the center part of a first center porous part 151 of the porous discharge anode 15, that particularly becomes high temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electron beam generator, and more particularly to an electron beam excited plasma generator, and more particularly to an electron beam generator that can be suitably used for a small electron beam excited plasma generator.

  Electron beam excited plasma (EBEP) generators are widely used for surface modification of various metal materials such as nitriding, fine dry etching of silicon wafers, and film forming such as plasma CVD and ion plating. Has been.

  The electron beam excitation plasma generator includes an electron beam generation chamber that generates an electron beam from plasma, and a reaction chamber that generates gas plasma by the electron beam emitted from the electron beam generation chamber and processes a material to be processed. In the electron beam generation chamber, a discharge cathode for generating plasma and an electron beam generator facing the discharge cathode are disposed. The electron beam generator includes a chamber, an acceleration electrode and a discharge anode held in the chamber, and an insulating plate that insulates both electrodes. The chamber has a cooling passage through which a cooling medium passes. The chamber cooled by the passage of the cooling medium cools the acceleration electrode and the discharge anode. The acceleration electrode is held in contact with the chamber, and the discharge anode is disposed so as to face the acceleration electrode through an insulating plate. The discharge anode generates plasma by electrons from the discharge cathode. The accelerating electrode accelerates by extracting electrons from the through hole of the discharge anode. The electron beam emitted from the through hole of the acceleration electrode toward the reaction chamber dissociates and ionizes the gas in the reaction chamber to generate gas plasma.

  In the electron beam excited plasma generator having such a configuration, the velocity of the electron beam emitted toward the reaction chamber can be controlled by the magnitude of the voltage applied to the acceleration electrode, and the specific pressure can be specified in the gas phase in the reaction chamber. It is possible to selectively promote the dissociation and ionization of the molecules. For this reason, according to the electron beam excitation plasma generator, even a nitrogen molecule having a large binding energy can be dissociated with high efficiency.

  As such an electron beam excited plasma generator, a device that is miniaturized using a discharge anode and an acceleration electrode made of a perforated plate is known (for example, see Patent Document 1). The discharge plate and the acceleration electrode made of this porous plate are formed in a disk shape, and are provided integrally with a circular central porous portion having a large number of through holes through which plasma electrons are transmitted, and at the periphery of the central porous portion. A frame-shaped peripheral edge.

  Here, for example, when the surface of the metal material is nitrided, if the volume of the reaction chamber is increased, it is necessary to increase the input power when generating the electron beam excited plasma. Increasing the power of the plasma source increases the thermal load on the perforated plate discharge anode and acceleration electrode. For this reason, the maximum value of the electron beam that can be steadily extracted and the electrode life are determined by the thermal load of the perforated plate electrode.

However, the conventional small electron beam excited plasma generator has not been devised to reduce the thermal load of the porous plate electrode. For this reason, the steady operation with an electron beam current of about 4 to 5 A is the limit, and there is a limit to increasing the density of the generated electron beam excited plasma and extending the life of the electrode.
JP-A-7-272894

  The present invention has been made in view of the above circumstances, and by devising the shape of the electrode made of porous plate, the thermal load of the electrode made of porous plate is reduced, the density of the electron beam excited plasma is increased, and the electrode has a long life. It is a technical problem to be solved.

  An electron beam generator of the present invention that solves the above problems is an electron beam generator disposed in an electron beam excited plasma generator so as to face a discharge cathode for plasma generation, and includes a plurality of electrode holding portions, A plurality of through-holes provided in each of the electrode holders, a chamber having a cooling mechanism, and plasma generated by electrons from the discharge cathodes and held by the electrode holders, respectively. A first central porous portion provided with a plurality of first through holes for transmitting electrons of the plasma; and a frame-shaped first peripheral portion integrally provided at the periphery of the first central porous portion. A plurality of porous discharge anodes are held in direct contact with the electrode holding portions so as to face the porous discharge anodes, and the electrons are extracted from the first through holes of the porous discharge anodes and accelerated. A second central porous portion having a plurality of second through holes for transmitting the accelerated electrons, and a frame-shaped second peripheral portion integrally provided at the periphery of the second central porous portion. A plurality of porous accelerating electrodes, disposed between each of the porous discharge anodes and each of the porous accelerating electrodes to insulate between the porous discharge anode and the porous accelerating electrode, and the first center of the porous discharge anode A plurality of first insulating plates having a through hole having a shape corresponding to the second central porous portion of the porous portion and the porous accelerating electrode, and each porous discharge anode and each electrode holding portion; A plurality of second insulating plates that insulate between the porous discharge anode and the electrode holding portion; and a plurality of lead wires for energizing each of the porous discharge anodes, and the porous discharge anode and the porous acceleration electrode The ratio of the lateral length to the longitudinal length in the outer shape is less than 1, and the front The first insulating plate and the second insulating plate is characterized by comprising from thermally conductive, electrically insulating material having a thermal conductivity of more than 5W / m · K.

  Since the central part of the first central porous part of the porous discharge anode and the second central porous part of the porous acceleration electrode are farthest from the cooled chamber, the cooling efficiency is inferior. For example, in the case of a disk-like electrode such as a porous discharge anode and a porous acceleration electrode in a conventional small electron beam excited plasma generator, the cooling efficiency is lowest at the center of the circular central porous portion. For this reason, as the discharge current flowing through the porous discharge anode increases, an excessive heat load is applied to the central portion of the first central porous portion of the porous discharge anode, and thermal damage is likely to occur in the central portion.

  In this respect, in the electron beam generator of the present invention, the ratio of the length in the short direction to the length in the long direction in the outer shape of the porous discharge anode and the porous acceleration electrode is set to less than 1. For this reason, even if it is the central portion in the longitudinal direction of the porous discharge anode, the center of the first central porous portion in the central portion is half the short length of the porous discharge anode from the outer edge of the porous discharge anode. It ’s only a long distance away. The thermal conductivity of the first insulating plate that insulates the porous discharge anode from the porous acceleration electrode, and the thermal conductivity of the second insulating plate that insulates the porous discharge anode from the chamber electrode holder is 5 W / m · K. More than that. On the other hand, the electrode holder of the chamber is cooled by a cooling mechanism. Further, the porous acceleration electrode held in direct contact with the electrode holder of the chamber is cooled by the electrode holder of the chamber. Therefore, the heat of the porous discharge anode can be efficiently diffused to the porous acceleration electrode via the first insulating plate, and can be efficiently diffused to the electrode holding portion of the chamber via the second insulating plate. Therefore, it is possible to reduce the thermal load of the porous discharge anode and the porous acceleration electrode, and it is possible to efficiently cool the central portion of the first central porous portion of the porous discharge anode that is particularly likely to have a high temperature.

  In the electron beam generator according to the present invention, preferably, the outer shapes of the porous discharge anode and the porous acceleration electrode are rectangular, and the outer shapes of the first central porous portion and the second central porous portion are rectangular. It is.

  The electron beam generator of the present invention preferably further comprises a frame-shaped metal plate disposed in contact with the first peripheral edge of the porous discharge anode. In this case, the frame-shaped metal plate is made of a metal having a higher electric conductivity than the material constituting the porous discharge anode, and the lead wire is connected to the frame-shaped metal plate. In the case where the lead wire is connected to the porous discharge anode, the potential difference generated between the portion near the connection point and the portion far from the connection point in the porous discharge anode tends to increase, and discharge occurs in the portion near the connection point in the first central porous portion. It is easy to concentrate and heat load. In this regard, when the electron beam generator of the present invention further includes a frame metal plate having a high thermal conductivity, the first central porous portion of the porous discharge anode regardless of the connection position of the lead wire to the frame metal plate. The discharge is uniformly generated as a whole, and the heat load is easily dispersed throughout the first central porous portion.

  In the electron beam generator of the present invention, preferably, the heat conductive electrical insulating material is a nitride ceramic.

  Therefore, according to the electron beam generating apparatus of the present invention, a discharge current larger than that in the prior art can be passed through the porous discharge anode, and the density of the electron beam excited plasma can be improved as compared with the prior art. In addition, the life of the porous discharge anode and the porous acceleration electrode can be extended.

  Hereinafter, embodiments of the electron beam generator of the present invention will be described in detail. In addition, embodiment described is only one Embodiment, The electron beam generator of this invention is not limited to the following embodiment. The electron beam generator of the present invention can be implemented in various forms that have been modified or improved by those skilled in the art without departing from the scope of the present invention.

  FIG. 1 is an exploded perspective view showing a main part of the electron beam generator of the present embodiment. FIG. 2 is a perspective view of the electron beam generator of the present embodiment. FIG. 3 is an explanatory view schematically showing the overall configuration of a small electron beam excited plasma generator using the electron beam generator of the present embodiment.

<Schematic configuration of small electron beam excited plasma generator>
As shown in FIG. 3, this small electron beam excited plasma generator generates an electron beam generating chamber 1 that generates an electron beam from plasma, and generates a gas plasma by an electron beam emitted from the electron beam generating chamber 1. And a reaction chamber 3 for processing the material 2 to be processed. In the electron beam generating chamber 1, a discharge cathode 4 for generating plasma and an electron beam generating device 5 facing the discharge cathode 4 are disposed. An auxiliary electrode 6 is disposed between the discharge cathode 4 and the electron beam generator 5.

  Both the discharge cathode 4 and the auxiliary electrode 6 are made of tungsten. The discharge cathode 4 is Joule-heated by a DC power source 7. The discharge cathode 4 and the auxiliary electrode 6 are connected to a DC power supply 8, and a DC discharge is generated by the DC power supply 8 between the discharge cathode 4 and the auxiliary electrode 6.

<Configuration of electron beam generator 5>
The electron beam generator 5 includes a water cooling chamber 9 and a plurality (six in this embodiment) of electrode units 10 held in the water cooling chamber 9. The water cooling chamber 9 includes a plurality of (three in this embodiment) cooling passages 11 through which cooling water as a cooling medium is supplied from a cooling water supply device (not shown). The cooling passage 11 is included in the cooling mechanism in the present invention. By allowing the cooling water to pass through the cooling passage 11 as the cooling mechanism, the entire water cooling chamber 9 can be cooled. Moreover, the number of the electrode part 10 and the electrode holding part 12 and the cooling channel | path 11 mentioned later are not specifically limited, It can set suitably. The configuration of the cooling mechanism is not particularly limited, and ethylene glycol, liquid nitrogen, or the like may be used as a cooling medium instead of water.

  The water cooling chamber 9 includes a plurality (six in this embodiment) of electrode holders 12. Each electrode holding portion 12 includes a recess 13 and a through hole 14 penetrating the bottom surface of the recess 13. The recess 13 has a rectangular shape of 64 mm × 22 m, and the depth of the recess 13 is 8 mm. The through-hole 14 is arrange | positioned in the center part of the recessed part 13, and exhibits 42 mm x 8 mm rectangular shape. Each electrode holding portion 12 holds an electrode portion 10.

  Each electrode portion 10 includes a porous discharge anode 15, a porous acceleration electrode 16, a first insulating plate 17, a second insulating plate 18, a lead wire 19, and a frame-shaped metal plate 20. The porous acceleration electrode 16, the first insulating plate 17, the porous discharge anode 15, and the frame-shaped metal plate 20 are fixed in this order on the bottom surface of the concave portion 13 of the electrode holding portion 12 with an insulating screw 21 made of an insulating material such as ceramics. Has been.

  The porous discharge anode 15 includes a first central porous portion 151 and a first peripheral edge 152. The porous discharge anode 15 is made of a graphite plate having a thickness of 1 mm. The outer shape of the porous discharge anode 15 is a rectangular shape of 58 mm × 20 mm, and the outer shape of the first central porous portion 151 is a rectangular shape of 42 mm × 8 mm. The first central porous portion 151 of the porous discharge anode 15 is provided with a large number (241 in this embodiment) of first through holes 151 a for transmitting plasma electrons generated by electrons from the discharge cathode 4. ing. The first through holes 151 a are uniformly distributed throughout the first central porous portion 151. The diameter of the first through holes 151a is 1 mm, and the interval (pitch) between the first through holes 151a is 1.2 mm. Further, five screw holes 152a through which the insulating screws 21 are inserted are provided in the first peripheral edge 152.

  The porous acceleration electrode 16 includes a second central porous portion 161 and a second peripheral edge portion 162. The porous acceleration electrode 16 is held in direct contact with the electrode holding portion 12 of the cooling chamber 9. Specifically, the second peripheral edge 162 of the porous acceleration electrode 16 is in contact with the bottom surface of the recess 13 of the electrode holding part 12. Thereby, the porous acceleration electrode 16 is conducted to the water cooling chamber 9 and grounded.

  The porous acceleration electrode 16 is made of a graphite plate having a thickness of 1 mm. The outer shape of the porous acceleration electrode 16 is a rectangular shape of 58 mm × 20 mm, and the outer shape of the second central porous portion 161 is a rectangular shape of 42 mm × 8 mm. The second central porous portion 161 of the porous accelerating electrode 16 has a large number (241 in the present embodiment) of second through holes 161 a for transmitting plasma electrons extracted from the first through holes 151 a of the porous discharge anode 15. Is penetrated. The second through holes 161 a are uniformly distributed throughout the second central porous portion 161. The diameter of the second through holes 161a is 1 mm, and the interval (pitch) between the second through holes 161a is 1.2 mm. In addition, five screw holes 162a through which the insulating screws 21 are inserted are provided in the second peripheral edge 162.

  The first insulating plate 17 is disposed between the porous discharge anode 15 and the porous acceleration electrode 16. In the center of the first insulating plate 17, the shape corresponding to the first central porous portion 151 of the porous discharge anode 15 and the second central porous portion 161 of the porous acceleration electrode 16, that is, the first central porous portion 151 and the second central porous portion. A through hole 171 having the same shape (same rectangular shape) as the outer shape of the portion 161 is provided. Five screw holes 172a through which the insulating screws 21 are inserted are provided through the peripheral edge portion 172 of the first insulating plate 17. The outer shape of the first insulating plate 17 is a rectangular shape of 58 mm × 20 mm, and the thickness of the first insulating plate 17 is 0.7 mm. The shape of the through hole 171 of the first insulating plate 17 is a rectangular shape of 42 mm × 8 mm.

  The second insulating plate 18 is disposed between the porous discharge anode 15, the porous acceleration electrode 16 and the frame-shaped metal plate 20 and the electrode holder 12 of the cooling chamber 9. It insulates from the electrode holding part 12 of the cooling chamber 9. The height of the second insulating plate 18 is 8 mm, and the thickness of the second insulating plate 18 is 1 mm.

  Both the first insulating plate 17 and the second insulating plate 18 are made of a heat conductive electrical insulating material having a thermal conductivity of 5 W / m · K or more. Specifically, both the first insulating plate 17 and the second insulating plate 18 are made of aluminum nitride as a nitride ceramic. The thermal conductivity of aluminum nitride is about 80 to 100 W / m · K.

  Here, as a heat conductive electrical insulating material having a thermal conductivity of 5 W / m · K or more that can be used for the first insulating plate 17 and the second insulating plate 18, in addition to aluminum nitride, boron nitride, silicon carbide. And alumina. Among these, aluminum nitride, boron nitride and silicon carbide having a thermal conductivity of 50 W / m · K or more are preferable. In addition, from the viewpoint of high thermal conductivity and high electrical resistivity, it is preferable to employ aluminum nitride or boron nitride as the material of the first insulating plate 17 and the second insulating plate 18.

  The lead wire 19 has a copper current introduction terminal 191. The current introduction terminal 191 of the lead wire 19 is connected to the frame-shaped metal plate 20 by an insulating screw 21 made of an insulating material such as ceramics. The porous acceleration electrode 16 conducted to the cooling chamber 9 and the current introduction terminal 191 of the lead wire 19 are connected to a DC power source 22.

  The frame-shaped metal plate 20 is disposed in direct contact with the first peripheral edge 152 of the porous discharge anode 15. Since the frame-shaped metal plate 20 and the porous discharge anode 15 are electrically connected, the porous discharge anode 15 is biased to −50 V to −200 V with respect to the ground via the current introduction terminal 191 of the lead wire 19.

  The frame-shaped metal plate 20 is made of a metal having a higher electrical conductivity than the material constituting the porous discharge anode 15. Specifically, the frame-shaped metal plate 20 is made of copper. In addition, as a kind of metal which comprises the frame-shaped metal plate 18, if it is a metal whose electric conductivity is higher than the material which comprises the porous discharge anode 15, it will not specifically limit, Although silver, gold | metal | money, etc. may be sufficient. From the viewpoint of cost, it is preferable to employ copper.

  A through-hole 201 having a shape substantially corresponding to the first central porous portion 151 of the porous discharge anode 15 and the second central porous portion 161 of the porous acceleration electrode 16 is provided in the center of the frame-shaped metal plate 20. Five screw holes 202a through which the insulating screws 21 are inserted are provided through the peripheral edge portion 202 of the frame-shaped metal plate 20. The outer shape of the frame-shaped metal plate 20 is a rectangular shape of 58 mm × 20 mm, and the thickness of the frame-shaped metal plate 20 is 0.5 mm. Moreover, the shape of the through-hole 201 of the frame-shaped metal plate 20 is a 45 mm × 13 mm rectangular shape. That is, the through-hole 201 of the frame-shaped metal plate 20 is longer in the longitudinal direction and shorter in the lateral direction than the first central porous portion 151 of the porous discharge anode 15 and the second central porous portion 161 of the porous acceleration electrode 16. These are all rectangular shapes that are a little longer.

  In the reaction chamber 3, a quartz chamber 31 and a quartz table 32 on which the material to be processed 2 is placed are disposed. Further, the inside of the quartz chamber 31 is maintained at a predetermined temperature by the external heater 33.

  In the electron beam generator 5 of the present embodiment having the above-described configuration, the outer shapes of the porous discharge anode 15 and the porous acceleration electrode 16 are rectangular, and the first central porous portion 151 and the porous acceleration of the porous discharge anode 15 are formed. The outer shape of the second central porous portion 161 of the electrode 16 is rectangular. For this reason, even if it is the central portion in the longitudinal direction of the second central porous portion 151 of the porous discharge anode 15, the center of the first central porous portion 151 in the central portion is from the outer edge of the porous discharge anode 15 to the porous discharge anode 15. The distance is only half the length of the fifteen short direction. The first insulating plate 17 that insulates the porous discharge anode 15 and the porous acceleration electrode 16 and the second insulating plate 18 that insulates the porous discharge anode 15 and the electrode holding part 12 of the cooling chamber 9 are made of aluminum nitride. . This aluminum nitride has a very high thermal conductivity of about 80 to 100 W / m · K. On the other hand, the electrode holding part 12 of the cooling chamber 9 is cooled by the cooling water flowing in the cooling passage 11. Further, the porous acceleration electrode 16 held in direct contact with the electrode holding unit 12 of the cooling chamber 9 is directly cooled by the electrode holding unit 12 of the cooling chamber 9. Therefore, the heat of the porous discharge anode 15 can be efficiently diffused to the porous accelerating electrode 16 through the first insulating plate 17, and the heat is efficiently transmitted to the electrode holder 12 of the cooling chamber 9 through the second insulating plate 18. Can diffuse well. The heat of the porous acceleration electrode 16 is efficiently diffused to the electrode holding part 12 of the cooling chamber 9. Therefore, it is possible to reduce the thermal load on the porous discharge anode 15 and the porous acceleration electrode 16, and it is possible to efficiently cool the central portion of the first central porous portion 151 of the porous discharge anode 15 that is particularly likely to be at a high temperature. .

  Further, in the electron beam generator 5 of the present embodiment, the frame-shaped metal plate 20 is disposed in direct contact with the first peripheral edge 152 of the porous discharge anode 15. A lead wire 19 is connected to the frame-shaped metal plate 20. Here, the frame-shaped metal plate 20 is made of copper having a higher electric conductivity than the material constituting the porous discharge anode 15. For this reason, in the porous discharge anode 15, the potential difference generated between the portion close to the connection point of the lead wire 19 and the portion far from it can be reduced. Therefore, regardless of the connection position of the lead wire 19 to the frame-shaped metal plate 20, the discharge can be generated almost uniformly in the entire first central porous portion 151 of the porous discharge anode 15, and the first central porous portion 151. The heat load at can also be distributed over substantially the entire first central porous portion 151.

  Therefore, according to the electron beam generator 5 of the present embodiment, a discharge current larger than that in the conventional case can be passed through the porous discharge anode 15, and the density of the electron beam excited plasma can be improved as compared with the conventional case. Moreover, the lifetime of the porous discharge anode 15 and the porous acceleration electrode 16 can be extended. Furthermore, since the outer shape of the electrode holding part 12 and the electrode part 10 is rectangular, it is connected to each electrode part 10 as compared with the case where the outer shape of the electrode holding part 12 and the electrode part 10 is circular, for example. The degree of freedom of the arrangement of the lead wires 19 and the arrangement of the cooling passages 11 in the cooling chamber 9 is increased.

  Hereinafter, an example in which the surface of a steel material (tool steel material, JIS SKD61) as the material to be processed 2 is nitrided using the small electron beam excitation plasma generator provided with the electron beam generator 5 described in the above embodiment. Will be described.

  A discharge argon gas was supplied from the port 1 a to the electron beam generation chamber 1, and a DC discharge was generated by the DC power supply 8 between the discharge cathode 4 and the auxiliary electrode 6 that were Joule-heated by the DC power supply 7. Thereafter, the DC power source 23 induces discharge in the porous discharge anode 15, and electrons are extracted from the plasma generated between the discharge cathode 4 and the porous discharge anode 15 by the porous acceleration electrode 16 to generate an electron beam. The electron beam was emitted into the reaction chamber 3. The electron beam energy at this time was controlled by the voltage of the DC power source 23. The electron beam emitted into the reaction chamber 3 collided with nitrogen gas supplied from the port 3a and introduced into the quartz chamber 31 to generate nitrogen plasma. The pressure in the quartz chamber 31 was adjusted by exhaust from the exhaust port 3b. The temperature in the quartz chamber 31 was kept at about 500 ° C. by the external heater 33.

  The conditions at the time of generating the electron beam excited plasma were as follows: electron beam energy: 80 eV, electron beam current: 10 A, nitrogen gas partial pressure: 0.12 Pa, argon gas partial pressure: 0.14 Pa. Although slight red heat was recognized over almost the entire central porous portion 151, only a part of the first central porous portion 151 was not extremely red hot. That is, it was confirmed that steady operation with an electron beam current of 10 A is possible.

  On the other hand, the frame-shaped metal plate 20 in the electron beam generator 5 described in the above embodiment is omitted, and the current introduction terminal 191 of the lead wire 19 is connected to the porous discharge anode 15 and is nitrided under the same conditions as described above. When the treatment was performed, only the portion of the lead wire 19 near the connection point of the current introduction terminal 191 was selectively greatly red-hot, and the partial heat consumption was also large. Thus, by providing the frame-shaped metal plate 20, discharge is generated almost uniformly throughout the first central porous portion 151 of the porous discharge anode 15, and the heat load in the first central porous portion 151 is changed to the first central porous portion 151. It was confirmed that it was possible to disperse almost the entire portion 151.

  In addition, using the small electron beam excitation plasma generation apparatus of the example provided with the electron beam generation apparatus 5 described in the above embodiment, the conditions for generating the electron beam excitation plasma are as follows: electron beam energy: 80 eV, nitrogen gas partial pressure : 0.12 Pa, argon gas partial pressure: 0.14 Pa, and when the electron beam current was variously changed in the range of 2 to 10 A, the plasma density of the generated electron beam excited plasma was examined. The result is shown in FIG.

  For comparison, the relationship between the electron beam current and the plasma density of the electron beam excited plasma was similarly examined in the case of using the small electron beam excited plasma generator of Comparative Example 1 equipped with the conventional electron beam generator. . The results are also shown in FIG. In the conventional electron beam generator used here, the outer shape of the porous discharge anode and the first central porous portion and the outer shape of the porous acceleration electrode and the second central porous portion are circular, and the frame-shaped metal plate 20 was omitted and the current introduction terminal 191 of the lead wire 19 was connected to the porous discharge anode.

  In FIG. 4, the square indicates the data of the example, and the black circle indicates the data of Comparative Example 1. As is clear from FIG. 4, in the data of the example, even when the electron beam current is increased to 10 A, the plasma density of the generated electron beam excited plasma increases as the electron beam current increases. did. On the other hand, in the data of Comparative Example 1, the plasma density of the generated electron beam excited plasma increased with the increase of the electron beam current only in the range of about 2 to 6 A of the electron beam current. In the current range of 6A to 10A, even if the electron beam current was increased, the plasma density of the generated electron beam excited plasma did not increase.

Further, using the small-sized electron beam excitation plasma generation apparatus of the example provided with the electron beam generation apparatus 5 described in the above embodiment, the conditions for generating the electron beam excitation plasma are as follows: electron beam energy: 80 eV, nitrogen gas partial pressure : Nitrogen treatment with 0.12 Pa, argon gas partial pressure: 0.14 Pa, sample bias voltage: −50 V, electron beam current: 8 A, plasma density: 1.7 × 10 ¹⁰ cm ⁻³ , short treatment of 3 hours From time to time, the Vickers hardness of Hv 1100 or higher was able to be obtained from the surface of the tool steel material to a depth range of 60 μm.

On the other hand, using the small electron beam excitation plasma generator of Comparative Example 1 equipped with the conventional electron beam generator, the conditions at the time of generating the electron beam excitation plasma are as follows: electron beam energy: 80 eV, nitrogen gas partial pressure: Nitriding was performed at 0.12 Pa, argon gas partial pressure: 0.14 Pa, sample bias voltage: −50 V, electron beam current: 5 A, plasma density: 1.3 × 10 ¹⁰ cm ⁻³ , and the processing time was 6 hours. Even if it was made longer, the Vickers hardness was Hv 1100 or higher only from the surface of the tool steel material to a depth range of 50 μm.

  In addition, in the small electron beam excitation plasma generator of the example provided with the electron beam generator 5 described in the above embodiment, electron beam energy: 80 eV, discharge voltage: 43 V, argon gas partial pressure: 0.15 Pa, The temperature of the porous discharge anode 15 is measured by gradually increasing the electron beam current to 1.9 A, 3.3 A, 4.5 A, 5.6 A, 6.7 A, 7.6 A, and 8.4 over time. did. In this measurement of the electrode temperature, the temperature of the first central porous portion 151 of the porous discharge anode 15 is 4 mm away from the end of the first central porous portion 151 (the end closer to the connection point of the lead wire 19). The temperature at the selected position was measured. The result is shown in FIG.

  For comparison, the small-sized electron beam excitation of the example is used except that a composite ceramic (a machinable ceramic) of alumina and silica is used instead of aluminum nitride as the material of the first insulating plate 17 and the second insulating plate 18. For the small electron beam excited plasma generator of Comparative Example 2 similar to the plasma generator, the electrode temperature was measured in the same manner as in the example. The results are also shown in FIG. The machinable ceramic has a thermal conductivity of 2 W / m · K.

  As is apparent from FIG. 5, the electrode temperature could be lowered by about 200 ° C. at the maximum by using aluminum nitride as the material of the first insulating plate 17 and the second insulating plate 18.

It is a disassembled perspective view which shows the principal part of the electron beam generator which concerns on embodiment. It is a perspective view of the electron beam generator concerning an embodiment. It is explanatory drawing which shows roughly the whole structure of the small electron beam excitation plasma generator using the electron beam generator which concerns on embodiment. In an Example and the comparative example 1, it is a graph which shows the relationship between an electron beam current and the plasma density of electron beam excitation plasma. In an Example and the comparative example 2, it is a graph which shows the relationship between an electron beam current and electrode temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 ... Discharge cathode 5 ... Electron beam generator 9 ... Cooling chamber 10 ... Electrode part 11 ... Cooling passage 12 ... Electrode holding part 13 ... Recessed part 14 ... Through-hole 15 ... Porous discharge anode 16 ... Porous acceleration electrode 17 ... 1st insulating board DESCRIPTION OF SYMBOLS 18 ... 2nd insulating board 19 ... Lead wire 20 ... Frame-shaped metal plate 21 ... Insulating screw 151 ... 1st center porous part 152 ... 1st peripheral part 151a ... 1st through-hole 161 ... 2nd center porous part 162 ... 2nd Peripheral portion 162a ... second through hole 171 ... through hole

Claims (4)

An electron beam generator disposed in an electron beam excited plasma generator so as to face a discharge cathode for plasma generation,
A chamber having a plurality of electrode holding portions, a plurality of through holes provided in each of the electrode holding portions, and a cooling mechanism;
A first central porous portion that is held by each of the electrode holding portions, generates plasma by electrons from the discharge cathode, and includes a plurality of first through holes for transmitting the generated electrons of the plasma; A plurality of porous discharge anodes having a frame-shaped first peripheral portion integrally provided at the periphery of the first central porous portion;
The electrodes are held in direct contact with the electrode holding portions so as to face the porous discharge anodes, and are accelerated by extracting the electrons from the first through holes of the porous discharge anodes, and transmitting the accelerated electrons. A plurality of porous accelerating electrodes having a second central porous portion through which a plurality of second through holes are formed, and a frame-shaped second peripheral portion integrally provided at the periphery of the second central porous portion When,
The porous discharge anode and the porous acceleration electrode are disposed between the porous discharge anode and the porous acceleration electrode to insulate the porous discharge anode and the porous acceleration electrode, and the first central porous portion of the porous discharge anode and the porous acceleration electrode A plurality of first insulating plates having through holes in a shape corresponding to the second central porous portion;
A plurality of second insulating plates disposed between each of the porous discharge anodes and each of the electrode holding portions to insulate between the porous discharge anode and the electrode holding portions;
A plurality of lead wires for energizing each of the porous discharge anodes,
The ratio of the lateral length to the longitudinal length in the outer shape of the porous discharge anode and the porous acceleration electrode is less than 1,
The electron beam generator according to claim 1, wherein the first insulating plate and the second insulating plate are made of a thermally conductive electrical insulating material having a thermal conductivity of 5 W / m · K or more.   2. The electron beam generator according to claim 1, wherein outer shapes of the porous discharge anode and the porous acceleration electrode are rectangular, and outer shapes of the first central porous portion and the second central porous portion are rectangular. . A frame-shaped metal plate disposed in contact with the first peripheral edge of the porous discharge anode;
The electron beam generator according to claim 1 or 2, wherein the frame-shaped metal plate is made of a metal having a higher electric conductivity than the material constituting the porous discharge anode, and the lead wire is connected to the frame-shaped metal plate. .   The electron beam generator according to any one of claims 1 to 3, wherein the thermally conductive electrical insulating material is a nitride ceramic.

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