JP4359597B2 - Hollow cathode discharge gun with excellent discharge stability - Google Patents

Description

  The present invention relates to a hollow cathode discharge gun, and more particularly to a hollow cathode discharge gun capable of maintaining a discharge for a long time.

  The hollow cathode discharge gun was developed as an auxiliary device to assist plasma generation at the Nagoya Fusion Research Institute in 1982, and has been used mainly for fusion research. Recently, there have been attempts to use a hollow cathode discharge gun as a discharge gas generation source of an ion plating apparatus.

  FIG. 1 is a cross-sectional view showing the structure of a hollow cathode discharge gun used in such a conventional ion plating apparatus.

Referring to FIG. 1, a hollow cathode discharge gun 100 is attached to a support 110 and has a hollow metal tube 120 made of a material such as Mo, and is inserted into the metal tube 120 in an axial direction. And a rod 130 made of a material such as Ta. In addition, a disc-shaped electron emitting member 140 surrounding the rod 130 is provided near the end of the rod 130. The electron emitting member 140 is generally made of a material such as LaB ₆ .

  A cooling water line 116 having an inlet 112 and an outlet 114 is provided around the support 110 to cool the discharge gun 100. The rod 130 is connected to a hole 118 penetrating the support 110, and an inert gas such as Ar gas flows into the metal tube through a flow path formed by the hole 118 and the inside of the rod 130.

  Further, a heat shield member 122 for blocking heat generated in the metal tube 120 is attached to the hollow of the metal tube 120 adjacent to the support 110. The heat shield member 122 can be made of a material such as molybdenum.

The hollow cathode discharge gun 100 having the above structure operates as follows.
When power is supplied to the rod 130 from the outside, the rod 130 generates heat, and the electron emitting member 140 absorbs the heat and is heated to a high temperature. If the discharge region A inside the metal tube is maintained at a temperature of about 1800 ° C. or higher, thermal electrons start to be emitted from the disk-type electron emission member 140. Discharge region of the metal tube end by the release of thermal electrons A has higher current density, the current density of for example, about 40A / cm ^2.

  Electrons generated in the discharge region A collide with an inert gas such as Ar flowing into the discharge region A and discharge occurs. The discharge gas formed by the discharge is discharged through the opening 150 formed at the end of the metal tube 120. For this purpose, a control system (not shown) for guiding the generated discharge gas to a desired point is provided at a suitable point outside the discharge gun 100.

  In order to use such a hollow cathode discharge gun as a discharge gas generation source for ion plating, the discharge in the hollow cathode discharge gun must be stably maintained during ion plating. However, the conventional hollow cathode discharge gun has a problem that the discharge is frequently turned off during the ion plating deposition.

  Particularly, in the case of a magnesium oxide protective film deposition process of a plasma display panel (PDP) for which application of the ion plating method is promising, the influence on the production line is serious due to unstable discharge guns. In the PDP production line, it takes usually 15 hours or more to restart the discharge gun. Therefore, during this period, the production line must be stopped, resulting in a huge loss in productivity.

Therefore, the present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a hollow cathode discharge gun that stably maintains discharge over a long period of time.
Another object of the present invention is to provide a vapor deposition apparatus having higher productivity than the conventional one by adopting the hollow cathode discharge gun as a discharge gas generation source.

In order to solve the above-described problem, according to one aspect of the present invention, a hollow that forms a discharge space is provided, a first opening for allowing gas to flow into the hollow is provided at one end, and the other end is provided. a metal tube having a second opening for discharging the gas from the hollow, a filament is inserted longitudinally into the tube, is mounted on the periphery of the filament in the metal tube, the heat by the heating of the filament A hollow cathode discharge gun is provided that includes two or more electron emitting members that generate electrons and are spaced apart at a predetermined interval.

In order to solve the above-mentioned problem, according to another aspect of the present invention, a hollow that forms a discharge space is provided, a first opening for flowing gas into the hollow is provided at one end, At the end, a metal tube having a second opening for flowing gas out of the hollow, a tungsten filament inserted in the metal tube in a longitudinal direction, and attached around the filament in the metal tube, A hollow cathode discharge gun including an electron emitting member that generates thermoelectrons by heating a filament is provided.

  In order to solve the above problems, according to still another aspect of the present invention, the hollow cathode discharge gun, a vapor deposition chamber capable of maintaining airtightness and having an anode inside, and the hollow cathode discharge gun are provided. There is provided a vapor deposition apparatus including a control system for inducing a discharge gas generated from the gas to an anode in the vapor deposition chamber, a hollow cathode discharge gun, and a power supply circuit unit for applying a bias voltage to the anode.

  As described above, the hollow cathode discharge gun according to the present invention employs a tungsten filament to provide a larger heat capacity and to maintain a wider discharge space inside the hollow cathode discharge gun. And more stable discharge sustaining characteristics. In addition, the hollow cathode discharge gun of the present invention employs two or more electron emitting members in the discharge space inside the discharge gun, thereby increasing the electron emission surface area and further improving the discharge sustaining characteristics. Can be improved.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals indicate the same or similar components. In addition, the accompanying drawings are shown as cross-sectional views so as to make it easy to grasp the internal structure of the discharge gun.

  The present invention focuses on the fact that the reason why the discharge maintenance safety of the conventional discharge gun 100 described above is reduced is that the thermal capacity of the tantalum rod used for discharge is low and the temperature of the discharge space cannot be stably maintained. It is a thing. In addition, the present inventors have noted that securing a wider discharge space is advantageous for maintaining the discharge, and the configuration of the discharge gun of the present invention described later has been made based on such findings. is there.

FIG. 2 is a diagram schematically illustrating the structure of a hollow cathode discharge gun 200 according to a preferred embodiment of the present invention.
Referring to FIG. 2, in the discharge gun 200 of the present invention, a filament 230 is inserted in a longitudinal direction of the metal tube into a hollow tube 220 made of a material such as Mo, and one end of the metal tube 220 is made of stainless steel. It is attached to a support 210 made of a metallic material. The metal tube 220 includes, at both ends, a first opening for inflow of inert gas and a second opening 250 for outflowing discharge gas due to discharge in the internal discharge region B. As shown in the drawing, the first opening may be implemented by an inflow pipe 218 that passes through the support 210 attached to one end of the metal tube and communicates with the hollow of the metal tube.

  The present invention is characterized in that the discharge is stably maintained using a filament having a larger heat capacity. Therefore, in the present invention, the filament 230 is preferably made of tungsten or a tungsten alloy material. The tungsten filament is capable of maintaining a discharge in a discharge space having a volume larger than that of tantalum at the same discharge current density and discharge space temperature conditions. Thus, the probability that a stable discharge is maintained can be increased as compared with the conventional case by increasing the volume of the discharge space.

  In the present invention, the filament 230 may be provided in a wound form as shown in the figure, but a U-shaped filament that is not wound may be used. The filament 230 is connected to an external power source (not shown) through two conductive leads 232. For this reason, as shown in the figure, all of the conductive leads 232 pass through the support 210 and are exposed to the outside. The exposed conductive leads 232 are made of alumina for insulation from the support 210. It is protected by an insulating material 234.

An electron emitting member 242 is mounted around the filament 230 inside the metal tube. The electron emission member 242 forms a discharge region B with the second opening 250. In the present invention, the mounting position of the electron emission member 242 can be determined in consideration of the size of a desired discharge space. In the present invention, a material that emits thermoelectrons by heating the filament 230 is used as the electron emitting member 242. Preferably, the electron emitting member is LaB ₆ .

  In addition, a cooling water line 216 may be provided on the outer periphery of the support 210 of the present invention.

The operation of the discharge gun according to the present invention described with reference to FIG. 2 is as follows. When an AC or DC current of several hundred amperes is applied to the tungsten filament 230 via the lead 232, the internal temperature of the metal tube 220 is maintained at 1800 ° C. or higher by heating the tungsten filament. The electron emitting member 242 such as LaB ₆ emits thermoelectrons at this temperature and maintains the current density in the discharge region B at approximately 40 A / cm ² . At this time, if a gas such as Ar flows into the discharge gun through the inflow pipe 218, the electrons generated in the discharge region B collide with the inflowing neutral atoms to form a plasma discharge gas, thereby causing a discharge. Be started. The discharge gas formed in the discharge region is supplied to the anode (340 in FIG. 4) through the second opening 250 by a control system such as electrodes (351 and 353 in FIG. 4) and a convergence coil (320 in FIG. 4) described later. ).

  By causing the magnetic field (Bz) generated by the control system to be generated in a direction perpendicular to the surface of the electron emitting member 242, the influence of the magnetron cut-off can be eliminated.

FIG. 3 is a view schematically showing the structure of a hollow cathode discharge gun according to another embodiment of the present invention.
Referring to FIG. 3, the hollow cathode discharge gun 200 includes a first radiating member 242 and a second electron radiating member 244, except that the discharge region is divided into two discharge regions B1 and B2. The remaining configuration is the same as the hollow cathode discharge gun of FIG.

In the present embodiment, although the volume of discharge regions B1, B2 is substantially the same as the discharge gun of FIG. 2, further comprising substantially the electron emission surface area of the electron emission member and the electron emitting member 244 to provide a thermionic Will increase. Thereby, the discharge region can be maintained in a more stable manner.

  On the other hand, FIG. 3 illustrates the case where two electron emitting members 242 and 244 are used. In the present invention, the number of the electron emitting members 242 and 244 is appropriate considering the volume of the discharge space. Anyone skilled in the art to which the present invention pertains can easily understand that this can be selected.

FIG. 4 is a view schematically showing the structure of a hollow cathode discharge gun according to still another embodiment of the present invention.
Referring to FIG. 4, the remaining structure of the hollow cathode discharge gun 200 is the same as that of the hollow cathode discharge gun of FIG. 3 except that electron emitting members 242 and 244 are disposed behind the filament 230. Although two electron-emitting members are shown as being arranged in the drawing, the present invention is not limited to this, and one or three or more electron-emitting members may be arranged.

  In the case of the embodiment shown in FIG. 2 and FIG. 3, the filament 230 is disposed inside the hole that penetrates the electron emitting member 242, so that an electrical circuit short circuit accident due to contact between the filament 23 and the electron emitting member 242 However, when the electron emitting members 242 and 244 are arranged in the direction of the filament 230 as in the present embodiment, it is possible to prevent an unforeseen accident due to a short circuit of the electric circuit.

FIG. 5 schematically shows the structure of an ion plating apparatus 300 employing the hollow cathode discharge gun 200 of the present invention.
Referring to FIG. 5, the ion plating apparatus includes a deposition chamber 310 and a hollow cathode discharge gun 200 mounted on one side of the deposition chamber 310. An anode 340 is provided in the deposition chamber 310.

  The hollow cathode discharge gun 200 is mounted on a tube-shaped mounting tool 330. The mounting tool 330 can be made of, for example, a glass material. Between the hollow cathode discharge gun 200 and the anode 340, a series of control devices for guiding the discharge gas discharged from the hollow cathode discharge gun 200 to the anode 340 is provided. The control device includes a first electrode 351 having an annular permanent magnet 342 therein, a second electrode 353 having an electromagnetic coil 354 therein, and a convergence coil mounted along the outer periphery of the deposition chamber outside the deposition chamber. 320 is included.

  The ion plating apparatus 300 includes a power supply circuit 350 that supplies a bias voltage to the first electrode 351 and the second electrode 353, the hollow cathode discharge gun 200, and the anode 340. Further, although not shown, a separate power source for supplying current to the electromagnetic coil 354 and the convergence coil 320 may be provided in the ion plating apparatus 300.

  Further, the ion plating apparatus 300 prevents the diffusion of the discharge gas emitted from the discharge gun opening, and forms the first electrode 351 and the second electrode 353 that form a passage for causing the discharge gas to go straight to the anode 340. A discharge gas passage 355 made of tungsten can also be inserted inside. When the discharge gas passage 355 is made of tungsten having a material evaporation coefficient of 100 times or more instead of conventional carbon, the discharge gas passage 355 can better withstand high temperatures, thereby having a semi-permanently long life. There are advantages that can be made. Further, when the discharge gas passage 355 is made of tungsten, a cooling water line for adjusting the temperature to be equal to or lower than the melting point of tungsten so that tungsten is not melted by a high-temperature discharge gas of generally about 10,000 to 20,000 ° C. A cooling device such as 356 may further be included.

  The detailed configuration of the ion plating apparatus 300 described above is merely an example, and it goes without saying that the ion plating apparatus 300 of the present invention can be provided by other configurations widely known to those skilled in the art. is there. Moreover, those skilled in the art will recognize that the hollow cathode discharge gun of the present invention can be applied not only to an ion plating apparatus but also to other vapor deposition apparatuses using a discharge gas.

  Since the hollow cathode discharge gun of the present invention does not cause a problem such as the end of discharge, it can be widely applied to industrial fields that require sustained discharge maintenance, such as a vapor deposition process.

It is sectional drawing which shows the structure of the conventional hollow cathode discharge gun. 1 is a diagram schematically showing a structure of a hollow cathode discharge gun according to an embodiment of the present invention. FIG. 6 is a diagram schematically showing a structure of a hollow cathode discharge gun according to another embodiment of the present invention. FIG. 6 is a view schematically showing a structure of a hollow cathode discharge gun according to still another embodiment of the present invention. It is a figure which shows roughly the ion plating apparatus with which the hollow cathode discharge gun of this invention was mounted | worn.

Explanation of symbols

100, 200: Hollow cathode discharge gun 110, 210: Support 116, 216: Cooling water line 120, 220: Tube 130: Tantalum rod
140, 242, 244: Electron emitting member 150, 250: Opening 230: Filament 310: Deposition chamber 320: Convergence coil 330: Mounting tool 340: Anode 350: Power supply circuit 351: First electrode 352: Permanent magnet 353: First Two electrodes 354: Electromagnetic coil 355: Discharge gas passage 356: Cooling water line

Claims (4)

A metal tube having a hollow forming a discharge space, having a first opening for flowing gas into the hollow at one end, and a second opening for flowing gas from the hollow at the other end When,
A filament inserted longitudinally into the tube;
Two or more electron emitting members mounted around the filament in the metal tube, generating thermoelectrons by heating the filament, and spaced apart at a predetermined interval;
Only including,
The hollow cathode discharge gun, wherein the two or more electron emission members divide the discharge space in the hollow into two or more discharge regions .   The hollow cathode discharge gun according to claim 1, wherein the filament is a tungsten filament.   2. The hollow cathode discharge gun according to claim 1, wherein the electron emitting member is LaB6. The hollow cathode discharge gun according to claim 1, wherein the two or more electron emitting members are disk-shaped members.

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