JPH11195498A - Dc plasma generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC plasma generation device capable of heating a base substance surface up to a high temperature, and capable of generating high density plasma. SOLUTION: An anode 14 provided on a center axis 142 and having a rotation symmetry cylinder structure against a center axis 142, a spiral body structure cathode 12 having a spiral center axis 121 (a cathode center axis 121) coaxially provided against the center axis 142 of the anode 14 in a state surrounding the anode 14 and composed of plural heating wires of a predetermined wire diameter peripherally provided on the outside of the anode 14 in a spiral diameter larger than the diameter of the anode 14 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current plasma generator for generating plasma near an anode based on ionization of a gas, and more particularly, to a gas phase reaction of a plurality of reactive gases in a plasma state. Chemical Vapor that can form a thin film by chemically and physically depositing a reactant on the surface of the material to be deposited with the help of an electric or magnetic field
The present invention relates to a direct-current plasma generating apparatus used for generating a reactive gas in a plasma state by a direct-current electric field applied between an anode and a cathode in a deposition film forming method (abbreviated as CVD).

[0002]

2. Description of the Related Art A conventional DC plasma generator of this type is disclosed, for example, in JP-A-6-163190 (see FIG. 6).

That is, a cylindrical anode 2 is surrounded by a cylindrical cathode 1 having a larger diameter and arranged coaxially in a closed space, and a DC voltage is applied between the anode 2 and the cathode 1. I was

As shown in FIG. 6, a cylindrical cathode 1 as a hot cathode has a plurality of heating electrodes (made of tungsten alloy or the like) between two opposed annular electrodes (made of stainless steel). What was stretched and formed into a cylindrical shape was used. However, only one is representatively shown in the figure. When a heating current is applied between two opposed annular electrodes of the cylindrical cathode 1 having such a configuration, thermoelectrons are emitted from the surface of the heating electrode heated to a high temperature by the heating current. The reactive gas was in a plasma state by the electrons.

[0005] The reactive gas in the plasma state reacts in a gas phase, and chemically and physically deposits on the surface of the object to be deposited with the help of an electric or magnetic field to form a thin film. I was

[0006]

However, in such a conventional hot-cathode type DC plasma generating apparatus, every time a heating current is applied between the annular electrodes of the cylindrical cathode 1,
The heating electrode expands due to the heat generated when the reactive electrons convert the reactive gas into a plasma state or the Joule heat generated by the heating current, and heat is applied to the heating electrode made of tungsten or the like, which is easily broken due to expansion and contraction. Stress occurs, and as a result,
Structural deformation and mechanical destruction occurred in the cylindrical cathode 1. Further, there is a technical problem that the life of the cylindrical cathode 1 may be shortened due to such structural deformation and mechanical destruction.

[0007] For the same purpose, in the conventional cold cathode type DC plasma generating apparatus, every time a field emission voltage required for field emission of field emission electrons from the annular electrode of the cylindrical cathode 1 is applied, an electric field is applied. The heat generated when the emitted electrons bring the reactive gas into a plasma state expands the heat generating electrode and generates heat stress on the heat generating electrode. Had occurred. Furthermore, due to such structural deformation and mechanical destruction,
There is a technical problem that the life of the cylindrical cathode 1 may be shortened.

An object of the present invention is to solve such a conventional technical problem, and has an anode provided on a central axis and having a cylindrical structure rotatable with respect to the central axis;
A spiral central axis (cathode central axis) is provided coaxially with the central axis of the anode in a state surrounding the anode, and a predetermined wire diameter provided around the outside of the anode with a spiral diameter larger than the diameter of the anode. The present invention provides a DC plasma generating apparatus capable of heating the body surface to a high temperature and generating high-density plasma by providing a spiral structure cathode composed of a plurality of heating wires. It is a technical issue.

In addition, even when the cathode is thermally expanded due to heat generated when thermoelectrons bring the reactive gas into a plasma state or Joule heat due to a heating current, thermal stress is generated in the cathode by the spiral structure. The technical problem of the present invention is to provide a DC plasma generator that can suppress the occurrence of structural deformation and mechanical destruction at the cathode. An object of the present invention is to provide a direct-current plasma generating apparatus that can prevent the life of a cathode from being shortened due to mechanical destruction.

[0010]

According to a first aspect of the present invention, a DC plasma generating apparatus for generating a plasma 102 near an anode 14 based on ionization of a gas is provided. , Central axis 142
A reticulated anode 14 having a cylindrical structure rotatable with respect to the central axis 142 and the anode 1
4, the central axis 121 is provided coaxially with the central axis 142 of the anode 14, and the helical diameter 122 of the anode 14 of the reticulated cylindrical structure is larger than the cylindrical diameter 144 of the anode 14. A cathode 12 having a helical structure composed of a plurality of heating wires having a predetermined wire diameter, and the anode 14 and the cathode 12
A discharge power supply 16 connected between the anode 14 and the cathode 12 for applying an electric field for generating a plasma 102 between the anode 14 and the cathode 12;
The heating current 107 for releasing 09 is applied to the cathode 1
2 is a DC plasma generating apparatus 10 having a hardware configuration having a heating power supply 18 to be applied to both ends of the DC plasma generating apparatus 2.

According to the first aspect of the present invention, the central axis of the anode 14 is formed in a state in which the helical diameter 122 is larger than the cylindrical diameter 144 of the anode 14 having a mesh cylindrical structure and surrounds the anode 14 outside the anode 14. A heating power source 18 is connected to both ends of a cathode 12 having a spiral structure composed of a plurality of heat generating wires having a predetermined wire diameter with a central axis 121 being coaxially screwed with respect to 142 to provide a heating current 107. The structure is such that the cathode 12 is heated to emit thermoelectrons 109, and the surface of the substrate to be irradiated with the plasma 102 is heated to a desired high temperature by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch). Will be able to do it.
Further, the discharge power supply 16 is used to apply an electric field for generating a plasma 102 between the anode 14 and the cathode 12. The diameter of the heating wire is adjusted and the number of spiral turns (spiral pitch) is adjusted. By adjusting 144, a desired high-density plasma 102 can be generated.

In addition, the cathode 12 which is a heating source has a helical structure to have elasticity, so that the thermoelectrons 10
9 when the cathode 12 is thermally expanded by heat generated when the reactive gas is turned into a plasma state, or when the heating current 10
Even if the cathode 12 thermally expands due to the Joule heat generated by the step 7, the amount of deformation of the cathode 12 caused by the thermal expansion can be absorbed by the spiral structure having elasticity, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode 12. As a result, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction.

According to a second aspect of the present invention for solving the above-mentioned problems, a direct current plasma generating apparatus for generating a plasma 102 in the vicinity of an anode 14 based on ionization of a gas is provided on a central axis 142. An anode 14 having a cylindrical shape, and a center axis 121 provided coaxially with a center axis 142 of the anode 14 in a state surrounding the anode 14. Spiral diameter 122 larger than diameter 144
A cathode 12 having a helical structure composed of a plurality of heat generating wires having a predetermined wire diameter and screwed outside the anode 14, connected between the anode 14 and the cathode 12, and connected to the anode 14 and the cathode 12; A discharge power supply 16 for applying an electric field for generating a plasma 102 between them, and a heating power supply for applying a heating current 107 for heating the cathode 12 to emit thermoelectrons 109 to both ends of the cathode 12 18 is a DC plasma generating apparatus 10 having a hardware configuration.

According to the second aspect of the present invention, the helical diameter 122 of the cylindrical anode 14 is larger than the cylindrical diameter 144 of the cylindrical anode 14. The outer periphery of the anode 14 is surrounded by the central axis 142 of the anode 14. Center axis 1
A heating power source 18 is connected to both ends of a cathode 12 having a spiral structure composed of a plurality of heating wires having a predetermined wire diameter in which 21 is coaxially screwed, and a heating current 107 is applied to heat the cathode 12. The surface of the substrate to be irradiated with the plasma 102 can be heated to a desired high temperature by adjusting the wire diameter and the number of spiral turns (spiral pitch) of the heating wire to have a structure for emitting thermionic electrons 109. .
Further, the discharge power supply 16 is used to apply an electric field for generating a plasma 102 between the anode 14 and the cathode 12. The diameter of the heating wire is adjusted and the number of spiral turns (spiral pitch) is adjusted. By adjusting 144, a desired high-density plasma 102 can be generated.

In addition, the cathode 12 serving as a heating source is formed into a helical structure to have elasticity.
9 when the cathode 12 is thermally expanded by heat generated when the reactive gas is turned into a plasma state, or when the heating current 10
Even if the cathode 12 thermally expands due to the Joule heat generated by the step 7, the amount of deformation of the cathode 12 caused by the thermal expansion can be absorbed by the spiral structure having elasticity, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode 12. As a result, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction.

According to a third aspect of the present invention, which is made by the present invention to solve the above-mentioned problem, the power supply for discharging 16 comprises:
A DC power source 18 for applying a DC electric field for generating a DC plasma 102 between the anode 14 and the cathode 12;
The DC plasma generating apparatus 10 according to claim 1 or 2, which has a hardware configuration that is a DC power supply 18 for applying a DC heating current 107 to both ends of the cathode 12 to heat the DC to emit thermoelectrons 109. .

According to the third aspect of the present invention, the center axis of the anode 14 is set with respect to the center axis 142 of the anode 14 with the spiral diameter 122 being larger than the diameter 144 of the anode 14 and surrounding the anode 14 outside the anode 14. A DC heating power source 18 is provided at both ends of a spiral structure cathode 12 composed of a plurality of heating wires having a predetermined wire diameter, which are screwed coaxially.
And a DC heating current 107 is applied to heat the cathode 12 by DC heating to emit thermoelectrons 109. By adjusting the wire diameter and the number of spiral turns (spiral pitch) of the heating wire, the DC plasma 102 is irradiated. The surface of the substrate to be heated can be heated to a desired high temperature. Further, a DC electric power source 16 is used to apply a DC electric field for generating a DC plasma 102 between the anode 14 and the cathode 12 by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch). By adjusting the diameter 144 of 14, the desired high density DC plasma 10
2 can be generated.

In addition, a cathode 1 serving as a DC heating source
2 has a helical structure to provide elasticity, so that the cathode 12 thermally expands due to heat generated when the thermionic electrons 10 9 bring the reactive gas into a plasma state, or the cathode 12 is heated by Joule heat generated by the heating current 107. Even in the case of expansion, the amount of deformation of the cathode 12 due to thermal expansion can be absorbed by the spiral structure having elasticity, and the occurrence of thermal stress in the cathode 12 can be reduced. As a result, Occurrence of structural deformation and mechanical destruction in the cathode 12 can be suppressed. As a result, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction.

According to a fourth aspect of the present invention, which is made by the present invention to solve the above problem, in the DC plasma generating apparatus 10 according to any one of the first to third aspects, the cathode 12 having the spiral structure is provided. However, a conductor having a circular cross-sectional shape is formed on the spiral center axis 121 by the spiral diameter 122.
Is a DC plasma generator 10 configured to be spirally wound at a predetermined spiral pitch according to the following formula.

According to the invention described in claim 4, according to claim 1,
In addition to the effects described in any one of the above items 3, the spiral 14 has a helical diameter 122 larger than the diameter 144 of the anode 14 and surrounds the anode 14 outside the anode 14. A heating power supply 18 is connected to both ends of a cathode 12 having a spiral structure composed of a plurality of heating wires having a circular cross-sectional shape in which a shaft 121 is coaxially wound at a predetermined spiral pitch, and a heating current 107 is applied. The cathode 12 is heated to emit thermoelectrons 109, and the surface of the substrate to be irradiated with the plasma 102 is heated to a desired high temperature by adjusting the circular sectional shape and the number of spiral turns (spiral pitch) of the heating wire. It can be heated. In addition, the anode 1 is
By applying an electric field for generating plasma 102 between the cathode 4 and the cathode 12, adjusting the circular cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, and adjusting the diameter 144 of the anode 14, High density plasma 102 can be generated.

In addition, the cathode 12 which is a heating source has a helical structure to have elasticity, so that the thermoelectrons 10
9 when the cathode 12 is thermally expanded by heat generated when the reactive gas is turned into a plasma state, or when the heating current 10
Even if the cathode 12 thermally expands due to the Joule heat generated by the step 7, the amount of deformation of the cathode 12 caused by the thermal expansion can be absorbed by the spiral structure having elasticity, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode 12. As a result, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction.

According to a fifth aspect of the present invention, which is achieved by the present invention, in order to solve the above-mentioned problems, in the DC plasma generating apparatus 10 according to any one of the first to third aspects, the cathode 12 having the spiral structure is provided. However, a conductor having a bar-shaped cross section is formed on the spiral central axis 121 by the spiral diameter 122.
Is a DC plasma generator 10 configured to be spirally wound at a predetermined spiral pitch according to the following formula.

According to the invention described in claim 5, according to claim 1,
In addition to the effects described in any one of the above items 3, the spiral 14 has a helical diameter 122 larger than the diameter 144 of the anode 14 and surrounds the anode 14 outside the anode 14. A heating power supply 18 is connected to both ends of a cathode 12 having a spiral structure composed of a plurality of heating wires having a rod-shaped cross-section in which a shaft 121 is coaxially wound at a predetermined spiral pitch, and a heating current 107 is applied. The structure is such that the cathode 12 is heated to emit thermoelectrons 109, and the surface of the substrate to be irradiated with the plasma 102 is heated to a desired high temperature by adjusting the rod-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire. It can be heated. In addition, the anode 1 is
The structure is such that an electric field for generating plasma 102 is applied between the cathode 4 and the cathode 12, the rod-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire are adjusted, and the diameter 144 of the anode 14 is adjusted. High density plasma 102 can be generated. In particular, a heating wire having a rod-shaped cross-section can flow a larger heating current 107 than a heating wire having a circular cross-section, and in addition, has excellent durability because it is mechanically strong. Has merits.

In addition, the cathode 12 which is a heating source has a helical structure to have elasticity, so that the thermoelectrons 10
9 when the cathode 12 is thermally expanded by heat generated when the reactive gas is turned into a plasma state, or when the heating current 10
Even if the cathode 12 thermally expands due to the Joule heat generated by the step 7, the amount of deformation of the cathode 12 caused by the thermal expansion can be absorbed by the spiral structure having elasticity, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode 12. As a result, it is possible to prevent structural deformation and mechanical destruction and to shorten the life of the cathode 12.

According to a sixth aspect of the present invention for solving the above-mentioned problem, the present invention provides a DC plasma generating apparatus 10 according to any one of the first to third aspects, wherein the cathode 12 having the spiral structure is provided. However, a conductor having a plate-shaped cross section is formed on the spiral central axis 121 by the spiral diameter 122.
Is a DC plasma generator 10 configured to be spirally wound at a predetermined spiral pitch according to the following formula.

According to the invention of claim 6, according to claim 1,
In addition to the effects described in any one of the above items 3, the spiral 14 has a helical diameter 122 larger than the diameter 144 of the anode 14 and surrounds the anode 14 outside the anode 14. A heating power supply 18 is connected to both ends of a cathode 12 having a spiral structure composed of a plurality of heating wires having a plate-like cross-sectional shape in which a shaft 121 is coaxially wound at a predetermined spiral pitch to supply a heating current 107. By heating the cathode 12 to emit thermionic electrons 109, the surface of the substrate to be irradiated with the plasma 102 can be adjusted to a desired shape by adjusting the plate-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire. It can be heated to a high temperature. In addition, the anode 1 is
By applying an electric field for generating a plasma 102 between the cathode 4 and the cathode 12, adjusting the plate-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, and adjusting the diameter 144 of the anode 14, A desired high-density plasma 102 can be generated. In particular, a heating wire having a plate-shaped cross-section allows a larger heating current 107 to flow than a heating wire having a circular cross-section, and furthermore has excellent durability because it is mechanically strong. It has such advantages.

In addition, the cathode 12 serving as a heating source has a helical structure to have elasticity, so that the thermoelectrons 10
9 when the cathode 12 is thermally expanded by heat generated when the reactive gas is turned into a plasma state, or when the heating current 10
Even if the cathode 12 thermally expands due to the Joule heat generated by the step 7, the amount of deformation of the cathode 12 caused by the thermal expansion can be absorbed by the spiral structure having elasticity, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode 12. As a result, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction.

According to a seventh aspect of the present invention to solve the above-mentioned problem, the present invention provides a DC plasma generating apparatus 10 according to any one of the fourth to sixth aspects, wherein the cathode 12 is heat-conductive. It is a DC plasma generation device 10 having a hardware configuration having a cathode structure.

According to the invention of claim 7, according to claim 4,
In addition to the effect described in any one of the above items 6 to 6, in addition to the anode 14 having a helical diameter 122 larger than the diameter 144 of the anode 14 and surrounding the anode 14 with respect to the central axis 142 of the anode 14, A DC heating power source 18 is provided at both ends of a spiral structure cathode 12 composed of a plurality of heating wires having a predetermined wire diameter on which a shaft 121 is coaxially screwed.
Is connected to apply a DC heating current 107 to heat the cathode 12 DC to emit thermoelectrons 109, and to generate plasma 102 near the anode 14 based on ionization of gas by hot cathode discharge using the emitted thermoelectrons 109. By adjusting the wire diameter and the number of spiral turns (spiral pitch) of the heating wire, the surface of the substrate to be irradiated with the DC plasma 102 can be heated to a desired high temperature. Also, the anode 14 is connected to a DC discharge power source 16.
A DC electric field for generating a DC plasma 102 is applied between the anode and the cathode 12, the diameter of the heating wire and the number of spiral turns (helical pitch) are adjusted, and the diameter of the anode 14
By adjusting 44, a desired high-density DC plasma 102 can be generated.

In addition, the cathode 1 which is a DC heating source
2 has a helical structure to provide elasticity, so that the cathode 12 thermally expands due to heat generated when thermionic electrons 109 caused by the hot cathode discharge bring the reactive gas into a plasma state, or Joule heat generated by the hot cathode discharge. Even when the cathode 12 thermally expands, the amount of deformation of the cathode 12 due to thermal expansion due to hot cathode discharge can be absorbed by the elastic helical structure, and thermal stress is generated in the cathode 12. As a result, it is possible to suppress the occurrence of structural deformation or mechanical damage due to hot cathode discharge in the cathode 12. Thus, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction due to hot cathode discharge.

According to an eighth aspect of the present invention to solve the above-mentioned problem, in the DC plasma generating apparatus 10 according to the seventh aspect, thermoelectrons 10 9 are emitted from the cathode 12 having the spiral structure. A heating current 107 required for the operation is applied to the cathode 12 and a thermoelectron 109 between the anode 14 and the cathode 12 is applied.
DC plasma configured to apply an accelerating voltage 108 for accelerating the plasma and generate plasma 102 near the anode 14 based on ionization of gas by hot cathode discharge using the emitted thermoelectrons 109. Generator 1
0.

According to the invention described in claim 8, according to claim 7,
In addition to the effect described in the above, the center axis 142 of the anode 14 is formed around the anode 14 with a helical diameter 122 larger than the diameter 144 of the anode 14.
A heating power supply 18 is connected to both ends of a spiral structure cathode 12 composed of a plurality of heating wires having a predetermined wire diameter with a central axis 121 coaxially screwed to the heating shaft.
07, the cathode 12 is heated to emit thermionic electrons 109, and the plasma 1 near the anode 14 based on the ionization of the gas by the hot cathode discharge using the emitted thermoelectrons 109.
O2 is generated, and by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), the plasma 102 is generated.
Can be heated to a desired high temperature. Further, the discharge power supply 16 is used to apply an electric field for generating a plasma 102 between the anode 14 and the cathode 12. The diameter of the heating wire is adjusted and the number of spiral turns (spiral pitch) is adjusted. By adjusting 144, a desired high-density plasma 102 can be generated.

In addition, by making the cathode 12 serving as a heating source a helical structure to have elasticity, the cathode 12 is heated by the heat generated by the hot electrons 109 caused by the hot cathode discharge to bring the reactive gas into a plasma state. When the cathode 12 expands due to expansion or Joule heat generated by hot cathode discharge.
Even when the thermal expansion of the cathode 12, the amount of deformation of the cathode 12 caused by the thermal expansion due to the hot cathode discharge can be absorbed by the spiral structure having elasticity, and the thermal stress is generated in the cathode 12. Can be mitigated, so that
The occurrence of structural deformation or mechanical destruction due to hot cathode discharge in the cathode 12 can be suppressed. Thus, it is possible to prevent the life of the cathode 12 from being shortened due to structural deformation or mechanical destruction due to hot cathode discharge.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a DC plasma generator 10 according to one embodiment of the present invention. FIG. 2 is a cross-sectional view along the central axis 142 of the DC plasma generator 10 of FIG.

The DC plasma generator 10 of the present embodiment
Is a DC plasma generator 10 for generating a DC plasma 102 in the vicinity of the anode 14 based on the ionization of hexamethyldisilane, which is a form of gas, and in particular, a gas phase reaction of a plurality of reactive gases in a plasma state. At the same time as the above-mentioned CVD, in which a thin film can be formed by chemically and physically depositing a reactant on the surface of an object to be deposited with the aid of an electric or magnetic field, A DC plasma generating apparatus 10 used to generate a reactive gas in a plasma state by a DC electric field applied to the reactive gas, wherein the DC current is generated by heat or heating current 107 generated when the reactive gas is turned into a plasma state. Even when the cathode 12 thermally expands due to Joule heat, the cathode elasticity due to the helical structure (see FIG. 3 or FIG. 4) causes Thermal stress is prevented from being generated in 12, deformation or mechanical disruption of the structure to be thought to be due to thermal stress has a function of suppressing the occurrence in the cathode 12. The shape of the spiral of the present embodiment is equivalent to a spiral shape or a spring shape. The anode 14 shown in FIGS. 1 to 4 is provided on the central axis 142 and has a stainless mesh shape having a cylindrical structure that can be rotated with respect to the central axis 142.

Specifically, as shown in FIG. 1, the annular body 2a having a smaller diameter than the spiral diameter (cathode diameter) 122 used for the cathode 12 is opposed to each other, and a stainless steel mesh is wound therebetween to form a cylindrical shape. What can be used.

The cylinder diameter 144 of the anode 14 is 4
4 mm (see FIG. 3) and 18 mm (see FIG. 4) can be used.

The material of the material constituting the anode 14 is not particularly limited. However, when the material is used for CVD, it is desirable that the material be formed of a metal having corrosion resistance to the source gas used.

In place of the cylindrical anode 14,
A similar function can be realized by using the anode 14 having a wire shape, and a similar effect due to this function can be obtained. A similar function can be realized by using a rod-shaped anode 14 instead of the cylindrical anode 14.
Similar effects due to this function can be obtained. Here, the wire-shaped anode 14 can be realized by a wire (specifically, a diameter of about 0.1 mm to 2 mm) using a high melting point metal such as a tungsten wire. The rod-shaped anode 14 is similar in material to the wire-shaped anode 14 and is made of a rod material (having a diameter larger than that of the wire rod, specifically, several mm To several centimeters). Instead of using a tungsten wire, a cathode 12 formed by uniformly stretching conductive carbon fibers (Nippon Oil Co., Ltd., Granox XN40) into a cylindrical shape can also be used.

The cathode 12 shown in FIGS. 1 to 4 is provided so as to surround the anode 14 and to have the center axis 121 substantially coincident with the center axis 142 of the anode 14. When the spiral diameter 122 is larger than the cylinder diameter 144 of the anode 14, the anode 14
A helical structure (FIG. 3 or FIG. 4) composed of a plurality of heating wires having a predetermined wire diameter and
See).

The spiral structure cathode 12 is shown in FIGS.
As shown in FIG. 5, a hot cathode structure in which a plurality of heating wires, which are conductors having a circular cross-sectional shape having a predetermined wire diameter, are wound on a spiral central axis 121 in a coil shape at a predetermined spiral pitch according to a spiral diameter 122. It has become. For example, if the wire diameter is 62
3 mm heating wire connected in parallel (Fig. 3
And a spiral structure in which four heating wires each having a wire diameter of 38 mm are connected in parallel (see FIG. 4).

At this time, the interval between the anode 14 and the cathode 12 can be appropriately selected so as to be suitable for the voltage applied to the discharge power supply 16, and usually the cylindrical diameter (anode diameter) 144 of the anode 14 or the like or the cylindrical diameter The diameter (anode diameter) 144 can be about 5 to 10 mm regardless of the wire diameter.

The cathode 12 having a helical structure has a heating current of 1
07 generates a magnetic field in the azimuthal direction, and a low lens force is generated in the direction of the spiral central axis (cathode central axis) 121. Therefore, the reactive gas DC plasma 102 brought into the plasma state near the anode 14 is efficiently subjected to CVD. Can be supplied.

For example, in the present embodiment, as shown in FIG. 2, the cathode 12 has a wire diameter of 0.2 mm and a length of 50 m between the stainless steel annular electrodes 1a, 1a having a diameter of 70 mm.
It has a structure as shown in FIG. 1 formed into a cylindrical shape by using a tungsten wire of m. Anode 1
4 is a 60-mesh stainless steel wire mesh 2b having a length of 50 mm between the stainless steel annular bodies 2a and 2a having a diameter of 50 mm.
It has a structure as shown in FIG.

In the CVD, a gas phase reaction using a DC plasma 102 of a reactive gas supplied from a DC plasma generator 10 is promoted, and at the same time, a reactant is applied to the surface of an object to be deposited with the aid of an electric or magnetic field. The above-described CVD plasma, which can be chemically and physically deposited to form a thin film, can be generated.

In CVD, at least 10 -6 To
Inside a sealed container that can withstand vacuum pressure of rr or less,
A member for supporting the base of the anode 14 is provided at a position of a cylindrical central axis (anode central axis) 142 of the anode 14, and a means for introducing a reactive gas material for CVD film formation is provided. It is desirable that parts constituting the CVD apparatus are formed of a material having sufficient corrosion resistance to a reactive gas.

When the cathode 12 is a hot cathode, it is preferable that the cathode 12 is provided with a high-melting-point heating wire. The diameter of the conductor, the number of spiral turns, the spiral pitch, and the like can be appropriately selected according to the capacity of the cathode 12 power supply to be used. Further, the material of the heating wire can be usually tungsten, a tungsten alloy, carbon, or the like, but is not particularly limited.

By using such a spiral structure for the cathode 12, the DC plasma 1 can be adjusted by adjusting the circular cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire.
The surface of the deposition substrate to be irradiated with O2 can be heated to a desired high temperature, and as a result, a thin film having a desired composition can be grown on the substrate. In addition, a structure is used in which an electric field for generating a DC plasma 102 due to decomposition products of hexamethyldisilane is applied between the anode 14 and the cathode 12 by using the discharge power supply 16, and the circular cross-sectional shape and the number of spiral turns of the heating wire ( By adjusting the helical pitch and the diameter 144 of the anode 14, the desired high density DC plasma 10
As a result, the growth rate of the thin film can be increased. In addition, the cathode 12 serving as a heating source has a helical structure to provide spring elasticity, so that the thermoelectrons 10 9 generate heat when decomposing hexamethyldisilane, which is a form of reactive gas, into a plasma state. Even when the cathode 12 is deformed by thermal expansion / contraction due to thermal expansion or contraction, or when the cathode 12 is thermally expanded / contracted and deformed by Joule heat generated by the heating current 107, the amount of deformation of the cathode 12 due to thermal expansion is reduced. It becomes possible to absorb by the spiral structure having spring elasticity, and it is possible to alleviate the occurrence of thermal stress in the cathode 12, and as a result, it is possible to suppress the occurrence of structural deformation and mechanical breakage in the cathode 12. Become like
As a result, stress applied to the cathode 12 due to structural deformation or mechanical destruction is reduced, and the cathode 1
2 can be extended.

The cathode 12 having a helical structure is composed of a plurality of heating wires having a rod-like cross-sectional shape.
21 may be wound in a coil shape at a predetermined spiral pitch in accordance with the spiral diameter 122. In this case, by adjusting the rod-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire and adjusting the diameter 144 of the anode 14,
As a result, a desired high-density DC plasma 102 can be generated, so that the growth rate of the thin film can be increased. In particular, a heating wire having a rod-shaped cross-section can flow a larger heating current 107 than a heating wire having a circular cross-section, and in addition, has excellent durability because it is mechanically strong. Has merits. The cathode 12 having a helical structure includes a plurality of heating wires having a plate-like cross-sectional shape, and the helical central axis 1.
21 may be wound in a coil shape at a predetermined spiral pitch according to the spiral diameter 122. In this case, by adjusting the plate-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, the surface of the deposition substrate to be subjected to the plasma CVD for irradiating the DC plasma 102 can be heated to a desired high temperature. As a result, a thin film having a desired composition can be grown on the substrate. Further, the anode 14 and the cathode 1 are
The structure is such that an electric field for generating a DC plasma 102 by a decomposition product of hexamethyldisilane is applied between the two, the cross-sectional shape of the heating wire and the number of spiral turns (spiral pitch) are adjusted, and the diameter 144 of the anode 14 is adjusted. As a result, the desired high-density DC plasma 102 can be generated, and as a result, the growth rate of the thin film can be increased. In particular, a heating wire having a plate-shaped cross-section allows a larger heating current 107 to flow than a heating wire having a circular cross-section, and furthermore has excellent durability because it is mechanically strong. It has such advantages.

The discharge power supply 16 shown in FIGS. 1 to 4 is a power supply for supplying power for generating a plasma discharge between the anode 14 and the cathode 12 and is connected between the anode 14 and the cathode 12. , Anode 14 and cathode 1
This is a DC power supply for applying a DC electric field for generating a DC plasma 102 by a decomposition product of hexamethyldisilane between the two. Specifically, the DC voltage is controlled so that the discharge current becomes about 3A.

The heating power supply 18 shown in FIGS. 1 to 4 is a power supply for supplying electric power for heating to the cathode 12, and heats a plurality of heating wires connected in parallel constituting the cathode 12 at the same time. A DC heating current 107 for emitting thermionic electrons 10 9 toward the anode 14 is applied to the cathode 12.
DC power supply to be applied to both ends.

In the DC plasma generating apparatus 10 having the above-described configuration, the heating current 107 required for emitting thermionic electrons 109 from the spiral-structured cathode 12 toward the anode 14 is applied to the cathode 12 at the same time. An acceleration voltage 108 for accelerating the thermoelectrons 109 is applied between the anode 14 and the cathode 12, and the emitted thermoelectrons 1
DC plasma 102 is generated in the vicinity of the anode 14 based on the ionization of hexamethyldisilane, which is a form of gas by hot cathode discharge using 09.

More specifically, the DC plasma generating apparatus 10 using the cathode 12 having the hot cathode structure generates the heating current 107 required for emitting thermionic electrons 109 from the cathode 12 having the spiral structure. At the same time as applying the voltage between the opposed annular electrodes 1a, an acceleration voltage 108 for accelerating the thermoelectrons 109 between the anode 14 and the cathode 12 is applied. A DC plasma 102 can be generated between the above-described anode 14 and the above-described cathode 12 based on the ionization of the gas by the cathodic discharge.

For example, in the present embodiment, the inside of the container is evacuated and then hydrogen is introduced to 0.06 Torr, and the cathode 12
The tungsten wire is heated to about 2500 ° C. by applying a current of about 20 A to the anode 12, and a positive voltage of 25 V is applied to the anode 12 with respect to the cathode 12 to generate a good DC plasma 102 in the internal space of the anode 14. ing. Specifically, the plasma density of the DC plasma 102 generated at the position of the cylindrical central axis (anode central axis) 142 by the Langmuir probe method was measured.
Values of 10 to the power of 11 have been obtained per cubic centimeter.

As a result, the surface of the deposition substrate to be subjected to the plasma CVD to which the DC plasma 102 is irradiated can be heated to a desired high temperature, and as a result, a thin film having a desired composition can be grown on the substrate. Become like Further, the anode 14 and the cathode 1 are
A structure for applying an electric field for generating a DC plasma 102 by the decomposition product of hexamethyldisilane between the two, adjusting the wire diameter and the number of spiral turns (spiral pitch) of the heating wire, and adjusting the diameter 144 of the anode 14. By doing
As a result, a desired high-density DC plasma 102 can be generated, so that the growth rate of the thin film can be increased. In addition, the cathode 1 as a heating source
2 having a helical structure and having spring elasticity, the cathode 12 is heated by the heat generated when the thermoelectrons 109 caused by hot cathode discharge decompose hexamethyldisilane, which is a form of reactive gas, into a plasma state. Even when the cathode 12 expands / shrinks and deforms, or when the cathode 12 thermally expands / shrinks due to Joule heat due to the hot cathode discharge, the cathode 12 due to the thermal expansion due to the hot cathode discharge.
Can be absorbed by the helical structure having spring elasticity, which can reduce the occurrence of thermal stress in the cathode 12, and as a result, structural deformation and mechanical destruction due to hot cathode discharge can be reduced. 12 can be suppressed. Accordingly, stress applied to the cathode 12 due to structural deformation or mechanical destruction due to hot cathode discharge is reduced, and the life of the cathode 12 can be extended.

Next, an embodiment of the spiral structure of the cathode 12 will be described.

FIG. 3 shows the DC plasma generator 10 of FIG.
FIG. 2 is a diagram showing a first embodiment of a spiral structure of a cathode 12 in FIG.

In the first embodiment, as shown in FIG. 3, the spiral structure of the cathode 12 is such that two tungsten alloy wires (heating wires) having a wire diameter of 62 mm are turned for two turns and the phase is set to one.
It is configured by winding it by shifting it by 80 degrees. At this time, the cylinder diameter 144 of the anode 14 is set to 44 mm.

The DC plasma generator 1 having such a structure
0, a CVD experiment was performed.
The result obtained was 50 ° C., plasma density = 1.5 × 10 ¹⁰ cm ⁻³ (discharge current = 3 A).

FIG. 4 shows the DC plasma generator 10 of FIG.
FIG. 5 is a view showing a second embodiment of the spiral structure of the cathode 12 in FIG.

In the second embodiment, the spiral structure of the cathode 12 has a 90-degree phase and a wire diameter of 38 m as shown in FIG.
m of four tungsten alloy wires (heating wires). At this time, the cylinder diameter 144 of the anode 14 is set to 18 mm.

The DC plasma generator 1 having such a structure
When a CVD experiment was performed using 0, the substrate temperature = 3
A result of 50 ° C. and a plasma density of 4.8 × 10 ¹¹ cm ⁻³ (discharge current = 3 A) was obtained.

FIG. 5 is a comparison diagram of the infrared spectrum. FIG. 5A is an infrared spectrum of hexamethyldisilane which is an example of a raw material gas, and FIG. 5B is a DC plasma of FIG. It is an infrared spectrum of the gas decomposed | disassembled using the generator 10, and FIG. 3C is an infrared spectrum of the gas decomposed using the DC plasma generator 10 of FIG.

The infrared spectrum is a measuring means for identifying a substance. Generally, when a substance is irradiated with infrared light, infrared light having a specific wavelength depending on the substance is selectively absorbed. Therefore, the spectrum of the infrared light transmitted through the substance is measured, and the transmitted light is plotted with the wave number of the infrared light on the horizontal axis and the intensity of the transmitted infrared light on the vertical axis to obtain an infrared spectrum.

In the infrared absorption spectrum of hexamethyldisilane shown in FIG. 5A, a steep spectrum such as a C—H bond is observed.

On the other hand, in the infrared absorption spectrum of the decomposition product of hexamethyldisilane when the spiral structure of the cathode 12 of the first embodiment is used, as shown in FIG. Si- (CH) observed in the infrared absorption spectrum of hexamethyldisilane shown
3) n absorption is observed. This indicates that the decomposition of hexamethyldisilane is insufficient and undecomposed hexamethyldisilane remains.

In the infrared absorption spectrum of the decomposition product of hexamethyldisilane in the case where the spiral structure of the cathode 12 of the second embodiment is used, as shown in FIG. Si- (CH) observed in the infrared absorption spectrum of hexamethyldisilane shown
3) Almost no absorption of n is observed, and instead, a sharp infrared absorption spectrum due to the Si—C bond is observed. From this, it can be seen that the decomposition of hexamethyldisilane is sufficiently performed, and that a product film mainly composed of Si-C as a decomposition product of hexamethyldisilane is formed on the substrate.

From the above experimental results, the number of heating wires was increased, and the spiral diameter 122 of the cathode 12 and the anode 1 were increased.
It can be understood that a smaller substrate diameter 144 of No. 4 can obtain a higher substrate temperature and plasma density.

[0070]

According to the first aspect of the present invention, the helical diameter of the reticulated cylindrical structure is larger than the cylindrical diameter of the anode, and the outer periphery of the anode is surrounded by the center with respect to the central axis of the anode. A heating power source is connected to both ends of a helical structure cathode composed of a plurality of heating wires having a predetermined wire diameter whose axis is screwed coaxially to apply a heating current to heat the cathode to emit thermoelectrons. By adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), the surface of the substrate to be irradiated with plasma can be heated to a desired high temperature. In addition, by using an electric power source for discharge to apply an electric field for generating plasma between the anode and the cathode, by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), and by adjusting the diameter of the anode. As a result, a desired high-density plasma can be generated.

In addition, the cathode, which is a heating source, is formed into a spiral structure to have elasticity, so that the cathode is thermally expanded due to heat generated when thermoelectrons bring the reactive gas into a plasma state, or the heating current is reduced. Even if the cathode thermally expands due to Joule heat, the amount of deformation of the cathode caused by thermal expansion can be absorbed by the elastic helical structure, reducing the occurrence of thermal stress on the cathode As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode. Thus, it is possible to prevent the life of the cathode from being shortened due to structural deformation or mechanical destruction.

According to the second aspect of the present invention, the central axis is coaxial with the central axis of the anode in a state where the helical diameter is larger than the cylindrical diameter of the cylindrical anode and surrounds the anode outside the anode. A structure in which a heating power source is connected to both ends of a cathode of a spiral structure composed of a plurality of heating wires having a predetermined wire diameter screwed into the heating body to apply a heating current to heat the cathode and emit thermoelectrons, By adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), the surface of the substrate to be irradiated with plasma can be heated to a desired high temperature. In addition, by using an electric power source for discharge to apply an electric field for generating plasma between the anode and the cathode, by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), and by adjusting the diameter of the anode. As a result, a desired high-density plasma can be generated.

According to the third aspect of the present invention, the center axis is screwed coaxially with the center axis of the anode in a state of surrounding the anode with a helical diameter larger than the diameter of the anode and surrounding the anode. A DC heating power source is connected to both ends of a spiral structure cathode composed of a plurality of heating wires having a predetermined wire diameter, and a DC heating current is applied to heat the cathode DC to emit thermoelectrons. By adjusting the wire diameter and the number of spiral turns (spiral pitch) of the electric wire, the surface of the substrate to be irradiated with the DC plasma can be heated to a desired high temperature. In addition, a DC electric power source is used to apply a DC electric field to generate DC plasma between the anode and the cathode, and the diameter of the heating wire is adjusted by adjusting the wire diameter and the number of spiral turns (spiral pitch). By doing so, a desired high-density DC plasma can be generated.

In addition, the cathode, which is a direct-current heating source, has a spiral structure to provide elasticity, so that the cathode is thermally expanded due to heat generated when thermoelectrons bring the reactive gas into a plasma state. Even when the cathode thermally expands due to Joule heat due to electric current, the amount of deformation of the cathode caused by thermal expansion can be absorbed by the elastic helical structure, and thermal stress is generated in the cathode. As a result, it is possible to suppress the occurrence of structural deformation and mechanical destruction in the cathode. Thus, it is possible to prevent the life of the cathode from being shortened due to structural deformation or mechanical destruction.

According to the invention set forth in claim 4, according to claim 1,
In addition to the effects described in any one of (3) to (3), in a state where the central axis is coaxial with the central axis of the anode while surrounding the anode with a spiral diameter larger than the diameter of the anode and surrounding the anode, A structure in which a heating power source is connected to both ends of a spiral structure cathode composed of a plurality of heating wires having a circular cross-sectional shape wound at a pitch and a heating current is applied to the cathode to heat the cathode and emit thermoelectrons. By adjusting the circular cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, the surface of the substrate to be irradiated with plasma can be heated to a desired high temperature. In addition, a structure for applying an electric field for generating plasma between the anode and the cathode using a discharge power source is used, and the circular cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire are adjusted to adjust the diameter of the anode. As a result, a desired high-density plasma can be generated.

According to the invention described in claim 5, claim 1 is provided.
In addition to the effects described in any one of (3) to (3), in a state where the central axis is coaxial with the central axis of the anode while surrounding the anode with a spiral diameter larger than the diameter of the anode and surrounding the anode, A structure in which a heating power source is connected to both ends of a spiral structure cathode composed of a plurality of heating wires having a rod-shaped cross-sectional shape wound at a pitch and a heating current is applied to heat the cathode to emit thermoelectrons. By adjusting the rod-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, the surface of the substrate to be irradiated with plasma can be heated to a desired high temperature. In addition, the discharge power source is used to apply an electric field for generating plasma between the anode and the cathode. The diameter of the anode is adjusted by adjusting the rod-shaped cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire. As a result, a desired high-density plasma can be generated. In particular, a heating wire having a rod-shaped cross-section allows a larger heating current to flow compared to a heating wire having a circular cross-section, and in addition, has excellent mechanical durability and excellent durability. have.

According to the invention set forth in claim 6, according to claim 1,
In addition to the effects described in any one of (3) to (3), in a state where the central axis is coaxial with the central axis of the anode while surrounding the anode with a spiral diameter larger than the diameter of the anode and surrounding the anode, A heating power source is connected to both ends of a spiral-structured cathode composed of a plurality of heating wires having a plate-like cross-sectional shape wound at a pitch, and a heating current is applied to heat the cathode to emit thermoelectrons. By adjusting the plate-like cross-sectional shape and the number of spiral turns (spiral pitch) of the heating wire, the surface of the substrate to be irradiated with plasma can be heated to a desired high temperature. In addition, the power supply for discharge is used to apply an electric field for generating plasma between the anode and the cathode, and the diameter of the anode is adjusted by adjusting the plate-shaped cross-section and the number of spiral turns (spiral pitch) of the heating wire. By doing so, a desired high-density plasma can be generated. In particular, a heating wire having a plate-shaped cross-section allows a larger heating current to flow compared to a heating wire having a circular cross-section, and in addition, has excellent durability because it is mechanically strong. Has merits.

According to the invention of claim 7, according to claim 4,
7. In addition to the effects described in any one of the above items 6, the central axis is screwed coaxially with respect to the central axis of the anode while surrounding the anode with a spiral diameter larger than the diameter of the anode. A DC heating power source is connected to both ends of the spiral structure cathode composed of a plurality of heating wires having a predetermined wire diameter, and a DC heating current is applied to the cathode to heat the cathode to emit thermoelectrons. A structure that generates plasma near the anode based on ionization of gas by hot cathode discharge using hot electrons, and adjusts the diameter of heating wires and the number of spiral turns (spiral pitch) to irradiate DC plasma The surface of the substrate can be heated to a desired high temperature. In addition, a DC electric power source is used to apply a DC electric field to generate DC plasma between the anode and the cathode, and the diameter of the heating wire is adjusted by adjusting the wire diameter and the number of spiral turns (spiral pitch). By doing so, a desired high-density DC plasma can be generated.

In addition, by making the cathode, which is a DC heating source, a spiral structure to have elasticity, the cathode thermally expands due to heat generated by thermionic electrons generated by hot cathode discharge when the reactive gas is turned into a plasma state. Even if the cathode thermally expands due to Joule heat due to hot cathode discharge, the amount of deformation of the cathode due to thermal expansion due to hot cathode discharge can be absorbed by the spiral structure having elasticity, The generation of thermal stress in the cathode can be reduced, and as a result, it is possible to suppress the structural deformation and the mechanical destruction due to the hot cathode discharge from occurring in the cathode. Thus, it is possible to prevent the life of the cathode from being shortened due to structural deformation or mechanical destruction due to hot cathode discharge.

According to the invention of claim 8, according to claim 7,
In addition to the effect described in the above, the helical diameter is larger than the diameter of the anode and has a predetermined wire diameter such that the central axis is screwed coaxially with the central axis of the anode in a state surrounding the anode outside the anode. A heating power supply is connected to both ends of a spiral structure cathode composed of a plurality of heating wires to apply a heating current to heat the cathode to emit thermoelectrons, and the hot cathode discharge using the emitted thermoelectrons is performed. Plasma is generated in the vicinity of the anode based on ionization of gas, and the surface of the substrate to be irradiated with plasma is heated to a desired high temperature by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch). Will be able to do it. In addition, by using an electric power source for discharge to apply an electric field for generating plasma between the anode and the cathode, by adjusting the diameter of the heating wire and the number of spiral turns (spiral pitch), and by adjusting the diameter of the anode. As a result, a desired high-density plasma can be generated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a DC plasma generator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along a central axis in the DC plasma generating apparatus of FIG.

FIG. 3 is a diagram showing a first embodiment of a spiral structure of a cathode in the DC plasma generating apparatus of FIG. 1;

FIG. 4 is a view showing a second embodiment of the spiral structure of the cathode in the DC plasma generating apparatus of FIG. 1;

5A and 5B are comparison diagrams of an infrared spectrum. FIG. 5A is an infrared spectrum of hexamethyldisilane which is an example of a raw material gas, and FIG. 5B is a diagram of the DC plasma generator of FIG. FIG. 3C is an infrared spectrum of the gas decomposed using the DC plasma generator of FIG. 4.

FIG. 6 is a perspective view showing a shape of a cathode in a conventional DC plasma generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... DC plasma generating apparatus 102 ... DC plasma 104 ... Field emission voltage 105 ... Field emission electron 107 ... Heating current 108 ... Acceleration voltage 109 ... Thermoelectron 12 ... Cathode 121 ... Helix center axis (cathode center axis) 122 ... Helix diameter ( 14 ... Anode 142 ... Cylinder central axis (Anode central axis) 144 ... Cylinder diameter (Anode diameter) 145 ... Wire diameter 16 ... Discharge power supply 18 ... Heating power supply

Claims (8)

[Claims] 1. A direct-current plasma generating apparatus for generating plasma near an anode based on ionization of a gas, comprising: a mesh-shaped anode provided on a central axis and having a cylindrical structure that is rotated about the central axis; In a state surrounding the anode, the central axis is provided coaxially with respect to the central axis of the anode, and is screwed outside the anode with a helical diameter larger than the cylindrical diameter of the anode of the mesh tubular structure. A cathode having a spiral structure composed of a plurality of heating wires having a predetermined wire diameter, a discharge power supply connected between the anode and the cathode, and applying an electric field for generating plasma between the anode and the cathode; A heating power supply for applying a heating current to both ends of the cathode to heat the cathode to emit thermoelectrons. Flow plasma generating apparatus. 2. A direct current plasma generating apparatus for generating plasma near an anode based on ionization of a gas, comprising: an anode provided on a central axis, having a cylindrical shape; and a center of the anode surrounding the anode. A central axis is provided coaxially with respect to the axis, and is constituted by a plurality of heating wires having a predetermined diameter and screwed outside the anode with a helical diameter larger than the cylinder diameter of the anode of the mesh tubular structure. A spiral-structured cathode, a discharge power supply connected between the anode and the cathode and applying an electric field for generating plasma between the anode and the cathode, and heating the cathode to emit thermoelectrons And a heating power supply for supplying a heating current to both ends of the cathode. 3. The power supply for discharging is a DC power supply for applying a DC electric field for generating a DC plasma between the anode and the cathode, and the heating power supply heats the cathode to generate thermoelectrons. The DC plasma generator according to claim 1 or 2, wherein the DC power supply is a DC power supply for applying a DC heating current for discharging to both ends of the cathode. 4. The helical structure cathode is characterized in that a conductor having a circular cross-sectional shape is configured to be spirally wound at a predetermined helical pitch on the helical central axis according to the helical diameter. The DC plasma generator according to any one of claims 1 to 3. 5. The spiral structured cathode according to claim 1, wherein a conductor having a rod-shaped cross-sectional shape is formed by spirally winding a conductor having a rod-shaped cross-sectional shape on the central axis of the spiral at a predetermined spiral pitch according to the spiral diameter. 4. The method according to claim 1, wherein:
The direct-current plasma generator according to any one of the above. 6. A cathode having a spiral structure, wherein a conductor having a plate-like cross-sectional shape is configured by being spirally wound at a predetermined spiral pitch on the central axis of the spiral according to the spiral diameter. The direct-current plasma generator according to any one of claims 1 to 3. 7. The DC plasma generator according to claim 4, wherein the cathode has a hot cathode structure. 8. A heating current necessary for emitting thermoelectrons from the cathode having the spiral structure is applied to the cathode, and an accelerating voltage for accelerating thermoelectrons is applied between the anode and the cathode. The DC plasma generation apparatus according to claim 7, wherein the apparatus is configured to generate plasma near the anode based on ionization of gas by hot cathode discharge using the emitted thermoelectrons. .