JP2003168596A - Discharge plasma electrode and discharge plasma treatment apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge plasma electrode equipped with a mechanism which can efficiently cool the electrode from the outside without providing a duct line for a cooling medium within the electrode, and a discharge plasma treatment apparatus using this electrode. <P>SOLUTION: The discharge plasma electrode is equipped with a cooling fin composed of metal projections on a back surface of an electrode discharge surface and has such a cooling mechanism as a cooling medium is sprayed on the back surface of the electrode discharge surface. The electrode can be very thinned to save the weight thereof. The discharge plasma treatment apparatus uses this discharge plasma electrode as at least one of a pair of plasma discharge electrodes. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge plasma electrode, and more particularly to a discharge plasma electrode having a cooling mechanism on the back surface of the discharge surface and a discharge plasma processing apparatus using the same.

[0002]

2. Description of the Related Art Normally, in the plasma CVD method and the like,
When processing an object using discharge plasma generated by applying an electric field between electrodes, the temperature of the electrode rapidly rises due to thermoelectrons, thermal plasma, resistance heating, etc. generated during discharge simultaneously with plasma processing. However, there is a risk that arc discharge or non-uniform and unstable discharge occurs, and the plasma treatment cannot be performed uniformly. Therefore, conventionally, a treatment is performed by forming a conduit in the electrode and circulating a coolant to cool the electrode. In order to provide a pipe through which the coolant passes inside the electrode, the electrode itself needs to have a thickness equal to or larger than that pipe, and as a result, the weight of the electrode itself becomes heavy, and the work process in handling and manufacturing is increased. There was a problem that it became complicated. In addition, there is a problem that equipment costs and material costs increase.

[0003]

In view of the above problems, the present invention provides a discharge plasma electrode provided with a mechanism capable of efficiently cooling the electrode from the outside without providing a conduit for a coolant inside the electrode and the discharge plasma electrode. It is an object to provide a discharge plasma processing apparatus used.

[0004]

As a result of intensive studies to solve the above problems, the present inventor has found that by providing a cooling mechanism on the back surface of an electrode, thermoelectrons generated during discharge, thermal plasma, resistance heating, etc. The present invention has been completed by finding that the heat of the generated electrode can be efficiently cooled and the electrode can be made very thin.

That is, the first invention of the present invention is a discharge plasma electrode characterized by having a cooling mechanism on the back surface of the discharge surface.

A second aspect of the present invention is characterized in that the cooling mechanism is such that the cooling mechanism is provided with cooling fins made of metal protrusions on the back surface of the discharge surface to increase the heat radiation area. The discharge plasma electrode according to the first invention.

A third aspect of the present invention is the discharge plasma electrode according to the first aspect of the present invention, wherein the cooling mechanism is a mechanism for spraying a mist-like coolant on the back surface of the discharge surface to radiate heat. is there.

A fourth aspect of the present invention is a glow discharge plasma generated by applying an electric field between a pair of electrodes, at least one of which is coated with a solid dielectric, and introducing a processing gas between the electrodes. A discharge plasma processing apparatus for processing a substrate to be processed, wherein at least one of the electrodes is the discharge plasma electrode according to any one of the first to third inventions.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of a discharge plasma electrode having a cooling mechanism on the back surface of the discharge surface of the present invention will be described with reference to the drawings. Figure 1
FIG. 4 is a schematic diagram illustrating an example of a cooling mechanism for a discharge plasma electrode of the present invention. In FIG. 1, an electric field is applied from a power source 1 between a pair of electrodes 2 and 3 to generate electrodes 2 and 3.
A device for generating plasma in the discharge space 4 between them, and having a cooling mechanism configuration in which cooling fins 5 made of a plurality of metal plate-shaped projections are installed on the back surfaces of the electrodes 2 and 3. . At least one of the pair of electrodes 2 and 3 may be an electrode having a cooling structure with a cooling fin 5 on the back surface, but both electrodes are electrodes having a cooling structure with a cooling fin 5 on the back surface. Is preferred. The material of the cooling fins 5 is not particularly limited as long as it is a metal, but stainless steel, aluminum and copper metals are preferable, and the same material as the electrode is particularly preferable. Moreover, the total surface area of the cooling fins 5 to be installed is preferably 2 to 100 times, more preferably 10 to 50 times the total surface area of the back surface of the electrode discharge. The cooling fins 5 are preferably mounted vertically on the back surface of the electrode, but the mounting may be angled in order to increase the heat dissipation efficiency. Further, it is more preferable to combine with a blower because the cooling efficiency is increased.

FIG. 2 is a schematic view for explaining another example of the cooling mechanism for the discharge plasma electrode of the present invention. In FIG. 2, an electric field is applied from a power source 1 between a pair of electrodes 2 and 3 to generate a plasma in a discharge space 4 between the electrodes 2 and 3, which is an electrode 2 and an electrode 3. The cooling mechanism has a structure in which the atomized coolant 8 is sprayed from the nozzle 7 to the back surface of the device to radiate heat. The atomized refrigerant 8 is preferably generated by a nozzle 7. The nozzle may be of a general shape or may be movable, and the number and mounting positions thereof can be appropriately selected depending on the discharge conditions and the like. . Further, the atomized refrigerant needs to have a structure that does not leak from the back surface of the electrode, and it is preferable to provide a container 6 as shown in FIG. 2 in which a circulation function or a discharge function is provided. When it has a circulation function, it is more preferable that it also has a chiller. The type of the refrigerant is preferably water, and may be a non-conductive refrigerant such as insulating oil or a non-combustible / flame-retardant refrigerant.

As the cooling mechanism provided on the back surface of the discharge surface of the plasma electrode of the present invention, a cooling mechanism in which the cooling fin structure and the atomized coolant spraying structure are combined can be used.

The material of the electrode is not particularly limited as long as it is a metal, but preferably, iron-based materials such as stainless steel, copper, aluminum and the like can be mentioned. The shape of the electrodes is not particularly limited, but a parallel plate type having a structure in which the distance between the opposing electrodes is constant is preferable in order to facilitate cooling and avoid generation of arc discharge due to electric field concentration.

The discharge plasma processing apparatus of the present invention is an apparatus including an electrode having a mechanism for efficiently cooling the back surface of the electrode from the outside. An electric field is applied between a pair of electrodes, at least one of which is coated with a solid dielectric. Then, a processing gas is introduced between the electrodes to process the substrate to be processed with the glow discharge plasma generated.

The distance between the electrodes in the discharge plasma processing apparatus of the present invention depends on the thickness of the solid dielectric, the magnitude of the applied voltage,
The thickness is appropriately determined in consideration of the purpose of using plasma and the like, but is preferably 0.1 to 50 mm. 0.1 m
If it is less than m, it may not be sufficient to install the electrodes with a space therebetween. If it exceeds 50 mm, it is difficult to generate uniform discharge plasma.

One or both of the facing surfaces of the electrode must be coated with a solid dielectric. It is preferable that the solid dielectric adheres to the electrode and completely covers the facing surface of the electrode. If there is a portion where the electrodes directly face each other without being covered with the solid dielectric, arc discharge easily occurs from there. The thickness of the solid dielectric is preferably 0.01 to 4 mm. If it is too thick, a high voltage may be required to generate discharge plasma, and if it is too thin, dielectric breakdown may occur when a voltage is applied and arc discharge may occur.

Examples of the material of the solid dielectric material include plastics such as silicone rubber, polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, barium titanate and the like. Complex oxides of
And those obtained by layering these layers. Further, in order to obtain stable plasma discharge, it is preferable that the surface of the solid dielectric material coated on the electrode is smooth, and the arithmetic average roughness Ra is preferably 10 μm or less.

In the device of the present invention, an electric field of high frequency, pulse wave, microwave or the like is applied between the electrodes to generate plasma, but it is preferable to apply a pulsed electric field, and in particular, rise of the electric field. And / or an electric field with a fall time of 10 μs or less is preferred. 1
If it exceeds 0 μs, the discharge state easily shifts to an arc and becomes unstable, and it becomes difficult to maintain the high-density plasma state due to the pulsed electric field. Further, the shorter the rise time and the fall time are, the more efficiently the gas is ionized at the time of plasma generation, but it is actually difficult to realize a pulsed electric field having a rise time of less than 40 ns. It is more preferably 50 ns to 5 μs. Note that the rising time referred to here means the time when the voltage (absolute value) continuously increases, and the falling time means the time when the voltage (absolute value) continuously decreases.

The electric field strength of the pulse electric field is 10 to 10
It is preferably set to 00 kV / cm. If the electric field strength is less than 10 kV / cm, the treatment takes too long, and if it exceeds 1000 kV / cm, arc discharge is likely to occur.

The frequency of the pulsed electric field is 0.5 kHz.
The above is preferable. If it is less than 0.5 kHz, the plasma density is low and the treatment takes too long. The upper limit is not particularly limited, but is commonly used 13.56M
A high frequency band such as Hz or a test-use 500 MHz may be used. Considering the ease of matching with the load and the handling property, the frequency is preferably 500 kHz or less. By applying such a pulsed electric field, the processing speed can be greatly improved.

Further, one pulse duration in the above pulsed electric field is preferably 200 μs or less. If it exceeds 200 μs, arc discharge is likely to occur. Here, one pulse duration is ON, OF
It means the continuous ON time of one pulse in the pulse electric field composed of the repetition of F.

Here, as the means for bringing the plasma into contact with the substrate to be treated, for example, (1) the substrate to be treated is arranged in the discharge space of the plasma generated between the opposing electrodes, and the substrate to be treated is There is a method of bringing the plasma into contact with (1), and (2) a method of bringing the plasma generated between the opposing electrodes into contact with the substrate to be treated arranged outside the discharge space (remote type).

As a specific method of the above (1), a substrate to be treated is placed between parallel plate electrodes covered with a solid dielectric and brought into contact with plasma, and the upper electrode having a large number of holes. And a method of treating with a shower-like plasma, a method of providing a container-like solid dielectric having an outlet nozzle on one electrode, and spraying the plasma from the nozzle onto a substrate to be treated arranged on another electrode. To be

As a concrete method of the above (2),
A solid dielectric is extended to form a plasma induction nozzle, and there is a method of spraying it toward a substrate to be treated that is located outside the discharge space. Parallel plate electrodes and elongated nozzles, coaxial cylinders. A combination of mold electrodes and cylindrical nozzles can be used. The material of the tip of the nozzle does not necessarily have to be the above solid dielectric, and may be metal or the like as long as it is insulated from the above electrodes.

The substrate to be treated used in the apparatus of the present invention may be in the form of film, sheet or sheet. Specific examples include base materials for semiconductors, such as copper clad laminates, printed circuit boards, TAB tapes, and prepregs. Also, as the material, polyimide, epoxy resin,
Examples thereof include BT resin, PPE resin, polyester resin, polyolefin resin, polyamide resin, liquid crystal polymer resin and the like.

The processing pressure in the discharge plasma processing apparatus of the present invention is not particularly limited, but it can be carried out under a pressure near atmospheric pressure, and is 1.333 × 10 ^{4 to} 10.664 ×.
10 is preferably carried out under a pressure of ⁴ Pa, among others, easy pressure adjustment device is simplified 9.331 × 10 ⁴ ~
It is preferable to carry out in the range of 10.397 × 10 ⁴ Pa.

In the above processing, any processing can be performed by selecting the processing gas existing in the discharge plasma generation space.

As the processing gas, CF ₄ , C ₂ F ₆ , C
A water repellent surface can be obtained by using a fluorine-containing compound gas such as ClF ₃ or SF ₆ .

As the processing gas, oxygen element-containing compounds such as O ₂ , O ₃ , water and air, nitrogen element-containing compounds such as N ₂ and NH ₃ , and sulfur element-containing compounds such as SO ₂ and SO ₃ are used. Then, a hydrophilic surface can be obtained by forming hydrophilic functional groups such as carbonyl group, hydroxyl group and amino group on the surface of the base material to increase the surface energy. Further, the hydrophilic polymer film can be deposited by using a polymerizable monomer having a hydrophilic group such as acrylic acid or methacrylic acid.

Further, by using a processing gas such as a metal-hydrogen compound of a metal such as Si, Ti or Sn, a metal-halogen compound or a metal alcoholate, SiO ₂ , TiO ₂ or SnO is used.
A metal oxide thin film such as ₂ is formed and is electrically and
Optical function can be given, and halogen gas is used for etching and dicing, oxygen gas is used for resist treatment and removal of organic contaminants, and inert gas such as argon and nitrogen is used. Surface cleaning and surface modification can also be performed with plasma.

From the viewpoint of economy and safety, it is preferable to perform the treatment in an atmosphere diluted with a diluent gas as described below, rather than in the atmosphere for the treatment gas alone. As the diluent gas, helium, neon, argon,
Examples include rare gases such as xenon, nitrogen gas, and the like. You may use these individually or in mixture of 2 or more types.

[0031]

EXAMPLES The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 A discharge plasma treatment was carried out using the apparatus shown in FIG. An aluminum metal parallel plate electrode having a width of 500 mm, a length of 500 mm and a thickness of 3 mm is used as the electrodes 2 and 3, and aluminum cooling fins (height 50 ×
10 pieces (width 500 mm × thickness 1 mm) were provided at intervals of 50 mm. Furthermore, an air-cooled fan is used to facilitate heat dissipation. The electrode facing surfaces of the electrodes 2 and 3 were coated with alumina as a solid dielectric to a thickness of 1.0 mm. A 0.2 μm-thick polyimide film was placed between the electrodes as a substrate to be treated. Using dry air as a processing gas, a pulse electric field having a pulse rising speed of 5 μs, a voltage of 15 kV _PP and a frequency of 10 kHz was applied between the electrodes, and the substrate film surface was subjected to glow discharge plasma treatment. As a result, the discharge state was good, and the uniform treatment of the substrate film surface was continuously performed.
I was able to do it on time. The electrode temperature was stable and kept at 110 ° C. An electrode of the same size having a refrigerant pipe inside the conventional electrode needs to have a thickness of 20 mm, and the electrode of the present invention can have a weight of 1/5 as compared with the conventional product. It was

Example 2 A discharge plasma treatment was performed using the apparatus shown in FIG. 1000 mm wide x 1000 mm long as electrodes 2 and 3
A parallel plate electrode made of SUS420JS having a thickness of 5 mm was used, and fog water was sprayed from the two nozzles on the back surfaces of both electrodes. In addition, to prevent fog water from leaking outside, thickness 5
mm polyvinyl chloride resin 1200 mm x 1200
A mm × 500 mm container was used, and the electrode portion was hollowed out from the container, and the enclosure 6 in which the joint portion was leak-proofed was provided. The electrode facing surfaces of the electrodes 2 and 3 were coated with alumina as a solid dielectric to a thickness of 1.0 mm. As the object to be processed, a polyolefin film having a thickness of 0.1 μm was placed between the electrodes. Using argon as a processing gas, a pulse electric field having a pulse rising speed of 5 μs, a voltage of 5 kV _PP and a frequency of 5 kHz was applied between the electrodes, and the substrate film surface was subjected to glow discharge plasma processing. As a result, the discharge state was good, and the uniform treatment of the substrate film surface could be continuously performed for 1 hour. In addition, the electrode temperature is stable,
It was kept at ℃. If you do not spray fog water,
The temperature of the electrode reached 150 ° C. in 10 minutes.

[0034]

EFFECTS OF THE INVENTION The discharge plasma electrode of the present invention does not have a refrigerant conduit in the electrode and is provided with a mechanism for cooling the back surface of the electrode from the outside. Since it can be made lighter, the work can be done easily in terms of handling. Furthermore, the discharge plasma processing apparatus using the electrode of the present invention is an apparatus capable of stably and uniformly processing an object to be processed. Further, since the apparatus of the present invention can be carried out under atmospheric pressure, it can be easily inlined, and the method of using the apparatus of the present invention can improve the speed of the entire processing steps.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a cooling mechanism for a discharge plasma electrode of the present invention.

FIG. 2 is a diagram illustrating another example of the cooling mechanism for the discharge plasma electrode of the present invention.

[Explanation of symbols]

1 power supply 2, 3 parallel plate electrodes 4 discharge space 5 radiating fins 6 enclosure 7 nozzles 8 Atomized refrigerant

Claims (4)

[Claims] 1. A discharge plasma electrode having a cooling mechanism on the back surface of the discharge surface. 2. The discharge plasma electrode according to claim 1, wherein the cooling mechanism is a mechanism in which cooling fins made of metal protrusions are provided on the back surface of the discharge surface to increase the heat radiation area. 3. The discharge plasma electrode according to claim 1, wherein the cooling mechanism is a mechanism for spraying a mist-like coolant on the back surface of the discharge surface to radiate heat. 4. A discharge plasma in which an electric field is applied between a pair of electrodes, at least one of which is coated with a solid dielectric, a processing gas is introduced between the electrodes, and a substrate to be processed is treated with glow discharge plasma generated. In the processing apparatus, at least one of the electrodes is the discharge plasma electrode according to any one of claims 1 to 3, wherein the discharge plasma processing apparatus is characterized.