JPH10245206A - Discharging cell for ozone-generation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a discharging cell structure for ozone-generation apparatus effective for suppressing the contamination from a bonded part of a conductive spacer between a conductive part and a dielectric plate, etc., and suppressing the peeling and cracking of the bonding member and applicable to the production of semiconductor by using a bonded structure produced by thermally welding a fluororesin to a gas-contacting part including the discharging part. SOLUTION: This discharging cell for an ozone generation apparatus is provided with high-voltage plate electrodes 10a, 10b and a ground electrode 20 as discharging electrodes. These discharging electrodes are stacked one upon another in the direction of thickness and fastened with plural tie-rods 40 at the outer circumferential part. Discharging spaces 30a, 30b are formed between the high-voltage electrodes 10a, 10b and the ground electrode 20. The high-voltage electrode 10a at the side of the upper stage is provided with an insulation plate 12 on a heat-sink 11 and a dielectric material 13 bonded to the lower face of the insulation plate. The upper face of the dielectric material 13 is coated with a thin film. The bonding of the dielectric material 13 is carried out by thermally welding with a bonding medium composed of a fluororesin and the conductive thin film is also sealed at the circumference. The other electrodes have the same structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a discharge cell used in an ozone generator.

[0002]

2. Description of the Related Art As an ozone generator, a device in which a plurality of plate-shaped discharge cells are stacked in a plate thickness direction is known. Here, the plate-shaped discharge cell includes a pair of discharge electrodes, that is, a high-voltage electrode and a ground electrode, which are disposed to face each other with a predetermined gap therebetween, and a high voltage is applied between them to generate a silent discharge. In this state, by flowing a source gas such as oxygen during this time, oxygen in the source gas is ozonized to generate ozone gas.

In general, at least one of a high-voltage electrode and a ground electrode used as a discharge electrode in a plate-type discharge cell has a surface in contact with a discharge gap and a dielectric or electrode plate from the front side to the back side. And a heat sink.

As the dielectric, a ceramic having a large dielectric constant is coated on the surface of the electrode plate, and the one integrated with the electrode plate is often used on the surface of the heat sink.

[0005] Meanwhile, while the ozone generator is used for various chemical treatments, it has begun to be used for manufacturing semiconductors. In the manufacture of semiconductors, ozone is used for forming an oxide film, ashing a resist, cleaning a silicon wafer, and the like. In the case of the ozone generator used for these, it is necessary to generate pure ozone gas with very little contamination (metal impurities + particles). For this reason, it has become necessary to use a high-purity, high-corrosion-resistant material for the gas contact members of the discharge cells and the piping.

In particular, from the viewpoint of preventing the occurrence of contamination due to sputtering in the discharge portion of the discharge cell,
It has become necessary to switch from an integrated dielectric in which the surface of an electrode plate is coated with ceramic to a single-plate dielectric made of a ceramic plate having high purity and good plasma resistance or a single crystal plate such as sapphire.

When a ceramic plate or a single crystal plate such as sapphire is used as the dielectric, a conductive thin film 2 is formed on the back surface of a plate-like dielectric 1 as shown in FIG. One having a structure in which it is coated and bonded to the surface of a heat sink 3 also serving as a current-carrying member with an adhesive 4 is used. As the adhesive 4, an epoxy resin room temperature adhesive or a thermosetting adhesive is used from the viewpoint of adhesive strength and ease of use. Then, the two electrodes are fastened by a plurality of tie rods via the insulating spacer 5 to form a discharge gap 6 between the two electrodes.

[0008]

However, a discharge cell for an ozone generator using such a discharge electrode has the following problems.

When assembling the discharge cell, if the discharge electrodes are fastened in the stacking direction with a spacer interposed between the opposing dielectrics 1, there is a risk that the plate-like dielectrics 1, 1 may be cracked. Therefore, the heat sink 3 also serving as a current-carrying member has a larger area than the dielectric 1 disposed on the surface thereof, and the upper and lower heat sinks 3 sandwiching the insulating spacer 5 disposed on the outer edge side of the dielectric 1. It is considered that a configuration in which 3 is tightened by a tie rod in the stacking direction is preferable.

However, in the case of such a laminated structure, the ozone gas generated in the discharge gap 6 comes into contact with the conductive thin film 2 coated on the side end surface of the dielectric 1 and the back surface thereof, and from the thin film 2, contamination occurs. , There is a risk that the purity of the ozone gas is reduced.

When the dielectric material 1 is alumina, its coefficient of thermal expansion is 70 × 10 ⁻⁷ / ° C., whereas the heat sink 3 also serving as a current-carrying member is usually made of an aluminum alloy having good thermal conductivity. The coefficient of thermal expansion is 220 × 10 ⁻⁷ / ° C. Due to such a large difference in the coefficient of thermal expansion, the dielectric 1
Also, there is a danger that the dielectric 1 will be cracked even if it peels off and does not peel off.

The adhesive 4 causes contamination, and the use of the ozone generator may be restricted depending on the required purity of the ozone gas.

An object of the present invention is to provide a discharge cell for an ozone generator capable of suppressing the generation of contamination from a bonding portion and, at the same time, preventing peeling and cracking of a bonding member.

[0014]

In the discharge cell for an ozone generator according to the present invention, an adhesive structure is adopted in at least a part of a gas contact part including a discharge part, and the adhesive structure is a fluororesin-based material as an adhesive medium. Characterized in that it is a heat welding structure using

As a specific bonding structure, for example, at least one of a pair of discharge electrodes is formed in a plate shape having a surface opposed to a discharge gap and a conductive thin film coated on a portion other than an outer edge of a back surface. A dielectric, a heat sink serving also as a current-carrying member disposed on the back side of the dielectric, a conductive spacer disposed between the heat sink and the thin film, and a dielectric for bonding the dielectric and the heat sink. And a heatsink, and a portion of the thin film located on the outer edge side of the thin film and a portion excluding the spacer between the thin film and the heat sink.

The fluororesin-based adhesive medium preferably has a molecular structure called Teflon (trade name) in which carbon atoms are surrounded by fluorine atoms.
A or FEP is preferable because of good fluidity at the time of melting.

In the discharge cell for an ozone generator according to the present invention,
As a bonding structure in a gas contact part including a discharge part, a heat welding structure using a fluororesin system as a bonding medium is adopted. For this reason, also in the bonding part of the discharge part such as the bonding part of the dielectric, the occurrence of contamination is prevented, and the peeling or cracking of the bonding member is also prevented. This will be described below with reference to the specific bonding structure described above.

In this bonding structure, a conductive thin film is coated on the back surface of the dielectric material except for the outer edge portion, and the dielectric material is coated on the surface of the heat sink with a conductive spacer disposed between the thin film and the heat sink. It is thermally welded by a fluororesin-based adhesive medium. Here, the adhesive medium is a portion between the dielectric and the heat sink located on the outer edge side of the thin film,
And a portion excluding the spacer between the thin film and the heat sink.

According to such an adhesive structure, the periphery of the conductive thin film coated on the back surface of the dielectric is sealed by the fluororesin-based adhesive medium. Even in the case of a cell configuration in which the dielectric member is located inside the fastening portion by being fastened in the stacking direction, the generation of contamination from the thin film is prevented. By locating the dielectric inside the fastening portion, cracking of the dielectric due to the fastening is prevented.

The fluororesin-based adhesive medium has flexibility,
In addition, the thickness variation is reduced by the conductive spacer disposed between the thin film and the heat sink. Therefore, peeling or cracking of the dielectric due to a difference in thermal expansion between the dielectric and the heat sink is prevented. Also, the spacer provides good electrical conductivity between the two. Furthermore, the generation of contamination from the adhesive medium itself is small.

The bonding structure according to the present invention is not limited to the bonding of a dielectric in a plate cell, the bonding of a dielectric in a cylindrical cell, and the bonding between members in a cell. The present invention can be applied to all kinds of joints that need to suppress the generation of contamination.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show one embodiment of the present invention.

The ozone generator discharge cell of this embodiment is
As shown in FIGS. 1 and 2, a plate-shaped high-voltage electrode 10a, a ground electrode 20, and a high-voltage electrode 10b are provided as discharge electrodes. These discharge electrodes are stacked in the thickness direction,
A plurality of tie rods 40, 40,.
・ Tightened by The ground electrode 20 sandwiched between the upper high-voltage electrode 10a and the lower high-voltage electrode 10b
Forms a discharge gap 30a with the upper high voltage electrode 10a, and forms a discharge gap 30b with the lower high voltage electrode 10b.

That is, this ozone generator discharge cell is composed of an upper cell composed of an upper high-voltage electrode 10a and a ground electrode 20, and a lower cell composed of a ground electrode 20 and a lower high-voltage electrode 10b. It has a two-stage structure that is superimposed on each other. The bonding structure between the dielectric and the heat sink, which is unique to the present invention, is formed by the upper and lower high-voltage electrodes 10a and 10b.
And ground electrode 20 shared between upper cell and lower cell
Has been adopted.

Hereinafter, the upper cell will be described. The lower cell has the same configuration as the upper cell except that it is vertically symmetrical. When describing the upper cell, the surface of the high-voltage electrode 10a is the lower surface, and the surface of the ground electrode 20 is the upper surface.

The high-voltage electrode 10a includes a thick heat sink 11, an insulating plate 12 disposed below the heat sink 11, and an insulating plate 1
2 and a dielectric 13 bonded to the lower surface. Dielectric 1
The upper surface of 3 is coated with a conductive thin film 14 except for the outer edge. A conducting wire 15 for applying a high voltage is electrically connected to the upper surface of the thin film 14.

The heat sink 11 is made of a thick plate of an aluminum alloy or the like, and is forcibly cooled by cooling water supplied therein. The insulating plate 12 is made of, for example, an alumina thin plate having a thickness of 4 mm. The insulating plate 12 is substantially the same as the heat sink 11 in order to provide insulation between the heat sink 11 and the thin film 14 and provide insulation between the high voltage electrode 10a and the ground electrode 20. That's it. The dielectric 13 bonded to the lower surface of the insulating plate 12
It is made of a thinner ceramic plate or a single crystal plate such as sapphire having a thickness of 0.6 mm, for example, and is narrower than the insulating plate 12 so as to be located inside the fastening portion between the high voltage electrode 10a and the ground electrode 20. The thin film 14 coated on the upper surface of the dielectric 13 is made of silver metallized mainly containing silver. The coating range of the thin film 14 is dielectric 1
The width smaller than 3 is as described above.

The dielectric 13 is bonded to the ground electrode 2 described later.
As in the case of bonding the dielectric 23 at 0, the conductive thin film is bonded to the lower surface of the insulating plate 12 by thermal welding using a fluororesin-based bonding medium and formed on the upper surface excluding the outer edge of the dielectric 13. 14 is sealed from the surroundings by an adhesive medium. Unlike the heat sink, the insulating plate 12 has a coefficient of thermal expansion close to that of the dielectric 13. Further, no conductivity is required between the thin film 14 and the insulating plate 12. For this reason, a conductive spacer used for bonding the dielectric 23 to the ground electrode 20 is not used.

The conductor 15 is, as shown in FIG.
And is drawn out above the heat sink 11 through through holes provided in the heat sink 11 and the insulating plate 12. In the through hole, the heat sink 11
An insulating sleeve 16 is inserted in order to prevent an electrical short circuit between the wire and the conductor 15. Incidentally, 19, 2 in the figure
9 is a passage for cooling water formed in the heat sinks 11 and 21, respectively.

On the other hand, the ground electrode 20 is connected to the heat sink 11
Is provided. Heat sink 2
Reference numeral 1 denotes a thick plate made of an aluminum alloy or the like, similar to the heat sink 11, and is forcibly cooled by cooling water supplied to the inside. The upper surface of the heat sink 21 is recessed downward except for the outer edge. A dielectric 23 corresponding to the dielectric 13 is adhered to the bottom surface of the recess 22. The depth of the concave portion 22 is determined by the dielectrics 13 and 23 opposed to each other across the discharge gap 30a.
It is set to be able to accommodate.

The dielectric 23 is made of an extremely thin plate such as ceramic or sapphire, like the dielectric 13. Dielectric 23
As shown in FIGS. 4 and 5, a conductive thin film 24 made of silver metallized or the like corresponding to the thin film 14
, Except for the outer edges. And
The dielectric 23 is thermally welded to the bottom of the recess 22 by a fluororesin-based adhesive medium 26 with a plurality of conductive spacers 25 interposed between the bottom of the recess 22 and the thin film 24. Have been.

As a result, the adhesive medium 26 is formed between the dielectric 23 and the heat sink 21 at the portion located on the outer edge of the thin film 24 and at the portion excluding the spacers 25 between the thin film 24 and the heat sink 21. The dielectric 23 is mechanically bonded and fixed to the upper surface of the heat sink 21 with each interposed therebetween. Each spacer 25 is made of a thin aluminum plate or the like, and secures electrical conduction between the thin film 24 and the heat sink 21.

Here, a method of manufacturing the ground electrode 20 will be described with reference to FIG.

One surface of the dielectric 23 is coated with a conductive thin film 24 by silver metallization or the like. On the heat sink 21, a fluorine-based resin sheet 26 ′ serving as an adhesive medium 26 and spacers 25 are placed. In the resin sheet 26 ', holes corresponding to the spacers 25, 25,.
Fits into this hole. The thickness of the resin sheet 26 'is larger than the thickness of the spacers 25, 25... For example, when the thickness of the spacers 25, 25. 1
mm or more is suitable.

The dielectric 23 is placed on the resin sheet 26 'with the thin film 24 facing down, and a pressure plate (not shown) is placed thereon. While pressing in the stacking direction,
The laminate is heated to a temperature equal to or higher than the melting point of the resin sheet 26 '.

Thus, the dielectric 23 is thermally welded to the upper surface of the heat sink 21. Specifically, as shown in FIG. 4, the portion of the dielectric 23 located on the outer edge side of the thin film 24 is bonded to the upper surface of the heat sink 21 by the bonding medium 26. .. Of the thin film 24 are adhered to the upper surface of the heat sink 21 by an adhesive medium 26. Then, the thin film 24 is formed of spacers 25 and 2.
5 are electrically connected to the heat sink 21.

When the ground electrode 20 is manufactured, as shown in FIGS. 1 and 2, the insulating plate 12 having the dielectric 13 adhered to the lower surface is placed on the heat sink 21 of the ground electrode 20.
Further, a heat sink 11 is placed thereon, and the heat sink 1
With the outer edge portion of the insulating plate 12 sandwiched between the outer edge portions of the stacks 1 and 21, the outer edge portion of the laminate is fastened in the stacking direction by tie rods 40, 40.

The dielectrics 13 and 23 are accommodated in the concave portion 22 formed on the upper surface of the heat sink 21 so as to face each other across the discharge gap 30a. The inside of the recess 22 is the insulating plate 1
The periphery is sealed by an annular seal ring 70 interposed between the heat sink 2 and the heat sink 21. The inside of the recess 22 is also connected to gas pipes 50 and 60 via gas holes 27 provided in the heat sink 21.

The configuration of the upper cell has been described above. The lower cell, which is vertically symmetrical to the upper cell, is constituted by the ground electrode 20 and the lower high-voltage electrode 10b. The two-stage ozone generator discharge cell is used as follows.

A predetermined high voltage (for example, 3000 V) is applied to the conductive thin films 14, 14 of the high-voltage electrodes 10a, 10b via the conductive wires 15, 15 in a state where the cooling water flows through the heat sinks 11, 21, 11. By doing so, the dielectric 1
Silent discharge is generated in discharge gaps 30a and 30b formed between the electrodes 3 and 23 and between the dielectrics 23 and 13. In this state, from the gas pipe 50 through the gas holes 27, the concave portions 22, 22 are formed.
A high-purity oxygen gas is introduced therein as a source gas.

The introduced oxygen gas is supplied to the discharge gaps 30a, 30
In the process of passing through Ob, it is exposed to silent discharge and becomes ozonized. Thereby, the ozone gas is led out of the cell from the gas pipe 60 through the gas hole 27.

The advantages of such a discharge cell for an ozone generator over a conventional cell are as follows.

In the high-voltage electrodes 10a and 10b, an insulating plate 12 is interposed between the thin film 14 and the heat sink 11. Therefore, the cooling water flowing through the heat sink 11 is electrically insulated from the thin film 14 to which a high voltage is applied, and the potential difference between the cooling water and the cooling water flowing through the heat sink 21 on the side of the ground electrode 20 is set. Does not occur. For this reason, it becomes possible to use ordinary industrial water or the like as the cooling water.

The insulating plate 12 comprises heat sinks 11 and
Since it is interposed between 1 and also serves as an insulating member during this time,
No insulating member is required during this time. Since the concave portion 22 for accommodating the dielectrics 13 and 23 is formed on the surface of the heat sink 21, a spacer between the heat sinks 11 and 21 is not required. Since the insulating plate 12 is held between the heat sinks 11 and 21, there is no need to bond the insulating plate 12 to the heat sink 11. Thus, increase in the number of parts and the number of manufacturing steps can be avoided.

Since the dielectrics 13 and 23 are accommodated in the recess 22 and do not intervene in the fastening portions of the heat sinks 11 and 21, there is no danger that the dielectrics 13 and 23 will be broken even if the fastening is performed strongly. And with this strong tightening,
Sufficient sealing performance in the recess 22 is ensured.

Ozone generated by the dielectrics 13 and 23 being accommodated in the recesses 22 is generated by the dielectrics 13 and 23.
Contacts the side end surface of However, since the conductive thin films 14 and 24 coated on the back surfaces are sealed around by a fluororesin-based adhesive medium 26, ozone does not come into contact with these side end surfaces. Therefore, the thin films 14, 24
The generation of contamination from the air is prevented. Also,
There is no generation of contamination from the adhesive medium 26 due to contact with ozone. Therefore, a decrease in the purity of the ozone gas due to these is prevented. This effect is particularly large when the adhesive medium 26 is PFA.

In the ground electrode 20, a dielectric 23 having a small coefficient of thermal expansion is bonded to the surface of a heat sink 21 having a large coefficient of thermal expansion. , 25... Ensure a sufficient thickness and reduce the variation in the thickness, so that the difference between the two coefficients of thermal expansion is effectively absorbed. Therefore, despite the fact that the dielectric 23 is adhered to the surface of the heat sink 21, the dielectric 23 does not peel or crack due to the difference in the coefficient of thermal expansion.

The dielectric 23 is not only a portion located on the outer edge side of the thin film 24 coated on the back surface of the dielectric 23 but also a spacer 25 between the thin film 24 and the heat sink 21.
The parts other than 25 are also adhered to the heat sink 21. Further, as the adhesive medium 26, a fluororesin system having high ozone resistance is used. For these,
The adhesion durability of the dielectric 23 is excellent.

Since the spacers 25 are interposed between the thin film 24 and the heat sink 21, despite the fact that the space is adhered by a sufficiently thick fluororesin-based adhesive medium 26, the spacers 25 are interposed between them. Sufficient electrical conductivity is provided.

Due to such advantages, the discharge cell for the ozone generator of this embodiment is less contaminated and clean than the conventional cell. for that reason,
It is particularly suitable for an ozone generator for semiconductor production that requires high-purity ozone gas. In addition, the discharge cell for an ozone generator is excellent in durability and economical.

The discharge cell for the ozone generator of this embodiment has a structure in which the upper cell and the lower cell are integrally laminated.
Although it has a step structure, it goes without saying that a discharge cell having a one-step structure may be used. Further, the bonding structure of the dielectric and the heat sink unique to the present invention is employed on the side of the ground electrode. However, it is naturally possible to employ the adhesive structure on the side of the high voltage electrode or on both the high voltage electrode and the ground electrode. Further, one spacer may be used for the bonding structure.

[0052]

As is clear from the above description, the discharge cell for an ozone generator of the present invention has a heat-welded structure using a fluororesin as an adhesive medium as an adhesive structure at a gas contact portion including a discharge portion. By adopting this, it is possible to prevent the occurrence of contamination and to prevent the adhesive member from peeling or cracking even at the bonding portion in the discharge portion such as the bonding portion of the dielectric.

In a state where a conductive thin film is coated on a portion except for the outer edge of the back surface of the dielectric, and a plurality of conductive spacers are dispersed between the thin film and the heat sink,
By adopting an adhesive structure in which the dielectric is heat-welded to the surface of the heat sink with a fluororesin-based adhesive medium, even in the case of a cell configuration where the dielectric is located inside the fastening part, the contamination from the thin film or the adhesive medium is reduced. Generation can be prevented. Further, it is possible to prevent the dielectric material from peeling or cracking due to a difference in thermal expansion between the dielectric material and the heat sink.
Further, despite the configuration in which the thin film is bonded to the heat sink, good electrical conductivity can be provided between the two.

That is, the discharge cell of the present invention solves the problem when a pure ceramic plate or a single crystal plate such as sapphire is used as a dielectric, and provides a clean ozone generator which does not hinder the purity. This makes it possible to increase the durability of the ozone generator.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a discharge cell for an ozone generator showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is an enlarged view of a portion B in FIG. 1;

FIG. 4 is a schematic vertical sectional view of a ground electrode showing a main configuration of an embodiment of the present invention.

FIG. 5 is a schematic plan view of the ground electrode.

FIG. 6 is a schematic perspective view for explaining a method of manufacturing the ground electrode.

FIG. 7 is a schematic vertical sectional view of a conventional discharge cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10a, 10b High voltage electrode 11 Heat sink 12 Insulating plate 13 Dielectric 14 Thin film 15 Conductor 16 Insulating sleeve 20 Ground electrode 21 Heat sink 22 Depression 23 Dielectric 24 Thin film 25 Spacer 26 Adhesive medium 26 'Resin sheet used as an adhesive medium 30a, 30b Discharge gap 40 Tie rod 50,60 Gas pipe 70 Seal ring

Claims (3)

[Claims] 1. An ozone generator, wherein an adhesive structure is adopted in at least a part of a gas contact part including a discharge part, and the adhesive structure is a heat welding structure using a fluororesin as an adhesive medium. Discharge cell for device. 2. A pair of discharge electrodes facing each other with a predetermined gap to form a discharge gap for ozone generation, wherein at least one of the pair of discharge electrodes has a front surface facing the discharge gap and a back surface. A plate-shaped dielectric body coated with a conductive thin film on a portion excluding the outer edge of the heat sink, a heat sink serving also as a current-carrying member disposed on the back side of the dielectric, and a conductive body disposed between the heat sink and the thin film. Fluororesins provided on the portion of the thin film between the dielectric and the heat sink, on the outer edge side of the thin film, and on the portion excluding the spacer between the thin film and the heat sink to bond the dielectric spacer and the heat sink. The discharge cell for an ozone generator according to claim 1, further comprising a system-based adhesive medium. 3. The fluororesin-based adhesive medium is PFA or F
The discharge cell for an ozone generator according to claim 1 or 2, wherein the discharge cell is an EP.