JP2004209373A - Method for starting electric discharge, treating method and treating apparatus in which the starting method is used for matter to be treated - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for starting electric discharge, wherein plasma can be easily generated when starting or restarting of the discharge, and a treating method and a treating apparatus in which the discharge-starting method is used. <P>SOLUTION: In the discharge starting method, a uniform water-membrane is formed in a reaction flow-path by overflowing water from the periphery of a long and narrow tubular reaction flow-path. A discharge is generated between a high voltage electrode in the air and a ground electrode in the water-membrane. When starting discharge or reignition, an electric circuit of a low resistance is formed through an electrolytic solution between the high voltage electrode and the ground electrode in the water membrane. Supply of the electrolytic solution is suspended, and the discharge of a prescribed duration or reignition is performed by breaking the current circuit between the high-voltage electrode and the ground electrode. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for starting a discharge between a high-voltage electrode and a ground electrode, a method for treating an object using the method for starting discharge, and an apparatus for treating an object using the method for starting.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a method of treating a harmful substance by decomposing a gas component using plasma has been proposed.
For example, Patent Document 1 proposes a method of supplying a gas between opposed electrodes.
Patent Documents 2 and 3 propose a method in which plasma is generated between a cylindrical case and a discharge wire suspended in the case, and gas is supplied into the case.
However, it is difficult for any of the above-mentioned conventional methods to generate plasma over the entire cross section of the reaction channel through which the gas passes.
Therefore, the present inventors have found a method for forming a plasma over the entire cross section of the reaction channel by securing a predetermined length of the reaction channel and generating plasma in the axial direction of the reaction channel.
[0003]
[Patent Document 1]
JP-A-11-156156 [Patent Document 2]
JP-A-5-15737 [Patent Document 3]
JP-A-7-47224
[Problems to be solved by the invention]
However, in order to generate plasma of a predetermined length in the axial direction of the reaction channel, the high-voltage electrode and the ground electrode must be brought close to each other at the time of starting, and the high-voltage electrode and the ground electrode must be separated after the plasma is generated. Providing a mechanism for changing the distance between them not only increases the cost but also has the problem that the plasma becomes unstable due to the movement of the electrodes.
[0005]
Therefore, the present invention provides a method of starting a discharge that can easily generate plasma at the time of starting or restarting a discharge, a method of treating an object using the method of starting a discharge, and a method of using the method of starting. An object of the present invention is to provide a processing device for a processed product.
[0006]
[Means for Solving the Problems]
In the method for starting discharge according to the present invention, a uniform water film is formed in the reaction flow channel by overflowing from the outer periphery of the tubular elongated reaction flow channel, and the high-pressure electrode and air in the air are formed. A method for initiating a discharge that causes a discharge between a ground electrode in a film and a start of discharge or a re-ignition, between the high-voltage electrode and the ground electrode in the reaction channel. Once a low-resistance current path is formed by the electrolytic solution, the supply of the electrolytic solution is stopped, and the current path between the high-voltage electrode and the ground electrode is interrupted to start discharge or re-ignite. It is characterized by
The discharge starting method according to the present invention according to claim 2, wherein a high-voltage electrode is disposed on one side and a ground electrode is disposed on the other side, and a current flow path is formed between the vicinity of the high-voltage electrode and the ground electrode. Or, at the time of restart, after applying a voltage to the high-voltage electrode, by causing the electrolyte to flow into the flow path, a short distance discharge is started between the high-voltage electrode and the electrolyte, and the flow of the electrolyte is stopped. By doing so, a discharge of a predetermined length is obtained.
According to a third aspect of the present invention, in the discharge starting method according to the first or second aspect, plasma is generated by arc discharge.
In the method for treating an object to be treated according to the present invention, an elongated reaction channel having a tubular shape through which the object passes, a high-voltage electrode disposed above the reaction channel, A ground electrode disposed on the lower side, wherein a plasma is generated in the axial direction of the reaction channel to process the workpiece such as chlorofluorocarbons. In some cases, the electrolytic solution is caused to flow from above the reaction channel, and after the voltage is applied to the high-voltage electrode, the flowing of the electrolytic solution is stopped.
According to a fifth aspect of the present invention, in the method for treating an object to be treated according to the fourth aspect, a water reservoir is formed on an outer peripheral portion of the reaction channel, and water in the water reservoir is supplied to the reaction channel. It is characterized by.
According to a sixth aspect of the present invention, in the method for processing an object to be processed according to the fourth aspect, plasma is generated by arc discharge.
The treatment device for treating an object according to the present invention according to claim 7 is a tubular elongated reaction channel through which the object passes, a high-pressure electrode disposed at one end of the reaction channel, A ground electrode disposed on the other end side, a water supply pipe for supplying water into the reaction channel from above the reaction channel, and discharging water from the reaction channel from below the reaction channel. And a nozzle for supplying an electrolytic solution into the reaction channel from above the reaction channel.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The method of starting discharge according to the first embodiment of the present invention is characterized in that, at the start of discharge or at the time of re-ignition, the electrolytic solution is once interposed between the high-voltage electrode and the ground electrode in the water film in the reaction channel. After forming the low-resistance current path, the supply of the electrolytic solution is stopped, and the current path between the high-voltage electrode and the ground electrode is interrupted to start discharge or re-ignite. . According to the present embodiment, the same effect as that of short-circuiting the electrodes can be obtained by injecting the electrolytic solution without requiring any movement of the electrodes. That is, when the electrolytic solution flows toward the water film in the reaction channel from or near the high-voltage electrode, the leading end of the electrolytic solution descends together with the water in the water film, and the leading end of the electrolytic solution flows into the water film. When the water electrode reaches the ground electrode in the film, the electric resistance of the water film decreases, so that the high-voltage electrode and the ground electrode move as if they were moving to the top end of the water film, and current flows from the high-voltage electrode to the ground electrode. Flows. If the injection of the electrolytic solution is immediately stopped at this time, an induced voltage is generated between the high-voltage electrode and the electrolytic solution, and the discharge starts. The overflowing water causes the electrolyte to go down, so the discharge length becomes longer, as if the ground electrode were being lowered.When the electrolyte passed away from the water film, it reached a predetermined length. Is obtained. When the electrolyte is injected toward the high-voltage electrode, the same effect as when the electrode is short-circuited is obtained.In any case, the same effect as when the electrode is moved without moving the electrode is obtained. Will be done. In particular, the intervening water makes it easy to clean up the injection of the electrolytic solution.
The method of starting discharge according to the second embodiment of the present invention is characterized in that, at the time of starting or restarting discharge, after applying a voltage to the high-voltage electrode, the electrolytic solution is caused to flow into the flow path, so that the high-voltage electrode and the electrolytic solution are separated. To start a short-distance discharge and stop the flow of the electrolyte to obtain a discharge of a predetermined length. According to the present embodiment, when the discharge is started or restarted, the supply of the electrolytic solution forms a path through which a current flows between the high-voltage electrode and the ground electrode. Can be generated. When the supply of the electrolytic solution is stopped, the electrolytic solution no longer exists between the high-voltage electrode and the ground electrode, but the discharge is continued.
According to a third embodiment of the present invention, in the discharge starting method according to the first or second embodiment, plasma is generated by arc discharge. According to the present embodiment, more stable plasma can be generated.
In the method for treating an object to be treated according to the fourth embodiment of the present invention, at the start of discharge or at the time of restart, the electrolyte flows in from the upper side of the reaction channel, and after the voltage is applied to the high voltage electrode, the flow of the electrolyte flows. Is to stop. According to the present embodiment, when the discharge is started or restarted, the supply of the electrolytic solution forms a path through which a current flows between the high-voltage electrode and the ground electrode. Can be generated. When the supply of the electrolytic solution is stopped, the electrolytic solution no longer exists between the high-voltage electrode and the ground electrode, but the discharge is continued. In addition, since plasma is formed in the entire cross section of the reaction channel by forming plasma in the longitudinal direction of the reaction channel, the object to be processed is affected by the plasma while passing through a long distance in a narrow cross section. Therefore, the decomposition efficiency of the object to be treated increases.
According to a fifth embodiment of the present invention, there is provided a method for treating an object to be processed according to the fourth embodiment, wherein a water reservoir is formed on an outer peripheral portion of a reaction channel and water in the water reservoir is supplied to the reaction channel. It is. According to the present embodiment, it is possible to prevent the wall surface temperature of the reaction channel from excessively rising, and thus prevent the water flowing down the inner wall of the reaction channel from evaporating in the middle of the reaction channel. be able to. Therefore, since the inner wall of the reaction channel is always covered with the water film, the erosion of the inner wall of the reaction channel can be prevented.
According to a sixth embodiment of the present invention, in the method for processing an object to be processed according to the fourth embodiment, plasma is generated by arc discharge. According to the present embodiment, more stable plasma can be generated.
The method for treating an object to be processed according to the seventh embodiment of the present invention comprises a tubular elongated reaction channel through which the object passes, a high-pressure electrode disposed at one end of the reaction channel, A ground electrode disposed on the other end side, a water supply pipe for supplying water into the reaction flow path from above the reaction flow path, and a discharge pipe for discharging water from the reaction flow path from below the reaction flow path. And a nozzle for supplying an electrolytic solution into the reaction channel from above the reaction channel. According to the present embodiment, since water is supplied near the plasma, water-soluble reaction products in the exhaust gas can be quickly eliminated, and the decomposition reaction can be promoted. In addition, by supplying the electrolytic solution along the flow of water, a path through which a current flows is formed between the high-voltage electrode and the ground electrode, so that plasma can be easily generated. In addition, by forming plasma in the axial direction of the reaction flow path, plasma is formed in the entire cross section of the reaction flow path, so that the exhaust gas is affected by the plasma while passing a long distance in a narrow cross section, Exhaust gas decomposition efficiency is increased.
[0008]
【Example】
Hereinafter, a discharge starting method according to an embodiment of the present invention will be described with reference to a processing apparatus and a processing method for an object to which the starting method is applied.
The object to be treated in the present invention is, for example, a gas mainly containing a halogen element, specifically, a PFC gas such as CF ₄ (Freon 14) or C ₄ F ₈ (Freon 318), and CxHyFz. , CxHyClz, CxFyClz, CwFxClyBrz, SF ₆ , NF ₃ , CCl _{4 and the} like (w, x, y, and z are integers). Further, the present invention can also treat various other harmful gases and solid or liquid harmful substances as objects to be treated.
The processing apparatus of the present invention is applied as a plasma facility for decomposing and processing harmful substances discharged from a dry etching apparatus for manufacturing semiconductors. The present invention is also applied to a plasma processing apparatus for decomposing a cleaning gas used for cleaning a PVD apparatus or a CVD apparatus.
The object processing apparatus of the present invention is used in an environment where plasma discharge is performed under substantially atmospheric pressure. The object processing apparatus of the present invention uses arc discharge having a low sustaining voltage.
[0009]
FIG. 1 is a main part configuration diagram of an apparatus for processing an object to be processed according to an embodiment of the present invention.
At the upper part of the hollow main body case 10, an introduction pipe 17 for introducing harmful substances such as exhaust gas to be treated into the main body case 10 is provided. This introduction pipe 17 is, for example, an exhaust pipe 18 of a roughing pump. It is connected to the.
At the lower end of the main body case 10, a discharge port 10c for communicating the inside and the outside of the main body case 10 is formed. Further, a cooling water passage 9 for supplying water into the outlet 10c is provided at a lower end portion of the main body case 10.
Inside the main body case 10, a hollow reaction pipe 3 having a predetermined length is vertically attached to the upper end of the outlet 10 c, and the reaction pipe 3 forms a tubular or cylindrical elongated reaction channel 13. are doing. The inner diameter of the reaction pipe 3 is preferably about 8 to 30 mm for forming plasma over the entire cross section of the reaction channel 13. In particular, an inner diameter of about 20 mm is suitable for efficiently processing harmful substances. In addition, Pyrex (registered trademark) glass can be used for the reaction pipe 3, but other insulators such as alumina, aluminum nitride, silicon nitride, silicon carbide, and boron nitride are suitable.
At the lower end inside the reaction pipe 3, a ground electrode 11 is provided along the inner surface of the reaction pipe 3. For the ground electrode 11, for example, a metal having high conductivity such as brass or copper is suitable, and a metal having high conductivity and being chemically stable, such as gold or platinum, is more suitable. However, the present invention is not limited to these as long as it can exhibit the function of causing
[0010]
At the upper end of the main body case 10, a high-voltage electrode 12 whose tip is made of a platinum alloy is provided. The lower end of the high-voltage electrode 12 is disposed near the upper end of the reaction pipe 3. A power supply 14 is connected to the upper end of the high-voltage electrode 12 via a matching circuit 15. The power supply 14 is an AC high-frequency power supply. When the DC power supply 14 is a DC high-voltage power supply, the matching circuit 15 is unnecessary.
Although the high-voltage electrode 12 is arranged on the center line near the inflow side of the reaction channel 13, the end of the high-voltage electrode 12 may be inserted into the reaction channel 13.
The distance between the ground electrode 11 and the high voltage electrode 12 is preferably 200 mm or more, and more preferably 250 mm or more.
Further, a nozzle 21 for supplying an electrolytic solution is provided at an upper end of the main body case 10. As the electrolytic solution, for example, NaCl, NaOH, H ₂ SO ₄ , HNO ₃ can be used. The nozzle 21 is provided toward the tip of the high-voltage electrode 12 or the upper end opening of the reaction pipe 3. The electrolyte supply unit 22 supplies an electrolyte discharged from the nozzle 21 to the nozzle 21. The supply of the electrolytic solution supply unit 22 is controlled by the control unit 23.
A water reservoir 8 is formed between the outer periphery of the reaction pipe 3 and the inner surface of the main body case 10 so as to surround the reaction pipe 3. A water supply pipe 16 is provided in the main body case 10, and the water supply pipe 16 supplies water to the water reservoir 8. The water supplied to the water reservoir 8 is supplied into the reaction pipe 3 from the upper end of the water reservoir 8.
[0011]
Hereinafter, the operation of the processing apparatus of the present embodiment will be described.
At the start of discharge or at the time of restart, the electrolytic solution is supplied from the electrolytic solution supply unit 22 according to a signal from the control unit 23, and the electrolytic solution is discharged from the nozzle 21. The electrolytic solution discharged from the nozzle 21 flows down into the reaction passage 13 through the high voltage electrode 12 or near the lower part of the high voltage electrode 12, and passes through the ground electrode 11.
After a predetermined time has elapsed after the start of the supply of the electrolytic solution, a high voltage is applied to the high voltage electrode 12 from the power supply 14 by a signal from the control unit 23. Since a path through which a current flows is formed between the high-voltage electrode 12 and the ground electrode 11 by the continuously dropped electrolytic solution, after the high voltage is applied from the power supply 14, When the supply of the electrolyte from the electrolyte supply unit 22 is stopped by the signal and the discharge of the electrolyte from the nozzle 21 is also stopped, plasma is easily generated.
When the supply of the electrolyte is stopped, the electrolyte does not exist between the high-voltage electrode 12 and the ground electrode 11, but the discharge is continued, and the plasma formed on the entire cross section of the reaction channel 13 is in a stable state. Is maintained in. The voltage may be applied to the high-voltage electrode 12 before the supply of the electrolytic solution, or the voltage may be applied when the supply of the electrolytic solution is stopped after the electrolytic solution reaches the ground electrode 11.
[0012]
Water supplied from the water supply pipe 16 to the water reservoir 8 is supplied into the reaction pipe 3 from the upper end opening of the reaction pipe 3. The water supplied into the reaction pipe 3 flows down along the inner wall of the reaction pipe 3 and forms a water film on the entire inner wall of the reaction pipe 3.
On the other hand, the workpiece is introduced into the main body case 10 from the exhaust pipe 18 via the introduction pipe 17. The object to be treated introduced into the main body case 10 comes into contact with the plasma when passing through the inside of the reaction pipe 3 and is decomposed into respective gas components. At this time, since the plasma fills the entire cross-section in the reaction channel, the gas does not pass through the plasma, and is efficiently decomposed into gas components. In particular, a fluorine compound such as PFC containing CF ₄ is very stable, so that an ordinary treatment method is useless, but it can be effectively decomposed by contacting the plasma with a narrow space for a sufficient time.
The decomposed water-soluble reaction product is absorbed by water flowing down along the inner wall of the reaction pipe 3. The decomposed water-soluble reaction product is released to the outside of the main body case 10 together with water.
[0013]
By using platinum as the high voltage electrode 12, the surface of the high voltage electrode 12 can be kept chemically stable. Therefore, it is possible to prevent the high-voltage electrode 12 from being corroded by harmful substances.
Further, if water is supplied from the cooling water passage 9 to the discharge port 10c, the water-soluble reaction products discharged from the reaction flow path 13 can be efficiently absorbed and removed by water, and the exhaust side of the apparatus is reduced. Damage due to heat can be prevented.
At the start of the discharge, if a pulse voltage higher than the discharge start voltage is applied to the ground electrode 11 or the high voltage electrode 12, the discharge can be started stably from the moment the pulse voltage is applied.
Further, at the start of discharge, if a high-frequency voltage higher than the discharge start voltage is applied to the ground electrode 11 or the high-voltage electrode 12, the discharge can be started stably, and the applied voltage at the start of discharge can be reduced. it can.
Furthermore, if a DC voltage is applied between the ground electrode 11 and the high-voltage electrode 12 to cause a discharge, a constant voltage can always be applied between the ground electrode 11 and the high-voltage electrode 12, so that the discharge is performed over the entire time period. Can be stabilized. In particular, when a negative voltage is applied to the high voltage electrode 12, the discharge can be further stabilized.
Further, the high voltage electrode 12 may use platinum only at the tip. The high-voltage electrode 12 is not particularly limited as long as it can exert a function of generating plasma, such as a metal pipe, a metal rod, a carbon rod, or a Ti-Pd alloy rod.
[0014]
In addition, since a water film is formed on the entire inner wall of the reaction channel 13, the plasma and water come into contact over a wide area. Therefore, the water vapor generated by the contact between the plasma and the water can be efficiently involved in the plasma. Therefore, the decomposition reaction of the harmful substance is promoted, and the water-soluble reaction product can be efficiently absorbed in water. Therefore, the efficiency of decomposing and separating harmful substances can be increased. Moreover, when the harmful substance is a solid or a liquid, the harmful substance is supplied to the water reservoir 8 through the introduction pipe 17 or together with the water from the water supply pipe 16, and the harmful substance flows down to the inner wall of the reaction channel 13 together with the water. The substance can be decomposed by contact with the plasma.
Further, since the reaction pipe 3 is cooled by the water in the water reservoir 8, it is possible to prevent the wall surface temperature of the reaction channel 13 from excessively increasing. For this reason, it is possible to prevent the water flowing down the inner wall of the reaction channel 13 from being completely evaporated in the middle of the reaction channel 13. Therefore, since the inner wall of the reaction channel 13 is always covered with the water film, erosion of the inner wall of the reaction channel 13 can be prevented.
Further, since the ground electrode 11 is provided along the inner surface of the reaction passage 13, water flows along the inner surface of the ground electrode 11. Therefore, the ground electrode 11 is automatically cooled, and the wear of the electrode can be suppressed. Moreover, the harmful substance passes through the inside of the water film formed on the inner surface of the ground electrode 11, so that the ground electrode 11 does not become a resistance when the harmful substance flows through the reaction channel 13.
In addition, if the water supplied from the water supply pipe 16 is heated in advance, the water heated by the heat of the plasma can be efficiently converted into steam, so that the steam can be efficiently supplied to the plasma.
[0015]
Next, another embodiment of the object processing apparatus is shown in FIG. Although FIG. 2 is a configuration diagram of a main part of the processing apparatus according to the embodiment, the same configuration as FIG. 1 is partially omitted from the drawings, and the same functions are denoted by the same reference numerals and description thereof is omitted.
In this embodiment, the ground electrode 11 is a rod-shaped electrode parallel to the center line of the reaction channel 13.
As shown in FIG. 2, a rod-shaped ground electrode 11 is provided on the center line of the reaction pipe 3, that is, on the center line of the reaction channel 13.
For this reason, the ground electrode 11 is not completely covered with the water flowing down along the inner wall of the reaction pipe 3, and a part of the ground electrode 11 is always exposed from the water film. Therefore, the plasma formed between the ground electrode 11 and the high-voltage electrode 12 comes into direct contact with the ground electrode 11, so that power loss due to water resistance can be eliminated.
Further, as shown in FIG. 2, the water supply pipe 16 may be provided at a lower portion of the main body case 10.
[0016]
In the above-described embodiment, the reaction pipe 3 is vertically mounted. However, the reaction pipe 3 may be inclined, and the high-voltage electrode 12 is on the upper side and the ground electrode 11 is on the ground. It may be arranged on the lower side.
Further, in the above-described embodiment, the case where water is supplied into the reaction pipe 3 has been described, but water other than water may be supplied. Further, an alkaline substance such as sodium hydroxide, potassium hydroxide, or ammonia may be dissolved in water. In this way, when CF ₄ is decomposed and the F component is dissolved in water, it becomes strongly acidic as it is, but this can be immediately neutralized, thereby suppressing the corrosion of the drainage system. There is an advantage that you can.
Further, a substance having high reactivity with the reaction product (for example, calcium hydroxide or the like) may be dissolved in water. This has the advantage that when the CF ₄ is decomposed and the F component is dissolved in water, it can be immediately precipitated and removed.
[0017]
【The invention's effect】
As is clear from the description of the above embodiment, according to the present invention, at the time of starting discharge or at the time of restart, by supplying the electrolyte, a path through which a current flows between the high-voltage electrode and the ground electrode is formed. Since it is formed, plasma can be easily generated.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram of an apparatus for processing an object to be processed according to one embodiment of the present invention. FIG. 2 is a main part configuration diagram of a processing apparatus according to another embodiment of the present invention.
3 Reaction pipe 8 Water reservoir 11 Ground electrode 12 High voltage electrode 13 Reaction channel 14 Power supply 16 Water supply pipe 21 Nozzle 22 Electrolyte supply part

Claims (7)

A uniform water film is formed in the reaction channel by overflowing from the outer periphery of the tubular elongated reaction channel, and a discharge is caused between the high-pressure electrode in the air and the ground electrode in the water film. A method for starting discharge, wherein at the start of discharge or at the time of re-ignition, a low-resistance current path is once passed between the high-voltage electrode and the ground electrode in the water film in the reaction channel by an electrolytic solution. After the formation, the supply of the electrolytic solution is stopped, and a current path between the high-voltage electrode and the ground electrode is interrupted to start or re-ignite a predetermined length of discharge. How to start the discharge. A high-voltage electrode is disposed on one side and a ground electrode is disposed on the other side, and a current flow path is formed between the vicinity of the high-voltage electrode and the ground electrode, at the time of starting or restarting discharge, after applying a voltage to the high-voltage electrode, By flowing an electrolytic solution into the flow path, a short-distance discharge is started between the high-voltage electrode and the electrolytic solution, and a predetermined length of discharge is obtained by stopping the flow of the electrolytic solution. How to start the discharge. 3. The method according to claim 1, wherein the plasma is generated by an arc discharge. An elongate tubular reaction channel through which the object passes, a high-pressure electrode disposed above the reaction channel, and a ground electrode disposed below the reaction channel; In the processing method of the object to be processed by processing the object such as chlorofluorocarbons by generating plasma in the axial direction, at the start of discharge, or at the time of restart, the electrolytic solution flows from the upper side of the reaction channel, A method for treating an object to be treated, wherein the flow of the electrolytic solution is stopped after a voltage is applied to the high-voltage electrode. The method according to claim 4, wherein a water reservoir is formed at an outer peripheral portion of the reaction channel, and water in the water reservoir is supplied to the reaction channel. The method according to claim 4, wherein plasma is generated by arc discharge. A tubular elongated reaction channel through which an object passes, a high-pressure electrode disposed at one end of the reaction channel, a ground electrode disposed at the other end of the reaction channel, A water supply pipe for supplying water into the reaction flow path from above, a discharge pipe for discharging water from the reaction flow path from below the reaction flow path, and a reaction flow from above the reaction flow path And a nozzle for supplying an electrolytic solution in the passage.

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