JP2004008893A - Plasma generating apparatus for waste gas decomposition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make performable a prescribed waste gas decomposition with remarkable high performance and efficiency by improving the responsiveness to the rapid deviation of loaded impedance with a compact, low cost and excellently durable structure as a whole. <P>SOLUTION: A high frequency power matching circuit 27 in a plasma generating apparatus for waste gas decomposition constituted so as to decompose the tail gas discharged from a semiconductor process chamber 1 by the generation of plasma in a vessel 5 of a high frequency discharge tube 4 formed by winding a high frequency discharging electrode 9 of an inductive coupling system on the outer circumference of an insulating tubular vessel 5 is formed into a fixed type or a semi-fixed type, a oscillator 13 of a high frequency power production source 8 is formed into a frequency variable type and a frequency control circuit 26 for variably controlling the oscillation frequency of the oscillator 13 so as to match the loaded impedance with output impedance, is provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma generator for exhaust gas decomposition processing. More specifically, for exhaust gas decomposition treatment in which exhaust gas discharged from various semiconductor manufacturing process chambers such as a chemical vapor deposition (CVD) process, a plasma CVD process, and a plasma etching process is rendered harmless by a discharge method using plasma. The present invention relates to a plasma generator.
[0002]
[Prior art]
Various reactive gases used in various semiconductor processes such as those described above often have toxicity, flammability, corrosiveness, etc., and some of these reactive gases are consumed during the semiconductor process. The remaining reactive gas is discharged out of the system as an unreacted gas. This unreacted exhaust gas is, for example, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₆ F ₁₄ (Perfluorinated carbon) gas such as NF ₃ Such as fluorinated nitrogen gas, SF ₆ And fluorinated gases such as fluorinated sulfur gases and their mixed gases. If these gases are discharged into the atmosphere without treatment, they may cause pollution, disasters such as air pollution, and environmental destruction. For this reason, in recent years, it has been required and legally obliged to release the harmful components in the exhaust gas discharged from the process chamber for semiconductor manufacturing into the atmosphere after detoxification treatment.
[0003]
As a general method of detoxifying harmful exhaust gas such as semiconductor process exhaust gas, a dilution treatment method of diluting harmful components in exhaust gas using a large excess of inert gas, and using exhaust gas with fuel and air Combustion treatment methods such as combustion, high-temperature heat decomposition and high-temperature treatment methods by catalytic decomposition with high-temperature reactants are known. Among these treatment methods, the dilution treatment method is used in the revision of high-pressure gas and special material gas. Therefore, the combustion treatment method produces a large amount of fine particles (dust) that are harmful to the environment as a by-product of combustion. In addition to the high temperature treatment method, there are many problems in practical use, such as the fact that fine particles block various jet ports and burners of the combustion system to easily cause a failure in the combustion system. H ₄ And NF contained in exhaust gas ₃ There is a problem that there is a danger of explosion due to mixing at a high temperature with water.
[0004]
As a method of detoxifying exhaust gas without causing various problems of these general processing methods, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-226032, the exhaust gas is discharged from a process chamber for semiconductor manufacturing or the like. Exhaust gas is introduced into an insulating tubular container, and high-frequency power is applied to a coiled electrode of a high-frequency discharge tube in which an inductively coupled high-frequency discharge electrode is wound in a spiral coil shape around the outer periphery of the tubular container. Conventionally, an inductively coupled plasma type exhaust gas decomposition treatment apparatus has been proposed in which an exhaust gas is decomposed by generating plasma in the container.
[0005]
Meanwhile, as a high-frequency power generation source (power supply) for plasma generation in a conventionally proposed inductively coupled plasma type exhaust gas decomposition treatment apparatus, conventionally, a fixed-frequency oscillator whose oscillation frequency is assigned to industrial use is generally used. The output impedance of the high-frequency power applied to the high-frequency discharge tube under the fixed oscillation frequency of the oscillator is automatically matched to the load impedance of the high-frequency discharge tube via a phase / impedance adjusting mechanism such as a servomotor. And a high-frequency power matching circuit variably controlled.
[0006]
[Problems to be solved by the invention]
The above-described inductively coupled plasma type exhaust gas decomposition treatment apparatus employs a method of disposing an electrode for high frequency discharge for plasma generation in a plasma region, that is, a tubular container under reduced pressure, and similarly decomposing exhaust gas with plasma. In comparison, the electrode and its protective material ₃ It does not need to come into direct contact with fluorine radicals, fluorine ions, or the like generated due to the above-mentioned factors, and has an excellent feature that the consumption of electrodes and the like is small and the damage is small, thereby improving the durability of the processing apparatus.
[0007]
On the other hand, in this type of plasma generator for exhaust gas decomposition treatment, the type and concentration of the reactive gas used, the operating pressure range, etc. are changed, or the capacitance under transient conditions where the plasma before and after discharge plasma ignition is unstable is unstable. The load impedance may fluctuate greatly due to fluctuations and the like. In this case, in the conventional device, the resonance condition is established through the phase / impedance adjustment mechanism such as a servomotor by changing the capacitance or inductance which is a component of the high-frequency power matching circuit. In order to automatically adjust the output impedance to the load impedance by adjusting it, many mechanical elements are required, which not only inevitably increases the cost and the size of the device, but also moves mechanical elements such as servo motors. Due to the inertia of the In addition, the responsiveness for generating stable plasma is lacking, and as a result, not only the processing time under unstable plasma is prolonged, but also the time required for matching is a loss time for a predetermined decomposition process. In addition, there is a problem that the exhaust gas decomposition performance and the processing efficiency are reduced. Furthermore, there is a problem that the durability (lifetime) of the entire apparatus is shortened due to wear or damage of a servomotor and a movable mechanical element such as a link mechanism that operates in conjunction therewith.
[0008]
The present invention has been made in view of the above-described circumstances, and suppresses wear and tear of electrodes and the like, and a decrease in durability due to wear and abrasion of movable mechanical elements, and, while configuring the whole as compact and low-cost, It is an object of the present invention to provide a plasma generator for exhaust gas decomposition processing capable of improving the response to a sudden change in load impedance and performing very high-performance and efficient predetermined exhaust gas decomposition processing.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a plasma generator for exhaust gas decomposition treatment according to the present invention comprises a high-frequency discharge formed by winding an inductively-coupled high-frequency discharge electrode in a spiral coil shape around the outer periphery of an insulating tubular container. A tube, a high-frequency power source for applying high-frequency power to the coil-shaped high-frequency discharge electrode of the high-frequency discharge tube to generate plasma in the container, and an output impedance of the high-frequency power source to a load of the high-frequency discharge tube. A high-frequency power matching circuit for matching impedance, comprising: a plasma generator for exhaust gas decomposition processing, wherein the high-frequency power matching circuit is fixed or manually fine-adjustable to hold the impedance at a preset value. In addition to being configured as a semi-fixed type, the oscillator of the high frequency power generation source is configured as a variable frequency type, and It is characterized in that the frequency control circuit the output impedance of the high frequency power source, the oscillation frequency of the load impedance is controlled to be aligned is provided.
[0010]
According to the present invention having the above-described characteristic configuration, the high-frequency discharge electrode for plasma generation is wound around the outer periphery of the insulating tubular container in a spiral coil shape and is arranged outside the plasma region. Excited NF ₃ In addition to reducing the wear and damage of the electrodes and the like due to the direct contact of the high-frequency discharge electrode and its protective material with the fluorine radicals and fluorine ions generated due to the existence of the high-frequency power matching circuit Is of a fixed or semi-fixed type and does not use a movable mechanical element that is easily worn or damaged, such as a servomotor, so that the durability of the entire apparatus can be improved. In addition, if the load impedance fluctuates rapidly due to changes in the type and concentration of the reactive gas used, the operating pressure range, etc., or fluctuations in capacitance under transient conditions where the plasma before and after discharge plasma ignition is unstable, By controlling the oscillation frequency of the oscillator in the high-frequency power generation source via the control circuit so that the output impedance of the high-frequency power generation source matches the load impedance, the high-frequency operation is performed using mechanical elements such as a servomotor and its control circuit. Compared to the conventional device that automatically adjusts the capacitance or inductance, which is a component of the power matching circuit, so that the resonance condition is satisfied, the size and cost of the entire device are reduced, while the load impedance is rapidly changed. To quickly follow the discharge plasma Causes generated, the generated plasma is maintained in a stable state performance of the predetermined exhaust gas decomposition process, and can be very efficiently performed.
[0011]
In the plasma generator for exhaust gas decomposition treatment according to the present invention having the above configuration, as described in claim 2, a reflected wave of high-frequency power applied to the high-frequency discharge electrode is detected, and the detected reflected wave power is set in advance. When it becomes more than the set value, by adding a traveling wave emission power suppression circuit that lowers the traveling wave power of the high-frequency power, the reflected wave power that cannot be avoided during the exhaust gas decomposition treatment by plasma exceeds the set value. When the power is increased, the traveling wave power is reduced, that is, the effective power is prevented from rising to a certain level or more, thereby protecting the high frequency power generation source and further improving the durability of the entire device, and further improving the power generation. Adverse effects on the source area can be avoided.
[0012]
Further, in the plasma generator for exhaust gas decomposition treatment according to the present invention having the above configuration, the output impedance of the high-frequency power generation source is matched to the load impedance by changing the oscillation frequency of the oscillator of the high-frequency power generation source to the load impedance. By providing a frequency switching circuit that can be switched between a state in which the load is variably controlled and a state in which the set frequency is fixed, exhaust gas having a condition in which the load impedance is likely to fluctuate rapidly, such as a semiconductor process gas, can be treated. In doing so, the oscillator frequency of the oscillator is switched to the variable control state to be used to promptly respond to the fluctuating load impedance by using it, so that the predetermined exhaust gas decomposition process can be efficiently performed, or that the load impedance does not fluctuate, or When treating exhaust gas with extremely small fluctuations, the oscillation frequency of the oscillator By switching to a fixed state, the characteristics and processing conditions of the exhaust gas to be treated can be adjusted so that the predetermined exhaust gas decomposition process can always be performed stably without the instability factors associated with the feedback variable control of the oscillation frequency. Correspondingly, two usage modes, a state in which the oscillation frequency is variably controlled and a state in which the oscillation frequency is fixed, can be arbitrarily selected, and the applicability of the plasma generator can be expanded.
[0013]
The exhaust gas to be decomposed by the plasma generator for decomposing exhaust gas according to the present invention having the above-mentioned structure is CF discharged from the semiconductor process chamber. ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₆ F ₁₄ (Perfluorinated carbon) gas such as NF ₃ Such as fluorinated nitrogen gas, SF ₆ A fluorine-based exhaust gas such as a fluorinated sulfur gas and a mixed gas thereof is most suitable. Further, in accordance with the gas type of the fluorine-based exhaust gas, H ₂ O, O ₂ Is added and introduced into the tubular container constituting the high-frequency discharge tube, so that various types of unreacted gases can be reliably decomposed.
[0014]
Further, the high-frequency discharge tube in the plasma generator for exhaust gas decomposition treatment according to the present invention having the above-mentioned configuration is configured by winding an inductively-coupled high-frequency discharge electrode in a spiral coil shape around the outer periphery of an insulating tubular container. As long as it is sufficient, the high-frequency discharge electrode is wound in a spiral coil shape around the outer periphery of the insulating tubular container in a state in which the cooling water can flow therethrough. And a small-diameter high-frequency power line disposed between the spiral pitches of the large-diameter conductive metal tube and spirally wound around the outer periphery of the insulating tubular container. A configuration in which the end of the conductive metal tube on the exhaust gas outlet side and the end of the small-diameter high-frequency power line on the exhaust gas inlet side may be electrically connected may be used. In this case, even if the center frequency of the power applied to the electrodes is set high to increase the efficiency of plasma generation by inductive coupling by flowing cooling water inside the large-diameter conductive metal tube during plasma generation, In addition to suppressing the heat generated by the effect, the power loss can be reduced, and since the small-diameter high-frequency power line is arranged in the dead space between the spiral pitches of the large-diameter conductive metal tube, the cooling action for the small-diameter high-frequency power line is also maintained, and Even though a high-frequency discharge tube having a short overall length is used, the number of turns of the entire high-frequency discharge electrode can be increased, and the effective power for stable plasma generation can be reduced and the durability of the electrode can be further improved. In addition, in a stable plasma generation situation, the increase in reflected power is suppressed by the cooling action of the two coiled electrodes, and the exhaust gas is always efficiently decomposed and harmless without a special power adjustment device or magnetic field application device. Can be processed.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a plasma generator for exhaust gas decomposition processing for a semiconductor process applied as the plasma generator for exhaust gas decomposition processing according to the present invention, and includes a chemical vapor deposition (CVD) process, a plasma CVD process, and plasma etching. Unreacted fluorine-based exhaust gas discharged from various semiconductor process chambers 1 such as a process is introduced into a high-frequency discharge tube 4 through a discharge pipe 3 by a turbo molecular pump 2. Here, as the unreacted fluorine-based exhaust gas to be treated, for example, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₆ F ₁₄ (Perfluorinated carbon) gas such as NF ₃ Such as fluorinated nitrogen gas, SF ₆ Fluorinated gas such as fluorinated sulfur gas and the like, and a mixed gas thereof. Before the fluorinated exhaust gas is introduced into the high-frequency discharge tube 4, H ₂ O, O ₂ By adding a gas containing, for example, 2NF ₃ And CF ₄ + 2H ₂ O and the like are introduced into the high-frequency discharge tube 4 by a chemical reaction.
[0016]
As shown in FIG. 2, the high-frequency discharge tube 4 includes an exhaust gas inlet 5a connected to the exhaust gas pipe 3 and an outlet 5b connected to the vacuum pump 6 for discharging the atmosphere via a pipe 7. An insulating tubular container 5 made of, for example, heat-resistant ceramic or quartz glass, and a tubular coil formed by applying a high-frequency power from a high-frequency power generating source 8 described later, which is wound around the outer periphery of the insulating tubular container 5 in a spiral coil shape. It comprises an inductively-coupled high-frequency discharge electrode 9 capable of generating plasma in the container 5.
[0017]
Here, as an example of the high-frequency discharge electrode 9, as shown in FIG. 3, for example, a spiral coil is wound around the outer periphery of the insulating tubular container 5 in a state where the cooling water CW can flow therethrough. A spiral coil is disposed around the outer periphery of the insulating tubular container 5 and is disposed one by one in all of the dead space between the spiral pitch of the large-diameter conductive metal tube 10 and the spiral pitch of the large-diameter conductive metal tube 10 such as a copper tube. End portion 10b of the large-diameter conductive metal tube 10 on the exhaust gas outlet 5b side and end portion of the small-diameter high-frequency power line 11 on the exhaust gas inlet 5a side. 11a and the end 10a of the large-diameter conductive metal tube 10 on the exhaust gas inlet 5a side and the end 11b of the small-diameter high-frequency power line 11 on the exhaust gas outlet 5b side are connected to a high frequency. Connected to the power supply 8, which Used those constituting the wave discharge electrode 9 total number of coil turns N to twice the number of turns of the coils of the large 径導 conductive metal tube 10. The high-frequency discharge electrode 9 may have a configuration in which, for example, a high-frequency power line is simply wound in a spiral coil shape around the outer periphery of an insulating tubular container, other than the configuration explicitly shown in FIG.
[0018]
FIG. 4 is a configuration diagram of a high-frequency power generation source (power supply) 8 that applies high-frequency power to the high-frequency discharge electrode 9 of the high-frequency power tube 4 in the plasma generator for exhaust gas decomposition processing for a semiconductor process having the above-described basic configuration. is there. In the figure, reference numeral 13 denotes a variable frequency crystal oscillator having a center frequency of 2 MHz or 4 MHz and a range of ± 0.5 MHz with respect to the center frequency, that is, 1.5 to 2.5 MHz or It is configured to be variably controllable in a range of 3.5 to 4.5 MHz. Reference numeral 14 denotes a phase-locked loop (PLL), in which the oscillation frequency of the oscillator 13 is fixed at its center frequency of 2 MHz or 4 MHz and variably controlled in the above range (1.5 to 2.5 MHz or 3.5 to 4.5 MHz). When the frequency switching circuit 15 configured to be able to switch to the state is switched to the fixed frequency side, the output frequency is fed back and the oscillation frequency is automatically adjusted to the fixed frequency necessary for generating the discharge plasma. I have.
[0019]
Reference numerals 16 and 17 denote power amplifiers. The operational amplifier 20 calculates a deviation between the set power Ptf preset by the power setting unit 18 and the traveling wave power Pf detected and fed back by the power directional coupler 19. The oscillating frequency is power-amplified based on the output signal of the effective power automatic adjustment circuit 21 for calculating the power amplification factor corresponding to the deviation, and high-frequency power is output. Reference numeral 22 denotes an operational amplifier 24 which calculates a deviation between the reflected wave power Pr detected and returned by the power directional coupler 19 and a set reflected wave power Ptr whose upper limit is set in advance by the reflected power setting unit 23. This is a traveling wave power suppression circuit that lowers (drops) traveling wave power so that the deviation becomes zero or less, and a high-frequency power generation source (power supply) 8 is configured by the above components 13 to 24.
[0020]
Reference numeral 25 denotes a VI phase difference detection circuit for detecting a phase difference between the voltage V and the current I of the high-frequency power. When the frequency switching circuit 15 is switched to the variable frequency side, the VI phase difference detection circuit 25 25, the oscillation frequency of the oscillator 13 is set in the above range (1.5 to 2.5 MHz or 3.5 to 4.5 MHz) based on the detection signal S of the operational amplifier 28 for detecting the phase difference between the voltage and the current of the high-frequency power. ) Is interposed in the feedback system of the frequency variable loop. Reference numeral 27 denotes a high-frequency power matching circuit composed of a capacitance and an inductance. The high-frequency power matching circuit 27 matches the output impedance of the high-frequency power generation source (power supply) 8 to the load impedance of the high-frequency power tube 4. Is fixedly held at a predetermined value or a semi-fixed type which can be finely adjusted manually.
[0021]
In the plasma generator for exhaust gas decomposition treatment for a semiconductor process configured as described above, a fluorine-based gas such as an unreacted PFC gas, a fluorinated nitrogen gas, or a fluorinated sulfur gas discharged from the semiconductor process chamber 1 is used. Before the mixed gas is introduced into the high-frequency discharge tube 4 through the exhaust gas piping 3 by the turbo molecular pump 2, ₂ O, O ₂ Is added, for example, 2NF ₃ And CF ₄ + 2H ₂ O is introduced into the insulating tubular container 9 of the high-frequency discharge tube 4 after being chemically reacted with O or the like. The high-frequency discharge electrode 9 of the high-frequency discharge tube 4 is applied with high-frequency power having a center frequency of 2 MHz or 4 MHz from a high-frequency power source 8 to generate plasma in the tubular container 9 by inductive coupling. When the above introduced exhaust gas comes into contact with the plasma, for example, N 2 ₂ + 6F or CO ₂ After being decomposed into +4 HF and detoxified, it is discharged to the atmosphere by a vacuum pump 6.
[0022]
During the detoxification treatment of semiconductor process exhaust gas by such inductively coupled plasma, the frequency switching circuit 15 is normally switched to the variable frequency side, and the type and concentration of the reactive gas used in the semiconductor process and the operating pressure range If the load impedance fluctuates rapidly due to a change in the frequency of the high frequency discharge tube 4 under a transient condition in which the plasma before and after the ignition of the plasma is unstable, the voltage of the high frequency power by the VI phase difference detection circuit 25 And a current phase difference detection signal S is fed back (feedback) to a voltage variable frequency control circuit (VCO) 26, and the oscillation frequency of the oscillator 13 of the high frequency power generation source 8 is changed to the load impedance by the high frequency power according to the feedback signal. The output impedance of the source 8 is variably controlled so as to match. Thus, even if the high-frequency power matching circuit 27 is of a fixed type or a semi-fixed type, the discharge plasma is quickly generated by responding to a rapid change in load impedance with good responsiveness, and the generated discharge plasma is stable. By maintaining the state, a predetermined exhaust gas decomposition treatment can be performed with high performance and efficiency.
[0023]
In such a processing operation, the reflected wave of the high-frequency power applied to the high-frequency discharge electrode 9 is always detected, and when the detected reflected-wave power Pr becomes equal to or more than a preset value Ptr, The traveling wave power Pf can be reduced (dropped) through the traveling wave power suppression circuit 22 so that the deviation becomes zero or less, whereby the reflected wave that cannot be generated when the exhaust gas is decomposed by the discharge plasma. An increase in traveling wave power accompanying an increase in power beyond a set value, that is, an abnormal increase in effective power, can be suppressed, and the high-frequency power generation source 8 can be protected to improve the durability of the entire apparatus. At the same time, it is possible to avoid adverse effects on the vicinity of the high frequency power generation source 8.
[0024]
Further, by circulating the cooling water CW inside the large-diameter conductive metal tube 10 constituting the high-frequency discharge electrode 9 of the high-frequency discharge tube 4, the frequency of the power applied to the electrode 9 is reduced to about 2 or 4 MHz. Even if it is set high, the heat loss due to the skin effect can be suppressed to reduce the power loss, and the small-diameter high-frequency power line 11 is arranged in the dead space between the spiral pitches of the large-diameter conductive metal tube 10, so that the small-diameter high-frequency power line 11 is disposed. It is possible to increase the number of coil turns N of the high-frequency discharge electrode 9 as a whole while keeping the cooling effect on the power line 11 good and shortening the entire length L of the high-frequency discharge tube 4 to make the entire device compact. It is possible. Thereby, the plasma ignition power can be reduced and the durability of the electrode 9 can be improved.
[0025]
In the above-described embodiment, the frequency switching circuit 15 is used because the load impedance of the high-frequency discharge tube 4 is applied to a plasma generator for decomposing exhaust gas for a semiconductor process, which tends to fluctuate rapidly due to a change in the type of reaction gas used. Is always switched to the variable control side for use. However, when the present invention is applied to a device having no or very little change in load impedance, the oscillation frequency can be changed by switching the frequency switching circuit 15 to the fixed side. It is possible to always maintain a stable plasma by eliminating unstable elements accompanying the variable control of. By providing the frequency switching circuit 15 in this manner, the applicability of the plasma generator can be expanded.
[0026]
【The invention's effect】
As described above, according to the present invention, the use of the inductively coupled electrode for high-frequency discharge minimizes the wear and damage of the electrode and its protective material, and the fixed or semi-fixed high-frequency power matching circuit. By using a movable mechanical element which is liable to be worn, damaged or broken down such as a servomotor using a servomotor, the durability of the entire apparatus can be remarkably improved. In addition, a high frequency is used for sudden changes in load impedance due to changes in the type and concentration of the reactive gas used, operating pressure range, etc., or changes in capacitance under transient conditions where the plasma is unstable before and after ignition of the plasma. By controlling the oscillation frequency of the oscillator of the power generation source, it is possible to match the output impedance of this high-frequency power generation source to the load impedance, and when using a conventional automatic matching circuit that requires a mechanical element such as a servo motor. In comparison, while achieving compactness and cost reduction of the entire apparatus, a discharge plasma is quickly generated by responding rapidly to a rapid change in load impedance, and the generated plasma is always maintained in a stable state. This has the effect of enabling high-performance and efficient exhaust gas decomposition processing. That.
[0027]
In addition, by providing the traveling wave power suppression circuit as described in claim 2, the effective power of the effective power due to the unavoidable increase of the reflected wave power that occurs during the decomposition treatment of the exhaust gas by the plasma to a set value or more is provided. An abnormal rise can be suppressed, the high-frequency power generation source can be protected, the durability of the entire apparatus can be further improved, and adverse effects on the surroundings can be avoided.
[0028]
In addition, by providing a frequency switching circuit as described in claim 3, when exhaust gas whose load impedance is likely to fluctuate rapidly, such as a semiconductor process gas, is to be treated, the fluctuating load impedance is applied. In the case where the exhaust gas decomposition process can be performed efficiently by responding quickly and the load impedance does not fluctuate or the exhaust gas under very small conditions is to be processed, the oscillator frequency of the oscillator should be fixed and used. In order to eliminate the unstable elements associated with the feedback control and perform the predetermined exhaust gas decomposition treatment constantly and stably, two appropriate use modes corresponding to the properties of the exhaust gas to be treated and the like are obtained, and the plasma generator Applicability can be expanded.
[0029]
Further, when the high-frequency discharge tube having the structure as described in claim 6 is used, even if the center frequency of the power applied to the electrode is set high in order to increase the efficiency of plasma generation by inductive coupling, the skin effect is obtained. In addition to suppressing heat generation due to the above, power loss can be reduced, and since the small-diameter high-frequency power line is arranged in the dead space between the spiral pitches of the large-diameter conductive metal tube, the cooling action for the small-diameter high-frequency power line is also maintained, and Although the high-frequency discharge tube having a short overall length is used, the number of turns of the entire high-frequency discharge electrode can be increased, and the effective power for stable plasma generation can be reduced and the durability of the electrode can be further improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exhaust gas decomposition processing plasma generator for a semiconductor process applied as an exhaust gas decomposition processing plasma generator according to the present invention.
FIG. 2 is a front view showing a configuration of a high-frequency discharge tube in the device.
FIG. 3 is an enlarged front view of a main part of FIG. 2;
FIG. 4 is a configuration diagram of a high-frequency power generation source in the above device.
[Explanation of symbols]
1 Semiconductor process chamber
4 High frequency discharge tube
5 Insulating tubular container
8 High frequency power source
9 High frequency discharge electrode
10 Large diameter conductive metal tube
11 Small diameter high frequency power line
13. Variable frequency oscillator
15 Frequency switching circuit
22 Reflected power suppression circuit
26 Frequency control circuit
27 High frequency power matching circuit

Claims (6)

A high-frequency discharge tube formed by winding an inductively coupled high-frequency discharge electrode in a spiral coil around the outer periphery of an insulating tubular container, and applying high-frequency power to the coil-shaped high-frequency discharge electrode of the high-frequency discharge tube A high-frequency power generation source for generating plasma in the container, and a high-frequency power matching circuit for matching the output impedance of the high-frequency power generation source to the load impedance of the high-frequency discharge tube, is a plasma generator for exhaust gas decomposition processing. So,
The high-frequency power matching circuit is configured as a fixed type that holds and holds the impedance at a preset value or a semi-fixed type that can be finely adjusted manually, and the oscillator of the high-frequency power generation source is configured as a variable frequency type. And a frequency control circuit for controlling the oscillation frequency of the oscillator so that the output impedance of the high frequency power generation source matches the load impedance. A traveling-wave power suppression circuit is provided for detecting a reflected wave of high-frequency power applied to the high-frequency discharge electrode and reducing the traveling-wave power of high-frequency power when the detected reflected-wave power becomes equal to or greater than a preset value. The plasma generator for exhaust gas decomposition treatment according to claim 1, wherein: A frequency switching circuit capable of switching between a state in which the oscillation frequency of the oscillator of the high-frequency power generation source is variably controlled so that the output impedance of the high-frequency power generation source matches the load impedance and a state in which the oscillation frequency is fixed at a set frequency is provided. The plasma generator for exhaust gas decomposition treatment according to claim 1 or 2, wherein: The plasma generator for exhaust gas decomposition treatment according to any one of claims 1 to 3, wherein the exhaust gas to be subjected to the decomposition treatment is a fluorine-based exhaust gas discharged from a semiconductor process chamber. 5. The method according to claim 4, wherein a gas containing H ₂ O and O ₂ is added in accordance with a gas type of the fluorine-based exhaust gas and introduced into a tubular container constituting the high-frequency discharge tube. 6. Plasma generator for exhaust gas decomposition treatment. The high-frequency discharge electrode has a large-diameter conductive metal tube wound in a spiral coil shape around the outer periphery of the insulating tubular container in a state in which cooling water can flow therein, and a spiral of the large-diameter conductive metal tube. A small-diameter high-frequency power line disposed between the pitches and wound around the outer periphery of the insulative tubular container in a spiral coil form; The plasma generator for exhaust gas decomposition treatment according to any one of claims 1 to 5, wherein the plasma generator is electrically connected to an end on the exhaust gas inlet side of the exhaust gas.

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