JP2006102717A - Treatment method and treatment apparatus for harmful component-containing gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for a harmful component-containing gas exhibiting good treatment efficiency to the harmful component-containing gas with difficult plasma decomposition such as perfluoromethane, and a treatment apparatus. <P>SOLUTION: In the treatment method for the harmful component-containing gas, the harmful component-containing gas is decomposed by plasma 100 in co-existence of a reactive gas. In the treatment method for the harmful component-containing gas, electric power of a microwave for generating the plasma 100 is adjusted by existence of perfluoromethane in the harmful component-containing gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for treating harmful component-containing gas, and in particular, a method for treating harmful components in gas discharged from a semiconductor manufacturing process, for example, perfluoro compound, and the method. The present invention relates to a processing apparatus.

In an etching process in a semiconductor manufacturing process, a CVD (chemical vapor deposition) chamber cleaning process, and the like, perfluoromethane (hereinafter abbreviated as “CF ₄ ”), perfluoroethane (C ₂ F ₆ ), perfluoropropene ( C ₃ F ₆ ), perfluoropentadiene (C ₅ F ₈ ), trifluoromethane (CHF ₃ ), nitrogen trifluoride (NF ₃ ), sulfur hexafluoride (SF ₆ ) and the like are used in large quantities. These gases are collectively called perfluoro compounds (hereinafter abbreviated as “PFC”), and are considered as greenhouse gases that cause global warming. Therefore, it is required to appropriately perform PFC processing and suppress the discharge thereof.

  Currently used treatment methods include combustion decomposition methods, heat decomposition methods, catalyst decomposition methods, heat reaction methods, recovery treatment methods, plasma decomposition methods, and the like. Among these, since the structure of the apparatus is relatively simple, the plasma decomposition method is considered to be the most practical and has been energetically studied in recent years (see, for example, Patent Document 1). The plasma decomposing method is a method for decomposing a gas containing harmful components such as PFC into plasma using electromagnetic waves such as microwaves.

An example of a processing apparatus used in the plasma decomposition method is shown in FIG. The processing apparatus of this example is generally composed of a reactive gas supply mechanism 10, a plasma generation mechanism 20, and a plasma container 30, and processes PFC discharged from a semiconductor manufacturing apparatus as a harmful component-containing gas. It is.
The reactive gas supply mechanism 10 is for supplying a reactive gas to the plasma container 30. This reactive gas reacts with the PFC converted into plasma to generate a stable compound such as carbon dioxide and hydrogen fluoride, and prevents recombination of the PFCs. As the reactive gas, an oxidizing agent such as water vapor that causes a hydrolysis reaction or oxygen that causes an oxidation reaction is used.

  The plasma generation mechanism 20 is for generating a microwave for converting the PFC into plasma and making it incident on the plasma container 30. The plasma generation mechanism 20 is provided with a microwave power source 21 and a microwave oscillator 22, which are connected to each other by an electric cable. When the microwave power source 21 is operated and driving power is supplied to the microwave oscillator 22, a microwave having a predetermined frequency is generated from the microwave oscillator 22.

The generated microwave propagates to the power monitor 25 via the waveguide 23 and the isolator 24, and incident power is detected by the power monitor 25. The isolator 24 is for protecting the microwave oscillator 22 by absorbing the microwave reflected from the plasma container 30. In addition, in the reflected microwave, the reflected power can be detected by the power monitor 25.
Next, the microwave enters the plasma container 30 via the matching unit 26 and the tapered waveguide 27. The matching unit 26 is for matching the load so that reflection is minimized. Further, the tapered waveguide 27 is for efficiently propagating microwaves to the plasma container 30.

  The plasma container 30 is for processing PFC into plasma inside thereof. A gas inflow pipe 31 is attached to the upper portion of the plasma container 30, and a nitrogen-based processing gas containing about 0.01 to 10% of PFC discharged from the semiconductor manufacturing apparatus 40 is in circulation. The gas inflow pipe 31 is provided with the reactive gas supply mechanism 10 so that the reactive gas is added to the processing gas. Further, the gas inflow pipe 31 communicates with the gas introduction part 32, and a mixed gas composed of a processing gas and a reactive gas is introduced into the plasma container 30.

  A cavity resonator 33 is provided below the gas introduction part 32. When a microwave is incident on the cavity resonator 33 from the plasma generation mechanism 20 and resonates, a gas flow pipe 39 (through a ceramic such as quartz) introduced from the gas introduction section 32 and penetrating through the cavity resonator 33. The mixed gas descending inside is made into plasma. An extension pipe 34 and a reaction pipe 35 are continuously provided at the lower part of the cavity resonator 33. The plasma mixed gas descends through these, and the PFC reacts with the reactive gas. Thus, a stable gas such as carbon dioxide or hydrogen fluoride is generated. Reference numeral 100 indicates plasma generated in the plasma container 30.

A cooling device 36 is provided at the bottom of the plasma container 30, and the generated gas is cooled by spraying cooling water from the cooling device 36. Thereafter, on the other hand, the gas is discharged from the plasma container 30 by the suction pump 37. On the other hand, water accumulated at the bottom of the plasma container 30 is discharged from the plasma container 30 by the drain pump 38.
By using such a processing apparatus, PFC can be converted into a harmless gas for processing.
JP 2003-245520 A

However, the conventional plasma decomposition method has a problem in that the microwave power required for the plasma conversion of the PFC is high, and the processing efficiency (that is, the PFC decomposition rate with respect to the microwave power) is poor. This is because PFC is generally a poorly reactive and stable substance. In particular, CF ₄ is a very stable material, and microwave plasma must be generated with high power in order to decompose the CF ₄ .

In view of the above-mentioned problems of the prior art, the present invention
It is an object of the present invention to provide a method and apparatus for treating harmful component-containing gas that exhibits good treatment efficiency for harmful component-containing gas that is difficult to decompose by plasma, such as PFC.

To solve this problem,
The invention according to claim 1 is a method for treating a harmful component-containing gas, wherein the harmful component-containing gas is decomposed by plasma in the presence of a reactive gas, and the presence or absence of CF ₄ in the harmful component-containing gas, It is a processing method for harmful component-containing gas, characterized by adjusting the power of microwaves that generate plasma.

  The invention according to claim 2 is characterized in that the adjustment of the power of the microwave is performed based on a signal sent from an etcher of a semiconductor manufacturing apparatus which is a discharge source of the harmful component-containing gas. It is a processing method of contained gas.

The invention according to claim 3 is characterized in that the microwave power is adjusted based on a signal sent from a detection means for detecting CF ₄ in the gas containing harmful components. It is a processing method of component-containing gas.

  The invention according to claim 4 is the method for treating a harmful component-containing gas according to any one of claims 1 to 3, wherein the reactive gas is a mixture of hydrogen and oxygen.

  The invention according to claim 5 is the method for treating a harmful component-containing gas according to any one of claims 1 to 4, wherein the adjustment time of the power of the microwave is 1 minute or less.

  According to a sixth aspect of the present invention, there is provided a plasma container for processing a harmful component-containing gas flowing from a semiconductor manufacturing apparatus, a plasma generation mechanism for generating plasma in the plasma container, and a reaction for supplying a reactive gas to the plasma container. An apparatus for processing a harmful component-containing gas comprising a reactive gas supply mechanism, a sending unit for sending a signal for notifying the presence or absence of perfluoromethane in the harmful component-containing gas, and a signal from the sending unit And a control unit for controlling the power of the microwave power source.

  According to a seventh aspect of the present invention, there is provided a plasma container for processing a harmful component-containing gas flowing from a semiconductor manufacturing apparatus, a plasma generation mechanism for generating plasma in the plasma container, and a reaction for supplying a reactive gas to the plasma container. And a detection unit that detects perfluoromethane in the harmful component-containing gas and sends a signal notifying the detection result, and a detection unit that detects the harmful component-containing gas. And a control unit for controlling the power of the microwave power supply in response to a signal from the unit.

According to the present invention, a high-power microwave is used when processing CF ₄ that is difficult to decompose by plasma, and a low-power microwave is used when processing a harmful component-containing gas that is relatively easy to decompose by plasma. As a result, the power consumption of the microwave can be minimized. Therefore, the processing efficiency of the harmful component-containing gas can be improved.

  An embodiment of a processing apparatus for harmful component-containing gas according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of the processing apparatus of the present invention. The same components as those of the conventional apparatus of FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the processing apparatus of FIG. 1, the difference from the conventional apparatus is that the delivery unit 42 is provided in the etcher 41 of the semiconductor manufacturing apparatus 40 and between the semiconductor manufacturing apparatus 40 and the reactive gas supply mechanism 10. The detection part 50 is provided in the gas inflow pipe 31, and the control part 28 is provided in the microwave power source 21.

The sending unit 42 is for sending a signal notifying the presence or absence of CF _{4 in} the PFC discharged from the etcher 41 to the control unit 28. As for the etching gas (PFC) used for an etching process, the kind and order of use are usually decided beforehand. Accordingly, a signal is sent from the sending unit 42 to the control unit 28 via the communication cable 43 in accordance with the order of use.

The detection unit 50 analyzes the PFC discharged from the etcher 41 and detects CF ₄ . Examples of the analytical instrument used for the detection unit 50 include FT-IR (infrared spectroscopy), ND-IR, constant potential electrolytic sensor, diaphragm sensor, mass analyzer, gas chromatography and the like. The present invention is not limited to these, and any PFC component can be applied as long as it can analyze and detect each component at high speed and with high sensitivity. The detection unit 28 is connected to the control unit 28 via the communication cable 51 so that a signal notifying the analysis result such as the presence or absence of CF ₄ is sent to the control unit 28. In the present invention, not only the communication cables 43 and 51 but also wireless communication may be used as a signal medium.

The control unit 28 is for adjusting the power supplied from the microwave power source 21 to the microwave oscillator 22 based on the signal sent from the sending unit 42 or the detecting unit 50. Specifically, the microwave power source 21 is controlled to generate a high-power microwave when CF ₄ is included in the PFC, and a low-power microwave when it is not included. Power is supplied to the wave oscillator 22. Therefore, the power of the microwave can be adjusted by the presence or absence of CF _{4 in} the PFC. In addition, in this specification, high power is a value of 140 to 160% of low power, and low power means a value of 60 to 70% of high power. Further, when the microwave is high power, it is called a normal processing mode, and when the microwave is low power, it is called an energy saving processing mode.

Hereinafter, an embodiment of a method for processing a harmful component-containing gas using the above processing apparatus will be described.
First, PFC is discharged from the etcher 41 of the semiconductor manufacturing apparatus 40. This PFC is diluted with nitrogen to become a processing gas, and then mixed with a reactive gas to become a mixed gas, which flows into the cavity resonator 33 of the plasma vessel 30. The flow rate of the mixed gas is not particularly limited, but is preferably 60 to 80 slm, and more preferably 70 to 80 slm from the viewpoint of processing capability.

As the reactive gas, a single substance or a mixture of hydrogen, oxygen, water vapor or the like is used. Among them, a mixture of hydrogen and oxygen is preferable, and the mixing ratio is preferably hydrogen: oxygen = 2: 1 based on the stoichiometric ratio in the hydrolysis reaction. Since the hydrolysis reaction has fewer by-products than the oxidation reaction, it is suitable for the treatment of PFC. Further, hydrogen and oxygen are gases at room temperature, and it is not necessary to apply heat unlike water vapor, so that they can be stably supplied into the processing gas.
Furthermore, hydrogen and oxygen have a lower binding energy than water vapor, and are easily converted to plasma because they are easily radicalized. Moreover, since the diffusion rate in a gaseous medium is large compared with water vapor | steam and mixing with PFC is easy, it reacts easily. Therefore, the decomposition rate of PFC can be improved.

On the other hand, as described above, a signal notifying the presence or absence of CF _{4 in} the PFC is sent from the sending unit 42 or the detection unit 50 of the etcher 41 to the control unit 28 via the communication cables 43 and 51. The control unit 28 adjusts the power supplied to the microwave oscillator 22 based on these signals. The control unit 28 may operate based on a signal from either the sending unit 42 or the detection unit 50, or may operate based on a signal from both. Moreover, since the average power of the microwave is proportional to the flow rate of the mixed gas when the PFC decomposition rate is constant, it is adjusted according to the flow rate of the used mixed gas.

The time required for adjusting the power of the microwave (hereinafter abbreviated as “adjustment time”) is preferably a short time so that it can follow the discharge time of the PFC used in the etching process. The following is preferable. In general, the adjustment time mainly depends on the power supply time in the microwave power source 21. This power supply time can be shortened to 1 to 4 seconds while maintaining the stability of the plasma 100. Therefore, the adjustment time can be shortened to about 1 minute or less including other operation times in the plasma generation mechanism 20.
Thus, by shortening the adjustment time as much as possible, the power of the microwave can be adjusted appropriately in accordance with the presence or absence of CF _{4 in} the PFC.

Next, the mixed gas flowing into the gas flow pipe 39 penetrating through the cavity resonator 33 is turned into plasma by the microwave incident from the plasma generation mechanism 20. At this time, since the power of the microwave is adjusted in advance by a signal from the etcher 41 or the detection unit 50, the mixed gas can be efficiently converted into plasma without supplying excessive power. . Next, the plasma mixed gas reacts with each other in the extension tube 34 and the reaction tube 35 to generate a stable gas, and is dehydrated and discharged to the outside of the plasma vessel 30.
By using the above processing method, the processing efficiency of PFC can be improved.

  Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[Example 1]
In Example 1, to evaluate the decomposition of CF _4, to measure the decomposition rate of CF ₄ by the processing unit of noxious component-containing gas of the present invention. In measuring the decomposition rate of CF ₄ , a mixed gas of nitrogen and reactive gas was used, and the flow rates of CF ₄ and nitrogen were set to 0.8 and 80 slm, respectively. Moreover, hydrogen and oxygen were used as the reactive gas, and the respective flow rates were set to 1.6 and 0.8 slm. For comparison, the decomposition rate of sulfur hexafluoride (hereinafter abbreviated as SF ₆ ), which is one of the PFCs, was also measured, and the flow rate of SF ₆ was set to 0.8 slm. The flow rates of other gases are the same as described above.

FIG. 2 shows a graph of measurement results. From this graph, it was confirmed that a decomposition rate of 90% was obtained with microwave power of 4.7 kW for CF ₄ (plotted with diamonds) and 3.0 kW for SF ₆ (plotted with triangles). Comparing the two, it was found that CF ₄ requires about 1.6 times higher microwave power than SF _{6 in} order to obtain a decomposition rate of 90%. On the other hand, it is known that PFCs other than CF ₄ exhibit the same decomposition rate as that of SF ₆ . Therefore, it has been clarified that the microwave power required for plasma decomposition of PFC other than CF ₄ is 64% of that of CF ₄ .

[Example 2]
In Example 2, the adjustment time of the microwave power in the processing apparatus for harmful component-containing gas of the present invention was measured. In measuring the adjustment time, the decomposition rate of CF ₄ was measured while switching between the normal processing mode and the energy saving processing mode, and the adjustment time was evaluated from the change in the decomposition rate. Further, a mixed gas composed of a reactive gas CF ₄ and nitrogen, was set CF ₄ and nitrogen flow rate to 0.8,80slm respectively. Moreover, hydrogen and oxygen were used as the reactive gas, and the respective flow rates were set to 1.6 and 0.8 slm. On the other hand, the microwave power in the normal processing mode was set to 5.3 kW, and the microwave power in the energy saving mode was set to 3.0 kW.
FIG. 3 shows a graph of measurement results. From the rise and fall of the curve in this graph, it was confirmed that the adjustment time was about 1 minute. It was also confirmed that the plasma 100 shown in FIG. 1 was stably generated when switching between the modes.

[Example 3]
In Example 3, in order to evaluate the effect of the mixture of hydrogen and oxygen as a reactive gas, the decomposition rate of CF ₄ by the method for treating a harmful component-containing gas of the present invention was measured. In measuring the decomposition rate, a mixed gas of CF ₄ and nitrogen was used, and the flow rates of hydrogen, oxygen, CF ₄ , and nitrogen were set to 1.6, 0.8, 0.8, and 80 slm, respectively. For comparison, the decomposition rate of CF ₄ when water vapor was used as the reactive gas was measured, and the flow rate of this water vapor was set to 1.6 slm. The flow rates of other gases are the same as in the case of a mixture of hydrogen and oxygen.
FIG. 4 shows a graph of measurement results. From this graph, it was confirmed that the mixture of hydrogen and oxygen (plotted with diamonds) improved the decomposition rate of CF ₄ compared with water vapor (plotted with squares). In addition, when a mixture of hydrogen and oxygen was used, it was confirmed that CO ₂ , HF, and NO _X were mainly generated.

[Example 4]
In Example 4, CF ₄ and SF ₆ were continuously treated using the method for treating harmful component-containing gas of the present invention, and the decomposition rate was measured. Specifically, CF ₄ and SF ₆ were alternately flowed, and these were processed while switching between the normal processing mode and the energy saving processing mode. In measuring the decomposition rate of CF ₄ and SF ₆ , a mixed gas of nitrogen and reactive gas was used, and the flow rates of CF ₄ , SF ₆ , and nitrogen were set to 0.8, 0.8, and 80 slm, respectively. Moreover, hydrogen and oxygen were used as the reactive gas, and the respective flow rates were set to 1.6 and 0.8 slm.
On the other hand, based on the result of Example 1 and the reflected power of 0.1 kW, the microwave power in the normal processing mode was set to 4.8 kW, and the microwave power in the energy saving mode was set to 3.1 kW. The inflow time of CF ₄ was 3 minutes and the inflow time of SF ₆ was 7 minutes, and after each time, they were exchanged. This ratio is the same as the ratio of CF ₄ and other PFC actually used in the etching process.
As a result, the decomposition rate of CF ₄ and SF ₆ was always 90% or more. In addition, the power consumption can be reduced by 25% compared with the conventional processing method (that is, the method of always maintaining the normal processing mode), and the processing efficiency can be improved.

The calculation formula for obtaining the power consumption reduction rate is as follows.
E = [{P ₁ × T ₁ − (P ₁ × T ₂ + P ₂ × T ₃ )} / (P ₁ × T ₁ )] × 100 (1)
(1) In the equation:
E: Reduction rate of power consumption (%)
P ₁ : microwave power (kW) in normal processing mode
P ₂ : Microwave power (kW) in energy saving processing mode
T ₁ : Sum of inflow time of CF ₄ and inflow time of SF ₆ (min)
T ₂ : CF ₄ inflow time (min)
T ₃ : SF ₆ inflow time (minutes)

[Example 5]
In Example 5, CF ₄ and SF ₆ were continuously treated using the method for treating harmful component-containing gas of the present invention, and the decomposition rate was measured. In Example 4, the difference from Example 3 is that the flow rates of CF ₄ , SF ₆ , nitrogen, hydrogen, and oxygen are set to 0.6, 0.6, 60, 1.2, and 0.6 slm, respectively. The microwave power in the normal processing mode is set to 3.8 kW, and the microwave power in the energy saving mode is set to 2.3 kW. Since other procedures are the same, description thereof is omitted.
As a result, the decomposition rate of CF ₄ and SF ₆ was always 90% or more. In addition, the power consumption can be reduced by 28% compared to the conventional processing method, and the processing efficiency can be improved.
The above formula (1) was used for comparison of power consumption.

It is a figure which shows an example of the plasma type processing apparatus concerning embodiment of this invention. ₆ is a graph showing a decomposition rate of CF ₄ and SF _{6 with} respect to microwave power in Example 1. Normal processing mode in the embodiment 2 is a graph showing the decomposition rate of CF ₄ by the energy saving process mode. In the case of using hydrogen and mixtures or water vapor of the oxygen in the Example 3 as a reactive gas is a graph showing the decomposition rate of CF ₄ in the microwave to the power. It is a figure which shows an example of the conventional plasma type processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Reactive gas supply mechanism, 20 ... Microwave generation mechanism, 28 ... Control part, 30 ... Plasma container, 40 ... Semiconductor manufacturing apparatus, 41 ... Etcher, 42 ... -Sending unit, 50 ... detecting unit, 100 ... plasma

Claims (7)

A method for treating a harmful component-containing gas, wherein the harmful component-containing gas is decomposed by plasma in the presence of a reactive gas,
A method for treating a harmful component-containing gas, wherein the microwave power for generating the plasma is adjusted depending on the presence or absence of perfluoromethane in the harmful component-containing gas.   2. The method for treating a harmful component-containing gas according to claim 1, wherein the adjustment of the power of the microwave is performed based on a signal sent from an etcher of a semiconductor manufacturing apparatus, which is a discharge source of the harmful component-containing gas.   The method for treating a harmful component-containing gas according to claim 1 or 2, wherein the microwave power is adjusted based on a signal sent from a detection means for detecting perfluoromethane in the harmful component-containing gas.   The method for treating a harmful component-containing gas according to any one of claims 1 to 3, wherein the reactive gas is a mixture of hydrogen and oxygen.   The method for treating a harmful component-containing gas according to any one of claims 1 to 4, wherein the adjustment time of the microwave power is 1 minute or less. A plasma container for processing harmful component-containing gas flowing from a semiconductor manufacturing apparatus;
A plasma generation mechanism for generating plasma in the plasma container;
A processing apparatus for harmful component-containing gas comprising a reactive gas supply mechanism for supplying a reactive gas to the plasma container,
A sending section for sending a signal notifying of the presence or absence of perfluoromethane in the harmful component-containing gas;
A harmful component-containing gas processing apparatus comprising: a control unit that receives a signal from the sending unit and controls electric power of a microwave power source. A plasma container for processing harmful component-containing gas flowing from a semiconductor manufacturing apparatus;
A plasma generation mechanism for generating plasma in the plasma container;
A processing apparatus for harmful component-containing gas comprising a reactive gas supply mechanism for supplying a reactive gas to the plasma container,
A detection unit that detects perfluoromethane in the harmful component-containing gas and sends a signal notifying the detection result;
A harmful component-containing gas processing apparatus, comprising: a control unit that receives a signal from the detection unit and controls the power of a microwave power source.

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