The present invention relates to an exhaust gas treatment system.
Priority is claimed on Japanese Patent Application No. 2006-19332, filed Jan. 27, 2006, the content of which is incorporated herein by reference.
Various gases are used in gas-using facilities in order to manufacture and/or treat a product such as a semiconductor, a flat display, a solar cell, a magnetic thin film and the like in accordance with manufacturing processes of the facilities. In such gas-using facilities, for example, gases such as Ar, CF4, H2, O2 and NOx are supplied to a production equipment or the like (hereinafter, a gas supplied to a gas-using facility may be described as a supply gas), processing is conducted using the gases, and then an exhaust gas is exhausted from the gas-using facilities.
In the exhausted gas, compounds including halogen such as CF4, SiF4 and C2F6, residual O2, H2 and NOx, Ar and the like, which are originated from the aforementioned gases supplied to the facilities, are included. Among them, the compounds including halogen have high Global Warming Potential, and therefore, treatment for decomposing and/or removing the composition including halogen is highly required.
Furthermore, as a case that a gas included in an exhaust gas is reused, for example, Ar included in an exhaust gas is recovered and reused. In such a case, it is necessary to remove O2, H2, NOx or the like from the exhaust gas as well as a compound including halogen.
In this way, treatment of an exhaust gas is very important.
For example, Japanese Unexamined Patent Application, First Publication No 2002-153729 discloses a method in which an exhaust gas such as those described above is mixed with a predetermined amount of water vapor wherein the amount is calculated based on the concentration of a compound including halogen within the exhaust gas, and then, the mixed gas is introduced into a discharge treatment part in order to decompose the compound including halogen and remove the decomposition products generated.
In the above treatment method of the exhaust gas, the concentration of the compound including halogen within the exhaust gas is merely measured, and the addition amount of water vapor is determined based on the measured concentration of the compound. However, since the amount of water vapor is determined merely based on the concentration of the compound including halogen in the treatment method, there is a case in which excess amount of water vapor is added to an exhaust gas due to the variation or the like of the type and/or concentration of various gas components, which are included in the exhaust gas but are different from the compound including halogen. In such a case, the discharge state at the discharge treatment part changes due to the excess water vapor, the decomposition ratio of a compound including halogen varies, and problems are caused such that removal of the compound including halogen is not conducted sufficiently.
In this way, when the conventional method is used, that is, when the method using a device, in which the amount of an additive gas such as water vapor is determined merely by measuring the concentration of a compound including halogen in an exhaust gas, is used, the optimum amount of an additive gas cannot be determined since, for example, even if other gases such as O2 and H2 which have the same functions with those of an additive gas are included in the exhaust gas, the presence of said other gases are ignored in the method when an additive gas is used (hereinafter, a gas which is added to treat an exhaust gas may be described as an additive gas). As the result, there are cases that a compound including halogen cannot be removed completely.
Furthermore, as those in the conventional method, that is, as in the method wherein the removal is conducted by measuring the concentration of a target component, which is a compound to be removed, within the exhaust gas sent from the gas-using facility, and then adding an additive gas such as water vapor in accordance with said concentration of the target component to react the additive gas with the target component and remove the target component, there are disadvantages that, if there are multiple target components to be removed or decomposed are included in the exhaust gas, plural devices are required in order to measure the concentration of each target components and equipment cost increases.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 200-153729
The object to be achieved in the present invention is to provide a system which can remove a target compound sufficiently and completely at a small cost, even if the type and/or concentration of the target compound such as a compound including halogen varies when treatment such as a plasma treatment is conducted in order to remove the target compound included in an exhaust gas exhausted from the gas-using facility such as semiconductor manufacturing equipment.
The first aspect of the present invention is an exhaust gas treatment system, which comprises:
an arithmetic processing part wherein the type of gas, the flow rate and the supply time of a gas supplied to a gas-using facility are inputted as parameters, and the type of gas, the flow rate and the supply time of an additive gas are calculated based on these parameters;
an additive gas supply part, which supplies an additive gas while controlling the type of gas, the flow rate and the supply time of the additive gas in accordance with indication signals sent from the arithmetic processing part; and
a removal part wherein the additive gas is added to an exhaust gas exhausted from the gas-using facility, and a target compound included in the exhaust gas is removed by reacting the additive gas and the target compound included in the exhaust gas.
The second aspect of the present invention is an exhaust gas treatment system which includes:
an arithmetic processing part wherein the type of gas, the flow rate and the supply time of a gas supplied to a gas-using facility are inputted as parameters, and the type of gas, the flow rate and the supply time of an additive gas to be supplied to an exhaust gas and electric power to be applied in plasma treatment are calculated based on these parameters;
an additive gas supply part, which supplies an additive gas while controlling the type of gas, the flow rate and the supply time of the additive gas in accordance with indication signals sent from the arithmetic processing part;
a power source part which controls and applies electric power in accordance with indication signals sent from the arithmetic processing part; and
a removal part wherein the additive gas is added to the exhaust gas, which comprises a compound including halogen and is exhausted from the gas-using facility, and the compound including halogen within the exhaust gas is removed by decomposing the compound including halogen by plasma treatment based on the applied electric power.
In the present invention, the arithmetic processing part can calculate the type of gas, the flow rate and the supply time of an additive gas, and furthermore can calculate electric power required in a plasma treatment if necessary, in accordance with information with regard to the type of gas, the flow rate and the supply time of a gas which is supplied to a gas-using facility. Accordingly, it is possible to apply to the treatment part the required and a sufficient amount of an additive gas and/or electric power for plasma decomposition, and therefore, the removal of a target compound such as a compound including halogen can be fully conducted.
Furthermore, according to the present invention, it is not necessary to apply an excess amount of an additive gas and/or plasma electric power, and as a result, operating cost becomes small since an additive gas and/or plasma electric power is not wasted. Furthermore, it is not necessary to use multiple devices used for measuring the concentration of each aimed component to be removed such as a compound including halogen which is included in a small amount within an exhaust gas.
Hereinafter, suitable examples of the present invention are explained, but the present invention is not limited to the examples. Any change and/or addition is possible in so far as it is included in the scope of the present invention. The number and the position of the systems can be changed as necessary.
The present invention relates to a treatment system which removes a target compound such as a compound including halogen which is included in an exhaust gas exhausted from a gas-using facility such as semiconductor manufacturing equipment. Said gas-using facility can mean any facility in so far as the facility uses gas. Preferable examples of the gas-using facility includes facilities which conduct the manufacture, treatment or the like of a semiconductor, a flat display, a solar cell, a magnetic thin film or the like. The gas which can be used in the facility is not limited, and any gas can be used as the gas used in the facility. Specific examples of the gas include Ar, CF4, H2, O2 and NOx.
Furthermore, an exhaust gas treated in the present invention can be any type of gas in so far as problems do not arise. Examples of compounds included in the exhaust gas include gases such as CF4, SiF4, C2F6, which are a compound including halogen, Ar, and residual O2, H2 and NOx.
In
The gas supplying device 2 supplies a gas. When the supplying is conducted by the device, the supplying flow rate and supplying time are measured for each type of supplied gases with one of or plurality of flow rate regulators 2A, 2B, 2C . . . 2N. In the present invention, the number of regulators can be determined optionally and can be selected if necessary. It is preferable that the number of the regulators is the same as the number of supplied gases. Each signal measured by the flow rate regulators is sent to and inputted in the arithmetic processing part 35 of the exhaust gas treatment system 3. Here, these flow rate regulators may be those used generally in the conventional gas supplying device. That is, it is possible to use a flow rate regulator which has been provided to the conventional gas supplying device. In such a case, it is not necessary to provide all of the required flow rate regulators as new members, in so far as the structure can be set such that the supplied flow rate and supplying time of each type of additive gas are measured and sent to the arithmetic processing part.
On the other hand, an exhaust gas is exhausted from the gas-using facility 1 when, for example, the manufacture of a semiconductor or the like is conducted. Various gases and compounds are included in the exhaust gas. For example, when a dry-etching process is conducted, the exhaust gas includes Ar, O2 and the like in addition to a compound including halogen such as SiF4, CF4, C2F6 or the like.
The exhaust gas exhausted from the facility is sent to the exhaust gas treatment device 3. That is, the exhaust gas is first sent to a SiF4 removal column 321 of a SiF4 removing part 32 under the condition of the reduced pressure by conducting aspiration using a vacuum pump 31 and/or 344. An adsorbent such as calcium hydroxide, calcium oxide or the like is filled in the interior of the SiF4 removal column 321, and SiF4 and the like within the exhaust gas is removed at the cyclinder. The shape and the number of the removal column, the amount of and type of adsorbent and the like can be selected as necessary.
Compounds such as SiF4 may form at the atmospheric pressure a solid of a gel-like polymer as the result of the reaction between the SiF4 and water component within an exhaust gas, and therefore deposition of the polymer may be formed in a duct. Accordingly, it is preferable that SiF4 is removed in advance under the reduced pressure as those described above.
The flow of the exhaust gas passed through the SiF4 removal column 321 enters in the SiF4 monitor 322 equipped at the down stream of the SiF4 removal column 321; and the concentration of SiF4 is measured at the monitor. After it is confirmed that the concentration of SiF4 of the exhaust gas does not exceed the allowable value, the exhaust gas is sent to a treatment part 34 to be rendered harmless. If necessary, the data of the measured SiF concentration can be sent to the arithmetic processing part 35 and be used in order to conduct a further control. It is possible to remove HF or the like as well as SiF4 in the SiF4 removal column 321.
Generally, the SiF4 removal column 321 has two columns, that is, a removal column 321A and a removal column 321B, which are placed in the parallel manner as shown in
However, the arrangement of the removal columns causes concern that when the reaction efficiency of the removal column, which is being used, deteriorates, SiF4 flows to the downstream of the column although the amount of SiF4 may be very small, and blockage of a duct may occur.
Accordingly, it is preferable that the arrangement of removal columns as those shown in
In the arrangement of
In such an arrangement, it is possible to use removal columns efficiently until the adsorption ability thereof is consumed. Furthermore, SiF4 is not sent in a duct positioned at the downstream of the SiF4 removing part 32, and therefore there is no concern that stoppage of a duct is caused.
Then, the exhaust gas is sent from the SiF4 treatment part 32 to a treatment part 34 to be rendered harmless. On the way to the treatment part 34, an additive gas supplied from an additive gas supply part 33 is added and mixed to the exhaust gas. The additive gas supply part 33 supplies the predetermined amount of an additive gas such as O2, H2, water vapor and the like wherein the amount thereof is determined by the arithmetic processing part which is described below. The arithmetic processing part 35 described below determines the type and amount of the additive gas. The additive gas may be a single gas or multiple gases, and may be a mixed gas if necessary.
In the subsequent step for the plasma decomposition, the additive gas can react as an oxidizing agent or a reducing agent for a decomposition product, which is generated by the plasma decomposition of a compound including halogen. As the result, the decomposition product generated is stabilized and becomes a chemical species which can be easily treated.
The exhaust gas to which the additive gas is mixed is introduced into a discharge part 341 of the treatment part 34 to be rendered harmless. In this part, a compound which can be decomposed by the plasma decomposition, for example, a compound including halogen such as CF4, is decomposed. Here, when hydrogen, oxygen or the like, which is originated from the additive gas, coexists at the time of the decomposition caused by the plasma discharge, constitutive atoms generated by the dissociation of the compound including halogen can become a chemical species which can be easily treated. For example, active C and F which are generated by the decomposition of CF4 become HF and CO or CO2 due to the presence of hydrogen and oxygen.
The discharge part 341 has general electrodes to which high frequency current is applied in order to excite a plasma discharge. To the electrodes, electric power, which preferably has a frequency of 2.0 to 2.4 GHz and an output of 2 to 3 kW, is applied from a high-voltage power supply part 343. The applied electric power is determined by the arithmetic processing part 35 described below.
The exhaust gas passed through the discharge part 341 includes a decomposition product generated from the compound including halogen. In the subsequent step, the exhaust gas is introduced into a gas reaction column 342. In the interior of the gas reaction column 342, a reaction agent such as calcium oxide and calcium hydroxide is filled, and the aforementioned decomposition product is removed in the column due to the reaction of the decomposition product and the reaction agent. Here, the number, the shape of the gas reaction column, the type of the reaction agent and the amount of the reaction agent can be selected if necessary.
The exhaust gas which passes through the gas reaction column 342 does not include harmful matter such as a compound including halogen, and the exhaust gas is aspirated by a vacuum pump 344 to discharge the gas out of the system.
Next, the arithmetic processing part is explained.
To the arithmetic processing part 35, data regarding the type of gas, the flow rate and the supply time of various gases, which are supplied from the gas supplying device 2 to the gas-using facility 1, are inputted. According to this data, the total amount of an exhaust gas which is exhausted from the gas-using facility 1, the flow rate and the concentration of a compound including halogen within the exhaust gas, the flow rate and concentration of an oxidizing agent such as oxygen within the exhaust gas, and the flow rate and the concentration of a reducing agent such as hydrogen, are calculated. Other data can be inputted to the arithmetic processing part if necessary. Subsequently, based on the date calculated, the optimum amount of an additive gas, and the optimum applied electric power which is required and sufficient for the plasma discharge treatment are calculated.
The aforementioned operation program includes a database which is prepared in advance. The correlations among the type of gas, the flow rate and the supply time of a gas supplied to the gas-using facility 1, and the type of gas, the flow rate and the concentration of a gas exhausted from the facility 1, wherein the correlation is obtained by conducting experiments, calculation or the like, are used as a data in the database. Furthermore, the operation program may include a database, in which the correlations among the type of gas, the flow rate and the concentration of a gas in an exhaust gas exhausted from the facility 1, the amount of an additive gas and the plasma discharge applied electric power are stored. This database may be used in combination. Due to the database, the aforementioned optimum amount of an additive gas and the optimum plasma discharge applied electric power can be calculated. The operation programs, which can be used for gas treatment concretely, are not described here since such programs can be obtained and inputted by conducting experiments, calculation or the like separately.
The optimum amount of an additive gas and the optimum plasma discharge applied electric power, which are obtained according the operation program as described above, are converted to analog signals with a D/A converter 355, and the signals are sent to the additive gas supply part 33 and the high-voltage power supply part 343. In the additive gas supply part 33, an additive gas is supplied to an exhaust gas in accordance with the sent signals. In the high-voltage power supply part 343, a plasma discharge applied electric power, which has an output value in accordance with the sent signals, is applied to the discharge part 341.
Here, changes, additions, deletions or the like are possible in the structure of the arithmetic processing part of the present invention if necessary.
Furthermore, as shown in
As described above, the optimum amount of an additive gas can be added and the optimum plasma discharge applied electric power can be applied, and therefore, an excess amount of an additive gas is not used in the present invention. Accordingly, variation of the decomposition ratio of a compound including halogen, wherein such a variation occurs due to the variation of the plasma discharging condition caused by an excess amount of an additive gas, does not occur.
Furthermore, it is possible to generate a plasma discharge in a sufficient amount properly, since an applied electric power can be determined in accordance with the amount of a compound including halogen within an exhaust gas in the present invention. An excess amount of electric power is not added, and plasma decomposition of a compound including halogen can be conducted sufficiently.
In the conventional device wherein the concentration of a compound including halogen within an exhaust gas is merely measured to determine the amount of an additive gas such as water vapor, even if another gas such as O2 and H2, which has a function similar to that of the compound including halogen, is included in the exhaust gas, the presence of another gas included in the exhaust gas is ignored, and the amount of additive gas is determined without taking into account the presence of another gas. Therefore, there is a case in which a compound including halogen cannot be removed completely. However, in the present invention, even if such an exhaust gas is treated, complete removal of a compound including halogen is possible since the amount of an additive can be determined while the presence of oxygen and hydrogen within an exhaust gas can be taken into consideration.
Ar, O2, H2 or the like is supplied to a gas-using facility 1 from a gas supplying device 2, and then an exhaust gas which includes Ar, residual O2, H2 and the like is exhausted from the gas-using facility 1. In the gas supplying device 2, an appropriate type and number of gas supply parts can be provided if necessary. As the type of additive gas which can be generally used, Ar, O2, H2 or the like can be cited.
The information with regard to the type of gas, the flow rate and the supply time of a gas, which is sent to the gas-using facility 1 from the gas supplying device 2, is sent to an arithmetic processing part 35 of the exhaust gas treatment system 3 similar to the method described above.
The exhaust gas exhausted from the gas-using facility 1 is aspirated by an exhaust pump 31, and is subsequently sent to a catalyst column 36 of the exhaust gas treatment device 3. On the way to the catalyst column 36, a gas such as H2, which is supplied from an additive gas supply part 33, is added to the exhaust gas.
In the catalyst column 36, a catalyst which consists of noble metal such as platinum, palladium and the like is filled. The number and form of the columns and the type and amount of the catalyst can be selected as necessary. In the catalyst column 36, H2O is generated by the reaction between O2 within the exhaust gas and H2 which is added, and therefore O2 within the exhaust gas is removed as H2O.
The amount of H2, which is supplied from an additive gas supply part 33, is controlled to be the optimum amount according to the instruction signal sent from a arithmetic processing part 35.
The arithmetic processing part 35 of the example of
The monitoring of the amount of H2, which is actually added in the additive gas supply part 33, is the same with those described in the aforementioned example of
In order for the exhaust gas, which includes O2 sent to the gas-using facility 1 from the gas supplying device 2, to arrives at the catalyst column 36, a certain amount of time is necessary. In order to conduct supply of an additive gas more suitably, the timing of adding an additive gas can be determined by conducting a calculation in the arithmetic processing part. That is, the time required for the gas to arrive at the column is measured in advance by experiment or the like. By setting the arithmetic processing part 35 such that an instruction signal which instructs the addition of an additive gas is given from arithmetic processing part 35 at the proper timing according to the said measured time which is required for the gas to arrive at the column, the addition of H2 can be conducted suitably according to the arrival of the exhaust gas.
In the treatment system as those in
The present invention provides a system in which a compound to be removed such as a compound including halogen within an exhaust gas exhausted from a gas-using facility can be removed completely and at a low cost even when the type of gas, the amount and the like of the target compound within an exhaust gas is changed when the target compound is removed from the exhaust gas.
Number | Date | Country | Kind |
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2006-019332 | Jan 2006 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/050525 | 1/16/2007 | WO | 00 | 7/24/2008 |