JP2007319782A - Exhaust gas treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method for recovering a reaction product as a valuable recovered matter as a fluorine raw material. <P>SOLUTION: The exhaust gas treatment method uses an exhaust gas treatment apparatus provided with an absorbent transfer type reactor (5) and an absorbent fixed type detoxifier (10). The reactor (5) causes decomposition product gas formed by the decomposition of PFC gas to act on the absorbent to allow them to react with each other. The absorbent after the reaction is separated into a surface layer part rich in a reacted portion and a core part rich in the unreacted portion. The core part after the separation is returned to the reactor (5). The surface layer part after the separation is classified into fine particles and medium particles by a classification means (7), the fine particles after the classification is recovered, and calcium-based powder is mixed with the medium particles to form a fluorine absorbent. The fluorine absorbent is supplied to the detoxifier (10). The decomposition product gas which is formed by the decomposition of PFC gas and is to be introduced into the detoxifier (10) is diluted, water is added in a controlled quantity to the diluted decomposition product gas, and the decomposition product gas added with water is reacted with the fluorine absorbent in the detoxifier (10). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention reacts hydrogen fluoride (HF) produced by decomposition (combustion) of PFC gas (Perfluoro Compounds gas) used in the manufacturing process of semiconductor devices and liquid crystal display devices with a calcium-based absorbent. The present invention also relates to an exhaust gas treatment method for recovering the reaction product (CaF ₂ ).

  PFC gas used in semiconductor manufacturing processes such as manufacturing processes for semiconductor devices and liquid crystal display devices needs to be reduced in use and reduced to the atmosphere from the viewpoint of preventing global warming. In recent years, in order to reduce atmospheric emissions, detoxification treatment has been carried out by an exhaust gas treatment technology that introduces a PFC gas decomposition device and removes hydrogen fluoride (HF) from the decomposition exhaust gas.

As an exhaust gas treatment apparatus for decomposing PFC gas and treating the decomposed exhaust gas, one disclosed in Patent Document 1 is known. This exhaust gas treatment apparatus passes cracked exhaust gas through an absorbent transfer type reactor, reacts hydrogen fluoride (HF) in the cracked exhaust gas with limestone, which is an absorbent in the reactor, to generate hydrogen fluoride from the exhaust gas. Remove. Then, the limestone is taken out from the bottom of the reactor described above, and the surface layer portion rich in the reacted portion and the core portion rich in the unreacted portion are separated by a separator, and the core portion is returned to the reactor. Reuse the surface layer using a classifier using a vibrating sieve, and fine particles with a diameter smaller than the particle diameter of 0.1 to 1.5 mm and a diameter larger than the particle diameter. It is divided into medium grains and collected separately.
JP 2005-28241

However, in the conventional absorbent transfer type exhaust gas treatment device disclosed in Patent Document 1, the limestone (absorbent) that has reacted with the exhaust gas is separated into a surface layer portion and a core portion, and the core portion is used as the treatment device. It is returned and reused, and the surface layer portion is separated into fine particles and medium particles by means of a vibrating sieve, and recovered, but the diameter less than 0.15 mm is fine, from 0.15 mm to 2.5 mm When the content is less than medium, the weight ratio of fine particles to medium particles is 1: 9, and the proportion of calcium fluoride (CaF ₂ ) in fine particles (10%) is 40 wt%, calcium oxide (CaCO ₃ ) Is 60 wt%, the ratio of calcium fluoride (CaF ₂ ) in the middle grains (90%) is 5 wt% or less, and the ratio of calcium oxide (CaCO ₃ ) is 95 wt% or more. In this case, if there is only a medium grain, it can be reused as limestone for waste hydrofluoric acid treatment. However, if the proportion of calcium fluoride in the fine grain is as high as 40 wt%, this fine grain is produced in the iron making process. It cannot be used for dephosphorization / desulfurization in Japan, and this fine granule becomes a large amount of industrial waste, and it is difficult to make it a valuable recovery as a fluorine raw material.

  This invention pays attention to such a point, and it aims at providing the method of collect | recovering as valuable collection | recovery as a fluorine raw material.

  In order to achieve the above-described object, the invention disclosed in claim 1 is directed to treating exhaust gas using an exhaust gas treatment apparatus including an absorbent-transfer reactor and an absorbent-fixed detoxifier. In the absorbent transfer type reactor, the decomposition product gas generated by the decomposition of the PFC gas is allowed to act on the absorbent moving in the reactor to react with the absorbent, and the reacted absorbent is already reacted. The surface layer portion is separated into a core portion rich in unreacted content and the core portion rich in unreacted components, and the core portion is returned to the absorbent transfer reactor and reused. The fine particles after classification are collected, and the calcium-based powder is mixed with the middle particles to form a fluorine absorbent, and this fluorine absorbent is supplied to the above-described absorbent-fixed detoxifier. Decomposition produced by decomposition of PFC gas introduced into absorbent-type abatement device The produced gas is diluted with air or nitrogen, and moisture is added to the diluted decomposition product gas, and the decomposition product gas to which the moisture is added reacts with the fluorine absorbent in the absorber-fixed detoxifier. Thus, the reaction product is recovered as a substitute for fluorite.

  The invention disclosed in claim 2 is the invention of claim 1, wherein the classifying means is constituted by a vibration sieve, the particle size of the sieving is 0.15 mm, the diameter is less than 0.15 mm, and the diameter is 0.15 mm. More than 2.5 mm is classified as a medium grain. Furthermore, the invention disclosed in claim 3 is characterized in that, in the invention of claim 1 or 2, the mixture of the medium grains and the calcium-based powder is granulated into granules to obtain a fluorine absorbent.

  In the present invention, the decomposed product gas generated by the decomposition of the PFC gas is introduced into the absorbent transfer reactor, so that the reacted absorbent is separated into a surface layer portion rich in already reacted components and a core portion rich in unreacted components. The core part is returned to the absorbent transfer reactor, and the surface layer part is supplied to the classifying means, and classified into fine grains finer than the predetermined particle diameter and medium grains coarser than the predetermined particle diameter, Fine particles after classification are recovered. By adjusting the transfer rate of the absorbent in the absorbent transfer reactor, the weight ratio of fine particles to medium particles is 15 wt%: 85 wt%. Since the ratio of calcium fluoride in the steel can be 60 wt% or more, the recovered fine particles can be used for dephosphorization / desulfurization in the iron making process, and the fine particles can be used as valuable recovery products. .

In addition, after mixing the calcium-based powder into the middle particles after classification, it is introduced into the absorbent-fixed type detoxifier and reacted with the absorbent in the absorbent-fixed type detoxifier. The decomposition product gas generated by the decomposition of the PFC gas introduced into the agent-fixed type detoxifier is diluted with air or nitrogen, and moisture is added to the diluted decomposition product gas. And the fluorine absorbent in the absorber-fixed detoxifier, the reactivity between the fluorine compound in the decomposition product gas and the absorbent increases, and the reaction that has stopped at the surface of the absorbent It will proceed to the inside of the absorbent. As a result, the reaction efficiency is improved particularly in the temperature range of 100 ° C. to 150 ° C., which has been low in reactivity, and fluorine can be stably recovered regardless of the temperature of the introduced gas. Along with this, the fluorine recovery capability is improved, and the industrial reuse of the absorbent after the reaction is facilitated.
In other words, due to the exhaust gas treatment with the fixed absorbent, the absorbent (limestone) that reacted with the diluted decomposition product gas becomes high-purity calcium fluoride, which can be reused as a raw material for producing PFC gas and has industrial utility value. High raw material. Therefore, 100% can be recovered as a valuable recovery material as a fluorine raw material (fluorite substitute).

FIG. 1 is an exhaust gas treatment system diagram according to the embodiment of the present invention.
For example, in the film formation process in the semiconductor device manufacturing process, a raw material gas such as silane gas (SiH ₄ ) is supplied to the CVD apparatus (1) from the introduction pipe (L1), and decomposed in the CVD apparatus (1) to decompose the surface of the substrate. Since a silicon film or the like is formed on the substrate, a reactive silicon compound such as amorphous silicon and other side reaction products are generated in the CVD apparatus (1). Since these silicon compounds adhere to and deposit on the surface of the CVD apparatus (1) and this deposit adheres to the film-forming surface of the substrate, the quality of the product may be deteriorated. Cleaning is performed by supplying a PFC gas such as NF ₃ into (1).

  In the cleaning process, PFC gas as a cleaning gas is supplied from the cleaning gas introduction pipe (L2) to the CVD apparatus (1), reacts with the reactive silicon compound deposited in the CVD apparatus (1), It is diluted with nitrogen gas together with the PFC gas of the reaction, and is sent to an absorbent transfer type exhaust gas treatment device (2) and an absorber fixed type exhaust gas treatment device (3) described later.

  The absorbent transfer type exhaust gas treatment device (2) includes a combustion part (4) for decomposing the PFC gas, a reactor (5) for moving the absorbent inside, a surface layer part and a core part of the absorbent. A surface layer peeling means (6) for separating the water and a classifying means (7) composed of a vibrating sieve for introducing and classifying the separated surface layer portion.

  The absorbent-fixed exhaust gas treatment device (3) has a combustion part (8) for decomposing the PFC gas, a dust removing part (9), and an absorbent-fixed dry detoxifier (10). And a diluting gas introducing means (11) such as nitrogen gas is provided between the combustion section (8) and the dust removal section (9), and moisture is provided between the dust removal section (9) and the dry detoxifier (10). Supply means (12) is provided.

  The absorbent taken out from the absorbent outlet (13) of the classifying means (7) of the absorbent transfer type exhaust gas treatment device (2) is absorbed through the mixer (14) and the granulator (15). It is supplied to the dry type detoxifier (10) of the exhaust gas treatment device (3) of the agent fixed type.

The PFC gas discharged from the CVD apparatus (1) is supplied to the absorbent transfer type exhaust gas treatment apparatus (2) and the absorbent fixed type exhaust gas treatment apparatus (3) for processing.
In the absorbent transfer type exhaust gas treatment device (2), hydrogen fluoride (HF) as a decomposition product gas is generated by a reaction between water and PFC gas generated by combustion of combustion gas in the combustion section (4). This decomposition product gas is introduced into the reactor (5), brought into contact reaction with the absorbent flowing in the reactor (5), and the treated exhaust gas is sent to a chimney (not shown) via an induction fan (16). Be paid.

  On the other hand, the absorbent that contacts and reacts with the cracked gas in the reactor (5) is composed of limestone that moves downward in the reactor (5), and the movement has an operation period and a stop period. The intermittent operation is repeated at a predetermined interval, and the pulsation is controlled so that the movement and the stop are repeated at a specified interval even in the operation period. The absorbent (limestone) reacts with the decomposition product gas (HF) to generate calcium fluoride on the surface layer.

  The absorbent in contact with the cracked product gas in the reactor (5) is rich in the reaction portion in the surface layer portion, but rich in the unreacted portion in the core portion. And since the surface layer of limestone reacted with hydrogen fluoride etc. is softer than the unreacted core part, this absorbent is introduced into the surface peeling means (6) constituted by a perforated cylindrical rotating body. During the rotational movement, the surface layers of the absorbent rub against each other and separate into a surface layer portion rich in the reacted components and a core portion rich in the unreacted components. Of the separated absorbent, the core part with a diameter of 2.5 mm or more is returned to the upper part of the reactor (5) and reused, and the surface layer part rich in the existing reaction is sent to the classifying means (7). To do.

The classifying means (7) is composed of a vibration device (not shown) and an approximately 100 mesh sieving tool. The surface layer portion fed from the surface peeling means (6) is screened by 0.15 mm. The particles are classified as a particle size. Fine particles having a diameter of less than 0.15 mm and medium particles having a diameter of 0.15 to 2.5 mm are used. In this case, the fine particles have a higher fluorine content than the medium particles. By the way, the absorbent transfer rate in the reactor (5) is intermittently operated at 8min / Hr to 8min / 1.5Hr, and the absorbent is moved at a transfer rate of 6m / Hr to 3.6m / Hr. Further, the weight ratio of the recovered fine particles to the medium particles is 15 wt% for the fine particles and 85 wt% for the medium particles, and the calcium fluoride (CaF ₂ ) in the fine particles is 60 wt% or more, and the calcium fluoride in the medium particles (CaF ₂ ) was around 10 wt%. Since the calcium fluoride (CaF ₂ ) in the fine particles is 60 wt% or more, the recovered fine particles become a valuable recovered material that can be used as a raw material for dephosphorization / desulfurization in the iron making process.

The intermediate grains classified and sent out by the classification means (7) are supplied to the mixer (14), where calcium-based powders such as calcium carbonate (CaCO ₃ ) and calcium hydroxide (Ca (OH) ₂ ) And mixed into a fluorine absorbent, and this fluorine absorbent is fed to a granulator (15) to be granulated, and the granulated fluorine absorbent is used as an absorbent-fixed exhaust gas treatment device (3 ) Is supplied to the dry detoxifier (10). In this example, the fluorine absorbent, which is a mixture of medium grains and calcium-based powder, is granulated to form granules, but may be a mixture of medium grains and powder without granulation. It is desirable to granulate from the convenience of use in a dry type abatement device.

In the absorbent-fixed exhaust gas treatment device (3), hydrogen fluoride (HF) as a decomposition product gas is generated by a reaction between water and PFC gas generated by combustion of combustion gas in the combustion section (8).
This decomposition product gas is introduced into the dust removal section (9) together with a diluent gas such as nitrogen gas, dust is removed from the decomposition product gas, and the decomposition product gas from which the dust has been removed is supplied from a water supply means (12) such as a sprayer. A moisture is added in a metered amount, and the decomposition product gas to which the moisture has been added is sent to the dry detoxifier (10), and this decomposition product gas is reacted with the fluorine absorbent in the dry detoxifier (10). The reaction product, calcium fluoride (CaF ₂ ), is recovered as a fluorite substitute.

  The dry type abatement device (10) is composed of a plurality (three in the figure) of reaction tubes (10a), (10b), and (10c) that are used for switching, and each reaction tube (10a) (10b) (10c ) Is filled with a fluorine absorbent formed into pellets, briquettes, granules or honeycombs.

In the dry detoxifier (10), the calcium fluoride produced in each reaction tube (10a), (10b), and (10c) is removed from each reaction tube (10a), (10b), and (10c) when a predetermined reaction rate is reached. Take out and collect in the recovery container (16), feed the recovered calcium fluoride and new calcium fluoride to the mixer (17) and mix them, and combine the recovered calcium fluoride with the new calcium fluoride. Is supplied to the PFC gas (NF ₃ ) production device (18) to produce PFC gas, and the reaction product in the dry detoxifier (10) is reused as a fluorine source that is a raw material of PFC gas . Note that the decomposition product gas treated by the dry abatement device (10) is discharged out of the system from the discharge passage (19) as a harmless gas.

  In the above-described exhaust gas treatment system, a CVD apparatus has been described as an example of an apparatus using PFC gas. However, the present invention is not limited to this, and PFC gas decomposition reaction in an etching apparatus or other apparatus using PFC gas. Needless to say, it can be applied as a gas processing technique.

  Also, in the absorbent-fixed exhaust gas treatment device (3), the sprayer has been described as an example of the moisture supply means (12) for adding moisture to the diluted process gas (decomposition product gas). In addition to the addition of mist-like water using, water vapor may be added at a high temperature by a water vapor generator as necessary. Thus, the reactivity of a fluorine compound and an absorbent can be enhanced by adding water in a quantitatively controlled manner to the PFC dilution decomposition product gas introduced into the dry type detoxifier (10).

  FIG. 2 shows a schematic configuration diagram of a test apparatus for examining the relationship between the introduced gas temperature and the reaction rate using the amount of water added as a parameter. This test apparatus is a hot air line (25) in which a blower (22), a flow meter (23), and a hot air generator (24) are arranged in series at an inlet (21) of a reaction tube (20) filled with a fluorine absorbent. ), An HF supply line (28) having an HF storage cylinder (26) and a flow meter (27) on the hot air line (25) on the outlet side of the hot air generator (24), and an atomizer (29) The HF gas is analyzed at the outlet (31) side of the reaction tube (20).

As test conditions in this test apparatus, the flow rate of HF for flowing the HF supply line (28) was 5 L / min. On the other hand, the amount of dilution air added through the hot air line was 1 m ³ / min. Therefore, the HF concentration in the introduced gas is 0.5%. In this case, the absolute humidity in the diluted air was 8 g / m ³ .

A dry state C in which moisture is not added to the diluted HF gas (a relative humidity of 50% at a temperature of 20 ° C., an absolute humidity of 8 g / m ³ ), and a water addition state B in which the amount of added water is 12 g / min ( Absolute humidity: 20 g / min) and water addition state A (absolute humidity: 30 g / min) with an added water amount of 22 g / min. Three types of diluted HF gas are generated, and the temperature conditions are 50 ° C. and 100 ° C. Twelve types of each diluted HF gas to be tested, each set at 150 ° C. and 250 ° C., were introduced into the reaction cylinder (20), and the reaction rate was examined.

  The result is shown in FIG. Each diluted HF gas is as indicated by the polygonal lines A, B, and C. Compared to those in the dry state C, the reaction rate increases by about 10% in the temperature range of 100 to 150 ° C. in the moisture addition state B, In the addition state A, the result was also increased by about 20%. As described above, it has been proved that the reactivity between the absorbent and the HF gas can be further increased by adding moisture under quantitative control.

Note that, as shown in this embodiment, although the increase reaction rate is sufficient to control the range of 20 to 30 g / m ³ as an absolute humidity, so as to control the absolute humidity in the range of greater than 30 g / m ³ May be. However, since the degree of corrosion by HF is accelerated when the absolute humidity becomes too high, the upper limit of the absolute humidity is preferably about 50 g / m ³ .

  INDUSTRIAL APPLICABILITY The present invention can be used for an abatement technique in a manufacturing process of a semiconductor device, a liquid crystal display device or the like.

It is an exhaust gas treatment system diagram concerning the embodiment of the present invention. It is a schematic block diagram of the test apparatus which investigates the relationship between the introductory gas temperature and reaction rate which made the moisture addition amount the parameter. It is a graph which shows the relationship between introduction gas temperature and reaction rate.

Explanation of symbols

5 ... Absorber transfer type reactor, 7 ... Classifying means, 10 ... Absorber fixed type abatement device.

Claims (3)

An exhaust gas treatment method in an exhaust gas treatment apparatus comprising an absorbent transfer type reactor (5) and an absorbent fixed type detoxifier (10),
In the absorbent transfer type reactor (5), the absorbent moving in the reactor (5) is caused to react with the absorbent by the decomposition product gas generated by the decomposition of the PFC gas, and the reaction is performed. The absorbent is separated into a surface layer portion rich in already reacted components and a core portion rich in unreacted components, and this core portion is returned to the absorbent transfer reactor (5) and reused, and the surface layer portion is reused. Classifying means (7) classifies fine particles and medium particles, collects the fine particles after classification, mixes calcium powder with the intermediate particles to form a fluorine absorbent, and absorbs the fluorine absorbent as described above. The decomposition product gas generated by the decomposition of the PFC gas supplied to the agent-fixed detoxifier (10) and introduced into the absorbent-fixed detoxifier (10) is diluted with air or nitrogen, and the diluted decomposition Water is added to the product gas in a metered amount, and the decomposition product gas to which this water is added and the absorbent fixed detoxifier (10) By reacting a fluorine absorber, exhaust gas treatment method characterized by recovering the reaction product as fluorite replacement. The classification means (7) is a vibrating sieve, wherein the particle size of the sieve is 0.15 mm, the diameter is less than 0.15 mm, and the diameter is 0.15 mm or more and less than 2.5 mm as the middle grain. The exhaust gas treatment method described. The exhaust gas treatment method according to claim 1 or 2, wherein a mixture of the medium grains and the calcium-based powder is granulated into a fluorine absorbent.

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