JP3866412B2 - Semiconductor manufacturing exhaust gas removal method and removal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for removing exhaust gas generated in the manufacture of electronic circuit elements such as semiconductors and liquid crystals.
[0002]
[Prior art]
Raw materials used for manufacturing electronic circuit elements such as semiconductors and liquid crystals are called process gases, and are roughly classified into depositing gases and etching gases. The former includes SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , TEOS, PH ₃ , B ₂ H ₆ , NH ₃ , WF ₆ , N ₂ O, H _{2 and the} like as representative examples, and the latter includes NF ₃ , C ₂ F ₆ , CHF ₃ , CF ₄ , SF _6, etc., all of which are hazardous gases that are toxic, flammable (explosive) or corrosive.
[0003]
Since these gases cannot be released on a global scale, let alone detrimental to the human body, they must be removed by any means. Yes. Typical examples include dry adsorption, wet scrubber, electrothermal oxidative decomposition, and flame combustion abatement, each having its advantages and problems. For example, dry adsorption is easy to handle and consumes less energy, but the processing capacity per unit is limited, leaving a problem in the disposal of used adsorbents and requiring considerable costs. Wet scrubbers are not always easy to detoxify to the target gas concentration.
[0004]
Flame combustion removal has a wide range of application fields for gas to be treated, but remains uneasy about safety during operation, and also remains a problem in the treatment of dust and corrosive gases that are by-produced during removal. That is, in the flame combustion method abatement using petroleum-based liquid or gas fuel, basically a burner is used for combustion, and exhaust gas is introduced into the combustion atmosphere to oxidatively decompose. (1) Burner (2) Unsafe situation when the flame disappears for some reason, (3) Complicated and enlarged equipment for removing dust, cleaning and cooling the treated gas with a central scrubber There is a point.
[0005]
The electrothermal oxidative decomposition method is currently the most widespread detoxification method. In detoxifying process gas exhaust gas used in the manufacture of electronic circuit elements such as semiconductors, it is easy to control the process and make it a compact device. As a method that can be assembled and is easy to handle safely, an oxidation thermal decomposition type abatement apparatus and method using an electric heater has been proposed (Japanese Patent Laid-Open No. 7-323211).
[0006]
However, although the electric heater is clean, there is a problem that the energy cost is high. In addition, the generation of high temperature of 1000 ° C. or higher has a limit in terms of the material of the heating element and the protective tube, and there is also a limit to the large air volume treatment. In particular, it seems that it is not very suitable for use in the detoxification of PFC that requires a high decomposition temperature.
[0007]
Typical examples of PFCs used for etching (cleaning) today include C ₂ F ₆ , CHF ₃ , CF _4, etc., but if these are simply pyrolyzed in the presence of O ₂ , the bonds in these compounds The necessary temperature order follows the order of the binding energy because it is cut and decomposed from the weak energy part.
[0008]
That is, it is cleaved and decomposed in the order of C ₂ F ₆ <CHF ₃ <CF ₄ (binding energy is 98, 106, 130 (each kcal / mol), respectively). Also, C ₂ F ₆ and CHF ₃ cause CF ₄ by-product in the thermal decomposition process, and as a result, CF ₄ detoxification technology is required for PFC heat release damage.
[0009]
In order to perform simple thermal decomposition of a PFC having such binding energy using the above-mentioned apparatus of JP-A-7-323211, temperatures of at least 1000, 1200, 1400 ° C. or more are required in each of C ₂ F ₆ , CHF ₃ and CF _4. And However, it is not always easy to form such a high-temperature atmosphere with an electric heater alone, and there is a problem in actual implementation because the energy cost becomes expensive.
[0010]
Therefore, any of the conventional abatement methods described above has the following performances: (1) safety, (2) work stability, (3) running cost, (4) abatement performance (including processing air volume). It can be said that it is insufficient.
[0011]
[Problems to be solved by the invention]
In view of such a current situation, there is a detoxification means that can safely and stably carry out the detoxification process, and can reduce exhaust gas below its TLV (allowable concentration) while suppressing running costs by using a minimum amount of energy. It has been demanded.
[0012]
Therefore, an object of the present invention is to provide means for achieving a sufficiently high temperature state with a small energy cost in an abatement method using an electric heater.
[0013]
[Means for Solving the Problems]
The present invention copes with the problem that the heat source is composed of _two electric heaters and a hydrocarbon fuel containing H ₂ and CO.
[0014]
Abatement process for producing semiconductor devices exhaust gas according to claim 1, the reaction tube equipped with an electric heater (5) (4a), the heat exchanger upper end opening portion thereof is opened in the central portion of the installation place of the electric heater (5) body (3b) and provided with an upper end opening reaction column a semiconductor manufacturing exhaust gas discharged from the portion (4a) the heat exchanger a high temperature oxidation decomposing detoxifying method at the body of the heat exchanger body (3b) A fuel gas supply pipe (2) is inserted into (3b), and a fuel gas obtained by mixing preheated air and hydrocarbon fuel containing H ₂ and CO is supplied to the fuel gas supply pipe (2). It is characterized by supplying to .
[0015]
The method for removing semiconductor manufacturing exhaust gas according to claim 2 is characterized in that the water-soluble component gas and / or hydrolysis component gas in the semiconductor manufacturing exhaust gas containing at least one of water-soluble component gas or hydrolysis component gas and thermal decomposition component gas. the a scrubber (1) for washing is removed, the reaction tube equipped with an electric heater (5) and (4a), the heat exchanger body which is opened at the center portion of the installation location of the upper end opening portion electric heater (5) (3b ), And a high temperature oxidative decomposition of the washing exhaust gas discharged from the upper end opening of the heat exchanger body (3b) in the reaction tube (4a) , and the heat exchanger body (3b) has a fuel gas supply pipe (2) is inserted, and wherein the supplying the fuel gas and the hydrocarbon fuel containing the preheated air and H _2, CO, which are mixed to the fuel gas supply pipe (2) To do.
[0016]
The method for removing semiconductor manufacturing exhaust gas according to claim 3 is the method for removing semiconductor manufacturing exhaust gas according to claim 1 or claim 2, wherein the electric heater (5) in the reaction tube (4a) is made of fuel gas (F5). It is used for ignition and is characterized in that energization of the electric heater (5) is stopped after fuel gas ignition.
[0017]
The semiconductor production exhaust gas abatement apparatus according to claim 4 is a method for producing water-soluble component gas and / or hydrolysis component gas in semiconductor production exhaust gas containing at least one of water-soluble component gas and hydrolysis component gas and thermal decomposition component gas. A scrubber (1) to be washed and removed, a reaction cylinder (4a) equipped with an electric heater (5) , and an upper end opening of the reaction cylinder (4a) are opened at the center of the installation place of the electric heater (5) , and the washing exhaust gas is discharged into the reaction cylinder (4a The heat exchanger body (3b) discharged into the heat exchanger and the fuel gas inserted into the heat exchanger body (3b) and mixed with preheated air and hydrocarbon fuel containing H ₂ and CO are heat exchanged. And a fuel gas supply pipe (2) to be supplied to the main body (3b) .
[0018]
In the present invention, the electric heater is always kept in a heated state (for example, a heater surface temperature of 700 ° C.), exhaust gas to be treated is introduced into a reaction tube under the atmosphere, and external air is used as a carrier gas, and H ₂ , A fuel gas mixed with a hydrocarbon-based fuel having a predetermined concentration containing CO is introduced.
[0019]
In this case, the fuel gas is simply mixed with the exhaust gas introduction and supplied to the reaction cylinder without using a commonly used burner-structure device, and is ignited by heating of an electric heater provided in the reaction cylinder. Therefore, a burner is unnecessary and the problem of burner tip clogging does not occur.
[0020]
In the reaction cylinder, the hydrocarbon fuel is immediately pyrolyzed and oxidatively decomposed by the external air coexisting as a carrier gas, and combustion heat is generated in the process to form the desired atmospheric temperature together with the heating value of the electric heater. it can.
[0021]
That is, the problem is solved by using both electric energy and fuel gas as heat sources. As a result, the increase in energy cost is greatly suppressed as compared with the case of using electric energy alone, the formation of a high temperature region of 1000 ° C. or higher is facilitated, and the range of exhaust gas that can be treated is widened.
[0022]
In addition, since different energy sources are used, the processing temperature can be maintained by combustion of the fuel gas even when the electric heater stops heating due to a power failure or the like during the operation of the abatement system. Is expensive.
[0023]
The electric heater may be used as a fuel gas ignition source, and after the gas ignition, the current may be cut off and the fuel gas may be heated only by combustion of the fuel gas.
[0024]
When an electric heater is fixed and a gas to be processed is flowed around it and heat energy is applied, a residence time is required for decomposition, and therefore the processing temperature is influenced in proportion to the amount of processing gas flow. However, when the gas to be treated and the exothermic fuel gas are introduced at the same time as in the present invention, since the stirring effect of both gases is taken into account, the influence of the residence time due to the air volume is small, and sufficient decomposition is possible even when the gas volume of the process gas is large. It can be performed.
[0025]
Petroleum is a typical example of the hydrocarbon fuel containing H ₂ and CO used in the present invention, but a gas mainly composed of hydrocarbon may be used. Examples include, but are not limited to, LPG (liquefied natural gas), city gas, kerosene, light oil, and heavy oil.
[0026]
The material constituting the electric heating element, its protective cylinder, and reaction cylinder needs to have a heat resistance of at least 1000 ° C. or more. Therefore, ceramic is suitable as a constituent component, and a non-metallic heat-resistant material is suitable for the heating element, typically SiC, but a metal material can also be used as long as it has heat resistance.
[0027]
Similar to the device proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-323211, if a water storage tank is placed at the lower part of the device, the reaction cylinder is provided at the center, and the scrubber devices are provided before and after that, they are brought in as exhaust gas. Most of the water-soluble or hydrolyzable components such as F ₂ and SiF ₄ are detoxified by the preceding scrubber device, and the amount introduced into the reaction cylinder can be greatly reduced. Therefore, the load of detoxification in the reaction cylinder can be reduced by that amount. Further, the exhaust gas after the decomposition treatment is cleaned with a scrubber at the subsequent stage and cooled, whereby the air emission gas can be purified. This makes it possible to remove PFC that is difficult to be thermally oxidized and decomposed even with a compact device.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to preferred embodiments.
[0029]
FIG. 1 is a diagram showing an outline of the abatement apparatus of the present embodiment. In FIG. 1, (1) is a scrubber provided on the inlet side, and is connected to a semiconductor manufacturing apparatus by a duct (14), and semiconductor manufacturing exhaust gas (F1) is introduced here.
[0030]
The scrubber (1) on the inlet side is erected on the water tank (12) and has a spray nozzle (1a) and a cylindrical portion (1b). The lower part of the cylindrical part (1b) is immersed in the stored water (12a) of the water tank (12). The spray nozzle (1a) is installed in the ceiling portion and sprays water downward.
[0031]
A circulating water pump (10) is installed between the spray nozzle (1a) and the water tank (12), and the stored water (12a) in the water tank (12) is pumped to the spray nozzle (1a). It has become. Further, city water is supplied to the circulating water pump (10), and the stored water (12a) in the water tank (12) and the city water are mixed and pumped.
[0032]
The pyrolysis device (4) is installed integrally on the heat exchanger (3), and both (3) and (4) are adjacent to the scrubber (1) on the inlet side and on the water tank (12). is set up.
[0033]
The heat exchanger (3) includes a cylindrical casing (3a), a heat exchange body (3b) housed inside the cylindrical casing (3a), and a heat insulating material (13) wound around the outer periphery of the cylindrical casing (3a). The heat exchange device main body (3b) communicates with the cylindrical portion (1b) of the scrubber (1) through the communication pipe (15).
[0034]
The thermal decomposition apparatus (4) includes a reaction tube (4a), an electric heater (5) installed in the reaction tube (4a), and a heat insulating material (13) wound around the outer periphery of the reaction tube (4a). The upper end opening of the heat exchanger body (3b) is opened at the center of the installation location of the electric heater (5), and the preheated flushing exhaust gas (F2) is the electric heater (5). It is discharged to the thermal decomposition zone of the installation part. The internal space volume of the reaction cylinder (4a) is about 30 liters, and the inside is covered with an alumina-based refractory material. As the electric heater (5), for example, six electric heaters in which a non-metallic (or metallic) heating element such as SiC is loaded on an alumina ceramic tube are used.
[0035]
The dust discharge device (6) is in the form of a nozzle connected to a high-pressure gas source (or high-pressure water source), and high-pressure jet gas (or high-pressure water) (16) is jetted from its opening. In this embodiment, the dust discharge device (6) is installed at the ceiling portion, the middle portion of the thermal decomposition device (4), the bottom opening portion of the heat exchanger (3), and the entrance of the scrubber (7). A compressed jet gas (16) is jetted out. The installation location of the dust discharge device (6) is not limited to the above-described position, and a required number of installations can be installed at necessary locations.
[0036]
The scrubber (7) on the outlet side is installed on the ceiling of the water tank (12), and the pyrolysis exhaust gas (F3) flowing into the water tank (12) from the bottom opening of the heat exchanger (3) is water. It flows in through the space between the ceiling of the tank (12) and the water surface. The scrubber (7) has, for example, a structure in which a number of baffle plates (7b) and a spray nozzle (7a) are incorporated.
[0037]
An exhaust duct (9) is installed at the outlet of the outlet side scrubber (7), and an exhaust fan (8) is installed in the middle.
[0038]
Then, the semiconductor manufacturing exhaust gas (F1) discharged from the semiconductor manufacturing facility is introduced into the introduction part through the duct (14), and washed with the mist-like high-pressure water ejected from the spray nozzle (1a). The high-pressure water ejected from the spray nozzle (1a) is effectively in gas-liquid contact with the semiconductor manufacturing exhaust gas (F1), and the water-soluble component or hydrolysis component in the semiconductor manufacturing exhaust gas (F1) is in contact with the spray water. It is decomposed or dissolved and removed.
[0039]
For the water tank (12), always supply fresh water (city water) to the circulating water pump (10), while the same amount of treated water from the drain duct (11) overflows from the water tank (12) or bottom. To eliminate.
[0040]
Insert the fuel gas supply pipe (2) into the heat exchanger body (3b) of the heat exchanger (3) from the maintenance door (18) formed in the cylindrical part (1b) of the scrubber (1) through the communication pipe (15). Then, air necessary for the oxidation thermal decomposition is supplied to the cleaning exhaust gas by the air supply pump (22) and mixed. (21) is a preheating unit that preheats external air to at least 200 to 300 ° C., and hydrocarbon-based fuel supplied from the fuel supply unit (20) is mixed with the preheated air to form fuel gas (F5). Is done. By mixing the fuel gas (F5), the concentration of the cleaning exhaust gas (F2) is reduced below the allowable concentration for explosion.
[0041]
The fuel gas supply pipe (2) may be inserted up to the entrance of the heat exchanger body (3b) as shown by a solid line, or penetrates the heat exchanger body (3b) as shown by a virtual line. Alternatively, air may be mixed in the communication pipe (15) to the cylindrical portion (1b). In order to sufficiently mix the cleaning exhaust gas (F2) and air, it is better to mix on the cylindrical part (1b) side, but from the viewpoint of safety, it penetrates the heat exchanger body (3b). It is desirable to arrange them.
[0042]
The flushed exhaust gas (F2) washed by the scrubber (1) on the inlet side enters the heat exchanger body (3b) of the heat exchanger (3) via the communication pipe (15). Here, the high temperature cracked gas (F3) mixed with the fuel gas and oxidized and decomposed by high temperature heating in the heat cracking device (4) at the top of the device as described above and the wall of the heat exchanger body (3b) The heat energy is exchanged through the heat exchanger, and is discharged from the upper end opening of the heat exchanger main body (3b) in a state where the temperature is preheated and enters the oxidation pyrolysis zone of the thermal cracking apparatus (4).
[0043]
The cleaning exhaust gas (F2) to be treated descends along the surface of the electric heater (5) and is thermally decomposed.
[0044]
Oxidized high-temperature decomposition exhaust gas (F3) generates a large amount of dust (17), and this is generated in the heat exchanger body (3b) installed on the outer periphery of the electric heater (5) and below the electric heater (5). Since it accumulates on the outer periphery, the accumulated dust (17) is removed by the dust discharger (6).
[0045]
The flushed exhaust gas (F2) descends from the thermal decomposition unit (4) toward the heat exchanger (3) while generating a large amount of dust (17) as the oxidation process proceeds, and the heat exchanger main body (3b) The flushed exhaust gas (F2) rising in the heat exchanger body (3b) from the outer periphery through the wall is heated. The pyrolysis exhaust gas (F3) having been subjected to heat exchange in this way enters the water tank (12) from the lower surface opening of the heat exchanger (3), and between the ceiling surface and the water surface of the water tank (12). Is introduced into the exit-side scrubber (7). The introduction of the cracked exhaust gas (F3) into the scrubber (7) is performed by the suction action of the exhaust fan (8).
[0046]
Part of the dust (17) is deposited and deposited in the electric heater (5) and the heat exchanger (3), but most of the dust falls with the high-temperature decomposition exhaust gas (F3), and most of it falls in the water tank (12 ) Pours over the stored water (12a) in) and sinks.
[0047]
The cracked exhaust gas (F3) containing the dust (17) introduced into the scrubber (7) on the outlet side is effectively washed and deprived of heat by the water spray from the spray nozzle (7a) and the baffle plate (7b). It becomes low temperature and becomes clean low temperature exhaust gas (F4), which is released into the atmosphere from the exhaust duct (9).
[0048]
Part of the stored water (12a) in the water tank (12) is discharged out of the water tank (12) through the drainage duct (11). In this case, if necessary, a filter (not shown) may be installed in front of the drain duct (11) to remove dust as a solid matter.
[0049]
Further, in the apparatus of the present invention, the washing exhaust gas (F2) can be preheated by installing the heat exchanger (3), heat recovery becomes possible, and the thermal energy burden on the electric heater (5) can be further reduced. it can.
[Example 1]
CF ₄ gas was introduced into the abatement apparatus at a concentration of 2000 ppm with an N ₂ gas carrier at 50 liters / min.
[0050]
The SiC heating element electric heater (5) is maintained at a surface temperature of 700 ° C, and external air is preheated to 300 ° C with LPG (10% propane, 90% butane) at 15.6 liters / min. 500 liter / min was mixed and introduced.
[0051]
LPG thermally decomposed and generated heat in the reaction tube (4a), and the space temperature gradually increased, reaching 1400 ° C. after 30 minutes. When the temperature was reached, the CF ₄ concentration in the exhaust gas was 30 ppm. In other words, it was possible to treat with a detoxification rate of 98.5% based on the concentration of introduced gas.
[Example 2]
In the same detoxification mechanism as in Example 1, C ₂ F ₆ gas was introduced at a concentration of 4000 ppm under N ₂ carrier at 100 liters / min.
[0052]
The SiC heater is maintained at a surface temperature of 700 ° C., and 13 A city gas (containing 88% methane) is 3.7 liters / min and external air 420 liters / min preheated to 250 ° C. in the reaction tower under the atmosphere. Mixed and introduced.
[0053]
The city gas thermally decomposed and generated heat in the reaction tower, and the space temperature gradually increased and reached 1200 ° C after 30 minutes. When the temperature was reached, the concentration of C ₂ F ₆ in the exhaust gas was measured and found to be 40 ppm. This results in a 99% abatement rate based on the introduced gas concentration. Further, CF ₄ was not present in the treated gas.
[Comparative Example 1]
LPG and external air are not introduced using only the electric heater maintained at 700 ° C., as in the example, but external air for oxidation is introduced into the reaction cylinder and discharged at 4 liters / min and 2000 ppm CF ₄ 50 liters / min. When the CF ₄ concentration in the gas was measured, it was found that it remained at 1900 ppm and was hardly detoxified.
[Comparative Example 2]
In Comparative Example 1, the temperature of the SiC heating element was raised and the surface temperature of the heater tube was heated to 1350 ° C. The CF ₄ gas and the oxidizing external air were subjected to the same conditions as in Comparative Example 1, and the CF ₄ concentration in the exhaust gas was measured. As a result, 550 ppm remained, and the detoxification rate was 72.5% based on the introduced gas concentration. It was. However, the temperature maintenance of the SiC heater became unstable, and continuous use for 3 days became impossible.
[0054]
【The invention's effect】
As described above, according to the present invention, in the detoxification method using an electric heater, since it becomes possible to achieve a sufficiently high temperature state with low energy cost, detoxification treatment can be carried out safely and stably, It is possible to reduce the exhaust gas below the TLV while suppressing the running cost by using the minimum energy.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an abatement apparatus according to the present embodiment.
[Explanation of symbols]
(F1) Semiconductor manufacturing exhaust gas
(F2) Flushing exhaust gas
(F3) Pyrolysis exhaust gas
(F4) Clean exhaust gas
(F5) Fuel gas
(1) Scrubber (entrance side)
(2) Fuel gas supply pipe
(3) Heat exchanger
(4) Thermal decomposition equipment
(4a) Reaction tube
(5) Electric heater
(6) Dust discharging device
(7) Scrubber (exit side)
(8) Exhaust fan
(9) Exhaust duct
(10) Circulating water pump
(11) Drainage duct
(12) Water tank
(14) Duct
(15) Communication pipe
(16) High pressure jet gas
(17) Dust
(20) Fuel supply unit
(21) External air preheater
(22) External air supply pump

Claims (4)

A semiconductor provided with a reaction cylinder provided with an electric heater, and a heat exchanger main body whose upper end opening is opened at a central portion of the installation location of the electric heater, and discharged from the upper end opening of the heat exchanger main body A detoxification method for high-temperature oxidative decomposition of production exhaust gas in the reaction cylinder,
A fuel gas supply pipe is inserted in the heat exchanger main body, and a fuel gas obtained by mixing preheated air and a hydrocarbon fuel containing H ₂ and CO is supplied to the fuel gas supply pipe. A method for removing exhaust gas from semiconductor manufacturing, characterized by: A scrubber for washing and removing water-soluble component gas and / or hydrolysis component gas in semiconductor manufacturing exhaust gas containing at least one of water-soluble component gas or hydrolysis component gas and thermal decomposition component gas, and a reaction cylinder provided with an electric heater And a heat exchanger main body whose upper end opening is opened at the central portion of the installation location of the electric heater, and water washing exhaust gas discharged from the upper end opening of the heat exchanger main body at high temperature oxidation decomposition An abatement method to
A fuel gas supply pipe is inserted in the heat exchanger main body, and a fuel gas obtained by mixing preheated air and a hydrocarbon fuel containing H ₂ and CO is supplied to the fuel gas supply pipe. A method for removing exhaust gas from semiconductor manufacturing, characterized by:   3. A method for removing exhaust gas from semiconductor manufacturing according to claim 1, wherein the electric heater in the reaction cylinder is used for igniting fuel gas, and energization of the electric heater is stopped after the fuel gas is ignited. A scrubber for washing and removing the water-soluble component gas and / or the hydrolyzed component gas in the semiconductor production exhaust gas containing at least one of the water-soluble component gas and the hydrolyzed component gas and the pyrolyzed component gas;
A reaction cylinder equipped with an electric heater;
The upper end opening part is opened in the central part of the installation place of the electric heater, and the heat exchanger main body for discharging the washing waste gas into the reaction tube,
A fuel gas supply pipe that is inserted into the heat exchanger main body and supplies a fuel gas obtained by mixing preheated air and a hydrocarbon-based fuel containing H ₂ and CO to the heat exchanger main body. A semiconductor manufacturing exhaust gas abatement apparatus.

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