TWI669151B - Method and device for decompressing and harming exhaust gas - Google Patents

Abstract

The present invention is to provide a method and a device for eliminating exhaust gas, which can minimize the use of nitrogen for dilution and have excellent energy utilization efficiency. That is, the decompression and detoxification method of exhaust gas and the device thereof according to the present invention are characterized in that the exhaust gas supplied from a generation source through a vacuum pump is maintained in a decompressed state and is decomposed by being heated by an electric heater and And / or reaction treatment.

Description

Method and device for decompressing and harming exhaust gas

The present invention relates to a method and a device for removing exhaust gas, which are suitable for the treatment of harmful gases such as flammable gases, toxic gases, and greenhouse gases emitted by manufacturing processes in the electronics industry.

In the electronics industry for manufacturing semiconductors and liquid crystals, various CVD procedures are used, such as silicon nitride film CVD, silicon oxide film CVD, TEOS oxide film CVD, high dielectric constant film CVD, low dielectric constant film CVD, and metal film CVD. . Among them, in order to form a silicon-based thin film, a CVD method using an explosive and toxic silane-based gas is mainly used. The process gas containing the above-mentioned silane-based gas used in the CVD method is exhausted after being used in the CVD process, and is harmless by a detoxification device as described in Patent Document 1 below. In front of this detoxification device, a large amount of nitrogen for dilution is injected in order to dilute the silane-based gas in the exhaust gas below the explosive electrode boundary. Here, in a typical silicon nitride film CVD, SiH ₄ / NH ₃ / N ₂ O = 1slm / 10slm / 10slm (slm: standard liter per minute) is used, and the flow rate per minute at 1 atm and 0 ° C is used. Units expressed in liters), since the explosion range of SiH ₄ is 1.3% to 100%, such a gas exhausted from the CVD process must be immediately diluted to about 76 times by dilution with nitrogen. As long as the dilution is performed, the detoxification treatment can be performed safely and reliably using a thermal decomposition device using a conventional combustion method or an atmospheric piezoelectric slurry method.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-333247

Problems to be solved by the invention

However, the conventional technique described above has the following problems. That is, as described above, in order to heat the entire exhaust gas containing the silane-based gas diluted with nitrogen to the decomposition temperature, it must be about 76 times of the case where only the exhaust gas containing the silane-based gas before dilution is heated. Times the energy. That is, in the past, the detoxification program that had to be diluted with nitrogen gas not only increased the cost with the use of a large amount of nitrogen, but also had to be heated with nitrogen that was not directly related to the exhaustion of the exhaust gas. Therefore, the energy efficiency was low and it also caused The cost of electricity or fuel increases.

In view of this, the main purpose of the present invention is to provide an exhaust gas detoxification method and a device thereof, which can minimize the use of nitrogen for dilution without compromising safety, and have excellent energy utilization efficiency. Technical means to solve problems

In order to achieve the above-mentioned object, the countermeasure adopted in the present invention is to reduce the exhaust gas under reduced pressure. That is, the first invention of the present invention is a method for decompressing and harming exhaust gas, which is characterized in that the exhaust gas E supplied from the exhaust gas generating source 12 through the vacuum pump 14 is maintained in a reduced pressure state by The electric heater 17 is heated to perform decomposition and / or reaction treatment.

The first invention has the following effects, for example. The exhaust gas E supplied from the exhaust gas generating source 12 through the vacuum pump 14 is maintained in a decompressed state and heated by an electric heater 17 to perform decomposition and reaction treatment. Therefore, the heat generated by the reaction becomes thinner, and no sharp Temperature rises, explosive reactions, nitrogen dilution is no longer necessary or very small. In addition, since the dilution with nitrogen gas is unnecessary or sufficient in this way, almost all of the heat energy supplied from the electric heater 17 can be directly used for the decomposition and reaction of the exhaust gas E. In addition, since the generation source of the exhaust gas E to the processing section are under reduced pressure, even if the exhaust gas E contains a gas that is toxic to the human body, it will not be heated and decomposed by the electric heater 17 and And / or the doubt that the exhaust gas E is leaked out of the system before the treatment.

Here, in the first invention, it is preferable that the decompressed state is in a range of 1 Torr or more and 700 Torr or less, more preferably in a range of 15 Torr or more and 685 Torr or less, and particularly preferably in a range of 100 ± 50 Torr. . When the decompression state is less than 1 Torr, a high-priced and large-scale device must be used in order to achieve a high vacuum environment. On the contrary, when the decompression state is more than 700 Torr, because the difference from atmospheric pressure becomes smaller, the exhaust must be exhausted. E was diluted with a large amount of nitrogen.

The second invention of the present invention is a device for implementing the above-mentioned decompression and detoxification method of exhaust gas. For example, as shown in FIGS. 1 and 2, the decompression and detoxification device 10 for exhaust gas is configured as follows. The decompression and detoxification device 10 for exhaust gas has a reaction cylinder 16 which receives the exhaust gas E supplied from the exhaust gas generation source 12 through the vacuum pump 14 in an exhaust gas treatment space 26 formed in the reaction cylinder 16. It is heated by the electric heater 17 to perform decomposition and / or reaction treatment. A rear-stage vacuum pump 18 is connected to the exhaust outlet 40 side of the reaction cylinder 16. The rear-stage vacuum pump 18 is configured to reduce the pressure from the discharge port of the vacuum pump 14 to the inside of the reaction cylinder 16.

In the second invention, it is preferable to provide a decomposition and reaction aid supply means 20, which is supplied to the inside of the reaction cylinder 16 and is selected from the group consisting of moisture, air, and At least one of the group consisting of O ₂ , H ₂ and a hydrocarbon gas. In this case, even if the exhaust gas E contains a large amount of flammable substances or harmful substances, such as SiH ₄ and NF ₃ , by adding the above-mentioned decomposition and reaction aids, these substances can be easily decomposed. A stable state or a reaction is performed to render it harmless.

Further, in the second invention, it is preferable that the reaction tube 16 has a double-tube structure having an outer tube 21 and an inner tube 23, and a preheating zone 25 is formed between the outer tube 21 and the inner tube 23. The preheating zone 25 is a process for allowing the exhaust gas E before the treatment which is introduced into the reaction cylinder 16 and supplied to the exhaust treatment space 26 and the exhaust treatment space 26 which is decomposed and reacted by heating. The exhaust gas E is exchanged with heat. In this case, the exhaust gas E supplied to the exhaust treatment space 26 can be preheated inside the reaction cylinder 16 under a reduced-pressure environment which can also be referred to as a quasi-vacuum, and can be generated by the electric heater 17 The thermal energy is used for the decomposition and reaction treatment of exhaust gas E without waste.

Moreover, in the said 2nd invention, it is preferable that the said back stage vacuum pump 18 is a water seal pump. The rear-stage vacuum pump 18 is used to suck in and discharge the exhaust gas that has been detoxified in the reaction cylinder 16 in addition to reducing the pressure from the discharge port of the vacuum pump 14 to the inside of the reaction cylinder 16. Here, the water-sealed pump (water-sealed vacuum pump) refers to a pump having a structure in which an appropriate amount of water-sealing liquid is added to the casing to rotate the impeller, and the water-sealing liquid and the impeller are pressed against the inner wall of the casing by centrifugal force A vacuum pump that performs suction and discharge by changing the enclosed space. Therefore, the exhaust gas E that has been subjected to the detoxification treatment in the reaction cylinder 16 comes into contact with the water-sealing liquid when passing through the inside of the water-sealing pump. In this way, the water-soluble components in the exhaust gas E accompanied by the detoxification treatment are dissolved in the water-sealing liquid and removed from the exhaust gas E. Therefore, an exhaust water washing device such as a wet scrubber can be omitted. Invention effect

According to the present invention, it is possible to provide a method and a device for eliminating exhaust gas, which can minimize the use of nitrogen for dilution without detracting from safety, and has excellent energy utilization efficiency.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing an exhaust gas pressure reduction and detoxification device 10 according to an embodiment of the present invention. As shown in FIG. 1, the decompression and detoxification device 10 for exhaust gas according to the present embodiment is a device for detoxifying exhaust gas E supplied from a discharge source 12 such as a CVD device through a vacuum pump 14 and has The reaction cylinder 16 and the rear vacuum pump 18. Here, in the embodiment of FIG. 1, the exhaust gas generation source 12 is an example showing a silicon nitride film CVD apparatus. In a typical silicon nitride film CVD device, SiH ₄ / NH ₃ / N ₂ O = 1slm / 10slm / 10slm is used as a program gas, and NF ₃ / Ar = 15slm / 10slm is used as a cleaning gas. It can be considered that SiF ₄ which is a product of the washing reaction is discharged about 10 slm. After use, these gases are supplied to the decompression and detoxification device 10 through the vacuum pump 14 in the form of exhaust gas E. In the manufacturing process of a semiconductor element such as a silicon nitride film CVD, a dry pump is mainly used as the vacuum pump 14. Therefore, N ₂ (nitrogen) supplied to the vacuum pump 14 is to purge N ₂ supplied to the shaft seal of the pump 14.

The reaction tube 16 is composed of a double tube (refer to FIG. 2) having an outer tube 21 and an inner tube 23. The outer tube 21 is formed of a metal material having excellent corrosion resistance such as HASTELLOY (registered trademark). It has a cylindrical shape with its shaft facing up and down. The inner tube 23 is also formed of a metal material with excellent corrosion resistance such as HASTELLOY (registered trademark), and is arranged in the outer tube 21. It is formed in a concentric shape with the outer tube 21. Here, an exhaust inlet 38 is provided at the lower end portion of the outer peripheral wall of the outer pipe 21 and communicates with a discharge port (delivery port) of the vacuum pump 14 through a pipe 36. In addition, in the space enclosed by the outer tube 21 and the inner tube 23, the lower end portion is closed, and the upper end portion separates the inner tube 23 from the top plate 16a of the reaction tube 16, thereby forming a space with the inner tube 23 The exhaust processing space 26 communicates. Therefore, the exhaust gas E introduced into the space enclosed by the outer tube 21 and the inner tube 23 from the exhaust inlet 38 will be at a high temperature after the space is heated up and decomposed in the exhaust treatment space 26 while the space rises. The processed exhaust gas E is preheated by heat exchange. That is, the space enclosed by the outer tube 21 and the inner tube 23 becomes the preheating zone 25.

The reaction cylinder 16 is erected on the stand 27, and the lower end portion of the inner tube 23 extends downward. The front end of the reaction cylinder 16 is provided with an exhaust outlet 40 directly connected to the suction (suction) of the vacuum pump 18 at the rear section. . Reference numeral 29a in FIG. 2 indicates a measurement port, which is a meter for installing a vacuum gauge (not shown) for measuring the degree of vacuum inside the reaction cylinder 16; and 29b, an air supply nozzle, which faces the reaction cylinder as necessary Internally, reaction air and dilution air are added. In addition, a nozzle 42 (see FIG. 2A) is installed near a portion that communicates the preheating zone 25 and the exhaust treatment space 26 on the upper portion of the reaction cylinder 16 with the decomposition and reaction auxiliary agent supply means 20 as necessary. Decomposition and reaction aids such as water and the like are introduced into the exhaust treatment space 26. In addition, a heater insertion hole 16 b is formed in the center of the top plate 16 a of the reaction cylinder 16, and an electric heating heater 17 in the reaction cylinder 16 is provided through the heater insertion hole 16 b.

The electric heater 17 is used to heat the exhaust treatment space 26 to a predetermined temperature above the thermal decomposition temperature of the exhaust gas E (especially the components to be harmed) (specifically, about 600 ° C to 1300 ° C). The exhaust gas E is thermally decomposed, and includes a heating element 17a and a protective tube 17b. The heating element 17a generates electricity at a temperature equal to or higher than the thermal decomposition temperature of the exhaust gas E by electricity. The heating element 17a becomes a heating source of the electric heating heater 17, and examples thereof include solid or hollow rods made of silicon carbide. A metal wire such as a nickel-chromium alloy wire, a Kanthal wire, etc., which is folded in half at the center C in the longitudinal direction so that the metal wires are substantially parallel to each other, and is further wound in a spiral shape. The outer periphery of the heating element 17a is protected by a protection tube 17b. The protective tube 17b is made of ceramics such as alumina (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and silicon nitride (Si ₃ N ₄ ), or has excellent corrosion resistance. A bottomed cylindrical container body made of a metal material or the like, which houses the heating element 17a and protects the heating element.

The rear-stage vacuum pump 18 is used to reduce the pressure from the discharge port of the vacuum pump 14 to the inside of the reaction cylinder 16 to a predetermined vacuum degree, and to suck and exhaust the exhaust gas E after the decontamination treatment of the reaction cylinder 16. In this embodiment, a water-sealed pump is used as the rear-stage vacuum pump 18. Therefore, a gas-liquid separation coalescer (coalescer) for separating the treated exhaust gas E discharged from the rear-stage vacuum pump 18 in a mixed state and a water-seal liquid is installed on the discharge port side of the rear-stage vacuum pump 18 The separator 62 (refer to FIG. 1).

Here, the depressurized state from the exhaust port of the vacuum pump 14 to the exhaust gas flow area inside the reaction cylinder 16 caused by the rear-stage vacuum pump 18 is preferably in a range of 1 Torr or more and 700 Torr or less, more preferably 15 Torr or more and In the range below 685 Torr, it is particularly preferably in the range of 100 ± 50 Torr. When the decompression state is less than 1 Torr, a high-priced and large-scale device must be used in order to achieve a high vacuum environment. On the contrary, when the decompression state is more than 700 Torr, because the difference from atmospheric pressure becomes smaller, the exhaust must be exhausted. E was diluted with the same amount of nitrogen as at atmospheric pressure.

Although not shown in the exhaust gas decompression and detoxification device 10 of this embodiment, it is of course provided with various detection equipment, control equipment, power supply, and the like necessary for operating the electric heater 17, the vacuum pump 18 at the rear, and the like. .

Next, the decompression and detoxification method of the exhaust gas E using the exhaust decompression and detoxification device 10 configured as described above will be described. The exhaust gas E discharged from the exhaust generation source 12 is passed through the vacuum pump 14 to the reaction cylinder 16. supply. Here, by operating the vacuum pump 18 at the rear stage, the exhaust gas E is maintained at a predetermined reduced pressure state, and the exhaust gas E is introduced into the exhaust gas treatment space 26 from the preheating zone 25 in the reaction cylinder 16. The heat generated by the electric heating heater 17 is decomposed and reacted.

According to the decompression and detoxification method of the exhaust gas of this embodiment, the exhaust gas E is maintained in a reduced pressure state, and the heat generated by the decomposition and reaction of the electric heating heater 17 is thinned, so that a rapid temperature rise and an explosion reaction do not occur. It is possible to carry out the detoxification treatment, so nitrogen for dilution becomes unnecessary or a very small amount is sufficient. In addition, since such dilution with nitrogen is unnecessary or sufficient, almost all of the heat energy supplied from the electric heater 17 can be directly used for the decomposition and reaction of the exhaust gas E. Therefore, these two functions complement each other, and it is possible to make the exhaust device for exhaust E into a very compact structure. Furthermore, since the source of the exhaust gas E to the processing unit are under reduced pressure, even if the exhaust gas E contains a gas that is toxic to the human body, it will not be thermally decomposed by the electric heater 17 Concerns about the leakage of the exhaust gas E to the outside of the system before the reaction.

The above embodiment can be modified as follows. Although the reaction tube 16 is a double-layer tube structure having an outer tube 21 and an inner tube 23 and a preheating zone 25, the reaction tube 16 may be used when the exhaust gas E is not required to be preheated. The structure is a single tube (single-layer tube) structure in which the preheating zone 25 is omitted.

Although the decomposition and reaction aid supplied from the aforementioned decomposition and reaction aid supply means 20 includes water, for example, when exhaust gas E contains a large amount of PFCs (perfluoro compounds) such as NF ₃ , it is generated as decomposition and reaction When a large amount of HF is generated, it is preferable to add an alkaline aqueous solution such as a KOH aqueous solution or a NaOH aqueous solution as a neutralizing agent (decomposition and reaction aid). In addition, the case where the oxidation treatment is performed includes a case where air or oxygen is added, or a case where a reducing gas such as H ₂ or CH ₄ is added.

Although the case where a water-sealed pump is used as the rear-stage vacuum pump 18 is shown, when the decomposed product after the exhaust gas E detoxification treatment does not need to be washed, a dry-type pump may be used instead of the water-sealed pump.

Although the case where the exhaust pump 38 of the vacuum pump 14 and the reaction cylinder 16 are connected by a pipe 36 is shown, the exhaust port of the vacuum pump 14 and the exhaust inlet 38 may be directly connected. In addition, although the case where the exhaust outlet 40 of the reaction cylinder 16 and the suction port of the rear vacuum pump 18 are directly connected is shown, the exhaust outlet 40 of the reaction cylinder 16 and the rear vacuum pump 18 may be connected through a pipe.

10‧‧‧Vacuum decompression device

12‧‧‧ exhaust gas generation source

14‧‧‧Vacuum pump

16‧‧‧Reactor

17‧‧‧ Electric heater

18‧‧‧ rear vacuum pump

20‧‧‧ Decomposition and reaction aid supply means

21‧‧‧ Outer tube

23‧‧‧Inner tube

25‧‧‧ warm-up zone

26‧‧‧Exhaust treatment space

E‧‧‧Exhaust

FIG. 1 is a schematic diagram showing a decompression and detoxification device for exhaust gas according to an embodiment of the present invention. FIG. 2A is a partial front sectional view showing an example of a reaction cylinder of the decompression and detoxification device for exhaust gas of the present invention, and FIG. 2B is a sectional view taken along the line A-A of FIG. 2A.

Claims (7)

A decompression and detoxification method for exhaust gas, characterized in that the exhaust gas supplied from an exhaust gas generation source through a vacuum pump is maintained in a reduced pressure state and is decomposed by being heated by an electric heater. The decompression and detoxification method of exhaust gas according to claim 1, wherein the decompression state is in a range of 1 Torr or more and 700 Torr or less. A decompression and detoxification device for exhaust gas, characterized in that it includes a reaction cylinder (16) and a rear vacuum pump (18). The reaction cylinder (16) passes through the vacuum pump (14) and is generated from an exhaust gas source (12). The exhaust gas (E) supplied is decomposed in an exhaust treatment space (26) formed in the interior by heating by an electric heater (17). The aforementioned vacuum pump (18) is connected to the reaction cylinder ( 16), the pressure is reduced from the exhaust port of the vacuum pump (14) to the inside of the reaction cylinder (16). The decompression and detoxification device for exhaust gas according to claim 3, wherein a decomposition and reaction aid supply means (20) and a decomposition and reaction aid supply means (20) are provided inside the reaction cylinder (16). It is at least one selected from the group consisting of moisture, air, O ₂ , H ₂ and hydrocarbon gas as a decomposition and reaction aid supplied to the inside of the reaction cylinder (16). The exhaust pressure reduction and harm reduction device according to claim 3 or 4, wherein the reaction tube (16) has a double-layered tube structure including an outer tube (21) and an inner tube (23), and the outer tube (16) A preheating zone (25) is formed between the 21) and the inner pipe (23). The preheating zone (25) is introduced into the reaction cylinder (16) and supplied to the exhaust treatment space (26). Heat exchange is performed between the exhaust gas (E) before the treatment and the processed exhaust gas (E) after the exhaust treatment space (26) is decomposed by heating. The exhaust pressure reducing and harm removing device according to claim 3 or 4, wherein the aforementioned vacuum pump (18) at the rear stage is a water-sealed pump. The decompression and detoxification device for exhaust gas according to claim 5, wherein the vacuum pump (18) at the rear stage is a water-sealed pump.