JP2003001063A - Method and device for treating nf3-containing exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for decomposing and removing NF3 , by which a large amount of NF3 is effectively decomposed and removed with a low running cost while suppressing the occurrence of harmful byproducts. SOLUTION: The method for treating an exhaust gas containing NF3 is characterized in that NF3 is decomposed into nitrogen and fluorides by bringing the exhaust gas into contact with aqueous ammonia in a state that they are heated. The device for treating an exhaust gas containing NF3 is constituted of a heating/oxidizing tank having a hollow inner part through which the exhaust gas can pass, an exhaust gas introducing port and an aqueous ammonia introducing port, and a heating member for heating the internal atmosphere of the heating/oxidizing tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating NF ₃ -containing exhaust gas, and more particularly, in the semiconductor industry, a step of dry cleaning the inner surface of a semiconductor manufacturing apparatus and etching various film formations such as oxide films. The present invention relates to a method and an apparatus for efficiently treating NF ₃ -containing exhaust gas discharged in a process or the like.

[0002]

2. Description of the Related Art In the semiconductor industry, various harmful gases are used in the semiconductor manufacturing process, and there is concern about environmental pollution. In particular, the amount of NF ₃ used has recently increased as an etching gas and a cleaning gas. N
Not only is F ₃ harmful to the human body (allowable concentration is 10 ppm), but there is also an urgent need to establish a system for removing it as a greenhouse gas. As a method of processing NF ₃ ,
At present, a method of reacting NF ₃ with water for thermal oxidative decomposition and a method of reacting NF ₃ with water and ammonia gas for thermal oxidative decomposition have been proposed. However, in both methods, although NF ₃ is decomposed, a large amount of NO _x and N ₂ O are generated as by-products in addition to hydrogen fluoride,
Because these by-products are inexpensive and do not have a reliable treatment method,
These are permissible concentrations (NO: 25ppm, N
There is a problem that it is emitted in excess of O ₂ : 3 ppm, N ₂ O: 50 ppm).

[0003]

Therefore, the present invention solves the above-mentioned problems of the prior art, suppresses the generation of harmful by-products at a low running cost, and efficiently produces a large amount of NF ₃ It is an object of the present invention to provide a processing method and a processing device for decomposing and removing slag.

[0004]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive studies, and as a result, by reacting exhaust gas containing NF ₃ with ammonia water at a predetermined temperature or higher, NO The inventors have found that NF ₃ can be decomposed into nitrogen and fluoride without generating a large amount of by-products such as _x and N ₂ O, and have completed the present invention.

That is, the present invention is a method for treating exhaust gas containing NF ₃ , wherein the exhaust gas is brought into contact with aqueous ammonia in a heated state to decompose NF ₃ into nitrogen and fluoride. The present invention relates to a method for treating exhaust gas.

[0006]

The present invention will be described in more detail below. The following description shows specific examples of preferred embodiments of the present invention, and the present invention is not limited thereto.

When NF ₃ is decomposed using ammonia gas and water according to the conventional method, the reaction of the following equation
In addition to N ₂ and HF, a large amount of nitrogen oxides such as NO and NO ₂ are generated as by-products.

[0008]

[Formula 1]

In the present invention, ammonia water and NF ₃
It was found that NF ₃ can be decomposed into N ₂ and HF without causing the formation of by-products as described above by reacting with.

In the method for treating exhaust gas containing NF _{3 according} to the present invention, the exhaust gas containing NF ₃ is passed through a heating oxidation tank capable of heating above a predetermined temperature, and ammonia water is introduced therein. At this time, by the following reaction in the gas phase,
NF ₃ decomposes into N ₂ and HF.

[0011]

[Formula 2]

In the method of the present invention, the fluoride (HF) produced by the reaction of the formula (2) can be easily removed by subsequent treatment with a known treatment device such as a scrubber.

In the present invention, the temperature of the gas phase portion in which the reaction between NF ₃ and ammonia water is carried out is preferably 350 to 650 ° C, more preferably 450 to 650 ° C, and 550 to 550 ° C.
Most preferred is 600 ° C. The introduction amount of ammonia water to the heating oxidation vessel may be any processed by the NF ₃ with an equimolar or more as NH ₃ amount. In addition, as the ammonia water to be used,
Commercially available commercial products having an NH ₃ content of 10 to 40 wt%, preferably 20 to 30 wt%, particularly preferably about 25 wt%, can be suitably used.

The present invention also provides an apparatus for carrying out the exhaust gas treatment method described above. That is, another aspect of the present invention is an apparatus for treating exhaust gas containing NF ₃ , which has a hollow interior that allows the exhaust gas to pass through,
The present invention relates to an apparatus comprising a heating oxidation tank equipped with an exhaust gas introduction port and an ammonia water introduction port, and a heating member for heating an internal atmosphere of the heating oxidation tank.

A specific example of the exhaust gas treating apparatus according to the present invention is shown in FIG. The apparatus according to the present invention shown in FIG. 1 has, as main components, an ammonia water tank 1 and a heating oxidation tank 6 for contacting NF ₃ -containing exhaust gas with ammonia water at a predetermined temperature. Further, as shown in FIG. 1, a scrubber 8 for removing the fluoride generated by the reaction between NF ₃ and ammonia water can be arranged as a subsequent stage of the heating oxidation tank 6. The exhaust gas containing NF ₃ is supplied to the heating oxidation tank 6 through the supply pipe 10. Ammonia water is preferably supplied to the heating oxidation tank 6 in a vaporized state in order not to lower the atmospheric temperature in the heating oxidation tank 6. In the embodiment shown in FIG. Is supplied to the vaporizer 4. Ammonia water is vaporized in the vaporizer 4, and the vaporized ammonia water is supplied to the pipe 5 by the nitrogen gas supplied through the nitrogen supply pipe 3.
Is sent under pressure to the heating oxidation tank 6. It is preferable that a heating means such as a band heater is arranged in the vaporized ammonia water supply pipe 5 to preheat the vaporized ammonia water to further suppress a decrease in the atmospheric temperature in the heating oxidation tank 6. Of course, the ammonia water may be supplied to the heating oxidation tank 6 in a liquid state, but in this case as well, it is preferable to dispose a heating means such as a band heater in the ammonia water supply pipe 5 to preheat the ammonia water. . Also,
The NF ₃ -containing exhaust gas and the ammonia water may be premixed before being introduced into the heating oxidation tank 6, and in that case, a premixing tank is formed in the preceding stage of the heating oxidation tank 6, and NF ₃ is added here. It is sufficient to supply the contained exhaust gas and the ammonia water. A heating means 9 such as a ceramic heater such as a ceramic electric tubular furnace is arranged in the heating oxidation tank 6, and the gas temperature inside the hollow inside the heating oxidation tank 6 is heated to the above-mentioned suitable reaction temperature. . In addition, a bypass plate 7 is preferably arranged inside the heating oxidation tank 6 in order to enhance the contact efficiency of the reactants. In the heated heating oxidation tank 6, NF ₃ reacts with aqueous ammonia to generate a fluoride (H
F) and nitrogen (N ₂ ) are decomposed.

Next, the exhaust gas is sent to the scrubber 8 in the subsequent stage through the pipe 11 to remove the fluoride (HF) produced by the NF ₃ decomposition reaction in the heating oxidation tank 6. As the scrubber 8, any device having a capability of treating fluoride may be used, and in addition to a water scrubber device such as a packed tower or a spray tower, a dry adsorption cylinder type of packed synthetic zeolite may be used. The exhaust gas from which the fluoride has been removed by the scrubber 8 is discharged from the exhaust pipe 12.

2 to 6, the ammonia water and the NF ₃ -containing exhaust gas to be treated are mixed more efficiently in the heating oxidation tank, and / or the exhaust gas / heating gas in the heating oxidation tank is mixed.
The various structural examples for raising the heating efficiency of an ammonia water mixture are shown.

In the structure shown in FIG. 2, the heating oxidation tank 6 is used.
The tip of the supply pipe 5 for supplying ammonia water into the inside has the shape of the shower nozzle 20. As a result, the ammonia water can be introduced into the heating oxidation tank 6 in a mist state, and the mixing efficiency with the exhaust gas is further improved. In addition, in each of the embodiments shown in FIGS. 2 to 6, the ammonia water may be introduced in a liquid state or in a gaseous state (in a vaporized state), but the ambient temperature in the heating oxidation tank is not lowered. It is preferable to introduce it in a vaporized state.

The configuration shown in FIG. 3 has an ammonia water and NF ₃
The mixture with the contained exhaust gas forms a swirling flow in the heating oxidation tank 6. The NF ₃ -containing exhaust gas supply pipe 30 is branched into a plurality of pipes, each branch pipe having a spiral shape, and is connected to the heating oxidation tank 6 (FIG. 3 a). 3b is a cross-sectional view 3 taken along the line AA ′ of FIG. 3a. An exhaust gas supply pipe that is branched into three is connected to the upper surface of the heating oxidation tank 6 to form an exhaust gas inlet 31. On the other hand, the ammonia water is the ammonia water supply pipe 35.
Is supplied to the annular water introducing member 36 (FIG. 3c). The ammonia water supply pipe 35 is obliquely connected to an annular ammonia water introducing member 36, and the ammonia water supplied to the introducing member 36 swirls in the annular ring. A plurality of ammonia water nozzles 37 are opened on the inner surface of the ring, and the ammonia water is ejected from the nozzles 37 into the heating oxidation tank 6. The nozzle 3
A guide member (for example, a tubular guide) directed in the tangential direction of the ring may be arranged in 7 so that the ammonia water is ejected in the tangential direction, or it may be directed toward the center of the oxidation heating tank 6. May be ejected. Since the ammonia water forms a swirl flow in the annular ammonia water introducing member 36, even after being ejected from the nozzle 37, the ammonia water forms a swirl flow and flows downward in the heating oxidation tank 6. on the other hand,
The NF ₃ -containing exhaust gas also forms a swirl flow when flowing in the spiral exhaust gas supply pipe, and is ejected from the exhaust gas inlet 31 while forming a swirl flow. As a result, the NF ₃ -containing exhaust gas and the ammonia water descend in the heating oxidation tank 6 while forming a mixed swirling flow (FIG. 3d). As a result, the NF ₃ -containing exhaust gas and the ammonia water are extremely efficiently mixed and brought into contact with each other in the heating oxidation tank 6.

FIG. 4 shows an example in which a guide plate is provided in the oxidation heating tank 6. The guide plate is formed so that the mixture of the exhaust gas and the ammonia water stays in the oxidation heating tank for a long time,
In the embodiment shown in FIG. 4, the hollow portion 5 is provided at the center of the heating oxidation tank 6.
2 is formed, and a guide plate 50 is formed around the same so as to draw a spiral from the exhaust gas introduction port and the ammonia water introduction port toward the discharge port. Furthermore, the temperature inside the oxidation heating tank 6 can be monitored by disposing the temperature detecting means 51 known in the art, such as a thermocouple, inside the hollow tube 52. In the configuration shown in FIG. 4, NF ₃
The exhaust gas contained and the ammonia water are respectively supplied to the supply pipe 10
And 5 are introduced into the heating oxidation tank 6, and the mixture of gas and ammonia water flows in the heating oxidation tank 6 spirally along the guide plate 50. Therefore, the time during which the mixture of the NF ₃ -containing exhaust gas and the ammonia water stays in the heating oxidation tank 6 can be increased, and the reaction can proceed more efficiently, as well as the heating by the heating medium 9. Can be performed more efficiently.

FIG. 5 shows an example in which a plurality of disk-shaped members 60 are arranged in the thermal oxidation tank 6. Openings 61 are formed in each disk-shaped member 60, and the openings of the respective disk-shaped members are arranged so as to be staggered. The NF ₃ -containing exhaust gas and the ammonia water are introduced into the heating oxidation tank 6 through the supply pipes 10 and 5, respectively, and flow toward the opening 61 along the surface of the first disk-shaped member 60, and then to the second Flows along the surface of the disk-shaped member 60 'toward the opening 61' provided on the opposite side. By adopting such a configuration, the time during which the mixture of the NF ₃ -containing exhaust gas and the ammonia water stays in the heating oxidation tank 6 can be increased, and the reaction can proceed more efficiently. In addition, heating by the heating medium 9 can be performed more efficiently.

FIG. 6 shows an example in which the heating oxidation tank 6 is formed in a crank shape along the heating medium 9. The NF ₃ -containing exhaust gas and the ammonia water are introduced into the heating oxidation tank 6 through the supply pipes 10 and 5, respectively, and flow toward the discharge pipe 11 while passing through the flow path 70. As a result, the flow path of the mixture of the NF ₃ -containing exhaust gas and the ammonia water can be made long, so that the time for which this mixture stays in the heating oxidation tank 6 can be increased and the reaction proceeds more efficiently. In addition to this, it is possible to increase the contact area between the flow path 70 and the heating medium 9, so that heating can be performed more efficiently.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 An SUS hollow column having an inner diameter of 110 mm and a length of 400 mm with a ceramic heater attached to the outside was used as a reaction vessel. 1.5 L / min of NF ₃ was added to this reaction vessel,
Ammonia water (25 wt%, specific gravity 0.898) 5 mL / min
(Equivalent to 1.5 L / min as NH ₃ ) and N ₂ were flown at a flow rate of 80 L / min.

The temperature of the gas phase portion of the reaction vessel was adjusted to 600 ° C., and the outlet gas at the time of passing gas was analyzed. The analysis was carried out by using a gas chromatograph mass spectrometer (Anerva, AGS-7000U) for NF ₃ and N ₂ O, and a chemiluminescence spectrometer (NOA-700, manufactured by Shimadzu Corporation) for NO and NO _2.
0), NH ₃ and HF were measured using a detector tube (manufactured by Gastec). Table 1 shows the results of the outlet gas analysis at the next point after 20 minutes have passed after the gas was discharged. NF ₃ , NO, N
O ₂ and N ₂ O were all below the allowable concentration and below the detection limit. Further, HF was discharged by decomposition of NF ₃ .

[0026]

[Table 1]

Comparative Example 1 Using the same reaction vessel as in Example 1, NF was introduced by introducing water.₃
The processing performance of was investigated. In the reaction vessel, NF₃0.82 L / m
in, water 5mL / min, N₂At a flow rate of 80 L / min. Anti
Adjust the temperature of the gas phase of the reaction vessel to 600 ° C, and
The outlet gas was analyzed. 20 minutes after degassing, at the next point
Table 2 shows the results of the outlet gas analysis of the above. NF ₃Is below the detection limit
Processed below, no, no₂, N₂O exceeds allowable concentration
Produced in large quantities.

[0028]

[Table 2]

Comparative Example 2 Using the same reaction vessel as in Example 1, the treatment performance of NF ₃ by introducing ammonia gas and water was examined. In the reaction vessel,
NF ₃ 1.5 L / min, ammonia gas 1.5 L / min,
Water was flown at 5 mL / min and N ₂ was flowed at 80 L / min. The temperature of the gas phase part of the reaction vessel was adjusted to 600 ° C., and the outlet gas at the time of passing gas was analyzed. Table 3 shows the results of the outlet gas analysis at the next point after 20 minutes have passed after the gas was discharged. Although NF ₃ was processed below the detection limit, NO, NO ₂ , and N ₂ O were produced in large amounts as by-products, exceeding the permissible concentration.

[0030]

[Table 3]

Example 2 A water washing tower (inner diameter 210 mm × height 430 mm, Raschig ring filling height 170) was added after the test column used in Example 1.
mm) connected. In the test column, as in Example 1, N
F ₃ at 1.5 L / min, ammonia water (25 wt%, specific gravity of 0.1.
898) at 5 mL / min (equivalent to 1.5 L / min as NH ₃ ),
N ₂ was flown at a flow rate of 80 L / min. The amount of water sprayed in the water washing tower was 3 L / min. In the same manner as in Example 1, the temperature of the gas phase part of the reaction vessel was adjusted to 600 ° C., and the gas at the outlet of the water washing tower during gas passage was analyzed. Table 4 shows the results of the outlet gas analysis at the next point 20 minutes after the gas was discharged. NF ₃ , NO, NO ₂ , N ₂ O
In addition, HF was below the allowable concentration and below the detection limit.

[0032]

[Table 4]

[0033]

According to the present invention, a large amount of NF ₃ can be efficiently removed at a low running cost by treating exhaust gas containing NF ₃ and suppressing the generation of harmful by-products. .

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of an exhaust gas treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structural example of a heating oxidation tank that can be used in the present invention.

FIG. 3 is a diagram showing another structural example of a heating oxidation tank that can be used in the present invention.

FIG. 4 is a diagram showing another structural example of a heating and oxidizing tank that can be used in the present invention.

FIG. 5 is a diagram showing another configuration example of a heating oxidation tank that can be used in the present invention.

FIG. 6 is a diagram showing another structural example of a heating and oxidizing tank that can be used in the present invention.

Claims (4)

[Claims] 1. A method for treating exhaust gas containing NF ₃ , comprising treating the exhaust gas with ammonia water in a heated state to decompose NF ₃ into nitrogen and fluoride. Method. 2. The method according to claim 1, further comprising a step of removing a fluoride produced by the reaction of NF ₃ and aqueous ammonia with a scrubber. _3. An apparatus for treating exhaust gas containing NF ₃ , which has a hollow interior for allowing the exhaust gas to pass therethrough, and a heating oxidation tank having an exhaust gas inlet and an ammonia water inlet, and a heating oxidation tank. A device comprising a heating member for heating the internal atmosphere of the device. 4. The apparatus according to claim 3, further comprising a scrubber after the heating oxidation tank.