JP3308365B2 - How to remove nitrogen trifluoride gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing and removing nitrogen trifluoride gas contained in dry etching exhaust gas and the like.

[0002]

[Prior art] nitrogen trifluoride gas (hereinafter referred to as NF ₃₎
Is attracting attention as a dry etching agent or a fluorinating agent for LSI. In particular, as a dry etching agent,
Contamination of LSI substrate occurring during perfluorocarbon-based etching compared with the etching agent such as CF ₄ has advantages such as extremely small. On the other hand, NF ₃ is extremely stable in the air and is a nonflammable gas that does not react with water, acid, or an aqueous alkali solution, but is a toxic gas having a TLV of 10 ppm. For this reason, the NF ₃ -containing gas after use cannot be released to the atmosphere as it is, and is currently diluted to 10 ppm or less in air or discharged after some decomposition treatment. is there.

However, the N discharged after air dilution
F ₃ is because they are not degraded in the atmosphere, it is feared adverse effect on the combined natural environment, and particularly in biological systems and the future of NF ₃ usage increase expected. Therefore, conventionally, as abatement method NF _3, it was mixed with hydrogen gas comprising NF _3, by contacting the mixed gas to a reducing catalyst, or so as to decompose the hydrogen reduction reaction (JP-A-2-303524 Japanese Patent Application Laid-Open No. 62-273039 discloses a method in which a gas containing NF ₃ is brought into contact with a substance mainly containing at least one of a reducing catalyst, alumina and silica. Have been.

[0004]

In However conventional abatement methods [0006] Since the intended former you have to disassemble the NF ₃ in a high temperature atmosphere of 130 to 180 ° C., by way of the latter 200 ° C. before and after There is a practical problem that a large-scale external heater is required, the entire apparatus becomes large, handling is inconvenient, and cost is high. Also, (Japanese Unexamined Patent Application Publication No.
Japanese Patent Application Laid-Open No. 261247/1995) is a method of removing harm at room temperature. However, the method according to this method has problems that not only the NF ₃ processing capacity (the processing amount per unit volume of the catalyst) is low, but also if the gas flow rate is high, sufficient detoxification cannot be performed.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have improved the drawbacks of the prior art, and have conducted intensive studies on methods that can be implemented industrially. The inventors have found that the object has been achieved, and have completed the present invention. That is, the present invention is characterized in that carbon monoxide is acted on a reducing metal catalyst to activate the same, and the activated reducing metal catalyst is brought into contact with a gas containing nitrogen trifluoride at room temperature. The present invention relates to a method for removing nitrogen gas.

Hereinafter, the present invention will be described in more detail. The reducing metal catalyst used in the present invention contains a metal, a metal oxide, or a metal hydroxide as an effective substance, and examples of the metal element include Cu, Fe, Zn, Cr, and Mn.

In the activation treatment of the reducing metal catalyst, 100% carbon monoxide is used for the reducing metal catalyst in the form of a tablet filled in an atmosphere furnace or a column, or carbon monoxide diluted with an inert gas is used. 300-1000 ° C
It is preferable to carry out at a temperature of preferably 400 to 600 ° C. and lower than the melting point of the contained metal. If the temperature is out of the above range, for example, less than 300 ° C., sufficient activity cannot be obtained.
NF ₃ is detected several minutes after aeration of F _3, which is not preferable. On the other hand, when the temperature exceeds 1000 ° C., although the activity is obtained, the NF ₃ treatment capacity is reduced, which is not preferable in terms of energy consumption and durability of the apparatus.

As described above, the present invention activates a reducing metal catalyst by causing carbon monoxide to act on the reducing metal catalyst at a temperature in the range of 300 to 1000 ° C., and the activated reducing metal catalyst contains NF _3. By bringing the gas into contact at room temperature,
Since NF ₃ is decomposed, there is no need to heat the reaction tower with an external heater, so that the entire apparatus can be reduced in size and handling is simplified. Thereby, the abatement cost can be reduced. In addition, it has a longer life than conventional products and can cope with a wide range of gas velocities.

[0009]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. Example 1 An apparatus equipped with a stainless steel column having a length of 500 mm and an inner diameter of 16.5 mmφ, a gas inlet tube, an exhaust gas tube on both sides, a joint for connecting the column, and a heater for heating the column was used. 4mmφ × 4m
The treatment agent formed in a tablet shape of mH
mm (25 ml, 17.5 g). The treatment agent used was an iron-based catalyst mainly composed of Fe ₂ O ₃ used as a reduction catalyst. This iron-based catalyst is obtained by solidifying metallic iron and iron oxide with diatomaceous earth.
Contains 0%. After filling the treatment agent, the mixture was heated to 500 ° C., and 300 cc / m of carbon monoxide was introduced from the gas inlet tube.
in for 6 hours, 100% of iron oxide in treatment agent
After treatment with carbon monoxide to activate the treating agent, nitrogen was flowed to cool the treating agent to room temperature. The treated packed column was moved to a scrubber equipped with a gas introduction pipe and an exhaust gas pipe, and the NF ₃ concentration diluted with N ₂ at room temperature was 1%.
1500 cc / min (superficial linear velocity 1)
Aeration was performed at a flow rate of 1.68 cm / sec). At this time, as a result of analyzing NF ₃ in the gas discharged from the exhaust gas port by gas chromatography, NF ₃ was not detected until 36 minutes after the ventilation. Table 1 shows the results.

Example 2 A packed column treated in the same manner as in Example 1 was transferred to an abatement apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and the NF ₃ concentration diluted with N ₂ at room temperature was 0.1%. Gas with
700 cc / min (superficial linear velocity 21.03 cm / se
Vent at the flow rate of c). At this time, as a result of analyzing NF ₃ in the gas discharged from the exhaust gas port by gas chromatography, NF ₃ was not detected until 150 minutes after the ventilation. Table 1 shows the results.

Example 3 A packed column treated in the same manner as in Example 1 was transferred to an abatement apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and the NF ₃ concentration diluted with N ₂ at room temperature was 0.1%. , O ₂ : 0.05
_%, NO 2: a gas having a 0.05% 500 cc / m
Vent at a flow rate of in (superficial linear velocity 3.89 cm / sec). At this time, as a result of analyzing NF ₃ in the gas coming out of the exhaust gas port by gas chromatography, up to 8 hours after aeration,
NF ₃ is, of course, NO ₂ was detected. Table 1 shows the results
Shown in

Example 4 50 g of an iron-based catalyst mainly composed of Fe ₂ O ₃ formed in a 4 mmφ × 4 mmH tablet shape was placed in a carbon monoxide atmosphere furnace, and the temperature was raised to 500 ° C. 1
The iron oxide in the treating agent is treated with carbon monoxide by circulating 00% carbon monoxide at 1000 cc / min for 6 hours to activate the treating agent, and then flowing nitrogen to cool the treating agent to room temperature. I let it. The activated treating agent obtained at this time is 40.
It was 5 g. This iron-based catalyst is obtained by solidifying metallic iron and iron oxide with diatomaceous earth, and contains 60% of metallic iron and iron oxide. The treatment agent cooled to room temperature was immediately transferred into the N ₂ BOX without contact with air, and the column was filled with 25 ml. Next, it moved to the abatement apparatus provided with the gas introduction pipe and the exhaust gas pipe, and at room temperature, the NF ₃ concentration diluted with N ₂ was 1
% Of gas at 1500 cc / min (superficial linear velocity 1
Aeration was performed at a flow rate of 1.68 cm / sec). At this time, as a result of analyzing NF ₃ in the gas discharged from the exhaust gas port by gas chromatography, NF ₃ was not detected until 30 minutes after the ventilation. Table 1 shows the results.

Example 5 A packed column treated in the same manner as in Example 1 except that the treatment temperature was set to 350 ° C. was transferred to a detoxification apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and N ₂ was added at room temperature. Gas with NF ₃ concentration of 1% diluted at 1500 cc / min
(Vent at a linear velocity of 11.68 cm / sec). At this time, NF ₃ in the gas coming out of the exhaust gas port was analyzed by gas chromatography, and as a result, N
F ₃ is not detected. Table 1 shows the results.

Example 6 A packed column treated in the same manner as in Example 1 except that the treatment temperature was set to 900 ° C. was transferred to a detoxification apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and N ₂ was added at room temperature. Gas with NF ₃ concentration of 1% diluted at 1500 cc / min
(Vent at a linear velocity of 11.68 cm / sec). At this time, NF ₃ in the gas coming out of the exhaust gas port was analyzed by gas chromatography.
F ₃ was not detected. Table 1 shows the results.

Example 7 A reducing metal catalyst containing Cu as a main component was used for a length of 500 m.
m, an apparatus equipped with a stainless steel column having an inner diameter of 16.5 mmφ, a gas inlet pipe, an exhaust gas pipe on both sides, a joint for connecting the column, and a heater for heating the column was used. 120 mm (25 m)
l, 15.5 g), and processed under the same conditions using the apparatus of Example 1. The treated packed column is moved to a scrubber equipped with a gas introduction pipe and an exhaust gas pipe, and a gas having a NF ₃ concentration of 1% diluted with N ₂ at room temperature is supplied to the apparatus.
00cc / min (superficial line velocity 11.68cm / se
Vent at the flow rate of c). At this time, as a result of analyzing NF ₃ in the gas discharged from the exhaust gas port by gas chromatography, NF ₃ was not detected until 24 minutes after the ventilation. Table 1 shows the results.

Example 8 A reducing metal catalyst containing Zn as a main component was used for a length of 500 m.
m, an apparatus equipped with a stainless steel column having an inner diameter of 16.5 mmφ, a gas inlet pipe, an exhaust gas pipe on both sides, a joint for connecting the column, and a heater for heating the column was used. 120 mm (25 m)
l, 19.3 g), and the mixture was treated using the apparatus of Example 1 under the same conditions. The treated packed column is moved to a scrubber equipped with a gas introduction pipe and an exhaust gas pipe, and a gas having a NF ₃ concentration of 1% diluted with N ₂ at room temperature is supplied to the apparatus.
00cc / min (superficial line velocity 11.68cm / se
Vent at the flow rate of c). At this time, as a result of analyzing NF ₃ in the gas discharged from the exhaust gas port by gas chromatography, NF ₃ was not detected until 30 minutes after the ventilation. Table 1 shows the results.

Comparative Example 1 A packed column treated in the same manner as in Example 1 except that the treatment temperature was set to 200 ° C. was transferred to a detoxification apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and N ₂ was added at room temperature. Gas with NF ₃ concentration of 1% diluted at 1500 cc / min
(Vent at a linear velocity of 11.68 cm / sec). At this time, as a result of the NF ₃ in the gas exiting from the gas outlet was analyzed by gas chromatograph until 3 minutes after venting NF ₃
Was not detected. Table 1 shows the results.

Comparative Example 2 A packed column treated in the same manner as in Example 1 except that the treatment temperature was changed to 1100 ° C., was transferred to an abatement apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and N ₂ was added at room temperature. Gas with NF ₃ concentration of 1% diluted at 1500 cc / min
(Vent at a linear velocity of 11.68 cm / sec). At this time, NF ₃ in the gas coming out of the exhaust gas port was analyzed by gas chromatography.
F ₃ was not detected. Table 1 shows the results.

Comparative Example 3 An apparatus equipped with a stainless steel column having a length of 500 mm and an inner diameter of 16.5 mmφ, a gas inlet pipe, an exhaust gas pipe on both sides, a joint for connecting the column, and a heater for heating the column was used. 4mmφ × 4m at the center of the column
The treatment agent formed in a tablet shape of mH
mm (25 ml, 25.5 g). The treating agent used was a nickel catalyst used as a reducing catalyst. This nickel catalyst is obtained by solidifying metallic nickel and nickel oxide with diatomaceous earth.
Contains. After filling the treatment agent, the treatment agent is activated by reducing the iron oxide in the treatment agent with hydrogen by passing hydrogen through the gas introduction tube for 20 hours while heating to 200 ° C. To allow the treatment to cool to room temperature. The packed column thus treated is moved to an abatement apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and a gas having a NF ₃ concentration of 1% diluted with N ₂ at room temperature is supplied at 1500 cc / m 2.
Vent at a flow rate of in (superficial linear velocity 11.68 cm / sec). At this time, NF ₃ in the gas coming out of the exhaust gas port was analyzed by gas chromatography.
NF ₃ was not detected. Table 1 shows the results.

Comparative Example 4 A packed column treated in the same manner as in Comparative Example 3 was transferred to an abatement apparatus equipped with a gas introduction pipe and an exhaust gas pipe, and the NF ₃ concentration diluted with N ₂ at room temperature was 0.1%. Gas with
700 cc / min (superficial linear velocity 21.03 cm / se
Vent at the flow rate of c). At this time, NF ₃ in the gas flowing out from the exhaust gas port was analyzed by gas chromatography, and as a result, NF ₃ was detected immediately after ventilation. Table 1 shows the results.

[0021]

[Table 1]

[0022]

As described above, the present invention provides:
NF on metal activated with carbon monoxide ₃Act on contained gas
NF₃Including
Exhaust gas is separated without adding hydrogen during the treatment.
Can be solved. Moreover, the treatment is performed at room temperature
Simplification of the entire abatement system
And its handling is simple and practical.
ing. Also, the amount of treatment per unit volume of catalyst is large, and
Removal of harmful nitrogen oxides is possible, and a wide range of gas flow rates
Can be used with

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B01J 37/08 B01J 23/74 301A (56) References JP-A-5-261247 (JP, A) JP-A-7-171343 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/34

Claims (1)

(57) [Claims] 1. A reducing metal catalyst comprising 300 to 1000
A method for removing nitrogen trifluoride gas, comprising activating carbon monoxide at a temperature of 0.degree. C. and contacting the activated reducing metal catalyst with a gas containing nitrogen trifluoride at room temperature.