JPH1147555A - Detoxification process for nitrogen trifluoride and detoxification catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat NF3 safely and efficiently for a long period of time. SOLUTION: Exhaust gas containing nitrogen trifluoride is reacted with hydrogen in the presence of a catalyst containing a first component selected out of the first group composed of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, Pt and Au and the second component composed of at least one kind of alkaline metal fluoride and alkaline earth metal fluoride. Also a catalyst of pretreating nitrogen trifluoride containing the first component selected out of a group composed of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, Pt and Au and the second component composed of at least one kind of alkaline metal fluoride and alkaline earth metal fluoride is prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the nitrogen trifluoride gas abatement method (hereinafter, referred to as NF _3), and to a catalyst for abating NF _3.

[0002]

2. Description of the Related Art At present, it is well known that restrictions are imposed on chlorofluorocarbons and CO ₂ which have a bad influence on the global environment, and NF ₃ is also a substance which is not easily decomposed in nature. In recent years, a large amount of NF ₃ gas has been used as a cleaning gas in semiconductor manufacturing. However, since it is toxic and has a large global warming effect, it is desired to remove NF ₃ remaining in exhaust gas.

As a method for solving the above problem, there is known a method in which an exhaust gas containing NF _{3 is} passed through a column filled with activated carbon at a high temperature (Japanese Patent Application Laid-Open No. 62-237929). However, in this method, resulting in the release of CF _4, also referred to as one of the causes of global warming.

Further, although it is reacted with the metal oxide has been known a method of abating (JP-A-3-181316), which is also added to carry out the reaction at a high temperature of about 500 ° C., NO _x There is a problem that generates. Further, since the metal oxide becomes a metal fluoride by the reaction and loses the NF ₃ abatement ability, it is necessary to periodically take out the metal fluoride and fill the metal oxide, which has a disadvantage that the running cost is increased.

Further, a method is known in which NF _{3 is} passed through a column filled with a metal which generates gaseous fluoride at a high temperature (Japanese Patent Application Laid-Open No. 61-204025). However, there is a disadvantage that metal oxide fine particles are generated in the gaseous fluoride secondary treatment facility to be used, and the treatment is required.

The above-mentioned abatement method has a common drawback that the abatement agent charged in the abatement apparatus needs to be replaced or replenished, which increases the running cost. On the other hand, a method of removing NF ₃ by reacting it with a reducing gas in the presence of a catalyst is known, and has the advantage that the frequency of catalyst replacement is much lower than the frequency of replacement of the harm removing agent. .

[0007] JP-A-2-303524 discloses a method using hydrogen as a reducing gas. Examples of the reduction catalyst include Vll group elements of the periodic table and Cu,
Metals containing at least one selected from the group consisting of Cr and Zn are mentioned. However, according to the findings of the present inventors, when these catalysts are used by being supported on a commonly used carrier such as alumina, silica, titania, and silica-alumina, the catalytic activity decreases with time, and a stable catalyst is used. It turned out that performance could not be obtained.

Japanese Patent Application Laid-Open No. 8-131774 discloses a method using hydrocarbon as a reducing gas. However, there is a fear that CF ₄ is generated by a reaction between NF ₃ and hydrocarbon, and global warming is caused. It is not desirable from the viewpoint of prevention. JP-A-3-65219 discloses a method using hydrogen chloride, but it is not desirable to use hydrogen chloride which is a corrosive and toxic gas.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for safely and efficiently removing NF ₃ and a catalyst thereof.

[0010]

Means for Solving the Problems The present inventors have intensively studied a method which can improve the disadvantages of the prior art and can be implemented industrially, and as a result, have found that a specific metal and a fluoride of an alkali metal or an alkaline earth metal can be obtained. The present invention has been completed by finding a method for removing NF ₃ by using a catalyst as a carrier.

That is, the present invention relates to Fe, Co, Ni, C
u, Zn, Ru, Rh, Pd, Ag, Ir, Pt, Au
An exhaust gas containing nitrogen trifluoride and hydrogen in the presence of a catalyst containing a first component selected from the group consisting of a first component and at least one of an alkali metal fluoride and an alkaline earth metal fluoride. To remove nitrogen trifluoride, wherein Fe, Co, N
i, Cu, Zn, Ru, Rh, Pd, Ag, Ir, P
a first component selected from the group consisting of t and Au and at least one of an alkali metal fluoride and an alkaline earth metal fluoride;
The present invention relates to a catalyst for removing nitrogen trifluoride, which comprises a second component comprising at least one species.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail. Abatement process of the present invention is an exhaust gas from an ultra LSI etching apparatus, the exhaust gas of CVD cleaning gas, such as leakage gases from NF ₃ container, applied to the abatement of gas containing NF _3. The gas containing NF ₃ reacts with hydrogen and is harmed.

The catalyst used in the present invention is Fe, Co,
Ni, Cu, Zn, Ru, Rh, Pd, Ag, Ir, P
a first component selected from the group consisting of t and Au and at least one of an alkali metal fluoride and an alkaline earth metal fluoride;
It comprises a second component comprising at least one species.

Among the first components, Ni, Ru, Pd, P
t is highly active and is particularly desirable. The content of the first component contained in the catalyst is 0.01 to 70% by weight, preferably 0.1 to 70% by weight.
1 to 50% by weight is preferred. Content is 0.01% by weight
If it is less than 70% by weight, the catalytic activity is too low, and if it exceeds 70% by weight, the dispersion of the active ingredient is deteriorated, and the catalytic activity is undesirably reduced. The optimum value of the content of the first component differs depending on the type of metal. For example, when the first component is Ni, 10 to 10
50% by weight, 0.1% when the first component is Ru, Pd, Pt.
1-5% by weight is preferred. The second component is Li, Na, K,
Rb, Cs, Mg, Ca, Sr, or Ba fluoride.

The catalyst may have any shape such as a sphere, a tablet, a ring, and a crushed product (irregular type). In molding, after forming the second component into a predetermined shape, the first component may be supported by a known method such as impregnation or coating, or the first component and the second component are mixed in a dry or wet method. After that, it may be formed into a predetermined shape.

As a method for producing the catalyst, a method may be employed in which the molded carrier comprising the second component is immersed in a solution containing the compound of the first component, and then dried and calcined to impregnate and carry the first component. it can. Further, an aqueous solution of the water-soluble salt of the first component is mixed with an appropriate precipitant to form a precipitate comprising the compound of the first component, and this is mixed with the second component as a slurry or after drying, The catalyst can be formed by molding and firing. Further, a method in which the first component powder in the form of a simple metal or a compound is mixed with the second component, and molded and calcined to obtain a catalyst may be employed. The catalyst of the present invention is not limited by its production method, and a catalyst produced by a method other than the above is also included in the scope of the present invention.

The reaction temperature between hydrogen and NF _{3 in} the presence of a catalyst is appropriately selected usually from room temperature to 600 ° C. Above all, 100-450 ° C, preferably 150-300 ° C
It is good to react with. If the reaction temperature is too low, the reaction cannot proceed at an industrially acceptable rate, and if the reaction temperature is too high, problems arise in the heat resistance and corrosion resistance of the apparatus, and equipment costs increase, which is not preferable.

It is particularly important to ensure safety in the reaction between hydrogen and NF _{3 in} the presence of a catalyst. This includes hydrogen and N
It goes without saying that the gas composition is controlled so that F ₃ does not form an explosive gas mixture, but it is important that the temperature rise of the reactor due to the heat generated by the reaction be suppressed to an appropriate range. Therefore, NF ₃ is diluted with an inert gas to 2% by volume or less (hereinafter, volume% is simply expressed as%), preferably 1.5% or less, more preferably 1% or less before being mixed with hydrogen. Is done. As the inert gas for dilution, nitrogen is usually used.

The molar ratio of added hydrogen to NF ₃ is preferably 1.5 to 10, more preferably 1.5 to 5. If the molar ratio is less than 1.5, the decomposition rate of NF ₃ is undesirably low. Further, if the molar ratio exceeds 10, the decomposition rate of NF ₃ does not increase, and a large amount of hydrogen, which is a flammable gas, remains undesirably. If the hydrogen concentration is 5% or less,
It is preferable that the hydrogen concentration is 5% or less, since no reaction with NF ₃ occurs, and there is no danger of explosion even if hydrogen is released to the atmosphere without being consumed in the NF ₃ abatement equipment. Assuming that the NF ₃ concentration is 1.5% and the hydrogen concentration is 5%, the molar ratio of hydrogen to NF ₃ is 3.3, which is included in the above-mentioned preferable molar ratio. Space velocity of reaction is 10
0-100,000 hr ^-1 , preferably 500-5
000 hr ^-1 is preferred.

The reaction of NF ₃ with hydrogen in the presence of a catalyst produces a fluorine compound such as hydrogen fluoride. As an adsorbent for removing the fluorine compound, a basic oxide such as alkaline earth oxide or soda lime, sodium fluoride, molecular sieve, activated alumina and the like are used. These adsorbents are inexpensive and result in reduced running costs for the NF ₃ abatement process. Further, a method of treating a fluorine compound such as hydrogen fluoride with a scrubber can also be used.

[0021]

EXAMPLES Hereinafter, the method of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, weight% is expressed by wt%, and volume% is simply expressed by%. Example 1 Nickel powder 30 wt% and calcium fluoride powder 70 wt
% Was uniformly mixed in a plastic bag, a small amount of water was added, and a paste-like mixture was prepared in an automatic mortar. This mixture was dried at 120 ° C. for 1 hour, pulverized to a particle size of 0.5 mm or less, and tableted to produce a tablet having a diameter of 5 mm and a height of 5 mm. The Ni (30 wt.
%) / CaF ₂ catalyst was crushed to a particle size of 1 to ₂ mm,
was charged into a flow reactor having an inner diameter of 20 mm. In addition, 500 ml of soda lime having a particle size of
And connected to the downstream side of the reactor filled with the catalyst. A gas consisting of 1% of NF ₃ , 5% of hydrogen and the balance of nitrogen was supplied to the reactor at a space velocity (SV) of 1200 hr ⁻¹ and reacted at 250 ° C. One hour, 5 hours, and 100 hours after the start of the reaction, the exhaust gas at the outlet of the soda lime-filled reactor (adsorber) was analyzed by gas chromatography, but NF ₃ was not detected. Also, the exhaust gas at the outlet of the adsorption device is passed through a bubbler containing water,
As a result of analyzing the components dissolved in water, no fluorine compound was detected.

Example 2 Nickel powder 30 wt%, sodium fluoride powder 70 wt
% Was uniformly mixed in a plastic bag, and was tableted as it was to produce a tablet having a diameter of 5 mm and a height of 5 mm.
The Ni (30 wt%) / NaF catalyst thus obtained was pulverized to a particle size of 1 to 2 mm, and a reaction was carried out in the same manner as in Example 1 using 40 ml of the pulverized powder. One hour, five hours, and 100 hours after the start of the reaction, the exhaust gas at the outlet of the soda lime-filled reactor (adsorber) was analyzed by gas chromatography, and as a result, NF ₃ was not detected.

Example 3 A calcium fluoride compact was pulverized to a particle size of 1 to 2 mm. 1.67 g of palladium chloride (PdCl ₂ ) was added to 1N-KCl
It was dissolved in 100 ml of an aqueous solution, and 100 g of the pulverized calcium fluoride was added thereto. After standing at room temperature for 1 hour, 0.3 g of sodium borohydride was added to reduce palladium. After completion of the reduction, the solution was removed by filtration, dried at 120 ° C. for 1 hour, then calcined at 400 ° C. for 1 hour, and Pd (1 wt.
%) / CaF ₂ catalyst was produced. 40 ml of this catalyst was charged into a flow reactor having an inner diameter of 20 mm. In addition, particle size 1
500 ml of 2 mm soda lime was charged into a flow reactor having an inner diameter of 20 mm, and connected to the downstream side of the reactor filled with the catalyst. A gas consisting of 1% of NF ₃ , 5% of hydrogen and the balance of nitrogen was supplied to the reactor at a space velocity (SV) of 1200 hr ⁻¹ and reacted at 220 ° C. One hour after the start of the reaction,
After 5 hours and 100 hours, the exhaust gas at the outlet of the soda lime filling reactor (adsorber) was analyzed by gas chromatography, and as a result, NF ₃ was not detected.

Comparative Example 1 A Ni (30 wt%) / Al ₂ O ₃ catalyst was produced in the same manner as in Example 1 except that γ-alumina was used instead of calcium fluoride. Using 40 ml of this catalyst, a reductive decomposition experiment of NF ₃ was performed under the same conditions as in Example 1. One hour and 5 hours after the start of the reaction, NF ₃ was contained in the exhaust gas at the outlet of the soda lime-filled reactor (adsorber). ₃ was not detected, but after 100 hours, 0.17% of NF ₃ was detected.

Comparative Example 2 Example 1 except that titania was used in place of calcium fluoride.
A Ni (30 wt%) / TiO ₂ catalyst was produced in the same manner as described above. An experiment of reductive decomposition of NF ₃ was carried out under the same conditions as in Example 1 using 40 ml of this catalyst.
Soda lime filled reactor in the time after it NF ₃ was detected in the exhaust gas (adsorption apparatus) outlet, 0.01% after 5 hours, after 100 hours was detected 0.20% of NF ₃ .

Comparative Example 3 In the same manner as in Example 3 except that γ-alumina having a particle size of 1 to 2 mm was used instead of calcium fluoride, Pd (1 wt%) /
An Al ₂ O ₃ catalyst was produced. Using 40 ml of this catalyst, a reductive decomposition experiment of NF ₃ was performed under the same conditions as in Example 3. One hour and 5 hours after the start of the reaction, NF ₃ was contained in the exhaust gas at the outlet of the soda lime-filled reactor (adsorber). ₃
Was not detected, but 0.25% of NF ₃ was detected after 100 hours.

Examples 4-7 Fe (30 wt%) was obtained in the same manner as in Example 1 except that powders of iron, cobalt, copper and zinc were used instead of nickel powder.
/ CaF ₂ , Co (30 wt%) / CaF ₂ , Cu (3
0 wt%) / CaF ₂ , and Zn (30 wt%) / C
the aF ₂ catalyst was prepared. Table 1 shows the results of a reductive decomposition experiment of NF ₃ performed under the same conditions as in Example 1.

Examples 8 to 10 Ruthenium chloride Ru instead of palladium chloride PdCl ₂
Cl ₃ , rhodium chloride RhCl ₃ , and chloroplatinic acid H
Ru (1 wt%) / CaF ₂ , Rh (1w) in the same manner as in Example 3 except that a predetermined amount of ₂ PtCl ₆ was used.
t%) / CaF ₂ , Pt (1 wt%) / CaF ₂ catalyst were prepared. Table 1 shows the results of a reductive decomposition experiment of NF ₃ performed under the same conditions as in Example 3.

[0029]

[Table 1]

[0030]

According to the present invention by using a catalyst for a specific metal and an alkali metal or alkaline earth metal fluoride with a carrier, it is possible abatement of NF ₃ is stably performed over a long period of time Was. That is, the comparative example of the present invention cannot remove NF _{3 in} a relatively short time. On the other hand, in the embodiment of the present invention, it is possible to remove NF ₃ even if it exceeds 100 hours, and it is possible to stably remove the NF _{3 for} a long time.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroko Wachi 7-1-1, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Pref.

Claims (2)

[Claims] 1. Fe, Co, Ni, Cu, Zn, R
of a catalyst containing a first component selected from the group consisting of u, Rh, Pd, Ag, Ir, Pt, and Au and a second component consisting of at least one of alkali metal fluorides and alkaline earth metal fluorides A method for removing nitrogen trifluoride, comprising reacting an exhaust gas containing nitrogen trifluoride with hydrogen in the presence of hydrogen. 2. Fe, Co, Ni, Cu, Zn, R
u, Rh, Pd, Ag, Ir, Pt, Au, containing a first component selected from the group consisting of at least one of alkali metal fluorides and alkaline earth metal fluorides. Characteristic catalyst for removing nitrogen trifluoride.