JPH10165764A - Agent and process for detoxifying nitrogen trifluoride gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat safely and efficiently nitrogen trifluoride gas (NF3 ). SOLUTION: In a pretreatment process, a pretreatment agent for mixing 0.3-100 pts.wt. of a metallic fluoride or a metallic oxide with 1 (one) pt.wt. of at least one kind or more of metals of Si, Ge, W and Mo and at least one kind or more of metals of Si, Ge, W and Mo on the upper stream side of ventilating gas and a metallic fluoride or a metallic oxide on the downstream side of ventilating as are filled in a column, and heated at 150-500 deg.C, and gas containing nitrogen trifluoride gas is passed through therein. Or 0.3-100 pts.wt. of a metallic fluoride or a metallic oxide is mixed with 1 (one) pt.wt. of at least one kind or more of metals of Si, Ge, W and Mo, and a mixture thus formed is filled in the column, and heated at 150-500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an abatement agent and an abatement method for nitrogen trifluoride gas.

[0002]

[Prior art] nitrogen trifluoride gas (hereinafter referred to as NF ₃₎
Has recently been used in large quantities as a cleaning gas in semiconductor manufacturing. However, since it is toxic, it is necessary to remove NF ₃ remaining in the exhaust gas.

As a method for solving the above-mentioned problem, a method is known in which exhaust gas containing NF _{3 is} passed through a column filled with activated carbon at a high temperature. However, in this method, resulting in the release of CF _4, also referred to as one of the causes of lower global warming.

[0004] In addition, a column filled with a metal at a high temperature has N
Although F ₃ is also known a method of venting, must be treated in the washing tower or the like gaseous fluoride produced by this, there is a disadvantage that the device size. Further, a method using a metal oxide is also known. However, this method is also performed at a high temperature of about 500 ° C. and has a problem that NOx is generated.

[0005]

At present, it is well known that restrictions are imposed on chlorofluorocarbons and CO ₂ which have an adverse effect on the global environment, and NF ₃ is also a substance which does not readily decompose in nature. Therefore, an object of the present invention is to treat NF ₃ safely and efficiently.

[0006]

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 carried out industrially. As a result, by using the specified metal under the specified conditions, the NF ₃ The present inventors have found an abatement method and have achieved the present invention.

That is, the present invention is characterized in that 0.3 to 100 parts by weight of a metal fluoride or a metal oxide is mixed with 1 part by weight of a metal of at least one of Si, Ge, W and Mo. A column is filled with an abatement agent for nitrogen trifluoride gas, at least one metal selected from the group consisting of Si, Ge, W, and Mo on the upstream side of the ventilation gas, and a metal fluoride or metal oxide on the downstream side. Heating at 500 ° C. and passing a gas containing nitrogen trifluoride gas, or Si,
A metal fluoride or metal oxide is used in an amount of 0.3 to 1 with respect to 1 part by weight of at least one of Ge, W, and Mo.
00 parts by weight, and the mixture was packed in a column,
The present invention relates to a method for removing nitrogen trifluoride gas, which comprises heating at a temperature of about 500 ° C.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail. Metal used in the present invention is relatively inexpensive, easy to handle, and a metal capable of generating a gaseous fluoride by reaction with NF _3, further gaseous fluoride metal this produces It is indispensable to be able to react and adsorb to fluoride or metal oxide. Therefore, metals satisfying the above conditions include Si, Ge, W, and Mo, and at least one or more of these metals are used. Among them, Si is most preferable because it is inexpensive and can be used sufficiently if its purity is 98% by weight or more.

These metals react with NF ₃ at a temperature of 150 ° C. or higher to produce gaseous fluoride. This gaseous fluoride reacts or adsorbs with the metal fluoride or metal oxide in the same column. Therefore, since gaseous fluoride as well as NF ₃ is removed, the treatment can be performed efficiently.

Therefore, when each of these metals is filled with a metal fluoride or metal oxide, the metal is placed upstream of the column packed layer and the metal fluoride or metal oxide is placed downstream of the gas to be passed. Need to fill the side. Further, in this case, it is preferable to use a soul-like metal rather than a powdery metal so that the gas flow resistance does not increase, and it is preferable to mold and use a metal fluoride or a metal oxide. More preferably, it is a method using an abatement agent obtained by molding a mixture of powdered metal and metal fluoride or metal oxide by granulation or compression.

The use or type of the binder at the time of molding is not specified at all in the present invention, but generally used methylcellulose, methylethylcellulose, polyvinyl alcohol and the like are used.
By using an abatement agent obtained by molding a mixture of powdered metal and metal fluoride or metal oxide by granulation or compression, the filling operation is simple, and the method described above,
That is, in the method of filling the metal and the metal fluoride or the metal oxide, there is no trouble such that the metal is erroneously filled in reverse, and it can be said that the method is suitable from the viewpoint of safety.

As the metal fluoride used in the present invention, many can be used, and among them, a metal fluoride selected from the group consisting of alkali and alkaline earth is preferred. These are those in which the gaseous fluoride generated by the reaction between the metal and NF ₃ is immobilized as silicofluoride.
iF, NaF, KF, BaF ₂ , MgF _{2 and the} like.

Although almost all metal oxides can be used, Ca, Ba, Al, and the like which react and adsorb well with the gaseous fluoride generated by the reaction between the metal and NF ₃ are used.
Mn, Sb, and Fe oxides can be suitably used. Also,
To improve the reaction and adsorption efficiency, the specific surface area is 10 m ² / g
The above are preferred. When the specific surface area is less than 10 m ² / g, the reaction adsorption efficiency is lowered, and the capacity of the packed column is undesirably increased due to the need to increase the packed amount. Among metal oxides that can be converted into solid metal fluorides by reaction, CaO is the most reactive and is preferred.

The mixing ratio of the metal and the metal fluoride or metal oxide is 0.3 to 100 parts by weight, preferably 1 to 50 parts by weight, with respect to 1 part by weight of the metal. And more preferably 3 to 20 parts by weight. The column is made of iron, a general-purpose material that can be used at high temperatures,
Made of metal such as copper, stainless steel, nickel, or
Oxides, such as glass and alumina, are generally cylindrical. In addition, as for the size, a size corresponding to the amount of detoxification and detoxification ability is used.

In the present invention, the column is heated from the outside and
Add. Column temperature is 150-500 ° C, preferably
At 200-400 ° C, more preferably at 250-350 ° C
NF ₃A gas contained in the gas is ventilated for harm. Also, 5
If the temperature exceeds 00 ° C, gaseous fluoride will be released
Not preferred.

As described above, once the NF ₃ reacts with the metal in the column, the gaseous fluoride is fixed as silicide in the reaction with the metal fluoride, and adsorbs and reacts with the metal oxide. This makes it possible to provide a detoxifying effect of not discharging fluorine-containing gas from the outlet of the column.

[0017]

The present invention will be further described below with reference to Examples and Comparative Examples.
This will be described in detail. In addition,% of gas concentration represents volume%. Examples 1 to 16 SUS columns having a length of 300 mm and an inner diameter of 12 mmφ
And a device equipped with a heater to heat the column
Used. On the upstream side of the ventilation gas of this column, Si, G
5g of metal powder or metal pieces of e, W, Mo
The side was filled with each metal fluoride and metal oxide. this
The packed column is heated to 150-500 ° C.₂gas
NF diluted in ₃50cc / min of 1% concentration gas
At a flow rate of Five minutes after the start of ventilation, the gas at the outlet is
The results of gas chromatography analysis are shown in Table 1.
Yeah, NF₃The concentration decreased and the abatement effect was observed.
In addition, the outlet gas is absorbed by water and obtained by reaction with the metal.
Analysis of gaseous fluoride
It became clear that.

Examples 17 to 30 Metal powders having a particle size of 100 μm or less among Si, Ge, W and Mo, and metal fluorides and metal oxides were mixed, and a 3 mmφ × 3 mm cylindrical molded product was obtained using a tablet machine. I got This was packed in a SUS column having a length of 300 mm and an inner diameter of 12 mmφ, and a gas having a NF ₃ concentration of 1% diluted with N ₂ gas at a column temperature of 150 to 500 ° C. was supplied at a flow rate of 50 cc / min. Ventilated. 5 from the start of ventilation
One minute later, the gas at the outlet was analyzed by gas chromatography. As a result, as shown in Table 2, the NF ₃ concentration was reduced, and the abatement effect was recognized. The outlet gas was absorbed in water, and the gaseous fluoride obtained by the reaction with the metal was analyzed. As a result, it was clarified that the gaseous fluoride was also reduced.

Examples 31-32 KF and MnO were respectively added to and mixed with 60-mesh Si metal powder, and a small amount of water and a very small amount of a binder (methylcellulose) were added to form a paste and dried at 100 ° C. This was crushed to obtain a granulated product of 8 to 12 mesh. This was packed in a SUS column having a length of 300 mm and an inner diameter of 12 mmφ, and a gas having a NF ₃ concentration of 1% diluted with N ₂ gas at a column temperature of 300 ° C. was charged to 50 c.
Vent at a flow rate of c / min. Five minutes after the start of the ventilation, the gas at the outlet was analyzed by gas chromatography, and as shown in Table 2, the NF ₃ concentration was reduced and the abatement effect was recognized. The outlet gas was absorbed in water, and the gaseous fluoride obtained by the reaction with the metal was analyzed. As a result, it was clarified that the gaseous fluoride was also reduced.

Comparative Examples 1-2 The procedure was as in Example 19, except that the heating temperature of the column was changed to 100 ° C. and 600 ° C. Five minutes after the start of aeration, the gas at the outlet was analyzed by gas chromatography. As shown in Table 3, at 100 ° C., no decrease in the NF ₃ concentration was observed. At 600 ° C., it became clear that the amount of gaseous fluoride obtained by the reaction with the metal increased.

Comparative Examples 3 to 660 A metal powder of Si, Ge, W, and Mo of 60 mesh was packed in a SUS column having a length of 300 mm and an inner diameter of 12 mmφ, and N ₂ gas was supplied at a column temperature of 300 ° C. The NF ₃ concentration of 1% gas diluted with the above was passed at a flow rate of 50 cc / min. Five minutes after the start of aeration, the gas at the outlet was analyzed by gas chromatography. As shown in Table 3, although the NF ₃ concentration was reduced, the gaseous fluoride generated by the reaction with the metal was observed. Was generated in large quantities.

Comparative Examples 7 to 8 Tablets (3
mmφ × 3mm column) 300mm long, 12 inner diameter
packed in a SUS column with a diameter of 30 mm
NF ₃ concentration 1 diluted with N ₂ gas under the temperature condition of 0 ° C.
% Gas was passed at a flow rate of 50 cc / min. Five minutes after the start of the ventilation, the gas at the outlet was analyzed by gas chromatography. As shown in Table 3, no decrease in the NF ₃ concentration was observed.

Comparative Examples 9 to 10 Tablets of CaO and MnO of 100 mesh or more (3
mmφ × 3mm column) 300mm long, 12 inner diameter
packed in a SUS column with a diameter of 45 mm
NF ₃ concentration 1 diluted with N ₂ gas under the temperature condition of 0 ° C.
% Gas was passed at a flow rate of 50 cc / min. Five minutes after the start of the ventilation, the gas at the outlet was analyzed by gas chromatography. As shown in Table 3, although a slight decrease in the NF ₃ concentration was recognized, NOx was generated.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

According to the present invention, there is provided an abatement method using NF _{3 in combination} with a specified metal and a metal fluoride or a metal oxide, and using a specified metal mixed with a metal fluoride or a metal oxide. by providing a detoxifying method and detoxifying agent, it becomes possible to efficiently abatement of NF _3. Furthermore, since the size of the abatement apparatus can be reduced, there is a great effect in terms of cost. Further, the method of the present invention uses CF ₄
Since it does not generate nitrogen oxides, it is significant in the global environment.

Claims (7)

[Claims] 1. A method of mixing one or more metals of at least one of Si, Ge, W and Mo with 0.3 to 100 parts by weight of a metal fluoride or metal oxide. Nitrogen gas abatement agent. 2. The nitrogen trifluoride gas abatement agent according to claim 1, wherein a mixture of a metal and a metal fluoride or metal oxide is formed by granulation or compression. 3. The nitrogen trifluoride gas abatement agent according to claim 1, wherein the metal fluoride is selected from the group consisting of an alkali metal and an alkaline earth metal. 4. The method according to claim 1, wherein the metal oxide is Ca, Ba, Al, M
3. The nitrogen trifluoride gas abatement agent according to claim 1, comprising n, Sb, and Fe. 5. The metal oxide has a specific surface area of 10 m ² /
The nitrogen trifluoride gas abatement agent according to any one of claims 1 to 4, which is not less than g. 6. Si, Ge, W, upstream of the ventilation gas
The column is filled with at least one metal of Mo and a metal fluoride or metal oxide on the downstream side,
A method for removing nitrogen trifluoride gas, comprising heating at 00 ° C. and passing gas contained in the nitrogen trifluoride gas. 7. A metal fluoride of 0.3 to 100 parts by weight is mixed with 1 part by weight of at least one of Si, Ge, W and Mo, and the mixture is packed in a column. A method for removing nitrogen trifluoride gas, comprising heating at 150 to 500 ° C.