JP3490751B2 - Decomposition method of gaseous fluoride - 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 a gas exhausted from a semiconductor etching process, or a gaseous fluoride or a gas containing the gaseous fluoride of a refrigerant exhausted from an air conditioner or the like when repairing the gas. Furthermore, the present invention relates to a method of detoxifying the gas produced by decomposition by treating it with an adsorbent.

[0002]

Gaseous fluorides used in semiconductor etching processes, such as CF ₄ , C ₂ F ₆ , C _{3
F 8, CHF 3, CH 2} F 2, SF 6, NF 3 or the like, be applied for use in the process, 10-30%
Only to a certain extent, it is decomposed and used for etching, and the remaining 70 to 90% is exhausted without being used and released into the atmosphere. Chlorofluorocarbon (CFC) used in refrigeration equipment, refrigerators or air conditioners
All of the gases such as -11 and 12 cannot be captured during repair, and some of them are released into the atmosphere.

However, these gases are said to contribute to global warming, and as is well known, CFC is a substance that destroys the ozone layer, and the phase-out schedule for its production and consumption is determined. It is a substance. Furthermore, the harmfulness of NF ₃ becomes a problem when it is released into the atmosphere. Therefore, it is necessary to decompose these gases before releasing them into the atmosphere to eliminate the influence on the environment.

Therefore, various methods for decomposing these gaseous fluorides such as a combustion method, a plasma decomposition method, an oxidative decomposition method, a hydrogenolysis method, a supercritical water method, and a microbial decomposition method have been studied and proposed. . However, of these, only the combustion method is actually used on a commercial scale, and the others are still in the trial stage.

In the combustion method, the gas discharged is hydrogen / oxygen,
This is a method of burning with propane, city gas, etc., washing the generated gas with an alkali, etc., and fixing the fluoride ions in the form of calcium fluoride or the like.

When a gaseous fluoride, particularly an etching gas or a cleaning gas used in a semiconductor etching process, is processed by a combustion method, 1) it is a stable gas, and therefore it is necessary to directly mix it in a flame. Becomes unstable and causes an extinguishing condition,
Unburned gas may accumulate inside the furnace and cause an explosion. 2) A large amount of air is required, which affects air control in the clean room. 3) Since a large amount of air is mixed in the exhaust gas, it is necessary to upsize the exhaust gas processing device after combustion, which increases equipment costs and processing costs. 4) Fluoride causes burner corrosion. 5) Noise during combustion becomes a problem. There are drawbacks, etc.

[0007]

Therefore, at present, there is a demand for the development of an inexpensive method / apparatus capable of efficiently decomposing and detoxifying gaseous fluorides and releasing them. Therefore, the object of the present invention is to eliminate the drawbacks of the conventional combustion method, an efficient and inexpensive decomposition method of gaseous fluoride,
Another object is to provide a method for preventing the release of harmful gas into the atmosphere by subjecting decomposition products to adsorption treatment.

[0008]

Means for Solving the Problems The present invention (1) (except hydrogen fluoride) gaseous fluoride or (except hydrogen fluoride) gas containing gaseous fluoride presence of hydrogen fluoride,
A method for decomposing gaseous fluorides (excluding hydrogen fluoride) , which comprises contacting with a decomposing agent consisting of one or more kinds selected from oxides of Si or B at a temperature of 500 ° C to 1500 ° C , And (2) the gas generated by the decomposition is treated with at least one adsorbent main agent selected from activated alumina, zeolite, soda lime, and silica gel, and sodium sulfite, sodium thiosulfate, manganese oxide / copper oxide, potassium permanganate. The above-mentioned decomposition method is characterized by further comprising a step of contacting with an adsorbent consisting of one or more adsorption aids selected from the above.

According to the present invention, the gas exhausted from the semiconductor etching process or the gaseous fluoride of the refrigerant exhausted from the air conditioning equipment at the time of repair can efficiently decompose the gas containing the gaseous fluoride. . Further, the present invention solves the drawbacks of the conventional combustion method and has the following advantages. 1) Since no flame is used, there is no possibility of extinguishing the fire or incomplete combustion. 2) It is easy to control the temperature. 3) A large amount of air is not required, and the total amount of exhaust gas is small. 4) The entire device becomes compact. That is, the floor of an expensive clean room can be effectively used, the air management is facilitated, and the noise is eliminated.

Gaseous fluorides to which the method of the present invention can be applied include gaseous fluorides used in semiconductor etching processes, such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ and CH.
_{F 3, CH 2 F 2,} SF 6, NF 3 or the like and the exhaust gas from the etching process including these, cleaning gases, more CFC's of the etching apparatus including these, hydrochlorofluorocarbons (HCFC) such, hydrofluorocarbons ( HFCs) can be mentioned.

The decomposing agent used in the present invention is Si or B.
Of these oxides, Si oxide is particularly preferable, and more specifically, silicon oxide and high silica zeolite can be mentioned.

The adsorbent is selected from one or more adsorbent main agents selected from activated alumina, zeolite, soda lime and silica gel, and sodium sulfite, sodium thiosulfate, manganese oxide / copper oxide and potassium permanganate. One or more of the adsorbent adsorbents, and the ratio of the adsorbent main agent to the adsorbent adjunct is 1: 0.01 to 1: 0.1 by volume,
It is particularly preferably 1: 0.05 to 1: 0.08, and the mixture is used.

Hydrogen fluoride is the most reactive hydrogen halide and reacts extremely well with decomposers. For example, due to the reaction of SiO ₂ + 4HF → SiF ₄ + 2H ₂ O on the surface of the decomposing agent, SiF ₄ and H ₂ O are volatilized, the surface of the decomposing agent becomes porous, and more efficiently reacts with the gaseous fluoride. become.

The amount of hydrogen fluoride is preferably 1% or more in terms of volume with respect to the amount of gaseous fluoride, and if it is less than 1%, the effect of the present invention cannot be obtained and the decomposition rate decreases. Further, although there is no particular upper limit, if the amount of hydrogen fluoride is large, the load on the adsorbent becomes large and the life of the adsorbent becomes short.
Therefore, the practical range is 10% or less. Further, if the decomposition temperature is 500 ° C. or higher, a sufficient decomposition rate can be obtained. However, even if the temperature is lower than 500 ° C., the decomposition rate can be maintained by slowing the charging rate of the gaseous fluoride. However, if the charging speed becomes too slow, it will not be practical, so 500 ° C
That's it. On the other hand, there is no particular upper limit to the temperature, but considering the heat-resistant temperature of the furnace and the like, it is not practical at 1500 ° C or higher. Yo
Therefore, the temperature is preferably 500 to 1500 ° C.

FIG. 1 shows a schematic block diagram of an example of an apparatus used for implementing the present invention. 1 is a line for charging gaseous fluoride. Reference numeral 2 is a hydrogen fluoride introduction tube. Reference numeral 3 is a decomposing agent introducing pipe, and when decomposing continuously, the decomposing agent is introduced into the system through this line. 5
Is a decomposer filled with a decomposer, and is heated by an electric heater 6; A temperature controller 7 controls the temperature of the decomposer.

Numeral 4 is a preliminary one which is used as a hydrogen fluoride introduction pipe in some cases or used for nitrogen substitution in the system. A cooler 8 cools the decomposed gas to near room temperature. In this example, water is used as the cooling medium. Reference numerals 9 and 11 denote sampling ports. Reference numeral 10 denotes an adsorption column filled with an adsorbent, which detoxifies the decomposed gas and releases the detoxified gas from a release pipe 12.

The outline of the device according to the present invention has been described above, but a device in which these devices are integrated is compact,
It is easy to handle and enables effective decomposition and detoxification of exhaust gas.

[0018]

[Examples] The following examples , comparative examples, and reference examples
The present invention will be described more specifically. (Examples 1 to 6, Comparative Examples 1 to 4 , and Reference Example 1 ) Experiments were conducted using the apparatus shown in FIG. The decomposer has an outer diameter of 38 mm,
It was made of high-grade alumina having an inner diameter of 35 mm and a length of 1,000 mm, and 500 ml of a decomposing agent was filled in this and electrically heated. The adsorption column was made of PVC with an inner diameter of 3 inches and a length of 300 mm, and was filled with 1200 ml of an adsorbent. The adsorbent was prepared as follows according to the type of gas (A, B and C). Organic fluoride: 600 ml each of activated alumina and soda lime mixed with 60 ml of sodium sulfite (Table 1: A) Sulfur hexafluoride: 6 each of zeolite and soda lime
Mixture of 60 ml of sodium sulfite to 00 ml (Table 1: B) Nitrogen trifluoride: Mixture of 60 ml of potassium permanganate to 600 ml of activated alumina and soda lime (Table 1) 1: C)

During the experiment, the sampling port 9 is regularly
The decomposition rate and the total concentration of fluorine and chlorine compounds produced by decomposition in the exhaust gas were measured by sampling from No. 11, and the experiment was terminated when the concentration became 1 mg / l or more. The experimental conditions and results are summarized in Table 1.

In the comparative example carried out without adding hydrogen fluoride, the decomposition rate was low and the concentration of undecomposed gaseous fluoride was high. These compounds are chemically inert and rarely treated with adsorbents. Since the treatment amount of the adsorbent is determined by the amount of decomposition products, it can be seen that the comparative example has a longer execution time.

[0021]

[Table 1]

[0022]

EFFECTS OF THE INVENTION By using hydrogen fluoride in combination with the decomposing agent, the decomposition efficiency is remarkably improved, the safety of exhaust gas is easily achieved, and the equipment can be made compact.

[Brief description of drawings]

1 is a schematic block diagram of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

1 Gaseous fluoride supply line 2 Hydrogen fluoride supply line 3 Decomposing agent supply device 4 Hydrogen fluoride or nitrogen supply line 5 decomposer 6 electric heater 7 Temperature control device 8 cooler 9, 11 Sampling port 10 adsorption cylinder 12 emission line

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-3-181316 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/68

Claims (2)

(57) [Claims] 1. A gaseous fluoride (except hydrogen fluoride) or (except hydrogen fluoride) gas containing gaseous fluoride presence of hydrogen fluoride, S at a temperature of 500 ° C. to 1500 ° C.
A gaseous fluoride characterized by being brought into contact with a decomposing agent comprising one or more kinds selected from oxides of i or B.
Decomposition method (excluding hydrogen fluoride) . 2. The gas produced by the decomposition is treated with at least one adsorbent main agent selected from activated alumina, zeolite, soda lime and silica gel and sodium sulfite, sodium thiosulfate, manganese oxide / copper oxide, permanganate. The decomposition method according to claim 1, further comprising a step of contacting with an adsorbent composed of one or more adsorption aids selected from potassium.