JPH0669528B2 - How to remove nitrogen trifluoride - 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 contained in dry etching exhaust gas.

[0002]

2. Description of the Related Art Nitrogen trifluoride (NF ₃ ) is drawing attention as a dry etching agent or a fluorinating agent for LSI.
In particular, as a dry etching agent, it has an advantage over the perfluorocarbon type etching agent such as CF ₄ that the LSI substrate is less contaminated during etching.

On the other hand, NF ₃ is extremely stable in the atmosphere, dissolves only slightly in water, and is a toxic gas with a TLV of 10 ppm. When this is used, the residual gas is removed when it is exhausted. Will be needed.

Therefore, as a conventional method of removing NF ₃ ,
Hydrogen is mixed with a gas containing F _3, and the mixed gas is brought into contact with a reducing catalyst so that the gas is decomposed by a hydrogen reduction reaction (Japanese Patent Laid-Open No. 2-303524), NF ₃
It has been known that a gas containing Pt and a substance containing at least one of a reducing catalyst, alumina and silica as a main component are brought into contact with each other (Japanese Patent Laid-Open No. 62-273039).

[0005]

However, in the conventional abatement method, NF ₃ is decomposed under a high temperature atmosphere of 130 to 180 ° C. in the former case and about 200 ° C. in the latter case. There is a practical problem that a large-scale external heater is required, the size of the entire apparatus becomes large, handling is inconvenient, and the cost is high. The present invention has been made paying attention to such a point, and an object thereof is to provide a method of removing NF _{3 which} can be reacted at room temperature.

[0006]

In order to achieve the above-mentioned object, the present invention fills a treating cylinder with a finely divided reducing metal catalyst, and hydrogen acts on the reducing metal catalyst filled in the treating cylinder. This is characterized in that the reducing metal catalyst is activated and the activated reducing metal catalyst is brought into contact with a nitrogen trifluoride-containing gas at room temperature to decompose nitrogen trifluoride.

[0007]

According to the present invention, the reducing metal catalyst is finely granulated and packed in the treatment cylinder, hydrogen is allowed to act on the reducing metal catalyst packed in the treatment cylinder to activate the reducing metal catalyst, and the activated reduction is carried out. Since the nitrogen trifluoride-containing gas is brought into contact with the reactive metal catalyst at room temperature to decompose nitrogen trifluoride at room temperature, it is not necessary to heat the reaction tower with an external heater, and the entire apparatus can be used. It can be miniaturized and is easy to handle. As a result, it is possible to reduce the cost of removing harm.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings show experimental equipment of an apparatus for carrying out the method of the present invention, in which reference numeral (1) is a gas cylinder to be treated containing a standard gas in place of nitrogen trifluoride gas discharged from a semiconductor manufacturing equipment, (2) is a diluting gas cylinder containing diluting nitrogen gas, (3) is a processed gas passage for leading out the treated gas, (4) is a diluting gas passage for leading out the diluting gas, (5)
Is a mixed gas passage for leading out a mixed gas of a gas to be treated and a diluting gas, (6) is a treatment cylinder filled with a treating agent composed of a reducing metal catalyst, and (7) is a treatment cylinder (6) Chromatography introducing the exhaust gas of (2), (8) is a mass flow rate regulator arranged in the gas passage (3) to be treated and the gas passage (4) for dilution, and (9) is a gas passage (3) to be treated and diluted. Gas passage
The pressure reducing valves are respectively arranged in (4).

§Experimental example: A stainless steel processing cylinder (6) with an inner diameter of 16.5 mm was placed with a diameter of 3 mm.
Φ × 3 mmH tablet-shaped processing agent is crushed to a particle size of 1 to 2 mm, and 145 mm (30 m
1, 29.4 g). As the treating agent, a nickel catalyst used as a reducing catalyst was used. This nickel catalyst is obtained by solidifying metallic nickel and nickel oxide with diatomaceous earth, and contains 46% of metallic nickel and nickel oxide.

After the treating agent is filled in the treating cylinder (6), hydrogen is allowed to flow under the temperature condition of 180 to 200 ° C. for 20 hours to reduce the nickel oxide in the treating agent with hydrogen. Was activated, and after the treatment agent was activated, nitrogen was passed to cool the treatment agent to room temperature.

When the activated treatment agent has cooled to room temperature, 250 m of nitrogen gas containing 600 ppm of nitrogen trifluoride at room temperature is discharged from the upper part of the treatment cylinder (6).
l / min (empty cylinder linear velocity 1.95 cm / sec)
The exhaust gas from (6) was analyzed by gas chromatography.

[0013] When nitrogen trifluoride concentration at the inlet to the treatment column (6) is 600 ppm, the outlet, nitrogen trifluoride (NF ₃₎ as well, hydrogen fluoride (HF), ammonia (NH ₃₎ also Didn't detect. As a result, the reaction with the residual hydrogen used during activation did not detect hydrogen fluoride or the like at the outlet, so it can be presumed that it did not react with hydrogen. Therefore, the expected reaction formula at this time is estimated to be 3Ni + 2NF ₃ → 3NiF ₂ + N ₂ ↑. In addition, a thermocouple was inserted into the processing cylinder (4) during the treatment to measure the temperature rise, but the heat generation could not be measured. And, this value was allowed to pass the gas to be treated continuously for 15 hours.

Even when a gas containing 1000 ppm of nitrogen trifluoride was passed through the treatment cylinder (4), nitrogen trifluoride, hydrogen fluoride and ammonia were not detected. In addition, a temperature rise of about + 3 ° C. was detected in the processing cylinder (4). Then, this value could be obtained by allowing the gas to be treated to pass continuously for 8 hours.

In the above examples, the nickel catalyst used as the reducing catalyst was used as the treating agent, but as the treating agent, copper, chromium, aluminum, barium, iron, zirconium, manganese, etc. are the main components. The reducing metal catalyst can be used.

[0016]

According to the method of the present invention, the trifluoronitrogen-containing gas is caused to act on the metal activated with hydrogen so that the metal is decomposed. Therefore, the exhaust gas containing nitrogen trifluoride is added with hydrogen during the treatment. It can be decomposed without doing. Moreover, since the treatment can be carried out at room temperature, the harm removing apparatus as a whole can be simplified, and its handling is simple, and it is excellent in practicality. In addition, since hydrogen is not added when decomposing nitrogen trifluoride, by-products such as hydrogen fluoride are not generated due to the treatment, and it is possible to completely detoxify at the outlet of the treatment cylinder.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of experimental equipment for carrying out the method of the present invention.

Claims (1)

[Claims] 1. A treatment cylinder is filled with a finely divided reducing metal catalyst, the reducing metal catalyst filled in the treatment cylinder is activated by causing hydrogen to act, and the activated reducing metal catalyst is trifluorinated. By contacting the nitrogen-containing gas at room temperature,
A method for removing nitrogen trifluoride, which comprises decomposing nitrogen trifluoride.