JPH0679138A - Method for pretreating nf3 gas - Google Patents

Abstract

PURPOSE:To decompose and remove by chemical reaction hydrogen bromide, hydrogen chloride, bromine and chlorine which are coexistent in a process for removing NF3. CONSTITUTION:A hydrogen bromide removal agent is composed of at least one chemical selected from calcium oxide and magnesium oxide. In addition, a removal process consisting of a combination of more than one type selected from among calcium hydroxide, sodium hydroxide, potassium hydroxide and magnesium hydroxide and more than one type selected from zeolite and silica gel is provided in the prestage of a process for removing NF3. In addition, a hydrogen bromide removal part detects the inflow of hydrogen bromide by a temperature rise. Further, it is possible to detect the life of a removal agent of hydrogen bromide by arranging a substance which discolors through chemical reaction with hydrogen bromide in a window part provided on part of the hydrogen bromide removal part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for safely removing NF ₃ gas in a system that simultaneously handles NF ₃ gas and hydrogen bromide.

[0002]

2. Description of the Related Art NF ₃ attracts attention as a rocket fuel in the aerospace field, and in recent years as a dry cleaning agent for a CVD apparatus or a dry etching agent in an LSI manufacturing process in the semiconductor industry field. . Especially as a dry etching agent, LSI is more suitable than perfluorocarbon type etching agents such as CF _4.
It has been increasingly used because it has the advantage of being extremely low in pollution.

However, NF ₃ is extremely stable in the atmosphere and is only slightly soluble in water. TLV = 10 p
Since this is a pm toxic gas, it is always necessary to remove the unused gas when it is used.

On the other hand, in a CVD apparatus, a method for safely removing harm together with at least one component (hereinafter referred to as "hydrogen bromide, etc.") of hydrogen bromide, hydrogen chloride, bromine and chlorine which are often used at the same time is required. ing.

NF ₃ is a very stable gas near room temperature, does not react with chemical substances such as acids and alkalis, is hardly absorbed by water, and has no suitable adsorbent. Can not be removed by a traditional method. But NF ₃
Starts to decompose into N ₂ and active F atoms at 180 ° C or higher (Equation 1), and has a sufficiently large decomposition rate at 400 ° C or higher.

2NF ₃ → N ₂ + 6F (Equation 1) That is, an effective method for treating NF ₃ is 400 ° C.
NF ₃ is decomposed at the above high temperature and the generated F atoms are reacted with an appropriate substance. Most of the NF ₃ detoxification methods that have been developed for industrial use are based on this principle. ing. For example, as a substance that reacts with F, Si,
Methods that use volatile fluorides such as W and Mo (Japanese Patent Publication No. 63-48570) and carbon sources that generate CF ₄ gas such as activated carbon (Japanese Patent Publication No. 2-30731) is there.

By the way, in the cleaning and etching processes in semiconductor manufacturing, which is the main use of NF ₃ ,
F ₃ is often used a mixture of hydrogen bromide in, but gases such as hydrogen bromide would significantly corrode the metal material in the high temperature reactor harm min releasing NF _3. As a method for removing hydrogen bromide and the like in advance before the NF ₃ removal reaction to remove such a danger, no suitable method has been proposed so far.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, in which a chemical agent for removing hydrogen bromide or the like is arranged in front of an NF ₃ abatement device having a high temperature part. It is intended to provide a method capable of safely removing NF ₃ , and further to provide a method capable of controlling the life of a chemical agent for removing hydrogen bromide and the like.

[0009] The present invention, prior to the step of abating NF ₃ gas, hydrogen bromide coexisting with NF ₃ gas, hydrogen chloride, bromine, and wherein the reaction is removed using a chlorine removal agent In the pretreatment method for NF ₃ gas, the removal agent comprises at least one selected from calcium oxide and magnesium oxide.
A method for pretreating NF ₃ gas, which comprises a combination of one or more selected from calcium hydroxide, potassium hydroxide, sodium hydroxide and magnesium hydroxide and one or more selected from zeolite and silica gel. The window provided is provided with a method for detecting the life of the removed chemical by arranging a substance that changes color by acting on the component to be removed, and also detects the life of the removed chemical by detecting the temperature rise of the removal section. The method is a pretreatment method for NF ₃ gas.

As chemicals for removing hydrogen bromide and the like, calcium hydroxide, potassium hydroxide, sodium hydroxide, magnesium hydroxide and the like are generally known as alkaline chemicals. Moisture, which is a reaction product with, is very unsatisfactory for the NF ₃ abatement device in the subsequent stage. Because this water is F generated by decomposition of NF _3.
This is because the action of the atoms significantly corrodes the metal of the high temperature reactor material.

As a result of intensive investigations by the present inventors on agents for removing hydrogen bromide and the like, it has been found that at least one agent selected from calcium oxide and magnesium oxide is very useful for this purpose. The present invention has been found out. That is, by disposing at least one or more agents selected from calcium oxide and magnesium oxide in the preceding stage of the NF ₃ abatement device, hydrogen bromide and the like are reacted and fixed in the form of calcium salt or magnesium salt, and at the same time, Since the water generated by the reaction is absorbed by the drug,
It has been found that the pretreatment of hydrogen bromide or the like can be performed without any adverse effect on the NF ₃ abatement device in the latter stage.

Further, in the case of calcium hydroxide, potassium hydroxide, sodium hydroxide and magnesium hydroxide, which produce water by the reaction, the effect of water can be eliminated by using them in combination with zeolite or silica gel which is a dehydrating agent. It was found that it can be sufficiently used as a removing agent for That is, it was found that pretreatment of hydrogen bromide or the like can be carried out by contacting gases in the order of calcium hydroxide or the like in the first stage and zeolite or the like in the second stage without adversely affecting the NF ₃ abatement device. .

Further, if hydrogen bromide or the like is continued to flow into the NF ₃ abatement line, it can be treated by the agent for removing hydrogen bromide or the like provided by the present invention, but the capability of the agent is limited. Since the ability to remove hydrogen bromide and the like will eventually be lost, a mechanism is necessary to detect the life of the chemical and inform the operator.

The present invention also provides a method for the detection mechanism. In other words, if the ability of a chemical agent for removing hydrogen bromide, etc. is lost, hydrogen bromide, etc. will flow out to the downstream side, so take measures by analyzing this hydrogen bromide, etc. You can However, in this case, if the outlet gas of the removal unit for hydrogen bromide, etc. is analyzed, it will occur at the same time that hydrogen bromide, etc. will be detected and that hydrogen bromide, etc. will flow into the NF ₃ abatement reaction unit. Can't deal with. Even if the chemicals on the upstream side of the removal unit for hydrogen bromide lose their ability, the remaining chemicals on the downstream side still retain their ability. The present invention also provides a method of arranging a reagent that changes color due to the reaction with the above in a portion where hydrogen bromide or the like is removed so that it can be observed from the outside. The discoloring agent may be selected according to the target component to be removed, and examples thereof include methyl orange, cresol red, benzeneazodiphenylamine, orthotolidine and the like. The color-changing reagent can be used in the form of being attached to a carrier such as silica gel, porous alumina, or filter paper.

In addition, a method of detecting with an electric signal is also required for unmanned / automated process, and the present invention also provides a method therefor. That is, calcium oxide, magnesium oxide, calcium hydroxide, potassium hydroxide, sodium hydroxide, magnesium hydroxide all generate heat due to reaction with hydrogen bromide, etc. Can be detected. For example, if a container with a temperature sensor at the bottom is filled with these removal agents and a gas containing hydrogen bromide is introduced from above, it is necessary to know that the removal agent on the upstream side of the sensor has breached due to the temperature rise. You can Signals captured by this temperature sensor can be used to activate alarm devices such as lamps and buzzers to promptly notify the operator of a dangerous condition, and the original valve for hydrogen bromide can be automatically closed. It is also possible to eliminate the cause of the dangerous condition. In the above-mentioned mechanism for detecting the inflow of hydrogen bromide or the like into the NF ₃ abatement line, it is practical to set the temperature level at which the alarm is output to a value obtained by adding the error width to the temperature fluctuation width in the normal state. Target.

The positions of the discoloration indicating device and the temperature rise detecting device for detecting the lifespan of the removed chemicals are determined by how much margin of the chemicals should be secured as a backup after detecting these signals. It may be designed as appropriate according to the convenience of the system.

[0017]

EXAMPLES The present invention will be described below with reference to specific examples. Example 1 A gas inlet / outlet is provided at both ends, and a gas is placed every 100 mm in the longitudinal direction.
70 mm inside diameter, 500 m long with a thermocouple inside
A stainless steel container of m was used as a column for removing hydrogen bromide and the like, and a gas sampling stand was provided at the outlet. 2 Kg of CaO (diameter 3 to 5 mm) was packed in the removal column and fixed vertically, and at room temperature, NF ₃ = 10% and the balance gas of N ₂ were flowed at a flow rate of 1000 cc / min from the upper port, and at the outlet of the removal column. When the gas was analyzed, NF ₃ = 10%, which was unchanged. There was also no change in the temperature inside the column.

Then, NF ₃ = 10%, HBr = 10%,
When the mixed gas of the balance N ₂ was flowed at a flow rate of 1000 cc / min and the outlet gas was analyzed, NF ₃ = 11%, HBr
<1 ppm (below the lower limit of detection) and H ₂ O <3 μg / l. The temperature inside was highest near the gas inlet and reached 54 ° C (20 ° C before the start of the experiment).

When the integrated value of the supplied HBr reaches 200 g, the composition of the outlet gas is NF ₃ = 11%, HBr <1.
ppm (below the lower limit of detection), H ₂ O <3 μg / l. The internal temperature reached 50 ° C, which was the highest near the gas outlet.

When the integrated value of the supplied HBr reaches 220 g, the composition of the outlet gas is NF ₃ = 11%, HBr <1.
ppm (below the lower limit of detection), H ₂ O = 20 μg / l. When the integrated value of the supplied HBr reached 260 g, the composition of the outlet gas was NF ₃ = 11%, HBr = 10 pp.
m, H ₂ O = 150 μg / l.

Example 2 The same experiment as in Example 1 was carried out except that a mixed gas of NF ₃ = 10%, HCl = 10% and the balance N ₂ was used, and the outlet gas was analyzed. NF ₃ = 11%, HCl <1 ppm (below the lower limit of detection) and H ₂ O <3 μg / l. The highest internal temperature reached 58 ° C near the gas inlet (20 ° C before the start of the experiment).

When the integrated value of the supplied HCl reached 70 g, the composition of the outlet gas was NF ₃ = 11%, HCl <1 p
pm (below the lower limit of detection), H ₂ O <3 μg / l.
The internal temperature reached 53 ° C, which was the highest near the gas outlet.

When the integrated value of the supplied HCl reached 80 g, the composition of the outlet gas was NF ₃ = 11%, HCl <1 p
pm (below the lower limit of detection), H ₂ O = 30 μg / l. When the integrated value of the supplied HCl reached 100 g, the composition of the outlet gas was NF ₃ = 11%, HCl = 20 pp.
m, H ₂ O = 200 μg / l.

Example 3 The same experiment as in Example 1 was carried out except that the mixed gas was NF ₃ = 10%, Br ₂ = 10%, and the balance was N ₂ , and the outlet gas was analyzed. NF ₃ = 11%, Br ₂ <1 ppm (below the lower limit of detection) and H ₂ O <3 μg / l. The internal temperature reached 47 ° C, the highest near the gas inlet (20 ° C before the start of the experiment).

When the integrated value of Br ₂ supplied reached 70 g, the composition of the outlet gas was NF ₃ = 11%, Br ₂ <1 p.
pm (below the lower limit of detection), H ₂ O <3 μg / l.
The internal temperature reached 45 ° C, which was the highest near the gas outlet.

When the integrated value of Br ₂ supplied reached 80 g, the composition of the outlet gas was NF ₃ = 11% and Br ₂ = 50.
ppm, H ₂ O <3 μg / l. Example 4 The same experiment as in Example 1 was carried out except that a mixed gas of NF ₃ = 10%, Cl ₂ = 10% and the balance of N ₂ was used, and the outlet gas was analyzed. NF ₃ = 11%, Cl ₂ < It was 1 ppm (below the lower limit of detection) and H ₂ O <3 μg / l. The highest internal temperature reached 58 ° C near the gas inlet (20 ° C before the start of the experiment).

At the time when the integrated value of the supplied Cl ₂ reached 30 g, the composition of the outlet gas was NF ₃ = 11%, Cl ₂ <1 p.
pm (below the lower limit of detection), H ₂ O <3 μg / l.
The internal temperature reached 53 ° C, which was the highest near the gas outlet.

When the integrated value of the supplied Cl ₂ reached 40 g, the composition of the outlet gas was NF ₃ = 11%, Cl ₂ = 40.
ppm, H ₂ O <3 μg / l. Example 5 A window made of quartz was provided near the gas outlet of the column of Example 1, and particles (yellow) in which benzeneazodiphenylamine was supported on silica gel were arranged inside the window. Other conditions were tested in the same manner as in Example 1, and at the time when the integrated value of the supplied HBr reached 200 g, the color of the particles changed from yellow to red, the drug broke through, and HBr was detected. I showed that.

Example 6 The same experiment as in Example 1 was carried out except that the mixed gas of the supply gas NF ₃ = 10%, HBr = 5%, and the balance N ₂ was carried out, and the integrated value of the supplied HBr was 200 g. The temperature inside the column reached a maximum of 41 ° C near the gas outlet (initial 20
It was found that the total amount of the removed chemicals passed through.

Example 7 The same experiment as in Example 1 was conducted except that 2 kg of MgO (diameter: 3 to 5 mm) was filled instead of CaO. Analysis of the outlet gas showed that NF ₃ = 11%, HBr <1 ppm
(Below the lower limit of detection), H ₂ O <3 μg / l.

Example 8 1% Ca (OH) ₂ (diameter 3-5 mm) was used instead of CaO.
The same experiment as in Example 1 was conducted except that 1 kg of Kg and 1 kg of zeolite (3A) were charged. When the outlet gas was analyzed, NF ₃ = 11%, HBr <1 ppm (below the lower limit of detection), and H ₂ O <3 μg / l.

Example 9 1% of Mg (OH) ₂ (diameter 3-5 mm) was used instead of CaO.
The same experiment as in Example 1 was conducted except that 1 kg of Kg and 1 kg of zeolite (3A) were charged. When the outlet gas was analyzed, NF ₃ = 11%, HBr <1 ppm (below the lower limit of detection), and H ₂ O <3 μg / l.

Example 10 NF ₃ removal consisting of a Ni reactor (heated to 600 ° C. with a Ni) in which a removal column having an inner diameter of 400 mm and a length of 960 mm was filled with 75 kg of CaO and metal silicon was filled in the downstream side of the outlet pipe. Combined harm device.

From the removal column inlet, NF ₃ = 1%, HBr
= 1% and the balance N ₂ mixed gas was flowed at a flow rate of 10 l / min, and the outlet gas of the NF ₃ abatement device was analyzed.
_{3 <10ppm, SiF 4 = 0.75} %, HBr <1p
pm (below the lower limit of detection), H ₂ O <3 μg / l.
After continuously treating for 120 hours, the NF ₃ abatement device was disassembled and the inside of the reactor was observed, and no corrosion occurred.

Comparative Example ₂ Ca (OH) ₂ (diameter 3-5 mm) was used instead of CaO 2.
The same experiment as in Example 1 was performed except that Kg was charged. Analysis of the outlet gas showed that NF ₃ = 11%, HBr <1
ppm (below the lower limit of detection), H ₂ O = 40 mg / l, removal of HBr was recognized, but H ₂ O was detected.

[0036]

Effect of the Invention] The present invention, NF ₃ it is possible to pre-preprocessing removes the hydrogen bromide or the like to coexist with NF ₃ gas
Safe maintenance management of gas abatement equipment can be performed, and NF
₃ Gas can be removed more safely.

Claims (5)

[Claims] 1. Prior to the step of removing NF ₃ gas, N
N characterized by reacting and removing hydrogen bromide, hydrogen chloride, bromine and chlorine coexisting with F ₃ gas using a removing agent
Pretreatment method for F ₃ gas. 2. The pretreatment method for NF ₃ gas according to claim 1, which comprises at least one selected from calcium oxide and magnesium oxide as a removing agent. 3. The removing agent according to claim 1, which comprises a combination of one or more selected from calcium hydroxide, potassium hydroxide, sodium hydroxide and magnesium hydroxide and one or more selected from zeolite and silica gel. Pretreatment method for NF ₃ gas. 4. The pretreatment of NF ₃ gas according to claim 1, further comprising a method for detecting the life of the removed chemical by disposing a substance that changes color by acting on a component to be removed in a window provided in the removing section. Method. 5. The NF ₃ gas pretreatment method according to claim 1, further comprising a method of detecting the life of the removed chemical by detecting an increase in the temperature of the removal section.