WO2025134869A1 - Method for removing fluorine gas - Google Patents

Abstract

Provided is a method for removing fluorine gas from a fluorine-containing gas that comprises fluorine gas and a fluorine-containing compound gas. This method for removing fluorine gas from a fluorine-containing gas comprising fluorine gas and a fluorine-containing compound gas comprises a removal step for inducing contact between the fluorine-containing gas and at least one metal salt selected from the group consisting of metal chlorides, metal bromides, and metal iodides.

Description

How to remove fluorine gas

This disclosure relates to a method for removing fluorine gas.

Due to the miniaturization and high integration of semiconductor devices, trace impurities mixed in during the semiconductor manufacturing process are one of the causes of reduced yields of semiconductor devices. Therefore, high purity is also required for fluorine-containing compound gases such as bromine pentafluoride ( _BrF5 ), iodine heptafluoride ( _IF7 ), nitrogen trifluoride ( _NF3 ), tungsten hexafluoride ( _WF6 ), phosphorus trifluoride ( _PF3 ), and carbonyl fluoride ( _COF2 ) used as semiconductor etching gases and chamber cleaning gases.

　Known methods for removing impurities from a fluorine-containing gas that contains both fluorine-containing compound gas and impurities in order to obtain a high-purity fluorine-containing compound gas include a cryogenic purification method in which the fluorine-containing gas is cooled to partially liquefy it (Patent Document 1), and a method in which the fluorine-containing compound gas is brought into contact with a metal fluoride to adsorb and remove metal impurities (Patent Document 2).

JP 2004-039740 A JP 2017-141150 A

However, the method of Patent Document 1 cannot be applied when the difference in boiling point or melting point between the fluorine-containing compound gas contained in the fluorine-containing gas and the impurities to be removed is small, and has the problem of requiring large-scale equipment. Furthermore, while the method of Patent Document 2 is effective for removing metal impurities, it does not disclose a method for removing fluorine gas.

The objective of the present disclosure is to provide a method for removing fluorine gas from a fluorine-containing gas that contains fluorine gas and a fluorine-containing compound gas.

As a result of extensive research into solving the above problems, the inventors have discovered that fluorine gas contained in a fluorine-containing gas can be removed by contacting the fluorine-containing gas with at least one metal salt selected from the group consisting of metal chlorides, metal bromides, and metal iodides.

In the method for removing fluorine gas according to the present disclosure, the fluorine gas contained in the fluorine-containing gas can be adsorbed to a metal salt. That is, the fluorine gas reacts with the metal salt to form a double salt. As an example, the reaction between fluorine gas and potassium halide is shown in formula (1). On the other hand, the fluorine-containing compound gas hardly adsorbs or reacts with the metal salt, so that separation of the fluorine gas in the fluorine-containing gas containing the fluorine-containing compound gas and the fluorine gas can be achieved.
nF ₂ +KX→K ⁺ XF _m ^- (1)
Here, X is at least one selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I), and n and m are arbitrary coefficients.

In order to solve the above problems, one aspect of the present disclosure is as follows [1] to [6].
[1] A method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas, comprising the steps of:
A method for removing fluorine gas, comprising the step of contacting the fluorine-containing gas with at least one metal salt selected from the group consisting of metal chlorides, metal bromides and metal iodides to remove the fluorine gas.
[2] The method for removing fluorine gas according to [1], wherein the fluorine-containing compound gas contains at least one selected from the group consisting of bromine pentafluoride, iodine heptafluoride, nitrogen trifluoride, tungsten hexafluoride, phosphorus trifluoride, and carbonyl fluoride.
[3] The method for removing fluorine gas according to [1] or [2], wherein the metal species of the metal salt is at least one selected from the group consisting of alkali metals and alkaline earth metals.
[4] The method for removing fluorine gas according to [3], wherein the metal species of the metal salt is at least one selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, cesium, and barium.
[5] The method for removing fluorine gas according to any one of [1] to [4], wherein in the removing step, the temperature at which the fluorine-containing gas is brought into contact with the metal salt is 0° C. or higher and 120° C. or lower.
[6] The method for removing fluorine gas according to any one of [1] to [5], wherein the content of fluorine gas contained in the fluorine-containing gas after the removing step is 100 ppm by volume or less based on the total volume of the fluorine-containing compound gas and the fluorine gas.

According to the present disclosure, fluorine gas can be removed from a fluorine-containing compound gas that contains fluorine gas as an impurity.

FIG. 1 is a schematic diagram showing an example of a gas treatment device for removing fluorine gas according to an embodiment of the present disclosure.

One embodiment of the present disclosure is described below. Note that this embodiment is merely an example of the present disclosure, and the present disclosure is not limited to this embodiment. In addition, various modifications and improvements can be made to this embodiment, and forms incorporating such modifications or improvements may also be included in the present disclosure.

The method for removing fluorine gas in this embodiment is a method for removing the fluorine gas from a fluorine-containing gas that contains fluorine gas and a fluorine-containing compound gas, and includes a step of contacting the fluorine-containing gas with at least one metal salt selected from the group consisting of metal chlorides, metal bromides, and metal iodides to remove the fluorine gas.

One embodiment of the gas processing device according to this embodiment will be described. The gas processing device 1 is equipped with a purification tower 6 filled with metal salts. The metal salts act as adsorbents for fluorine gas. This purification tower 6 has a supply port 4 through which a fluorine-containing gas containing fluorine and a fluorine-containing compound gas is supplied, and an exhaust port 5 through which the purified gas obtained by subjecting the fluorine-containing gas to an adsorption treatment with an adsorbent is exhausted from inside the purification tower 6 to the outside.

Furthermore, the gas treatment device 1 of this embodiment includes a fluorine-containing gas supply mechanism 2 for supplying a fluorine-containing gas, a fluorine-containing gas flow rate control device 7, an additive gas supply mechanism 3 for supplying an additive gas, and an additive gas flow rate control device 8. Furthermore, the outlet 5 of the purification column 6 is connected by a branch pipe to an analysis device 11 for analyzing the fluorine gas in the fluorine-containing gas.
The fluorine-containing gas supply mechanism 2 is connected to a fluorine-containing gas flow rate control device 7 through a pipe, and the fluorine-containing gas flow rate control device 7 is connected to the purification column 6 through a pipe. The gas sent from the fluorine-containing gas supply mechanism 2 is supplied to the inside of the purification column 6 through a supply port 4, and a fluorine gas separation process using a metal salt may be performed in a temperature environment of 0° C. or higher and 120° C. or lower.

The gas supplied from the supply port 4 to the inside of the purification tower 6 may be a gas consisting of only fluorine gas and fluorine-containing compound gas, or may contain other gases. That is, as shown in FIG. 1, a pipe extending from the fluorine-containing gas supply mechanism 2 and a pipe extending from the additive gas supply mechanism 3 may be joined, and the joined pipe may be connected to the supply port 4 of the purification tower 6. Gases other than fluorine gas and fluorine-containing compound gas are not particularly limited, but may include, for example, inert gas. By diluting the fluorine-containing gas with an inert gas, localized heat generation can be easily suppressed, making it easier to perform the fluorine gas separation operation safely.

In this configuration, the fluorine-containing gas delivered from the fluorine-containing gas supply mechanism 2 and the inert gas delivered from the additive gas supply mechanism 3 are mixed in the piping where they join together to form a mixed gas, which is then supplied to the inside of the purification column 6 from the supply port 4.

The mixed gas supplied to the inside of the purification tower 6 may come into contact with an adsorbent in a temperature environment of 0°C or higher and 120°C or lower, and may be subjected to an adsorption process by the adsorbent. In other words, the fluorine gas contained in the fluorine-containing gas is adsorbed and separated by the adsorbent.

The purified gas that has been subjected to the adsorption process using the adsorbent, i.e., the gas containing the fluorine-containing compound gas from which the fluorine gas has been separated, is discharged from inside the purification tower 6 to the outside through the exhaust port 5. In addition, a portion of the purified gas is supplied to the analysis device 11 through a branch pipe that connects the exhaust port 5 to the analysis device 11.

The purified gas is analyzed in the analysis device 11. Specifically, quantitative or qualitative analysis of the fluorine gas contained in the purified gas is performed. The analysis device is not particularly limited as long as it is capable of performing qualitative or quantitative analysis of the fluorine gas contained in the purified gas, and for example, an ultraviolet-visible spectrophotometer, a Raman spectrophotometer, a mass spectrometer, or the like can be used as the analysis device.
After the analysis, the purified gas is passed through an analysis gas discharge pipe 9 connected to an analysis device 11 and supplied to a detoxification device (not shown).

In this way, by using the gas treatment device 1 of this embodiment, fluorine gas contained in a fluorine-containing gas can be efficiently removed under mild conditions without the need for complicated operations.

The fluorine gas removal method and the gas treatment device 1 of this embodiment are described in further detail below.

In the gas processing apparatus 1 of this embodiment, the fluorine-containing compound gas contained in the fluorine-containing gas supplied from the fluorine-containing gas supply mechanism 2 is not particularly limited as long as it is a compound gas containing fluorine atoms, and may be at least one selected from the group consisting of bromine pentafluoride (BrF ₅ ), iodine heptafluoride (IF ₇ ), nitrogen trifluoride (NF ₃ ), tungsten hexafluoride (WF ₆ ), phosphorus trifluoride (PF ₃ ), carbonyl fluoride (COF ₂ ), and the like.

There are no particular limitations on the material used for the purification column 6, so long as it has corrosion resistance to the fluorine-containing compound gas and fluorine gas used. For example, metals such as nickel, nickel-based alloys, aluminum, stainless steel, and platinum, ceramics such as alumina, and fluororesins can be used for the parts that come into contact with the fluorine-containing compound gas and fluorine gas.
Examples of nickel-based alloys include Inconel, Hastelloy, Monel, etc. In addition, since the members made of the above-mentioned metals may react with a fluorine-containing compound gas, it is preferable to perform a treatment such as passing a fluorine-containing compound gas or fluorine gas through the member before use to form a passivation film on the surface. This is because it becomes easier to suppress the generation of impurities.
Examples of fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), Viton, and Kalrez.

The content of fluorine gas contained in the fluorine-containing gas at the supply port 4 of the purification column 6, i.e., before the fluorine gas removal process, may be 10 ppm by volume or more and less than 3% by volume, 100 ppm by volume or more and 2% by volume or less, or 200 ppm by volume or more and 1% by volume or less. If the amount of fluorine gas is within the above range, it is easy to achieve separation of fluorine gas without using excessively large equipment.

The adsorbent for fluorine gas packed in the purification column 6 is at least one metal salt selected from the group consisting of metal chlorides, metal bromides, and metal iodides. The metal salt may be a solid. The metal species of the metal salt may be at least one selected from the group consisting of alkali metals and alkaline earth metals, and may be at least one selected from the group consisting of lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), cesium (Cs), and barium (Ba) because they are easily available.
In addition to the metal salt, the purification column 6 may be further filled with an auxiliary agent that does not react at all or hardly reacts with the fluorine-containing compound gas and the fluorine gas. By filling these auxiliary agents together with the metal salt, it may be possible to suppress the heat generated when the metal salt and the fluorine gas form a double salt. As the auxiliary agent, a metal fluoride or a metal oxide can be used, and it is preferable to use at least one selected from the group consisting of lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), aluminum fluoride (AlF ₃ ), aluminum oxide (Al ₂ O ₃ ), and barium fluoride (BaF ₂ ) because they are easily available and easy to handle.
The shape of the metal salt and the auxiliary is not particularly limited and may be, for example, pellets, foils, powders, granules, blocks, etc. Furthermore, a material containing a metal salt and an auxiliary as components, such as a pellet containing a mixture of a metal salt and an auxiliary, may be used as the filler.

In the purification column 6, the temperature at which the fluorine-containing gas is brought into contact with the metal salt may be 0°C or higher and 120°C or lower, 10°C or higher and 100°C or lower, or 20°C or higher and 80°C or lower. The metal salt is a solid. If the operating temperature is within the above temperature range, the removal rate of the fluorine gas contained in the fluorine-containing gas is likely to be high. Furthermore, by diluting the fluorine-containing gas with an inert gas, localized heat generation due to adsorption of the fluorine gas is suppressed, and separation of the fluorine gas may be safely performed. The type of inert gas is not particularly limited, but examples include nitrogen gas, argon, and helium. Of these inert gases, nitrogen gas is preferred from the viewpoints of ease of availability and low cost.

The content of fluorine gas contained in the fluorine-containing gas at the outlet 5 of the purification column 6, i.e., after the fluorine gas removal process, is preferably 100 ppm by volume or less relative to the total volume of the fluorine-containing compound gas and the fluorine gas.

The following examples and comparative examples will be used to explain the present disclosure in more detail, but the present disclosure is not limited to the examples.

[Example 1]
Adsorption treatment of a fluorine-containing gas was carried out using a gas treatment device having a configuration similar to that of the gas treatment device 1 shown in Fig. 1. The gas treatment device was equipped with a stainless steel purification tower having an inner diameter of 1 inch and a length of 200 mm. This purification tower was filled with 200 g of potassium bromide (manufactured by Kanto Chemical Co., Ltd.) pressed into pellets having a diameter of 3 mm and a height of 5 mm as an adsorbent.
Next, a fluorine-containing compound gas at a flow rate of 10 mL/min and an additive gas at a flow rate of 20 mL/min were mixed and supplied to the purification column 6. Thereafter, the fluorine gas contained in the gas supplied to the purification column was adsorbed by an adsorbent at 50° C. The fluorine-containing compound gas was bromine pentafluoride. The additive gas was a gas composed of fluorine gas and nitrogen gas, and the concentration of fluorine gas in the additive gas was 0.1% by volume. In Table 1, the composition of the additive gas is represented as "0.1%-F ₂ /N ₂ ".
Thereafter, a portion of the purified gas discharged from outlet 5 of purification column 6 was extracted, and the concentration of fluorine gas contained in the purified gas was measured using an inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Hiden Analytical Co., Ltd.). The results are shown in Table 1.
The fluorine gas concentration was calculated using the following formula.
Fluorine gas concentration (ppm by volume) = Fluorine gas flow rate / (Fluorine gas flow rate + Fluorine-containing compound gas flow rate)

(Examples 2 to 25)
Fluorine gas was removed in the same manner as in Example 1, except that the type and flow rate of the fluorine-containing compound gas, the type, composition and flow rate of the added gas, the adsorbent, and the purification column temperature were changed as shown in Table 1, and the fluorine gas concentration contained in the obtained purified gas was measured. The results are shown in Table 1.
In addition, for Example 25, the gases other than fluorine gas contained in the obtained refined gas were also analyzed.

(Comparative Examples 1 and 2)
Fluorine gas was removed in the same manner as in Example 1, except that potassium fluoride and α-Al ₂ O ₃ were used as the metal salts, and the fluorine gas concentration in the resulting purified gas was measured. The results are shown in Table 1.

From the results of Examples 1 and 2, it was found that fluorine gas could be removed from a fluorine-containing gas containing fluorine gas and _BrF5 . In addition, when the fluorine gas concentration at the supply port of the purification column was 200 ppm by volume, the fluorine gas concentration at the outlet of the purification column was less than the lower detection limit (5 ppm by volume) of the mass spectrometer.

From the results of Examples 3 and 4, it was found that fluorine gas could be removed even when the fluorine-containing compound gas was _IF7 . In particular, when KI was used as the adsorbent, the effect of removing fluorine gas was high. This suggests that KI shows higher reactivity with fluorine gas than KBr.

The results of Examples 1 and 5 to 8 show that fluorine gas can be removed even when the temperature of the purification tower is between 0°C and 120°C. In particular, the most fluorine gas was removed from the fluorine-containing gas when the temperature of the purification tower was 50°C.

From the results of Examples 9 to 15, it was found that even when the adsorbent was KI, NaBr, LiBr, CsBr, CaBr ₂ , MgBr ₂ , or BaBr ₂ , fluorine gas in a fluorine-containing compound gas could be removed.

The results of Example 16 show that fluorine gas can be removed even when the fluorine gas concentration in the fluorine-containing gas is 10,000 ppm by volume.

The results of Examples 17 and 18 show that fluorine gas can be removed even when KF and α-Al ₂ O ₃ are added to the adsorbent as auxiliary agents.

From the results of Examples 19 to 22, it was found that fluorine gas could be removed even when the fluorine-containing compound gas was WF ₆ , NF ₃ , PF ₃ or COF ₂ .

From the results of Examples 23 and 24, it was found that when the fluorine-containing compound gas was IF ₅ or BrF ₃ , IF ₅ and BrF ₃ were adsorbed by the adsorbent KBr, and the adsorption capacity of fluorine gas was reduced, but fluorine gas could still be removed.

From the results of Example 25, it was found that when the fluorine-containing compound gas was _ClF3 , fluorine gas could be removed, but a mixture of multiple halogen compounds was also obtained. This is considered to be because multiple halogen compounds were generated by the reaction of the fluorine-containing compound gas _ClF3 with the adsorbent KBr.

From the results of Comparative Examples 1 and 2, it was found that when the adsorbent consisted of only KF or only α-Al ₂ O ₃ , almost no fluorine gas was removed. This is considered to be because KF and α-Al ₂ O ₃ did not react at all with fluorine gas, or reacted almost only slightly with fluorine gas.

The present disclosure makes it possible to easily remove fluorine gas contained in a fluorine-containing gas, and to provide a high-purity fluorine-containing compound gas that can be used in applications such as etching to accommodate miniaturization in the semiconductor manufacturing field.

Reference Signs List 1 Gas treatment device 2 Fluorine-containing gas supply mechanism 3 Additive gas supply mechanism 4 Supply port 5 Exhaust port 6 Purification column 7 Fluorine-containing gas flow rate control device 8 Additive gas flow rate control device 9 Analysis gas exhaust pipe 11 Analysis device

Claims (6)

A method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas, comprising the steps of:
A method for removing fluorine gas, comprising the step of contacting the fluorine-containing gas with at least one metal salt selected from the group consisting of metal chlorides, metal bromides and metal iodides to remove the fluorine gas. The method for removing fluorine gas according to claim 1, wherein the fluorine-containing compound gas contains at least one selected from the group consisting of bromine pentafluoride, iodine heptafluoride, nitrogen trifluoride, tungsten hexafluoride, phosphorus trifluoride, and carbonyl fluoride. The method for removing fluorine gas according to claim 1 or 2, wherein the metal species of the metal salt is at least one selected from the group consisting of alkali metals and alkaline earth metals. The method for removing fluorine gas according to claim 3, wherein the metal species of the metal salt is at least one selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, cesium, and barium. The method for removing fluorine gas according to claim 1 or 2, wherein in the removal step, the temperature at which the fluorine-containing gas is brought into contact with the metal salt is 0°C or higher and 120°C or lower. The method for removing fluorine gas according to claim 1 or 2, wherein the content of fluorine gas contained in the fluorine-containing gas after the removal step is 100 ppm by volume or less with respect to the total volume of the fluorine-containing compound gas and the fluorine gas.

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