Method for removing fluorine gas

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

Fluorine gas removal method

[0001] The present disclosure relates to a method for removing fluorine gas.

[0002] As semiconductor devices become smaller and more highly integrated, trace impurities introduced during the semiconductor manufacturing process can cause a decrease in the yield of semiconductor devices. Therefore, bromine pentafluoride (BrF), which is used as a semiconductor etching gas and chamber cleaning gas, has been developed. ５ ), iodine heptafluoride (IF ７ ), nitrogen trifluoride (NF ３ ), tungsten hexafluoride (WF ６ ), phosphorus trifluoride (PF ３ ), carbonyl fluoride (COF ２ High purity is also required for fluorine-containing compound gases such as fluorine-containing fluorine compounds.

[0003] Known methods for removing impurities from a fluorine-containing gas containing a 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).

[0004] JP 2004-039740 A JP 2017-141150 A

[0005] However, the method of Patent Document 1 has the problems that it 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 that it requires large-scale equipment. Furthermore, although the method of Patent Document 2 is effective for removing metal impurities, it does not disclose a method for removing fluorine gas.

[0006] An object of the present disclosure is to provide a method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas.

[0007] As a result of extensive research to solve the above problems, the present inventors have found 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.

[0008] In the method for removing fluorine gas according to the present disclosure, the fluorine gas contained in the fluorine-containing gas can be adsorbed onto 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 from the fluorine-containing gas containing the fluorine-containing compound gas and fluorine gas can be achieved. nF ２ +KX →K ＋ XF ｍ ― (1) where 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.

[0009] In order to solve the above-mentioned 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 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. [2] The method for removing fluorine gas according to [1], wherein the fluorine-containing compound gas contains at least one metal 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 metal 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 the temperature at which the fluorine-containing gas is brought into contact with the metal salt in the removing step 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.

[0010] According to the present disclosure, fluorine gas can be removed from a fluorine-containing compound gas that contains fluorine gas as an impurity.

[0011] 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.

[0012] An embodiment of the present disclosure will be described below. Note that this embodiment shows an example of the present disclosure, and the present disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modifications or improvements may also be included in the present disclosure.

[0013] The method for removing fluorine gas of the present embodiment is a method for removing the fluorine gas from a fluorine-containing gas containing 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.

[0014] An embodiment of a gas treatment device according to this embodiment will be described. The gas treatment device 1 includes a purification column 6 filled with a metal salt. The metal salt acts as an adsorbent for fluorine gas. The purification column 6 has an inlet 4 through which a fluorine-containing gas containing fluorine and a fluorine-containing compound gas is supplied, and an outlet 5 through which a purified gas obtained by subjecting the fluorine-containing gas to adsorption treatment with the adsorbent is discharged from the purification column 6 to the outside.

[0015] Furthermore, the gas treatment device 1 of this embodiment includes a fluorine-containing gas supply mechanism 2 that supplies a fluorine-containing gas, a fluorine-containing gas flow rate control device 7, an additive gas supply mechanism 3 that supplies an additive gas, and an additive gas flow rate control device 8. Furthermore, the outlet 5 of the purification column 6 is connected via a branch pipe to an analyzer 11 that analyzes the fluorine gas in the fluorine-containing gas. The fluorine-containing gas supply mechanism 2 is connected via a pipe to the fluorine-containing gas flow rate control device 7, and the fluorine-containing gas flow rate control device 7 is connected via a pipe to the purification column 6. The gas sent from the fluorine-containing gas supply mechanism 2 is supplied into the purification column 6 through the supply port 4, and a fluorine gas separation treatment using a metal salt may be performed in a temperature environment of 0°C to 120°C.

[0016] The gas supplied from the supply port 4 into the inside of the purifying column 6 may be a gas consisting only of 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 together, and the joined pipe may be connected to the supply port 4 of the purifying column 6. The gas other than fluorine gas and fluorine-containing compound gas is not particularly limited, but an inert gas may be mentioned, for example. By diluting the fluorine-containing gas with an inert gas, local heat generation can be easily suppressed, and the fluorine gas separation operation can be carried out more safely.

[0017] In such a 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 to form a mixed gas, which is then supplied from the supply port 4 into the purifying column 6.

[0018] The mixed gas supplied to the inside of the purifying column 6 may be brought into contact with an adsorbent in a temperature environment of 0° C. or higher and 120° C. or lower, and subjected to adsorption treatment by the adsorbent. That is, the fluorine gas contained in the fluorine-containing gas is adsorbed and separated by the adsorbent.

[0019] The purified gas obtained by the adsorption treatment with the adsorbent, i.e., the gas containing the fluorine-containing compound gas from which the fluorine gas has been separated, is discharged from the inside of the purification tower 6 to the outside through the outlet 5. In addition, a part of the purified gas is supplied to the analyzer 11 through a branch pipe connecting the outlet 5 and the analyzer 11.

[0020] The purified gas is analyzed in the analyzer 11. Specifically, quantitative or qualitative analysis of the fluorine gas contained in the purified gas is performed. The analyzer 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 analyzer. After the analysis, the purified gas is supplied to a detoxification device (not shown) through an analysis gas discharge pipe 9 connected to the analyzer 11.

[0021] 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 requiring complicated operations.

[0022] The method for removing fluorine gas according to this embodiment and the gas treatment device 1 according to this embodiment will be described in further detail below.

[0023] In the gas treatment device 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. ５ ), iodine heptafluoride (IF ７ ), nitrogen trifluoride (NF ３ ), tungsten hexafluoride (WF ６ ), phosphorus trifluoride (PF ３ ), and carbonyl fluoride (COF ２ ) and the like.

[0024] The material used for the purification column 6 is not particularly limited as long as it is corrosion-resistant 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, and Monel. Since the above-mentioned metal members may react with the fluorine-containing compound gas, it is preferable to perform a treatment such as passing a fluorine-containing compound gas or fluorine gas through them before use to form a passivation film on the surface. This is because it is 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.

[0025] 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 step, 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, separation of the fluorine gas can be easily achieved without using excessively large equipment.

[0026] The adsorbent for fluorine gas packed in the purifying 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 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 purifying column 6 may further be packed with an auxiliary agent that does not react at all or hardly reacts with the fluorine-containing compound gas and fluorine gas. Packing these auxiliary agents together with the metal salt may sometimes make it possible to suppress the heat generated when the metal salt and fluorine gas form a double salt. As the auxiliary agent, metal fluorides, metal oxides, etc. can be used, and lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), magnesium fluoride (MgF) are preferred because they are easy to obtain and handle. ２ ), calcium fluoride (CaF ２ ), aluminum fluoride (AlF ３ ), aluminum oxide (Al ２ O ３ ), and barium fluoride (BaF ２ It is preferable to use at least one selected from the group consisting of: The metal salt and the auxiliary agent are not particularly limited in shape, and may be, for example, pellets, foils, powders, granules, or lumps. Furthermore, a material containing a metal salt and an auxiliary agent as components, such as a pellet containing a mixture of a metal salt and an auxiliary agent, may be used as the filler.

[0027] 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. When the operating temperature is within the above temperature range, the removal rate of fluorine gas contained in the fluorine-containing gas is likely to be high. Furthermore, by diluting the fluorine-containing gas with an inert gas, local heat generation due to adsorption of fluorine gas is suppressed, and separation of fluorine gas can sometimes be carried out safely. The type of inert gas is not particularly limited, and examples include nitrogen gas, argon, and helium. Of these inert gases, nitrogen gas is preferred from the viewpoints of easy availability and low cost.

[0028] The content of fluorine gas contained in the fluorine-containing gas at outlet 5 of purification column 6, i.e., after the fluorine gas removal step, is preferably 100 volume ppm or less based on the total volume of the fluorine-containing compound gas and fluorine gas.

[0029] EXAMPLES The present disclosure will be explained in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to the examples.

[0030] Example 1 Adsorption treatment of a fluorine-containing gas was carried out using a gas treatment device having the same configuration as the gas treatment device 1 shown in FIG. 1 . The gas treatment device was equipped with a stainless steel purification column having an inner diameter of 1 inch and a length of 200 mm. This purification column was filled with 200 g of potassium bromide (manufactured by Kanto Chemical Co., Inc.) pressure-molded 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 purification column 6. Thereafter, the fluorine gas contained in the gas supplied to the purification column was adsorbed onto the 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 shown as "0.1%-F ２ / N ２Thereafter, 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). 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)

[0031]

[0032] Examples 2 to 25 Fluorine gas was removed and the concentration of fluorine gas contained in the resulting purified gas was measured 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. The results are shown in Table 1. In Example 25, gases other than fluorine gas contained in the resulting purified gas were also analyzed.

[0033] (Comparative Examples 1 and 2) Potassium fluoride and α-Al were used as metal salts. ２ O ３ The fluorine gas was removed in the same manner as in Example 1, except that the following were used:

[0034] From the results of Examples 1 and 2, it is clear that fluorine gas and BrF ５ Furthermore, when the fluorine gas concentration at the inlet of the purification column was 200 ppm by volume, the fluorine gas concentration at the outlet of the purification column was below the lower detection limit (5 ppm by volume) of the mass spectrometer.

[0035] From the results of Examples 3 and 4, it is clear that the fluorine-containing compound gas is ７ It was found that fluorine gas could be removed even in this case. In particular, when KI was used as the adsorbent, the fluorine gas removal effect was high. This suggests that KI exhibits a higher reactivity with fluorine gas than KBr.

[0036] The results of Examples 1 and 5 to 8 show that fluorine gas can be removed even when the temperature of the purifying column is set to 0° C. or higher and 120° C. or lower. In particular, when the temperature of the purifying column is 50° C., the most fluorine gas in the fluorine-containing gas is removed.

[0037] From the results of Examples 9 to 15, it was found that the adsorbents were KI, NaBr, LiBr, CsBr, and CaBr. ２ , MgBr ２ , and BaBr ２ It has been found that even in this case, fluorine gas in the fluorine-containing compound gas can be removed.

[0038] 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.

[0039] From the results of Examples 17 and 18, it was found that the adsorbent contained KF and α-Al as auxiliary agents. ２ O ３ It was found that fluorine gas could be removed even when

[0040] From the results of Examples 19 to 22, it was found that the fluorine-containing compound gas was WF ６ , N.F. ３ , P.F. ３ , COF ２ It was found that fluorine gas can be removed even in this case.

[0041] From the results of Examples 23 and 24, it is clear that the fluorine-containing compound gas is ５ , BrF ３ When the adsorbent KBr is ５ , BrF ３ Although the adsorption capacity of fluorine gas was reduced due to the adsorption of fluorine, it was found that fluorine gas could still be removed.

[0042] From the results of Example 25, it was found that the fluorine-containing compound gas was ClF ３ It was found that, although fluorine gas could be removed, a mixture of multiple halogen compounds was also obtained. This is because the fluorine-containing compound gas ClF ３ This is thought to be because multiple halogen compounds were produced when the reacted with the adsorbent KBr.

[0043] From the results of Comparative Examples 1 and 2, the adsorbent was KF only and α-Al ２ O ３ It was found that when only KF and α-Al were used, almost no fluorine gas could be removed. ２ O ３ This is thought to be because the compound does not react at all with fluorine gas, or reacts very little with fluorine gas.

[0044] According to the present disclosure, it is 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 for applications such as etching to accommodate miniaturization in the field of semiconductor manufacturing.

[0045] REFERENCE SIGNS LIST 1 Gas treatment device 2 Fluorine-containing gas supply mechanism 3 Added gas supply mechanism 4 Supply port 5 Discharge port 6 Purification column 7 Fluorine-containing gas flow rate control device 8 Added gas flow rate control device 9 Analysis gas discharge pipe 11 Analysis device

Claims

1. A method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas, comprising a removal 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 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.

3. 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.

4. 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.

5. A method for removing fluorine gas according to claim 1 or 2, 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. A 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 based on the total volume of the fluorine-containing compound gas and the fluorine gas.

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