Method for removing fluorine gas

Abstract

A method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas is provided. A method for removing fluorine gas from a fluorine-containing gas containing fluorine gas and a fluorine-containing compound gas includes a removal step in which the fluorine-containing gas is brought into contact with at least one metal salt selected from the group consisting of metal chlorides, metal bromides, and metal iodides.

Description

TECHNICAL FIELD

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

[0002] With miniaturization and high integration of semiconductor devices, trace impurities mixed in a semiconductor manufacturing process become one of the causes of reduction in yield of semiconductor devices. Therefore, high-purity is also required for fluorine compound gases such as bromine pentafluoride (BrF5), iodine heptafluoride (IF7), nitrogen trifluoride (NF3), tungsten hexafluoride (WF6), phosphorus trifluoride (PF3), carbonyl fluoride (COF2), and the like, which are used as semiconductor etching gases, chamber cleaning gases.

[0003] In order to obtain a high-purity fluorine compound gas, as a method for removing impurities from a fluorine-containing gas containing a fluorine compound gas and impurities, a cryogenic purification method in which the fluorine-containing gas is cooled to liquefy a part of it (Patent Literature 1), and a method in which a fluorine compound gas is brought into contact with a metal fluoride to adsorb and remove metal impurities (Patent Literature 2) are known.

[0004] Prior Art Documents

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2004-039740

[0006] Patent Literature 2: Japanese Patent Application Publication No. 2017-141150 SUMMARY

[0007] However, the method of Patent Literature 1 cannot be applied not only to a case where the difference between the boiling point or melting point of the fluorine compound gas contained in the fluorine-containing gas and the impurities to be removed is small, but also to a case where a large-scale apparatus is required. In addition, although the method of Patent Literature 2 is an effective method in the case of removing metal impurities, a method for removing fluorine gas is not described.

[0008] The present disclosure relates to a method for removing fluorine gas.

[0009] The present inventors have intensively studied to solve the above problem, and as a result, have found that by bringing a fluorine-containing gas into contact with at least one metal salt selected from the group consisting of a chloride of a metal, a bromide of a metal, and an iodide of a metal, fluorine gas contained in the fluorine-containing gas can be removed.

[0010] In the method for removing fluorine gas of the present disclosure, fluorine gas contained in a fluorine-containing gas can be adsorbed to a metal salt. That is, fluorine gas reacts with the metal salt to form a double salt. For example, the reaction of fluorine gas and potassium halide is shown in formula (1). On the other hand, a fluorine compound gas hardly adsorbs or reacts with the metal salt, and thus separation of fluorine gas from a fluorine-containing gas containing a fluorine compound gas and fluorine gas can be achieved.

[0011] nF2+KX→K + XF m ― (1)

[0012] wherein X is at least one selected from chlorine (Cl), bromine (Br), and iodine (I), and n and m are arbitrary coefficients.

[0013] To solve the above problem, one embodiment of the present disclosure is as shown in [1] to [6] below.

[0014] [1] A method for removing fluorine gas, which is a method for removing fluorine gas from fluorine gas-containing gas containing fluorine gas and fluorine compound gas, comprising a removal step,

[0015] The removal step removes the fluorine gas by bringing the fluorine gas-containing gas into contact with at least one metal salt selected from a chloride of a metal, a bromide of a metal, and an iodide of a metal.

[0016] [2] The method for removing fluorine gas according to [1], wherein the fluorine compound gas contains at least one selected from bromine pentafluoride, iodine heptafluoride, nitrogen trifluoride, tungsten hexafluoride, phosphorus trifluoride, and carbonyl fluoride.

[0017] [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 alkali metals and alkaline earth metals.

[0018] [4] The method for removing fluorine gas according to [3], wherein the metal species of the metal salt is at least one selected from lithium, sodium, potassium, magnesium, calcium, cesium, and barium.

[0019] [5] The method for removing fluorine gas according to any one of [1] to [4], wherein, in the removal step, the temperature at which the fluorine gas-containing gas is brought into contact with the metal salt is 0°C or higher and 120°C or lower.

[0020] [6] The method for removing fluorine gas according to any one of [1] to [5], wherein the fluorine gas-containing gas after the removal step contains fluorine gas at a content of 100 ppm by volume or less with respect to the total volume of the fluorine compound gas and the fluorine gas.

[0021] According to the present disclosure, it is possible to remove fluorine gas from fluorine compound gas containing fluorine gas as an impurity. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic view showing an example of a gas treatment device for removing fluorine gas according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] An embodiment of the present disclosure will be described below. Furthermore, the present embodiment illustrates one example of the present disclosure, and the present disclosure is not limited to the present embodiment. In addition, various modifications or improvements can be made to the present embodiment, and such modified or improved embodiments are also included in the present disclosure.

[0024] The fluorine gas removal method of the present embodiment is a method of removing fluorine gas from fluorine gas-containing gas containing fluorine gas and fluorine compound gas, which includes a step of removing fluorine gas by bringing the fluorine gas-containing gas into contact with at least one metal salt selected from the group consisting of a chloride of a metal, a bromide of a metal, and an iodide of a metal.

[0025] An embodiment of the gas treatment device of the present embodiment will be described. The gas treatment device 1 is provided with a purification column 6 filled with a metal salt. The metal salt functions as an adsorbent for fluorine gas. The purification column 6 has a supply port 4 that supplies fluorine gas-containing gas containing fluorine and fluorine compound gas, and a discharge port 5 that discharges purified gas obtained by performing adsorption treatment on the fluorine gas-containing gas with the adsorbent from inside the purification column 6 to the outside.

[0026] Furthermore, the gas treatment device 1 of the present embodiment is provided with a fluorine gas-containing gas supply mechanism 2 that supplies fluorine gas-containing gas, a fluorine gas flow rate control device 7, an additive gas supply mechanism 3 that supplies additive gas, and an additive gas flow rate control device 8. Furthermore, the discharge port 5 of the purification column 6 is connected to an analysis device 11 that performs analysis of fluorine gas in the fluorine gas-containing gas through a branch pipe.

[0027] The fluorine gas-containing gas supply mechanism 2 is connected to the fluorine gas flow rate control device 7 with a pipe, and the fluorine gas flow rate control device 7 is connected to the purification column 6 with a pipe. The gas sent out from the fluorine gas-containing gas supply mechanism 2 is supplied to the inside of the purification column 6 through the supply port 4, and the separation treatment of fluorine gas with the metal salt can also be performed in a temperature environment of 0°C or higher and 120°C or lower.

[0028] The gas supplied to the inside of the purification column 6 from the supply port 4 can be gas composed only of fluorine gas and fluorine compound gas, or can include other gas. That is, as shown in Figure 1 the pipe extending from the fluorine gas-containing gas supply mechanism 2 and the pipe extending from the additive gas supply mechanism 3 can be combined, and the combined pipe can be connected to the supply port 4 of the purification column 6. The gas other than fluorine gas and fluorine compound gas is not particularly limited, and for example, non-active gas can be cited. By diluting the fluorine gas-containing gas with non-active gas, local heating is easily suppressed, and the separation operation of fluorine gas is easily performed safely.

[0029] If the structure is like this, the fluorine-containing gas supplied from the fluorine-containing gas supply mechanism 2 and the inactive gas supplied from the additive gas supply mechanism 3 will mix in the confluenced piping to form a mixed gas, which will be supplied to the interior of the purification tower 6 from the supply port 4.

[0030] The mixed gas supplied to the interior of purification tower 6 can also contact the adsorbent at a temperature above 0°C and below 120°C to carry out adsorption treatment using the adsorbent. That is, the fluorine contained in the fluorine-containing gas is adsorbed by the adsorbent and separated.

[0031] The purified gas obtained by adsorption treatment using an adsorbent, namely the gas containing fluorine-containing compounds after fluorine separation, is discharged from the purification tower 6 to the outside through the outlet 5. In addition, a portion of the purified gas is supplied to the analysis device 11 through a branch pipe connecting the outlet 5 and the analysis device 11.

[0032] The purified gas is analyzed in the analytical apparatus 11. Specifically, quantitative or qualitative analysis of the fluorine contained in the purified gas is performed. Furthermore, there are no particular limitations on the analytical apparatus as long as it is capable of performing qualitative or quantitative analysis of the fluorine contained in the purified gas. For example, an ultraviolet-visible spectrophotometer, a Raman spectrophotometer, or a mass analyzer can be used as the analytical apparatus.

[0033] After the analysis is completed, the purified gas is supplied to the harmless device (not shown) through the analytical gas discharge pipe 9 connected to the analytical device 11.

[0034] Thus, if the gas processing device 1 of this embodiment is used, there is no need for complicated operations, and the fluorine gas contained in the fluorine-containing gas can be removed efficiently under mild conditions.

[0035] The fluorine removal method and the gas treatment apparatus 1 of this embodiment will be described in more detail below.

[0036] In the gas processing apparatus 1 of this embodiment, the fluorine-containing gas supplied from the fluorine-containing gas supply mechanism 2 is not particularly limited to any compound gas containing fluorine atoms, and can be at least one selected from bromine pentafluoride (BrF5), iodine heptafluoride (IF7), nitrogen trifluoride (NF3), tungsten hexafluoride (WF6), phosphorus trifluoride (PF3), and carbonyl fluoride (COF2).

[0037] There are no particular limitations on the materials used in purification tower 6, as long as they are corrosion-resistant to the fluorinated compound gases and fluorine gases used. For example, for parts that come into contact with fluorinated compound gases and fluorine gases, materials such as nickel, nickel-based alloys, aluminum, stainless steel, platinum, alumina ceramics, and fluororesins can be used.

[0038] As the nickel-based alloy, for example, INCONEL, HASTELLOY, MONEL, and the like can be listed. Further, the member composed of the above metal can be likely to react with the fluorine compound gas, and thus, before use, it is preferable to perform a treatment of flowing the fluorine compound gas, fluorine gas to form a passive film on the surface or the like. Because thus, generation of impurities is easily suppressed.

[0039] As the fluorine resin, for example, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxy ethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), Viton, KALREZ, and the like can be listed.

[0040] The content of the fluorine gas contained in the fluorine compound gas in the supply port 4 of the purification column 6, that is, the fluorine gas before the removal step of the fluorine gas can be 10 ppm by volume or more and less than 3% by volume, can be 100 ppm by volume or more and 2% by volume or less, or can be 200 ppm by volume or more and 1% by volume or less. If the amount of the fluorine gas is within the foregoing range, separation of the fluorine gas is easily achieved without using an excessively large device.

[0041] The fluorine gas adsorbent filled into the purification column 6 is at least one kind of metal salt selected from a chloride of a metal, a bromide of a metal, and an iodide of a metal. The metal salt can be a solid. The kind of metal of the metal salt can be at least one kind selected from an alkali metal and an alkaline earth metal, and from the viewpoint of easy availability, can be at least one kind selected from lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), cesium (Cs), and barium (Ba).

[0042] In the purification column 6, in addition to the foregoing metal salt, an auxiliary agent which does not react at all or hardly reacts with the fluorine compound gas and the fluorine gas can be further filled. By filling these auxiliary agents together with the metal salt, heat generated when the metal salt and the fluorine gas form a double salt is suppressed. The auxiliary agent can use a metal fluoride, a metal oxide, or the like, and from the viewpoints of easy availability and handling, it is preferable to use at least one kind selected from lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), magnesium fluoride (MgF2), calcium fluoride (CaF2), aluminum fluoride (AlF3), aluminum oxide (Al2O3), and barium fluoride (BaF2).

[0043] The shape of the foregoing metal salt and the auxiliary agent is not particularly limited, and for example, can be a pellet shape, a foil shape, a powder shape, a granular shape, or a block shape, or the like. In addition, a material containing the metal salt and the auxiliary agent as components, such as a pellet in which the metal salt and the auxiliary agent are mixed, can be used as the filler.

[0044] The temperature at which the fluorine-containing gas is brought into contact with the metal salt in the purification column 6 can be 0°C or higher and 120°C or lower, can be 10°C or higher and 100°C or lower, or can be 20°C or higher and 80°C or lower. In addition, the metal salt is a solid. When the temperature of use is within the aforementioned temperature range, the removal rate of fluorine gas contained in the fluorine-containing gas easily becomes high. In addition, by diluting the fluorine-containing gas with a non-active gas, local heating caused by adsorption of fluorine gas can be suppressed, and separation of fluorine gas can be safely performed. The kind of the non-active gas is not particularly limited, and for example, nitrogen, argon, helium, or the like can be exemplified. Among these non-active gases, from the viewpoint of easy availability and low cost, nitrogen is preferred.

[0045] The content of fluorine gas contained in the fluorine-containing gas in the outlet 5 of the purification column 6, that is, after the removal process of fluorine gas, is preferably 100 ppm by volume or less with respect to the total volume of the fluorine-containing compound gas and fluorine gas.

[0046] The following examples and comparative examples more specifically illustrate the present disclosure, but the present disclosure is not limited to the examples.

[0047] [Example 1]

[0048] A gas treatment device 1 having the same structure as that shown in Figure 1 A gas treatment device having the same structure as that shown in

[0049] Next, the fluorine-containing compound gas having a flow rate of 10 mL / minute and the additive gas having a flow rate of 20 mL / minute were mixed and supplied to the purification column 6. Thereafter, fluorine gas contained in the gas supplied to the purification column was adsorbed to 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 fluorine gas concentration in the additive gas was 0.1% by volume. In Table 1, the composition of the additive gas is indicated as "0.1%-F2 / N2".

[0050] Thereafter, a part of the purified gas discharged from the outlet 5 of the purification column 6 was extracted and the concentration of fluorine gas contained in the purified gas was measured by an inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Hiden Analytical). The results are shown in Table 1.

[0051] Further, the fluorine gas concentration was calculated by the following formula.

[0052] Fluorine gas concentration (ppm by volume) = fluorine gas flow rate / (fluorine gas flow rate + fluorine-containing compound gas flow rate)

[0053]

[0054] (Examples 2 to 15)

[0055] The kind and flow rate of the fluorine compound-containing gas, the kind of the additive gas, the composition and flow rate of the additive gas, the adsorbent, and the temperature of the purification column were changed as shown in Table 1, and otherwise, the removal of fluorine gas was performed in the same manner as in Example 1, and the fluorine gas concentration in the obtained purified gas was measured. The results are shown in Table 1.

[0056] In addition, in Example 25, the gas other than fluorine gas contained in the obtained purified gas was also analyzed.

[0057] (Comparative Examples 1 and 2)

[0058] Potassium fluoride and α-Al2O3 were used as the metal salt, respectively, and otherwise, the removal of fluorine gas was performed in the same manner as in Example 1, and the fluorine gas concentration in the obtained purified gas was measured. The results are shown in Table 1.

[0059] From the results of Examples 1 and 2, it was found that fluorine gas can be removed from the fluorine gas-containing gas containing fluorine gas and BrF5. In addition, when the fluorine gas concentration in the supply port of the purification column was 200 ppm by volume, the fluorine gas concentration in the discharge port of the purification column became lower than the detection lower limit (5 ppm by volume) of the mass spectrometer.

[0060] From the results of Examples 3 and 4, it was found that fluorine gas can be removed even when the fluorine compound-containing gas is IF7. In particular, when KI is used as the adsorbent, the removal effect of fluorine gas becomes high. This indicates that KI shows higher reactivity with fluorine gas than KBr.

[0061] From the results of Examples 1 and 5 to 8, it was found that fluorine gas can be removed even when the temperature of the purification column is set to 0°C or higher and 120°C or lower. In particular, when the temperature of the purification column is 50°C, fluorine gas in the fluorine gas-containing gas is removed the most.

[0062] From the results of Examples 9 to 15, it was found that fluorine gas in the fluorine compound-containing gas can be removed even when the adsorbent is KI, NaBr, LiBr, CsBr, CaBr2, MgBr2, and BaBr2.

[0063] From the results of Example 16, it was found that fluorine gas can be removed even when the fluorine gas concentration in the fluorine gas-containing gas is 10,000 ppm by volume.

[0064] From the results of Examples 17 and 18, it was found that fluorine gas can be removed even when KF and α-Al2O3 are added as the auxiliary agent to the adsorbent.

[0065] From the results of Examples 19 to 22, it was found that even in the case where the fluorine compound gas is WF6, NF3, PF3, or COF2, fluorine gas can be removed.

[0066] From the results of Examples 23 and 24, it was found that in the case where the fluorine compound gas is IF5 or BrF3, IF5 or BrF3 is adsorbed to KBr as the adsorbent, and although the adsorption capacity of fluorine gas decreases, fluorine gas can be removed.

[0067] From the result of Example 25, it was found that in the case where the fluorine compound gas is ClF3, fluorine gas can be removed, but a mixture of various halogen compounds is also obtained. It is considered that this is because ClF3 as the fluorine compound gas reacts with KBr as the adsorbent, and thus various halogen compounds are generated.

[0068] From the results of Comparative Examples 1 and 2, it was found that in the case where the adsorbent is only KF or only a-Al2O3, fluorine gas can hardly be removed. It is considered that this is because KF and a-Al2O3 do not react with fluorine gas at all or hardly react with fluorine gas.

[0069] Industrial Applicability

[0070] According to the present disclosure, fluorine gas contained in a fluorine compound gas can be easily removed, and a high-purity fluorine compound gas that can be used for etching and the like corresponding to miniaturization in the field of semiconductor manufacturing can be provided.

[0071] Explanation of Reference Numerals

[0072] 1 gas treatment device

[0073] 2 fluorine compound gas supply mechanism

[0074] 3 additive gas supply mechanism

[0075] 4 supply port

[0076] 5 discharge port

[0077] 6 purification column

[0078] 7 fluorine compound gas flow control device

[0079] 8 additive gas flow control device

[0080] 9 analysis gas discharge pipe

[0081] 11 analysis device

Claims

1. A method for removing fluorine gas, comprising a removal step, wherein the fluorine gas is removed from a fluorine-containing gas containing fluorine gas and a fluorine compound gas. The removal process involves contacting the fluorine-containing gas with at least one metal salt selected from 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 comprises at least one selected from 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 salt is selected from at least one of alkali metals and alkaline earth metals.

4. The method for removing fluorine gas according to claim 3, wherein the metal salt is selected from at least one of lithium, sodium, potassium, magnesium, calcium, cesium and barium.

5. 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 comes into contact with the metal salt is above 0°C and below 120°C.

6. The fluorine removal method according to claim 1 or 2, wherein the fluorine content in the fluorine-containing gas after the removal step is less than 100 ppm by volume relative to the total volume of the fluorine-containing compound gas and the fluorine gas.

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