JP2007176768A - Method for producing fluorine gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a fluorine gas, that is employable as an etching gas and a cleaning gas in producing semiconductors or liquid crystals, inexpensively on a massive scale. <P>SOLUTION: The method of producing fluorine gas comprises heating a higher metal fluoride under a gas flow. Examples of the higher valence metal fluoride preferably include a manganese fluoride represented by MnF<SB>x</SB>and a nickel potassium fluoride represented by K<SB>3</SB>NiF<SB>y</SB>wherein y is 6-7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a fluorine gas by heating a higher-order metal fluoride. More specifically, the present invention relates to a method for efficiently producing fluorine gas by heating a high-order metal fluoride under gas flow.

Fluorine gas is used as a raw material for synthesizing various fluorides, and recently has begun to be used as a cleaning gas and etching gas for electronic parts such as semiconductors and liquid crystals. General industrial production of fluorine gas is performed by electrolysis of KF · 2HF molten salt. The fluorine gas obtained by this method may contain impurity gases derived from electrodes and raw materials such as HF, O ₂ , N ₂ , CO ₂ , CF ₄ , SiF _4, etc., and a high-purity fluorine gas is obtained. It is difficult. Moreover, maintenance and safe operation are difficult for a fluorine electrolytic cell. Furthermore, since ancillary facilities are required, the capital investment is high, and the fluorine gas becomes very expensive if there is no amount of use, so far it has been difficult to supply inexpensive high-purity fluorine gas.

  Fluorine gas is the most oxidative combustion-supporting gas, highly toxic, and highly corrosive to materials. Therefore, in Japan, except for special cases, it is almost distributed as a compressed gas cylinder that is not diluted on a commercial basis. Not done.

  As a method for supplying fluorine gas other than a cylinder, an occlusion method using a fluorine occlusion alloy such as a higher order metal fluoride has been conventionally known. For example, in Japanese Patent Publication No. 5-502981 (Patent Document 1), fluorine gas is stored in a solid state, and when the fluorine gas is used, the container containing the solid is heated, A fluorine gas generator that generates fluorine gas by the reaction of the formula (1) is disclosed.

K ₃ NiF ₇ → K ₃ NiF ₆ + 1 / 2F ₂ (1)
The storage method is a method of generating fluorine gas by storing fluorine in the fluorine storage alloy and heating the fluorine storage alloy. Since fluorine gas can be generated by a simple operation of heating the fluorine storage alloy, The gas generator can be simplified and downsized. Therefore, the fluorine gas generator using the occlusion method is useful as an on-site type fluorine gas generator.

  However, the conventional fluorine gas generator using the occlusion method does not have a high fluorine gas generation pressure, and the gas generation amount is not sufficient. Furthermore, in order to increase the generation rate of fluorine, conventional methods of increasing the amount of heat of the heater of the gas generator or improving the thermal efficiency by installing internal fins are sufficient, but it is sufficient even if the heating temperature is raised A sufficient amount of fluorine gas could not be obtained.

Further, CoF ₃ is a metal fluoride that can generate more fluorine gas than K ₃ NiF _7.
And MnF ₄ are known. However, the generation rate and purity of fluorine gas, and a method for efficiently producing fluorine gas at an industrial level (kg unit or more) have not been studied so far. However, in the field of electronic industries such as semiconductors, microfabrication is progressing year by year, and the development of technology that uses fluorine gas as an etching gas is also progressing. Furthermore, fluorine gas is a gas with a low global warming potential. Use as a cleaning gas for a CVD chamber is also expected, and development of an inexpensive method for producing fluorine gas is required.
Japanese National Patent Publication No. 5-502981

  The present invention is intended to solve the problems associated with the prior art as described above, and the problem to be solved can be used, for example, as an etching gas and a cleaning gas when manufacturing semiconductors and liquid crystals. The object is to provide a method for producing a large amount of fluorine gas at low cost.

As a result of intensive studies to solve the above problems, the present inventors have found that the reason why the gas generation rate in the entire apparatus is not increased and the final gas generation amount is reduced is the adsorption and desorption of fluorine from the storage alloy. I thought it was in equilibrium. That is, in the fluorine storage method, fluorine is in an equilibrium state of adsorption and desorption with respect to the storage alloy, and when the fluorine storage alloy (high order metal fluoride) filled in the container is heated, the high order metal fluoride is filled. Since heat distribution occurs in the layer, the above adsorption / desorption equilibrium caused fluorine to desorb and generate fluorine gas at the high temperature part, but the generated gas was considered to be re-adsorbed at the low temperature part. Therefore, the present inventors generate fluorine gas from the high order metal fluoride layer by forming a gas flow in the high order metal fluoride layer and heating the high order metal fluoride under the gas flow. , Re-absorption of the generated fluorine gas into the metal fluoride can be prevented. As a result, the gas generation rate of the fluorine gas is increased, and the final gas generation per fluorine generator (higher metal fluoride) is achieved. The inventors have found that the amount can be increased and have completed the present invention.
That is, the present invention includes the following [1] to [9].

  [1] A method for producing fluorine gas, comprising heating a higher-order metal fluoride under gas flow.

[2] The higher-order metal fluoride contains manganese fluoride represented by an average composition formula MnF _x (x is 3 to 4) and a fluoride represented by an average composition formula K ₃ NiF _y (y is 6 to 7). The method for producing a fluorine gas according to the above [1], which is at least one metal fluoride selected from nickel potassium bromide.

[3] The method for producing fluorine gas according to [2], wherein the higher-order metal fluoride is manganese fluoride represented by an average composition formula MnF _x (x is 3 to 4).

  [4] The method for producing a fluorine gas according to any one of the above [1] to [3], wherein the heating temperature of the high-order metal fluoride is 300 to 450 ° C.

  [5] The method for producing a fluorine gas according to any one of the above [1] to [4], wherein the gas is heated in advance.

  [6] The method for producing fluorine gas as described in [5] above, wherein the heating temperature is 280 to 500 ° C.

  [7] The fluorine gas according to any one of [1] to [6], wherein the gas is at least one inert gas selected from nitrogen, argon, helium, krypton, and neon. Production method.

  [8] The method for producing fluorine gas according to any one of [1] to [6], wherein the gas contains fluorine gas.

[9] The metal fluoride after being used in the production method according to any one of [1] to [8] described above is occluded with fluorine gas, and the obtained higher-order metal fluoride is used to obtain the above [1] to [1] to [9]. [8] A method for producing fluorine gas, comprising generating fluorine gas by the production method according to any one of [8].

  According to the present invention, it is possible to prevent reabsorption of fluorine gas generated from a higher-order metal fluoride into the metal fluoride, improve the generation rate of fluorine gas, and produce a large amount of fluorine gas. Furthermore, it can be heated at a lower temperature than when no gas is circulated, which is economically advantageous in terms of reducing capital investment and running costs.

The present invention will be described in detail below.
The high-order metal fluoride used in the present invention is not particularly limited as long as it is stably present as a solid and generates fluorine gas by heating, and can be prepared by a conventionally known method, such as HF. This is a metal fluoride obtained by fluorinating a metal fluoride obtained by fluorinating a metal or a metal salt with a fluorinating agent having a weak oxidizing power, and further increasing the metal valence by fluorinating with a fluorinating agent having a strong oxidizing power. In the present invention, among such highly oxidized metal fluoride, the average composition formula MnF _x (x is 3-4) is manganese fluoride and the average composition formula K ₃ NiF _{y (y} is represented by 6
To 7) are preferred, and the average composition formula MnF _x (x is 3 to 4) is that the fluorine gas generation ratio relative to the higher-order metal fluoride is 10% by mass or more. Manganese fluoride is more preferable, x can be lower in that the heating temperature can be lowered, the cost of the container material can be reduced, and the fluorine gas generation rate is higher.

Usually, manganese fluoride MnF _x (x is 3 to 4) and nickel fluoride potassium K ₃ NiF _y (y is 6 to 7) are crystals represented by MnF ₃ and MnF ₄ , respectively. And a mixture of crystals represented by K ₃ NiF ₆ and crystals represented by K ₃ NiF ₇ . The above average composition formula represents the average composition of such a mixture. For example, in the case of manganese fluoride containing 50% MnF ₃ and 50% MnF ₄ , it is expressed as MnF _3.5 .
K ₃ NiF ₆ to 50%, in the case of manganese fluoride containing K ₃ NiF ₇ 50% is, K ₃ Ni
_Expressed as F _6.5 .

The “fluorine gas generation ratio with respect to the higher-order metal fluoride” is a value theoretically obtained from the fluorine gas generation reaction formula. For example, if the MnF _4, the following formula (2)
MnF ₄ → MnF ₃ + 1 / 2F ₂ (2)
As described above, ½ mol (19 g) of F ₂ is produced from 1 mol (131 g) of MnF ₄ . Therefore, the fluorine gas generation ratio from MnF _{4 is} 19/131 × 100 = 15 mass%.

In the present invention, the higher-order metal fluorides may be used alone or in combination of two or more.
In the present invention, the high-order metal fluoride is charged into a gas generation container, and the high-order metal fluoride is heated by circulating gas in the gas generation container. By this heating, for example, in the case of MnF ₄ , fluorine gas is generated as shown in the following formula (3).

2MnF ₄ → 2MnF ₃ + F ₂ (3)
The capacity of the gas generating container can be appropriately set depending on the amount of gas generated in the following steps. The material of the gas generating container is preferably selected from corrosion-resistant metal materials such as nickel, monel, and stainless steel, and the surface of these metal materials is preferably passivated in advance with fluorine gas. Alternatively, after nickel plating is applied to the surface of the metal material, the surface may be passivated with fluorine gas.

The high-order metal fluoride may be charged into the gas generating container, but it is preferable to charge with a proper gap. In particular, when the high-order metal fluoride is densely filled, pressure loss is generated by the high-order metal fluoride layer, which may hinder the gas flow. In addition, the fluorine gas generation reaction from the higher order metal fluoride (the above formula (3)) is expressed by the following formula (4)
2MnF ₃ + F ₂ → 2MnF ₄ (3)
If the gas distribution in the gas generation container is not sufficiently distributed, the generated fluorine gas may not quickly flow out of the container and may be absorbed again by the metal fluoride.

  Therefore, it is preferable to insert the high-order metal fluoride into the gas generation container with a gap so as to ensure a gas flow path. As a means for securing the gas flow path, a plurality of compartments are provided in the gas generation container by a gas-permeable structure, and a high-order metal fluoride is introduced into each compartment so as not to impair the gas permeability of the structure. The method of doing is mentioned. In this way, by introducing a high-order metal fluoride into the gas generation container with a gap to an extent that can secure a gas flow path, the gas can be circulated without being hindered by pressure loss or the like and generated fluorine. The gas can be quickly discharged out of the gas generation container, fluorine reabsorption can be prevented, the amount of fluorine gas generated can be increased, and the production efficiency of fluorine gas can be increased.

  The heating temperature of the higher order metal fluoride is preferably 300 to 450 ° C, more preferably 330 to 420 ° C, and particularly preferably 350 to 400 ° C. When the heating temperature is set to 300 ° C. or higher, the pressure of the fluorine gas generator can be made higher than the pressure of the fluorine gas supply destination, and the supply pressure of the fluorine gas can be easily adjusted. However, since the generation pressure of fluorine gas increases exponentially with respect to the heating temperature, it tends to be high pressure. When the heating temperature exceeds the above range, high-pressure fluorine gas is generated, which is not preferable in terms of safety, and it is necessary to increase the thickness of the container in order to increase the pressure resistance of the gas generating container, which is not preferable economically. .

  Although the said heating can be performed with a heater etc. from the exterior of a fluorine gas generator, in addition to this, it is preferable to provide and heat a heat-transfer body inside a fluorine gas generator. The higher order metal fluoride is efficiently heated by this heat transfer body, and a decrease in the fluorine gas generation rate can be prevented. The heat transfer body is not particularly limited as long as it can compensate for a temperature decrease due to an endothermic reaction during the generation of fluorine gas, and it is sufficient that a part of the heat transfer body is in contact with the inner wall of the fluorine gas generator.

  Examples of the gas to be circulated through the gas generator include inert gases such as nitrogen, argon, helium, krypton, and neon, and these may be used alone or as a mixture of two or more. . Further, the gas may contain fluorine gas. In particular, when fluorine gas is circulated as the gas, fluorine gas having a concentration of 100% by mass can be produced.

The gas supply rate to the gas generator is not particularly limited, and can be appropriately set according to a desired fluorine gas flow rate, fluorine gas concentration, and the like.
The gas is preferably preheated before being supplied to the gas generator. This heating can compensate for a temperature decrease due to an endothermic reaction during the generation of fluorine gas, and can prevent a decrease in the fluorine gas generation rate. The heating temperature of the gas is preferably 280 to 500 ° C.

  The fluorine gas thus produced can be appropriately diluted with nitrogen gas or the like and used as a fluorine gas having an arbitrary concentration. Further, the metal fluoride after the fluorine gas is produced by the above method has a reduced metal valence, but the metal fluoride can be converted into a higher-order metal fluoride by occluding the fluorine gas. It can be used again for the production of the fluorine gas.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by this Example. The examples and comparative examples show the results of the case where 20 vol% fluorine gas is supplied at 1000 cc / min.

(Fluorine gas analysis method)
Fluorine gas concentration, is passed through a 5% by weight of the aqueous solution of KI in sampled gas was determined by titrating the liberated I ₂ with Na ₂ S ₂ O ₃ aqueous solution of 0.1 N.

The fluorine gas production apparatus shown in FIG. 1 was used. 6500 g of MnF _3.8 was charged into a gas generation container 7 (made of Ni, internal volume 5 L, φ100 mm × 640 mm). The valve 1 was opened, the flow rate was controlled to 400 cc / min with the mass flow controller 3, nitrogen was supplied to the preheat column 2, heated to 360 ° C. with the preheater 4, and then supplied to the gas generation container 7. The heater 5 heated the MnF _3.8 to 350 ° C. in the presence of nitrogen gas to generate fluorine gas. At the same time, the valve 12 was opened, nitrogen gas whose flow rate was controlled to 400 cc / min by the mass flow controller 11 was supplied as a dilution gas, and mixed with the fluorine gas. At this time, the display of the flow meter 8 showed 1000 cc / min. Further, the fluorine gas concentration was measured by sampling from the valve 9 and the valve 13. The results are shown in Table 1.

  When the heating was continued, the gas flow rate in the flow meter 8 decreased to 960 cc / min. At this time, the fluorine gas concentration was measured by sampling from the valve 9 and the valve 13. The results are shown in Table 2.

  Thereafter, the nitrogen gas flow rate in the mass flow controller 3 was adjusted to 500 cc / min so that the gas flow rate in the flow meter 8 was 1000 cc / min, and the nitrogen gas flow rate in the mass flow controller 11 was adjusted to 300 cc / min. At this time, the fluorine gas concentration was measured by sampling from the valve 9 and the valve 13. The results are shown in Table 3.

  Subsequently, when the heating was continued, the gas flow rate in the flow meter 8 decreased so that the gas flow rate in the mass flow controller 3 was increased so that the gas flow rate in the flow meter 8 was 1000 cc / min. Reduced. When the gas flow rate in the mass flow controller 11 is adjusted to 0 cc / min (fully closed), the gas flow rate in the mass flow controller 3 is adjusted to 800 cc / min, and the gas flow rate in the flow meter 8 reaches 1000 cc / min, the valves 9 and 13 Further sampling was performed to measure the fluorine gas concentration. The results are shown in Table 4.

  Thereafter, the heating temperature by the heater 5 was increased to 360 ° C. At this time, the display of the flow meter 8 showed 1220 cc / min. Further, the fluorine gas concentration was measured by sampling from the valve 9 and the valve 13. The results are shown in Table 5.

  Thereafter, the gas flow rate in the mass flow controller 11 was adjusted to 220 cc / min and the gas flow rate in the mass flow controller 3 was adjusted to 580 cc / min so that the gas flow rate in the flow meter 8 was 1000 cc / min. At this time, the fluorine gas concentration was measured by sampling from the valve 9 and the valve 13. The results are shown in Table 6.

  When the heating was continued, the gas flow rate in the flow meter 8 decreased, so that the gas flow rate in the mass flow controller 3 was increased so that the gas flow rate in the flow meter 8 became 1000 cc / min as described above. The gas flow rate at 11 was reduced. Similarly to the above, when the gas flow rate in the mass flow controller 11 is reduced to 0 cc / min, the subsequent heating temperature by the heater 5 is increased so that the gas flow rate in the flow meter 8 becomes 1000 cc / min. The gas flow rate in the mass flow controller 3 and the gas flow rate in the mass flow controller 11 were adjusted. Table 7 shows the fluorine gas concentrations at 370 ° C, 380 ° C, 390 ° C, and 400 ° C.

  Gas production was stopped when the heating temperature by the heater 5 was 400 ° C., the gas flow rate in the mass flow controller 3 was 800 cc / min, and the gas flow rate in the flow meter 8 was 1000 cc / min. After the production was completed, the amount of fluorine gas generated was calculated by measuring the reduced weight of the gas generating container and found to be 900 g.

[Comparative Example 1]
The fluorine gas production apparatus shown in FIG. 2 was used. 6500 g of MnF _3.8 was charged into a gas generation container 7 (made of Ni, internal volume 5 L, φ100 mm × 640 mm), and heated to 360 ° C. by the heater 5 to generate fluorine gas. The flow rate of fluorine gas was controlled to 200 cc / min by the mass flow controller 14. At the same time, the valve 12 was opened, nitrogen gas whose flow rate was controlled to 800 cc / min by the mass flow controller 11 was supplied as a dilution gas, and mixed with the fluorine gas. At this time, the fluorine gas concentration was measured by sampling from the valve 9. The results are shown in Table 8.

  Subsequently, when the heating was continued, the fluorine gas flow rate in the mass flow controller 14 could not be maintained at 200 cc / min. Therefore, the heating temperature was gradually increased to maintain the fluorine gas flow rate in the mass flow controller 14 at 200 cc / min. When the heating temperature was 380 ° C., sampling was performed from the valve 9 to measure the fluorine gas concentration. The results are shown in Table 9.

  Subsequently, when the heating temperature was gradually increased so that the flow rate of fluorine gas in the mass flow controller 14 was 200 cc / min, when the temperature increased to 400 ° C., the flow rate of fluorine gas could not be maintained at 200 cc / min. Stopped. At this time, the fluorine gas concentration was measured by sampling from the valve 9. The results are shown in Table 10.

  After the completion of the production, the amount of fluorine gas generated was calculated by measuring the reduced weight of the gas generating container and found to be 650 g.

  Fluorine gas is a gas with extremely high combustion support, and it is very dangerous to transport a cylinder filled with fluorine gas as in the past, but according to the present invention, without transporting the fluorine gas itself, Fluorine gas can be easily obtained in large quantities on site.

FIG. 1 shows a schematic diagram of an example of a fluorine gas generator used in the present invention. FIG. 2 shows a schematic diagram of an example of a conventional fluorine gas generator.

Explanation of symbols

1 stop valve 2 preheater column 3 the mass flow controller 4 preheater 5 gassing container heater 6 fluorine generating agent (e.g., MnF _x)
7 Gas generation vessel 8 Flow meter 9 Sampling valve 10 Outlet valve 11 Mass flow controller 12 Stop valve 13 Sampling valve 14 Mass flow controller

Claims (9)

  A method for producing fluorine gas, comprising heating a higher-order metal fluoride under gas flow. The higher-order metal fluoride is manganese fluoride represented by an average composition formula MnF _x (x is 3 to 4) and nickel potassium fluoride represented by an average composition formula K ₃ NiF _y (y is 6 to 7). The method for producing fluorine gas according to claim 1, wherein the fluorine gas is at least one metal fluoride selected from the group consisting of: The highly oxidized metal fluoride, a manufacturing method of a fluorine gas as claimed in claim 2, wherein an average composition formula MnF x _(x is 3-4) is a manganese fluoride represented by.   The method for producing a fluorine gas according to any one of claims 1 to 3, wherein the heating temperature of the high-order metal fluoride is 300 to 450 ° C.   The said gas is heated previously, The manufacturing method of the fluorine gas in any one of Claims 1-4 characterized by the above-mentioned.   The said heating temperature is 280-500 degreeC, The manufacturing method of the fluorine gas of Claim 5 characterized by the above-mentioned.   The said gas is at least 1 sort (s) of inert gas chosen from nitrogen, argon, helium, krypton, and neon, The manufacturing method of the fluorine gas in any one of Claims 1-6 characterized by the above-mentioned.   The said gas contains fluorine gas, The manufacturing method of the fluorine gas in any one of Claims 1-6 characterized by the above-mentioned.   The metal fluoride after being used in the production method according to any one of claims 1 to 8 occludes a fluorine gas, and the resulting higher-order metal fluoride is used. A method for producing fluorine gas, comprising generating fluorine gas by a production method.

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