KR20070057489A - The electrolyzer for manufacturing nitrogen tri-fluoride to minimize the amount of a vaporized hydrogen flouride and the manufacturing method using the same - Google Patents

Abstract

An electrolyzer for producing high purity nitrogen trifluoride(NF3) at high efficiency and low cost, which has an electrolyzer top plate cooling pipe that removes hydrofluoric acid(HF) generated during the electrolysis for producing nitrogen trifluoride, and a method of producing nitrogen trifluoride using the electrolyzer are provided. In an electrolyzer for producing nitrogen trifluoride(NF3) through molten salt electrolysis, the electrolyzer comprises an electrolyzer body(1), a fluorine resin coated bottom face(2), a fluorine resin coated separation plate(3), an electrolyte(4), a Ni anode(5), a Ni cathode(6), an anode connecting rod(7), a cathode connecting rod(8), a produced nitrogen trifluoride(NF3) outlet(9), a produced hydrogen(H2) outlet(10), an electrolyzer top plate(11), and a cooling pipe, wherein the cooling pipe includes an electrolyzer top plate cooling pipe(13). The electrolyzer top plate cooling pipe is a cooling system capable of controlling temperature of the electrolyzer top plate to 10 to 130 deg.C while proceeding the molten salt electrolysis. The electrolyzer further comprises an electrolyzer sidewall cooling pipe(12) in addition to the electrolyzer top plate cooling pipe to control temperature of the electrolyte to 100 to 130 deg.C during the molten salt electrolysis.

Description

ELECTROLYZER FOR MANUFACTURING NITROGEN TRI-FLUORIDE TO MINIMIZE THE AMOUNT OF A VAPORIZED HYDROGEN FLOURIDE AND THE MANUFACTURING METHOD USING THE SAME}

1 is a longitudinal cross-sectional view of an electrolytic cell for producing nitrogen trifluoride (NF 3) of the present invention.

* Explanation of symbols for main parts of drawings *

1: electrolytic cell body 2: bottom surface coated with fluorocarbon resin,

3: separator plate coated with fluororesin 4: electrolyte

5: nickel anode 6: nickel anode

7: cathode connecting rod 8: anode connecting rod

9: generated nitrogen trifluoride (NF ₃ ) outlet

10: generated hydrogen (H ₂ ) outlet 11: electrolytic cell top plate

12 electrolytic cell side wall cooling tube 13 electrolytic cell upper plate cooling tube

The present invention relates to nitrogen trifluoride (NF ₃₎ for producing the electrolytic cell, and more particularly to exhaust the excess with nitrogen trifluoride (NF ₃₎ in the manufacture of nitrogen trifluoride (NF ₃₎ through the molten salt electrolysis reaction The present invention relates to an electrolytic cell for producing nitrogen trifluoride (NF ₃ ) which can economically produce high purity nitrogen trifluoride by minimizing the amount of hydrofluoric acid (HF), and a method for producing nitrogen trifluoride (NF ₃ ) using the same.

In general, fluorine gas is an essential gas in the semiconductor manufacturing field, and nitrogen trifluoride (NF ₃ ) gas is widely used in semiconductor and TFT-LCD manufacturing as a cleaning gas or dry etching gas of semiconductors. Recently, with the activation of the semiconductor industry and the FPD industry, the demand for the chamber cleaning gas is rapidly increasing.

In particular, the use of other fluorides (eg, SF ₆ or C ₃ F _8, etc.) is limited by global warming measures, and easy to decompose nitrogen trifluoride (NF ₃ ) as an alternative to these fluorides. It is getting more attention in the field.

In general, the production of nitrogen trifluoride (NF ₃ ) is possible through a method of performing a direct fluorination reaction, a method using a plasma or a method through electrolysis.

The first method, direct fluorination, is a method in which fluorine gas is produced and then injected into a reactor containing ammonium bifluoride, which is synthesized through a two-step process. There are disadvantages. The second method, the plasma using method, still has low compatibility, requires high energy, and has low efficiency.

On the other hand, the molten salt electrolysis method through the electrolysis, the third method is possible to produce a high-purity product and a high yield compared to the above two methods, it is suitable for mass production of high-purity nitrogen trifluoride.

The production method of nitrogen trifluoride (NF ₃ ) through the electrolysis of the molten salt is as follows.

Electrodes made of carbon or nickel are used inside the electrolyzer, and potassium fluoride (KF) is used in the NH ₄ F-HF system or NH ₄ F-HF system derived from ammonium fluoride (NH ₄ F) and hydrofluoric acid (HF). Either KF-NH ₄ F-HF system or LiF-NH ₄ F-HF system derived by addition) is used.

Nitrogen trifluoride (NF ₃ ) and nitrogen (N ₂ ) gases are produced at the anode, hydrogen (H ₂ ) gases are produced at the cathode, and the gas evolution reaction is positive during the electrolysis of the electrolyte. At the same time, and produced by collecting and discharging the generated nitrogen trifluoride gas separately.

In addition, as nitrogen trifluoride (NF ₃ ) is generated in a narrow electrolyzer, nitrogen trifluoride (NF ₃ ) gas generated at the anode is mixed with hydrogen (H ₂ ) gas generated at the cathode, which may cause an explosion. Since this becomes large, to prevent the mixing of the product gas between the chambers and install a separator plate coated with fluorine resin to improve safety.

As matters to be managed in the preparation of molten salt electrolysis of nitrogen trifluoride (NF ₃ ) as described above, first, the nickel trifluoride (NF ₃ ) is easily dissolved and deposited on the cathode, resulting in nitrogen trifluoride (NF 3). ₃ ) and the mixing of hydrogen, and second, the nitrogen trifluoride (NF ₃ ) bubble does not rise vertically along the electrode, but the reaction is intense because it diffuses obliquely to the top, third, the nickel electrode in the form of NiF If the electrode tip is buried in NiF on the bottom of the electrolyzer, it will no longer function as an electrode, resulting in a decrease in yield of nitrogen trifluoride (NF ₃ ) and further short circuit or explosion. Is that there is.

In addition, an important matter to be managed additionally is to maintain a constant temperature of the molten salt in the electrolyzer. The general operating temperature of the electrolyzer is preferably 100 to 130 ° C., because it is easy to operate, has good electrical conductivity, and has good electric current efficiency.

On the other hand, when the operating temperature of the electrolytic cell exceeds 130 ℃, the vaporized electrolyte component (NH ₄ F-HF or HF) blocks the outlet of the product gas to finally reduce the yield of nitrogen trifluoride (NF ₃ ) There is a problem.

The most important factor in controlling these problems is the emissions of hydrofluoric acid (HF). In other words, the nitrogen trifluoride (NF ₃₎ major factor in determining the yield of the electrolyte is hydrofluoric acid (HF) is nitrogen trifluoride (NF ₃₎ inhibition of the content that is vaporized in an amount in excess of the generation.

In general, since the vapor pressure of hydrofluoric acid (HF) is about 100mHg (100 ° C) at a temperature of 100 to 130 ° C, a large amount of hydrofluoric acid (HF) is contained in the anode and the cathode, particularly the cathode. In the case of (Anode), in addition to nitrogen trifluoride (NF ₃ ) generated in the exhaust gas, it is accompanied by vaporized hydrofluoric acid (HF) and occupies the highest content of 20-25% of the total composition of nitrogen trifluoride (NF ₃ ) gas. Done.

Generally, in order to lower the amount of hydrofluoric acid, a NaF trap or a low temperature cooling trap which removes hydrofluoric acid (HF) immediately after the generated gas is discharged from the electrolytic cell is installed, but this cannot be a fundamental solution in process efficiency and productivity.

Therefore, if the amount of hydrofluoric acid (HF) contained in the nitrogen trifluoride (NF ₃ ) gas discharged from the electrolytic cell is greatly reduced by suppressing the evaporation of the electrolyte, the consumption of hydrofluoric acid (HF), which is an important raw material, can be reduced. In addition, it will also be possible to improve the yield of nitrogen trifluoride (NF ₃ ) per hour. In particular, by reducing the load on the post-process for the production of high purity nitrogen trifluoride (NF ₃ ) can improve the efficiency of the overall process and apparatus.

In order to achieve this purpose, it is possible to safely and economically treat hydrofluoric acid (HF) by significantly reducing the amount of hydrofluoric acid (HF) contained in the nitrogen trifluoride (NF ₃ ) gas discharged from the electrolytic cell by suppressing evaporation of the electrolyte. There is a need to develop an electrolytic cell for the production of nitrogen trifluoride (NF ₃ ) having an improved structure compared to a conventional electrolytic cell.

The present invention is to solve the above problems of the prior art,

One object is nitrogen trifluoride (NF ₃₎ a high-purity nitrogen trifluoride of high efficiency low cost having an electrolytic cell top plate cooling pipe to remove the hydrofluoric acid (HF) generated during the electrolytic reaction for the production of the present invention (NF ₃₎ for preparing It is to provide an electrolytic cell.

Another object of the present invention is to provide a method for producing nitrogen trifluoride using an electrolytic cell for manufacturing high efficiency low cost high purity nitrogen trifluoride (NF ₃ ) having an electrolytic cell upper plate cooling tube.

One aspect of the present invention for solving the above technical problem is

Body of electrolyzer, bottom surface coated with fluorine resin, separator plate coated with fluorine resin, electrolyte, nickel anode (Ni anode), nickel anode (cathode), cathode connecting rod, anode connecting rod, produced nitrogen trifluoride (NF ₃ ) An electrolyzer consisting of an outlet, a generated hydrogen (H ₂ ) outlet, an electrolyzer top plate, and a cooling tube, wherein the cooling tube relates to an electrolyzer for the production of nitrogen trifluoride (NF ₃ ), comprising an electrolyzer top plate cooling tube.

According to another aspect of the present invention, the weight percent ratio of hydrofluoric acid (HF) to ammonium fluoride (NH ₄ F) in an electrolytic cell for producing nitrogen trifluoride (NF ₃ ) is characterized in that it comprises the electrolytic cell upper plate cooling tube. A method for producing nitrogen trifluoride (NF ₃ ) using an electrolyte having NH ₄ F = 1.0 to 2.6.

Hereinafter, with reference to the accompanying drawings will be described in more detail the present invention.

1 illustrates a longitudinal section of an electrolytic cell for producing nitrogen trifluoride (NF 3) as an embodiment of the present invention.

Referring to Figure 1, the electrolytic cell of the present invention is an electrolyzer body (1), the bottom surface (2) coated with a fluorine resin, the separator plate (3) coated with a fluorine resin, the electrolyte (4), a nickel anode (Ni anode) (5), nickel cathode (6), cathode connecting rod (7), anode connecting rod (8), produced nitrogen trifluoride (NF ₃ ) outlet (9), generated hydrogen (H ₂ ) outlet (10) ), An electrolytic cell upper plate 11, an electrolytic cell side wall cooling tube 12, and an electrolytic cell upper plate cooling tube 13.

In detail with respect to each configuration of the electrolytic cell of the present invention, the bottom surface 2 and the separator 3 is coated with a fluororesin material to prevent corrosion, the fluororesin material that can be used is not particularly limited, Polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, etc. can be illustrated, and is preferable. It is preferably a polytetrafluoroethylene or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer having acid resistance and heat resistance.

As the electrolyte 4 used in the present invention, ammonium fluoride-fluoric acid (NH ₄ F-HF) is used, and the composition ratio of the electrolyte in the nitrogen trifluoride (NF ₃ ) electrolytic cell is based on hydrofluoric acid (NH ₄ F). The percentage by weight of HF) is comprised between 1.0 and 2.6.

In the present invention, the electrodes 5 and 6 use electrodes made of nickel (Ni). A carbon electrode may be used in addition to the nickel electrode. However, since it is not easy to remove carbon tetrafluoride (CF ₄ ), which is an easily generated impurity during the reaction, it is preferable to use a nickel (Ni) electrode.

The cooling tubes 12 and 13 are used to suppress evaporation of the electrolyte component so that the hydrofluoric acid as an impurity is not excessively discharged in the production of high-purity nitrogen trifluoride. It characterized in that it comprises a cooling tube 13 installed. The refrigerant for cooling the electrolytic cell upper plate cooling tube 13 of the present invention may be selected and used according to convenience, and the same refrigerant as that for methyl alcohol, ethyl alcohol, ethylene glycol, and the like commonly used as the refrigerant for cooling the electrolytic cell cooling tube may be used. have.

In addition, the electrolytic cell upper plate cooling tube 13 used in the present invention may change and maintain the temperature of the electrolytic cell upper plate 11 by adjusting the temperature of the refrigerant, and considering the generation efficiency of nitrogen trifluoride (NF ₃ ). The preferred temperature range is 10-130 ° C, more preferably 85-125 ° C. At lower temperatures below 10 ° C, the operating temperature of the electrolyzer is lowered, leading to a decrease in efficiency due to a decrease in reactivity. If the temperature is above 130 ° C, the temperature of the electrolyzer is too high, resulting in side reactions (the formation of N ₂ ) resulting in decreased efficiency. do.

On the other hand, the cooling tube is a cooling tube of the side wall of the electrolytic cell in addition to the electrolytic cell upper plate cooling tube 13 in order to control the temperature of the electrolyte 4 during the electrolytic reaction for the production of nitrogen trifluoride (NF ₃ ) in the range of 100 -130 ℃. (12) may be further included.

The operating temperature of the electrolytic cell is preferably 100-30 ℃, ammonium fluoride-

Hydrofluoric acid (NH ₄ F-HF, melting point: 126 ℃) system when the temperature of the electrolyte is less than 100 ℃ in the ammonium fluoride-hydrofluoric acid (NH ₄ F-HF) is a possibility that the nitrogen trifluoride (NF ₃ becomes large to be immersed in the electrolytic bath When the production rate decreases rapidly and exceeds 130 ° C., the reaction rate may increase, but the vaporized electrolyte component including hydrofluoric acid (HF) increases to block the generated gas outlet 9. As a result, when the outlet 9 is blocked, as the internal pressure in the anode chamber increases, the interface is lowered than the separator plate, and nitrogen trifluoride (NF ₃ ) is incorporated into the cathode chamber. Finally, the yield of nitrogen trifluoride (NF ₃ ) is reduced.

Therefore, in order to control the operating temperature of the electrolytic cell, the electrolytic cell upper plate cooling tube 13 and the electrolytic cell side wall cooling tube 12 may be installed together, and for this purpose, the electrolytic cell upper plate cooling tube 13 may be an electrolytic cell. It may be connected with other cooling pipes inside or outside, or may be installed and used independently of each other.

The method for producing nitrogen trifluoride (NF ₃ ) through the molten salt electrolysis reaction in the electrolytic cell according to the present invention configured as described above is the weight ratio of hydrofluoric acid (HF) to ammonium fluoride (NH ₄ F) is HF / It is characterized in that the molten salt electrolysis reaction using an electrolyte of NH ₄ F = 1.0 ~ 2.6. If the weight percentage of hydrofluoric acid (HF) is too small, less than 1.0, the production efficiency of nitrogen trifluoride (NF ₃ ) decreases due to an increase in the viscosity and side reaction of the electrolyte, whereas an excess of hydrofluoric acid (HF) exceeds 2.6 Not only causes economic loss but also causes corrosion.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. However, this is for the purpose of explanation and the present invention is not limited thereto.

Example 1

A cooling tube 13 for suppressing vaporization of the electrolyte component was provided on the upper plate 11 of the electrolytic cell for producing nitrogen trifluoride (NF ₃ ), and a cooling tube 12 was further provided on the side of the electrolytic cell. The refrigerant for cooling the electrolytic cell upper plate and the side cooling tubes 12 and 13 can be selected and used according to convenience, and ethylene glycol was used in methyl alcohol, ethyl alcohol, and ethylene glycol. The temperature of the upper plate 11 was maintained at 10 ° C. by adjusting the coolant temperature.

The bottom surface 2 and the separator 3 were made of fluorine resin to prevent corrosion, and the electrodes 5 and 6 were made of nickel (Ni). As the electrolyte 4, ammonium fluoride-fluoric acid (NH ₄ F-HF) was used, and the composition ratio of the electrolyte in the electrolytic cell for producing nitrogen trifluoride (NF ₃ ) was% by weight of hydrofluoric acid (HF) relative to ammonium fluoride (NH ₄ F). The ratio was set to 2.0, and a thermal couple was installed in the electrolyzer and the electrode so that the temperature of the electrolyte 4 during the reaction could be operated at 100 to 130 ° C. so that the temperature according to the conditions could be observed. In the examples, 125 ℃ was maintained.

Detectors for TCD and DID on the generated nitrogen trifluoride (NF ₃ ) outlet 9 at the top of the anode (5) and the generated hydrogen (H ₂ ) outlet (10) at the top of the anode to analyze the gases produced after the reaction. Gas chromatography (Gas Chromatography) was installed to enable analysis of impurity gas generated after electrolysis reaction.

Since the electrolytic cell was hygroscopic, dehydration electrolysis was carried out at low current before carrying out this reaction. After 40-50A flow at low current, 200 hours at average current density of 1-2A / dm ² , dehydration electrolysis reaction is carried out when the concentration of oxygen (O ₂ ) produced at the anode is kept at 2%. dehydration electrolysis) was terminated.

Then, hydrogen (H ₂ ) and trioxide discharged by operating the molten salt electrolysis reaction to produce nitrogen trifluoride (NF ₃ ), 4000 hours at 250 to 500 A and an average current density of 10 to 20 A / dm ² . Nitrogen fluoride (NF ₃ ) and other by-product content analysis and nitrogen trifluoride (NF ₃ ) production efficiency analysis was performed, the results are shown in Table 1 below.

Example 2

Except that the temperature of the electrolytic cell top plate was carried out in the same manner as in Example 1, the content analysis and the analysis results of the production efficiency of nitrogen trifluoride (NF ₃ ) are shown in Table 1 below.

Example 3

Except that the temperature of the electrolytic cell upper plate was set to 85 ℃ was carried out in the same manner as in Example 1, the content analysis and analysis results of the production efficiency of nitrogen trifluoride (NF ₃ ) are shown in Table 1 below.

Example 4

Except that the temperature of the electrolytic cell top plate was 100 ℃ was carried out in the same manner as in Example 1, the content analysis and the analysis results of the production efficiency of nitrogen trifluoride (NF ₃ ) are shown together in Table 1 below.

Example 5

Except that the temperature of the electrolytic cell upper plate was set to 125 ℃ was the same as in Example 1, the content analysis and analysis results of the production efficiency of nitrogen trifluoride (NF ₃ ) are shown in Table 1 below.

Comparative Example 1

Except not installing the electrolytic cell upper cooling tube was carried out in the same manner as in Example 1, the content analysis and the analysis results of the production efficiency of nitrogen trifluoride (NF ₃ ) are shown in Table 1 below.

As can be seen in Table 1, compared to Comparative Example 1, in the case of Examples 3 to 5, the amount of hydrofluoric acid (HF) vaporized rapidly decreased to about 5-15%, so that the production efficiency of nitrogen trifluoride (NF ₃ ) was increased. It can be seen that about 30% is greatly improved. That is, it can be confirmed that the reactivity is greatly improved by controlling or inhibiting the electrolyte components such as hydrofluoric acid (HF) vaporized and discharged due to heat generated inside the nitrogen trifluoride (NF ₃ ) electrolytic cell more finely through the electrolytic cell upper plate cooling system. have.

However, it can be seen that when the temperature of the electrolytic cell upper plate is set too low as in Examples 1 and 2, the operating temperature of the electrolytic cell is lowered, resulting in a decrease in efficiency due to a decrease in reactivity.

According to the electrolytic cell apparatus for producing nitrogen trifluoride (NF ₃ ) including the electrolytic cell upper plate cooling tube according to the present invention and the method for producing nitrogen trifluoride using the same,

By suppressing evaporation of hydrofluoric acid (HF), which is discharged in excess at the same time with the produced nitrogen trifluoride (NF ₃ ) component, it is possible to effectively lower the content of impurities including hydrofluoric acid (HF), and important raw material, hydrofluoric acid (HF) It is possible to reduce the consumption of carbon dioxide, thereby improving the process unit and reducing the load of the post-process for the production of high purity nitrogen trifluoride (NF ₃ ), thereby improving the yield of nitrogen trifluoride (NF ₃ ) production and overall utility and device efficiency. can do.

Claims (5)

In the electrolytic cell for producing nitrogen trifluoride (NF ₃ ) through molten salt electrolysis, Body of electrolyzer, bottom surface coated with fluororesin, separator plate coated with fluorine resin, electrolyte, Ni anode, Ni cathode, cathode connecting rod, anode connecting rod, nitrogen trifluoride (NF ₃ ) outlet, the generated hydrogen (H ₂₎ outlet, the electrolytic cell tops, as an electrolytic cell consisting of a cooling tube, said cooling tube is nitrogen trifluoride (NF ₃₎ for producing electrolytic cell characterized in that it comprises an electrolytic cell top plate condenser. The method of claim 1, wherein the electrolytic cell top plate condenser is nitrogen trifluoride (NF ₃₎ for producing electrolytic cell characterized in that the cooling system which can adjust the temperature of the top plate of the electrolytic cell in progress molten salt electrolysis reaction to 10~130 ℃. According to claim 1 or 2, wherein the electrolytic bath further comprises a cooling tube of the inner wall of the electrolytic cell in addition to the upper plate cooling tube of the electrolytic cell in order to adjust the electrolyte temperature during the molten salt electrolysis reaction to 100 ~ 130 ℃. Electrolyzer for the production of nitrogen trifluoride (NF ₃ ). The method of claim 1 or 2, wherein the electrolytic cell upper plate cooling tube is connected with other cooling tubes outside or inside the electrolytic cell, or for the production of nitrogen trifluoride (NF ₃ ), which can be installed and used independently of each other. Electrolyzer. The electrolytic reaction of molten salt using an electrolyte in which the weight percentage ratio of hydrofluoric acid (HF) to ammonium fluoride (NH ₄ F) is HF / NH ₄ F = 1.0 to 2.6 in the electrolytic cell according to claim 1 or 2. A process for producing nitrogen trifluoride (NF ₃ ).

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