WO2005070824A1

WO2005070824A1 - Method for refining carbonyl difluoride

Info

Publication number: WO2005070824A1
Application number: PCT/JP2005/000776
Authority: WO
Inventors: Akinori Yamamoto; Takuji Kume; Seiji Takubo
Original assignee: Daikin Industries, Ltd.
Priority date: 2004-01-26
Filing date: 2005-01-21
Publication date: 2005-08-04
Also published as: JP2006282398A

Abstract

A method for producing a carbonyl difluoride wherein the metal content is reduced is characterized in that a carbonyl difluoride containing a metal component which has been stored in the liquid state in a container on the supply side is transferred to another container in the form of a fluid having a density of 0.7 g/cm3 or less.

Description

Specification

Purification method of carbonyl difluoride

Technical field

The present invention relates to a method for producing carbonyl difluoride having a reduced metal content.

Background art

[0002] Carbonyl difluoride (COF) is a raw material for organic fluorine compounds,

2

It is a useful substance that has applications such as lining gas.

[0003] As a method for producing carbonyl difluoride, a method of reacting carbon dioxide gas and fluorine gas in a gas phase (Patent Document 1), a method of electrolytic fluorination of carbon monoxide (Patent Document 2), A method of fluorinating phosgene with hydrogen fluoride in the presence or a method of fluorinating phosgene with hydrogen fluoride in the presence of a solvent and triethylamine (Patent Document 3), a method of fluorinating with sodium fluoride in a solvent (Patent Document 4), A method in which phosgene is fluorinated in the gas phase with hydrogen fluoride over an activated carbon catalyst (Patent Document 5), a method in which fluorinated carbon monoxide is directly fluorinated with fluorine gas (Non-patent Document 1), After contacting with an inorganic fluoride and then in the gas phase with activated carbon to obtain phosgene and carbonyl chloride, the carbonyl chloride is separated and contacted with activated carbon in the gas phase So, method who obtain carbonyl difluoride (Patent Document 6), etc. to give Ru method tetrafluoropropoxy O b by reacting ethylene and oxygen difluoride carboxymethyl sulfonyl (Patent Document 7) have been reported. However, none of the reports mention the content of metals or the method of reducing them.

[0004] Patent Literature 8, Patent Literature 9, and Patent Literature 10 describe tallying COF and gas containing COF.

twenty two

It is disclosed to be used as Jung gas. However, there is no mention of the metal content and the method of reducing it.

[0005] Unlike conventional cleaning gases (CF, CF, NF), carbon difluoride is non-

2 6 4 3

The reactivity and corrosiveness are always high.

2

Decomposes into F and may attack metals. In general, metal difluoride production equipment is required to have pressure resistance and corrosion resistance. Examples of the metal used include iron, copper, and alloys such as stainless steel, Hastelloy, Inconel, and Monel. Hastello In Ni-based alloys such as iron, monel, and inconel, a small amount of metal can be dissolved out depending on the operating conditions of power equipment, which is said to have high corrosion resistance, and can cause impurities in carbonyl difluoride. Iron and stainless steel are more likely. The metal content in carbonyl difluoride depends on the material of the equipment and the metal content in the raw materials. Any metal is conceivable. On the other hand, sodium, copper, etc. are one of the metals that must be prevented from being mixed most in semiconductors. Nevertheless, these patent documents do not describe a metal component. These metals need to be reduced in the production of semiconductors, for example, because they lead to a decrease in product yield and reliability.

Patent Document 1: JP-A-11-116216

Patent Document 2: Japanese Patent Publication No. 45-26611

Patent Document 3: JP-A-54-158396

Patent Document 4: US Patent 3088975

Patent Document 5: US Patent 2,866,622

Patent Document 6: EP0253527

Patent Document 7: US Patent 3639429

Patent Document 8: JP-A-10-223614

Patent Document 9: JP-A-2002-184765

Patent Document 10: JP 2002-158181A

Non-Patent Document 1: J. Amer.Chem.Soc., 91, 4432 (1969)

Disclosure of the invention

Problems to be solved by the invention

[0006] These metals can be removed by distillation or, more simply, by liquefied COF.

2 It is possible to vaporize once and transfer it to another container.

[0007] However, distillation requires a large amount of cost for equipment and operation of the equipment. In addition, while the distilled COF is being stored in the storage tank, there is a possibility that metal may be mixed in the tank.

2

Need to be distilled. In addition, the liquefied COF is once vaporized and transferred to another container.

2

In the method, first, the pressure is once reduced by a pressure control valve and vaporized, and then it is transferred to another container. A method of increasing the pressure with a compressor or the like, or a method of cooling a pressure vessel at a transfer destination is adopted. However, these methods require equipment such as a compressor and a refrigerator, and the operation thereof is expensive. Also, if a compressor is used, the COF contacts

2

There is a very high possibility that impurities such as genus particles are mixed. On the other hand, when cooling the container at the transfer destination with a refrigerator, if the transfer destination container is a cylinder, etc., the COF will be measured and filled while cooling the cylinder. .

2

[0008] As described above, carbonyl difluoride containing a small amount of metal has not been mentioned before, and therefore, there is no disclosed technique regarding a purification method for removing the metal. In addition, since a general purification method is costly, a simpler purification method is desired.

Means for solving the problem

[0009] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the carbonyl difluoride stored in a liquid state was transferred as a fluid having a density of 0.7 g / cm ³ or less to transfer the carbonyl difluoride. It has been found that the metal content in carbonyl chloride can be reduced.

[0010] The present invention relates to the following method for producing carbon difluoride having a reduced metal content.

1. Reduced metal content characterized by transferring carbon difluoride containing metal components stored in liquid form in the supply side container to another container as a fluid with a density of 0.7 g / cm ³ or less Method for producing carbon difluoride.

2. The method according to item 1, wherein the transfer of the fluid having a density of 0.7 g / cm ³ or less is performed while passing through a filter.

3. The method according to item 1 or 2, wherein the fluid is transferred while keeping the temperature of the supply side container higher than room temperature (20 ° C).

4. The method according to any one of Items 1 to 3, wherein the fluid is transferred while cooling another container filled with carbonyl difluoride.

5. The method according to any one of Items 14 to 14, wherein the metal content of the carbon difluoride before transfer is 100 ppb or more and the metal content of the carbon difluoride after transfer is 500 ppb or less. 6. The method for producing carboyl difluoride described in the item [1] or [1] of [1]-[5] for the production of semiconductors in which sodium in the transferred carbonyl difluoride is below the detection limit.

7. The method for producing carbon difluoride according to any one of claims 15 to 15, wherein the transferred carbonyl difluoride has a copper content of 5 ppb or less for semiconductor production.

8. The method according to any one of Items 1 to 7, wherein the other container is a cylinder.

The invention's effect

According to the present invention, the metal content contained in carbonyl difluoride can be removed by a simple method. Particularly, metals such as sodium and copper, which are problematic in the production of semiconductors, can be reduced to a level that does not adversely affect them, and the resulting carbon difluoride is used as a plasma cleaning gas for semiconductor production equipment. Useful.

Brief Description of Drawings

FIG. 1 shows one embodiment of a carbonyl difluoride transfer system of the present invention.

FIG. 2 shows an embodiment of the carbonyl difluoride transfer system of the present invention.

FIG. 3 shows an embodiment of the carbonyl difluoride transfer system of the present invention.

Explanation of symbols

[0013] A: Gas phase

B: liquid phase

C: Critical or supercritical fluid

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The present invention can be implemented in various forms. For example, when transferring carbonyl difluoride obtained by a known method from a supply-side container (for example, a storage tank) to another container (a storage tank), or filling a supply-side container power cylinder, etc. The method of the invention can be used. In particular, when transferring the supply-side container force to a container (for example, a cylinder) that uses COF,

2

In many cases, cylinders are shipped as products, and the transfer method of the present invention, which can remove metal components in products, can be preferably used.

The carbonyl difluoride in the supply container (storage container) contains a metal component. The total amount of metal components dissolved in carbon difluoride is usually 100000 ppb or more, especially 15 OOppb or higher. The content of metals, such as sodium and copper, which have an adverse effect on semiconductor manufacturing, can be contained in the carbon difluoride in the supply container at about 5 ppb or more for sodium and about 10 ppb or more for copper. The upper limit of the metal content is not particularly set V, but the metal content is particularly high! In such cases, the transfer rate of carbon difluoride is reduced, the density is reduced, the pressure is reduced, etc. Reduces the amount of dissolved metal and removes metals more efficiently.

[0015] The metal of the carbon difluoride after transfer is generally 500 ppb or less in total content, preferably

It is 450 ppb or less, more preferably 400 ppb or less. The content of metals, such as sodium and copper, after removal of metals that adversely affect semiconductor production is preferably 5 ppb or less for copper, and particularly preferably, the detection limit (lppb) or less for sodium, which is particularly preferable for sodium. Such a COF gas can be suitably used as a cleaning gas for a semiconductor manufacturing chamber.

2

In the present specification, metals that can be contained in carbon difluoride include Al, Ca, Cr, Cu, Fe, Mn, Na, Ni, Zn, Ag, Au, Ba, and Bi. , Cd, Co, Ga, Ge, K :, Li, Ni, Pb

, Sb, Sn, Sr and Tl forces, and the total amount of metals (metal content, metal content, etc.) means the total amount of these metals. Calculate the amount of metal below the detection limit as 0. Metals other than the above may be included or excluded from the total metal content in the present specification.

The material of the supply side container is usually a pressure-resistant metal container such as iron, copper, stainless steel! ^), Hastelloy, Inconel, Monel, etc. from the surface of this metal container, the metal dissolves in carbonyl fluoride. Therefore, the metal is mixed into the carbon difluoride. In addition, the material of another container (for example, storage tank II) to which carbon difluoride is transferred is usually a pressure-resistant metal container such as stainless steel (SUS), Hastelloy, iron or the like, or a fluorine resin. When the container is made of a metal such as stainless steel, it is preferable that the container be used within one week after the transfer and filling or be transferred again by the above method.

[0017] Density of the fluid to be transported is possible to remove the metal content as long 0. 7gZcm ³ below.

Beyond that, the metal content dissolves in the COF, so the effect of metal removal is insufficient or negligible.

2

Yes. The state of the fluid depends on the density of the liquid, gas, critical state, and supercritical state. Density of the fluid is 0. 003-0. 7gZcm ³ preferably 0. 03-0. 7g More preferably ZCM ³ is 0. 1-0. 7gZcm ^3. Density 0. 7gZcm ³ below fluid temperature is not particularly limited, when the supply side containers (e.g. below reservoir I) such as to transfer to another container (e.g., reservoir below [pi) is the fluid temperature ( The temperature of the storage tank I) is usually −30 ° C. to 200 ° C., preferably −20 ° C. to 180 ° C., and more preferably −10 ° C. to 160 ° C. If the temperature is too low, cooling of Storage Tank II will be costly, and if the temperature is too high, there is a risk of corrosion of the storage tank and piping.

The pressure is preferably 1.2 MPa-lOMPa. However, the density must be 0.7 g / cm ³ or less. Although the effect of removing metal can be obtained with a pressure lower than this, considering the productivity, 1.2 MPa or more is preferable, and considering the pressure resistance of pressure vessels such as storage tanks, lOMPa or less is appropriate. A preferred pressure range is 1.2-10 MPa, more preferably 1.5-8 MPa.

[0018] A detailed implementation method of the present invention includes the following method, but is not limited thereto. For example, when transferring carbonyl difluoride obtained by distillation or the like from storage tank 1 (for example, a receiver for distillation or the like) to the next storage tank II (for example, a measuring tank or product storage tank), the following method is used. Is possible. That is, as shown in FIG. 1, the gas phase portion of the storage tank I, the reservoir II while only passes the filter if necessary density 0. 7gZcm ³ following fluid through the pressure control valve and flow control valve or the like There is a way to transfer.

[0019] At this time, the temperature of the storage tank I may be lower than the critical temperature, but is generally about 40 ° C to 20 ° C, preferably about 30 ° C to 20 ° C. The temperature of the storage tank II may be the same as or lower than the temperature of the storage tank I. In general, the temperature is about -60 ° C to 20 ° C, preferably about -50 ° C to 15 ° C. The temperature difference between storage tank I and storage tank II is about 0-80 ° C, especially about 5-30 ° C, for example, about 10-25 ° C.

[0020] Density of the fluid is 0. 7gZcm ³ or less, preferably 0. 003-0. 7gZcm ^3, more preferably 0. 03-0. 7gZcm ³ and more preferably 0. 1-0. 7gZcm ^3. If the density of the fluid is too high, it will be difficult to remove the metal in carbonyl difluoride; if the density of the fluid is too low, a sufficient amount of Or it is necessary to compress carbon difluoride using a compressor or to make the temperature of another container much lower than the temperature of the supply side container. Become. [0021] Alternatively, as shown in FIG. 2, the tank II while passing a filter in accordance with density 0. 7gZcm ³ following fluid required via the pressure control valve and flow control valve from the liquid phase portion of the storage tank I There is a method of transport. Temperature at this time the tank I is, 15 ° if the above C to the critical temperature the density of the liquid body 0. 7gZcm ³ below (GAS DATA HANDBOOK MATHESON) and becomes a pressure regulating valve and flow control valve as required, It is transferred to storage tank 介 through the filter. If less than 15 ° C, required after the 0. 7gZcm ³ below density reduces the pressure in Kotogaa because the pressure regulating valve and flow control valve which density of the liquid is higher than 0. 7gZcm ³ by pressure There is a method of transferring to storage tank II through a filter according to the conditions. At this time, the temperature of the storage tank II does not depend on whether the temperature of the storage tank I is 15 ° C or more, and it is sufficient if the temperature of the storage tank is very low. Alternatively, as shown in FIG. 3, after previously adjusting the weight of the COF of the storage tank I so that the density of the fluid is 0.7 g / cm ³ or less, the storage tank I is heated to a critical temperature or higher.

2

There is a method of transferring to storage tank を通して through a filter as needed through a pressure control valve or a flow control valve. At this time, the temperature of storage tank II does not necessarily need to be lower than storage tank I, and may be higher than storage tank I in some cases. At this time, the temperature difference between the storage tanks I and II is 0-50 ° C, preferably 0-40 ° C, and more preferably 0-30 ° C. When the temperature is lower than the storage tank I, the temperature difference between the storage tanks I and II is more than 0 and 50 ° C or less, preferably more than 0 and 30 ° C or less, more preferably more than 0 and 25 ° C or less. .

[0022] Further, for example, the following method is used for filling a product cylinder from the storage tank III. In other words, if the method shown in Fig. 1 to Fig. 3 is used to read tank I into tank m and tank Π into cylinder, the method is almost the same, but there may be the following differences. For example, when filling a cylinder, it is desirable to pass through a filter in order to remove particles in the method shown in Figs. In addition, in the methods shown in FIGS. 1 and 2, unless the temperature of the cylinder is lower than that of the storage tank III, the filling amount in the cylinder is reduced. On the other hand, it is not economical to fill cylinders while cooling them, but it is not economical to cool cylinders by placing them in a thermostat, attaching a cooling jacket, or setting up a filling area in a freezer. can do. In the method shown in Fig. 3, by setting the temperature of storage tank III higher than room temperature, cooling of the cylinder is not required, and filling at room temperature becomes possible. For example pooled Le to 7000kg tank III, the temperature of the reservoir - the illustrating a more specific way, for example, if capacity of the reservoir III is a 10 m ³ difluoride carbonitrile If the temperature is raised to 30 ° C, a fluid with a density of 0.7 gZcm ³ can be obtained, and if the cylinder is kept at room temperature of about 20 ° C, it will be possible to fill with carbon difluoride at a density of at least 0.7 gZcm ³ Can be done. Further, the density of the fluid in the storage tank III is reduced by repeatedly filling, but by increasing the temperature of the storage tank III, the filling amount in the cylinder can be maintained. In addition, a decrease in the density of storage tank III has no effect on the effect of reducing the metal content, and an increase in the temperature does not affect the effect of reducing the metal content. The temperature of the 1S storage tank is generally 150 ° C or less is desirable. As described above, there are methods as shown in Figs. In the methods shown in FIGS. 1 and 2, since the liquid is separated into a liquid phase and a gas phase, the temperature is lower than the critical temperature, and the pressure is lower than the critical pressure. With the method in Fig. 3, it is possible to raise the pressure above the critical pressure by raising the supply side vessel above room temperature. The higher the pressure on the feed side, the greater the amount of carbonyl difluoride that can be transferred or filled into the cylinder. Therefore, it can be said that the method of FIG. 3 is more advantageous than the methods of FIGS. 1 and 2. Here, the temperature higher than room temperature refers to a temperature higher than about 20 ° C. which is near the critical temperature of carbon difluoride, and more preferably higher than about 23 ° C. which is higher than the critical temperature.

[0023] The filter is usually 200 µm-0.1 µm. The target value of the metal content after removing the force, the quality of the filter, the density of the fluid, the temperature of the supply side container, etc. It can be changed as appropriate.

Further, the term “cylinder” as used herein refers to a large pressure vessel such as 500 L or 1000 L in addition to a small pressure vessel such as 5 L, 10 L, or 47 L.

The metals to be removed include transition metal power, alkali metal, alkaline earth metal, anoreminidium, gallium, indium, thallium, genolemanium, tin, lead, arsenic, antimony, bismuth, and selenium, as described in the periodic table. , Tellurium, and polonium. More specifically, transition metals include scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, lutetium, rhodium, palladium, silver, Indicates cadmium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, and lanthanides and actinides. Alkali metals include lithium, sodium, potassium, rubidium, cesium, francium, and alkaline earth metals include beryllium, magnesium, calcium, strontium, norium, and radium. Show. In this specification, among the metals to be removed, Al, Ca, Cr, Cu, Fe, Mn, Na, Ni, Zn, Ag, Au, Ba, Bi, Cd, Co, Ga, Ge, K : Assess the degree of metal removal by calculating the contents of Li, Ni, Pb, Sb, Sn, Sr and Tl.

Among the above metals, the metals analyzed in the examples are Al, Ca, Cr, Cu, Fe, Mn, Na, Ni, Zn, Ag, Au, Ba, Bi, Cd, Co, Ga, Ge, K: only Li, Ni, Pb, Sb, Sn, Sr and Tl, indium, arsenic, selenium, tellurium, polonium, scandium, titanium, nonadium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium , Palladium, tantalum, tungsten, rhenium, osmium, iridium, platinum, mercury, lanthanoids, actinoids, rubidium, cesium, francium, beryllium, magnesium, and radium are exemplified by the above metals. It is not based.

For example, alkali metals (especially sodium) and copper are metals that have an adverse effect on the manufacture of semiconductor devices, and thus are preferably reduced to 5 ppb or less, preferably to the detection limit or less. In addition, iron, nickel, chromium, etc. are metals that dissolve into carbon difluoride from stainless steel containers, and it is important to reduce them.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Comparative Example 1

Ultrapure water is introduced into the lower part of the stainless steel pressure vessel storing COF via a valve.

2

I connected the PFA bottle straight. After cooling the stainless steel pressure vessel to 0 ° C, open the valve at the bottom of the vessel and pulsate COF (34 g) from the liquid phase to ultrapure water (11 lg).

2

did.

At this time, the density of the liquid was 0.8 gZcm ³ .

Example 1

It was connected to a PFA bottle filled with ultrapure water via a knob at the top of a stainless steel pressure vessel that stores COF2. After the stainless steel pressure vessel was cooled to 0 ° C, the valve at the top of the vessel was opened, and COF (49 g) was pulsated from the gas phase to ultrapure water (104 g). [0029] Density of gas at this time is expected to 0. 14gZcm ^3.

Example 2

It is connected to a PFA bottle filled with ultrapure water via a knob at the top of a stainless steel pressure vessel that stores COF2. After heating the stainless steel pressure vessel to 25 ° C to make it supercritical, the valve at the top of the vessel was opened, and COF2 (31 g) was vigorously bubbled into ultrapure water (104 g).

At this time, the density of the fluid was 0.5 gZcm ³ .

Excess analysis

The aqueous solutions subjected to publishing in Comparative Examples and Examples were placed in a platinum dish washed with concentrated hydrochloric acid, and evaporated to dryness using a hot plate for about 2 hours. This was again dissolved with 0.1N hydrochloric acid, and then concentrated similarly on a hot plate, and diluted with an equal volume by adding ultrapure water to prepare a sample. In addition, a blank sample was prepared by performing the same operation on unpublished water. The samples obtained here were subjected to metal analysis by ICP. Table 1 shows the results of the comparative example and the example. These results indicate the value obtained by subtracting the blank value if the obtained value is above the detection limit, and indicate ND if the obtained value is below the detection limit.

[Table 1]

[0033] Ag, Au, Ba, Bi, Cd, Co, Ga, Ge, K :, Li, Ni, Pb, Sb, Sn, Sr, and Tl were below the detection limit.

Industrial applicability

According to the present invention, carbonyl difluoride having a reduced metal content is removed by a simple method. can do. In particular, carbonyl difluoride having a reduced content of sodium and copper is useful as a plasma cleaning gas for semiconductor manufacturing equipment.

Claims

The scope of the claims

[1] A carbonyl difluoride containing metal component stored in a liquid state in the supply side container has a density of 0.7 g / cm

^{3. A} method for producing carbonyl difluoride having a reduced metal content, wherein the method is transferred to a separate vessel as a fluid of ³ or less.

[2] The method according to claim 1, wherein the transfer of the fluid having a density of 0.7 g / cm ³ or less is performed while passing through a filter.

[3] The method according to claim 1, wherein the fluid is transferred while the temperature of the supply side container is set to a temperature higher than room temperature!

[4] The method according to claim 1, wherein the transfer of the fluid is performed while cooling another container filled with carbon difluoride.

[5] The method according to claim 1, wherein the metal content of the carbon difluoride before transfer is 100000 ppb or more, and the metal content of the carbon difluoride after transfer is 500 ppb or less.

[6] The method for producing carbonyl difluoride according to claim 1, which is used for semiconductor production wherein sodium in the transferred carbonyl difluoride is below the detection limit.

7. The method for producing carbon difluoride according to claim 1, wherein the transferred carbonyl difluoride has a copper content of 5 ppb or less for semiconductor production.

[8] The method according to claim 1, wherein the other container is a cylinder.

[9] A cleaning gas for a semiconductor manufacturing chamber containing copper fluorca having a copper content of 5 ppb or less and a sodium content of 1 ppb or less.