JPH01234301A - Production of gaseous metal fluoride - Google Patents

Abstract

PURPOSE:To produce a gaseous metal fluoride in good yield and inexpensively so as to prevent mixing of fine powder of a simple substance metal in the gaseous metal fluoride by compression-molding a mixture of a simple substance metal with a specified molding additive, then allowing the mixture to react with gaseous F2. CONSTITUTION:Powder of simple substance metal such has Mo, W, Nb, Si, Ge, etc., is mixed with powder of a solid fluoride as a molding additive which does not react with gaseous F2 and is held at solid state at a temp. where said simple substance metal reacts with gaseous F2 (in a proportion of 30-70wt.% of said simple substance metal basing on the total wt. of the mixture), and the mixture is compression-molded with a pelletizer, etc., under 1-3t/cm<2> pressure. The solid fluoride to be used is, for example, NaF, CaF2, Na2AlF6, etc. A gaseous metal fluoride is obtained by allowing the molded body to react with gaseous F2 (pref. diluted usually to 5-40vol.% with inert gas) at 250-500 deg.C under normal pressure -10kg/cm<2> for 2-10hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing a gaseous metal fluoride by reacting an elemental metal with fluorine gas.

"Conventional technology" Gaseous metal fluorides include tungsten hexafluoride (WF).
, molybdenum hexafluoride (MoFs), antimony trifluoride (SbFs), niobium trifluoride (NbFs), tantalum trifluoride (TaFs), titanium tetrafluoride (TiFn), silicon tetrafluoride (SiF4), Germanium tetrafluoride (GeF,
), arsenic trifluoride^sh), and other compounds.

Among these compounds, -F, MOF&, etc. are expected to be used as raw materials for electrode materials for semiconductors. Especially the deceased,
Tungsten silicide (WSit) and molybdenum silicide (MoSi
z) is attracting attention as a wiring material for high-density integrated circuit LSI. Further, the above gaseous metal fluorides, including WFa and MoF&, are also used as raw materials for various fluorinating agents and optical materials.

The gaseous metal fluoride used in the present invention refers to a metal fluoride that is gaseous at the temperature at which an elemental metal and F2 gas react.

Conventionally, gaseous metal fluorides are composed of elemental metals and fluorine (-S).
F.) It is manufactured by contacting and reacting with gas at high temperature.

Since F2 gas is a highly toxic and very active substance, in the above contact reaction, F2 gas is mixed with nitrogen (Nt) gas, so that its concentration is 10 to 30% by volume.
It is used after being diluted with an inert gas such as argon (Ar) gas.

When reacting the above-mentioned elemental metal with the F2 gas, the elemental metal is usually used in the form of powder in order to ensure rapid and good contact between the elemental metal and the F2 gas. This reaction is carried out by providing a fluidized bed or a fixed bed in a reactor and passing F2 gas diluted with N2 gas or the like into the metal powder layer on the fluidized bed or fixed bed.

"Problem to be Solved by the Invention" However, such a method has the following problems.

In other words, in the fluidized bed method, diluted Ft gas passes through a bed of fluidized metal powder, so fine powder of the metal is entrained in the gaseous metal fluoride that is generated, causing a decrease in the purity of the product. Become. In addition, the reaction yield was also 8 based on F agas standard.
The limit is about 0%, which is also insufficient in this respect.

On the other hand, in the fixed bed method, the reaction between the metal powder, F, and gas takes place only on the surface of the metal powder layer, so the single metal powder and F
There is a problem that the contact area between the two gases is small and therefore the reaction yield is low, and there is also a problem that a large amount of unreacted F2 gas is mixed into the generated gaseous metal fluoride. Furthermore, as the reaction progresses, the single metal powder is pulverized,
This pulverized single metal is entrained in the generated gas,
There is also the problem of lowering the purity of the product. In order to increase the reaction yield in the above fixed bed method, it is necessary to increase the contact area between the single metal powder and the F2 gas, and the reactor must be made considerably large.However, in this reaction, Since extremely corrosive F gas is used as a raw material,
The reactor is usually made of expensive nickel. Therefore, increasing the size of the reactor is a problem as it increases costs considerably.

[Means for Solving the Problems] In view of the above situation, the present inventors have attempted to prevent the mixing of single metal fine powder into gaseous metal fluoride, and to produce gaseous metal fluoride at low cost with high yield. As a result of various studies on manufacturing methods, we added a specific forming aid to a single metal, pressed
The inventors have discovered that the above object can be achieved by using the molded body as a raw material for a single metal, and have completed the present invention.

That is, the present invention provides a method for producing a gaseous metal fluoride by reacting an elemental metal with fluorine gas, in which a solid metal fluoride that does not react with fluorine is added and mixed with the elemental metal as a forming aid in advance. - "Detailed Disclosure of the Invention" Hereinafter, the present invention will be described. Detailed explanation of.

The gaseous metal fluoride that can be produced in the present invention is a fluoride that can be usually synthesized by direct reaction of fluorine and metal, and as mentioned above, the temperature at which the elemental metal and F2 gas react, for example,
It is gaseous at temperatures of 300°C or higher. An example of such a compound is tungsten hexafluoride (WF
6) Molybdenum hexafluoride (MoFJ, antimony trifluoride (SbF'S), niobium trifluoride (NbFs), tantalum trifluoride (TaF), titanium tetrafluoride, (TiF),
Silicon tetrafluoride (SiF4), germanium tetrafluoride (Ge
), arsenic trifluoride (ASF3), and the like.

The shape of the raw metal used in the present invention is not particularly limited, but it is preferably in the form of a powder. The reason for this is, as will be described later, in the present invention, it is necessary to add and mix a forming aid to this single metal, pressurize and mold this mixture, and make a molded object. This is because it is preferable to mix the agents as uniformly as possible in order to obtain a high reaction yield, and for this purpose it is convenient for the elemental metal to be in powder form. In addition, powder is easier to press and mold.

It goes without saying that the elemental metal used in the present invention is the metal constituting the gaseous metal fluoride.

Next, the molding aid will be explained.

In the present invention, a solid fluoride that does not react with fluorine is used as a molding aid, but this solid fluoride needs to remain solid even at the temperature at which the elemental metal and F2 gas react. For example, lithium fluoride (Li
F), sodium fluoride (NaF), potassium fluoride (
F), rubidium fluoride (RbF), cesium fluoride (C
Metal fluorides of lAl1 such as sF); beryllium fluoride (
BeFz), magnesium fluoride (MgF2), calcium fluoride (CaFz), strontium fluoride (Srh),
Group IIA metal fluorides such as barium fluoride (BaFz);
Aluminum fluoride (AI F3), gallium fluoride (
Examples include total fluorides of the IIIA group such as GaFx), insidium fluoride (InFx), and thallium fluoride (1!Pff); and double salts such as sodium aluminum fluoride (NaxAffiFJ).A mixture of these may also be used.

It should be noted that these solid metal fluorides need to be mixed with a single metal and then pressurized and molded, so it is preferable that they be in powder form as in the case of the single metal.

Next, in the present invention, the single metal and the solid metal fluoride as a forming aid are mixed together and pressed and formed. The mixing ratio of the two at this time is preferable because if the ratio of the single metal is too large, the reactivity will improve but the strength of the molded body will decrease, and as a result, there is a risk that the molded body will turn into powder as the reaction progresses. do not have. On the other hand, if the proportion of the elemental metal is too small, the strength of the molded product will not be a problem, but the reactivity will decrease. Therefore, the mixing ratio is usually such that the content of elemental metals and metals is in the range of 30 to 70 weight percent based on the total amount of both.

In the present invention, a single metal and a solid metal fluoride are mixed and molded. However, since it is undesirable if the resulting molded product collapses or becomes powder during the reaction, the molding is usually carried out using a tablet press or the like. It is preferable to pressurize and mold the tablets, and the tableting pressure at this time is usually about 1 to 3 t/cJ. The shape of the molded product obtained by molding is cylindrical,
It may have any shape, such as a ring shape or a columnar shape, as long as it can be formed into tablets using a normal tablet machine. Further, the size of the molded product is not particularly limited and is determined depending on the size of the reactor and the ease of handling the molded product, but it may be any size that can be formed into tablets with a tablet machine.

On the other hand, since it is preferable that the above-mentioned molded body has a low moisture content, it is desirable that the raw materials, the single metal and the solid fluorine compound, be dried to remove moisture before molding.

Next, a method for producing a gaseous metal fluoride using this compact and F2 gas will be described.

In the present invention, the reactor for reacting the single metal contained in the molded body with the F2 gas is usually made of nickel because of its corrosion resistance against fluorine. There are no particular restrictions on the shape, but a cylindrical shape is preferred for ease of production.
It is convenient and convenient to fill this perforated plate with the above-mentioned molded body and to use it by feeding F2 gas from the bottom. still,
Heating of the reactor can be easily performed by providing a heater or the like on the outside of the cylindrical portion of the reactor.

In the present invention, as described above, a reactor is filled with a molded body made of a single metal and a forming aid, and while the molded body is heated, F2 gas is introduced from the bottom to remove the single metal and F2 gas in the molded body.
A gaseous metal fluoride is produced by reacting with 2, and the reaction temperature naturally varies depending on the type of gaseous metal fluoride to be produced. To illustrate this, the temperatures shown in Table 1 below are suitable.

Table-1 The F2 gas fed into the reactor is dangerous at high concentrations, so it should be diluted with an inert gas such as N2 gas or ^r gas.
It is preferable to use it at a concentration of about 0% by volume.

The pressure during the reaction is not particularly limited and of course may be reduced pressure, but the reaction is usually carried out at a pressure of about normal pressure to 10 kg/cJ. The reaction time may vary depending on the temperature, but is usually 1 to 20
The treatment time is preferably about 2 to 10 hours. The gaseous metal fluoride obtained by the reaction contains the inert gas used to dilute the F2 gas and some unreacted F2 gas, so it is cooled to below the liquefaction temperature of the gaseous metal fluoride. to separate the inert gas and F2 gas.

"Example" Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Dry in advance at 120°C for 2 hours in a N2 gas atmosphere.
Metallic tungsten powder with a purity of 99.9% (iron content: 15%)
0pp+n) and NaF, which was also pre-dried in the same way.
After thoroughly mixing the powder (grade 1 reagent) at a ratio of 1:1 by weight, it was compressed into tablets with a tableting pressure of 2t/cIa using a small tableting machine, with a diameter of 5 and a height of 5. 100 cylindrical molded bodies
I got g. The average compressive strength of this molded body is 270.
kg/cJ, which was extremely high.

Next, this molded body is made of nickel and has an inner diameter of 19 mm and a height of 60 mm.
The mixture was filled in the center of a vertical reactor with a hollow bar. After that, in order to completely remove the moisture in the molded body, while the packed bed of the molded body was heated to about 100°C, normal pressure (h) gas was poured from below at a flow rate of 300 Nynl/min for about 2 hours. After venting the SZ gas for a time, the packed layer of the molded body was
While heating to ~400°C, N2 was added from the bottom of the reactor.
Pg gas at normal pressure with a concentration of about 30% by volume diluted with gas
The gas contained in the ridge generated from the 0 reactor was vented for 3 hours at a flow rate of 00 Nd/win, and the gas contained therein was heated to -80°C.
After the reaction, the inside of the trap was evacuated with a vacuum pump to remove the N2 gas used to dilute the F2 gas and unreacted F2 gas.
t gas was removed.

The amount of WF obtained was 69 g, which was a high yield of 96% based on fluorine. Moreover, the molded body in the reactor maintained its original shape without collapsing.

In addition, when analyzing the content of elemental metals in the collected carcasses, it is difficult to measure the content of elemental tungsten in the ridges. Regarding iron (Fe), ICP
The content was measured by (high-frequency inductively coupled plasma) analysis, and the result was 0.05 pp+w or less. From this result, it is estimated that the scattering of the raw material, tungsten metal, has been substantially prevented.

Examples 2 to 8 Single metals shown in Table 2 were used instead of tungsten as the single metal, and Table 2 was used instead of sodium fluoride as the forming aid.
The solid metal fluorides shown in Table 2 were used in the amounts shown in Table 2, and the tablets were compressed in the same manner as in Example 1 at the tableting pressures shown in Table 2 to obtain molded products in the amounts shown in Table 2. Ta. (The single metal and the molding aid were each dried in the same manner as in Example 1 prior to molding.) The reactor used in Example 1 was filled with the molded product in the amounts shown in Table 2. Various gaseous metal fluorides were obtained in the same manner as in Example 1 by passing F2 gas under the reaction conditions shown in Table 2.

In addition, the drying conditions of the molded body before introducing F2 gas into the reactor are as follows:
This was carried out in exactly the same manner as in Example 1.

Yield, yield, F of the resulting product, gaseous metal fluoride
The e content was as shown in Table 2, and as in Example 1, the yield was high and there was no scattering of single metals. In addition, none of the molded bodies collapsed after the reaction was completed.

Comparative Example 1 After charging 100 g of pre-dried metal tungsten powder, which is the same as that used in Example 1, as uniformly as possible at the bottom of a nickel horizontal reactor with a diameter of 38 mm and a length of 600 mm, the reactor was heated to about 100 g. The reactor was heated to .degree. C. and 82 gas was passed through the left end of the reactor at a flow rate of 300 Nm/win for about 2 hours to dry the metal tungsten.

After stopping the N2 gas ventilation, the metal tungsten layer was heated to the same temperature as in Example 1 (380 to 400"C,
F2 gas diluted with H2 gas was vented from the left end of the reactor under the same conditions as in the example to cool the gases generated from the reactor and collect the gases contained therein.

The amount of WFi obtained was 33g, and the yield was 46% based on fluorine.
This was less than half of that of Example 1. Further, the Fe content in the ridges was 0.9 ppm, and it is presumed that a considerable amount of metallic tungsten powder was mixed in.

"Effects of the Invention" As explained in detail above, in the method of producing gaseous metal fluoride by reacting an elemental metal with F2 gas, conventionally, in order to improve the reaction yield, the elemental metal was used in powder form. However, in the present invention, a solid metal fluoride that does not react with fluorine, preferably its powder, is added and mixed as a forming aid to a single metal, preferably a powdered single metal, and then this is pressurized and molded. This method uses a molded product obtained by using a molded product, which completely prevents the problem of contamination of single metal powder into the gaseous metal fluoride product, which has been a problem in the past. This has made it possible to improve the quality of products.

It should also be noted that, as an effect of the present invention, a significantly higher reaction yield can be obtained compared to conventional methods, even though the single metal is pressurized and molded with the addition of a molding aid. Probably.

Furthermore, since the present invention provides such a high reaction yield,
The reactor can also be small, and since it is made of expensive nickel, it has the advantage of being much cheaper to manufacture than conventional reactors.

Furthermore, solid metal fluorides that do not react with fluorine remain in the molded bodies used in the reaction after the reaction is completed, but these solid gold and hydrofluorides can be reused repeatedly by crushing them. This is also one of the advantages of the present invention.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] (1) In a method of producing a gaseous metal fluoride by reacting an elemental metal with fluorine gas, a solid metal fluoride that does not react with fluorine is added and mixed with the elemental metal as a forming aid in advance, and the mixture is pressurized. - A method for producing a gaseous metal fluoride, which comprises, after molding, bringing the molded product into contact with fluorine gas in a heated state.