JPH07173551A - Method for refining high-purity titanium - Google Patents

Abstract

PURPOSE:To refine high-purity titanium through one reaction by using titanium tetraiodide as the gaseous reactant. CONSTITUTION:A raw material part 2a, an intermediate deposition part 2b and a final deposition part 2c are arranged in a reactor 1. The heating temp. is successively raised from the raw material part 2a toward the final deposition part 2c, and titanium tetraiodide is supplied into the reactor 1. The raw material part 2a is etched, and high-purity titanium is deposited on the surface of the intermediate deposition part 2b on the raw material part 2a side. The surface of the intermediate deposition part 2b on the final deposition part 2c side is etched, and high-purity titanium is further deposited on the final deposition part 2c.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying high-purity titanium by the iodine method.

[0002]

2. Description of the Related Art Due to the recent rapid increase in the degree of integration of LSIs, the electrode materials used in LSIs are shifting to those having higher purity and higher melting points. For example, in order to solve the signal delay due to the thinning of the electrode wiring, a high-purity / high-melting-point metal material having a lower resistance has been attracting attention in place of polysilicon which has been widely used conventionally. Examples of high-purity and high-melting point metal materials used for LSI electrodes include molybdenum, tungsten, titanium, and their silicides.
Among them, titanium is particularly promising because it has excellent specific strength, workability and corrosion resistance.

In order for titanium to be used as an electrode material for semiconductors, high purity is essential. The iodine method is typical as a refining method for obtaining high-purity titanium. In the conventional high-purity titanium purification method by the iodine method,
The following reaction proceeds in the reactor. Crude Ti + 2I ₂ → TiI ₄ (synthesis reaction) TiI ₄ → high-purity Ti + 2I ₂ (pyrolysis reaction)

However, the temperature of the synthetic reaction is 200-400.
Since it is as low as ℃, by-products such as high melting point lower titanium iodide (TiI ₂ , TiI ₃ ) are easily generated in the solid state.
The generated lower titanium iodide covers the surface of the crude titanium and prevents the reaction from continuing. On the other hand, the temperature of the thermal decomposition reaction is 1300 to 1
The temperature is as high as 500 ° C., which promotes thermal decomposition of metal impurities contained in titanium tetraiodide as a titanium deposition gas source, and becomes a cause of limiting purification of precipitated titanium to high purity. Because of these
It was impossible to continuously deposit ultra-high purity titanium called 6-nine for a long time. Hereinafter, the 6-nine-level purity is referred to as 6N grade, and similarly, the 5-nine level and 4-nine level purities are referred to as 5N-grade and 4N-grade, respectively.

In order to solve the above-mentioned problems of the conventional method, the applicant of the present invention said, "Keeping crude titanium in a reactor and reacting titanium tetraiodide with the crude titanium to synthesize lower titanium iodide, A method for purifying high-purity titanium, in which the synthesized lower titanium iodide is thermally decomposed to precipitate high-purity titanium, was first developed and proposed in JP-A-3-215633.
In this new method, the following reactions proceed in the reactor. Crude Ti + TiI ₄ → 2TiI ₂ (synthesis reaction) 2TiI ₂ → high-purity Ti + TiI ₄ (pyrolysis reaction)

The synthesis of lower titanium iodide by the reaction of crude titanium and titanium tetraiodide is carried out at about 700 to 900 ° C., which is higher than the synthesis of titanium tetraiodide, and the lower titanium iodide is directly in a gaseous state. can get. Further, at the synthesis temperature of lower titanium iodide, titanium tetraiodide produced by unreacted and thermal decomposition is also maintained in a gas state. Therefore, there is no fear that the iodide gas (lower titanium iodide and titanium tetraiodide) in the reactor will cover the surface of the crude titanium, and the synthesis reaction will continue stably.

The synthesized lower titanium iodide is more easily thermally decomposed than titanium tetraiodide and has a thermal decomposition temperature of 1100 to 13
It can be lowered to around 00 ° C. Therefore, the thermal decomposition of the metal impurities contained in the lower titanium iodide as the titanium deposition gas source is prevented, and there is no risk that the metal impurities are mixed into the deposited titanium.

[0008]

However, in the purification of this new high-purity titanium, the high-purification rate obtained in one reaction process is about 1/10 to 1/30, and the high-purity of 5N class is high. Even when purifying titanium, raw material titanium having a relatively high purity of 4N grade is required. High-purity titanium refined from 3N-grade crude titanium remains in 4N-grade. Therefore, in the case of purifying 5N-grade high-purity titanium from 3N-grade crude titanium, the reaction process needs to be repeated twice, which causes problems such as reduction in yield and increase in purification cost.

An object of the present invention is to solve the above-mentioned problems and to provide a method for purifying high-purity titanium capable of efficiently producing ultra-high-purity titanium of 6N grade or higher from low-purity raw material titanium in one purification process. To provide.

[0010]

According to the method for purifying high-purity titanium of the present invention, a raw material part made of titanium, one or more intermediate depositing parts, and a final depositing part are sequentially arranged in the same reactor. Then, titanium tetraiodide is supplied into the reactor, and each part is heated and held so that the holding temperature becomes higher from the raw material part to the final precipitation part in the order of arrangement.

It is desirable that both the intermediate depositing portion and the final depositing portion, or only the intermediate depositing portion be made of titanium together with the raw material portion, and the purity thereof be increased from the raw material portion to the final depositing portion in the order of arrangement.

More preferably, the space on the raw material side of the intermediate depositing portion, the space on the final depositing portion side, and the space between the intermediate depositing portions when a plurality of intermediate depositing portions are used are made independent from each other, Prevent gas from flowing between spaces.

FIG. 1 shows a particularly preferred embodiment of the present invention.

In the cylindrical reactor 1, a disk-shaped raw material part 2a made of lower titanium, a disk-shaped intermediate precipitation part 2b made of titanium of higher purity than that, and a titanium of higher purity are used. And the disc-shaped final deposition portion 2c are sequentially arranged from the bottom to the top with a space therebetween.

Here, the outer diameters of the raw material portion 2a, the intermediate precipitation portion 2b, and the final precipitation portion 2c are smaller than the inner diameter of the reactor 1.
Therefore, there is a gap outside each part. And
In particular, by closing the gap between the intermediate precipitation portion 2b and the reactor 1 with the annular partition plate 4, the inside of the reactor 1 is filled with the intermediate precipitation portion 2b.
The space 3a on the raw material part 2a side and the final deposition part 2 are sandwiched between
It is divided into a space 3c on the c side.

On the other hand, outside the reactor 1, an annular first heater 5a for heating the raw material portion 2a, an annular second heater 5b for heating the intermediate depositing portion 2b, and an annular heater for heating the final depositing portion 2c. No. 3 heater 5c is located on the outer peripheral side of each part and is arranged in three stages.

To carry out purification, for example, 3N grade titanium is selected as the raw material part 2a and 4N grade titanium is selected as the intermediate precipitation part 2b. In addition, as the final deposition portion 2c, 5
Select N grade titanium. Then, the spaces 3a and 3c are
Through the traps 6a and 6c, the vacuum pumps 7a and 7c reduce the pressure to a predetermined degree of vacuum.

Next, the raw material portion 2a, the intermediate depositing portion 2b and the final depositing portion 2c are independently heated and held by the heaters 5a, 5b and 5c. The heating and holding temperature is Ta <Tb <Tc, where Ta, Tb, and Tc are the temperatures of the raw material part 2a, the intermediate precipitation part 2b, and the final precipitation part 2c. That is, the raw material part 2a
To the final precipitation portion 2c in the order of arrangement, the temperature is increased. Then, while maintaining the vacuum degree and temperature, titanium tetraiodide gas is gradually supplied into the spaces 3a and 3c from the TiI ₄ supply units 8a and 8c through the flowmeters 9a and 9c.

As a result, the space 3a, that is, the raw material part 2
In the space on the a side, of the two materials facing each other, the intermediate precipitation portion 2b is higher in temperature than the raw material portion 2a, so that a synthesis reaction of lower Ti + TiI ₄ → 2TiI ₂ occurs near the raw material portion 2a, Corresponding to the intermediate precipitation portion 2b
In the vicinity of the surface of the raw material portion 2a side, a thermal decomposition reaction of 2TiI ₂ → intermediate Ti + TiI ₄ occurs.

As a result, the raw material portion 2a is etched, and highly purified titanium is deposited on the surface of the intermediate deposition portion 2b on the raw material portion 2a side. The high purification rate here is 1
/ 10 to 1/30. Therefore, when the raw material portion 2a is 3N-grade titanium and the intermediate precipitation portion 2b is 4N-grade titanium, the intermediate precipitation portion 2b is changed to the raw material portion 2 as the raw material portion 2a is etched.
Precipitation grows on the a side.

On the other hand, the space 3c, that is, the final deposition portion 2c
In the space on the side, of the opposed two materials, for towards the final deposit part 2c from the intermediate deposit part 2b is hot, near the surface of the final deposit part 2c of the intermediate deposit part 2b is intermediate Ti + TiI ₄ → 2TiI _Two synthetic reactions occur. Corresponding to this, the final deposition portion 2b
In the vicinity of, a thermal decomposition reaction of 2TiI ₂ → higher Ti + TiI ₄ occurs.

As a result, the surface of the intermediate deposit 2b on the final deposit 2c side is etched, and highly purified titanium is deposited on the final deposit 2c. The high purification rate here is also 1/10 to 1/30. Therefore, when the intermediate precipitation portion 2b is 4N-class titanium and the final precipitation portion 2c is 5N-class titanium, the final precipitation portion 2c is deposited and grown as the surface of the intermediate precipitation portion 2b on the final precipitation portion 2c side is etched.

That is, the reaction between these iodides and titanium depends on titanium iodide or iodine partial pressure, composition and temperature.
Either an etching reaction or a precipitation reaction can occur. When the two plates are faced to each other as described above, the factors that cause the precipitation and etching of each titanium are:
The temperature difference is a more important factor than the absolute temperature. That is, Ti in the high temperature region causes a precipitation reaction and Ti in the low temperature region causes an iodide reaction. Therefore, 2a, 2b
In between, 2a is an iodination reaction, 2b is a precipitation reaction, and 2b,
Between 2c, 2b is an iodide reaction and 2c is a precipitation reaction, and the respective reactions proceed.

Thus, the raw material part 2a continues to be consumed by etching. The intermediate precipitation portion 2b continues to grow on the raw material portion 2a side, but continues to be consumed on the final precipitation portion 2c side, and the volume can be maintained apparently constant by setting the operating conditions. The final precipitation portion 2c continues only precipitation growth. Due to the two-step reaction mediated by this intermediate precipitation part 2b, the raw material part 2a becomes (1/10
It is highly purified to 1/30) ² and deposited in the final deposition portion 2c.

Therefore, if 3N grade titanium is used as the raw material part 2a, the titanium can be converted to 5N in one reaction process.
It can be refined to grade titanium. Higher purity titanium can be obtained by increasing the grade of the raw material part 2a or increasing the number of intermediate precipitation parts 2b to carry out the reaction in three or more stages.

In each reaction in the spaces 3a and 3c, the synthesis temperature can be raised and the thermal decomposition temperature can be lowered as described above, so that the reaction can be continued for a long time and impurities can be suppressed.

The gas used in each reaction is a vacuum pump 7.
It is gradually discharged to the outside of the spaces 3a and 3c by a and 7c, and is collected in the traps 6a and 6c.

In the present embodiment, titanium is required for the intermediate precipitation portion 2b to be etched, and the intermediate precipitation portion 2 is required.
Titanium of approximately the same purity as the titanium deposited in b is desirable, but it is not necessary to use titanium in the final deposited portion 2c that is not subjected to etching, and there is no danger of contaminating the deposited titanium, such as Ta, Mo, W, etc. It is also possible to use melting point materials.

As for the heating of each part, direct heating by energization may be adopted instead of external heating, or both may be used in combination.

[0030]

As described above, in the method for purifying high-purity titanium of the present invention, high-purity titanium can be purified in one reaction process by the multistage precipitation reaction from the raw material part to the final precipitation part through the intermediate precipitation part. It will be possible. Further, it becomes possible to reduce the purity of the raw material titanium.

The temperatures Ta, Tb, and Tc of the raw material portion, the intermediate precipitation portion, and the final precipitation portion must satisfy the relationship of Ta <Tb <Tc, but the maximum temperature is 1300 to suppress thermal decomposition of metal impurities. It is desirable to limit the temperature to below ℃, and to keep the minimum temperature above 700 ℃ in order to suppress the condensation reaction of lower titanium iodide (TiI ₂ , TiI ₃ ).

Therefore, Ta, Tb, and Tc are each 700
<Ta <900 ° C, 900 <Tb <1100 ° C, 110
Most preferably, 0 <Tc <1300 ° C. Under such temperature conditions, the iodide reaction in the raw material part 2a, the precipitation reaction in the final precipitation part, and either of the reactions in the intermediate precipitation part proceed efficiently.

Temperature difference between each part (Tc-Tb, Tb-T
A) is preferably 30 to 300 ° C. If the temperature is lower than 30 ° C. or higher than 300 ° C., the synthesis reaction and the thermal decomposition reaction hardly occur in one direction.

Further, the heating and holding temperature of each part and the amount of raw material gas supplied to each space are preferably adjusted so that etching and deposition are balanced in the intermediate deposition part and the volume of the intermediate deposition part is kept constant. Then, the reaction is continued while the supply of the low-grade titanium as the raw material is continued.

The vacuum degree in each space is preferably 10 ^-1 to 10 ^-3 Torr. If it is less than 10 ^-3 Torr, precipitation of titanium is less likely to occur, and if it exceeds 10 ^-1 Torr, diffusion of titanium iodide is rate-determining and the precipitation rate is reduced.

[0036]

EXAMPLES Examples of the present invention will be described below.

The present invention was carried out in the manner shown in FIG. A titanium plate having the composition shown in Table 1 was used for the raw material part, the intermediate precipitation part, and the final precipitation part. The diameter of the titanium plate was 100 mm. The heating and holding temperature of each part is Ta = 800 ° C. and Tb = 1000.
C and Tc = 1150 ° C. External heating by electric resistance heating was used for heating. The degree of vacuum in each space is about 10 ^-2 Torr
And The amount of titanium tetraiodide gas supplied is 30 g in each space.
/ H.

As a result of continuing the reaction for 100 hours, the thickness of the raw material portion was reduced by 6 mm, and conversely, the thickness of the final deposited portion was increased by 6 mm. On the other hand, the thickness of the intermediate deposited portion did not differ from that before the reaction. Table 1 also shows the analysis results of titanium deposited in the final deposited portion.

[0039]

[Table 1]

0.2 kg of 6N grade titanium was purified from 4N grade titanium in one reaction process (100 hours).

[0041]

As is apparent from the above description, the method for purifying high-purity titanium according to the present invention uses titanium tetraiodide as a reaction gas, and the reaction is performed in multiple stages.
High-purity purification is possible in one reaction process. Therefore, highly pure titanium can be purified economically. Further, since the grade of the raw material titanium can be reduced, the economical efficiency can be improved also from this point.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of the present invention.

[Explanation of symbols]

1 Reactor 2a Raw material part 2b Intermediate precipitation part 2c Final precipitation part 3a, 3c Space 5a, 5b, 5c Heater 7a, 7c Vacuum pump 8a, 8c TiI ₄ feeder

Claims (4)

[Claims] 1. A raw material part made of titanium, one or a plurality of intermediate precipitation parts, and a final precipitation part are sequentially arranged in the same reactor, and titanium tetraiodide is supplied into the reactor. A method for purifying high-purity titanium, characterized in that each part is heated and held so that the holding temperature becomes higher in the order of arrangement from the raw material part to the final precipitation part. 2. The holding temperature of each part is controlled within the range of 700 to 1300 ° C., and the temperature difference between the parts is 30 to 300 ° C.
The method for purifying high-purity titanium according to claim 1, wherein the purification method is controlled within the range. 3. Along with the raw material part, both the intermediate depositing part and the final depositing part or only the intermediate depositing part are made of titanium, and the purity is increased in the order of arrangement from the raw material part to the final depositing part. The method for purifying high-purity titanium according to claim 1 or 2. 4. A space on the side of the raw material part from the intermediate precipitation part, a space on the side of the final precipitation part, and a space between the intermediate precipitation parts when a plurality of intermediate precipitation parts are used are made independent of each other, and each space is separated. The method for purifying high-purity titanium according to claim 3, wherein gas is prevented from flowing between them.