JPH11323451A - Production of high purity titanium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor progress of a refining reaction and to stably produce high purity titanium by measuring the change in the weight of crude titanium used for precipitating titanium with iodine in a reaction vessel by a gravimeter provided on the outer part of the reaction vessel in the process of the reaction. SOLUTION: In a reaction vessel 1 capable of being sealed, a filament 2 made of high purity Ti wire is set so as to be capable of electric heating, and on the circumferences, crude Ti materials 3 so as to be formed into raw materials are arranged with prescribed gaps. The inside of the reaction vessel 1 is evacuated, the crude Ti materials 3 are heated to about 200 to 400 deg.C by a heater 4 for heating the reaction vessel, and the filament 2 has been electrically heated to about 1300 to 1500 deg.C, which is introduced from a gaseous iodine source gas introducing tube 8 into the reaction vessel 1, and the reaction vessel 1 is sealed. The crude Ti materials 3 are allowed to react with iodine to form TiI4 , and metallic Ti is precipitated into the surface of the filament. The crude Ti materials 3 are suspended from the outer part of the reaction vessel 1 by a suspending rod or held by a supporting rod, each is fitted with a gravimeter, and the change of the weight of the crude Ti materials 3 is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity titanium using iodine, which is generally called an iodine method.

[0002]

2. Description of the Related Art Recent LSIs (Large Scale Integrated Circuits: Large)
Due to an increase in the degree of integration of Scale Integration, the use of refractory metals such as molybdenum (Mo), tungsten (W), titanium (Ti), and silicides thereof as materials for electrodes and wirings is being promoted. This is because fine processing can be performed with high precision, and among these metals, Ti is considered to be the best in terms of specific strength, workability, and corrosion resistance. However, in such a case,
In order to suppress signal delays and circuit malfunctions, extremely high purity is required.

[0003] Metallic Ti is usually produced from oxide ore to TiC.
to produce a l _4, it is common to manufacture the Mg reduction method is said to Kroll process by distillation purification. For ordinary applications, metal Ti with sufficiently high purity is obtained by this method, but for LSIs, ultra-high purity from four nines (99.99%) to six nines (99.9999%) is required. . In order to obtain such ultrahigh-purity Ti, a method of thermally decomposing Ti, which is referred to as iodine method, as titanium tetraiodide (TiI ₄ ) is mainly employed.

FIG. 1 is a schematic diagram showing an example of an apparatus for a purification method using iodine, and an outline of the method will be described with reference to FIG. In a container 1 that can be sealed, a filament 2 made of, for example, high-purity Ti
Is provided, and a crude Ti material 3 serving as a raw material is placed around it so as to surround it. The gap between the filament and the coarse Ti material is about 5 to 40 mm. After evacuating the container to a vacuum of 10 ⁻³ Torr or less, the crude Ti in the container is heated by an external heater.
4 to 200-400 ° C, filament 2 from 1300 to 1
Heat to 500 ° C before introducing gaseous iodine (I ₂ )
Introduce into the container from 8 and seal the container. I ₂ is crude Ti material 3
Reacting with TiI ₄ is possible, because TiI ₄ has a high enough vapor pressure at this temperature, when diffuses to the filament 2 is deposited substrate, metal Ti is deposited by thermally decomposing at the surface.

[0005] This utilizes the following reversible reaction in principle.

Ti + 2I ₂ = TiI ₄ (1) Here, Ti is a solid, and since I ₂ and TII ₄ are gases, the partial pressures of these gases in the gas phase in an equilibrium state are denoted by P _I and P _T4 , respectively. Then, the equilibrium constant K _{1 for} this reaction can be expressed as K ₁ = P _T4 / P _I ² (2). K ₁ is a constant determined by the temperature, and in the reaction of equation (1), K ₁ decreases as the temperature increases. The value of K ₁ is large at low temperatures P _T4 for P _I high, namely (1) TiI ₄ the direction of the iodide reaction proceeds to increase the expression,
Since K ₁ is small at a high temperature P _I P _T4 is lower than the state,
That is, the precipitation reaction of Ti in the left direction of equation (1) in which TiI ₄ decreases and I ₂ increases increases.

Accordingly, is opposed with a space in a relatively low temperature of the crude Ti material 1 and the hot filament 2 as shown in FIG. 1, when there I ₂ is present, the low temperature of the crude Ti
The side reacts with I ₂ to produce TiI ₄ , but its attained equilibrium concentration ratio is too high with respect to the high temperature of the filament, so that TiI ₄ decomposes on the filament to precipitate Ti, and I ₂ discharge. That is, since the generation and decomposition of TiI ₄ proceed simultaneously, a steady state in which the concentration ratio of I ₂ and TiI _{4 in} the space is maintained at a constant value is maintained. I ₂ in the gas phase forms a TiI ₄ reacts with coarse Ti, when TiI ₄ on the filament is decomposed, the resulting I ₂ is the crude Ti
Then, it is combined with Ti again and reused because it is circulated and used, so that the purification reaction constantly proceeds in a form in which the crude Ti of the raw material decreases and gradually moves onto the filament and precipitates. Here, since I ₂ mainly reacts with Ti in the crude Ti, impurities are left behind, and only TiI ₄ is decomposed on the filament and other compounds are not decomposed. As a result, high-purity Ti is obtained. become.

One of the present inventors raised the heating temperature of crude Ti to 700 to 900 ° C. to improve the above-mentioned purification method and to produce Ti with higher purity more efficiently. And an improved method utilizing a lower titanium iodide such as TiI ₂ was proposed in Japanese Patent Application Laid-Open No. 3-215633. In this case, while supplying TiI ₄ into the reaction vessel, while exhausting gas on the other hand, impurities in the gas phase are eliminated, and Ti with higher purity is obtained. Further, as a result of the temperature decrease of the deposition substrate, a method of using a high-purity Ti tube instead of a filament as the deposition substrate and indirectly heating the inside from the inside to increase the deposition area and improve the productivity is also disclosed in Japanese Patent Application Laid-Open No. HEI 4 (1994) -104605. -246136.

As described above, the purification reaction is performed under a reduced pressure of 1 Torr or less in a high-temperature closed vessel for the purpose of maintaining the vapor pressure of TiI ₄ or lower titanium iodide, promoting the reaction, removing impurities, and the like. For this reason, the state during the purification is hardly observed, and in the case of direct electric heating, it can be somewhat inferred from the decrease in the electric resistance of the filament. I just guessed the course. However, grasping the progress of the purification process is extremely important for ensuring the quality of the resulting high-purity Ti, efficiently using the purification equipment, and further preventing abnormal purification reaction progress.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for monitoring the progress of a purification reaction in the course of a titanium purification process using iodine. Is to be able to carry out the manufacturing.

[0011]

SUMMARY OF THE INVENTION Purification using iodide proceeds by depositing high purity Ti on a high temperature substrate. Therefore, if the weight of the deposited substrate during the reaction can be measured, it is considered that the progress of the reaction can be grasped. However, the deposition substrate is provided with a power distribution body, an electric insulator, and a seal for guiding the current into the decompression vessel, etc., which carry a large current for high-temperature heating. There are various difficulties in measuring the substrate weight. However, the phenomenon occurring in this closed container is that Ti is precipitated on the substrate by the purification reaction and its weight increases, and the crude Ti reacts with iodine and decreases as TiI ₄ or lower iodide. . When the reaction proceeds in a steady state, the amount of precipitated Ti is considered to be substantially equal to the amount of decrease in crude Ti. However, if the gas composition of the atmosphere in the initial stage of the refining does not reach a steady state, the amount of precipitation may not match the amount of decrease in crude Ti, but this is a temporary phenomenon.
In addition, TiI ₄ may be introduced into the reaction vessel as an iodine source, and it is conceivable that the Ti component is precipitated. However, the introduced amount of TiI ₄ is operated such that an amount corresponding to the TiI ₄ is excluded from the reaction vessel. In addition, the amount of introduction can be measured.

Therefore, an attempt was made to grasp the progress of the purification reaction by measuring the weight loss of the crude Ti. Since the crude Ti is simply placed in the reaction vessel, its weight measurement is easier than that performed on the deposition substrate. For measuring the weight of the coarse Ti, the coarse Ti in the reaction vessel was held from outside the vessel, and a weighing scale was attached to the holding mechanism. Thus, a method of continuously measuring the weight of crude Ti during the purification reaction was examined, and as a result of producing high-purity Ti, it was confirmed that the progress of purification could be sufficiently grasped. In particular, the change in the purification rate with the progress of the precipitation of Ti became apparent,
By adjusting the heating of the deposition substrate while observing the change in the amount of deposition, the purification reaction can be efficiently performed.

That is, the gist of the present invention is to provide (1) a method for purifying titanium using iodine, wherein a change in weight of crude titanium in a reaction vessel is measured during the reaction; (2) The method for producing high-purity titanium according to (1), wherein the crude titanium is suspended or supported from outside the reaction vessel, and the weight of the crude titanium is measured by attaching a weighing scale to the suspension or support. is there.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Crude Ti as a raw material is a simple metal,
A sponge titanium, a cut piece or the like is compressed, or a small piece is placed in a basket made of a corrosion-resistant metal such as Mo, and the like is placed in the reaction vessel. Any method can be used as long as the change in weight of the crude Ti can be measured with high accuracy.
And a weighing scale is installed on the holding mechanism.

For example, as shown in FIG.
The crude Ti3 is suspended at 10, and the suspension rod is attached to the weighing scale 12 so that it can be weighed by being sealed with a vacuum seal 11. Hot I
₂ is highly corrosive, so the part inside the reaction vessel connected to the crude titanium of the suspension jig is made of corrosion-resistant metal such as Mo,
A heat-resistant material similar to the inside of the reaction vessel whose surface is lined with Au, Pt, Ta, or the like is used. As the vacuum seal 11, for example, a Viton O-ring or the like is applied. In the case of sealing with an O-ring, it is necessary to tighten sufficiently to prevent atmospheric leakage into the depressurized reaction vessel, and water-cooling must be performed so that the temperature of the sealing portion does not rise.
However, since a certain amount of friction cannot be avoided, errors due to the frictional resistance are reduced as much as possible. It is also desirable to take care to reduce the diameter of the rod so that it is not thicker than necessary for suspension, and not to tighten too much. Bellows may be used for the vacuum seal of the suspension rod.

The crude Ti in the reaction vessel may be supported from below rather than suspended from above, and a weighing scale may be installed thereon.
For example, a schematic diagram is shown in FIG. 3, where the crude Ti3 is held by a support and a support rod 13, and the support rod is sealed with a vacuum bellows 14 so that it can be weighed by a weighing scale 12 outside the reaction vessel. The support jig, the support rod, the bellows, and the like are provided with a corrosion-resistant material or a surface-lined portion in contact with the atmosphere in the container.
Also in this case, if the frictional resistance can be sufficiently reduced, a seal using an O-ring may be used.

[0017]

FIG. 2 is a schematic view of a reaction vessel 1 having an inner diameter of 250 mm.
The filament 2 for deposition has a diameter of 1 mm and an effective length of 1000
5 kg of titanium and 5 kg of titanium sponge placed in a cylindrical cylindrical basket of Mo as crude Ti3 were placed in the reaction vessel. Crude Ti
The wire baskets with are suspended at four places with Mo wires 10 having a diameter of 1 mm, and the Mo wires are sealed with O-rings 11 and are taken out of the furnace, and are weighed by a weighing scale 12 (minimum scale 10 g, maximum 10 kg). And coarse T
The change in weight of i3 can be measured.

After the inside of the furnace is evacuated, the crude Ti is supplied to an external heater.
4 to 800 ° C. Filament 2 is set to 1200 ° C by energizing heating. In this state, 10 g of TiI ₄ gas is added.
/ h introduced.

Purification was performed for 100 hours under the same conditions as in the prior art, the filament was taken out of the reactor, and the weight was measured. As a result, 3.3 kg of high-purity Ti was obtained. FIG. 4 shows the results of the measurement of the weight change during that time according to the method of the present invention as conventional conditions. Next, in the same equipment as above, after starting the reaction under the same conditions, while monitoring the weight change, increase the crude Ti temperature, increase the filament current, etc., and adjust so that the deposition rate does not decrease significantly. As a result, the same 3.3 kg of high-purity Ti could be obtained in 73 hours, as shown as an improvement condition in FIG. in this way,
Since the progress of the reaction can be known, automatic control of the conditions during the purification reaction and the like can be applied by using the information, thereby further improving the productivity.

[0020]

According to the present invention, in the method of purifying titanium using iodine, the progress of the purification reaction of high-purity titanium can be monitored, so that the conditions of the purification reaction can be controlled based on the data. Production efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating the structure of a reaction apparatus used for producing ordinary high-purity Ti using iodine.

FIG. 2 is a diagram schematically illustrating a method of measuring a change in weight of crude Ti during a reaction by suspending from above.

FIG. 3 is a diagram schematically illustrating a method of measuring a weight change of crude Ti during a reaction by supporting from below.

FIG. 4 is a diagram showing a change in weight of crude Ti during a purification reaction.

[Explanation of symbols]

1 Reaction vessel 2 Precipitated substrate (filament) 3 Crude Ti material 4 Heater for heating the reaction vessel 6 Vacuum exhaust hole 8 Iodine source gas introduction pipe 10 Suspension rod 11 O-ring seal 12 Weight scale 13 Support rod 14 Bellows

Claims (2)

[Claims] 1. A method for purifying titanium using iodine, wherein a change in weight of crude titanium in a reaction vessel is measured during the reaction. 2. The method for producing high-purity titanium according to claim 1, wherein the crude titanium is suspended or supported from outside the reaction vessel, and the weight of the crude titanium is measured by attaching a weighing scale to the suspension or support. .