JPH10298674A - Method for refining high purity titanium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the surface areas of precipitating substrates and suppress the reduction of the yield while securing an effective space in a reaction vessel by arranging a plurarity of in depend ant hollow precipitating substrates in parallel in a reaction vessel in which high purity titanium is precipitated over the surfaces of the substrates by an iodine method. SOLUTION: Coarse titanium 7 is arranged around a plurality of hollow precipitating substrates 5 sagged in a reaction vessel 1. The inside of the reaction vessel 1 is evacuated and heated, and the vapor of titanium tetraiodide is introduced into the reaction vessel 1. The hollow precipitating substrates 5 are heated by a heater. The coarse titanium 7 in the reaction vessel 1 is converted into titanium diiodide, which is thermally decomposed on the surfaces of the hollow precipitating substrates 5 to convert into high purity titanium. The iodizing reaction and thermal decomposing reaction of titanium one-sidedly progress and allow to continue the precipitation of high purity titanium on the surfaces of the hollow precipitating substrates 5. Even in the case a part of the hollow precipitating substrate 5 is made a defective, th other precipitated articles can be adopted as products to improve the yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying high-purity titanium by an iodine method.

[0002]

2. Description of the Related Art In recent years, thin films of high-purity titanium have begun to be used as gate electrode materials, diffusion barrier materials, wiring materials and the like in semiconductor devices such as LSIs and ULSIs. This high-purity titanium thin film is usually formed by sputtering, and its sputtering target is generally manufactured from melting, forging, rolling, and heat-treating a high-purity titanium purified by an iodine method. .

In the purification of high-purity titanium by the iodine method used here, crude titanium having a low purity and a titanium substrate having a high purity are accommodated in a reaction vessel and heated in various heating modes by a synthesis reaction and a thermal decomposition reaction. Is to deposit high-purity titanium on the titanium substrate thus formed. Since the iodine reaction here is a diffusion-controlled reaction, increasing the surface area of the deposition substrate has a great effect in terms of accelerating the thermal decomposition rate.

[0004] From this viewpoint, the present applicant has previously proposed changing the deposition substrate from a conventional linear filament to a tube (Japanese Patent Publication No. 7-62183), and succeeded in significantly increasing the production amount. I have.

[0005]

When a tubular substrate is used as the deposition substrate, the diameter of the substrate must be increased in order to further improve the productivity. However, when the tube diameter is increased, the surface area increases by the first power, whereas the volume occupied by the base increases by the second power. Therefore, the ratio of unnecessary space in the reaction vessel increases with an increase in the tube diameter, and the productivity per unit volume decreases.
It is difficult to increase the tube diameter more than twice.

Therefore, even if a tubular deposition substrate is used, it is difficult to further improve productivity.

When a tubular deposition substrate is used, since accurate temperature control is possible by indirect heating,
It is possible to react for a long time, and in actual operation, the reaction is continued for several days. However, as the continuous operation time becomes longer, the frequency of occurrence of quality contamination (occurrence per batch) due to corrosion, vacuum leak, and the like also increases. If quality contamination occurs during continuous operation, the refined product becomes a defective product that cannot be used as a product, and all operations for several days become meaningless. As a result, the yield is significantly reduced.

An object of the present invention is to increase the surface area of a deposition substrate while securing an effective reaction space in a reaction vessel, and to effectively suppress a decrease in yield due to generation of defective products. An object of the present invention is to provide a method for purifying titanium.

[0009]

According to the present invention, there is provided a method for purifying high-purity titanium, comprising the steps of: placing crude titanium and a deposition substrate in a reaction vessel; and depositing the high-purity titanium on the substrate surface by an iodine method. The method is characterized in that a plurality of independent hollow deposition substrates are arranged in parallel in the reaction vessel.

When a plurality of hollow deposition substrates are arranged in parallel in a reaction vessel, assuming that the total volume of the space occupied by the deposition substrates is the same, the larger the number of substrates, the smaller the individual substrates, but the total surface area increases. I do. Therefore, by arranging a plurality of hollow deposition substrates in parallel in the reaction vessel, an effective reaction space in the reaction vessel is secured, the surface area of the deposition substrates is increased, and productivity is improved.

In addition, even if defective deposits occur on a specific depositing substrate during continuous operation, other deposits can be used as products. It doesn't make sense, and the yield improves.

In the method for purifying high-purity titanium according to the present invention, a plurality of hollow deposition substrates are symmetrically arranged with respect to the center of the reaction vessel in order to equalize the temperature between the substrates and stabilize the reaction in each substrate. It is preferable to arrange them.

When the number of substrates is two, hollow deposition substrates are disposed at two positions sandwiching the center of the reaction vessel, so that useless space exists in the reaction tube and the volume utilization rate is low. . On the other hand, if it is 5 or more, disassembly and assembly are complicated, and the efficiency is reduced. Therefore, the number of substrates is preferably 3 to 4.

Regarding the shape of the hollow precipitation substrate, a circular tube having a circular cross section is preferable for uniform deposition conditions on the surface.

The thickness of each substrate is appropriately selected according to the number thereof so as to secure a sufficient reaction space between adjacent substrates.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic structure of a purification apparatus suitable for carrying out the method for purifying high-purity titanium of the present invention, and FIG. 2 is a cross-sectional view showing an arrangement of coarse titanium and a hollow precipitation substrate in a reaction vessel. FIG.

The reaction vessel 1 is a cylindrical airtight vessel made of stainless steel or the like, and is inserted into the heating furnace 2.
A lid 4 is placed on the reaction vessel 1 via an exhaust chamber 3.
Are connected. The lid 4 has a hollow structure which also serves as an exhaust chamber for a hollow deposition substrate described later. A titanium tetraiodide supply device 8 is connected to the bottom of the reaction vessel 1, and a trap 9 is connected to the exhaust chamber 3.

Inside the reaction vessel 1, three hollow deposition substrates 5, 5, 5 each composed of a high-purity titanium circular tube are arranged, and are formed in a plate shape so as to surround each hollow deposition substrate 5. A large number of coarse titanium 7, 7,... Are arranged.

The three hollow deposition substrates 5, 5, 5 are symmetrically arranged at 120 ° intervals around the center of the reaction vessel 1,
It is held in the reaction vessel 1 by being hung on the lid 4. The inside of each hollow precipitation substrate 5 communicates with a cover 4 having a hollow structure also serving as an exhaust chamber, and a heater 6 such as a carbon heater is provided inside the cover 4.
The heater 6 is connected to an external power supply via the inside of the lid 4 having a hollow structure.

A large number of coarse titaniums 7, 7... Are cast materials (ingots) obtained by dissolving low-purity sponge-like titanium, and are provided around each of three hollow precipitation substrates 5, 5, 5. The three hollow deposition substrates 5, 5 surround the hollow deposition substrate 5.
It is hung on the lid 4 together with 5 and 5.

In operation, after assembling the refining apparatus as shown in FIGS. 1 and 2, the inside of the reaction vessel 1 is evacuated to a predetermined degree of vacuum through the exhaust chamber 3 and the trap 9 and also serves as an exhaust chamber. The inside of each of the hollow deposition substrates 5, 5, 5 is evacuated to a predetermined degree of vacuum through the lid 4 having a hollow structure.

Further, the inside of the reaction vessel 1 is heated to a predetermined temperature from the outside by the heating furnace 2, and the three hollow deposition substrates 5, 5, 5 are heated to the predetermined temperature from the inside by the heaters 6.

In this state, the titanium tetraiodide (melting point: 428 K) distilled and purified is evaporated by the titanium tetraiodide supply device 8 and introduced into the reaction vessel 1. At this time, the inside of the reaction vessel 1 is continuously evacuated to maintain a predetermined degree of vacuum.

The titanium tetraiodide introduced into the reaction vessel 1 converts the crude titanium 7 in the reaction vessel 1 into titanium diiodide. It is thermally decomposed on each surface and deposited on each surface as high-purity titanium. The iodination reaction and the thermal decomposition reaction of titanium proceed unidirectionally due to the temperature difference, and continue to deposit high-purity titanium on the surfaces of the hollow deposition substrates 5, 5, and 5.

The titanium iodide and iodine after the reaction are cooled and recovered in the trap 9, and only titanium tetraiodide is reused after distillation.

According to such a method for purifying high-purity titanium, the three hollow deposition substrates 5, 5, 5
Is arranged, the total surface area of the deposition substrate is increased, and the productivity is improved.

That is, when the height of the deposition substrate is represented as H and the volume of the space occupied by the deposition substrate is represented as V, the total surface area of the deposition substrate is 2 × when the number of the deposition substrate is one. (V / πH) ^1/2 × π × H, but when there are three precipitation substrates, it becomes 3 × 2 × (V / 3πH) ^1/2 × π × H, and the latter is about 1.73 of the former. Double.

The operation using the hollow deposition substrate is performed for several days, and there is a danger that defective products will be generated during that operation.
With the other two hollow deposition substrates 5 and 5, a sound purified product can be obtained, so that a long operation is not wasted and the yield is improved.

FIG. 3 is a cross sectional view showing another arrangement of the coarse titanium and the hollow precipitation substrate in the reaction vessel.

Here, four hollow deposition substrates 5, 5,
5, 5 are symmetrically arranged around the center of the reaction vessel 1 at equal intervals. When four hollow deposition substrates 5, 5, 5, 5 are used, the total surface area is 4 × 2 × (V / 4πH)
^1/2 × π × H, which is about twice as large as when one deposition substrate is used.

FIGS. 4 and 5 are cross-sectional views showing another arrangement of the crude titanium and the hollow deposition substrate in the reaction vessel.

Here, a round bar having a circular cross section is used as the coarse titanium 7 '.

As shown in FIG. 4 or FIG. 5, when a rod is used as the coarse titanium 7 ', 7',..., The consumption between the coarse titanium 7 ', 7',. Despite the differences, the individual coarse titanium 7 'is consumed uniformly without any local depression. For this reason, change the installation position for each batch, such as changing the installation position for each batch, such as setting the low-consumption one to the high-consumption setting place and the high-consumption setting to the low-consumption setting place. It can be used. Therefore, the use efficiency of the coarse titanium 7 ', 7',.

When a plurality of hollow deposition substrates 5 are installed inside the reaction vessel 1, the variation in consumption depending on the installation position is greater than when one hollow deposition substrate 5 is used. The use of rod-shaped crude titanium 7 ', 7',... Which can be repeatedly used until the whole reaches the use limit is particularly effective.

Since the rod-shaped crude titanium 7 is a cast material,
The iodination reaction proceeds uniformly from the surface, and the reaction rate is stabilized.

In the purification reaction, titanium diiodide, which is a lower iodide, is thermally decomposed instead of directly pyrolyzing titanium tetraiodide. The temperature decreases and the likelihood of impurities being pyrolyzed together is small. It is of course possible to use a normal iodine method for directly pyrolyzing titanium tetraiodide.

[0037]

As described above, the method for purifying high-purity titanium according to the present invention is characterized in that in purifying high-purity titanium by the iodine method, a plurality of independent hollow deposition substrates are arranged in parallel in a reaction vessel. Since the surface area of the deposition substrate can be increased while securing an effective reaction space in the reaction vessel, the productivity can be further improved. In addition, even if a defective product occurs on a specific precipitation substrate during continuous operation, other deposition products can be adopted as a product, so that a decrease in yield due to occurrence of a defective product can be effectively suppressed. . Therefore, it is very effective in reducing the production cost of high-purity titanium.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic structure of a refining apparatus suitable for performing a method for purifying high-purity titanium of the present invention.

FIG. 2 is a cross-sectional view showing an arrangement of a crude titanium and a hollow precipitation substrate in a reaction vessel.

FIG. 3 is a cross-sectional view showing another arrangement of the coarse titanium and the hollow precipitation substrate in the reaction vessel.

FIG. 4 is a cross-sectional view showing an arrangement when a rod is used as coarse titanium.

FIG. 5 is a cross-sectional view showing another arrangement when a bar is used as coarse titanium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2 Heating furnace 3 Exhaust chamber 4 Lid 5 Hollow precipitation substrate 6 Heater 7, 7 'Crude titanium 8 Titanium tetraiodide supply device 9 Trap

Claims (2)

[Claims] 1. A method for purifying high-purity titanium in which crude titanium and a deposition substrate are disposed in a reaction vessel and high-purity titanium is deposited on the surface of the substrate by an iodine method. A method for purifying high-purity titanium, comprising arranging substrates in parallel. 2. The method for purifying high-purity titanium according to claim 1, wherein a plurality of hollow deposition substrates are arranged symmetrically with respect to the center of the reaction vessel.