WO2003040418A1

WO2003040418A1 - Method for producing titanium material of low oxygen content

Info

Publication number: WO2003040418A1
Application number: PCT/JP2002/001824
Authority: WO
Inventors: Hisayuki Wada
Original assignee: Sumitomo Titanium Corporation
Priority date: 2001-11-09
Filing date: 2002-02-27
Publication date: 2003-05-15
Also published as: JP3735060B2; JP2003147454A

Abstract

A method for producing a titanium material of a low oxygen content from a sponge titanium prepared by the kroll method, characterized in that a sponge titanium after separation under vacuum is cooled in a reaction vessel, a nitride film is then formed on the surface of the sponge titanium in the reaction vessel, and thereafter the sponge titanium is taken out of the reaction vessel and is cut or/and crushed. It is desirable that the formation of the nitride film is carried out through the introduction of a low oxygen content nitrogen gas having a ratio of partial pressure of nitrogen/partial pressure of oxygen of 20 or more to the reaction vessel, and that the nitrogen gas is introduced after the sponge titanium is so cooled as for the central portion thereof to have a temperature of 200˚C or lower. The method allows the production of a titanium material of a low oxygen content usable for a semiconductor target according to the Kroll method with a high production efficiency.

Description

Specification

Manufacturing method of low oxygen titanium material

The present invention relates to a method for producing low-oxygen titanium, and more particularly, to a method for producing a high-purity titanium material for forming a thin film useful as a material used when forming a wiring network on a surface of a semiconductor element. The present invention relates to a method for producing a titanium material having an oxygen concentration of 200 ppm or less and low oxygen, which is suitable as a material for an evening getter for sputtering manufactured from a high-purity titanium material for forming a thin film. Background art

Conventionally, high-purity refractory metal materials have been used as wiring materials for semiconductors. Specific examples of metal materials used as wiring materials include molybdenum, tungsten, niobium, titanium, and silicides thereof.Titanium has excellent specific strength, workability, and corrosion resistance. It is used.

At present, as a method of manufacturing titanium materials that are industrially employed, there is a method of producing titanium chloride by chlorinating titanium oxide and reducing it as an intermediate material to produce pure titanium metal. . Specifically, the Kroll method uses titanium tetrachloride (TiCI) as an intermediate material and uses magnesium (Mg) as a reducing agent, and the Hunter method uses sodium (Na) as a reducing agent. Comparing the production methods of these titanium materials, the chlorine method is considered to be an excellent production method from the viewpoint of productivity and energy saving.

FIG. 1 is a diagram illustrating a production process of titanium sponge obtained as a titanium material by the Kroll method along reduction, vacuum separation, and crushing. In the reduction step (①), TiCl ₄ is sprayed from nozzle 2 in reduction furnace 1 to react with molten Mg. At this time, if oxygen or the like is mixed in the reaction atmosphere in the reduction furnace 1, the sponge titanium is contaminated, so that the reaction is carried out in the sealed steel reaction vessel 3.

The Mg required for the reaction is charged into the reaction vessel 3, the inside of the vessel is replaced with an inert gas, and then heated to raise the temperature to melt the Mg. TiCL is supplied from the nozzle 2 into the reaction vessel 3 containing the molten Mg, and Ti and MgCl _{2 as a} by-product are generated. MgCl ₂ as a by-product is appropriately taken out of the reaction vessel 3, and finally sponge-like titanium containing unreacted Mg and residual MgCl ₂ is obtained in the reaction vessel 3.

In the vacuum separation step (②), the reaction vessel 3 is housed in a vacuum separation furnace 4, and the inside of the reaction vessel 3 is evacuated. Unreacted Mg and residual MgCl ₂ contained in the titanium sponge in 3 are evaporated. Evaporated unreacted Mg and residual MgCl ₂ are collected by a condenser 5 outside the vacuum separation furnace 4. The sponge titanium after vacuum separation is extruded from the reaction vessel 3 as a cylindrical mass.

In the crushing step (③), the extruded titanium sponge is cut by the cutting press 6 after its bottom, top and circumference have been removed. Then, it is crushed into fine grains (less than 1/2 inch) with a jaw crusher. The sponge titanium thus crushed to a predetermined particle size is mixed to further maintain the quality evenly, and then stored in a sealed drum filled with argon gas. After that, it is used as a raw material for dissolving titanium materials for semiconductors and wrought titanium materials.

On the other hand, with the recent increase in the density of LSI elements, titanium used for semiconductors is required to have high purity, and further reduction in the concentration of oxygen contained in the titanium is required. For example, in the titanium material used for the 64Mbit wiring material, which is the mainstream of DRAM, the oxygen concentration is 250p pm or less is required. Furthermore, in the case of titanium materials used for wiring materials with a high integration density of 128 Mbits or 256 Mbits, for which full-scale production has begun to be considered in recent years, the oxygen concentration contained is further reduced to 200 ppm or less. Has been required.

In response to such demands, various methods for producing low oxygen titanium materials have been proposed. For example, in Japanese Patent Application Laid-Open No. H10-259432, by specifying the humidity condition or temperature condition in the crushing step, the oxygen content has a high grade of 250 ppm or less and further 200 ppm or less, There has been proposed a method for producing a low-oxygen titanium material that can be applied to a kit. The method proposed here focuses on the fact that MgCl ₂ remaining in the sponge cake absorbs moisture in the atmosphere, thereby increasing the amount of oxygen contained in the sponge cake.

Specifically, when the humidity in the atmosphere during the cutting process of the sponge titanium, particularly the crushing process, is high, the oxygen content in the titanium sponge increases, and conversely, when the humidity in the atmosphere during the crushing process decreases, It says that oxygen contained in titanium sponge is suppressed. Thus, cutting the titanium sponge cakes made with Kroll process, when crushing the sorted sponge titanium, in an atmosphere of absolute humidity is "10g-H ₂ 0 / m ³ or less", more preferably ambient temperature The temperature is kept below 25 ° C.

However, if the method proposed in Japanese Patent Application Laid-Open No. Hei 10-259432 is to be implemented, a device for adjusting the atmospheric humidity and the atmospheric temperature in the crushing step is required, and the cost involved in the production of high-purity titanium is high. This will increase costs. In addition, oxygen contained in the sponge titanium removed from the reaction vessel due to moisture absorption can be suppressed, but titanium sponge is active against oxygen in the air atmosphere, so that it cannot react to an increase in oxygen concentration due to oxidation. It is not an effective means.

Also, in Japanese Patent Application Laid-Open No. 2000-309833, After cooling the sponge titanium until the temperature at the center part becomes substantially 100 ° C or less after vacuum separation, the center part of the sponge titanium is cut, and a low-oxygen high-purity titanium material having an oxygen content of 200 ppm or less. Is disclosed. In this method, when the surface of titanium sponge after vacuum separation is active, an oxide film is formed on the surface when exposed to the atmosphere, and the thickness of the oxide film depends on the temperature of the titanium sponge. The higher the value, the thicker the oxide film and the higher the oxygen concentration in titanium sponge.

However, the above method of defining the center temperature requires a relatively long cooling time in the reaction vessel after vacuum separation. Therefore, from the viewpoint of efficient production of low-oxygen copper material, there is room for improvement in shortening the cooling time. Disclosure of the invention

The present invention has been made to solve the problem of producing a low-oxygen titanium material, for example, titanium having an oxygen concentration of 200 ppm or less, and a nitride film is formed on the surface of the sponge titanium in a reaction vessel for cooling the sponge titanium. An object of the present invention is to provide a method for producing a low-oxygen titanium material suitable for producing an evening sputtering target by extracting sponge titanium after forming the titanium oxide.

The present inventor conducted various studies using the method disclosed in the aforementioned Japanese Patent Laid-Open Publication No. 2000-309833 to achieve the above object. When the titanium sponge is cooled down to substantially 100 ° C or less in the reaction vessel, a thin oxide film is formed on the surface of the titanium sponge taken out of the reaction vessel when cutting and collecting the central part. Will be formed. Then, if an oxide film is formed on the surface of the sampled titanium sponge, it becomes difficult to supply oxygen to the inside thereof, so that a subsequent increase in the oxygen content can be suppressed. Next, the cooling time in the reaction vessel was reduced, and the center temperature was about 150 ° C. When titanium is taken out, it reacts with oxygen in the atmosphere to form an oxide film on its surface. Due to the effect of the heat of reaction accompanying the formation of the oxide film, the surface temperature rises locally and oxidation proceeds further, and a relatively thick film is formed on the surface of titanium sponge. In addition, when cutting or crushing, a new cut surface or crushed surface appears with the processing, so the processing heat associated with the processing is combined with the reaction heat of the cut surface or the crushed surface, and the sponge titanium The formation of a film on the surface is promoted, and the oxygen content increases.

Even if the cooling time in the reaction vessel is shortened, nitrogen gas is introduced into the reaction vessel to form a nitride film on the sponge titanium surface in order to suppress the oxide film formed on the titanium sponge surface. Was taken out to the atmosphere. Since the bulk properties of titanium sponge are porous, nitrogen gas penetrates to the center of titanium sponge in the reaction vessel, so that the nitride film is formed almost entirely.

Even if the sponge titanium on which the nitride film is formed is exposed to the atmosphere, the formation of an oxide film by the subsequent oxidation reaction is significantly suppressed. For example, according to a study by the present inventor, the thickness of the oxide film on the surface of the bond is 100 to 150 A by the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-309833, whereas the nitride film is formed. The thickness of the oxide film on the surface of the sponge titanium remains below 100A.

Furthermore, when cutting or crushing, even if a new cut surface or crushed surface appears during processing and the temperature rises, the formation of an oxide film on the titanium sponge surface with a nitride film is suppressed. Will be.

The present invention has been completed based on the above findings, and has a gist of the following methods (1) and (2) for producing a low-oxygen titanium material.

(1) A method of producing a low-oxygen titanium material from titanium sponge obtained by the Kroll method, in which titanium sponge after vacuum separation is cooled in a reaction vessel. Then, after a nitride film is formed on the surface of the titanium sponge in the reaction vessel, the titanium sponge is taken out of the reaction vessel and cut or / and crushed.

(2) In the manufacturing method of the above (1), the formation of the nitride film is performed by introducing a low-oxygen-containing nitrogen gas having a ratio of nitrogen partial pressure / oxygen partial pressure of 20 or more into the reaction vessel. It is desirable to introduce nitrogen gas after the temperature of the center of the titanium sponge in the vessel has dropped below 200 ° C.

By employing the production methods (1) and (2), a titanium material having a low oxygen concentration of 200 ppm or less and a high purity can be produced. In the present invention, the high-purity titanium material is intended to have a content of Fe, Ni, Cr, A1, and Si as impurities of 10 ppm or less and a content of Na and K of 0.1 ppm or less as impurities. .

In the current manufacturing technology of the cup method, the mass of titanium sponge mass is 6 to 6 depending on the capacity of the reaction vessel used. According to the study of the present inventors, the manufacturing method of the present invention is not limited to 6 to! Oton weight titanium sponge, but other than that, for example, Ι Τοι! Applicable even for titanium sponge blocks of ~ 5 Ton. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating the steps of producing titanium sponge by the chlorine method in the order of reduction, vacuum separation, and crushing. BEST MODE FOR CARRYING OUT THE INVENTION

In the production method of the present invention, the titanium sponge after the vacuum separation is cooled in the reaction vessel, and then a nitride film is formed on the surface of the titanium sponge in the reaction vessel. It is characterized by: Hereinafter, nitrogen in the production of low oxygen titanium according to the present invention will be described. The formation conditions, cooling time, cutting, and crushing of the oxide film are explained. Usually, when cooling the sponge titanium to substantially 100 ° C. or less in the reaction vessel using the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-309833, the cooling time is 70 to 80 hours. Become. On the other hand, the cooling time according to the present invention may be 50 to 70 hours (see Examples described later), so that the cooling time can be significantly reduced.

The formation of the nitride film is performed by introducing nitrogen gas into the reaction vessel. The introduction timing may be any time just before taking out the sponge titanium from the reaction vessel. For example, the inside of the reaction vessel is evacuated and then filled with nitrogen gas 15 to 20 minutes before the completion of cooling, that is, 15 to 20 minutes before opening the lid of the reaction vessel. At this time, the argon gas in the container is exhausted by evacuation.This gas is injected from the start of cooling to increase the cooling rate of titanium sponge and to prevent air from leaking into the reaction container. Things.

Even if argon gas remains in the reaction vessel when nitrogen gas is introduced, if nitrogen in the reaction vessel is at least 10% by mass (mass%), formation of a nitride film using nitrogen gas can be performed properly. Will be

As the nitrogen gas used for forming the nitrided layer in the present invention, it is desirable to use a low oxygen-containing nitrogen gas having a ratio of nitrogen partial pressure / oxygen partial pressure of 20 or more. This is because even when the oxygen gas is contained in the nitrogen gas, by controlling the oxygen at a low partial pressure, that is, at a low concentration, the formation of the nitride film has priority over the formation of the oxide film. is there.

Therefore, when using a nitrogen gas having a nitrogen partial pressure / oxygen partial pressure ratio of less than 20, the oxide film is mainly formed, and the originally necessary nitrogen film may not be formed sufficiently. On the other hand, since the nitriding gas used may be pure nitrogen gas, the upper limit of the ratio of nitrogen partial pressure / oxygen partial pressure does not need to be particularly defined. In the present invention, it is desirable that the low oxygen-containing nitrogen gas be introduced after the temperature of the central part of the titanium sponge cooled in the reaction vessel becomes 200 ° C. or less. More preferably, it should be introduced after the temperature at the center has dropped below 150 ° C. When nitrogen gas is introduced at a temperature of 200 ° C or more at the center, the thickness of the formed nitride film increases rapidly, and the concentration of nitrogen contained increases, affecting high-purity titanium. Is concerned.

Usually, the temperature control in the central part is controlled by the cooling time after the end of vacuum separation. For this reason, the sponge titanium that has completed the reaction is cooled, drilled from above to insert a thermocouple in the center, and then heated to a temperature at which vacuum separation is performed. After performing vacuum separation, it is cooled, and the relationship between the time from the start of cooling and the temperature at the center is measured. The cooling time after vacuum separation is controlled based on the measurement results.

Further, in the production method of the present invention, it is desirable that after taking out from the reaction vessel, the sponge titanium is cut, and a cut mass whose measured oxygen concentration satisfies a required concentration is selected and cut and crushed. This is to strictly control the concentration and quality of the titanium produced.

At present, the content of impurities required for high-purity titanium materials in the sputtering target is less than 30 ppm for nitrogen concentration and less than 250 ppm for oxygen concentration. Recently, the required nitrogen concentration is not a problem, but the oxygen concentration is shifting to severe conditions, and the oxygen concentration is affecting the yield of high-purity titanium materials. Therefore, the reference oxygen concentration here is 180 ppm.

In actual operation, not all the cut pieces of titanium sponge are measured, but the cut pieces at the center except for the peripheral part. For example, as the central part, a part with a thickness of 15% or more of the lump height from the bottom of the titanium sponge mass and a part with a thickness of 5% or more of the lump height from the top are cut and removed, and the cylindrical lump is removed. This corresponds to the part where the circumferential part with a thickness of 10% or more of the lump diameter is cut off from the circumferential part of.

The method of the present invention relates to a method for producing a low oxygen titanium material, comprising the steps of: Even when a thin nitride film is formed on the surface of dititanium and then exposed to the atmosphere, the formation of an oxide film can be suppressed. As a result, new equipment and equipment are not particularly required, and oxygen reduction can be achieved. Therefore, the method of the present invention is an effective production method. In addition, this method is not only effective for high-purity titanium material, but also applicable to wrought material, powder production, and titanium production for precision fabrication.

(Example)

The effects of the manufacturing method of the present invention will be described in detail based on specific examples. Cylindrical sponge titanium with a weight of about 6 T after vacuum separation was produced by the Kroll method.

In the invention example, the cooling time after the completion of the vacuum separation was controlled at 50 to 76 hours, and the inside of the reaction vessel was substantially evacuated for 10 minutes from 15 minutes to 5 minutes before opening the reaction vessel. Then, from 5 minutes before opening the reaction vessel to 5 minutes before the opening, nitrogen gas with a nitrogen partial pressure / oxygen partial pressure ratio of 100 or more was introduced from the vessel lid, and the lid was opened to open the inside of the reaction vessel. The sponge titanium mass was taken out into the atmosphere. The removed sponge titanium was sized by cutting and crushing to a particle size of 10 to 30 mm, mixed uniformly, and then the oxygen concentration and nitrogen concentration at the center of the mass were measured.

In the comparative example, the sponge titanium removed from the reaction vessel was cut and crushed to a particle size of 10 to 30 mm without introducing nitrogen gas, with the cooling time after completion of vacuum separation being 50 to 76 hours. After mixing uniformly, the oxygen concentration and the nitrogen concentration at the center of the mass were measured.

As is evident from the results in Table 1 on the next page, Invention Example 1 significantly reduced the cooling time, but the result is that the oxygen concentration satisfies 200 ppffl or less. Thus, low oxygen titanium which can be used as a material was obtained. On the other hand, in Inventive Example 3, if the same cooling time as that of the related art is ensured, it becomes possible to produce a low-oxygen titanium material that could not be obtained conventionally. table 1

Industrial applicability

According to the method for producing a low-oxygen titanium material of the present invention, a nitrogen gas is introduced into a reaction vessel of the crawl method, and a nitride film is formed up to the central portion of the cylindrical titanium sponge. A low-oxygen titanium material having an oxygen concentration of 200 ppm or less, which is suitable for producing one get, can be produced. Moreover, the cooling time can be greatly reduced, the production efficiency is excellent, and it can be widely used as an industrial method for producing low oxygen titanium materials.

Claims

The scope of the claims

1. A method for producing a low-oxygen titanium material from titanium sponge obtained by the Kroll method, in which the sponge titanium after vacuum separation is cooled in a reaction vessel, and then a nitride film is formed on the surface of the titanium sponge in the reaction vessel. 5) A method for producing a low-oxygen titanium material in which titanium sponge is taken out of a reaction vessel and cut or / and crushed.

2. The method for producing a low oxygen titanium material according to claim 1, wherein the formation of the nitride film is performed by introducing a low oxygen-containing nitrogen gas having a nitrogen partial pressure / oxygen partial pressure ratio of 20 or more into the reaction vessel.

L03. The method for producing a low-oxygen titanium material according to claim 1 or 2, wherein the low-oxygen-containing nitrogen gas is introduced after the temperature of the center of the sponge titanium has become 200 ° C or lower in the reaction vessel.

4. The method for producing a low oxygen titanium material according to claim 1, wherein the produced titanium material has an oxygen concentration of 200 ppm or less.

L55. The method for producing a low oxygen titanium material according to any one of claims 1 to 4, wherein the produced titanium material has a nitrogen concentration of 30 ppm or less.