JP3129709B2 - Method for producing low oxygen high purity titanium material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity titanium material for a target used for forming a wiring material for a semiconductor. More specifically, the present invention relates to a method for producing a sputtering target. The present invention relates to a method for producing a low-oxygen and high-purity titanium material.

[0002]

2. Description of the Related Art Conventionally, high-purity high-melting point metal materials have been used as wiring materials for semiconductors. Specific examples of the metal material used as the wiring material include molybdenum, tungsten, niobium, titanium and their silicides. Among them, titanium is widely used because of its excellent specific strength, workability and corrosion resistance. I have.
With the recent increase in the density of LSI devices, titanium used for wiring materials for semiconductors is required to have high purity, and further reduction in the concentration of contained oxygen is required.

For example, with respect to the oxygen content, a high-purity titanium material used for a 64-Mbit wiring material, which is a mainstream of DRAM, requires an oxygen concentration of 250 ppm or less. Furthermore, in the case of high-purity 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 studied in recent years, the oxygen concentration contained is further reduced to 200 ppm or less. It is desirable to be.

In response to such a demand, Japanese Patent Publication No. 4-75
No. 301 discloses that the oxygen content is reduced to 250 ppm or less, the iron (Fe), nickel (Ni), and chromium (Cr) content is 10 ppm or less, and the sodium (Na) and potassium (K) content is reduced. A high purity titanium material for a thin film forming target having a content of 0.1 ppm or less is disclosed, and as a method for producing the same, a method of electron beam melting a crude titanium material obtained by a molten salt electrolysis method in a high vacuum has been proposed. The titanium material manufactured in this way is used not only for thin film forming targets, but also for LSIs, VLSIs,
Even when viewed as a thin film material such as ULSI, the content of impurity elements to be avoided is extremely small.

Certainly, in the combination of the molten salt electrolysis method and the electron beam melting method, the acicular titanium obtained by the molten salt electrolysis method is melted in a high vacuum using an electron beam.
Alkali metals such as Na and K, which are often contained in the acicular titanium, can be efficiently evaporated, and a high purification effect can be obtained. Further, since the electron beam melting method is performed under a vacuum condition of 10 ^-5 torr, almost no increase in the oxygen concentration in the smelted titanium material is recognized.

[0006] Incidentally, in addition to the above-mentioned molten salt electrolysis, titanium tetrachloride (TiCl ₄ ) as an intermediate raw material is currently used industrially as a method for producing a titanium material for spreading. Is reduced to pure titanium metal,
It is roughly divided into two manufacturing methods. That is, Kroll, which is thermally reduced using magnesium (Mg) as a reducing agent
Hunte using sodium (Na) as a reducing agent
r) method.

[0007] Comparing the production methods of these wrought titanium materials, the crawl method is the most excellent from the viewpoint of productivity and energy saving, whereas the molten salt electrolysis method is inferior. Furthermore, in the method of manufacturing a high-purity titanium material for a target disclosed in the above-mentioned Japanese Patent Publication No. 4-75301, in addition to the above-mentioned problems of the molten salt electrolysis method, there is a problem that an expensive apparatus cost of the electron beam melting method is required. It is. For this reason,
Various attempts have been made to improve the conventional crawl method and produce high-purity titanium for a target.

FIG. 1 is a view for explaining the steps of producing the sponge titanium for spreading by the Kroll method in the order of reduction, vacuum separation and crushing. First, in the reduction step (), TiCl ₄ is sprayed from the nozzle 2 in the 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 titanium sponge will be contaminated.
The reaction is performed in a closed steel reaction vessel 3.

[0009] Mg required for the reaction is charged into the reaction vessel 3,
After replacing the inside of the container with an inert argon gas, the temperature is increased by heating to melt Mg. TiCl ₄ is supplied from a nozzle 2 into a reaction vessel 3 containing molten Mg, and Ti and by-product MgC
l ₂ is generated. MgCl ₂ as a by-product is added to the reaction vessel 3
And finally unreacted Mg and residual Mg
Sponge-like or needle-like titanium containing Cl ₂ is used as the reaction vessel 3
Obtained within.

In the vacuum separation step (1), the reaction vessel 3 is housed in a vacuum separation furnace 4, and the inside of the reaction vessel 3 is evacuated, and the inside of the reaction vessel 3 is further heated from outside. Unreacted Mg and residual MgCl ₂ contained in the titanium sponge in the reaction vessel 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 (), the extruded lump of titanium sponge is cut by the cutting press 6 after its bottom, top and circumference are removed. Then, it is crushed into fine grains (less than 1/2 inch) with a jaw crusher. Sponge titanium crushed to a predetermined particle size in this way,
After mixing to maintain the quality even, the mixture is stored in a sealed drum filled with argon gas. However, in the production of high-purity titanium materials for targets,
In order to avoid contamination of the oxygen component and the metal component, fine particles are not crushed or mixed.

Japanese Patent Application Laid-Open No. 7-258765 discloses production of a high-purity titanium material for a target by the Kroll method.
A method for producing a high-purity titanium material by selecting a central portion of a cylindrical titanium sponge produced using a reaction vessel, cutting the central portion into 10 to 300 mm, and dissolving the obtained sponge titanium as a consumable electrode. Is disclosed.

[0013] In other words, in the cylindrical titanium sponge produced by the Kroll method, the distribution of impurities present in the mass is not uniform. For example, oxygen (O ₂ )
Is caused by the titanium sponge mass extruded from the reaction vessel coming into contact with O ₂ in the air atmosphere and being contaminated from the outer surface of the mass. Therefore, it is stated that the concentration of oxygen contained can be reduced by limiting the sponge titanium to be collected to the center of the cylindrical mass. For this reason, the manufacturing method proposed in Japanese Patent Application Laid-Open No. 7-258765 has achieved a certain result since high-purity titanium can be manufactured at relatively low cost.

In Japanese Patent Application Laid-Open No. 10-259432, the humidity condition or the temperature condition in the crushing step is specified, so that the oxygen content has a high quality of 250 ppm or less and can be applied to a sputtering target. A method for producing a low oxygen titanium material has been proposed. Here, in the proposed method, MgCl ₂ remaining in the sponge cake by absorbing moisture in the atmosphere, attention is paid to the amount of oxygen contained in the sponge cake increases.

Specifically, a step of cutting titanium sponge;
Particularly when the humidity in the atmosphere in the crushing step is high, the oxygen content in the titanium sponge increases, and conversely, when the humidity in the atmosphere in the crushing step decreases, the oxygen contained in the titanium sponge is suppressed. And For this reason, when cutting the sponge titanium cake manufactured by the Kroll method and crushing the sorted sponge titanium cake, the absolute humidity is `` 10 g-H ₂ O / m ³ or less '' in an atmosphere, more preferably the ambient temperature is 25. ° C
It keeps it below.

If the method proposed in Japanese Patent Application Laid-Open No. H10-259432 is to be carried out, it is difficult to obtain the atmospheric humidity,
In addition, a device for adjusting the ambient temperature is required,
The installation cost and the operation cost of the apparatus increase the production cost of high-purity titanium. Further, the atmosphere adjustment in the crushing step, which is a subsequent step, is insufficient for reducing the oxygen content. In other words, in order to suppress the oxygen contained in the sponge titanium, the sponge cake remains in the sponge cake.
MgC1 ₂ hygroscopic rather than a major problem, active state with respect to oxygen in the ambient atmosphere, i.e., upon cleavage of titanium sponge taken from the reaction vessel, must take measures.

[0017]

DISCLOSURE OF THE INVENTION The present invention is intended to produce low-oxygen high-purity titanium having an oxygen concentration of 200 ppm or less by the Kroll method, An object of the present invention is to provide a method for producing low-oxygen and high-purity titanium suitable for producing a sputtering target by controlling the temperature of a central portion of a cylindrical titanium sponge.

[0018]

Means for Solving the Problems The present inventors have conducted various studies using the method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-258765 in order to achieve the above object. Usually, after the reduction reaction, the sponge titanium that has been subjected to the vacuum separation is cooled to a surface temperature of 100 ° C. or lower, and then taken out of the reaction vessel using an extruder or the like. Here, the reason why the standard for taking out from the reaction vessel is “100 ° C. or less in surface temperature” is a result in consideration of the workability of the extruder, the workability of the subsequent cutting press, and the characteristics of sponge titanium described later.

Conventionally, in order to obtain low oxygen sponge titanium, sponge titanium taken out of the reaction vessel is
In order to shorten the exposure time to the atmosphere, the central part is cut as soon as possible, and the cut part is adjusted to 10 to 300 mm in the crushing step as it is, or if necessary, to obtain a high-purity center. Collected as part. The collected titanium sponge is stored in a sealed drum filled with argon gas.

Since the surface of the sponge titanium after the vacuum separation is active, it is easily oxidized from the outside, and when exposed to the atmosphere, an oxide film is formed on the surface. The thickness of the oxide film formed at this time depends on the temperature of the titanium sponge, and the higher the temperature, the thicker the oxide film, and accordingly, the concentration of oxygen contained in the titanium sponge also increases. Since the oxide film is dense and strong, once the oxide film is formed on the surface, oxygen is no longer supplied to the inside of the titanium sponge, and the increase in the oxygen content is hardly recognized.

In order to form an appropriate oxide film thickness, it is a standard to set the surface temperature to 100 ° C. or less. But,
Since the thermal conductivity of titanium sponge is extremely low,
Even if the surface temperature is 100 ° C., the temperature exceeds 100 ° C. in the central part where high-purity titanium is collected. Furthermore, when cutting with a cutting press, it must be noted that the temperature rises with the cutting process. According to the study results of the inventors, it depends on the speed of the cutting process, but 20 ° C.
A temperature rise of about 40 ° C. is observed, and when the surface temperature exceeds 100 ° C., a thick oxide film is formed.

In consideration of the above-mentioned characteristics of titanium sponge, the temperature of the central part of titanium sponge in the reaction vessel is 10
0 ℃ or less, that is, even if the temperature rise is observed with the processing of the cutting press, so as to take out after cooling down to substantially 100 ℃ or less, then by immediately collecting the central part, low It has been found that high-purity titanium suitable for manufacturing a sputtering target can be manufactured with oxygen. The present invention has been completed based on such knowledge, and has a gist of the following (1), (2) and (3) methods for producing a low-oxygen and high-purity titanium material. The following theory
Low oxygen means that the oxygen concentration is 200 ppm or less.
High purity means that Fe, Ni, Cr, Al, Si
The content is 10 ppm or less, and the content of Na and K is 0.1 ppm or less.
Intended to be.

(1) A method for producing a high-purity titanium material by collecting a central portion of titanium sponge produced by the Kroll method, wherein the temperature of the central portion of the titanium sponge is
After There was cooled to 100 ° C. or less, a method for producing a low-oxygen high-purity titanium material, characterized in that cutting the center portion of titanium sponge. However, the sponge in the present invention
The central portion of the dititanium conforms to the rules described later.

(2) A method of producing a high-purity titanium material by collecting a central portion of titanium sponge produced by the Kroll method, wherein the temperature of the central portion of the titanium sponge is cooled to 60 ° C. or less. after a method for producing a low-oxygen high-purity titanium material, characterized in that cutting the center portion of titanium sponge.

(3) A method for producing a high-purity titanium material by sampling a central portion of titanium sponge similarly to the above (1) and (2), wherein the temperature of the central portion of titanium sponge in a reaction vessel is There 100 ° C. or less, or 60 ° C. after cooling down below a predetermined temperature, a method for producing a low-oxygen high-purity titanium material, characterized in that cutting the center portion of titanium sponge removed from the reaction vessel.

In the method for producing a low-oxygen and high-purity titanium material according to the above (1), (2) and (3), the inside of the reaction vessel is made of low-carbon steel in order to prevent mixing of metallic impurities such as Ni and Cr. It is desirable that the outside is made of clad steel as stainless steel.

In the present invention, the central part of the titanium sponge is defined as a part having a thickness of 25% or more of the lump height from the bottom of the titanium sponge lump taken out of the reaction vessel after vacuum separation and a lump having a thickness from the top. Cut and remove 10% or more of the height, and cut and remove from the circumference of the cylindrical mass a circumference of 18% or more of the mass diameter, and remove 30% of the weight of the titanium sponge mass.
%. The central portion, as the distribution of impurities sponge titanium, other O _2, N
This is obtained as a result of a detailed study of the uneven distribution of i, Cr, Fe and the like.

In the current production technology of the crawl method,
The weight of the titanium sponge mass is often 6 to 10 tons depending on the capacity of the reaction vessel used. According to the study of the present inventors, the definition of the central portion is not limited to the titanium sponge mass of 6 to 10 ton weight,
For example, sponge titanium lump of 1Ton-5Ton,
It has been confirmed that the center part specified above can be applied.

In the method (1) for producing a low-oxygen high-purity titanium material, the temperature of the central portion is specified to be 100 ° C. or less even when the thermal conductivity of titanium sponge is taken into consideration, or Even if the temperature rises with the processing of the cutting press, the temperature at the center of the titanium sponge is 100%.
It means that the temperature is below ℃.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the cutting of the central part of the sponge titanium taken out of the reaction vessel is performed regardless of whether the sponge titanium is cooled in the reaction vessel or the sponge titanium is taken out of the reaction vessel and cooled. At the time of sampling, the temperature of the corresponding central portion is controlled to be low, so that a thin oxide film is formed on the surface thereof. When an oxide film is formed on the surface of the sampled titanium sponge, it becomes difficult to supply oxygen to the inside of the titanium oxide sponge, so that the subsequent increase in the oxygen content can be suppressed.

The specific temperature of the central part is 100 ° C.
It is to be cooled to below or to 60 ° C or below. Usually, the temperature control of the central portion is controlled by the cooling time after the completion of the vacuum separation. Therefore, the sponge titanium which 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. Then, cooling is performed after vacuum separation, and the relationship between the time from the start of cooling and the temperature of the central portion is measured. Based on this measurement result,
The cooling time after vacuum separation is controlled.

Further, in the present invention, in order to further reduce the concentration of impurities, the reaction vessel used in the reduction step and the vacuum separation step is made of clad steel having carbon steel on the inside and stainless steel on the outside. desirable. Since the inner carbon steel is used to avoid the elution of Ni, Cr, etc. into the molten Mg, rolled steel for general structures (SS330 to SS540) specified in JIS, carbon steel for boilers and pressure vessels (SB
410 to SB480) and steel plates for pressure vessels (SPV315 to SPV49)
0) etc. may be adopted. On the other hand, the outer stainless steel is preferably austenitic from the viewpoint of ensuring high-temperature strength, and is a stainless steel sheet SUS304, SUS3
04L, SUS310, SUS316, SUS316L and SUS321 are used.

If possible, the sizing of the center of the titanium sponge can be performed only by cutting with a cutting press, and the grain refinement by a jaw crusher can be omitted. The target particle size is 10 to 300 mm, more preferably 2 to 300 mm.
00 to 300 mm. When such a particle size cannot be ensured only by the cutting press, the particle size may be reduced by using a jaw crusher. By omitting the step of grain refinement as much as possible, it is possible to reduce the specific surface area of the central portion of the titanium sponge and prevent oxygen contamination from the air atmosphere.

[0034]

EXAMPLES The effects of the manufacturing method of the present invention will be described in detail based on specific examples. Cylindrical sponge titanium lump (dimensions: height H20) manufactured by a crawl method using a clad steel reaction vessel (outside: SUS304L stainless steel / inside: SS400 carbon steel) and having a weight of about 6 T after vacuum separation
00 mm x diameter D1500 mm). The cooling time after the completion of the vacuum separation was controlled, and when the central part of the titanium sponge mass reached a predetermined temperature, the central part was taken out of the reaction vessel and immediately cut and collected.

At the time of collecting the center, a portion having a thickness of 550 mm (28% of the height of the lump) from the bottom of the titanium sponge mass and a portion of a thickness of 250 mm (13% of the height of the lump) from the top are cut and removed. Then, 350mm (23% of the diameter of the lump) is cut off from the circumference of the cylindrical lump, and the center part (height: 1200mm x diameter: 800mm x weight: 1,200mm) corresponding to 20% of the lump weight (Equivalent to Kg) was taken out, cut by a cutting press to a particle size of 10 to 300 mm, and sized.

In the embodiment, the temperature of the central portion of the sponge titanium at the start of cutting is changed in the range of 40 ° C. (room temperature) to 200 ° C. by estimating the relationship between the cooling time and the temperature of the central portion from the measured data. Was. After sampling the central part, 800-2000K
g was sampled and the oxygen content was measured. The results are shown in Table 1. In addition, as other impurities, Fe, Ni, Cr, Al,
It has been confirmed that the content of Si is 10 ppm or less and the content of Na and K is 0.1 ppm or less.

[0037]

[Table 1]

As is clear from the results in Table 1, in the invention examples (Nos. A to C), the temperature at the center of the titanium sponge was 100 ° C. or less when the sponge was taken out of the reaction vessel.
The concentration of oxygen contained in each case was 200 ppm or less. In Comparative Example No. D, the temperature at the center was controlled at 100 ° C., but there was a rise in temperature along with the cutting, which substantially exceeded 100 ° C.
The oxygen concentration increased to 207 ppm.

[0039]

According to the method for producing a low-oxygen high-purity titanium material of the present invention, by controlling the temperature of the central portion of the cylindrical titanium sponge at the stage of taking it out of the reaction vessel, it is suitable for producing a sputtering target. In addition, low-oxygen high-purity titanium having an oxygen concentration of 200 ppm or less can be produced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a production process of titanium sponge by the Kroll method in the order of reduction, vacuum separation, and crushing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reduction furnace, 2 ... Nozzle, 3 ... Reaction vessel 4 ... Vacuum separation furnace, 5 ... Condenser 6 ... Cutting press

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-25527 (JP, A) JP-A-9-104931 (JP, A) JP-A-10-259432 (JP, A) JP-A-7-107 258765 (JP, A) JP-A-9-287035 (JP, A) JP-A-9-272928 (JP, A) JP-A-7-41881 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 34/12 103

Claims (5)

(57) [Claims] (1) cutting and removing a portion having a thickness of 25% or more from the bottom and a portion having a thickness of 10% or more from the top from the bottom of titanium sponge produced by the Kroll method, and Producing high-purity titanium material by cutting and removing from the circumference of the cylindrical lump the circumference part with a thickness of 18% or more of the lump diameter and collecting the central part corresponding to less than 30% of the weight of the titanium sponge lump The temperature of the central portion of the titanium sponge is
After cooled to 100 ° C. or less, the oxygen concentration is 200ppm or less, characterized in that cutting the central portion of the titanium sponge
Below, Fe, Ni, Cr, Al and Si are reduced to 10 ppm or less and Na and
Of high purity titanium material containing 0.1ppm or less of K and K
Law . 2. The sponge titanium produced by the Kroll method is cut and removed from a bottom portion having a thickness of 25% or more of the lump height and a top portion having a thickness of 10% or more of the lump height from the top, and Producing high-purity titanium material by cutting and removing from the circumference of the cylindrical lump the circumference part with a thickness of 18% or more of the lump diameter and collecting the central part corresponding to less than 30% of the weight of the titanium sponge lump The temperature of the central portion of the titanium sponge is
After cooling down to 60 ° C or less, cut the central part of titanium sponge.The oxygen concentration is 200ppm or less.
Fe, Ni, Cr, Al and Si by 10 ppm or less and Na and
Of high purity titanium material containing 0.1 ppm or less of K and K. 3. The method according to claim 1, wherein after cooling the temperature of the central part of the titanium sponge in the reaction vessel to 100 ° C. or lower, the titanium sponge is taken out of the reaction vessel and the central part of the titanium sponge is cut. The method for producing a high- purity titanium material according to claim 2. 4. The method according to claim 1, wherein after cooling the temperature of the central part of the titanium sponge in the reaction vessel to 60 ° C. or less, the titanium sponge is taken out of the reaction vessel and cut at the central part. The method for producing a high- purity titanium material according to claim 2. 5. The method according to claim 1, wherein the reaction vessel is made of clad steel.
Production method of high purity titanium material.