WO2003066914A1

WO2003066914A1 - High-purity spongy titanium material and its production method

Info

Publication number: WO2003066914A1
Application number: PCT/JP2002/001118
Authority: WO
Inventors: Hisayuki Wada
Original assignee: Sumitomo Titanium Corporation
Priority date: 2000-08-07
Filing date: 2002-02-08
Publication date: 2003-08-14
Also published as: AU2002232157A1; EA006077B1; CN100487144C; JP2002053922A; JP3756047B2; EA200401055A1; CN1633511A

Abstract

A high-purity spongy titanium material containing less amounts of oxygen and metal elements is economically produced. The vacuum separation time t in a vacuum separation step is t = tO + 15 to + 35 hour where tO is the time from the start of the vacuum separation till the time when the temperature of the central part of the material in a reaction vessel reaches to a stable temperature. At and near the central part of the material where the amounts of metal elements are a little, the specific area measured by the BET method is below 0.05 m2/g. The amount of oxygen after cutting and crushing is suppressed to a low level even if the cutting and crushing are carried out in the atmosphere.

Description

Description High purity titanium sponge material and method for producing the same

TECHNICAL FIELD The present invention relates to a high-purity sponge titanium material suitable for a material for an evening gate material for sputtering and a method for producing the same. Background art

As an industrial production method of titanium metal, a method of cutting and crushing a sponge titanium material produced by the Kroll method, hardening it into a briguet, and dissolving and producing the same is often used. The Kroll method consists of a reduction step in which molten Mg reacts with titanium tetrachloride in a reaction vessel, and after reduction, heats the reaction vessel in a vacuum state to heat unreacted Mg contained in the material in the vessel. And a vacuum separation step of evaporating and removing residual by-products.

On the other hand, a new use of titanium metal is as a wiring material in semiconductor devices such as LSI. This wiring is formed by performing sputtering using high-purity metallic titanium as a target material. It is required that the sputter material for sputtering has a small amount of impurities. The sponge titanium material, which is a material of the sputter material, has an oxygen content of 20 ppm or less, Fe, Ni, Cr, and A. The content of each metal element of 1 and Si is required to be 10 ppm or less.

However, since the crawl method is a method that prioritizes productivity, it is not easy to secure an impurity level required for an evening gate material for sputtering. Therefore, the following method has been proposed. One is the top and bottom of the titanium sponge material obtained in the reaction vessel after vacuum separation. Centering method to commercialize the part near the center excluding the outer part and outer periphery

Another method is a low-moisture crushing method in which a sponge titanium material taken out of the reaction vessel is cut and crushed in a low-humidity atmosphere (Japanese Patent No. 2863469). No. 2,179,900).

However, the former method of centering can secure the level required for the evening getter material for sputtering for each of the metal elements Fe, Ni, Cr, A1, and Si. However, it is difficult to maintain the level of oxygen. On the other hand, in the latter method of low-moisture crushing, as for oxygen, a force capable of securing a level required for a target material for sputtering ^ Fe, Ni, Cr, A1, and Si. It is difficult to secure the level of each metal element.

Therefore, in order to secure the levels required for the evening getter material for sputtering, both the Fe, Ni, Cr, A1, and Si metal elements, and oxygen, the former should be selected as the center. It is necessary to combine this method with the latter method of low-moisture crushing. However, as a practical matter, the former method of centering is easy to implement, while the latter method of low-moisture crushing has a stable oxygen level actually required for the target material for sputtering. In order to secure such a space, a very large isolated work space with a low humidity inside is required, and the construction and maintenance of the atmosphere require a great deal of expense. I can not say.

An object of the present invention is to provide a high-purity titanium sponge material which is low in both the amount of oxygen and the amount of a metal element and which is excellent in economical efficiency, and a method for producing the same. Disclosure of the invention

In order to achieve the above object, the present inventors have produced by the chlorine method. We focused on the relationship between the sampling position of the sponge titanium material and the oxygen content. FIG. 1 is a longitudinal sectional view of a titanium sponge material in a reaction vessel in a vacuum separation step. The reaction vessel 20 is housed in a heating furnace 30. Since the titanium sponge material 10 in the reaction vessel 20 causes precipitation of titanium on the rostrol 21 in the reaction vessel 20 and on the inner surface of the side wall of the reaction vessel 20 in the previous reduction step, the middle part is narrowed. Shape.

In the sponge titanium material 10 after the vacuum separation step, the content of each of the metal elements Fe, Ni, Cr, A1, and Si decreases as the distance from the upper surface, the lower surface, and the outer peripheral surface increases. This is because the content of each metal element is mainly due to contamination from the reaction vessel 20. For this reason, by removing the upper, lower, and outer peripheral portions of the sponge titanium material 10 and collecting the remaining portion 11 near the center, the level of the metal element required for the evening getter material for sputtering can be reduced. Can be relatively easily secured.

However, the oxygen content, particularly the oxygen content after cutting and crushing, surprisingly decreases in the surface layer of the sponge titanium material 10. For example, when examining the oxygen content distribution after cutting and crushing at the center of the sponge titanium material 10 from the uppermost part A to the 1Z2 part C, the oxygen amount increases closer to 1/2 part C. . For example, when the oxygen content of the titanium particles obtained from the uppermost part A is 250 ppm, 1/4 part B is about 300 ppm, that is, 1/2 part. Then it becomes about 3501 m. Due to this tendency, even if the portion 11 near the center of the titanium sponge material 10 is sampled, it becomes difficult to secure the level of oxygen required for the sputtering target material after cutting and crushing.

The present inventors have investigated the cause of the decrease in the amount of oxygen in the surface layer of the titanium sponge material 10 from both the physical properties and the production method. As a result, the following facts became clear.

Figure 2 shows the temperature change of the titanium sponge material in the vacuum separation process. The upper part A, 1Z4 part B and 1Z2 part C are shown. The temperature in either part tends to drop temporarily after the start of vacuum separation, then rises and reaches a stable temperature close to the furnace temperature. This is because the residual Mg starts to evaporate together with the vacuum separation, and the temperature temporarily decreases due to the heat of vaporization.However, the temperature starts to increase as the residual Mg decreases, and the furnace temperature increases when the evaporation is completed. Due to temperature stabilization at a level close to

This tendency is common in the top section A, 1/4 section B, and 1/2 section C, but the lowest temperature is lower in the order of the top section A, 1/4 section B, 1Z2 section C, and vacuum separation starts. The time from when the temperature starts to rise and when the temperature reaches the stable temperature increases in the order of top A, 1/4 B, and 1/2 C. This is because the portion nearer to the center of the titanium sponge material is more difficult for residual Mg to escape, and the central portion where the residual Mg is most difficult to escape, that is, 1/2 part of the residual Mg is removed, and the temperature Tc The point at which the temperature reaches the stable temperature T 0 is the end of the vacuum separation. The reason that the stable temperature is lower in the order of the uppermost part A, the 1Z4 part B, and the 1/2 part C is due to the remarkable heat radiation toward the opening (upper side) of the reaction vessel.

As a result of performing vacuum separation in such a process, the surface portion far from the center of the titanium sponge material is continuously heated for a long time even after the evaporation of Mg is completed, and becomes a so-called dry-fired state. The present inventor believes that the heating time after the evaporation of the Mg is related to the oxygen amount after the cutting and crushing, and conducted various investigations. As a result, the farther from the center of the titanium sponge material, the more the empty firing state The sintering proceeds during the heating of the steel to reduce the specific surface area, and the smaller the specific surface area, the more the increase in the amount of oxygen due to oxidation in the cutting and crushing process is suppressed. As a result, 1/2 part C, 1Z4 If the amount of oxygen after cutting and crushing decreases in the order of part B and top A, 1Z 2 If heating is continued even after evaporation of Mg in part C, sintering of this part proceeds and The surface area becomes smaller It was found that hypoxia was realized.

The present invention has been completed based on this finding, and the high-purity titanium sponge material is a titanium sponge material produced by the chlorine method, and has a specific surface area of 0.05 m measured by the BET method. ² Zg or less, and the content of each metal element of Fe, Ni, Cr, A1, and Si is 10 ppm or less.

By limiting the specific surface area to 0.05 m ² / g or less according to the 8-patch method, even when cutting and crushing in a normal air atmosphere, the oxygen content of titanium particles is 300 ppm or less. Is suppressed. It is preferably at most 0.04 m ² Zg, more preferably at most 0.03 m ² / g, whereby the oxygen content is further reduced. The preferred oxygen content after cutting and crushing is 200 ppm or less, more preferably 100 ppm or less. The lower limit of the specific surface area, but the lower, the better in terms of oxygen content reduced, since it is difficult to cut fracture and too small specific surface area, 0. 01 m ² Zg more preferably

The content of each of the metal elements Fe, Ni, Cr, A1, and Si is limited to 10 ppm or less in order to eliminate the upper, lower, and outer peripheral portions of the titanium sponge material. These surface layers, for example, the uppermost portion A shown in Fig. 1, have been heated in the dry state, and the specific surface area by the BET method has been reduced. However, in this part, the content of each metal element exceeds 1 O ppm. A particularly preferred content of each metal element is 7 ppm or less.

In addition, the method for producing a high-purity titanium sponge material of the present invention is characterized in that, when producing a titanium sponge material by the Kroll method, the vacuum separation time t in the vacuum separation step is set at the center of the material in the reaction vessel from the start of the vacuum separation. The time until the temperature Tc reaches the stable temperature To near the furnace temperature is defined as t0, and t = to + (15 to 35) hours.After the vacuum separation is completed, the upper part of the material in the reaction vessel is set. A part near the center excluding the lower part and the outer peripheral part is commercialized.

By setting the vacuum separation time t to (to +15) hours or more, the specific surface area of the material in the reaction vessel near the center excluding the upper, lower, and outer peripheral parts is reduced, and low oxygen after cutting and crushing is reduced. Is realized. By commercializing the upper and lower parts of the material in the reaction vessel and the part near the center excluding the outer peripheral part, the content of each of the metal elements Fe, Ni, Cr, A1, and Si is also reduced. It is suppressed to a low level.

If the vacuum separation time exceeds the t force (t 0 +35) time, the specific surface area becomes too small, and cutting and crushing becomes difficult. Also, the thermoeconomics will be worse than necessary. The particularly preferable vacuum separation time t has a lower limit of (t 0 +20) hours or more and an upper limit of (t 0 +30) hours or less.

In actual operation, the temperature at the center of the titanium sponge material is not measured. From the temperature change data obtained by test operation and temperature analysis for each operating facility, determine the time until the center temperature reaches a stable temperature, and set the heating time in the vacuum separation process based on this time. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a vertical cross-sectional view of the titanium sponge material in the reaction vessel in the vacuum separation process. Fig. 2 shows the time-dependent temperature change of the titanium sponge material in the vacuum separation process. B s 1/2 The part shown for part C, Fig. 3 is a graph showing the preferred vacuum separation time in the vacuum separation process with the diameter of the reaction vessel (retort diameter) as a parameter, and Fig. 4 shows the different vacuum separation times. It is a micrograph of the sample taken from the central part of various kinds of sponge titanium materials. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.

The sponge titanium material is manufactured by melting Mg in a reaction vessel and dropping a titanium tetrachloride solution. When this reduction step is completed, the process proceeds to the vacuum separation step. In the vacuum separation process, the unreacted Mg and by-products are removed by evacuating the inside of the reaction vessel and heating it to a predetermined temperature with a heating furnace.

This vacuum separation step will be described in detail for the test operation example in FIG. The temperature Ta at the top A of the titanium sponge material in the reaction vessel slightly decreases at the beginning of the vacuum separation, but immediately rises and reaches a stable temperature in about 20 to 30 hours after the start of the vacuum separation. On the other hand, the temperature Tc at the center (1/2 part C) continues to drop for about 30 hours from the start of vacuum separation, and then rises to reach a stable temperature T0 70 hours after the start of vacuum separation.

In the past, vacuum separation was completed when the center temperature Tc reached the stable temperature To about 70 hours, and attempts to reduce this time are undeniable, and it is considered that this will be extended. Had not been. As a result, in the vicinity of the center where the amount of metal elements is small, heating in an empty state after evaporation of Mg is not performed, and sintering does not proceed, so that the specific surface area is not sufficiently reduced. For this reason, even if the portion near the center is sampled after vacuum separation, the increase in the amount of oxygen due to oxidization becomes remarkable in the cutting and crushing in the air atmosphere, and the level required for the evening getter for sputtering is low. Oxygenation is difficult to achieve o

Therefore, in the present embodiment, after the central portion temperature Tc reaches the stable temperature To, heating is continued for another 15 to 35 hours, preferably 20 to 30 hours. Thereby, even in the vicinity of the center where the amount of the metal element is small, the specific surface area by the BET method is reduced to 0.05 m ² / g or less due to the progress of sintering. As a result, cutting near the center after vacuum separation The increase in the amount of oxygen due to oxidation during the crushing process is suppressed, and the impurity level required for the evening getter material for sputtering can be achieved in both the amount of oxygen and the amount of metal elements.

In the sampling near the center after vacuum separation, as shown in Fig. 1, the lump height of sponge titanium material 10 is H, the lump diameter is D, and the thickness h1 from the upper surface is 0.1 H or more. The thickness h2 from the lower surface is 0.25 H or more, and the lower part is 0.18 D or more from the outer peripheral surface, and the outer peripheral part is 0.18 D or more. Collect a portion 11 near the center of less than 30% of the lump weight of 10.

The sample near the center 11 is usually cut and crushed in an air atmosphere to obtain titanium sponge particles having a predetermined particle size. Despite cutting and crushing in the air atmosphere, the amount of oxygen is suppressed to 300 ppm or less, and the amounts of metallic elements Fe, Ni, Cr, A1, and Si are also reduced. It is suppressed below 10 p pm. The average particle size after crushing is preferably 10 to 300 mm. FIG. 3 shows the result of investigation of a preferable vacuum separation time in the vacuum separation step. A preferable vacuum separation time is a region indicated by hatching in FIG. The vacuum separation time is affected by the diameter (retort diameter) of the reaction vessel, and the longer the diameter, the longer the time. The vacuum separation time in the present invention is +15 hours to +35 hours compared to the conventional vacuum separation time indicated by the solid line. After more than 15 hours, the specific surface area by the BET method in the vicinity of the center becomes less than 0.05 m ² / g, and the oxygen content after cutting and breaking becomes less than 300 ppm. In addition, the specific surface area by the BET method in the vicinity of the center becomes less than 0.03 m ² Zg in more than +20 hours, and the oxygen content after cutting and crushing becomes less than 200 ppm. When the specific surface area by the BET method is less than 0.01 m ² / g, cutting and breaking becomes difficult. The diameter (retort diameter) of the reaction vessel is preferably 135 to 200 mm. If it is less than 135 mm, metal impurities tend to increase even if the center is used. If it exceeds 2000 mm, equipment problems such as thermal deformation of the reaction vessel may occur.

By the way, the temperature change shown in Fig. 2 is when the diameter (retort diameter) of the reaction vessel is 100 mm, the conventional vacuum separation time is 70 hours, and in this case, the vacuum separation time in the present invention is 85 1105 hours, with 90-100 hours being especially preferred.

Micrographs of samples taken from the center of the sponge titanium material when the diameter (retort diameter) of the reaction vessel is 170 Qmm are shown for the cases where the vacuum separation time is 70 hours and 95 hours. 4 (a) and (b) show the same magnification.

Specific surface area by the BET method, vacuum separation time whereas a case 0. 1 m ² / g of 70 hours and the vacuum separation time is 9 5 hours a 0. 0 3m ² / g. This difference is also evident from Figs. 4 (a) and 4 (b). As a result of this difference in specific surface area, the amount of oxygen at the stage of cutting and crushing to an average particle size of 65 mm in the air atmosphere was 320 ppm when the vacuum separation time was 70 hours, and the vacuum separation time was 95 hours. In this case, it became 190 ppm. In each case, the content of each of Fe, Ni, Cr, A1, and Si was 10 ppm or less.

The shaded area in FIG. 3 is expressed by the following equation.

Vacuum separation time = (0.06 9 8 X [retort diameter] — 24) ± 10 BET method is a method of calculating the specific surface area from the absorbed amount of liquid nitrogen, which is widely used for adsorbents and the like. Used. Industrial applicability

As explained above, high-purity titanium sponge material of the present invention, by limiting the specific surface area by BET method is less than 0. 05 m ² Zg, cut crushed in the atmosphere means pursuant also the amount of oxygen in the low It is possible to economically secure the impurity level required for the evening getter material for sputtering, in combination with the reduction of metal impurities by centering.

In the method for producing a high-purity sponge titanium material of the present invention, the vacuum separation time t in the vacuum separation step is set such that the temperature Tc at the center of the material in the reaction vessel from the start of vacuum separation is set to a stable temperature To near the furnace temperature. By setting the time until the arrival at t 0 to t = t 0 + (15 to 35), the specific surface area by the BET method can be easily limited to 0.05 m ² Zg or less, The reduction of the amount of oxygen and the reduction of metal impurities by taking the center can economically secure the impurity level required for the target material for sputtering.

Claims

The scope of the claims

1. A sponge titanium material manufactured by the Kroll method, having a specific surface area measured by the BET method of 0.05 m ² / g or less, and Fe, Ni, Cr, A1, and S High purity in which the content of each metal element in i is 10 ppm or less

2. When producing titanium sponge material by the Kroll method, the vacuum separation time t in the vacuum separation process is set to the stable temperature T 0 near the furnace temperature, which is the temperature at the center of the material in the reaction vessel from the start of vacuum separation. Set the time until arrival to t0 to t = to + (15 to 35) hours, and after vacuum separation, commercialize the parts near the center excluding the upper, lower, and outer peripheral parts of the material in the reaction vessel High purity

)Production method.