JP3292060B2 - Deoxygenation method of scandium metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for deoxidizing scandium metal.

[0002]

2. Description of the Related Art Scandium (Sc) is an element which is expected to be widely used as a raw material for a catalyst, a phosphor or a heat conductive material. In addition, S (Al)
If c is contained in an amount of about 0.01 to 1%, the strength is improved. Therefore, c is recently added to an Al-based target material and used as a material for a gate electrode or a wiring of a semiconductor.

At present, as a general method for producing scandium, scandium oxide (Sc ₂ O ₃ ) obtained from scandium ore is treated with hydrofluoric acid to precipitate hardly soluble scandium fluoride (ScF ₃ ). Is filtered, dried and then reduced with calcium. However, since scandium has a strong affinity for oxygen, the metal scandium obtained by the above-mentioned production method is at least 2000 ppm.
Contains about oxygen.

However, when the oxygen concentration in scandium is high, its properties are often adversely affected. For example, when used as a wiring material, a high oxygen content causes an increase in resistance, which causes signal delay and disconnection. Therefore, there is a need for a method for reducing the oxygen concentration in scandium metal.

As a laboratory method, there is a method in which metal scandium is heated to about 1500 ° C. above its melting point (about 1400 ° C.) and distilled in a vacuum (FHSpedding et al.).
l. "The resistivity of scandium sigle crystals",
J. Less-Common Metals, 23 , 263-270 (1971)). However, such a method is disadvantageous in terms of equipment cost and energy cost, and is not suitable as an industrial deoxygenation method.

For a rare earth element other than scandium, there is a method of adding a corresponding rare earth fluoride and alkaline earth fluoride to the rare earth metal and heating and melting in an inert gas or vacuum to deoxygenate. It has been proposed (Japanese Patent Publication No. 5-83622). However, scandium is not included in the above literature. Further, in this method, since fluoride is handled at a high temperature of about 1500 ° C., even if a crucible having high heat resistance, such as a graphite crucible or a tantalum crucible, is used, the material of the crucible (eg, C or Ta) is attacked. A new problem of mixing in rare earth metals.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional metal scandium, and provides an efficient and cost-effective method for deoxidizing metal scandium.

That is, according to the present invention, there is provided a method for deoxidizing metal scandium having the following constitution. (1) Metallic scandium is alloyed with a low melting point, and the scandium halide, from which oxygen has been removed in advance in a halogen gas atmosphere under heating, is brought into contact with the low-melting liquid of the metal scandium to convert oxygen in the alloy into halogen. A method for deoxidizing metal scandium, comprising reducing the oxygen concentration by causing the metal to be absorbed by scandium halide. (2) Mg, Al, Ga, In, Se, Te, Mg, Al, Ga, In, Se, Te
The deoxidation method according to the above (1), wherein at least one metal selected from Zn and Cd is used. (3) The scandium halide to be brought into contact with the low-melting liquid of scandium metal is prepared by adding calcium chloride and / or calcium fluoride to the scandium halide in advance, and introducing chlorine gas into the mixed melt under heating and melting. The deoxygenation method according to the above (1) or (2), wherein the oxygen is removed from the mixture. (4) After deoxidation by the method of (1), (2) or (3), the slag layer and the alloy layer are separated, and the alloy is heated to about 1000 to 1100 ° C. in vacuum, A method of obtaining purified metal scandium by volatilizing and separating a metal element added to scandium. (5) Scandium halide is scandium fluoride
The method according to any one of the above (1) to (4), which is (ScF ₃ ).

[0009]

[Specific description] (I) Metal scandium Metal scandium (abbreviated as metal Sc) to be treated in the present invention may be obtained by any scouring method. Above general procedure, i.e., the Sc ₂ O ₃ obtained from the ore is treated with hydrofluoric acid to precipitate ScF ₃ of poorly soluble, after which was filtered dried, be those obtained by the method of reduction with Ca or the like well,
After converting Sc ₂ O ₃ to a halide other than fluorine, for example, a chloride, it may be obtained by subjecting it to molten salt electrolysis.
Further, a material recovered using an ion exchange resin or the like may be used, or a method other than these methods may be used. Further, it is possible to further remove oxygen from the purified metal Sc whose oxygen concentration has been reduced by the method of the present invention.

(II) Alloy-forming element The alloy-forming element (Y) added to the metal Sc for producing the low-melting scandium alloy is an element that can be easily removed from the metal Sc after the deoxidation treatment, or Sc It is a metal element that is not harmful in view of its intended use. Examples of the former include Mg, Se, Te, Zn, Cd and the like. For example, Mg (boiling point: about 1102 ° C.) can be volatilized and removed by vacuum distillation. The same applies to Zn (boiling point: about 907 ° C.). Examples of the latter include Al, Ga, I
n and the like. For example, when used as a target material by being added to Al, mixing of Al is usually allowed.

(III) Deoxidizing Method The deoxidizing method of the present invention comprises (a) a melting step by forming a low melting point Sc alloy, (b) a pretreatment step of ScX ₃ , (c) a deoxidizing step, and (D) a dealloying step performed in accordance with (A) Melting step by alloy formation Low melting point S by adding the above alloying element to metal Sc
A c alloy is formed. The amount of addition to Sc differs depending on the type of the added metal or the purpose of use of Sc, but usually, the melting point after alloying is 900 to 1300 ° C.
The amount is reduced to the extent. Generally, it is in the range of 50-90%, preferably 70-80% by weight.
If the amount of the added element is too small, the melting point will not be sufficiently reduced.
If the amount is excessive, it causes a problem in use after removal or deoxidation in a later step.

These metals may be alloyed in addition to the metal Sc obtained by refining in advance.
In the manufacturing process of c, an alloy with these metal elements may be manufactured without isolating the metal Sc. FIG.
Shows such an example.

In the example shown in FIG. 1, Sc ₂ O ₃ as a raw material is first dissolved with hydrochloric acid. Then to produce ScF ₃ was added hydrofluoric acid of about 1~3M to the solution. Highly soluble ScC
Unlike l ₃ , ScF ₃ is hardly soluble and precipitates.
This is filtered off and dried. Then, low melting point S was added to ScF _3.
A Zn-Ca alloy for forming a c-alloy is added together with CaCl ₂ (step at the upper right of FIG. 1), and is melt-reduced to obtain Sc-Zn.
Obtain a melt of the alloy. By leading this Sc—Zn alloy directly to the deoxidizing step (the lower step in FIG. 1), the entire manufacturing process of the metal Sc can be simplified, and there is no need to repeat melting and solidification, thereby eliminating waste of energy costs. .

In the above process, CaCl ₂
Is an additive mainly for lowering the melting point of the raw material ScF ₃ , usually 50 to 90% by weight based on ScF ₃
What is necessary is just to add. Magnesium chloride, calcium fluoride, etc. may be used instead of CaCl ₂ . The Zn-Ca alloy used as the alloy-forming material may be a combination of an alloy-forming element (Y) for forming a low-melting-point Sc alloy and a metal element (Z) having a reducing power for the raw material ScF ₃ . It is sufficient that these metal elements Y and Z are not limited to alloyed ones.
May be used individually. The alloy forming element (Y) is as described above, and the metal element (Z) having a reducing power for ScF ₃ is magnesium in addition to Ca.
(Mg) or lithium (Li) is used. Reducing metal (Z)
Is added to 1.5 equivalents of ScF ₃ as a raw material.
About 4 equivalents is appropriate.

[0015] While oxygen is carried out by contacting the SCX ₃ to melt pretreatment step the low-melting Sc alloy (b) SCX _3, Prior to this, SCX ₃
Is preferably pretreated with a halogen gas to remove or reduce oxygen in ScX ₃ . In general, the synthesis of pure ScX ₃ is difficult, and hypohalite (ScOx)
Are mixed. With such a SCX _3,
It is difficult to reduce the amount of oxygen in the metal Sc to about 1000 ppm or less. Therefore, a halogen gas (chlorine gas or fluorine gas) is previously introduced into ScX ₃ as an oxygen scavenger, and oxygen such as hypohalite is gasified and desorbed.

For example, deoxidation with chlorine gas can be performed by maintaining ScX ₃ heated to about 800 to 900 ° C. in a dry chlorine gas atmosphere for about 30 to 60 minutes. Preferably, 70 against SCX ₃
About 90% by weight of CaCl ₂ and / or CaF ₂ is added, melted by heating (about 900 to 1000 ° C.), and dry chlorine gas is introduced therein. This mixture comprises ScX ₃ and CaCl ₂
Although it is a mixed melt of CaX ₂ , it can be used as it is in the deoxygenation step. After completion of deoxidation, these calcium salts form a slag layer containing ScX ₃ or the like on the metal S.
It is easy to peel off from the c layer.

(C) Deoxygenation Step By bringing the melt of the Sc low melting point alloy into contact with ScX ₃ , oxygen in the Sc low melting point alloy is removed. The oxygen in the alloy is absorbed by pure ScX ₃ as shown in the following formula:
It becomes ScOX and is removed. O + ScX ₃ → ScOX + X ₂ Sc The contact between the low melting point combined liquid and ScX ₃ can be carried out by any method. For example, the solid Sc low melting point alloy and ScX ₃ may be mixed and then heated and melted, or ScX ₃ may be added after the Sc low melting point alloy is heated and melted. In terms of energy costs,
Lead to Sc alloy prepared in step (b) leave deoxidation step in the molten state, _{(preferably, ScX 3 -CaCl 2 -CaF 2)} ScX 3 prepared in the step (b) to this added melt It is preferable to mix and stir in an atmosphere of an inert gas such as helium.

The mixing ratio of ScX ₃ and Sc low melting point alloy (S
cX ₃ : Sc low melting point alloy) is preferably 2: 3 to 4:
1, more preferably about 1: 1 to 2: 1. Note that S
When cX ₃ is a mixture with the above calcium salt, an Sc low melting point alloy in the above range is suitable for ScX _{3 in} the mixture. When the mixing ratio is less than 2: 3, the oxygen removing effect is not sufficiently exhibited. When the ratio exceeds 4: 1, the effect is saturated, and a sufficient treatment effect is not exhibited on the scale of equipment such as a reaction vessel.

According to the method of the present invention, the deoxidizing treatment can be performed at a temperature of about 900 to 1300 ° C. by using the low melting point Sc alloy. As a result, even if an ordinary crucible such as a graphite crucible or a Ta crucible is used, contamination by the crucible component does not progress. Further, by using ScX ₃ from which oxygen is substantially completely removed as described above, the oxygen concentration in the metal Sc can be reduced to about 500 ppm or less. Scandium fluoride (ScF ₃ ) is preferred as ScX ₃ because of its low hygroscopicity and easy handling.

(D) Dealloying Step When the alloy forming element is at least one metal selected from Mg, Se, Te, Zn or Cd, the low oxygen content obtained in the deoxidizing step is usually These metal elements can be easily removed from the Sc alloy by vacuum separation. Vacuum separation of the Sc alloy above about 1000 in vacuum
Performed by heating to ~ 1100 ° C. The above-mentioned metal elements excluding Sc in the alloy components are volatilized by vacuum separation, and a sponge-like purified metal Sc is obtained.

[0021]

EXAMPLES AND COMPARATIVE EXAMPLES Example 1 37.8 g of oxidized Sc powder (purity: 99.9%) was dissolved in 250 ml of a special grade reagent, hydrochloric acid, and ion-exchanged water was added.
0 ml of an aqueous Sc chloride solution was obtained. 100 ml of semiconductor-grade pure hydrofluoric acid was added thereto to generate a Sc fluoride precipitate, which was collected by filtration, dried at 300 ° C., and dried at 300 ° C.
53 g of a powder were obtained. Using 40 g of this fluorinated Sc powder,
Metallic 16g, zinc 94g, calcium chloride 8
The mixture was placed in a 500 ml tantalum crucible together with 8 g, and reacted at 950 ° C. for 1 hour under an argon gas atmosphere. After the reaction is completed, the contents are taken out by cooling to room temperature in the same atmosphere, and the slag layer (flux layer) and alloy layer (Sc-Zn alloy)
And separated. On the other hand, the fluorinated Sc3
0 g was put in a glassy carbon crucible together with 88 g of calcium chloride, heated to 900 ° C. and melted, and chlorine gas was blown into the melt at a rate of 200 ml / min for 2 hours to cause a reaction. After the reaction was completed, the crucible was taken out at room temperature, and a fluorinated Sc-Ca chloride mixture was taken out. Furthermore, the Sc-
The Zn alloy and this fluorinated Sc-Ca chloride mixture were placed in a 500 ml tantalum crucible and reacted again at 950 ° C. for 1 hour in a reaction vessel in an argon gas atmosphere. After the reaction is completed, the crucible is taken out at room temperature, and the slag layer and Sc are removed.
-Separated from the Zn alloy layer. Next, 92 g of the above alloy was crushed to about 1 cm in a glove box in an argon atmosphere, put again in a tantalum crucible, and placed in a vacuum vessel at 1000 g.
The solution was heated at a temperature of 5 ° C. for 5 hours to remove Zn and obtain a purified metal Sc. The oxygen concentration in the raw material Sc and the purified Sc was measured by a combustion infrared absorption method. As a result, it was confirmed that the oxygen concentration in the raw material, which was 2000 ppm, could be reduced to 450 ppm by the treatment of the present invention.

Example 2 40 g of Sc fluoride powder prepared in the same manner as in Example 1, 6 g of calcium metal particles, and aluminum 10 having a purity of 99.999%
0 g and 120 g of calcium chloride together with a tantalum crucible having an inner volume of 500 ml.
The reaction was carried out at a temperature of 1 hour. After the completion of the reaction, the content was taken out by cooling to room temperature in the same atmosphere, and the slag layer (flux layer) and the alloy layer were separated. On the other hand, 30 g of Sc fluoride obtained in the same manner was put into a glassy carbon crucible together with 88 g of calcium chloride.
The melt was blown into the melt at a rate of 0 ml / min for 2 hours to cause a reaction. After the reaction was completed, the crucible was taken out at room temperature, and a fluorinated Sc-Ca chloride mixture was taken out. Further, the alloy layer and the fluorinated Sc-Ca chloride mixture were placed in a tantalum crucible having an inner volume of 500 ml, and reacted again at 950 ° C. for 1 hour in a reaction vessel in an argon gas atmosphere. After the reaction, take out the crucible at room temperature, separate the slag layer and the alloy layer,
110 g of a purified Sc-Al alloy was obtained. When the oxygen concentration in the purified Sc-Al alloy was measured in the same manner as in Example 1,
The oxygen concentration was 700 ppm.

Example 3 3.6 g of the purified metal Sc obtained in Example 1 was added to 300 g of aluminum having a purity of 99.999%, melted at 800 ° C. in a vacuum, and cast. After keeping the obtained ingot at 520 ° C. for 10 hours, it was subjected to cold rolling at a rolling reduction of 80%, and further 420
Heat treatment was performed at 30 ° C. for 30 minutes. Using the obtained material, a sputtering target having a diameter of 120 mmφ and a thickness of 2 mm was prepared. Using this target, a wiring pattern was formed by a sputtering method and a lithography method. The width of each wiring in the wiring pattern is 2μm, length 3mm,
The thickness was 1 μm, and ten wirings were selected for each sample target. Each wiring was energized to perform an accelerated reliability test. Test conditions were: substrate temperature 150 ° C, current density 5 × 10
⁶ A / cm ² . For each wiring obtained from each sample target, the ratio of the number of broken wires to the total number of wires was calculated, and the reliability of the wiring was evaluated. Table 1 shows the results.

Example 4 1.5 g of the purified Sc—Al alloy obtained in Example 2 and a purity of 99.999
% Of aluminum was melted in a vacuum at 800 ° C., and a wiring was manufactured in the same manner as in Example 3, and the reliability was examined. Table 1 shows the results.

COMPARATIVE EXAMPLE 1 The reliability of wiring was tested in the same manner as in Example 3 except that commercially available metal Sc (oxygen concentration: 2000 ppm) was used. Table 1 shows the results.

[0026]

As is apparent from the results, the Al-Sc wiring material of the present invention using the metal Sc having a low oxygen content has a disconnection occurrence rate of half or less as compared with the conventional product, and is excellent in reliability. Understand.

[0028]

According to the present invention, a low oxygen concentration of about several hundred ppm, which cannot be achieved by the conventional method, can be easily realized, so that a wide range of applications can be achieved without impairing the original characteristics of the metal Sc. In particular, when used as an Al-Sc wiring material, the rate of disconnection and signal delay are remarkably improved as compared with conventional products, and a product having high reliability and excellent electrical characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing a process for producing low oxygen Sc according to the present invention.

Continuation of the front page (56) References JP-A-7-90411 (JP, A) JP-A-63-161130 (JP, A) JP-A-1-116038 (JP, A) JP-B-5-85627 (JP) , B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (5)

(57) [Claims] 1. A method according to claim 1, wherein the metal scandium is alloyed with a low melting point, and the scandium halide from which oxygen has been removed in advance in a halogen gas atmosphere under heating is brought into contact with the low-melting alloy liquid of the metal scandium, thereby obtaining oxygen in the alloy. Deoxygenation of metal scandium by absorbing oxygen into scandium halide to reduce the oxygen concentration. 2. As a metal added to scandium metal to form a low melting point alloy, Mg, Al, Ga, In, S
2. The deoxidation method according to claim 1, wherein at least one metal selected from e, Te, Zn, and Cd is used. 3. A scandium halide to be brought into contact with a low-melting-point metallurgical solution of scandium metal is prepared by adding calcium chloride and / or calcium fluoride to scandium halide in advance, and adding chlorine gas to the mixed melt under heating and melting. 3. The method according to claim 1, wherein oxygen is introduced to remove oxygen.
Deoxygenation method. 4. After deoxidizing by the method of claim 1, 2 or 3, the slag layer and the alloy layer are separated, and the alloy is heated to about 1000 to 1100 ° C. in a vacuum to convert the alloy into scandium. A method of obtaining purified metal scandium by volatilizing and separating the added metal element. 5. The method according to claim 1, wherein the scandium halide is scandium fluoride (ScF ₃ ).