JP2002332528A - Method for recycling high purity ruthenium, and method for producing target from recycled high purity ruthenium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily recycling high purity ruthenium from the scrap of ruthenium cut chips, mills ends or the like, and to inexpensively produce a sputtering target which has excellent properties from the high purity ruthenium obtained in this method. SOLUTION: Ruthenium scrap containing >=80 wt.% ruthenium is subjected to alkali or acid treatment to remove impurities stuck to the surface, and after that, its purity is made high by EB(electron beam) dissolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling high-purity ruthenium from scrap such as ruthenium chips or scraps and a method for producing a target from recycled high-purity ruthenium.

[0002]

2. Description of the Related Art In recent years, high-purity ruthenium has been used as an electronic material such as a ferroelectric electrode, a catalyst, or other raw material for processing. In general, when a ruthenium thin film is formed, a sputtering method is used. There are many. Although the sputtering method itself is a well-known method in the field of electronics, a high-purity ruthenium target having uniform and stable characteristics suitable for the sputtering is required. For example, materials used in recent electronics are required to have high purity for the purpose of preventing noise generation and improving characteristics, and a high purity ruthenium sputtering target is required to have a purity level of 5N. I have. On the other hand, in the process of manufacturing such a high-purity ruthenium target, a considerable amount of cuttings and scraps generated by flat grinding are generated. In the production of the target, it is desirable that such scraps can be reused. However, in the processing steps such as the above-mentioned cutting, the scraps are contaminated and a large amount of impurities are mixed. Particularly, contamination of oxygen and contamination from the cutting tool are remarkable. Although the amount of this impurity varies considerably depending on the processing conditions, the amount is as shown in Table 1.

[0003]

[Table 1]

In general, ruthenium materials are inexpensive for noble metals, but since ruthenium itself is a hardly soluble metal, it is very difficult to recycle such scraps when recycling such scraps. Disadvantage. However, commercially available 3N (99.
From a relatively low-purity ruthenium powder at a level of 9%) to a high-purity ruthenium sputtering target at a purity level of 5N, which is compatible with materials used in modern electronics, there is an additional process complexity and cost. The demand for scrap recycling is high, but there is no effective means at present. For this reason, a ruthenium scrap containing impurities is volatilized by arc melting or the like to evaporate the impurities to produce a metal ruthenium molten casting (ingot) whose purity has been increased, and a high-purity ruthenium sputtering target is to be manufactured therefrom. It is possible. However, there is a problem that the purity is not necessarily improved by this method, and that a molten cast product of metal ruthenium (an ingot) is hard and brittle, so that ordinary rolling, forging, and other processes are extremely difficult.

In general, as a method of processing such a difficult-to-process material, there is a method of rolling in a metal container (canning method). However, when rolling ingots of metallic ruthenium using this method, for example, when rolling,
In addition to the process of wrapping the metal ruthenium ingot with other metal sheets or foils, the process of removing it after rolling is extremely complicated, and the process becomes extremely complicated, and this also lowers the yield and significantly increases the cost. There were disadvantages. Therefore, even if a ruthenium target is conventionally produced on a trial basis by forging or rolling, it cannot be used in actual production.

For this reason, conventionally, a powder metallurgy method has been used to produce a high-purity ruthenium sputtering target. For example, a low-purity ruthenium powder is once purified by melting with an electron beam (EB), and then purified. A method has been adopted in which a ruthenium chloride is brought into contact with chlorine gas, which is further reduced with hydrogen to obtain a highly purified powder, which is further sintered and used as a sputtering target (JP-A-9-227965). And JP-A-9-227966.
reference). However, such a sintering method has many purification steps, and the final target has pores peculiar to the sintered body, which increases the adsorption of gas and the like. There is. Therefore, a melt-forged product (theoretically, a relative density of 1
(00%), it is inevitable that the characteristics are inferior, and the cost is high. Of course, the reuse of ruthenium scrap was not usually considered, and the increase in the sputtering target manufacturing cost as a whole was inevitable.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has established a method for easily recycling high-purity ruthenium from scrap such as ruthenium cuttings or scraps. It is an object of the present invention to provide a method for manufacturing a sputtering target excellent in characteristics at low cost from the obtained high-purity ruthenium.

[0008]

According to the present invention, a ruthenium scrap containing at least 1.80 wt% of ruthenium is treated with an alkali or an acid to remove impurities adhering to the surface, and is then highly purified by EB dissolution. A method for recycling high-purity ruthenium, characterized in that: 2. 2. The method for recycling high-purity ruthenium according to 1 above, wherein the oxygen content in ruthenium is 100 wtppm or less. 3. 3. The method for recycling high-purity ruthenium according to 1 or 2, wherein the recycling rate is 70% or more. Ruthenium scrap containing at least 4.80 wt% of ruthenium is treated with an alkali or an acid to remove impurities attached to the surface, and then highly purified by EB dissolution, and then solidified to form an ingot. A method for producing a high-purity ruthenium target, comprising forging an ingot at 1400 to 2000 ° C. 5. 5. The method for producing a high-purity ruthenium target according to the above item 4, wherein the ruthenium scrap is sintered at 800 to 1600 ° C. in an argon or hydrogen gas atmosphere and then EB-dissolved. 6. 6. The method for producing a high-purity ruthenium target according to 4 or 5, wherein the oxygen content is 100 wtppm or less. 7. 8. The method for producing a high-purity ruthenium target according to any one of the above items 4 to 7, wherein the average crystal grain size is 5 mm or less. 8. The method for producing a high-purity ruthenium target according to any one of the above items 4 to 7, wherein the method has a purity of 8.5N level or more (excluding gas components). 9. The above-mentioned item 4 wherein EB dissolution is performed twice or more.
9. The method for producing a high-purity ruthenium target according to any one of Items 1 to 8. I will provide a.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ruthenium scrap containing at least 80 wt% of ruthenium, for example, Na
After treating with an alkali such as a mixed solution of ClO and NaOH or an acid such as hydrofluoric acid to remove impurities such as SiO ₂ adhered to the surface, high purity is achieved by dissolving EB. By slightly dissolving the ruthenium surface by this alkali or acid treatment, impurities (WC
And SiC) can be removed. Gas components such as oxygen or volatile metals in ruthenium can be volatilized and removed during EB dissolution, and other impurities can be effectively removed as slag. And the oxygen content can achieve 100 wtppm or less. High-purity ruthenium recycling rate of 70
% Or more.

In manufacturing a high-purity ruthenium target, the above-mentioned ruthenium scrap containing at least 80 wt% of ruthenium is treated with an alkali or an acid to remove impurities attached to the surface, and then purified by EB dissolution.
Next, this is solidified to form an ingot, and the ingot is manufactured by forging at 1400 to 2000 ° C. When dissolving EB, ruthenium scrap (including powder) is solidified by mixing PVA (polyvinyl alcohol) or the like in advance, if necessary, and sintered at 800 to 1600 ° C. in an argon or hydrogen gas (non-oxygen, non-nitrogen) atmosphere. After sintering to obtain a sintered body, EB is melted. Sintering temperature 80
The reason for sintering in the range of 0 to 1600 ° C. is that splash during EB melting can be reduced.

It is desirable to carry out the EB dissolution twice or more. 1
This is because a large number of nests are apt to be generated in the EB dissolution at a time, and the quality and the yield are likely to be reduced. By this EB dissolution, as described above, the volatile components of the impurities present in ruthenium are removed and can be removed as slag. This makes it possible to easily obtain a high-purity ruthenium ingot having a 5N level (excluding gas components) from scrap. In particular, the oxygen content can be reduced to 100 wtppm or less.

Next, the 5N-level high-purity ruthenium ingot thus obtained is forged in a range of 1400 to 2000 ° C. If the temperature is lower than 1400 ° C., cracking is caused by forging, and if the temperature exceeds 2000 ° C., energy cost increases, which is not preferable. Further, if the temperature is lowered during forging, a crack occurs in the target material, so that constant temperature forging is desirable. Within the above temperature range, a forged product free from cracks can be obtained. It is processed by forging to a shape almost similar to the target, but the surface is further processed with a lathe or the like and finish processing is performed to finish the target. As a result, a high-purity ruthenium sputtering target having an average crystal grain size of 5 mm or less, uniform components, high density, and a level of 5N or more (excluding gas components) can be obtained at low cost. Further, the recycling rate can be 70% or more.

[0013]

Next, an embodiment will be described. It should be noted that the present embodiment is merely an example of the present invention, and the present invention is not limited to these embodiments. That is, it includes other aspects and modifications included in the technical idea of the present invention.

(Example 1) Ruthenium scrap having a total weight of about 11 kg consisting of plain steel, cutting chips and offcuts containing the impurities shown in Table 1 above was washed with a NaClO + NaOH detergent for 1 hour, and the ruthenium surface was removed. Was slightly dissolved and removed, and impurities adhering thereto were removed. next,
The washed scrap is mixed with PVA (polyvinyl alcohol) in advance and solidified.
It was sintered at 0 ° C. to obtain a sintered body. The sintered body thus obtained was subjected to EB melting three times to obtain an ingot of about 10 kg. The nest was small due to this dissolution. The slag floating above the ingot was removed by cutting. As a result, an ingot of about 9 kg was obtained. The ingot was further forged at 1600 ° C.
A plate of 0 × 8 mmt was obtained. This was turned into a high-purity ruthenium sputtering target. Table 2 shows the impurity concentrations of the target thus obtained. The concentrations in Table 2 are wtppm. Further, the average crystal grain size was about 2 mm.

[0015]

[Table 2]

As shown in Table 2, the contents of oxygen and nitrogen were less than 10 ppm, and a 5N level high purity ruthenium sputtering target could be obtained. According to the present invention, a high-purity, high-density target can be manufactured at low cost from ruthenium scrap that has been conventionally discarded. The recycling rate has reached 80% or more.

In the same manner as in Example 1, the total weight of the flattening material containing the impurities shown in Table 1 above, cutting chips and offcuts is about 11 k.
g of the ruthenium scrap was washed for one hour using a NaClO + NaOH detergent to dissolve and remove the ruthenium surface slightly and to remove impurities adhering thereto.
Next, the washed scrap is mixed with PVA (polyvinyl alcohol) in advance and solidified.
It was sintered at 1000 ° C. to obtain a sintered body. The sinter thus obtained was subjected to EB melting twice, to obtain an ingot of about 10 kg. The nest was small due to this dissolution. The slag floating above the ingot was removed by cutting. As a result, an ingot of about 9 kg was obtained. This ingot is further forged at 1800 ° C.
A plate of φ350 × 8 mmt was obtained. This was turned into a high-purity ruthenium sputtering target. The analysis results of the target thus obtained were the same as those in Table 2 of Example 1, and the results were good, but the average crystal grain size was about 4 mm.

Comparative Example 1 An ingot was obtained using the same materials as in Example 1 except that the EB melting was performed once, and under the same conditions. However, because the EB dissolution is not sufficient, there are many nests in the ingot, and it is necessary to delete many portions where the nests have occurred from the ingot, so that the yield has deteriorated. In addition, foreign substances such as SiC were also observed. Therefore, the subsequent forging process was not performed.

Using the same material as in Example 1, EB melting was performed three times, and an ingot was obtained under the same conditions except for the above. Then, it was forged at 1300 ° C. However, processing of the ingot was difficult due to the low forging temperature, and cracks occurred. For this reason, processing on the target was suspended.

[0020]

The present invention has the advantage that high-purity ruthenium can be easily recycled using scraps of ruthenium cuttings or scraps. It is not necessary to take complicated and cost-increasing methods such as wrapping (canning method) and rolling. Also, there is no porosity (density reduction) peculiar to powder metallurgy. It has an excellent effect that a small, high-purity, high-density ruthenium sputtering target can be obtained at low cost.

Claims (9)

[Claims] 1. A method for recycling high-purity ruthenium, comprising subjecting a ruthenium scrap containing at least 80 wt% ruthenium to an alkali or acid treatment to remove impurities attached to the surface, and then purifying the ruthenium by EB dissolution. . 2. The oxygen content in ruthenium is 100 wt.
2. The method for recycling high-purity ruthenium according to claim 1, wherein the content is less than ppm. 3. The method for recycling high-purity ruthenium according to claim 1, wherein the recycling rate is 70% or more. 4. Ruthenium scrap containing at least 80 wt% of ruthenium is treated with an alkali or an acid to remove impurities attached to the surface, and then purified by EB dissolution, and then solidified to form an ingot. A method for producing a high-purity ruthenium target, further comprising forging the ingot at 1400 to 2000 ° C. 5. After sintering ruthenium scrap at 800 to 1600 ° C. in an argon or hydrogen gas atmosphere,
The method for producing a high-purity ruthenium target according to claim 4, wherein EB is dissolved. 6. The method for producing a high-purity ruthenium target according to claim 4, wherein the oxygen content is 100 wtppm or less. 7. The method for producing a high-purity ruthenium target according to claim 4, wherein the average crystal grain size is 5 mm or less. 8. The method for producing a high-purity ruthenium target according to claim 4, wherein the target has a purity of 5N level or more (excluding gas components). 9. The method for producing a high-purity ruthenium target according to claim 4, wherein EB melting is performed twice or more.