High purity hafnium, target and thin film comprising said high purity hafnium, and method for producing high purity hafnium

- Nikko Materials Co., Ltd.

The present invention relates to high purity hafnium having a purity of 4N or higher excluding zirconium and gas components and an oxygen content of 40 wtppm or less, and a target and thin film formed from such high purity hafnium, and high purity hafnium having a purity of 4N or higher excluding zirconium and gas components and in which the content of sulfur and phosphorus is respectively 10 wtppm or less. The present invention also relates to a high purity hafnium material which uses a hafnium sponge with reduced zirconium as the raw material, and in which the content of oxygen, sulfur and phosphorus containing in the hafnium is reduced, as well as to a target and thin film formed from such material, and to the manufacturing method of high purity hafnium. Thereby provided is efficient and stable manufacturing technology which enables the manufacture of a high purity hafnium material, and a target and thin film formed from such material.

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Description
TECHNICAL FIELD

The present invention relates to a high purity hafnium material in which the content of impurities such as zirconium, oxygen, sulfur and phosphorus contained in the hafnium is reduced, as well as to a target and thin film formed from such high purity hafnium material, and a manufacturing method of high purity hafnium.

BACKGROUND ART

Conventionally, there are numerous documents relating to the manufacture of hafnium, and, since hafnium and zirconium are very similar in terms of atomic structure and chemical property, the inclusion of zirconium or the inclusion of zirconium in hafnium was never really acknowledged as a problem as exemplified below.

Hafnium and zirconium are superior in heat resistance and corrosion resistance, and are characterized in that they have a strong affinity with oxygen and nitrogen. And, since the oxides or nitrides thereof have superior stability in high temperatures, they are utilized as fire-resistant materials in the manufacture of nuclear ceramics, steel or castings. Further, recently, these are also being used as electronic materials or optical materials.

The manufacturing method of metal hafnium or metal zirconium is proposed as the same manufacturing method. As such example, there is a method of reacting a fluorine-containing zirconium or hafnium compound with metal aluminum or magnesium in inert gas, reducing gas or vacuum at a temperature of 400° C. or higher (e.g., refer to Patent Document 1); a manufacturing method of reducing zirconium chloride, hafnium chloride or titanium chloride and manufacturing the respective metals thereof characterized in the sealing metal (e.g., refer to Patent Document 2); a manufacturing method of hafnium or zirconium characterized in the reaction container structure upon reducing zirconium tetrachloride or hafnium tetrachloride with magnesium and the manufacturing technique thereof (e.g., refer to Patent Document 3); a method of manufacturing chloro-, bromo- or iodic zirconium, hafnium, tantalum, vanadium and niobium compound vapor by introducing these into a crucible (e.g., refer to Patent Document 4); a method of refining zirconium or hafnium chloride or an acid chloride aqueous solution with strongly basic anion exchange resin (e.g., refer to Patent Document 5); a method of collecting zirconium via solvent extraction (e.g., refer to Patent Document 6); and a crystal bar hafnium manufacturing device having characteristics in the feed portion (e.g., refer to Patent Document 7).

[Patent Document 1] Japanese Patent Laid-Open Publication No. S60-17027

[Patent Document 2] Japanese Patent Laid-Open Publication No. S61-279641

[Patent Document 3] Japanese Patent Laid-Open Publication No. S62-103328

[Patent Document 4] WO89/11449

[Patent Document 5] Japanese Patent Laid-Open Publication No. H10-204554

[Patent Document 6] Japanese Patent Laid-Open Publication No. S60-255621

[Patent Document 7] Japanese Patent Laid-Open Publication No. S61-242993

As described in the foregoing documents, although there are numerous refining methods and extraction methods of zirconium and hafnium, the inclusion of zirconium or the inclusion of zirconium in hafnium was never really acknowledged as a problem.

Nevertheless, in recent years, deposition on electronic components using hafnium silicide is being demanded. In such a case, even zirconium is an impurity, and there is a possibility that the required characteristics of the hafnium raw material may become unstable. Therefore, there is demand for a high purity hafnium material with reduced zirconium, and a target and thin film formed from such a material.

However, since there was no notion of separating hafnium and zirconium as described above, the actual condition is that there is no efficient and stable manufacturing technology for obtaining the foregoing high purity hafnium material with reduced zirconium, and a target and thin film formed from such a material. Further, since it is difficult to efficiently eliminate the impurities of oxygen, sulfur and phosphorus, this is another reason that high purification has been neglected heretofore.

In particular, materials having a high residual resistance ratio are being demanded, and, since a high purity hafnium material could not be obtained conventionally, it was not possible to sufficiently meet the demands as electronic component materials since the residual resistance ratio was low.

DISCLOSURE OF THE INVENTION

Thus, an object of the present invention is to provide a high purity hafnium material which uses a hafnium sponge with reduced zirconium as the raw material, and in which the content of oxygen, sulfur and phosphorus contained in the hafnium is reduced, as well as to a target and thin film formed from such material, and to the manufacturing method of high purity hafnium. Thereby provided is efficient and stable manufacturing technology which enables the manufacture of a high purity hafnium material, and a target and thin film formed from such material.

MEANS FOR SOLVING PROBLEMS

In order to achieve the foregoing object, as a result of intense study, the present inventors discovered that the intended high purity hafnium can be manufactured by using a hafnium sponge with reduced zirconium developed previously by the inventors as the raw material, and further performing electron beam melting and deoxidation with molten salt so as to efficiently separate oxygen, sulfur and phosphorus, and, as necessary, further performing electron beam melting.

Based on the foregoing discovery, the present invention provides:

1) High purity hafnium and a target and thin film formed from the high purity hafnium having a purity of 4N or higher excluding zirconium and gas components, and an oxygen content of 40 wtppm or less;

2) High purity hafnium and a target and thin film formed from the high purity hafnium having a purity of 4N or higher excluding zirconium and gas components, and in which the content of sulfur and phosphorus is respectively 10 wtppm or less;

3) High purity hafnium and a target and thin film formed from the high purity hafnium according to paragraph 1) above having a purity of 4N or higher excluding zirconium and gas components, and in which the content of sulfur and phosphorus is respectively 10 wtppm or less;

4) High purity hafnium and a target and thin film formed from the high purity hafnium according to any one of paragraphs 1) to 3) above having a purity of 4N or higher excluding zirconium and gas components, and in which the zirconium content is 0.5 wt % or lower;

5) A manufacturing method of high purity hafnium wherein a hafnium sponge raw material is subject to solvent extraction and thereafter dissolved, and the obtained hafnium ingot is further subject to deoxidation with molten salt; and

6) The manufacturing method of high purity hafnium according to paragraph 5) above wherein, after performing deoxidation with molten salt, electron beam melting is further performed.

[Effect of the Invention]

The present invention yields a superior effect in that it is capable of stably manufacturing high purity hafnium by using a hafnium sponge in which the zirconium in the hafnium is eliminated as the raw material, and further performing electron beam melting and deoxidation with molten salt to this hafnium sponge. Further, by manufacturing a sputtering target with the high purity hafnium ingot obtained as described above and performing sputtering with this target, it is possible to obtain a high purity hafnium thin film. Moreover, it is possible to obtain a thin film having a high residual resistance ratio from the high purity hafnium material, which will be able to sufficiently meet the demands as an electronic component material.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, a hafnium sponge from which zirconium has been eliminated is used as the raw material. Upon eliminating zirconium from hafnium, a method invented previously by the present inventors may be adopted, or another raw material may be used so as long as it is hafnium with reduced zirconium.

The previous invention as a method for reducing zirconium is introduced below.

Hafnium tetrachloride (HfCl4) is used as the raw material. A commercially available material can be used as the hafnium tetrachloride. This commercially available hafnium tetrachloride contains roughly 5 wt % of zirconium. Incidentally, hafnium (Hf) metal or hafnium oxide (HfO2) may also be used as the raw material.

These raw materials have a purity level of 3N excluding zirconium, and contain iron, chrome and nickel as main impurities other than zirconium.

First, this hafnium tetrachloride raw material is dissolved in purified water. Next, this is subject to multistage organic solvent extraction. Normally, solvent extraction is performed in 1 to 10 stages. TBP may be used as the organic solvent.

As a result, zirconium can be made to be 5000 wtppm or less, and can be further made to be 1000 wtppm or less by repeating solvent extraction. Further, the total content of other impurities can be made to be 1000 wtppm or less.

Next, neutralization treatment is performed to obtain hafnium oxide (HfO2). This hafnium oxide is subject to chlorination to obtain high purity hafnium tetrachloride (HfCl4), and this is further reduced with, for instance, magnesium metal having chloridization power that is stronger than hafnium or zirconium to obtain a hafnium sponge. As the reducing metal, in addition to magnesium, for instance, calcium, sodium, and so on may be used.

In the present invention, the hafnium sponge obtained as described above is once subject to electron beam melting (hearth melting) in a Cu crucible. Thereafter, the hafnium sponge is sequentially placed therein. The hafnium molten metal overflowing from the upper part of the pool flows into the upper part of the ingot. This is still in a molten metal state, and the purity can be improved by performing the two melting processes with a series of electronic beam operations at the stages of hearth melting and manufacturing the ingot.

Thereafter, the obtained ingot is subject to deoxidation with molten salt. This deoxidation process, as described later, is able to eliminate carbon, sulfur, phosphorus and other impurities. Specifically, it is possible to make oxygen 40 wtppm or less, and sulfur and phosphorus respectively 10 wtppm or less. In the foregoing process, zirconium can be made to be 5000 wtppm or less, and further 1000 wtppm.

Like this, it is possible to obtain a high purity hafnium ingot having a purity of 4N (99.99 wt %) or higher excluding gas components such as carbon, oxygen and nitrogen, and zirconium.

Further, it is possible to use this high purity hafnium to manufacture a high purity hafnium target, and it is further possible to deposit high purity hafnium on a substrate by performing sputtering with this high purity target.

Moreover, a material having a high residual resistance ratio can be obtained from the foregoing high purity hafnium material as described in the following Examples, and it is possible to sufficiently meet the demands as an electronic component material.

The target may be manufactured with the ordinary processing steps of forging, rolling, cutting, finishing (polishing) and so on. There is no particular limitation in the manufacturing method thereof, and the method may be selected arbitrarily.

EXAMPLES

Examples of the present invention are now explained. These Examples are merely illustrative, and the present invention shall in no way be limited thereby. In other words, the present invention shall only be limited by the scope of the present invention, and shall include the various modifications other than the Examples of this invention.

Example 1

100 Kg of commercially available hafnium tetrachloride (HfCl4) shown in Table 1 having a purity of 3N and containing roughly 5000 wtppm of zirconium was used as the raw material, and this was dissolved in 1 L of purified water to create a nitric acid solution.

This raw material contained 500 wtppm, 40 wtppm and 1000 wtppm of iron, chrome and nickel, respectively, as its main impurities in HfCl4.

Next, this hafnium raw material (a nitric acid solution) was subject to 4-stage organic solvent extraction using a TBP organic solvent, and neutralization treatment was performed to obtain hafnium oxide (HfO2).

Further, this hafnium oxide was subject to chlorination to obtain high purity hafnium tetrachloride (HfCl4), and then subject to magnesium reduction to obtain a hafnium sponge as the raw material. This hafnium sponge contained 300 wtppm of zirconium, and the total content of other impurities was reduced to 300 wtppm.

Next, the obtained hafnium sponge was used as the raw material, and further subject to two-stage melting via hearth melting and ingot melting with an electron beam to remove volatile elements, gas components and so on. As a result of the foregoing process, although the zirconium content did not change at 300 wtppm, iron, chrome, nickel and other impurities were reduced to 70 wtppm as shown in Table 1, and further resulted in O: 250 wtppm, C: 50 wtppm, N: <10 wtppm, S: <10 wtppm, P: <10 wtppm.

Next, the hafnium thus obtained was subject to deoxidation at 1200° C. for 5 hours with molten salt of Ca and CaCl2. Reduction was realized where O: <10 wtppm and C: <10 wtppm, and other impurities were also reduced to 30 wtppm.

Accordingly, it is possible to obtain a high purity hafnium ingot having a purity level of 4N (99.99 wt %) excluding zirconium.

The sputtering target obtained from this ingot is also capable of maintaining high purity, and, by performing sputtering with this target, a uniform high purity hafnium thin film can be formed on a substrate.

TABLE 1 wtppm O C N S P Zr Others Raw Material — — — 20 20 5000 800 Ingot 250 50 <10 <10 <10 300 70 Deoxidation <10 <10 <10 <10 <10 300 30

Example 2

100 Kg of hafnium metal raw material (zirconium content of 2 wt %) shown in Table 2 was used and dissolved in nitric-hydrofluoric acid. This raw material contained 15000 wtppm, 8000 wtppm and 5000 wtppm of iron, chrome and nickel, respectively, as its main impurities in the raw material.

Next, this hafnium raw material was subject to 10-stage organic solvent extraction using a TBP organic solvent, and neutralization treatment was performed to obtain hafnium oxide (HfO2).

Further, this hafnium oxide was subject to chlorination to obtain high purity hafnium tetrachloride (HfCl4), and then subject to calcium reduction to obtain a hafnium sponge. This hafnium sponge contained 1500 wtppm of zirconium, and the total content of other impurities was reduced to 1000 wtppm.

Next, the obtained hafnium sponge was used as the raw material, and further subject to two-stage melting via hearth melting and ingot melting with an electron beam to remove volatile elements, gas components and so on. As a result of the foregoing process, as shown in Table 2, realized was O: 400 wtppm, C: 30 wtppm, N: <10 wtppm, S: 10 wtppm, P: 10 wtppm.

Next, the hafnium thus obtained was subject to deoxidation at 1200° C. for 10 hours with molten salt of Mg and MgCl2. Reduction was realized where O: 20 wtppm and C: 10 wtppm, and other impurities were also reduced to 50 wtppm.

With the sputtering target obtained from this ingot, as with Example 1, a uniform high purity hafnium thin film can be formed on a substrate.

TABLE 2 wtppm O C N S P Zr Others Raw Material 10000 5000 4000 100 50 20000 30000 Ingot 400 30 <10 10 10 1500 100 Deoxidation 20 10 <10 <10 <10 1500 50

Example 3

100 Kg of hafnium oxide (HfO2) raw material (3N level) shown in Table 3 was used and dissolved in nitric-hydrofluoric acid. This raw material contained 15000 wtppm, 8000 wtppm and 5000 wtppm of iron, chrome and nickel, respectively, as its main impurities in the raw material.

Next, this hafnium oxide raw material was chlorinated and subject to refining with distillation of 10 or more stages, then further subject to sodium reduction.

Next, the obtained hafnium was used as the raw material, and further subject to two-stage melting via hearth melting and ingot melting with an electron beam to remove volatile elements, gas components and so on. As a result of the foregoing process, as shown in Table 3, realized was Zr: 500 wtppm, O: 100 wtppm, C: 100 wtppm, N: 20 wtppm, S: 10 wtppm, P: 10 wtppm, others: 30 wtppm.

Next, the hafnium thus obtained was subject to deoxidation at 1250° C., under argon pressure (4 atm) for 10 hours with molten salt of Ca and CaCl2. Reduction was realized where 0, C, N, S, P<10 wtppm, and other impurities were also reduced to 25 wtppm.

With the sputtering target obtained from this ingot, as with Example 1, a uniform high purity hafnium thin film can be formed on a substrate.

TABLE 3 wtppm O C N S P Zr Others Raw Material — 10000 5000 500 100 10000 10000 Ingot 100 100 20 10 10 500 30 Deoxidation <10 <10 <10 <10 <10 500 25

With respect to the foregoing Examples 1 to 3, results of measuring the residual resistance ratio are shown in Table 4. As a result, as shown in Table 4, the residual resistance ratio at the ingot stage in Examples 1, 2 and 3 is respectively 38, 22 and 45, but respectively increased after deoxidation at 200, 120 and 190. Like this, it is evident that hafnium having a high residual resistance ratio can be obtained from hafnium having ultra high purity.

TABLE 4 Hafnium Material Residual Resistance Ratio Example 1 Ingot 38 After Deoxidation 200 Example 2 Ingot 22 After Deoxidation 120 Example 3 Ingot 45 After Deoxidation 190 Comparative Ingot 5 Example 1

Comparative Example 1

The raw material shown in Table 2 was subject to plasma arc melting to manufacture an ingot. The impurity content of the ingot was O: 7,000 wtppm, C: 1,800 wtppm, S: 100 wtppm, P: 50 wtppm, Zr: 20,000 wtppm, others: 1,600 wtppm. The residual resistance ratio of this ingot is similarly shown in Table 4.

As clear from Table 4, since the impurity content is high, the residual resistance ratio was low at 5.

INDUSTRIAL APPLICABILITY

Since the present invention is able to stably manufacture high purity hafnium in which gas components such as oxygen and other impurity elements are reduced by using a hafnium sponge with reduced zirconium as the raw material and subjecting this hafnium sponge to electron beam melting and deoxidation processing with molten salt, such high purity hafnium can be used as a heat-resistant or corrosion-resistant material, or an electronic material or optical material.

Claims

1. High purity hafnium and a target and thin film formed from said high purity hafnium having a purity of 4N or higher excluding zirconium and gas components, and an oxygen content of 40 wtppm or less.

2. High purity hafnium and a target and thin film formed from said high purity hafnium having a purity of 4N or higher excluding zirconium and gas components, and in which the content of sulfur and phosphorus is respectively 10 wtppm or less.

3. High purity hafnium and a target and thin film formed from said high purity hafnium according to claim 1 having a purity of 4N or higher excluding zirconium and gas components, and in which the content of sulfur and phosphorus is respectively 10 wtppm or less.

4. (canceled)

5. A manufacturing method of high purity hafnium wherein a hafnium sponge raw material is subject to solvent extraction and thereafter dissolved, and the obtained hafnium ingot is further subject to deoxidation with molten salt.

6. A manufacturing method of high purity hafnium according to claim 5 wherein, after performing deoxidation with molten salt, electron beam melting is further performed.

Patent History
Publication number: 20060266158
Type: Application
Filed: Oct 25, 2004
Publication Date: Nov 30, 2006
Applicant: Nikko Materials Co., Ltd. (Tokyo)
Inventor: Yuichiro Shindo (Ibaraki)
Application Number: 10/595,660
Classifications
Current U.S. Class: 75/612.000; 420/422.000
International Classification: C22C 27/00 (20060101);