High purity iron, method of manufacturing thereof, and high purity iron targets

Abstract

High purity iron with a very few content of impurities such as copper, a method of manufacturing thereof, and high purity iron targets are provided. The iron containing impurities such as copper is dissolved in a hydrochloric acid solution, and the concentration of the hydrochloric acid of the aqueous solution of iron chloride is adjusted to 0.1 kmol / m<3 >to 6 kmol / m<3>. Then, iron is added in the aqueous solution of iron chloride, and an inert gas is injected into the solution with agitating, in order to convert the trivalent iron ions and divalent copper ions contained in the aqueous solution of iron chloride respectively to divalent iron ions and monovalent copper ions. Then, the aqueous solution of iron chloride is fed into a column filled up with the anion exchange resins. The divalent iron ions are not absorbed on the anion exchange resins although the monovalent copper ions are absorbed on the anion exchange resins. Therefore, copper can be separated from the aqueous solution of iron chloride. And then, the aqueous solution of iron chloride is evaporated to dryness, oxidized and heated in a hydrogen atmosphere to generate iron.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to high purity iron in which contents of impurities such as copper are reduced, a method of manufacturing thereof, and high purity iron targets.[0003] 2. Description of the Related Art[0004] Semiconductor devices such as VLSI (very large scale integrated circuit) and ULSI (ultra LSI) have a structure where various thin metal films are deposited on, for example, a silicon (Si) wafer. Although the idea of using iron (Fe) as a material of magnetic random access memory (MRAM) has been considered in recent years, the accompanying injurious impurities in the iron may result in malfunction or deterioration of the semiconductor device, which is undesirable. For example, copper (Cu) may cause a short circuit because of high diffusion rate inside silicon, and radioactive elements such as uranium (U) and thorium (Th) will cause incorrect operations, and alkaline metals and alkaline-earth metals may cause degradation of the de...

AI Technical Summary

Benefits of technology

[0010] It is another object of the invention to provide a method of easily and surely manufacturing high purity iron.

[0018] The method of manufacturing the high purity iron according to the invention includes the steps of converting trivalent iron ions and divalent copper ions respectively to divalent iron ions and monovalent copper ions, and adjusting a concentration of hydrochloric acid. These steps allow monovalent copper ions to be absorbed on the anion exchange resins, and divalent iron ions not to be absorbed thereon. Thus the copper can be separated easily and surely from the aqueous solution of iron chloride.

[0019] Another method of manufacturing high purity iron according to the invention includes the steps of converting trivalent iron ions in an aqueous solution of iron chloride to divalent iron ions and adjusting a concentration of hydrochloric acid. These steps allow at least one of impurities selected from the group consisting of zinc, gallium, niobium, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, and bismuth to be absorbed on the anion exchange resins, and divalent iron ions not to be absorbed thereon. Thus the impurities can be separated easily and surely from the aqueous solution of iron chloride.

Problems solved by technology

Although the idea of using iron (Fe) as a material of magnetic random access memory (MRAM) has been considered in recent years, the accompanying injurious impurities in the iron may result in malfunction or deterioration of the semiconductor device, which is undesirable.

For example, copper (Cu) may cause a short circuit because of high diffusion rate inside silicon, and radioactive elements such as uranium (U) and thorium (Th) will cause incorrect operations, and alkaline metals and alkaline-earth metals may cause degradation of the device properties.

Small amounts of impurities form impurity level that causes degradation of the semiconductor properties.

However, there is a problem with the solvent extraction.

It is difficult to control extraction and reverse extraction and to refine iron surely in industrial processes.

And, although nearly all of metal impurities can be separated by the ion exchange, copper contents before and after refining by the ion exchange may not change, that is, it is difficult to remove copper, which is a problem with the ion exchange.

In addition, there are problems with the electrolytic refining that pH control of electrolytic solutions is required, and it is difficult to remove nickel and copper.

However, it is difficult to apply the floating zone melting refining method to large scale and the method may not always produce high purity metals surely, that is, it is difficult to produce a large amount of high purity iron at a low price with the floating zone melting refining method.

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