Preparation method of target-grade ultrahigh-purity tantalum metal

Abstract

The invention provides a preparation method of target-grade ultrahigh-purity tantalum metal. In the method, a recrystallization process is added in tantalum wet-process metallurgy, thereby effectively reducing the contents of high-melting-point metal impurities and radioactive elements. The preparation method comprises: industrial K2TaF7 is put in a pure diluted HF solution, the concentration of crystalline HF is controlled, the temperature of crystalline HF is controlled to 80-90 DEG C, and potassium salt is excessive by 5-10%; after naturally cooling to 35-45 DEG C, cooling water is introduced to cool to room temperature; filtration is carried out while washing with a solution having PH 9 and absolute ethyl alcohol, thus high-melting-point metals, transition metals and impurities such as uranium, thorium, carbon, oxygen and the like are effectively removed; and then in tantalum pyrometallurgy, Si is effectively removed, and the pollution of Fe, Ni and Cr is prevented; and low-melting-point metals of less than 3000 DEG C are further removed in tantalum refining, thereby effectively reducing the contents of C, N and O. By using the preparation method provided by the invention, therefining frequency of an electron beam furnace is saved, and production cost is reduced.

Description

technical field [0001] The invention relates to a preparation method of ultra-high-purity tantalum metal, in particular to a preparation method of target-grade ultra-high-purity tantalum metal. Background technique [0002] Silicon oxide was used as the insulating film between electrodes in semiconductor devices. Large-scale integrated circuits appeared after the 1990s, requiring extremely thin insulating films and larger, more stable and reliable node constants. Therefore, the oxide film of tantalum replaced the silicon oxide film. Oxide film. The oxide film of tantalum is realized by the Ar-O sputtering method, so the tantalum target is required to have high purity, small grain size, good recrystallization texture and three axial consistency. [0003] The production of tantalum targets is completed by two majors: metallurgy and pressure processing. Obtaining high-purity tantalum metal by metallurgy includes three major processes: hydrometallurgy, pyrometallurgy and refin...

AI Technical Summary

Problems solved by technology

One is that the tantalum metal is not pure enough

Practice has proved that high alkali metals such as K and Na in tantalum will cause the movement of semiconductor insulating film and deteriorate the interface characteristics; high transition elements such as Fe, Cr, Ni, Mn, etc. will affect the operation of components; high radioactive impurities such as Th and U , the emitted rays have a fatal impact on the reliability of components; high refractory metals such as Nb, W, Mo, and Zr increase the leakage current of components; high gas impurities such as C and O affect the electrical properties of components

[0005] The second is the high cost of electron beam refining. In order to ensure the purity of tantalum metal, tantalum ingots are usually refined 2 to 3 times, or even more times, but high melting point metals such as Nb, W, Mo, and Zr cannot be removed.

[0006] There are three main reasons for the above problems: First, the composition of tantalum ore is complex, and the existing hydrometallurgical purification capacity is not enough

Usually, tantalum ore is associated with Ti, Zr, Li, RE, W, U, Th, Sn, Ca, Fe, Mn and other elements, and has similar crystal chemical properties, and is prone to equivalent and heterovalent isomorphism, so the mineral The composition is very complex; while using HF-H 2 SO 4 - Insufficient hydrometallurgical purification capacity of sec-octanol (MIBK)

Second, there is secondary pollution in the reduction, water washing and pickling processes of pyrometallurgy

Third, electron beam refining has no removal effect on high melting point metals

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