| 简介 |
PROBLEM TO BE SOLVED : To obtain high-purity lanthanum having a purity of 4 N or more.
SOLUTION : In a method for producing high-purity lanthanum having a purity of 4 N or more, lanthanum fluoride, as a raw material, which has a purity of 4 N or more excluding rare earth elements other than lanthanum and gas components, is reduced with distilled calcium so as to produce lanthanum having a purity of 4 N or more, and the reduced lanthanum is subjected to electron beam melting to remove volatile substances so as to exclude rare earth elements other than lanthanum and gas components. In the method for producing high-purity lanthanum, Al, Fe, and Cu are respectively made to be included in the amount of 10 wt.ppm or less, the rare earth elements other than lanthanum are made to be included in the total amount of 10 wt.ppm or less, and C is made to be included in the amount of 200 wt.ppm or less. In the method for producing high-purity lanthanum, the total content of gas components is made to be 1, 000 wt.ppm or less. In a technique, high-purity lanthanum, a sputtering target composed of the high-purity lanthanum, and a thin film for metal gate which includes the high-purity lanthanum as a main component are efficiently and stably provided.
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