High purity erbium, erbium sputtering target consisting of high purity, high purity and erbium met

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High-purity erbium having a purity of 5N or higher excluding rare earth elements and gas components, and containing Al, Fe, Cu, and Ta each in an amount of 1 wtppm or less, W in an amount of 10 wtppm or less, carbon in an amount of 150 wtppm or less, alkali metals and alkali earth metals each in an amount of 1 wtppm or less, other transition metal elements in a total amount of 10 wtppm or less, and U and Th as radioactive elements each in an amount of 10 wtppb or less. An object of this invention is to provide a method of highly purifying erbium, which has a high vapor pressure and is difficult to refine in a molten state, as well as technology for efficiently and stably providing high-purity erbium obtained with the foregoing method, a sputtering target made of high-purity erbium, and a metal gate film having high-purity erbium as a main component thereof.