METHOD OF PRODUCING HIGH-PURITY ERBIUM

A method of purifying erbium is provided to produce a 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. Erbium has a high vapor pressure and is difficult to refine in a molten state. The method provides technology for efficiently and stably providing high-purity erbium, a sputtering target made of high-purity erbium, and a metal gate film having high-purity erbium as a main component thereof.