METHOD FOR PRODUCING HIGH-PURITY LANTHANUM, HIGH-PURITY LANTHANUM, SPUTTERING TARGET FORMED FROM HIGH-PURITY LANTHANUM, AND METAL GATE FILM HAVING HIGH-PURITY LANTHANUM AS MAIN COMPONENT

摘要

The present invention addresses the problem of providing a technique capable of efficiently and stably providing a method for producing high-purity lanthanum, the method characterized in that: a crude lanthanum oxide starting material having a purity of 2N-5N, excluding gas components, is used; the material is subjected to molten salt electrolysis at a bath temperature of 450-700°C to produce lanthanum crystals; the lanthanum crystals are subsequently desalted: and electron beam melting is then performed to remove volatile substances. The present invention also addresses the problem of providing a technique capable of efficiently and stably providing high-purity lanthanum, high-purity lanthanum itself, a sputtering target formed from high-purity material lanthanum; and a thin film for metal gates that has high purity lanthanum as the main component.