HIGH-PURITY YTTRIUM, PROCESS OF PRODUCING HIGH-PURITY YTTRIUM, HIGH-PURITY YTTRIUM SPUTTERING TARGET, METAL GATE FILM DEPOSITED WITH HIGH-PURITY YTTRIUM SPUTTERING TARGET, AND SEMICONDUCTOR ELEMENT AND DEVICE EQUIPPED WITH THE METAL GATE FILM

摘要

Provided are high-purity yttrium and a high-purity yttrium sputtering targeteachhaving a purity, excluding rare earth elements and gas components, of 5 N ormoreand containing 1 wt ppm or less of each of Al, Fe, and Cu; a method ofproducinghigh-purity yttrium by molten salt electrolysis of a raw material being acrude yttriumoxide having a purity, excluding gas components, of 4N or less at a bathtemperatureof 500°C to 800°C to obtain yttrium crystals, desaltingtreatment, water washing, anddrying of the yttrium crystals, and then electron beam melting for removingvolatilematerials to achieve a purity, excluding rare earth elements and gascomponents, of5N or more; and a technology capable of efficiently and stably providing high-purityyttrium, a sputtering target composed of the high-purity yttrium, and a metal-gate thinfilm mainly composed of the high-purity yttrium.