Study of Refining and Purification Processing of Gallium Metal As a Raw Materials for Compound Semiconductor

Abstract

Gallium is used in III-V compound semiconductors according to the development of the semiconductor industry, and increasingly requires high purity gallium metal, and the amount of use is also increasing. The rare earth metal, gallium, has low reserves, which makes it difficult to supply raw materials. Therefore, process waste containing gallium is used to secure raw materials. In this study, high-purity gallium metal was fabricated from process wastes by electrolytic refining and Czochralski(CZ). The CZ device was operated in a clean room of 400 class or less for a high purity environment, and the source crucible was controlled with oxidation of metal using sodium hydroxide and mineral oil. Gallium has a low melting point of 303 K, so the seed portion was cooled to 260 K to make an ingot. The impurity elements in the highly purified gallium metal of about 8N grade was quantitatively analyzed using a glow discharge mass spectrometer(GD-MS). In quantitative analysis using GD-MS, relative sensitivity factors(RSF) are used. For RSF of each element, a standard sample containing gallium as an impurity in an aluminum matrix was used. By analyzing the aluminum matrix CRM, quantitative analysis is possible for a total of 17 elements: Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ag, Cd, Sn, Pb, Bi, etc. Lastly, in the analysis of gallium crystallized using the CZ method, four of impurity elements were detected: Al, Si, Cr, and Fe, and all other elements were below the detection limit. In the quantitative analysis of impurities in the gallium metal, the total impurity element was 5.58 ppbw, and the final purity of gallium was about 99.9999994% (8N).