12.16 Final.2025

Abstract
Electron-beam (EB) evaporation systems are useful in forming thin metal films for the production of compound semiconductor devices. The formation of metal ballistic nodules during evaporation is a major concern because it degrades the production yield of wafers. These nodules are caused by high-melting-point materials and gaseous components in the evaporation source materials. In the production of Ag slugs for evaporation, these impurities are easily introduced during the casting of Ag ingots. To minimize the impurities, we propose implementing a new impurity removal process during casting and a new degassing process after cutting. The use of Ag slugs fabricated using these improved processes drastically reduces the number of particles on the wafer. Furthermore, by removing the impurities in the Ag slug, the amount of floating objects during evaporation, which inhibits evaporation, is reduced compared to using conventional Ag slugs. In addition, the use of low-contamination Ag slugs results in low EB emission during evaporation. These results indicate that low- impurity Ag slugs could be very effective not only for the deposition of uniform Ag thin films, but also for evaporation operations under more environmentally friendly conditions via EB evaporation in compound semiconductor devices and other applications.