長寿命・大電流プラズマ陰極形イオン源の開発

概要

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A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma cathode is convergent, i.e. filament-like; in zero magnetic field, it turns divergent and spray-like. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF_5 or PF_5,the lifetime of this ion source was found to be more than 90 hours with an extraction voltage of 40kV and the corresponding ion current density 20mA/cm^2. Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As^+ and P^+ ions from AsF_5 and PF_5,and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is eminently suitable for use in oxygen ion production.
東海大学の論文