Microwave ion sources for material processing (invited)

Abstract

Microwave ion sources were developed and used for material processing in industrial manufacture. Major applications of them were concentrated on semiconductor device fabrication, especially on modifying electrical properties of semiconductor material by ion implantation, as well as on processing submicron structures of semiconductor devices by so-called plasma etching. Most ion implanters for manufacturing silicon on insulator wafers exclusively adopt microwave ion sources because the sources work very stably for oxygen ions. Recently, the application of ion beams is extending to nonsemiconductor fields. Thus, ions are applied to surface modification of nonsemiconductor materials and to thin-film formation by ion beam deposition which is carried out with low energy of several tens of eV. The characteristics of films are very dependent on the beam energy values which are strictly determined by sum of the source bias voltage and the plasma potential with respect to the chamber. Microwave ion sources are very suitable to such applications of low-energy ion beams because the ions extracted from them have a very small energy dispersion. In this article, the features of microwave ion sources are specified and a variety of the sources are reviewed with respect to their applications.