Broad-beam ion sources: Present status and future directions

Abstract

Operational problems are believed to constitute the major obstacle to the more widespread use of broad-beam ion sources, particularly in production applications. In the category of problems that are primarily the responsibility of ion-source operators: an excessive discharge voltage is undesirable because it causes excessive damage depth and contamination at the target; an excessive ion-beam current is undesirable because it leads to rapid wear of the accelerator grid, increased target contamination, and little or no increase in process rate; and an electron backstreaming condition is undesirable because false indications of ion-beam current are given by the power supply. In the category of problems that are primarily the responsibility of ion-source manufacturers: the need for excessive maintenance has an obvious and direct impact on cost; the lack of reproducibility of both ion-beam profile and direction results in an overall lack of reliability that has required an excessive degree of care by highly skilled operators; and the lack of adequate information from the manufacturer is a problem that, in turn, aggravates all other problems. From examination of ion sources and industrial applications of these sources, most ion sources are misused, as well as being unsuited for production applications. There is an obvious need for improved education of ion-source operators and improved ion-source design.