Emittance considerations in ion source design and operation

In any ion beam system relevant to high current ion implantation, the ion source itself is the single most important component in that it determines the minimum emittance of the beam and hence the feasibility of obtaining a specified beam current, physical size and angular spread at the wafer position. The effects of emittance are fundamental and cannot be overcome by ion optical operations on the beam following extraction. The ion sources that have been developed for high current, production ion implanters are required to provide effective molecular cracking and, in some cases, high multiple charge state fractions. In the present work, the effect of achieving these properties on the beam quality has been studied for sources based on the widely used Bernas design.