Boron beam performance and in-situ cleaning of the ClusterIon® source

The implantation of borohydride ions has enabled very high dose rates at low implantation energies. Using the borohydride material B18H22, an on-wafer equivalent current of 18 mA at 1 keV are readily achieved using a ClusterIon (R) source on a conventional high current implanter. As is frequently the case when running condensables, when borohydrides are introduced into the source in the vapor phase, boron-containing deposits tend to condense and accumulate in and around the ion source over extended periods of operation. In order to achieve production-worthy source lifetimes, we have developed a means of controlling the temperature of those surfaces exposed to the vapor to reduce condensation, and an in-situ cleaning process to efficiently remove deposits from the system. We show beam recovery after periodic cleaning cycles which enable good beam stability and performance. The in-situ cleaning process is also beneficial in reducing potential exposure to toxic fumes during source removal.