Purity of high energy beams in R.F. linear accelerator based implanters

Nearly monoenergetic beams of ions in the MeV range are critical in many implants for semiconductor fabrication. In this study, possible contamination scenarios leading to beam components significantly different in energy from the intended beam are examined in the context of R.F. linear accelerators. Experiments have been performed to artificially create conditions which might lead to energy contamination from beam components injected into the linear accelerator. The susceptibility of the system to transport a contaminated beam was measured by observing beam currents in a faraday near the wafer. Mass isotopes, such as /sup 10/B, are deliberately injected instead of /sup 11/B. Dimer effects are evaluated for phosphorous. In these and additional cases, it is found that the three major beam purity assurance systems of the NV-GSD/HE implanter, the mass, velocity, and energy filters, provide excellent energy purity.