Energy contamination control in multiple charged ion implantations

A technique for measuring and monitoring charge exchange reactions prior to implantation of multiple charged ion beams on an E500 medium current implanter is discussed. There is a clear relationship between the energy contamination level measured in-situ before implantation and SIMS (secondary ion mass spectrometry) and thermawave measurements afterwards. This electrical technique establishes the process control capabilities needed for high-energy implantations, giving the user predictable and repeatable high-energy implants, with acceptable results for beam energy purity, uniformity, and dosimetry. It gives a process control capability for multiple charged implantations that was previously unavailable. Vacuum system pressure interlocks that are sometimes used are not reliable, since the vacuum gauges that are used to measure system pressure are not very sensitive to hydrogen or to important residual gas in ion implanter systems. Vacuum gauges also give only an indirect control of the energy contamination process