Ion beam technologies, in particular ion implantation, have had a profound effect on the development of Si integrated circuits. We review the pertinent history of ion source and machine development within the constraints of Moore's law. For ion sources, the critical roles of hot cathode and rf sources are discussed. Novel applications such as sources for finely focused beams for lithography and cluster beams for doping ͑decaborane͒ or smoothing ͑Ar͒ will be discussed. Future trends in terms of the next generation of devices and the required implantation machines will be reviewed.

We present secondary electron yield and plasma enhancement factor data for silicon surfaces exposed to Ar, He, N2, O2, H2, and BF3 plasmas, for incident ion energies from 0.5–10 keV. A fiber-optic isolated Faraday cup was used to directly measure the ion current Jion, allowing a direct measurement of the secondary electron yield. This method automatically accounted for the effect of pulse-induced plasma density enhancement due to the ionization of neutral gas by accelerated secondary electrons, which we observed and measured quantitatively. The values of the secondary electron yields measured by this method were higher than published values measured by the conventional (ultraclean surface and ultrahigh vacuum) methods but lower than published values measured by previous plasma immersion ion implantation methods.

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