Abstract
We have investigated the electrostatic charging effects of dielectric substrate materials during plasma immersion ion implantation. The results demonstrate that the time-dependent surface potential (negative) may be reduced in magnitude due to the charging effect of the dielectric surface, leading in turn to a reduction in the energy of the incident ions and a broadening of the implanted ion energy spectrum. The charging effect is greater during the plasma immersion bias pulse rise-time, and the electrostatic potential charging may be as large as 75% of the total applied (pulse) potential. This is due to abundant charge movement both of ions and secondary electrons, and has been confirmed by computer simulation. The plasma sheath capacitance has a small influence on the surface potential, via the bias pulse rise-time. Processing parameters, for example voltage, pulse duration, plasma density, and pulse rise-time, have a critical influence on the charging effects. Short pulse duration, high pulse frequency and low plasma density are beneficial from the viewpoint of maximizing the implantation ion energy.
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