Effect of pulse waveform on plasma sheath expansion in plasma-based ion implantation

In this paper, the effect of the pulse waveform on plasma sheath evolution around a diamond-shaped target has been simulated using fluid dynamic model in the context of plasma-based ion implantation (PBII). The implanted para meters of ions such as ion-implanted energy, impact angle and impact curren t have also been studied under different pulse shapes. Understandably, the longer pulse rise time would result in the lower ion impact energy, and les s sheath expanding extent. By comparing the sheath structure under differen t pulse rise time, we found that long pulse rise time would enhance the con formation of the sheath to the target at the earlier stage of the pulse and would reduce the tendency of the ion depletion in the plasma sheath. Accor dingly increase the ion impact current at the later stage of the pulse, whi ch is quite important for the PBII process, when the ions have been acceler ated adequately. (C) 2000 Elsevier Science B.V. All rights reserved.