Numerical modelling of the plasma source ion implantation process in 2D

摘要

Plasma immersion ion implantation (PII) has been developed for material modification by ion implantation to aviod the line-of-sight restrictions of beam-line ion implantation. In PII the target is immersed in a weakly ionised plasma and biased with a high negative voltage. In the time scale of the inverse electron plasma frequency, #omega# _(pe)~(-1), electrons near the surface are repelled due to their negative charge, leaving behind an uniform ion sheath. In the time scale of the inverse ion plasma frequency, #omega# _(pi)~(-1), the positive charged ions are accelerated through the sheath towards the target from all sides and are implanted. Consequently the ion density in the sheath drops causing the sheath-plasma edge to recede and uncover enough ions to shield the target potential. As a result the sheath expands.