Theoretical Studies Of Plasma Ion Implantation

The plasma ion implantation relies on the ion acceleration in the sheath region to a high energy (10-50 keV), alleviating the cumbersome system of a conventional ion implantor. The dynamic evolution of the sheath characteristics is highly nonlinear especially when the negative high voltage at the target material is modulated at a finite frequency to contain the sheath expansion to a manageable size. Our approach uses a kinetic PIC (particle-in-cell) simulation method for a bounded plasma system allowing an external circuit as in the laboratory experiments. It predicts the kinetic properties which are inaccesible with fluid approach. The applied voltage magnitude and frequency depend on the application area, tool hardening or electronic material processing. By using a rather modest computing facility (PC-80386 or VAX-8800), we calculate the average and peak currents together with the sheath size and the implanted ion energy distribution. These results compare well with other analytic and fluid calculations; they will be the subject of the comparison with experiments as the latter results become available.