SHEATH DYNAMICS IN PLASMA IMMERSION ION-IMPLANTATION

Plasma immersion ion implantation is a new method to implant ions into materials for modifying surface properties. The samples are immersed into a plasma and high voltage is applied to the sample. Ions are extr acted from the plasma and accelerated directly to the sample. Critical parameters for the development of this implantation process are the i on implantation current and the sheath expansion characteristics. To m odel the ion dynamics of this process, we used the two-fluid model of the plasma and the Bohm sheath criterion. To verify the predictions of the model, the sheath and the presheath expansion were measured using a Langmuir probe, and the ion fluence reaching the sample surface was determined by Rutherford backscattering spectroscopy. The calculated sheath expansion and current densities are in good agreement with the experimental data.