Magnetic field effect on the sheath in plasma immersion ion implantation

Summary form only given. Plasma immersion ion implantation (PIII) is a relatively new technology that is used to modify material surface properties. In a PIII process, a negatively biased target is placed in the plasma. The resulting electric field is concentrated in the target vicinity, in a sheath, a region where quasi-neutrality breaks down. This electric field accelerates ions to the high energy towards the target. High energy ions are implanted into the surface and modify the surface properties for a wide range of materials. Since the main ion acceleration is concentrated in the sheath, the sheath behavior is extremely important in PIII. It is clear that keeping the sheath thickness in the optimal range is an important problem. One of the ways to control the sheath thickness may be the use of a magnetic field. We present some preliminary results of experimental measurements of the sheath size using a filtered vacuum arc plasma source. The sheath thickness was measured using a positively biased movable cylindrical probe. When the probe was immersed in the plasma, it collected the electron saturation current and when the probe was immersed in the sheath, its current is practically zero because the sheath is depleted of electrons. By moving the probe from the target, it was possible to determine the sheath edge distance from the target when observing a sharp change in electron current collected by the probe.