Positive pulse bias method for a high-throughput PBII processing system

The positive pulse bias (PPB) method has been proposed as a new scheme of the plasma-based ion implantation. In this method, the plasma is biased to a positive high potential with respect to a target (a workpiece) at ground potential. While it offers new benefits coming from the grounded target, such as possible handling of the target during PBII processing and in situ process monitoring, it needs special considerations to meet the PPB conditions and to minimize an extra power loss at the chamber as well. Characteristic features of the PPB method: Its arrangement, potential and current distributions and the necessary condition for the ion sheath formation are first discussed in contrast to the usual negative pulse bias (NPB) method. Next, results of the experiment are presented. They include the floating potential measurement in the plasma and the energy analysis of the ions incident upon the target. It is confirmed that the ion energy agrees well with the potential energy across the sheath and increases in proportion to the anode potential as expected from the principle of the PPB method.