Positive pulse bias method in plasma-based ion implantation

A novel scheme of the plasma-based ion implantation (PBII), the positive pulse bias (PPB) method has been proposed, in which a workpiece to be treated is at the ground potential while the plasma surrounding it is biased to a positive high voltage; thus the ion sheath same as the one in the conventional negative pulse bias (NPB) method is formed on the workpiece. Principal merit of the PPB method over the NPB method is that it possesses a mechanism of suppressing X-rays from the wall by impact of secondary electrons and it enables to manipulate the workpiece during PBII processing. The latter merit will serve to realize an efficient continuous processing system. The principle of the PPB method is discussed based on the asymmetric double probe theory and results of the proof-of-principle experiment are presented.