Two-dimensional particle-in-cell plasma source ion implantation of a prolate spheroid target

A two-dimensional particle-in-cell simulation is used tostudy the time-dependent evolution of the sheath surrounding aprolate spheroid target during a high voltage pulse in plasma sourceion implantation. Our study shows that the potential contour linespack more closely in the plasma sheath near the vertex of the majoraxis, i.e. where a thinner sheath is formed, and a non-uniform totalion dose distribution is incident along the surface of the prolatespheroid target due to the focusing of ions by the potentialstructure. Ion focusing takes place not only at the vertex of themajor axis, where dense potential contour lines exist, but also atthe vertex of the minor axis, where sparse contour lines exist. Thisresults in two peaks of the received ion dose, locating at thevertices of the major and minor axes of the prolate spheroid target,and an ion dose valley, staying always between the vertices, ratherthan at the vertex of the minor axis.