Simulation of sheath dynamics and current nonuniformity in plasma-immersion ion implantation of a patterned surface

We study the steady-state structure and the dynamics of a plasma sheath surrounding a patterned surface. A two-dimensional hybrid particle-in-cell code is employed where special attention is given to the plasma side boundaries. The surface consists of a periodic array of wide and narrow trenches. We characterize the conformity of the steady-state sheath and the uniformity of the ion currents to the wall as well as the sheath-expansion dynamics following sudden negative charging of the surface. We study the nonuniform motion of the sheath edge away from the surface, which leads to a planar high-voltage sheath. The inhomogeneous distributions of ion current and impact angle onto the walls are discussed.