The ion kinetics at the wafer edge by the variation of geometry and permittivity of the focus ring in capacitively coupled discharges

Abstract

The change of the ion transport is investigated with the variation of the focus ring property at the wafer edge of a capacitively coupled plasma under an intermediate pressure of a few Torr. The particle fluxes and the ion trajectories at different locations are investigated with the variations of the gap size between the wafer edge and the focus ring, the focus ring height, and the permittivity of the focus ring. The incident angle and the particle fluxes to the wafer edge increase with the gap size. Conversely, the particle fluxes to the wafer edge decrease with the increase in the focus ring height. The incident angle of ions still keeps normal to the surface at the wafer edge, but on the left side of the focus ring, it increases dramatically with the increase in the focus ring height. With the change of the permittivity of the focus ring, it is possible to control the ratio of the ion flux to the neutral flux on the focus ring surface by enhancing only the ion flux independently.