Ion energy and angular distributions into the wafer-focus ring gap in capacitively coupled discharges

The termination of the edge of wafers in reactive ion etching reactors is important for obtaining uniform fluxes of reactants across the substrate. Structures such as focus rings (FRs) are often used to improve the uniformity of fluxes. There is a gap of hundreds of micrometres to a few mm between the edge of the wafer and the FR for mechanical clearance. Plasma penetration into the gap can produce particle forming films and erosion of consumable parts. In this paper, we discuss results from a computational investigation of ion energy and angular distributions incident into the wafer-focus ring gap. The geometry and electrical properties of the FR can skew the angle and limit the extent of energies of ions penetrating into the gap.