Ion transit through capacitively coupled Ar sheaths: Ion current and energy distribution

Abstract

The ion current and ion energy distribution (IED) of Ar+ and ArH+ impinging on a grounded surface immersed in capacitively coupled Ar plasmas have been measured as a function of pressure, applied rf voltage amplitude (Vrf), interelectrode gap, and sampling orifice size. A maximum in ion current occurs at high Vrf and intermediate electrode spacing. rf modulation of the collisionless IED occurs at high pressure and high Vrf and is caused by reduction of the sheath dimension under these conditions. Collisional shift to lower ion energy is also noted at high pressure. A low-energy peak at ∼10 eV is observed under high pressure and ion current conditions. Larger orifice sizes increase the collisions occurring downstream from the orifice as indicated by collisional energy shifts in the IED and a decrease in ion current density.