Angular characteristics of argon ion fluxes at the rf-powered electrode of a parallel-plate reactor

Abstract

In a parallel-plate 13.56 MHz rf reactor argon ions are created in a plasma and are accelerated by the electric field across the sheath where they are subject to charge-exchange collisions and elastic scattering. The time-dependent electric field and the sheath length are used as input for Monte Carlo simulations. Assuming initial trajectories for ions crossing the plasma sheath boundary deviating from being parallel to the sheath electric field, secondary maxima in the ion angular distributions are found. Experimental ion angular distributions are investigated by sampling ions through a 100 μm orifice. These ions are detected with a quadrupole mass spectrometer which is tilted with the vertex lying in the orifice. The experimental ion angular distributions are compared with the results of Monte Carlo simulations showing that experimental and simulated distributions are in fairly good correspondence.