Decreasing high ion energy during transition in pulsed inductively coupled plasmas

Pulsed RF plasmas sustained in electronegative gas mixtures are increasingly being employed for plasma etching at future technological nodes. During the plasma transition from the afterglow to the active-glow, ion energies at the wafer can substantially increase due to the high voltage required to deposit bias power into few electrons. These high energy ions, albeit few, increase the possibility of ion bombardment damage and are, therefore, detrimental to the etching process. Strategies to decrease the high ion energies during transition are investigated using a two-dimensional computational plasma model. Results for poly-Si etch in an Ar/Cl-2 gas mixture indicate that the high ion energies can be reduced by offsetting the bias pulse from the source pulse with minimal impact on the etch depth rates. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3679075]