Dual frequency discharge
A. Wu (UCB-NE) 
 
In a capacitive discharge used for semiconductor processing, the ion
energy distribution function (IEDF) is an important diagnostic for
seeing the effects of ions at the wafer.   The ability to predict the
IEDF is greatly desired.  Simulations have been done for different
frequencies and voltages.  The results are then presented in addition
to a model to pred ict the IEDF for any number of frequency drives,
as long as the voltage at the sheath is known.  Since ions are too
heavy to respond with typical high frequencies used in industry, it
is possible to filter the high frequencies using Fourier transforms
and low pass filters to create the voltage that the ions actually can
respond to.   The shape of the low pass filter is given by
Benoit-Cattin (1968).  Knowing the voltage that the ions actually
respond to, then it is possible to predict the IEDF from that. 
Details on the filter and the prediction require further refinements.