Ion Energy Distribution Function of Triple Frequency Capacitive
Discharges
 
A. Wu (UCB-NE)
 
  In many capacitive discharges for plasma processing applications, a
dual frequency drive is used to control the ion energy distribution
and the ion flux.  The high frequency is used to control the ion
flux, and the low frequency is used to control the ion distribution. 
It is then desired to increase the controllability of the ion energy
distribution by adding a third frequency, so that the high frequency
is used to control the ion flux, and the two lower frequencies are
used to control the width and the mean of the distribution.
 
  Using XPDP1, a one-dimensional particle-in-cell program, sets of
three frequencies are simulated at different driving voltages and the
results are presented.  The simulations are advantageous because they
can model the electrons colliding, but turn off the ion collisions,
allowing the ions to behave as if there were no charge exchange
collisions.  The results show that it is possible to control the mean
and the width of the distribution by applying different voltages. 
However, there is not a perfect decoupling of the voltages.