Abstract
Abstract
The time-varying mechanism of the positive-ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma was investigated in detail using a quadrupole mass spectrometer equipped with an electrostatic energy analyzer. Time-resolved measurements of the ion composition with respect to the pulse-off period (
T
off
) revealed that the electron temperature (
T
e
) just after turning on the pulse is an important factor in determining the ratio of the ionization rates of the Ar+ and C
x
F
y
+ ions. The time-varying phenomenon of the ion composition was also investigated through a numerical analysis based on the particle balance model, considering the production and loss rates of ions, ion–ion recombination processes, and ion–molecule reactions. When the VHF power (
P
VHF
) was increased, a decrease in the ambipolar diffusion loss time constants of the ions (
τ
loss
i
) was observed, and the change in electronegativity was pointed out as the cause of this phenomenon.
Subject
General Physics and Astronomy,General Engineering