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Review of relaxation oscillations in plasma processing discharges
周筑文, M.A.Lieberman, SungjinKim
2007 (3):
758-765.
doi: 10.1088/1009-1963/16/3/033
摘要
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Relaxation oscillations due to plasma instabilities at frequencies
ranging from a few Hz to tens of kHz have been observed in various
types of plasma processing discharges. Relaxation oscillations have
been observed in electropositive capacitive discharges between a
powered anode and a metallic chamber whose periphery is grounded
through a slot with dielectric spacers. The oscillations of
time-varying optical emission from the main discharge chamber show,
for example, a high-frequency (\sim 40~kHz) relaxation
oscillation at 13.33Pa, with an absorbed power being nearly the
peripheral breakdown power, and a low-frequency ( \sim 3 Hz)
oscillation, with an even higher absorbed power. The high-frequency
oscillation is found to ignite plasma in the slot, but usually not in
the peripheral chamber. The kilohertz oscillations are modelled using
an electromagnetic model of the slot impedance, coupled to a circuit
analysis of the system including the matching network. The model
results are in general agreement with the experimental observations,
and indicate a variety of behaviours dependent on the matching
conditions. In low-pressure inductive discharges, oscillations appear
in the transition between low-density capacitively driven and
high-density inductively driven discharges when attaching gases such
as SF6 and Ar/SF6 mixtures are used. Oscillations of
charged particles, plasma potential, and light, at frequencies
ranging from a few Hz to tens of kHz, are seen for gas pressures
between 0.133 Pa and 13.33 Pa and discharge powers in a range of
75--1200 W. The region of instability increases as the plasma becomes
more electronegative, and the frequency of plasma oscillation
increases as the power, pressure, and gas flow rate increase. A
volume-averaged (global) model of the kilohertz instability has been
developed; the results obtained from the model agree well with the
experimental observations.
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