1. Instabilities in Inductive Discharges
SFR Workshop
November 8, 1999
A. M. Marakhtanov, M. A. Lieberman, and
A. J. Lichtenberg
Berkeley, CA
This work aims to investigate unstable behavior of plasma in inductive discharges with attaching gases.
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2. End-On View of 5.4 mTorr SF6 Discharge
TCP Experiment
PMT
Plasma
Inductive
Coil
Video
Langmuir Probe
End-On View of 5.4 mTorr SF6 Discharge
Capacitive
450 W
Unstable
595 W
Inductive
900 W
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3. Range of Instability in SF6 Discharge
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4. Fluctuation of Light Emission vs. Power
90 mTorr
SF6
80 mTorr
65 mTorr
50 mTorr
40 mTorr
25 mTorr
10 mTorr
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5. Fluctuation of Light Emission vs. SF6 Pressure35 90 80
P=760 W 30
P=650 W 70 25 60
Frequency of light signal, kHz
Frequency of light signal, kHz 20 50
P=650 W 40 15 30 10 20 5 10 5 10 15 20 20 40 60 80
100
Pressure, mTorr
Pressure, mTorr
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6. Langmuir probe current time history
pSF6 = 5.2 mTorr, 500 W
-300 14
- 460 10
V=0
V=28 V
- 620 6
0.2 ms
0.2 ms
- 15 29
PROBE CURRENT, A
- 30 25
V=14 V
V=-14 V
- 45 21
0.2 ms
0.2 ms
- 1 44
- 9 40
V=10 V
V=-28 V
- 17 36
TIME
0.2 ms
TIME
0.2 ms
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7. Theoretical Model of Instability
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8. Theoretical Model of Instability
pSF6 = 5 mTorr, ICOIL =8.2 A
0.4 n e 1 10 5
dne/dt=0 n - - n 10 e T 10 20 F
dn-/dt=0
0.4 G - -1 10 1 -4 -2 10 10 10
optical
emission n
(1010 cm-3) 1 2 3 4 5 6 7 8 9 10 e
t,ms
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9. Progress vs Milestones
Year 1
Mapping of inductive plasma instability regions inside TCP source. (Done)
Observation of optical emission modulations due to instabilities. (Done)
Develop theoretical model of instabilities (Done); to appear in Applied Physics Letters (December 1999).
Year 2
Add additional TCP plasma diagnostics. (Done)
Further develop theory for electronegative instabilities in inductive discharges. (Done)
Bring high flow Lam oxide etch prototype on-line. (In progress)
Future Work
Continue work on the TCP, characterizing the influence of the matching network and power supply on the instabilities. Incorporate these effects into our global model of instability.
Initiate instability studies on a Lam high flow oxide etch prototype TCP reactor.
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