1 Instabilities in Inductive Discharges SFR Workshop November

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. 12/14/2021

2 TCP Experiment Inductive Coil PMT Plasma Video Langmuir Probe End-On View of 5. 4 m. Torr SF 6 Discharge Capacitive 450 W 12/14/2021 Unstable 595 W Inductive 900 W

3 Range of Instability in SF 6 Discharge Instability 12/14/2021

4 Fluctuation of Light Emission vs. Power SF 6 90 m. Torr 80 m. Torr 65 m. Torr 50 m. Torr 40 m. Torr 25 m. Torr 10 m. Torr 12/14/2021

5 35 30 P=650 W 25 20 15 10 5 5 10 15 Pressure, m. Torr 12/14/2021 20 Frequency of light signal, k. Hz Fluctuation of Light Emission vs. SF 6 Pressure 90 80 P=760 W 70 60 50 P=650 W 40 30 20 10 20 40 60 80 Pressure, m. Torr 100

6 Langmuir probe current time history PROBE CURRENT, A p. SF 6 = 5. 2 m. Torr, 500 W -300 14 - 460 10 - 620 0 6 0. 2 ms - 15 29 - 30 25 - 45 V=0 0 V=14 V 0 0. 2 ms 21 -1 44 -9 40 - 17 12/14/2021 V=28 V V=10 V 0 TIME 0. 2 ms 36 0. 2 ms V=-14 V 0 0. 2 ms V=-28 V 0 TIME 0. 2 ms

7 Theoretical Model of Instability 12/14/2021

8 Theoretical Model of Instability p. SF 6 = 5 m. Torr, ICOIL =8. 2 A ne 0. 4 1 10 0 20 10 Te 0 10 n- n- 0 5 dne/dt=0 F 0 0 0. 4 optical emission G- dn-/dt=0 -1 10 -4 10 0 1 12/14/2021 2 3 4 5 t, ms 6 7 8 9 10 -2 10 0 10 ne (1010 cm-3)

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. 12/14/2021