1 Instabilities in Electronegative Inductive Discharges SFR Workshop
1 Instabilities in Electronegative Inductive Discharges SFR Workshop November 8, 2000 A. M. Marakhtanov, M. A. Lieberman, A. J. Lichtenberg, and P. Chabert Berkeley, CA 2001 GOAL: characterize instability using OES/actinometry and planar probe. Install the Z-scan sensor and explore the spectral RF signature of plasma instability by 9/30/2001. 11/8/00
Experimental TCP Setup Planar Probe 30 cm Monochromator Inductive Coil Plasma 19 cm OES (PMT) Langmuir Probe Mass Spectrometer
3 Instability windows Inductive Capacitive • Unstable in most of discharge conditions used in etching • Instability linked to average attachment rate 11/8/00
4 Frequency vs. Power and Pressure 90 m. Torr 80 m. Torr SF 6 65 m. Torr 50 m. Torr 40 m. Torr 25 m. Torr 10 m. Torr • Instability frequency increases with increase of pressure and power 11/8/00
5 Effect of Matching Network SETTING 1 (LOW FREQ. ) SETTING 2 (HIGH FREQ. ) Ar / SF 6 (1: 1) p = 5 m. Torr Prf = 500 W f 1 = 1. 0 k. Hz f 2 = 8. 5 k. Hz • In Ar/SF 6 discharges the frequency depends on the settings of the matching network 11/8/00
6 Determination of time varying densities from planar and cylindrical probes currents time (ms) The negative ion fraction a can be deduced from the saturation current ratio: , where 11/8/00 Ar / SF 6 (1: 1) p = 5 m. Torr Prf = 550 W f = 0. 8 k. Hz
7 Results in (1: 1) Ar/SF 6 discharge Ar / SF 6 (1: 1) p = 5 m. Torr Prf = 500 W f = 0. 8 k. Hz • The electron density changes by a factor of 20 with fast rise and decay times • Positive and negative ion densities decay at the same rate 11/8/00
8 Results in pure SF 6 discharge 5 SF 6 p = 5 m. Torr Prf = 500 W f = 12. 9 k. Hz 400 • The electron density exhibit sharp peaks; the ion density is slightly modulated • The discharge spends a long time in low-density regime with 400 11/8/00
9 2002 and 2003 Goals Characterize plasma instability using V-I-phase probe. Develop model for reduced electron temperature and density, by 9/30/2002. Develop and test instability control. Reduce electron temperature and density in discharges, by 9/30/2003. 11/8/00
- Slides: 9