Measurement and modeling of voltage and plasma distribution of VHF-driven capacitively-coupled ladder-shaped electrode
Abstract
Voltage and plasma density distributions along electrode-rods of ladder-shaped electrodes were measured and theoretical models were proposed. Measurements were performed in test chambers, which were transparent for plasma emission observation and had probing points for voltage distribution measurements. Argon or nitrogen gas at 100 mTorr is used and the rod diameter and the rod to earth electrode spacing were 6 mm and 29 mm, respectively. The length of the rod was 1 m in the case of 1D, and the size of the electrode was 50 x 40 cm and the rod-to-rod spacing was 26 mm in the case of 2D. Measured ion saturation current distributions, which were coincident with the appearance of the plasma emission, was almost proportional to the voltage distribution. The proportional ratio of the current and the voltage increases with excitation frequency. Theoretical models of lossy transmission-line (for 1D) or transmission-network (for 2D) which consist of electrode's skin resistance and inductance, sheath capacitance and plasma impedance showed very good agreement with the measurements. Standing wave was a dominant cause of the distribution in 60-150 MHz range while a voltage drop dominated in over 150 MHz in the case of rod length of 1 m. Wavelength of the propagation wave in this case was about half of that in free space.
- Publication:
-
APS Annual Gaseous Electronics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..GECGTP063S