Validated Sheath Model for Radio-Frequency-Biased, High-Density Plasmas

Published

October 16, 2008

Author(s)

Mark Sobolewski

Abstract

A model is proposed for sheaths in high-density plasma discharges, with radio-frequency bias applied at frequencies (omega) comparable to (omega sub i), the ion plasma frequency at the edge of the sheath. The model treats ion dynamics using fluid equations, including all time dependent terms. Current waveforms and sheath impedances predicted by the model were compared to measurements performed in high-density discharges in argon at 1.33 Pa (10 mTorr) at rf frequencies from 0.1 to 10 MHz (omega/omega (sub i) from 0.013 to 1.3) and rf bias voltages from 1 V to 200 V. All model input parameters were measured - no fitting or adjustable parameters were used. Model predictions were in good agreement with measurements, much better than that obtained by models which neglect time-dependent ion dynamics. The model explains why methods of extracting plasma parameters from electrical measurements using previous sheath models may fail, and it suggests new, more accurate methods of extracting these parameters.

Citation

Applied Physics Letters

Pub Type

Journals

Keywords

current, discharge, electrical, impedance, model, plasma, radio-frequency, sheath, voltage

Citation

Sobolewski, M. (2008), Validated Sheath Model for Radio-Frequency-Biased, High-Density Plasmas, Applied Physics Letters (Accessed April 25, 2024)