Sheath model for radio-frequency-biased, high-density plasmas valid for all omega/omega(i)

A model is proposed for sheaths in high-density discharges, with radio-freq uency (rf) bias applied at frequencies omega comparable to omega (i), the i on plasma frequency at the edge of the sheath. The model treats ion dynamic s using fluid equations, including all time-dependent terms. Model predicti ons for current, impedance, and power were compared to measurements perform ed in high-density discharges in argon at 1.33 Pa (10 mTorr) at rf bias fre quencies from 0.1 to 10 MHz (omega/omega (i) from 0.006 to 1.8) and rf bias voltages from 1 to 200 V. Model predictions were in good agreement with me asurements, much better than that obtained by models that neglect time-depe ndent ion dynamics. In particular, differences of as much as 40-50 % betwee n power measurements and the power predicted by previous models are now exp lained and eliminated. The model also explains why methods of extracting pl asma parameters from electrical measurements using previous sheath models m ay fail, and it suggests more accurate methods of extracting these paramete rs.