Plasma uniformity in high-density inductively coupled plasma tools

A two-dimensional (r, z) fluid model is used to study plasma transport in inductively coupled plasmas (ICPS). Electron heating from external RF coil driven at 2 MHz is calculated self-consistently by solving for the time-averaged RF electric field. Radial plasma uniformity has been studied in both high (R/L=2.5) and low (R/L=1) aspect ratio ICP reactors driven with external planar or cylindrical coils. The effect of neutral gas pressure on plasma uniformity is presented for Ar discharges at 5 and 20 mTorr. The location of external coils and corresponding power deposition profile is predicted to have little effect on uniformity except at higher pressure (>or approximately= 20 mTorr) and for large aspect ratios. Planar coils appear superior to cylindrical coils for achieving relatively consistent uniformity over a wide range of pressures and reactor aspect ratios.