Electron-density and energy distributions in a planar inductively coupled discharge

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Abstract
Electron‐density and electron energy distribution functions (EEDFs) are measured in a 20‐cm‐diam by 14‐cm‐long cylindrical, inductively coupled plasma source driven by fields from a planar, spiral coil at 13.6 MHz. Radio‐frequency (rf) ‐filtered Langmuir probes are used to obtain spatial profiles of electron population characteristics in argon at powers and pressures of interest for etching and plasma‐assisted deposition (1–100 mT). Electron densities range from 1010 to 1012 cm3 with 100–500 W of rf power and peak on axis in the center of the cylindrical volume. The EEDFs show that the observed average electron energy varies by 1–2 eV spatially, with the highest values of average energy occurring at those regions of strongest rf electric field. The EEDF measurements also reveal a significant population of cold electrons trapped in a potential well at the location of peak electron density. From these spatial measurements, spatial estimates of conductivity and ionization rate are deduced.

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