Axial measurements of electron energy distribution functions (EEDFs) in argon inductively coupled plasmas (ICPs)*

In plasma processing, information of the electron distributions is crucial as ionization and radical production are largely governed by high-energy electrons. In inductively coupled plasmas (ICPs), two mechanisms can affect the electron distribution: inductive coupling and capacitive coupling. In this study, the effect of inductive and capacitive coupling on the electron distribution is explored in a two-chamber ICP with Ar gas. The electron energy distribution functions (EEDFs) are measured with an RF-compensated Langmuir probe which rejects the 13.56MHz signal. Measurements are taken at various axial locations to compare the distributions in the source region, where RF power is deposited, and in the expanding region, where the generated plasmas diffuse into. EEDFs as a function of the axial location are compared with and without Faraday shielding, where the Faraday shield greatly reduces the capacitive coupling.