Effect of dual frequency rf power in an inductively coupled plasma

Dual frequency inductively coupled plasma discharge is investigated. Dual RF power is applied independently to each antenna (inner and outer coil), and the electron energy distribution functions (EEDFs) are measured using a RF compensated Langmuir probe. As the ratio of low frequency power (P$_{\mathrm{low}})$ and high frequency power (P$_{\mathrm{high}})$ is changed, the variation of EEDF is observed. When P$_{\mathrm{low}}$ is higher than P$_{\mathrm{high}}$, the low energy electrons effectively heated compared to the case when P$_{\mathrm{low}}$ is comparable to P$_{\mathrm{high}}$. This difference in the shape of the EEDF can be understood by correlation between the driving frequency and the collision frequency.