On the E to H transition in a dual frequency inductively coupled plasma

E-H transition powers with various gas pressures are investigated in a dual frequency inductively coupled plasma. Driving frequencies of 2 MHz and 13.56 MHz are applied to antennas, respectively. At low pressures ($\nu $/$\omega $\textless 1), the E-H transition power decreases with the pressure, and at high pressures ($\nu $/$\omega $\textgreater 1), the transition power increases with the pressure. Therefore, the transition power has a minimum near $\nu $/$\omega $\textasciitilde 1. In experiments, the E-H transition power of 2 MHz is lower than that of 13.56 MHz at low pressures (\textless 10 mTorr). At high pressures (\textgreater 50 mTorr), the transition power of 13.56 MHz is lower than that of 2 MHz. However, at the dual frequency operation, the transition occurs between the transition power of 2 MHz and 13.56 MHz. These transition powers of the dual frequency are consistent with those from a power balance model including plasma absorbed power and plasma loss power. In the dual frequency ICP, the E-H transition is more independent of the pressure than a single frequency ICP.