Diagnostics of Inductively Coupled Plasma Under the Influence of Immersed RF Self-Biased Substrate Electrode

Diagnostics of the inductively coupled plasma (ICP) generated using a flat spiral antenna are performed using radio frequency (RF) compensated Langmuir probe (CLP). The measurements on the generated plasma are made under the varying influence of the RF self-biased substrate electrode immersed in the plasma. From the V - I characteristics of the Langmuir probe taken at different radial locations in the plasma volume at a fixed axial distance of 5 cm from the quartz isolation window, electron energy probability functions (EEPFs) at various locations are obtained. It is observed that there is a strong correlation between the plasma parameters and EEPF with the bias on the substrate electrode. At a constant RF power in antenna coils, the EEPF evolved from bi-Maxwellian to Maxwellian with an increase in the bias level on the substrate electrode. The evolution of the EEPF with a variation of operating pressure is explained in terms of different heating mechanisms in plasma. Furthermore, EEPF evolution in the plasma from Maxwellian to bi-Maxwellian under the varying influence of RF power fed to the antenna coils keeping RF self-bias level on the substrate electrode constant is also explained.