Modulation of electron energy distributions and discharge parameters in a dual frequency ICP discharge

Abstract

Using a radio frequency (RF) compensated Langmuir probe, modulations in electron energy distribution (EED) and plasma potential are investigated in a discharge produced by a large-area dual frequency/dual antenna inductively coupled plasma source. The discharge is ignited using two frequencies (2 and 13.56 MHz). It is observed that the EEDs can be tailored by varying the power ratio of the two frequencies. Increasing the power level of the low frequency (P2 MHz) enhances the population density of high-energy electrons; however, increasing the high-frequency power (P13.56 MHz) increases the low-energy electron population density. At a fixed total power (P2 MHz + P13.56 MHz), the higher the low-frequency power (P2 MHz) content, the higher the population density of high-energy electrons; however, this trend reverses with high-frequency power (P13.56 MHz). The influence of power ratio on plasma density (ne), plasma temperature (Te) and plasma potential (Vp) has also been studied. It is found out that the plasma parameters have similar trends with RF power irrespective of its frequency. The value of ne increases, and Te and Vp decrease with increasing power. At a fixed P2 MHz, Vp increases with increasing P13.56 MHz. However, Vp decreases with increasing P2 MHz at a fixed value of P13.56 MHz.