Influence of external parameters on RF inductive discharge plasma characteristics

Abstract

Systematic experimental studies of the electron density and temperature, the efficiency of RF power coupling to the RF inductive discharge plasma have been carried out in the pressure range of helium, neon, argon, and krypton 0.1–133 Pa, at an RF generator power of 100–500 W and frequencies of 2, 4 and 13.56 MHz. It is shown that the electron density reaches a maximum, and the temperature reaches a minimum in the pressure range 1.33–13.3 Pa. Taking into account the presence of a parasitic capacitive coupling between the inductor and the plasma, which forms the capacitive channel of RF power input, makes it possible to conclude that the maximum values of the electron density were observed at the pressure at which the power input through the inductive channel is maximal. At pressures of the order of 0.133 Pa and below, an increase in the electron temperature is observed in the peripheral part of the discharge. Numerical modeling by the PIC method shows that one of the reasons is the formation of a directed azimuthal motion of electrons in the region of the skin layer. As the pressure increases, a transition occurs from the nonlocal to the local electron kinetics, which is reflected in the ratio between the electron temperature in the peripheral and central parts of the discharge.