Frequency dependencies of the characteristics of an inductively coupled radiofrequency discharge at reduced pressure

Abstract

The dependence of parameters of an inductively coupled radiofrequency plasma on the electromagnetic field frequency in range 0.25–40 MHz at reduced pressure (113 Pa) was studied. The study was carried out in a 2D axisymmetric time-dependent setting, implemented in the Comsol multiphysics software package using the Navier–Stokes equations, continuity equation for electron density, electron energy density equation, ion density equation, metastable atom density equation, heat transfer equation, Maxwell and Poisson equations for electromagnetic fields. The distributions of the plasma parameters at the output of the discharge tube in dependence on electromagnetic field frequency were obtained. It was found that the dependences of the electron density, electron temperature, and gas temperature on the field frequency are non-linear. The maximum value of these quantities were achieved at different frequencies depending on the discharge power. A mechanism relating the frequency and power to the shift in the positions of the maxima of these plasma parameters is proposed.