Spatial variation of the electron distribution function in a rf inductively coupled plasma: Experimental and theoretical study

The spatial dependence of the electron distribution function (EDF) and of related macroscopic parameters in an inductively coupled argon plasma at 13.56 MHz is studied. The rf induction field is generated using a planar coil. The EDF is determined experimentally with axial and radial resolution via a Langmuir probe technique. The experimental results demonstrate that the EDF can be considered as a spatially homogeneous function of the total energy of electrons. The axial variation of the EDF is described by a one-dimensional, kinetic model, which is based on the nonlocal approach to the solution of the spatially inhomogeneous Boltzmann equation. Good agreement between measured and calculated electron distribution functions is found. Also the axial profiles of the space-charge potential, the electron density, and the mean kinetic energy of the electrons are well reproduced by the theoretical model.