Plasma properties determined with induction loop probes in a planar inductively coupled plasma source

Electromagnetic fields in a planar rf inductively coupled plasma source, of interest for materials processing, were measured using a two-loop inductive (B-dot) probe. The two loops were oriented to measure the time derivative of the axial and radial components of the magnetic field Boverdot(z) and Boverdot(r), respectively, at various positions in the r-z plane of the cylindrically symmetric argon discharge. Maxwell's equations were used with this data to calculate amplitudes of the rf azimuthal electric field E(phi) and current density J(phi), as well as the complex permittivity E of the plasma, from which the electron density n(e) was calculated. The electron densities calculated using this technique were found to compare favorably to the results of measurements made with Langmuir probes. Electron drift velocities calculated from J(phi) and n(e) were found to be comparable to electron thermal velocities in the region of highest E(phi) and thus may contribute to local enhancement of electron impact reactions, thereby affecting process chemistry and uniformity. The peak in the drift velocity moved radially outward as the pressure increased due changes in the radial plasma density profile. This technique is applicable to chemistries where Langmuir probes are not practical. (C) 1996 American Institute of Physics.