Probe Diagnostics in Commercial Plasma Reactors

The commercial plasma reactors are not designed for plasma diagnostics and attempts to implement methods and apparatus proved in the laboratory plasma experiments are in many cases frustrating. There are three major problems in implementing of meaningful probe diagnostics in commercial plasma reactors. They are: a) large frequency spectrum with significant amplitudes of the plasma rf potential corresponding to source and bias fundamental frequencies and their harmonics; b) contamination of the probe surface with a low conductive layer of the reaction products; and c) too high impedance between the plasma and grounded chamber due to the chamber contamination or/and an artificial protective coating. Analysis of these problems and attempts of their resolution are discussed in this presentation. Experimental measurements with different commercial probes, based on electron and ion currents of the probe characteristic, performed in commercial rf plasma processing chambers filled with both noble and molecular processing gases are presented and discussed here. Feasibility of different kinds of probe diagnostics (based on ion and electron saturation currents, as well one based on the second derivative of the probe current) in commercial plasma reactors is discussed and some recommendation are given for meaningful probe diagnostics in such devices.