Plasma diagnostics in rf discharges using nonlinear and resonance effects

In modelling rf discharges, nonlinear phenomena usually are treated as inconvenient effects. A method based on a nonlinear phenomenon is the self excited electron plasma resonance spectroscopy (SEERS). This new method for plasma monitoring allows to determine density and collision rate of the electrons and the power dissipated in the plasma body. Microwave interferometry (MWI) and Langmuir probe (LP) measurements were used to verify this method. This is shown for inert (He, Ar) and electronegative gases (O-2, CF4). Examples of in situ control in plasma etching process are described. The high sensitivity and the capability of endpoint detection are shown.