A new diagnostic tool for low-temperature plasmas: the Multipole Resonance Probe
Martin Lapke, Thomas Mussenbrock, Ralf Peter Brinkmann
35th IEEE International Conference on Plasma Science 2008, Karlsruhe, Germany,15-19 June
Summary form only given. Low temperature plasmas are routinely used in materials processing, especially in etching and deposition applications. In this context the electron density is one of the most important parameters in order to characterize the state of the plasma process and the plasma itself. Numerous methods for determining the electron density have been successfully applied. However, only a few are industry compatible which means that i) the results are clearly interpretable, ii) the diagnostic method itself does not lead to contamination of the plasma, iii) the method is robust against perturbation (e.g., due to deposition), and iv) of course the cost of maintenance and the diagnostics itself is low. The so-called resonance spectroscopy methods which employ the ability of a plasma to resonate at or near the electron plasma frequency fulfill these requirements to a great extend. This contribution discusses a particular realization of that general concept. Based on new insights of recent simulations, we developed a new diagnostic concept, termed multipole resonance probe. A spherical design enables to gain an analytical evaluation formula to determine the electron density from a measured absorption spectra.