A NEW DIAGNOSTIC TOOL FOR LOW

TEMPERATURE PLASMAS -

THE MULTIPOLE RESONANCE PROBE ∗

Martin Lapke, Thomas Mussenbrock, and Ralf Peter Brinkmann

Institute for Theoretical Electrical Engineering,

Center for Plasma Science and Technology,

Ruhr-University Bochum, D-44780 Bochum, Germany

Low temperature plasmas are routinely used in materials pro-

cessing, especially in etching and deposition applications. In

this context the electron density is one of the most important pa-

rameters 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 gen-

eral concept. Based on new insights of recent simulations1, we

developed a new diagnostic concept, termed multipole reso-

nance probe. A spherical design enables to gain an analytical

evaluation formula to determine the electron density from a mea-

sured absorption spectra.

1. M.Lapke, T.Mussenbrock, R.P. Brinkmann, C. Scharwitz,

M.Boke, J. Winter, “Modeling and simulation of the plasma ab-

sorption probe”, Appl. Phys. Lett. 90, 121502 (2007)

∗The authors acknowledge the support by the Deutsche Forschungsgemein-

schaft (DFG) via the Graduiertenkolleg GK 1051 and the Ruhr University Re-

search School.