Resonance Frequencies of Curling Probe in Plasma: Surface Wave Analysis
Ali Arshadi, Ralf Peter Brinkmann
67th Annual Gaseous Electronics Conference, 3- 7 November, 2014, Raleigh, North Carolina.
Electron density is a crucial characteristic in reactive plasma sources determining the quality of material processing like etching and deposition. It is vital to monitor electron density giving us the ability to control different chemical and physical reactions in plasma reactor.
A recently invented plasma diagnostic probe called curling probe resonates in distinctive frequencies when it is embedded in the wall of the plasma reactor. The excited frequencies of probe are studied for various electron densities. It has been demonstrated that the high-frequency (HF) volume wave resonances and the low-frequency (LF) surface wave resonances are predictable considering the wave propagation in plasma when it is diffracted on the curling probe. We consider the three dimensional diffraction of incident plane wave by a slot in an infinitely thin perfectly conducting screen located between dielectric and sheath.
Our computations for LF resonances were published recently. The results are in a very good agreement with the FDTD analysis. In this paper it is demonstrating that the LF resonances are based on the surface wave propagation. We compare our result with one comes from surface wave analysis and we prove that the LF resonances are not dependent on the length of curling probe. The other theoretical and computational methods do not take into account the existence of the sheath and the collisions between electrons and atoms in plasma. We have generalized our study in order to be able to investigate the effect of the sheath thickness and electron- neutral collision frequency.