Plasma Analysis with Plasma Probes and Retarding Field Analysers

Principle of Plasma Analysis with plasma probes and Retarding Field Analysers

Plasma probes are one of the oldest measuring techniques for gas discharges and have a history of more than 100 years. They can be used as Langmuir probes, measuring plasma properties like electron density and electron energy at the plasma itself, or as plasma sheet probes arranged at the plasma walls (or substrate position) to characterize the plasma from the plasma sheet, which influences thin film deposition processes significantly.

Retarding Field Analysers  (RFA)  are used for plasma- and ion beam analysis since 50 years. They consist of an ion optical systems with several isolated grids to extract from a plasma positive ions or negative ions/electrons and to measure their energy distribution by a retarding field.

Principle of  plasma analysis by Langmuir probes, plasma sheet probes and Retarding Field Analysers

The device "PlasmaMon" from Jenion works with all three kinds of plasma probes. All probes have to be installed at the vacuum chamber, mostly  at customer specified positions. At the electrical vacuum feedtroughs filter circuits for suppressing Radio Frequency are installed. So with this probes plasma analysis can be carried out at plasma excitation frequencies ranging from DC up to 2.45 GHz (microwave plasma).

All probes analyse the plasma in respect to ground. Because the measuring principle is based on DC-currents, the probes only work at plasmas without deposition of isolating layers (e.g. like oxide- or nitride deposition by sputtering or PE CVD).

Of course also broad ion beams can be analysed with plasma sheet probes and Retard