Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Optimisation of operation frequency for high plasma density generation over the whole source area

Generate inductively coupled plasma over large area required large antenna to coupled RF energy to the plasma. The main problem to solve is that long antenna with length comparable to the RF wavelength creates non-uniformity of power dissipation along the coil length (standing wave effect).

This has been verified in our experiments made at 13.56MHz (RF wavelength 22m) with a 2 turn S-shaped antenna (17m) resulting in a non-uniformity of +200 %. The implemented solution consists in the use a set of coils in parallel connected to a 2 MHz generator. With this configuration, the plasma profile is symmetrical showing that the standing wave effect has been removed. Furthermore, the ion current density measurements versus the RF power shows clearly that the plasma density exhibits higher values at 2MHz (x 4) than at 13.56MHz Frequency. It is a direct consequence of a better coupling efficiency improved thanks to the higher pole magnetic permeability and the lower pole magnetic losses at 2MHz vs. 13.56MHz.

The use of 2 MHz frequency with a set of antenna connected in parallel enables high plasma density generation (> 1011 ion. cm-3) over reactor large area.

Reported by

EC Joint Research Center
Via E. Fermi 1
21020 Ispra (VA)
See on map