Plasma parameters in a twin-chamber RF inductive plasma source, placed in a weak external magnetic field

Abstract

Experimental study of the plasma parameters in an RF inductive plasma source consisting of gas-discharge chamber and process chamber (GDC and PC) located in the magnetic field with inductance less than 70 Gs was carried out. The magnetic field was close to uniform in the PC and divergent in the GDC. The metal or dielectric flange was used as a separating element between GDC and PC. Experiments showed that an increase in the magnetic field at the pressures when the electron mean free path exceeds the longitudinal size of the plasma source and utilization of the operating frequencies of more than 2 MHz led to the formation of radially limited plasma column, which ended at the bottom grounded flange of PC. In this case, the plasma density in the PC became higher than in the GDC. In the area of the metal separation flange, there was a local minimum of the electron density as well as plasma potential, associated with the parasitic capacitive coupling between the antenna and the separating flange. The growth of the magnetic field led to the equalization of the axial potential distribution.At the operating frequency of 2 MHz, at the pressures at which the electron mean free path is less than the longitudinal size of the plasma source, the electron density as well as the space potential reaches a maximum in the GDC and, as a rule, decreases monotonously toward the PC.