A novel electro-optical probe to diagnose plasma uniformity

A novel electro-optical probe (EOP) has been developed to characterize the spatial uniformity of various plasma parameters. Spatially resolved electron density and energy distribution function, neutral and charged particle densities, as well as ion flow velocity are determined by the EOP. The design of the EOP combines a Mach probe, back-to-back charge collectors, and a collimated optical fiber. The light collection angle of the optical fiber is limited by recessing the fiber in a ceramic tube. The line-of-sight integration length of the plasma emission is bounded by the charge collector disk. A spatial resolution of 2.4 cm is obtained by the present design of the EOP. The ion flow velocity perpendicular to the charge collector surface is determined by the ratio of the ion saturation currents of the two counter facing charge collectors. Localized actinometry, that combines spatially resolved optical emission spectra and electron energy distribution functions, is used to determine the density of atomic chlorine and fluorine radicals. The spatial distribution is obtained by scanning the EOP across the plasma volume. (C) 1998 American Institute of Physics. [S0034-6748(98)03609-0]