A novel electro-optical probe to diagnose plasma uniformity

Abstract

A novel electro-optical probe ͑EOP͒ 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.

Spatial profiles of neutral, ion, and etch uniformity in a large-area high-density plasma reactor

“…The spatial profile of atomic oxygen density may not be uniform because atomic oxygen is a dissociated species by plasmas but the spatial profile of the actinometer may be uniform. 10 Thus, N O (x) can be estimated by measuring I a (x) and I O (x) at each position, assuming a spatially uniform actinomer. In the case of our experiment, the radial profile of O with a blank photoresist wafer was similar to the radial profile of O with a blank Si wafer.…”

“…5,6,9,10 It can be obtained by adding a small amount of an inert gas called the actinomer, by selecting emission lines that meet certain criteria and by the following equation:…”

Two-dimensional calculation of spatial distribution of neutral atoms for a planar inductively coupled oxygen discharge

“…At a lower pressure, the oxygen atom density is nearly homogeneous due to the greater diffusion length [12]. The calculated profile of oxygen atoms compares well with the relative radial distribution of the F density which was obtained by optical emission actinometry in SF 6 discharges [13] and CF 4 discharges [14]. The variation of the magnitude of the spatially averaged density of oxygen atoms with operating pressure was predicted by global modeling [15].…”

An optical probe for local ion temperature measurements in a plasma

“…However, neither a critical analysis of its performance was given nor ion temperature measurements are presented in Ref. [7], [8]. We will point out in chapter 3 some of the differences between their and our design.…”