AVS 46th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoP

Paper PS-MoP13
The Effect of Electrode Gap on CF@sub 2@ Distribution and Electrical Parameters in Fluorocarbon Plasmas

Monday, October 25, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: K.L. Steffens, National Institute of Standards and Technology
Authors: K.L. Steffens, National Institute of Standards and Technology
M.A. Sobolewski, National Institute of Standards and Technology
Correspondent: Click to Email
Fluorocarbon plasmas are widely used by the semiconductor industry for etching and in situ cleaning of PECVD chambers. Previous studies in parallel-plate reactors have indicated that reactive species density distributions, precursor destruction efficiencies, plasma optical emission, and cleaning rates are correlated to the rf current measured at the upper, grounded electrode, I@sub ge@. In these studies, I@sub ge@ varied with changing pressure or was directly controlled by adjusting the impedance between the upper electrode and ground. The electrode gap is an additional parameter which can be varied to optimize the performance of these plasmas. In this study, performed on O@sub 2@/CF@sub 4@ chamber-cleaning plasmas in the capacitively-coupled Gaseous Electronics Conference Reference Cell, we investigated the correlations between electrode gap, electrical parameters, and the spatial distribution of the reactive CF@sub 2@ radical. Electrode gaps ranging from 0.5 cm to 2.25 cm were studied at pressures from 0.1 to 1.0 Torr. The 2-D density distribution of the reactive CF@sub 2@ radical was measured by planar laser-induced fluorescence (PLIF), and the regions where reactive species were generated were determined using spatially-resolved, broadband optical emission. The axial and radial uniformity and intensity of the emission and the CF@sub 2@ PLIF depended on both pressure and gap. The pressure at which the maximum radial uniformity in the CF@sub 2@ PLIF was observed correlated well with the maximum in I@sub ge@ but not with the minimum in plasma impedance. Measurements of rf current at the grounded electrode could be used to optimize the spatial distribution of reactive chemical species in reactors with differing electrode gaps, aiding in the optimization of chamber-cleaning plasmas and other fluorocarbon plasmas.