AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThA

Paper PS-ThA10
Electrical Control of Spatial Uniformity of Chamber-Cleaning Plasmas Investigated using Planar Laser-Induced Fluorescence

Thursday, November 5, 1998, 5:00 pm, Room 318/319/320

Session: Diagnostics II
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 in situ cleaning of PECVD chambers. Control and optimization of chamber-cleaning processes are critical for reduction of both the emission of greenhouse gases and chamber-cleaning time. Also the spatial distribution of chemically reactive species in the plasma should be tailored to maximize the cleaning rate at appropriate surfaces. Previous studies in parallel-plate reactors have indicated that reactive species density distributions, plasma emission, and cleaning rates are correlated to the rf current measured at the upper, grounded electrode. In this study, the current at the upper electrode was varied by adjusting the impedance between the upper electrode and ground, and the resulting changes in plasma uniformity were investigated using optical techniques. Measurements were made in O@sub 2@/CF@sub 4@ and O@sub 2@/C@sub 2@F@sub 6@ plasmas in the capacitively-coupled Gaseous Electronics Conference Reference Cell at pressures from 0.1 to 1 Torr. The 2-dimensional density distribution of the reactive radical, CF@sub 2@, was measured using planar laser-induced fluorescence (PLIF), and the regions where reactive species were generated were determined using spatially-resolved, broadband optical emission. As the current at the upper electrode was varied, changes were observed in the axial symmetry of the broadband emission and in the radial uniformity of the CF@sub 2@ PLIF. These results suggest that electrical control of the current paths through the plasma could be used to control the spatial distribution of reactive chemical species, aiding in the optimization of chamber-cleaning plasmas and other fluorocarbon plasmas.