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Electrical Control of the Spatial Uniformity of Reactive Species in Plasmas



Mark A. Sobolewski, Kristen L. Steffens


We report a new method for controlling the spatial distribution of reactive chemical species in a parallel-plate reactor, by means of a variable-impedance load placed between the unpowered electrode and ground. The technique was demonstrated in 89% CF(sub4)/11% O(sub2) and 51% C(sub2)F(sub6)/49% O(sub2) chamber-cleaning plasmas at 13.3-133 Pa (0.1-1.0 Torr) in a Gaseous Electronics Conference reference cell. The rf current and voltage at both electrodes were measured, and plasma spatial characteristics were observed using two-dimensional (2-D) planar laser-induced fluorescence of the CF(sub2) radical and 2-D broadband optical emission measurements. By adjusting the load impedance to cancel the impedance of stray capacitances in parallel with the load, or the sheath capacitance in series with the load, the rf current at the load electrode could be made higher or lower than the current received when the electrode is grounded. When the rf current at the load electrode was minimized, regions of intense optical emission and high CF(sub2) density shifted radially inward, and the distribution of CF(sub2) across the electrode surfaces became more uniform. These results suggest that variable loads could be used to direct reactive species in chamber-cleaning plasmas to the surfaces most in need of cleaning, or to increase the radial uniformity of reactive species in etching plasmas.
Journal of Vacuum Science and Technology A
No. 6


C(sub2)F(sub6), CF(sub)4, chamber cleaning, current, discharge, electrical, plasma, radio frequency


Sobolewski, M. and , K. (1999), Electrical Control of the Spatial Uniformity of Reactive Species in Plasmas, Journal of Vacuum Science and Technology A (Accessed June 23, 2024)


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Created December 1, 1999, Updated February 17, 2017