IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Thursday Sessions
       Session PS-ThP

Paper PS-ThP25
The Geometric and Chemical Effect of Polymer Deposition and Etch-product Redeposition on the Etching of SiO@sub 2@ Trench Sidewall in a CF@sub 4@ Plasma

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Plasma Etching Poster Session
Presenter: J.H. Min, Seoul National University, Korea
Authors: J.H. Min, Seoul National University, Korea
S.W. Hwang, Seoul National University, Korea
G.R. Lee, Seoul National University, Korea
S.H. Moon, Seoul National University, Korea
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The effect of etch-product redeposition on the etching of SiO@sub 2@ trench sidewall in a CF@sub 4@ plasma was studied using a Faraday cage with a slit on the upper plane located in a transformer coupled plasma reactor. The Faraday cage with a slit allowed ions to be injected vertically on the specified portion of SiO@sub 2@ bottom surface under the practical plasma condition. The effect of the bottom surface on the redeposition of the etch products on the sidewall was studied by comparing the properties of the sidewall surfaces obtained with or without the etch-product emission from the bottom surface. The trench bottom was etched at the bias voltage ranging between -200 and -600V and at the source power between 200 and 600W. The bias voltage and the source power had complex influences on the redeposition of the etch products on the sidewall because they changed the concentration of radicals, and the flux and the energy of ions injected on the bottom surface. Specifically, the bias voltage increased the redeposition rate mostly by physical sputtering, while the source power increased the rate mostly by chemical sputtering. The concentration of CF@sub 2@ and F radicals increased with the bias voltage and the source power, which enhanced the polymer deposition on the sidewall. The shape of the Si-O peak in the Infrared(IR) spectrum of the redeposition film was similar to that of thermal oxide, but the Auger Emission Spectroscopy(AES) indicated that the O/Si ratio was higher for the redepsition film than for the thermal oxide. Analyses of the sidewall surface by AES and IR indicated that F radicals reacted with the oxide layer to break the Si-O bond. In the case of oxygen addition, the etch rate of the bottom surface increased but the rates of redeposition and polymer deposition on the sidewall decreased due to the enhanced production of F radicals in the plasma.