AVS 47th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThA

Paper PS2-ThA4
Reaction Mechanisms and SiO@sub 2@ Profile Evolution in Fluorocarbon Plasmas: Bowing and Tapering@footnote 1@

Thursday, October 5, 2000, 3:00 pm, Room 311

Session: Dielectrics I
Presenter: D. Zhang, University of Illinois at Urbana-Champaign
Authors: D. Zhang, University of Illinois at Urbana-Champaign
C. Cui, Applied Materials, Inc.
M.J. Kushner, University of Illinois at Urbana-Champaign
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The rate and quality of fluorocarbon plasma etching of dielectrics is largely determined by a balance between deposition of polymer and ion activated chemical or physical sputtering. The proper balance results in selectivity and sidewall passivation producing straight walled features. The scaling of SiO@sub 2@ etching in fluorocarbon plasmas was numerically investigated using the Hybrid Plasma Equipment Model and the Monte Carlo Feature Profile Model (MCFPM). Algorithms were added to Surface Kinetics Module to account for multiple polymer layers, delivery of activation energy through polymer layers and ion activated polymer deposition. The MCFPM was also improved by including these processes. Reaction mechanisms were developed in which deposition of C@sub n@F@sub m@ radicals, either direct or ion activated, produces a polymer layer. At the interface of the polymer layer and SiO@sub 2@, a C@sub n@F@sub m@-SiO@sub 2@ complex is formed which, in the presence of fluorination by F atoms diffusing and ion energy delivery through polymer layers, produces etching in a 2 step process. Selectivity to Si results from lack of consumption of the polymer layer. SiO@sub 2@ etch rates increase with increasing bias at low biases due to increased activation energy delivered through a thinner passivation layer. Etch rates saturate at high biases due to polymer starvation. Comparisons to experiments showed that etch profiles transitioned from bowed to tapered as the passivation flux to ion flux ratio increased. This transition is delayed to higher passivation flux to ion flux ratios by increasing the bias. In general, loss of critical dimension correlated with a reduction in etch rate due to the thickening of passivation layers. For this reason, saturation of the etch rate due to polymer starvation also improved maintenance of the critical dimension. @FootnoteText@ @footnote 1@Work supported by AMAT, LAM, SRC and NSF.