IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Tuesday Sessions
       Session PS1-TuA

Paper PS1-TuA9
Modeling of SiO@sub 2@ Feature Etching in Fluorocarbon Plasmas: The Effect of Gas Phase Composition on Aspect Ratio Dependent Phenomena

Tuesday, October 30, 2001, 4:40 pm, Room 103

Session: Dielectric Etch I
Presenter: E. Gogolides, National Center for Scientific Research (NCSR) "Demokritos", Greece
Authors: G. Kokkoris, National Center for Scientific Research (NCSR) "Demokritos", Greece
E. Gogolides, National Center for Scientific Research (NCSR) "Demokritos", Greece
A.G. Boudouvis, National Technical University of Athens (NTUA), Greece
Correspondent: Click to Email
There are several problems during etching of SiO@sub 2@ features in fluorocarbon plasmas such as Reactive Ion Etching lag (RIE lag), inverse RIE lag,@footnote 1@ and etch stop,@footnote 2@ which have been observed to depend on Aspect Ratio (AR) of the etched feature@footnote 3@ and are included in the general term Aspect Ratio Dependent Etching (ARDE). A goal to achieve in feature etching is Aspect Ratio Independent Etching (ARIE). The context of this work involves modeling of the effect of gas phase composition on AR dependent phenomena during SiO@sub 2@ feature etching in fluorocarbon plasmas. The effort to accomplish this task requires: a) A predictive surface model@footnote 4@ for open area SiO@sub 2@ etching; the surface "coverage", @theta@, is assigned to all species (fluorine atoms, fluorocarbon radicals, and a surface polymer) in the mixed layer created under ion bombardment. The "polymer surface coverage", @theta@@sub P@, could be thought of in a more general sense as a normalized thickness of the polymer overlayer. The model coefficients have been calculated@footnote 4@ by fits to beam experiments' results. b) A model to calculate the local values of neutral and ion fluxes (flux calculator@footnote 5@) inside etched features, which takes into account shadowing of neutral and ion flux and re-emission of neutral flux. Charging effects are not explicitly considered at present. c) A coupling of model (a) with (b) to calculate the local etching rate inside features. The focal point of the coupling is the simultaneous@footnote 5@ calculation of local fluxes and effective sticking coefficients of the neutral species at each elementary surface of the structure being etched. The goal of this work is the prediction of several phenomena (RIE lag, inverse RIE lag, etch stop, and ARIE) and their relation with gas phase composition. A new approach is presented based on maps of two types. The maps of the first type show the effect of gas phase composition on etching yield at the bottom of an etched feature. In the second type of maps the effect of gas phase composition on ARDE and ARIE is illustrated. Gas phase composition is divided into regions characterized by the observation of a specific phenomenon in each region (e.g. RIE lag, inverse RIE lag, ARIE). Furthermore, a preliminary investigation of processes windows satisfying specific demands on ARIE, etching rate magnitude, and etching rate (SiO@sub 2@/Si) selectivity is done. @FootnoteText@ @footnote 1@ M. F. Doemling, N. R. Rueger, and G. S. Oehrlein, Appl. Phys. Lett. 68, 10 (1996). @footnote 2@ O. Joubert, G. S. Oehrlein, and Y. Zhang, J. Vac. Sci. Technol. A 12, 658 (1994). @footnote 3@ R. A. Gottscho, C. W. Jurgensen, and D. J. Vitkavage, J. Vac. Sci. Technol. B 10, 2133 (1992). @footnote 4@ E. Gogolides, P. Vauvert, G. Kokkoris, G. Turban, and A. G. Boudouvis, J. Appl. Phys. 88, 5570 (2000). @footnote 5@ G. Kokkoris, E. Gogolides, A. G. Boudouvis, Etching of SiO@sub 2@ and Si features in fluorocarbon plasmas I: Effect of gas phase composition on aspect ratio dependent phenomena in trenches, submitted for publication to Journal of Applied Physics.