AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA9
Insights into the Ion Energy Dependence of Ion-Assisted Chemical Etch Rates in High-Density Plasmas

Monday, November 15, 2004, 4:40 pm, Room 213A

Session: Plasma Surface Interactions in Etching
Presenter: L. Stafford, Universite de Montreal, Canada
Authors: L. Stafford, Universite de Montreal, Canada
J. Margot, Universite de Montreal, Canada
M. Chaker, INRS-Energie, Canada
S.J. Pearton, University of Florida
Correspondent: Click to Email
Over the last few years, important research efforts have been devoted to the development of plasma etching models of various materials in various reactive plasma mixtures. These models generally include a surface kinetic model in which it is usually assumed that the ion-assisted chemical etch rate varies like the square root of the ion energy. This dependence is empirically deduced from the universal energy dependence of physical and ion-assisted chemical etch yields presented by Steinbruchel.@footnote 1@ In the present work, we show from existing experimental data that the ion-assisted chemical etch rate does not necessarily follow this particular energy dependence. A typical example is provided by the etching of ZnO films in an Ar/Cl2 high-density plasma. To explain this behavior, we propose an analytical model in which the formation rate of the adsorbate is assumed to be proportional to the number of adsorption sites. In the specific case of ZnO, the adsorption sites are generated by thermal desorption of oxygen atoms. This is found to induce a non-linear relation between the etch rate and the square root of the ion energy. For oxide materials with more complicated structures like (Pb,Zr)TiO3 (PZT), ion bombardment is required to generate adsorption sites. In this case, the adsorbate formation depends on ion energy, which results in an etch rate that approximately varies like the square root of the ion energy. The predictions of our model are found to be in excellent agreement with the experimental data reported for several materials, for example ZnO, SiO2, HfO2, PZT, PST, and SBT. In addition, the model includes previous ion-assisted etching models such as that developed by Gottscho and his co-workers.@footnote 2@. @FootnoteText@ @footnote 1@ C. Steinbruchel, Appl. Phys. Lett. 55, 1960 (1989)@footnote 2@ R.A. Gottscho, C.W. Jurgensen and D.J. Vitkavage, J. Vac. Sci. Technol. B 10, 2133 (1992) .