AVS 46th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS+SS-WeA

Paper PS+SS-WeA1
How Does Ion Bombardment Produce Enhanced Etching?

Wednesday, October 27, 1999, 2:00 pm, Room 612

Session: Ion-Surface Interactions II
Presenter: P.G.M. Sebel, Eindhoven University of Technology, The Netherlands
Authors: P.G.M. Sebel, Eindhoven University of Technology, The Netherlands
L.J.F. Hermans, Eindhoven University of Technology, The Netherlands
H.C.W. Beijerinck, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Etching of Si by XeF@sub 2@ is enhanced considerably by ion bombardment. The role of the reaction layer in this process is studied in a multiple-beam setup at room temperature. One of the main reaction products, SiF@sub 4@, is formed in this layer. During spontaneous etching a thick reaction layer with a chain-like Si@sub x@F@sub y@ structure is formed.@footnote 1@ From ion pulse experiments on a slow time scale (100 s), it is concluded that this reaction layer is depleted of fluorine by the ion bombardment. This thinner reaction layer leads to a lower spontaneous SiF@sub 4@ formation. The depletion of the reaction layer is supported by model calculations. Despite this lower spontaneous contribution, the release of reaction products on a depleted reaction layer under ion bombardment is enhanced by chemical and physical sputtering. However, to produce more reaction products, more reactants (XeF@sub 2@) have to adsorb. This raises the question: "How does ion bombardment cause XeF@sub 2@ to have an increased sticking probability".@footnote2@ From ion pulse measurements on a fast time scale (1 s) it is concluded that on a depleted reaction layer XeF@sub 2@ mainly sticks on dangling bonds with a sticking probability of 0.71. By contrast, on a thick reaction layer the adsorption probability of XeF@sub 2@ is determined by the much lower sticking probability of 0.08 on SiF@sub 2@ surface species. This explains the enhanced sticking probability under ion bombardment and shows that a depleted reaction layer is a prerequisite for enhanced etching under ion bombardment. @FootnoteText@ @footnote 1@ M.J.M. Vugts, M.F.A. Eurlings, L.J.F. Hermans, and H.C.W. Beijerinck, J. Vac. Sci. Technol. A 14, 2780 (1996) @footnote 2@Y. Tu, T.J. Chang, and H.F. Winters, Phys. Rev. B. 23, 823 (1981)