AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoM

Paper PS2-MoM10
X-ray Photoelectron Spectroscopy Analyses of SiGe and Si Surfaces after Selective Etching of Si

Monday, November 15, 2004, 11:20 am, Room 213B

Session: Silicon Etching
Presenter: S. Borel, CEA-DRT-LETI, France
Authors: S. Borel, CEA-DRT-LETI, France
O. Renault, CEA-DRT-LETI, France
J. Bilde, CEA-DRT-LETI, France
Correspondent: Click to Email
Recent progress in thin films epitaxial growth enables to consider new applications based on the realisation of Si/SiGe/Si heterostuctures. Indeed, lateral etching process can removed either SiGe or Si sacrificial layer and leads to a cavity between two single crystal-layers. The empty space thus created can be filled by an amorphous material in order to obtain a mono-layer on a insulator (Silicon On Nothing transistors). The selectivity of such processes is crucial for safeguarding of transistors actives parts dimensions. The Si removal etching process is as much more interesting because the selectivity to SiGe is almost infinite. The infinitely selective isotropic etching of Si to SiGe@footnote 1@, obtained by using a combined addition of N@sub 2@ and CH@sub 2@F@sub 2@ into O@sub 2@ +CF@sub 4@ plasma was studied by ex-situ X-ray photoelectron spectroscopy. Etched Si and SiGe surfaces were analysed in terms of elemental composition, bonding states and oxide/oxyfluoride thickness by careful decomposition of Ge3d, Si2p, C1s and F1s core-level spectra. Both F1s and C1s spectra show up a component due to fluorocarbon polymeric groups, the quantity of which is 3 times higher on SiGe than on Si. At the same time on SiGe surfaces, F1s and Ge3d spectra reveal a large formation of Ge(O@sub x@)F@sub y@ bonds compared to metallic Ge, whereas SiF@sub x@ are almost absent. We conclude that a layer formed by a fluorocarbon polymer and Ge oxyfloride induces a total passivation of the SiGe when subjected to the N@sub 2@ /CH@sub 2@F@sub 2@/O@sub 2@+CF@sub 4@ plasma. The precise role of the CH@sub 2@F@sub 2@ will be tentatively interpreted on the basis of other etching results with similar inverted selectivities. @FootnoteText@ @footnote 1@ S. Borel et al., Jpn. J. Appl. Phys. (accepted).