Surface analysis of the oxidation of organotin films deposited by ArF excimer laser Chemical Vapour Deposition

ArF excimer laser photolysis of gas phase tetramethyltin was used to deposit thin organotin films onSi. In situ Auger electron spectroscopy and x-ray photoelectron spectroscopy ~XPS! film analysis,showed the presence of C and Sn, which, according to C 1s and Sn 3d5/2 peak deconvolution, wereorganized in highly branched polymeric chains likely containing H as well. The film was oxidizedat room temperature by exposure to controlled quantities of O2 up to 5.431012L. Sn 3d5/2, C 1s,and O 1s XPS peaks monitoring allowed us to follow the sequence of the oxidative reactions. Itresulted that oxygen attacks first the Sn-H and Sn-C sites leading to the elimination of H2O and Ccontaining volatile compounds, which determines a rearrangement of the cleaved bonds and anoverall decrease of the measured C content. After this fast phase, oxygen is inserted in the Sn-Snand Sn-C bonds, with formation of Sn-O-Sn, Sn-O-C, and Sn-C-O species. At the highestoxygen doses the dominating SnO2 component shows that almost all available Sn bonds areoxidized to Sn41. However, either core level or valence-band spectroscopy demonstrated that belowthe near-surface layer the tin oxide phase remains substoichiometric, as if the SnO2 at the surfacebehaves as a passivating agent toward further oxidation. © 1997 American Vacuum Society.