AVS 49th International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoA

Paper AS-MoA6
Ultra Thin SiO@sub 2@ on Si: Quantification of the Oxide Thickness and Carbonaceous Contamination

Monday, November 4, 2002, 3:40 pm, Room C-106

Session: Quantification & Accuracy in Surface Analysis
Presenter: M.P. Seah, National Physical Laboratory, UK
Authors: M.P. Seah, National Physical Laboratory, UK
S.J. Spencer, National Physical Laboratory, UK
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An analysis is made of the quantification issues in the measurement of ultra-thin layers of SiO@sub 2@ and of carbonaceous contamination on (100) and (111) polished Si surfaces. For the analysis of the oxide thickness, a simple equation is generally used involving two parameters; the attenuation length of photoelectrons in the oxide, L, and the ratio, R@sub o@, of the intensities of the Si 2p peak from bulk thermal SiO@sub 2@ and from pure Si. An analysis of previously reported measurements of L gives an average value of only 6% less than the theoretical value. However, careful measurements of R@sub o@, via two routes, indicate consistently that a value of 0.88 ± 0.05 should be used rather than the calculated value of 0.53 ± 0.05. This difference may arise through systematic errors in the values for the relevant inelastic mean free paths, the silicon dioxide density and the shake-up intensity contributions. Previously reported experimental values of R@sub o@ range from 0.67 to 0.87. Sources of uncertainty in these parameters and in the thickness will be addressed. Measurements of a basis set of materials for an international study, started in March 2002 under the auspices of the Consultative Committee for Amount of Substance (CCQM), show average correlations with ellipsometry better than 0.13 nm over the thickness range 2 nm to 8 nm. Measurements of the carbonaceous contamination show how to clean and store the samples effectively and the relevant parameters for a consistent carbon quantification.