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Ultra-thin SiO2 on Si: III mapping the layer thickness efficiently by XPS.

Seah, M P; White, R* (2002) Ultra-thin SiO2 on Si: III mapping the layer thickness efficiently by XPS. Surf. Interface Anal., 33. pp. 960-963.

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For many electronic and other purposes, oxides in the range 2-10 nm are grown on silicon. These layers are usually monitored and measured by ellipsometry. Ellipsometry is particularly favoured because it may be integrated into semiconductor production lines, it is fast and, using optical radiation, is relatively benign. Modern ellipsometers can be used to map large wafers in detail with precisions of 0.002 nm (i.e. 0.05%). Unfortunately, it is known if calibrations of ellipsometer, made for thicker films, can be extended down into this region. Also, unfortunately, the method does not distinguish variations in the oxide thickness from variations in the carbonaceous or water contamination overlayers that always will be present in samples exposed to the environment. Ellipsometric anaysis of a 200 nm wafer with 4 nm of oxide shows a ring that may be of oxide or contamination that is 0.2 nm thicker than the central region of the wafer. By mapping with angle-resolved XPS, using a new Thermo VG Scientific Theta 300 instrument, the true aspects of this oxide profile may be verified. Improvements in the data processing of the Theta 300 probe measurements allow similar maps to those of ellipsometry to be obtained with a thickness precision of 0.01 nm (i.e. 0.2%).

Item Type: Article
Keywords: wafer homogeneity
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/2537

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